# Autocross EV special



## galderdi (Nov 17, 2015)

Here are a couple more, earlier photos


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## bigmouse (Sep 28, 2008)

In order to measure voltage (or current) between the chassis and the HV battery, you have to have some sort of connection between them. High-value resistor chains approximate isolation for safety purposes. Something in the range of 5 mega-ohm would be acceptable to most regulatory bodies. Measuring the voltage across one of those resistors will tell you how much current is flowing. You need to have two of these setups in case the loss of isolation happens on the same node as the resistor (no current will flow).

There are products you can buy that do this.

If you REALLY need to have complete isolation, then you'll have to get fancy with a capacitor and AC excitation to detect losses of isolation.

As for opening the contactors, you'll have to integrate something with the isolation detector to drive the contactors either directly or through a relay.


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## galderdi (Nov 17, 2015)

Someone outside the forums made a suggestion to split the battery packs to reduce the voltage. I am thinking about taking that principle one step further. I think if I run the -ve from the -ve of the last battery in the chain to the -ve of my dual pole circuit breaker. Then run the other side of the circuit breaker to the chassis. The most it would ever see is 12v if the insulation failed but it would still be enough to trip the circuit breaker well before anyone ever comes in contact with it. I will do a test tonight to prove my theory. The two outcomes I will be looking for are (1) does the circuit breaker trip when connected to the -ve of the last battery? (I think this is fairly certain). (2) With 2 batteries as the test do I see 12v or 24v across the circuit breaker (again I am fairly certain it will be 12v).

I will do a circuit diagram to demonstrate the concept.


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## dougingraham (Jul 26, 2011)

Isolation detection is tricky to do right. Your most likely source of loss of isolation is an instrument that you thought was isolated followed by something like a buildup of brush dust in the motor. This can cause a bridge from the brush holders to the motor case. And in DC motor controllers usually the positive rail is connected through to one brush all the time.

As soon as you are hooked on the electric version of this switch to Lithiums. 1/4 the weight for the same stated capacity although in practice it can be as much at twice this.

Good luck on your racing. It looks like it will be a lot of fun.


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## arklan (Dec 10, 2012)

could u use a comparator for this?

and also as doug said,
my car has a 4Mohm connection from the negative to the chassis through the motor, if u get a bit of wire from the positive and scrape it along the car, it will get little sparks as if it were from a 9v battery, also makes me feel warm and fuzzy if i bump anything while playing around in the battery section.


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## galderdi (Nov 17, 2015)

Thanks for the ideas. The resisitor idea is a good one.

I did a test this morning. 
The circuit breaker will trip if it sees any positive voltage on the chassis but the maximum it will see is 12v.


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## galderdi (Nov 17, 2015)

Hmmm actually rethinking my idea....it isn't any good. Yes it will trip the circuit breaker and yes it will only see the 12v under normal circumstances. But I didn't consider that connecting the -ve from the last cell is also connecting the +ve from the remaining 11 cells. This would mean if for some reason I came into contact with the chassis and the Traction pack earth I would have 132V running through me (exactly what I am trying to avoid). 

However I am thinking I could solve that complication using a big diode to prevent positive voltage passing back through the circuit breaker. I will perform another test this weekend.

What advantage is gained by earthing the Chassis?


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## arklan (Dec 10, 2012)

semiconductor fuses are big fat diodes so u can do 2 things in one 

earthing the chassis means that u dont need to run so many wires for your 12v system, thats it.

if u r talking about earthing your traction pack, yeah, dont do that


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## galderdi (Nov 17, 2015)

arklan said:


> semiconductor fuses are big fat diodes so u can do 2 things in one
> 
> earthing the chassis means that u dont need to run so many wires for your 12v system, thats it.
> 
> if u r talking about earthing your traction pack, yeah, dont do that


Agreed, Earthing the chassis is what I am trying to avoid.

But I want some protection incase the insulation ever fails. 
So my current thinking is to run the -ve from the last cell through a diode (or multiple to handle about 15amps) through to a 10amp circuit breaker then to the chassis. Then if the insulation ever fails and puts +ve voltage to the chassis (anything more than 10amp) it will trip the circuit breaker and disconnect all the power circuits.

Effectively I will be earthing the chassis from the traction pack but only from the last cell. Not the full 12 cells. I will attach a diagram shortly.


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## galderdi (Nov 17, 2015)

Here are some diagrams of my current thinking


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## galderdi (Nov 17, 2015)

And here is the latest photo of the car


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## arklan (Dec 10, 2012)

diodes dont work in paralel, theyll choose a representative to do all the work while the others supervise.


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## galderdi (Nov 17, 2015)

On Friday I weighed the car. It is currently 475KG. I still have a few things to add so I expect that to grow to about 530kg but thats still a lot less than the 600kg I was predicting.


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## EVsonic (Aug 14, 2014)

Is there a body and windshield? 

Also how long are your runs and how many amps will you draw?

Looks like a weapon

Cheers Kiwi


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## Duncan (Dec 8, 2008)

Looks like a fun car

Shame you are on the wrong side of the ditch - I would love to try "The Device" against you and EVSonic

http://www.diyelectriccar.com/forum...-dubious-device-44370p8.html?highlight=duncan

I suspect I am older than the two of you put together so you would win - but it would be fun


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## EVsonic (Aug 14, 2014)

Duncan said:


> Looks like a fun car
> 
> Shame you are on the wrong side of the ditch - I would love to try "The Device" against you and EVSonic
> 
> ...


Hey Duncan I'm coming home to the long white cloud in the end of January will be doing the campervan thing around Queenstown would love to catch up.
Cheers Kiwi


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## galderdi (Nov 17, 2015)

EVsonic said:


> Is there a body and windshield?
> 
> Also how long are your runs and how many amps will you draw?
> 
> ...



The body will be a continuation of the right side you can see in that latest photo. It will continue around the back and sides at that same height. It is 0.4mm polycarbonate and weighs next to nothing.

There will not be any windscreen. We run on bitumen and are required to wear a helmet with visor. 

The runs are anything from 20 seconds to 90 seconds. Theoretically it could draw 400amps but in reality I don't think it will need anything like that. I really won't know until the first drive. My best guess is peaks of 300amps for a couple of seconds here and there.

In between each run there are gaps of 5-10 minutes where the car will remain idle, giving everything a chance to cool (including the driver  ) The hardest part will be looking for shade between runs to assist the cooling.

I don't think it will be the most competitive in outright speed as it is a bit bigger and heavier than some of the petrol driven competitors. Most of those are single seaters. But I am aiming to compensate using the torque and reliability. I'll let you know if it worked at the end of 2016.


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## galderdi (Nov 17, 2015)

Duncan said:


> Looks like a fun car
> 
> Shame you are on the wrong side of the ditch - I would love to try "The Device" against you and EVSonic
> 
> ...


 Swing on over with or without the car. I'd be happy to let you drive the BATTmobile in a Motorkhana. The dates for suitable events are Sept 4th, or Nov 27th.
That is one of the reasons I made it a two seater I get almost as much enjoyment letting other people thrash it.

I just hope the performance is up to scratch.


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## galderdi (Nov 17, 2015)

Here is a challenge for you all.

I have plugged all the figures into a performance simulator found on this forum. So I have a hypothetical idea how it will perform. But I was wondering what other people might predict. So please post your 0-35MPH prediction here by Feb 6th. I will be competing on Feb 7th so I will have the results and video evidence. I have chosen 35mph as the target because the event is a motorkhana and 60mph may not be practical at this course.

The vehicles specifics are:



total weight without driver 1168 pounds
total weight with driver 1433 pounds
it is frount wheel drive with a viscous LSD
tyres (tires) are treaded track tyres 205/15/16
I generally run the tyres at 25 PSI cold
The event is in Feb and this test is likely to occur around 9am so I expect the ambiant temp to be about 84*°F* (29*°C)*
The voltage is 149V before I start
The current is unknown at this time but the controller and motor can handle 400 amps
The batteries can discharge at 410amps for up to 20 seconds (Assuming *77°F (25°C))*
The gearing is as follows - 1=3.063 2=1.826 3=1.286 4=0.975 5=0.83 Final drive=4.167


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## Duncan (Dec 8, 2008)

EVsonic said:


> Hey Duncan I'm coming home to the long white cloud in the end of January will be doing the campervan thing around Queenstown would love to catch up.
> Cheers Kiwi


Hi Kiwi
I'm in Gore - about two hours from Queenstown 
So you are very welcome to drop in for a coffee and a feed,
Not sure what state the Device will be in - It's sitting under a tarp until I get my new shed built

Cheers
Duncan


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## galderdi (Nov 17, 2015)

Last night was a pivotal point in my project. I had a couple of tests on the weekend which failed. I quickly identified the issue and targeted last night for remediation and a repeat test.
Failure would have put my timeline in jeopardy as I would only have a few weeks to secure and implement any replacement parts (these motors and controllers are not common).
Success would mean I am back on track for the first event on Feb 7th.

The test was successful. I ran the motor on stands without the gears engaged. Then I ran the motor on stands with gears engaged. Then I went for a few test drives.
I still have a few challenges to overcome. Like the accelerator safety not working as expected. Apart from the obvious increased risk it also means when I operate at 30% or greater the motor doesn’t stop spinning when my foot is off the accelerator (Not a show stopper). It also means the motor controller puts out a “Low duty cycle” alarm constantly until I push the accelerator a fair way down.
My Power dial worked absolutely perfectly. On 10% I barely crawl even with the accelerator fully depressed. On 30% it moves the car at what I would describe as adequate speed/acceleration. On 50% it was quite good. I wasn’t game to try it on anything more than 50% because I need to upgrade one of the power cables and I only have the handbrake for the moment. 
I need to raise the car as it scraped quite a few times. 

This first video is the test on stands:
https://www.youtube.com/watch?v=JfGaBPGaSgg&feature=em-upload_owner

This video is the first test drive. Sorry about the quality but the BattMobile was in Stealth mode. Plus I had the Neighbour’s kid doing the videoing. But you can get a bit of a sense of the performance on the 50% setting. 
https://www.youtube.com/watch?v=zDTj-N4-6ek&feature=em-upload_owner

I hope to have a daylight test video next week but there won’t be any advancement for another couple of weeks.


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## galderdi (Nov 17, 2015)

Here are some better videos:
https://www.youtube.com/watch?v=CI3KsInT1R8
https://www.youtube.com/watch?v=SOB0wmiybRw

These test runs are a bit slow because they are on wet grass. I only had my power setting on 5 out of 10. So I get the sense it will have enough power. (Not to mention I only had a handbrake)

I am still on track for the first 2016 motorkhana for Feb 7th.

All I need to do is:
• Swapping the rear hubs and upgrading the rear springs to handle the weight
• Brakes all round
• Panels and dash
• Belts
• Another set of batteries
• And a handful of other minor items

I estimate another 4 days effort and then some tweaks / adjustments


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## galderdi (Nov 17, 2015)

Here are the latest photos. It is almost complete.

I just need some fiishing touches and extra sets of batteries. 
It is ready with plenty of time for the first event on Feb 7th

Here is the video of the latest test in my driveway:
https://www.youtube.com/watch?v=1DJ2EE6qcXY


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## dcb (Dec 5, 2009)

wow, you really cranked this project out, very nice.

What are you using for the camera overlay? And am I reading the spot right (pulling about 1/2 g?), and are you still at %50 here?

Also, looks like the shifter needs adjustment, but way to git 'er done!


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## galderdi (Nov 17, 2015)

Thanks, Yes I am very happy with the progress. It helps to have an unmovable deadline. 

There are certainly going to be some bugs to iron out but I am very happy with the performance so far. I think the oil level in the gearbox is low and might be contributing to the shifting problems. 

The camera has built in GPS which I then feed into software called "Dashware" which produces the overlay. Its very customisable, and I highly recommend it.

I think you are reading it correctly although it feels more like 1G from the driver seat.

In that video I did try it on 60% but that is still with old hard tyres. For Feb 7 I will have my sticky track tyres and it will be on bitumen rather than pebble concrete. So I am expecting to get even better launch. But only time will tell if I can make use of the 100% setting.


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## dcb (Dec 5, 2009)

galderdi said:


> So please post your 0-35MPH prediction here by Feb 6th.


Just watching the flying meatball, I'll give you 4.2 seconds with no rollout fudge. Probably gonna have traction issues with all the weight in back.

Moving as many batteries as you can to the front would help, might help with the handbrake turns as well.

fwiw, the fwd scirocco uses a 64/36 weight distribution (and launch control) for 4 second 0-40mph.


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## galderdi (Nov 17, 2015)

Here's hoping. 4.2 would be great.

The motor/gearbox is fairly similar wieght to the batterieis. I put the batteries in back to achieve fairly close to 50/50 weight distribution which will be better for khanacross (higher speed, needing better stability).

As a stop gap (just for the acceleration trial) I will move the driver seat all the way forward to get more of my weight above the front wheels. 

But you've got me thinking for motorkhana (with the handbrake turns) I could make up a frame to sit in the passenger footwell to hold the batteries. Thus moving all that weight forward getting better acceleration and handbrake turns as you've said. I'll add that to my list of future enhancements.

Another one of my future enhancements is to make adjustable upper control arms for the front suspension so I can dial in the camber.


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## galderdi (Nov 17, 2015)

Can someone check my logic/understanding?

Beng new to the whole EV world and only having test driven my EV for a total of a few minutes I am still learning about the whole experience.

I am running a Curtis controller and brushed DC motor. My understanding is the Curtis controller is not "aware" of the voltage being passed through it. It mearly controls the frequency of pulses of whatever the available voltage is. 

Therefore I am thinking as the voltage decreases between charges I will need to use more pedal to result in more frequent pulses to achieve the same performance as I was getting with freshly charged batteries.

Is my thinking correct? 
Is this a common experience?
Or is performance more about current than voltage?


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## Duncan (Dec 8, 2008)

Hi
Your controller effectively controls current,
It changes the mark/space ratio until it's current sensor sees a current that matches the "demand" from your throttle

So if 500amps = full current and you are at half throttle it will control the on/off periods until the current it senses = 250 amps

Example -
So you are stationary - you hit full power
500 amps with a stationary motor = 15v (ish) the controller goes to 10% ON 90%OFF
At 1000 rpm with 30v Back EMF it requires 15v + 30v = 45v so it will be at more like 40% ON 60% OFF
As your revs rise the percentage ON will rise until at 100% your controller cant give any more and your current will drop as the revs rise further


So you won't need to use more throttle BUT you will hit the maxed out bit at lower revs with a lower voltage


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## dougingraham (Jul 26, 2011)

galderdi said:


> I am running a Curtis controller and brushed DC motor. My understanding is the Curtis controller is not "aware" of the voltage being passed through it. It mearly controls the frequency of pulses of whatever the available voltage is.
> 
> Therefore I am thinking as the voltage decreases between charges I will need to use more pedal to result in more frequent pulses to achieve the same performance as I was getting with freshly charged batteries.
> 
> ...


Most controllers are configured to do what is called Torque Control. The more throttle you apply the more torque. Torque is directly proportional to current. However, the way the controller works all it is able to do is adjust the motor voltage. So there is a control loop that causes the motor control to adjust the output voltage in order to regulate the motor current. The controller that operates in torque mode must be very aware of the motor voltage. The motor current will always be greater than or equal to the battery current.

It is difficult (unnatural) to control a car by directly controlling the motor voltage.

When the battery voltage declines with state of charge or sag due to load you will experience a decrease in the point where the torque drops off as the RPM increases. For example, with a full battery if the torque drops off at 4000 rpm when the battery is at 3/4 voltage that point would have moved to around 3000 RPM. This is why operating at a higher battery voltage can give you a wider torque band. 

Hope that helps.


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## dcb (Dec 5, 2009)

dougingraham said:


> When the battery voltage declines with state of charge or sag due to load


the sag and onset of voltage decline will be more pronounced with smaller agm batteries, fwiw. It should affect the top end more than the low end. I don't know the particulars, but many controllers also have a low voltage cutout, which shuts down the controller if the voltage gets too low.

I assume these are them (basically)? 14.8 ah, and a 9 inch adc?
http://www.directcycleparts.com/ele...rformance-deep-cycle-battery-pc535-p-267.html

"21 minute reserve capacity with 25amp load" means a serious peukert effect here, that is basically 8.75ah at a mere 25 amps.


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## galderdi (Nov 17, 2015)

Ahh, Well thats a good news story. I was imagining I would need to predict how much pedal to use as the battery charge reduced. The scenario you have described suits me better.

So now what I am imagining is that I will use the pedal the same regardless of the State of Charge but for the faster events I may need to change gears earlier to keep within the torque band.


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## galderdi (Nov 17, 2015)

Yes the controller has a minimum voltage of 60volts from memory. I don't anticipate ever getting anywhere near that. I am starting with 150v. They are 14ah batteries. But I plan to have at least 2 sets on hand (probably 3) so I can swap through the day.

It is a 9inch Advanced DC motor.


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## dcb (Dec 5, 2009)

this might be useful for predictive purposes as well
http://www.batteryplex.com/sheets/Odyssey Application Manual.pdf

(assuming new)

at 112 amps the PC535 is good for 2 minutes of operation (3.4ah). plus a section on charging.

and a motor that can suck 800 amps.
http://www.evmotors.com.au/products/download/fb144.pdf

the battery won't draw that much except as the rpm picks up of course.

And the course looks between 1 and 2 minutes.

It will be interesting


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## galderdi (Nov 17, 2015)

These are Fullriver HC14A.
According to their specs they will give:
535A for 5 secs
435A for 15 secs
410A for 20 secs
57A for 5 mins

The courses are between 20 and 80 seconds (at my old / slow speed). Then there is usually a break of 5-10 minutes between runs.
So far I have not needed more than 200amps. 
So I am fairly confident it will work. But yes it will be close and will be interesting.


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## galderdi (Nov 17, 2015)

I have attached the latest pics of the car. I only have a few minor tasks to complete the car. Which is great because I only have 3 weekends to get it all finished.

For those of you who are in Australia the first motokhana is coming up soon on Feb 7th at Willowbank.

It is a come and try day so if you are interested I highly recommend giving it a go. PM me if you need more information.

But if you don't want to compete I still recommend coming along so you can spectate or even go for rides with the competitors (no cost).


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## EVsonic (Aug 14, 2014)

galderdi said:


> I have attached the latest pics of the car. I only have a few minor tasks to complete the car. Which is great because I only have 3 weekends to get it all finished.
> 
> For those of you who are in Australia the first motokhana is coming up soon on Feb 7th at Willowbank.
> 
> ...


Good luck mate, will be interesting to see how she goes.

Cheers Kiwi


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## galderdi (Nov 17, 2015)

Last night I put the car on a trailer and took it along to the monthly Electric Vehicle Association meeting.

It generated a fair amount of interest. There were a few questions regarding some of the directions I've taken but overall the feedback was constructive and the car was well received.

By the time I go to the next meeting I will have videos from the performance on the track.

Over the past few days I have built the final 6 of the 9 battery packs. The intent is to have 3 complete sets of 3 packs containing 4 batteries in each pack. That is 36 batteries in total but the car will only use 12 at a time. When the charge is running low I will swap 3 packs out to replace with the next 3 packs. So I have been crimping the cables for the 2nd and 3rd sets. I'm probably about 40% complete. Another few hours effort over the next few days should see that job complete. Then just a few more loose ends to tidy to complete the car ready for the first event.


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## galderdi (Nov 17, 2015)

Here are the latest pics from my project. It is almost complete.
I just need to:


Assemble my 3rd set of batteries 
Bleed the brakes 
Align the front wheels 
Sort out an issue I am having with my BMS 
Put some trim around the edges to tidy them up
 Someone asked if I would have copyright issues with the stickers on the sides. I think it will be fine as Batman is a DC Comic and this is a DC car.

So I think I am all set for the event this coming Sunday. The event is part motorkhana and park Khanacross. The motorkhana part is lower speed and lower risk, but I am a little nervous about the khanacross part as there are some solid objects and higher speeds involved. Being in an untested car, and I don't know how it will handle, I will see how self disciplined I can be with holding back for the first few runs at least.


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## galderdi (Nov 17, 2015)

Here is some video of my first ever motorkhana test in the ev special.

The first couple of runs were ok but from then on the rest of the runs through the day were a lottery. Each run would start fine but 20 seconds in I would loose power. I believe my choice of batteries is now costing me. They are not able to provide the prolonged amps required for my application. Nothing is blowing or over heating so I am fairly sure its the batteries. Looks like I will need to upgrade the batteries.


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## galderdi (Nov 17, 2015)

Here are some more videos from last Sunday.

I did some calculations. I only did two motorkhana runs on my last battery pack. (plus the few hundred meters between courses) I checked that pack and I seem to have used about 25%. Of the total pack power 2.066 Kwh that equates to about 0.26Kwh per run.

The most I would do on a competition day is 18 runs = 4.68Kwh of discharge.


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## galderdi (Nov 17, 2015)

Here is one of the videos from my last competition day

<a href="https://youtu.be/JbupTMkcw1g" target="_blank">https://youtu.be/JbupTMkcw1g</a><br />


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## Duncan (Dec 8, 2008)

Looks like great fun
When I get the device back on the road I'm going to have to get one of those cameras


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## galderdi (Nov 17, 2015)

I have done a fair bit of racing. But none of the other stuff give as good bang for buck. $45 for a whole day. Its awesome fun. They don't make this camera anymore. But sony and garmin both have their own versions. If you do get a camera with gps make sure to check out Dashware for editing the footage. It makes it so easy.


Now if I could just work out how to post them in this forum properly.


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## Duncan (Dec 8, 2008)

I like the speed and course in the top left hand window - is that easy to do?
How does it link to your throttle?


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## galderdi (Nov 17, 2015)

Duncan said:


> I like the speed and course in the top left hand window - is that easy to do?
> How does it link to your throttle?


 Those are options within the "Dashware" editing software. They are just a few I have chosen. There are many many more options. You can even add altitude (incase you get some air lol). They are super easy to set up. Although I cheat these days by copying a previous "project" and then just replacing the footage and GPS data. 

The only other trick worth noting is that often the video and GPS data are out of sync by a few seconds (usually the GPS is delayed). You can switch off the syncronisation and progress the video without progressing the GPS data. So what I do is find a spot when I am sitting still in the car, keep it syncronised at first and play the video until I see the speed pop up from 0 to 1 or 2. Then I turn off the syncronisation an rewind the video until 1 frame after the first hint of forward movement. Then I turn the synconisation back on and all is normally fine from there on. 

Each video takes about 2 minutes of effort to edit. But it takes another few minutes to process when you hit the "Create video" button. Then it takes a long time to load to Youtube. But thats probably a reflection of my internet speed.

The Throttle and Brake indicators in the footage are not actually connected to the throttle and brake at all. A bit like when I give my Boss my monthly report through interpretive dance. They are mearly a visual representation of the acceleration or deceleration. You can configure them to cut in and out when ever you like. For example I have configured the brake to stay off under mild deceleration (representing the natural slowing of the vehicle without applying the brake). But anything more than mild deceleration and the brake light shows up. I know its not technically accurate but its pretty close and does provide some clue as to what is going on with my feet.

The one I am find most useful at the moment is the G force dial. Again its not actually G forces. It is actually a representaion of acceleration and deceleration front to back and left to right. But I am presently finding this super useful in understanding what the car is doing and what it should be doing. The great thing is having the previous point of reference by looking at my old footage from my Pulsar and comparing the cornering forces and acceleration rates to the batt mobile.

From this analysis I have seen that I need to push harder through the flowing corners because I am currently only matching the corner speed of the old car but the new car is half the weight and should corner quicker. This matches what I am feeling in the car. I am timid coming in to the corners and by the time I realise I have slowed too much I don't have enough power to pick the speed up again.
Another outcome is the comparison of launch speeds (0-40kmph). Again the batt mobile is only matching the old car.
Another outcome is the comparison of acceleration from around 40-80 and beyond. This is the key difference between the cars. The old one would give around 0.5 G of acceleration while the batt mobile is only giving around 0.1 G of acceleration. 
But I am working on increasing the current to achieve these last two improvements.


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## Duncan (Dec 8, 2008)

But I am working on increasing the current to achieve these last two improvements.

You may find that it's the voltage you need to increase
I went from 144v and a 500amp controller to 130v and a 1000amp controller
It was great - leapt out of the corners - then my tiger turned into a pussy cat and it poodled along the straights

The drop from 144v to 130v dropped my top speed down from over 110Kph (not sure where) to 100Kph - full throttle just sat at that speed


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## galderdi (Nov 17, 2015)

Duncan said:


> You may find that it's the voltage you need to increase
> I went from 144v and a 500amp controller to 130v and a 1000amp controller
> It was great - leapt out of the corners - then my tiger turned into a pussy cat and it poodled along the straights
> 
> The drop from 144v to 130v dropped my top speed down from over 110Kph (not sure where) to 100Kph - full throttle just sat at that speed


I sure do hope you are wrong. That doesn't feel like my scenario. My scenario feels more like a torque issue rather than power/revs. Each time I ask the motor to produce more torque by going up a gear it gets weaker and weaker. Third gear is a high as I have bothered to go because it won't accelerate in 3rd so there is no way it would accelerate in 4th of 5th. 
But I do get what you are saying. Increasing the voltage would certainly increase the top speed in each gear. But without increasing the current I will never get to that top speed anyway. I am planning on another test this Sunday. So I will provide an update Sunday night.


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## Duncan (Dec 8, 2008)

I forgot - you have a gearbox! 
I'm just direct drive


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## galderdi (Nov 17, 2015)

Yup, so if I am able to pump some more amps through it will be really interesting to see what it can do in the higher gears. Unfortunately I won't get the chance to try it at higher speeds for a few months. The next event is a motorkhana so I won't get past 2nd.


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## Duncan (Dec 8, 2008)

Just re-read your thread - 300 amp controller

You NEED more amps!! - a 1000 amp controller would be just about right!

I have the next size up motor (11 inch) - I'm a good 150Kg heavier and I am direct drive - the same as stuck in fourth gear

I get a bit more torque/amp because of the larger frame motor - but not a lot

If you had 500 amps like my first controller you would have nearly double the torque
wouldn't that be fun!


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## galderdi (Nov 17, 2015)

Duncan said:


> Just re-read your thread - 300 amp controller
> 
> You NEED more amps!! - a 1000 amp controller would be just about right!
> 
> ...


 
Not quite. I do have the 500amp controller. So that is not my bottleneck.
In standard form I beleive the motor is only rated to 400amps. But that is still not my bottleneck. I only have a 300amp fuse at the moment, but I have some 400amp fuses on their way. So that won't be my bottleneck.
The cables should be okay for short periods of 400amps followed by a few minutes to disperse any heat built up. So that shouldn't be my bottleneck. But if I start finding excessive heat in the cables I will double the capacity.

I beleive my real bottleneck is the internal limits of the batteries. I beleive Chev have limited the batteries to 350amps.
But that would be enough to get me out of trouble for the next few months while I iron the bugs out of the car. Then I can look at alternate batteries.


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## Duncan (Dec 8, 2008)

Hi

A couple of points
Battery current is NOT motor current (until the controller is maxed out)

A 300 amp fuse will take a lot more for a short period - at 400amps it may take a minute or more to blow

Motor current is a time/current thing - mine is continuously rated at about 200amps but it will take 1000+ for a short time

I suggest you dial your controller current up to max - 500 amps and look at your battery current

Example
0 rpm - motor voltage 15v motor current 500amps = battery voltage 150v battery current 50amps
1000 rpm - motor voltage 15v+35v BEMF motor current 500amps = battery voltage 150v battery current 166amps
2000 rpm - motor voltage 15v + 70vBEMF motor current 500amps = battery voltage 150v battery current 283amps

The magic of DC controllers - Power In = Power Out!!


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## galderdi (Nov 17, 2015)

OK, well that is some good news. That will save a lot of adjustment time. I was planning a series of minor tweaks until I reached 350 amps.

So I will turn it up to 100% and stick the 400amp fuse in and that should handle it. Unfortunately the weather is closing in this weekend so it will have to wait for another week or so before the next meaningful test.


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## piotrsko (Dec 9, 2007)

If your talking chev volt batteries, they are good for 500 amps (C5) for 15 seconds at a whack for 2 years so far. I am water cooled however. And they sag terribly at that rate.


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## galderdi (Nov 17, 2015)

piotrsko said:


> If your talking chev volt batteries, they are good for 500 amps (C5) for 15 seconds at a whack for 2 years so far. I am water cooled however. And they sag terribly at that rate.


Thanks. That is great information. 15 seconds probably isn't long enough. But if I can get 30seconds at 400amps with less sag I think I'd be doing well. Or even 1 minute at 350amps. Mine are also cooled.


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## Duncan (Dec 8, 2008)

Hi galderi

I think you are worrying too much,
The sort of relatively low speed auto-sport we are likely to do is short power bursts,

The other thing that helps is that at lower speeds the motor current to battery current thing comes in

You hit full power off the line - 500amps - the battery current starts at 50amps and rises - you probably won't exceed 350 amps for more than a second or two before you are braking 

Even in a 90 second run you are probably only going to be braking the 350amps for less than 20 seconds - and that will be split into lots of bits of less than 5 seconds


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## galderdi (Nov 17, 2015)

You are correct. I am treading very carefully. I don't want to be "That idiot that rushed in and blew his car up" or worse "blew himself up". I am gaining a lot of knowledge and experience along this journey and I am thankful to everyone who has contributed.

I am certainly keen to push the car up to it's limits. But I would rather ease up to that limit rather than guess where the limit is and risk stepping over it and not being able to step back. 

Having said all that I have turned the controller up. I just need the right conditions to give it a whirl.


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## piotrsko (Dec 9, 2007)

This is electric. Things don't blow up. Mostly they MELT, then do funny flashing popping sparkly things which annoys the local fire authority.

Note the statement: melt. If it doesn't get that hot, things tend to not go brzzzt pop! (Controllers excepted).

If you can comfortably put your hand on an item after a run, it should be mostly ok.

Invest in temperature measuring devices.


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## galderdi (Nov 17, 2015)

piotrsko said:


> This is electric. Things don't blow up. Mostly they MELT, then do funny flashing popping sparkly things which annoys the local fire authority.
> 
> Note the statement: melt. If it doesn't get that hot, things tend to not go brzzzt pop! (Controllers excepted).
> 
> ...


Why doesn't that put me at ease?

It's all good. At the moment everything is really cool. I struggle to even detect warmth. But yes this is why I want to ease into it rather than gong straight from all is cool and Ok to me sitting in amongst a lava flow. I do have a suitable temperature sensor but so far I haven't needed it. It will likely become more important as I start getting closer to the limits.


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## galderdi (Nov 17, 2015)

Did some maintenance on my motor this past weekend.

I purchased another motor on the weekend. Long term I intend to use this one for my next project (An even faster accelerating car). Short term I have stolen a few springs from it to use on the original motor to get it back up to scratch. 
It's a very good thing I decided to do this as the brushes were in a very poor state and had I driven it for much longer would have destroyed the motor. You can see in the photo the brushes are not protruding into the centre, even though there is nothing to stop them. They should be almost touching in the centre of the ring. I believe before I purchased the motor it had been sitting for a lengthy period which resulted in the brushes seizing in place. Some of them needed significant force to free them. I believe under heavy load this caused some arching and is the cause of the scorching you can see in the photos. I have now cleaned up all the brushes so they move freely and I replaced 4 of the 8 springs due to scorching. It's all back together now and running better than it ever has.

I took a few videos of the tests after I put it back together. You can see in the view from the back of the car I was experimenting with launching from different gears (1st, 2nd and 3rd). All in all its feeling great. Can’t wait for the next event.
Two of those videos are using a 360 degree camera so try moving the view around.

https://www.youtube.com/watch?v=ULgkdePEJII
https://www.youtube.com/watch?v=dQ5yJ8B2sVE
https://www.youtube.com/watch?v=QwjjB9gFaSk


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## galderdi (Nov 17, 2015)

It's been too long between events. But the next one is looming large now. It is a motorkhana on this Sunday Aug 7 at Willowbank. If anyone local to Sth East QLD is interested please come along. Spectators are free. I am confident I am past all my teething problems and I am expecting a better indication of how competitive the car can be. I am litterally expecting 30-40% better power. But obviously grip is a variable that will limit my ability to use the power. But I have introduced launch control and put wide slicks on the front. Either way it will be exciting. Hopefully I will have some good videos to share early next week.

Then the following event is another motorkhana. But then the final event for 2016 is a khanacross on Nov 7th. My car is much more suited to Khanacross so I am holding on to the hope of reaching first place in class and even first place outright at this event. But that is an optimistic goal given the jump from 2nd in class and 10th outright at the last khanacross. 

This weekend I intend to do a couple of sneaky speed tests to see if my latest improvements are having the expected impacts on 3rd and 4th gear acceleration. From these tests I will have a much better idea how it will go in November.


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## Duncan (Dec 8, 2008)

"Launch control?"

Tell us more


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## galderdi (Nov 17, 2015)

It's not quite as exciting as it sounds. 

Firstly my requirements. I need to maximise my launch in a repeatable way. In a petrol car all you do is rev the engine at a desired speed before dropping the clutch. You can reach the desired revs either with the tacho or by ear. You get to know how hard to rev to maximise the launch.

In my car I am launching with the car already in gear. I could guess how far to depress the pedal to get minimum wheel spin and maximum launch. But the result wpould be unreliable. On 1 attempt I might over cook it at spin the wheels too much, on the next attempt I might be too tentative and not feed it enough power to get a good launch.

I need to be able to quickly depress the accelerator without hesitation but also consistantly finding the optimum power for maximum launch and minimum wheel spin. So I introduced a dial and a button. The dial has a set of resistors, probably reducing the accelerator pedal anywhere from 100% down to about 40%. The selected resistor is only introduced into the circuit when the button is depressed. 

So the idea is at the beginning of the day I will take the time to test the grip by pressing the accelerator fully from a standing start repeatedly turning the dial until there is only a hint of wheel spin. Then at the start line I will hold the button while I launch off the line giving me reduced power. I will hold it for about .45 to 1 second to get past that time when wheel spin is a factor. Then I will release the button which will then give me 100% of the available power. 

I have tested it at home and I think it works a treat. It will be even more important when I am competing in the wet.


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## galderdi (Nov 17, 2015)

Here are a couple of photos. 

The Launch control dial is the smaller one towards the bottom of the dash.
The larger dial is the pedal sensitivity/power dial. The larger dial impacts the pedal immediatly and is more useful for choosing whether to put around and put it on the trailer safely versus 100% mode when I am racing.

The other photo shows the launch control button just behind the gear lever. I had to place it somewhere safer where it wouldn't be accidentally pushed.


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## Duncan (Dec 8, 2008)

I think I am going to steal your idea!

I have been thinking about something based on a dual boat throttle so that It would automatically reduce throttle when the rear wheels were going faster than the front wheels - I may still go there sometime in the future

But for now I am definitely stealing that idea


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## galderdi (Nov 17, 2015)

I am happy if it helps. I have had a lot of suggestions to go down the true traction control path. But for me it doesn't make sense. It is complicated to set up and there are times when I want the wheel spin. So this is a simple method that still gives me the control.

The larger dial is the best thing I ever did. It gives me so much more control and makes it drivable at low speed. Trying to drive it at low speed with the pedal set to 100% makes it buck and launch. It either doesn't move at all or wants to move at light speed. With the dial I can bring it back to about 20-30% and its perfect for moving it around my yard etc with no risk of slipping on the throttle and putting it through the side of my garage. Most of the time I will only use 30% and 100% but I suspect I might use the settings in between if I compete in the wet.


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## galderdi (Nov 17, 2015)

Duncan said:


> I think I am going to steal your idea!
> 
> I have been thinking about something based on a dual boat throttle so that It would automatically reduce throttle when the rear wheels were going faster than the front wheels - I may still go there sometime in the future
> 
> But for now I am definitely stealing that idea


By the way, if you have front and rear wheels on your boat you are doing it wrong


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## galderdi (Nov 17, 2015)

Ok so that didn't go to plan!!

The car survived the day but was mediocre at best. The driver has a lot to answer for. In hindsight when it broke so early at the previous few motorkhana days it limited my ability to learn the car. So yesterday that lack of knowledge finally became apparent. More time behind the wheel will fix that.

But the performance is still an issue. Before the event I had the chance to take it for a test drive down the 1/4 mile drag strip. I saw absolutely 0% improvement compared to previous events!!!
I was/am perplexed. I have the controller turned up fully and I fixed an issue with siezed brushes. How could I not be seeing any improvement at all. This was the first time I have had the chance to test for absolute top speed (not having to slow for corners etc. I did not manage to get more than 90kmph. It's pretty obvious something is wrong. This motor and controller should be able to do that with a car 3 times the weight.

I have a few theories. 
Maybe I am seeing a recurrence of the siezed brushes. I am not sure how that would be possible but I will check anyway. Its unlikely to be the brushes this time but it could be a problem with one or more of the springs. 
Maybe my accelerator pedal is not giving the correct resistance. Again in theory it is correct but I might try adding a resistor in series to bump the resistance up by 1Kohm. 
Maybe I have a weak point in my conductors. I will try doubling up some of the conductors in some obvious areas to see if I can eliminate any weaknesses. I had been operating under the assumption that the conductors would be getting warm if they were not up to the task. But maybe they are up to the task 95% of the time and the 5% when I need full current is not long enough to get them warm.

Any suggestions?


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## Duncan (Dec 8, 2008)

Hi
Unplug/disconnect your throttle and measure the resistance

What actually happened on the 1/4 mile?
can you talk us through it?
Are you measuring motor or battery current? 
If not you need something like a Cycle Analyst 

If you can see battery voltage and current it will tell you a ton - especially on something like a 1/4 mile when you have time to look at it


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## galderdi (Nov 17, 2015)

Duncan said:


> Hi
> Unplug/disconnect your throttle and measure the resistance
> 
> What actually happened on the 1/4 mile?
> ...


I measured the throttle resistance before installing it and from memory it was correct. I will recheck it. But even if it is correct (according to the manual) I want to try upping the resistance anyway. Just in case my controller differs from the version of the manual I downloaded.

I do have a volt meter and Ammeter. They are connected between the batteries and controller. To be honest I was too chicken to look down at them because the car was railroading all over the place. The 1/4 mile run was pretty much the same as all my previous speed tests. Launch in 1st gear was fine as always, 2nd gear was average, 3rd was slow but got me up to about 85kmph and I even tried 4th but it hardly raised the speed at all. Its like the whole system is limited to around 65% of it's potential. 90kmph tops in a 500KG car (600KG including me) there is obviously something drastically wrong. 

I do want a data logger but the local distributor is a bit slack in getting back to me.


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## Duncan (Dec 8, 2008)

Hi
On the 1/4 mile when did you "top out" - before the 1/8th??? later?
And what time did you do?

Last time I was on a 1/4 mile (only time!)
The device is about 850kg with me in it - direct drive 4.1:1 diff 
Took off really well - but stopped accelerating well before the 1/8th mile mark at just below 100kph
18 seconds - but half of that was just driving along
Full throttle - but only 200amps - voltage sagged down to about 115v
The device is not yet back on the road so I don't KNOW what was wrong but I am blaming a lack of battery voltage


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## galderdi (Nov 17, 2015)

Duncan said:


> Hi
> On the 1/4 mile when did you "top out" - before the 1/8th??? later?
> And what time did you do?
> 
> ...


 When I say I was on the 1/4 mile, I was just borrowing their track. Nobody else was there so the timers etc were not operating. Plus I topped out well before 1/8 so I didn't bother using the whole length of the track.
I know I started with 168volts and I am fairly sure it sagged by around 4 volts. Its taking me about 7 or 8 seconds to get to 85 kmph running through 1,2 and 3 gears.


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## kennybobby (Aug 10, 2012)

galderdi said:


> ...I know I started with 168volts and I am fairly sure it sagged by around 4 volts. Its taking me about 7 or 8 seconds to get to 85 kmph running through 1,2 and 3 gears.


Based upon your car weight and these few data values, it looks like about 22 kW or 30 HP drawing 140 Amps neglecting tire friction and aero losses just for the acceleration.

What's the motor power rating?


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## galderdi (Nov 17, 2015)

Its an advanced DC 9 inch FB1-4001.

Theoretically it would be 72KW if it ever received full volts and current at the same time 144v and 500amps. But I know that will never happen. 

But even if it was using 120v at 250amps thats 30KW. Thats probably about where it ends at the moment (as you say allowing for aero and friction). 

But I think I should be able to achieve say 120v at 350amps at 42KW.

I would have thought the "massive torque" should have at least been able to increase the speed in 4th but no go.


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## Duncan (Dec 8, 2008)

Hi Galderdi

It really does not sound as if you are getting the current that you should,
I know you are waiting for a data-logger but could you arrange your camera to video the current and voltage while you take it for a blast?


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## galderdi (Nov 17, 2015)

Yeah I have considered that a few times. But I have struggled to come up with a suitable way to mount the camera. I will need to do it though. But also the meter is between the batteries and the controller so I don't think it will fully answer the question as I won't know what is going on between the controller and motor. If I wanted to measure current between the controller and motor which lead si the most appropriate?

I also want to redo some of my cables just to make sure they aren't introducing any resistance (weak points).

I also now advanced the brushes 10 degrees. I tested it in my driveway but its not a good enough test to proove anything.


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## Karter2 (Nov 17, 2011)

Battery volts & Amps will give a good idea of how much power the motor is pulling.
Even if you Just hand hold the camera near the dials whilst you do a brief full power "pull" ....it could give a enough info to see if there is a problem.


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## galderdi (Nov 17, 2015)

The only place I can test the car is on my driveway. This involves threading the needle into the garage as I begin to slow the car down. Its not something I want to be doing with a camera in my hand.

However I might borrow one of the neighbour's kids to hold the camera for me......Or I could get them to drive and I can hold the camera LOL!


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## galderdi (Nov 17, 2015)

Here is the link to the video of the speed test from last Sunday.

As you can see it is less than impressive. I only need another 10-15 Kmphy to become competitive. Hopefully I can squeeze that improvement from the brush timing plus a few other things I want to check.

https://www.youtube.com/watch?v=ZP6VLhc1HwU


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## Duncan (Dec 8, 2008)

Hi galderdi

Brush timing
Your 10 degrees advance will DROP your initial torque by about 20% - you will get it back when the revs rise

Bad connections
I just don't see that being the problem
You would only need 120v - or a lot less to get your performance so a bad connection would have to steal 50v
50v x 500amps = 25Kw - it would get VERY warm very fast!

You just don't seem to be getting the current - the only things that I can think of would be the controller or the throttle

You seem to be having to steer it a bit - have you checked your toe setting?


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## Karter2 (Nov 17, 2011)

You could consider the old "clutch dyno" test !
Chain/strap the chassis to something solid ( power pole etc) , or nose bumper against a wall, .... handbrake on,...... camera on the dials,...
Top gear, ....
...and hit max throttle for a sec or two !
see what readings you get at peak load !


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## galderdi (Nov 17, 2015)

Duncan said:


> Hi galderdi
> 
> Brush timing
> Your 10 degrees advance will DROP your initial torque by about 20% - you will get it back when the revs rise
> ...


 Awesome Feedback Duncan. That gives me confidence. It explains why I didn't feel any difference on my driveway test post timing change.
I think what I will do is drill another set of timing holes half way between neutral an 10 degrees advanced. For the lower speed motorkhanas I will run it in the 5 degree position. Then for the higher speed khanacross I will switch it back to 10 degrees advanced to get the better top end.

I am yet to check the throttle. Probably won't be this weekend. Very likely will be next weekend. The manual calls for 4500ohms maximum I'll have a play and see what I can work out.

I still think there is a chance its a connection issue. My thinking is that is not steeling volts, its steeling amps. There is a couple of points in particular that I am concerned about. I will at least address them and see what happens. Nothing to lose. 

There is still a slight chance the controller is not turned up all the way. The dial is hidden inside the controller and is near impossible to see. So its difficult to know if its turned up all the way. I have tried turning it and it doesn't want to go any further.

The alignment was wrong on the day. I had a little play in one side of the steering (now fixed). Plus I had aligned it to be straight under zero load which resulted in severe Toe in under load. I will be redoing the alignment to start at 4mm Toe out.


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## galderdi (Nov 17, 2015)

Karter2 said:


> You could consider the old "clutch dyno" test !
> Chain/strap the chassis to something solid ( power pole etc) , or nose bumper against a wall, .... handbrake on,...... camera on the dials,...
> Top gear, ....
> ...and hit max throttle for a sec or two !
> see what readings you get at peak load !


I have tried similar tests and I will again. I just need someone to hold the camera for me.


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## Karter2 (Nov 17, 2011)

Why ?.. You wont be using your hands, just clutch and throttle .


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## Duncan (Dec 8, 2008)

Karter2 said:


> Why ?.. You wont be using your hands, just clutch and throttle .



just throttle


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## galderdi (Nov 17, 2015)

Doh!!!

Very good point. I guess it doesn't sound natural to be pressing the pedal without hands on the wheel. I will likely be doing this on dirt so I will need my helmet on otherwise I won't be able to see for a month after all the dirt gets flicked at my face.

By the way, just in case anyone is interested I have now created a Youtube channel and facebook page. You can check them out here:

https://www.youtube.com/channel/UCnE...ehgrxXcohzWiYQ
https://www.facebook.com/fullchargemotorsport/


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## galderdi (Nov 17, 2015)

I didn't get to do much on the car over the weekend. But I did measure the resistance of the throttle. The upper limit is 4.7Kohms. Right smack in the middle of the range suggested in the manual. 4.5Kohms is suppose to give full acceleration. 

I still have few more tests to perform. I will see what I can come up with.


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## galderdi (Nov 17, 2015)

Duncan said:


> Hi galderdi
> 
> Brush timing
> Your 10 degrees advance will DROP your initial torque by about 20% - you will get it back when the revs rise


So the way I see it I have three choices regarding the timing:

#1 Leave it in neutral - I need to exclude this option as the higher volts are destroying my brush springs.
#2 Create a new set of bolt holes at 5 degrees as a compromise between the torque and the higher voltage.
#3 Use the 10 degrees advanced position.

When you say I should get it back at higher revs....which option do you think would give the best overall result?

I am tending towards #3 because the overall lack of power is some other problem. So when I fix the other problem I will end up with more torque and better top end.


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## Duncan (Dec 8, 2008)

Hi Galderdi

_"I still think there is a chance its a connection issue. My thinking is that is not steeling volts, its steeling amps."_

It doesn't work that way! - you can't lose amps - the only way would be for a bad connection to drop the voltage enough to then drop the amps

As far as the advance is concerned my tuppence worth is stick to the 10 degrees 

Have you done the "trying to push a tree" test yet?
It will only give you a very rough idea of what is happening - if you could put a voltmeter across the motor at the same time that would be very interesting

This is what I expect - if its working right
Battery voltage 160v - battery current 50amps - (These two are your current instruments)
Motor voltage 16v motor current 500amps 

If you are losing volts (because of a connection) before the controller you will see MORE battery current

If your controller is (as I suspect) controlling to a lower current then you will see LESS battery current


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## galderdi (Nov 17, 2015)

Duncan said:


> Hi Galderdi
> 
> _"I still think there is a chance its a connection issue. My thinking is that is not steeling volts, its steeling amps."_
> 
> ...



Sorry I shouldn't have said steeling amps. I meant to say capping the amps because some component can't handle the full current but the current isn't there long enough to blow the component.

I haven't done the tes yet. I plan to do it this weekend.

The manual for the controller recommeds a 5kohm pot and it cuts out completely at 7kohms assuming there is a fault. But the manual also says peak power should be at 4.5Kohms. My pedal peak is at 4.7Kohms so I am in two minds whether another 300 ohms could increase my peak power.

The other thought that crossed my mind is that the motor was new but had been sitting for many years (assumed) unused. So even now the motor has probably only done 100Km. So maybe the brushes are not fully seated and therefore unable to transfer the full current. I will run it in neutral for a few more hours to seat the brushes better.


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## galderdi (Nov 17, 2015)

Your comments have made me think maybe the problem is on the far side of the controller. If there is a bad connection up there it could be dropping volts and I won't see it on the battery side.

Also another observation. The connection points on the motor have the usual bolt through the case then an insulating washer then a nut but there is no second nut. So I have put the terminal on the bolt directly on top of the insulator then securing it with the single nut. But it means the terminal is not held between two nuts as I would normally expect. Could this cause a performance issue?


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## galderdi (Nov 17, 2015)

Maybe my expectations are too high. But I really expected better performance. My expectations were based on the fact these motors get reasonable results pulling a car 3 times the weight. If I was managing to get it up to 12kmph I would be fairly satisfied but 90kmph in a 500kg car just doesn't seem to correllate with all the results for all the other vehicles out there.


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## Karter2 (Nov 17, 2011)

galderdi said:


> ...... The connection points on the motor have the usual bolt through the case then an insulating washer then a nut but there is no second nut. So I have put the terminal on the bolt directly on top of the insulator then securing it with the single nut. But it means the terminal is not held between two nuts as I would normally expect. Could this cause a performance issue?


. ?? Doesnt sound like an ideal connection,...but a simple and easy fix....Do it !
But you rally must get some instrumentation / data so you can stop guessing and actually see what is happening.
But again, even those volt and amp readings from the battery would be a good start. Also, Im sure you could rent or borrow a clamp on DC ammeter to hook over the motor leads. A decent one will have a "peak hold" feature so you can just hook it on, run a test drive, and read what the peak amps were.
But my money is on the controller not up to the job !


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## galderdi (Nov 17, 2015)

I do hope to fix the connections. I just need to track down the correct nuts.

I have been in contact with a vendor of a suitable data logging tool. But he is quite slack at responding to messages.

I have a clamp meter but it doesn't have the peak hold feature.
Which motor lead would I put it on?

If it ends up being the controller I am stuffed! I can't afford to buy a replacement. If that is the case I will just have to make do with the performance I do have.


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## Duncan (Dec 8, 2008)

Hi Galderdi

A decent controller does not have to cost the earth
I started off with a Paul & Sabrina OpenRevolt - that made my car at 50% heavier AND effectively stuck in top gear pretty good
I've sold the old one unfortunately or I could have let you have it

I wonder if Paul has any of his boards for the 1400amp one left


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## galderdi (Nov 17, 2015)

I checked into those controllers. I don't see any bigger than the 144v 500 amp. I don't think one of those would fit the bill. I have sent them an Email asking for advice.

By the way I just realised the link to my youtube channel was incomplete. Try this one:

https://www.youtube.com/channel/UCnEGxozdhehgrxXcohzWiYQ


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## piotrsko (Dec 9, 2007)

Over on ecomodder, I was under the impression you could go as high as 350 v and 1200 amps. It is a DIY controller dependent on your IGBT buy.


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## galderdi (Nov 17, 2015)

Here is an initial design for my next project. The last car was more suited to Khanacross. It could do motorkhana too but it was never going to be competitive due to the size and weight. This new project will be dedicated to motorkhana. The target is to be sub 300kg and it will use the ADC 8 inch motor. I will need to tweak a few of the dimensions and the batteries won't sit like that. I will probably slide the driver to the right by a couple of inches and place all the batteries down the left side.

I already have the motor, but realistically it is about 18 months off. I don't want to distract from getting the Batt mbile from being competitive at khanacross. I hope to have the next car ready to compete mid way through 2018. I will use 2018 to iron the bugs out in preparation for an all out asault on the 2019 season.


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## galderdi (Nov 17, 2015)

Quick Update:

I have installed the new controller, BMS and related systems. However I am striking a couple of errors. I have been progressively working my way through them but I am at a dead end.
The two remaining errors are Precharge error and Insulation fault.

The precharge error comes up when I am plugged into my 100V Lead acid pack but goes away when I plug into my 170v Lithium pack. So I am fairly confident this will be caused by the 100V being under some minimum voltage threshold.

I have measured the resistance from the chassis to the Traction battery and I am seeing infinite resistance (I would think this is a good thing). But even with the motor disconnected I am receiving the insulation error.
The manual talks about the system measuring any power across the chassis but I have not connected anything to the chassis. I suspect that might be the cause of the error. The diagram does not clearly state where the chassis should be connected. I only see 3 ground connections in the wiring diagram: 1 to the 12v battery, 1 to the Current sensor and 1 to the Temp sensor. None of these stand out as being the chassis circuit. I'd rather not guess.

I have sent an Email to the supplier of the system. Given the time difference I expect a response in a couple of days.

Unfortunately these errors caused me to miss my last event which was a Khanacross held last Sunday. Hopefully I can get it all sorted before the next event whigh is a Motorkhana on Nov 27th.


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## galderdi (Nov 17, 2015)

I was fairly ill over the weekend so I hardly touched the car. However I managed to make more progress in 10 minutes than I had in the prevous 3-4 weekends combined.

It turns out it helps if you turn the system on. (Ok that makes it sound a bit to simple/embarrassing).

In reality there are stages to turning it on. On the old system I noticed a problem with the voltage but proceeded to activate the final switch anyway which caused a small explosion in the old controller. On the new system when I received the error at that same stage I was hesitant to activate that final switch. But it turned out all the errors disappeared once it was fully operational. It was to some degree a leap of faith.

I am not out of the woods yet but it does give me hope for the next event on Nov 27.

Here is my list to work through before then:
• Enter EVMS parameters / limits
• Replace top right rear control arm
• Replace all the cable ties removed during testing
• Put side cover back on
• Replace top motor cover
• Test controller out of gear
• Test controller in gear
• Test on ground
• Replace fuses
• Replace contactors
• Increase limits
• Perform a general check
• Flush coolant


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## galderdi (Nov 17, 2015)

I made some great progress on the electric car this weekend. I have now adjusted the rear suspension. The camber on the right rear wheel is now the same as the left rear. More importantly I managed to get it running again with the new controller. I did need to introduce a manual precharge resistor and switch off the one built into the system. I also found an error in my throttle wiring, which took about 30 minutes to correct.

With my next event looming next Sunday I couldn't afford too much testing time as I won't have time to recharge the batteries fully. But I did a few test runs and the results are promising. I started at an output of 500amps and increased to 600amps for the later tests. I also decreased the throttle ramping as I was experiencing some noticeable delay in throttle response.

I still have a few bits and pieces that need to be done before next sunday but they are all fairly minor. 
The next update should be a report of how it/I perform this Sunday.


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## galderdi (Nov 17, 2015)

The event went quite well. I haven't seen the results yet but I should be a fair way up the standings.
I did make a bit of a mistake on my third run when I got a bit sideways right at the end and found myself across the finish line but unable to cross it. I had to do an extra loop so I could cross the line. It would have cost me a few extra seconds. I was up against a heap of Porsches and Clubmans. It was 35 degrees Celsius so controller heat was a concern but it survived.

Here is a playlist of all 12 runs:
https://www.youtube.com/watch?v=WIR_4pr ... AzZXr7FxPj


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## galderdi (Nov 17, 2015)

We had our presentation night on Saturday.I achieved a 1st in class for the khanacross season and a 2nd in class for the motorkhana season (yes there were others in my class).
I also achieved 1st in class for the Vice president's motorkhana (single event).
Since the last event I have learned of some minor configuration issues that were introducing some throttle lag and limiting the current/acceleration to around half the capacity. I have rechecked the wiring diagram and I can see I need to re-wire it so it retains connection to the aux battery between runs. Then it will retain the Throttle ramp setting of 0 instead of 1 and max motor amps of 800+amps instead of defaulting to 500amps. So I am super confident I can see some significant improvements in the coming year.In the last event for the year I placed 6th outright beating 8 out of 10 Porsches and 4 out of 4 Caterhams. The 2016 results are reasonable results considering it was largely a development year. I have certainly learnt heaps and I am now aiming for outright results in 2017.


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## Duncan (Dec 8, 2008)

Hi
I took the Device to an Autocross on Saturday - great fun
This was on grass and it was much much smoother than I expected,
I did take my roll bar camera for it's first outing but the remote failed and I didn't realize that I hadn't switched the bloody thing on - zero video!

Nowhere near the top of the listings - but not near the bottom either

I used your throttle resistor idea to limit power - still spun out once
Then on the last run I set to full - if anything it was easier to control with more torque available - and I set my fastest time

I do have quite a lot of throttle travel with my home made throttle pot (converted Subaru TPS) - it might be easier with less throttle travel


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## galderdi (Nov 17, 2015)

Duncan said:


> Hi
> I took the Device to an Autocross on Saturday - great fun
> This was on grass and it was much much smoother than I expected,
> I did take my roll bar camera for it's first outing but the remote failed and I didn't realize that I hadn't switched the bloody thing on - zero video!
> ...


 Well done for getting out there and giving it a go. Most people never muster up enough courage. I have spoken to dozens of people who sound keen but then never turn up. Even when I offer for them to drive my car. I don't get it. Anyways..... I actually have two of those resistor setups on the car currently. 

The original one is just a dial which selects which resistor to place in parrallel to the throttle. It effectively give me the choice of 10% - 100% in 10% increments. With my old controller settings 1-3 were useless. With my new controller 1-6 are useless. I don't think the throttle ramp on the new controller is linear.

The second one is another dial which selects resistor to place in parrallel to the throttle. But this one only applies the resisor to the throttle when I hold a button. This one is intended to give better control during launch, once the launch is complete I release the button and from then on I have 100% power available.

With my old controller the original dial was a necessity as the car was unable to be driven smoothly / safely at low speed set to 100%. So when I wanted to load on the trailer or move around people I would set it to about 40% giving much better control. With the new controller it's not as necessary for that reason......But I also intend to allow the car to be driven by new comers to my sport. So on those occasions it will still be useful to limit their power until I am convinced they can handle it (No!!! it has nothing to do with ensuring they can't beat me in my own car!!......well ok maybe just a little). So it sounds like your throttle / controller combination brings the power on smoothly and allows you fairly good control at the lower end. Yay!


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## Duncan (Dec 8, 2008)

Hi Galderdi
Mine is nice and smooth - no problem loading onto the trailer
But I do set to about 43% for driving in town - it is just too scary on the main road if I give it full throttle

I have three resistors
Fine - 90%
Medium - 80% (fine + medium together)
Coarse - 48%
All three - 43%

With a passenger I don't spin the tires (on good tarmac)

Shame I buggered up the video - better luck next time


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## dcb (Dec 5, 2009)

fwiw, you might consider "exponential control" on the throttle, used on twitchy rc planes all the time. large motions make small changes at low throttle, and small motions make large changes near full throttle.

An audio taper pot might work, or fancy little circuit, if not built-in to controller.

(and of course make full use of pedal travel so you don't have wasted motion)


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## galderdi (Nov 17, 2015)

If anything the curve on my throttle is already too harsh.

I get absolutely nothing for the first 60% of the travel then it comes on quite sudennly.

I have a few minor adjustments to make. The most significant adjustment is the replacement of the rear control arms (again). The first time around I fluked it. The geometry was perfect. Then I broke one due to insufficient material around a pivot. But I have already had two attempts at the replacement and just can't get the geometry right. At the moment the camber is too harsh an the right side is toe out. So this time I will make the lower control arms adjustable.

The events I am aiming for are:


A casual (come and try) motorkhana Feb 12 
A club level motorkhana March 12 
A stat championship round motorkhana March 25 & 26
 The third one is to be held in Gladstone, about 8 hours north.....roadtrip!!!! 
For that event in 2016 I had no charger so I went up there with about 20% charge and only lasted 5 runs. It was very dissappointing to go all that way and not event complete 50% of one day.


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## galderdi (Nov 17, 2015)

ver the Christmas break I made a couple of minor improvements.

I added a heat shield between the motor and controller. Last time I competed the heat was rising from the motor into the controller and was making me nervous. If was a rather hot day, but this is Queensland so hot days are not rare. The heat shield is really excellent so I am confident this will mostly take care of the issue except if it is an exceptionally hot day (by QLD standards >35c). But I plan to also install a fan to extract any stray heat from the engine bay.

I modified my rear lower control arms (2 on each side). I added some thread so I can adjust them in and out to modify the rear alignment. This gives me some camber and Toe adjustment. It can't be adjusted on the car, at least one end of each arm must be disconnected so it can be twisted in or out. 

The next event is a Motorkhana on Feb 12 followed by a couple more in March. But I am really aiming for a good result in the Khanacross April 9th.


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## galderdi (Nov 17, 2015)

My next event is a come and try motorkhana on Feb 12 at Willowbank. If anyone is in the area feel free to come and take a look. Spectators are free and I will have a spare helemet so I can take passenger rides.


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## Duncan (Dec 8, 2008)

Hi
They let you take passengers? - they would't let me take a passenger because the Device is an open car -


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## galderdi (Nov 17, 2015)

Yes, only in Motorkhana (a fair bit safer than autocross or khanacross), only on come and try days (because we aren't supposed to get too competitive on come and try days) and only when the passenger has a helmet if in an open car.


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## galderdi (Nov 17, 2015)

It ended up being 43 degrees on Sunday so the event was cancelled. I think it was a wise move.

But a few of us went out there anyway for a casual test and tune. My car went quite well. It was the best performance I have managed. I got it up to 120kmph and 0-70 was very exciting. But my rear wheel alignment is still shot. At any speed over 70kmph it was downright dangerous. I had to fight to make it track straight. The other guys had proper wheel alignment gear so I took some measurements. I need to set it back to neutral camber and adjust the toe in (its currently significantly tow out).

Here are some videos from yesterday:












 360 degree


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## itchyback (May 28, 2014)

damn why did i only find your thread today, i would have loved to come check this out!
next time maybe


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## galderdi (Nov 17, 2015)

itchyback said:


> damn why did i only find your thread today, i would have loved to come check this out!
> next time maybe


Where are you?

The next one is a motorkhana at Willowbank again on March 12.
Then I have a two day motorkhana at Gladstone March 25&26
Then I have a khanacross at Willowbank on April 9th

My car is very much suited to Khanacross rather than motorkhana so bring on April 9th!!


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## galderdi (Nov 17, 2015)

OK I am kinda struggling a bit. I have searched and searched but I can't find an answer to my question. I think it is because it's not a simple question or answer.

What maximum amps can my motor handle (ADC FB1-4001)?

What I can see is the motor should be ok up to 800amps for short periods and is fine at around 150 amps continuous.

I also understand that the ability for a motor to handle current is limited by the heat. 

So now I am thinking the following:


My usage pattern is a 9.30 am start with around 15 one minute hard runs (Full throttle) with 15-30 minute breaks in between ending around 3.30pm. The motor only seems to reach around 50-60 degrees Celsius. 
I will be running fans over the motor and controller during each of the breaks. 
So I think a sliding scale is the way to go for me. 
I think I can probably stretch the limit to 900amps for the first couple of runs while the motor temp is still relatively low. 
Then as I get more runs under my belt I can reduce the maximum current back down to 800amps when the motor is at 60 degrees or even 700amps when the motor is any hotter.
 What do people think? Are these realistic limits? Or too conservative?
I have been told the FB1-4001 can handle 1000amps but I am nervous.


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## Duncan (Dec 8, 2008)

Hi
I am running in similar events - my car is heavier and I am always in "top gear"
Even when I limited it to 40% (about 500amps) - I was at full power for only a tiny fraction of the time
That was on grass - but I'm not sure how much longer I would be at power on tarmac

I would suggest that the type of event will limit you so that the 1 minute "full power" actually looks like 5 seconds on 5 seconds off - 5 seconds on 50% - and so on

The drag guys are using 2000 amps - for about 7 seconds

With that in mind - I believe that you will be able to set your limit as high as you like!

I'm doing our 1/8th mile drags next Sunday - I'm expecting to be below 10 seconds
as far as I am aware none of the straights on Khanacross or Autocross will be as long as that - I have an idea that there is a limit of 80m 

So I would say set it as high as you like - but you may have to drop it for control-ability reasons!!

But then I only paid $100 for my motor - I might be more conservative if I had paid big bucks


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## galderdi (Nov 17, 2015)

You are correct there is certainly a limit of 80 meters on straights in Khanacross. 

There is also a rule that says the course will be designed to limit speed to 100kmph. But how can the designer predict the performance of the top cars. So that one is more of a guide than anything.

The 790amps I set as a limit is plenty for 0-50. But I would ideally need a bit more punch from 50-100. Anything over 100 is a bonus/pointless. 
Controlability in that 50-100 range will be fine event if I had 50% more power because at that speed much of the power is just fighting wind resistance.
Controlability in the 0-50 will also be fine because once I increase the limit I will start to use my launch button more regularly (to limit wheel spin). In other words the launch button will probably bring the amps down to something like 700 for the launch anyway then when I release the button I will have the extra power I require to improve my 50-100 acceleration.
This also adds weight to the view that I can nudge the 1000amps because it will really only be taken that far once or twice each run for about 3 seconds.

For motorkhana I do need to remove the throttle delay because I need the instant accleration for all the stop start stuff. But for khanacross I am contemplating leaving it set on 1 (very slight delay) as this will also improve controlability.

But I don't think the drag guys are a good point of reference as I am fairly sure they have modified their motors to handle the larger current.

I am still keen to hear other points of view?


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## Duncan (Dec 8, 2008)

_But I don't think the drag guys are a good point of reference as I am fairly sure they have modified their motors to handle the larger current._

I'm not so sure - as far as I can see the wiring and laminations are the same
About the only thing that they can play with is the brushes and the com

From the various threads they are using split brushes and brush compounds designed for higher currents
That will probably give an advantage - but not a big one! and they are using 2000 amps plus

I have set mine to 1200 amps 

What is your voltage? - I forget
At 130v I was voltage limited - by 100kph I was down to 200 amps - and that was where the aero-drag hit the current

With my current set up (340v) even with the 40% it whistles up from 50kph to 120kph pretty fast

I wonder if you are being voltage limited ?? - not as much as I was but a bit

Re "launch button" - that simply restricts current? - I'm not sure that you will be able to use more current at higher speeds - yes the wind resistance increases but I'm not at all sure that grip increases - and that is your limiting factor

Also - you have advanced the motor? that effects the current/torque ratio
My motor has 8 degrees advance - that means that at a given current my low speed torque is 20% less than my high speed torque

So that may mean that at higher rpm you need less current - or more accurately you can only use less current

You have a gearbox so that makes it more complex as well


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## galderdi (Nov 17, 2015)

Excellent, well that gives me confidence that I still have room to increase the current.

My voltage starts at 170v. most of those tests were between 155 and 165.
But I am limited to 175v with my setup. 

I am totally happy with the top speed. I really don't need more than that. In my events I would not expect to get past 105 or so. But I need to get to that speed quickly. An extra 100 amps or so will do it I think.

Yes the launch button restricts current. But it's indirect, by reducing the throttle to a preselected %. I have a dial that allows the % selection for the button.

My required improvement is in 3rd gear so my theory is that more current will overcome the wind resistance that becomes apparent at around 70 or so. My design didn't really consider aero and in hindsight I think the flat panel on the front is part of the problem. I am considering a prostetic nose added to that front panel to scoop the air over the top of the nose rather than push a bow wave along.

Grip isn't really an issue as I generally only accelerate hard once I am through the corners (ie in a straightish line). Plus I am running track tyres so my grip is pretty darn good.

Yes I have advanced the motor to the standard advanced position which I think is 10 degrees.

All in all I think a few more amps, some minor aero tweaks and some suspension adjustment will see me being very competitive this year.


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## Duncan (Dec 8, 2008)

Hi Galderdi
170v would limit my motor - 
At 100pkh - 3500 rpm I had effectively 10v to push 200amps across the motor (resistive) and about 120v BEMF - giving me 130v - which is why I only had 200 amps!

If I had 400 amps then at 3500rpm I would have 240v BEMF + 20v = 260 v
So I would have needed 260v to get 400amps at 3500rpm
I now have 340v - so that should not be a problem

If your motor is giving 1/2 the BEMF for revs and current that my one is (WAG) 

then 400amps at 3500rpm will give 120v (+20v resistive) = 140v

500 amps would give 150v + 25v = 175v

So I suspect that setting the current higher won't buy you that much - if anything

But setting the current higher AND changing up sooner may get you a bit

To expand - I suspect that you are being voltage limited at higher rpm so increasing the current won't help - you will already be on 100% 

Turning the current up will give you more available torque at lower rpm's - and won't reduce the torque at higher rpm's
So grabbing a higher gear sooner may actually give you more torque

Have you tried grabbing 4th instead of 3rd?


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## dcb (Dec 5, 2009)

yah I would think with your flying meatball interface you should be able to log several runs in each gear from slow till it is about done accelerating, then pinpoint exactly where to shift for best acceleration (where the next gear minus rpm drop and factoring in mechanical disadvantage would out-torque/out-accel the current gear).

Seat of the pants is good too 

Nice ride btw, hope you get that rear alignment sorted out.


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## galderdi (Nov 17, 2015)

Duncan said:


> Hi Galderdi
> 170v would limit my motor -
> At 100pkh - 3500 rpm I had effectively 10v to push 200amps across the motor (resistive) and about 120v BEMF - giving me 130v - which is why I only had 200 amps!
> 
> ...


 
No I haven't tried grabbing higher gears directly. I have certainly thought about it. I'll give that a go. I have tried to take off in 2nd but I wasn't happy with the resulting launch. However the reduced launch may well be offset by the ellimination of a gear change.

I am already changing up fairly quickly as I don't want to risk over spinning the motor. I am pretty much driving and changing just like the ICE motor that preceded it. (and the gearing has not changed)

It also sounds like for khanacross I will really need to put it back on charge between every run to slow the voltage drop as much as possible. Otherwise my performance by the end of the day will be disappointing.


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## major (Apr 4, 2008)

Hi Greg,

The short duration high current duty cycle typically puts the brushes/commutator at risk long before a temperature rise on the case or even the windings would indicate overload. The coil insulation is rated to 180°C and I've seen outside case temperature near 100°C for longer duration runs. Running 3 second blasts several times lap will most certainly put the brush at its limit well ahead of the coils or case.

Get an IR non contact thermometer and shoot the brushes and comm asap after the run. Undoubtedly those will cool some before your measurement. But operational limit on or actually in the brush is 200°C maybe a bit more. We would embed a thermocouple... likely not practical for you. Comm surface should not exceed 200°C for long at all. Of course these are performance limits and not recommended grocery-getters.

What you really need to watch out for is the zorch. That is when the limits of successful commutation are exceeded and severe brush arcing turns into a plasma event. I've seen cases where this plasma has actually severed off pieces of cast metal on the motor... well used to be on the motor but was retrieved from the track. 

So how do you push your motor to the acceleration (current) limit and avoid a visit fron Mr. Zorch? There is no math formula answer. He comes calling seemingly at his discretion however we do know contributing factors. Current, voltage, RPM, temperature, comm surface condition, brush seating, humidity, phase of the moon, etc.

I see no reason if you treat the motor properly you can't live for many seasons on the track at 1000A limit. Make sure you have a proper advance. Proper break in for comm film (patina) and brush seating. Arcing, which is bound to occur, short of the zorch, can strip the comm film. After hard runs the motor should be run wheels up at 1000-2000 RPM with fans blowing air across or thru it. This helps recondition the comm film and brush seat as well as mitigate to chance of heat soak distortion of the comm. Read up on comm and brush service. Get and learn to use a dial indicator to frequently check comm trueness.

If you have a rev limiter, do not stay on the throttle when it kicks in. Slow down and change gears or reset limiter higher. Pedal to metal in rev limit is a invite to Mr. Zorch.

Those dual wafer or split brushes might help. Wouldn't be a bad idea to talk with and get advice from a brush engineer. I forget the nice fellow's name at Helwig Carbon. 

Regards,

major


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## galderdi (Nov 17, 2015)

Awesome. That fills me with confidence (within reason).

I am always careful about revs. I will also be adding some more cooling for between my runs.

I had considered "idling" the motor in neutral after each run. It sounds like I will need to do that as a precaution at least for the last 2/3 of the day when the components are getting some heat. I would have thought 1000 rpm would be too high. I would have thought the lowest revs that are still sufficient to get the air moving would be ideal? 

I have also wired up a couple of external fans. I will be hanging one to push cool air in from one side and the other to pull hot air out from the other side of the motor. I just need to rig up a bracket to hold them in the correct positions. 

I do have a non contact thermometer but I need to track it down, I think its sitting somewhere with my odd socks.


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## Duncan (Dec 8, 2008)

Hi Major

Sounds like I should do the same - 2000rpm "idle" after a run
How long should I do this?


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## galderdi (Nov 17, 2015)

BTW I love the name "Mr Zorch" I would be tempted to use that as the name for my next project if it wasn't inviting disaster :-D

It looks like I will be taking a brick along to my events. Brick against peddle = idle.

I am thinking in my case I would let it idle for the whole break (until I get in ready for the next run). But if the break exceeds 15 minutes I'd turn it off.


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## major (Apr 4, 2008)

Hard to say how long. Do what is practical. Maybe use a 12V battery and jumper cables on the motor for this no load recondition period so you don't drain the traction battery. That would give your controller a cool down rest and avoid a brick on the throttle which could lead to over speed. 15 minutes and let her cool off sounds good to me.

major

ps. Get polarity correct if using 12V battery and jumpers with the controller still connected. Reverse polarity will take out the FW diode in the controller. Safe would be to disconnect one controller lead from the motor.


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## galderdi (Nov 17, 2015)

Yes you are right. Sorry I wasn't clear.

I actually meant: Rest the brick on the floor holding the peddle slightly in.

I also have the added protection of being able to use my power dial to set the maximum way down. 

I still have my old lead acid batteries and they still have anderson plugs attached so I can unplug my traction battery and plug in these extras without risk of getting it wrong. I usually run 8 in series to give around 100v


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## Duncan (Dec 8, 2008)

Hi Major
I've got direct drive so I will have to jack the back wheels off the ground 

That will cause a delay when it's all hot so I might just spend a couple of minutes gentle driving at about 50kph - 1800rpm after a run

That would get the main "heat" out - would it still be worth jacking it up and "idling" it at about that rpm afterwards?

Would the comm film rebuild better under almost no load (just the diff and wheels) or under light load poodling at 50kph?

At the Drags I will have 1/8th mile full power - then a 1/2mile drive - so 1 minute at low power to the holding area where I won't be able to do anything for a at least 20 minutes


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## galderdi (Nov 17, 2015)

Hey Duncan. Obviously the drags format is a problem. But for other situations you could make a quick jack like mine.


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## Duncan (Dec 8, 2008)

That's a good idea - looks pretty simple as well
I think I will do that!


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## galderdi (Nov 17, 2015)

I found some casters in the hardware store with fairly sturdy wheels and disassembled them. If I were to change one thing about the design. It would be to set the wheels further apart for stability. they are currently about 30mm apart. I suggest making them about 60mm apart. The bolt is an adjustment because it needs to be low for the front but needs additional height for the back.


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## Duncan (Dec 8, 2008)

Do you need the wheels?
I was thinking that the car would roll backwards on the front wheels while the jack lifted the rear

If I was going to use that at a grass autocross I would need a bit of plywood as well


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## galderdi (Nov 17, 2015)

I need the wheels because I usually have the handbrake on. If you weren't using a handbrake the car will shift as you said.

If you are using it on soft ground you could build in a "heel" instead of the wheels, so the weight doesn't drive it into the ground. A patch of steel around 100mm should do it and just curve it like a heel.


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## major (Apr 4, 2008)

Duncan said:


> Hi Major
> I've got direct drive so I will have to jack the back wheels off the ground
> 
> That will cause a delay when it's all hot so I might just spend a couple of minutes gentle driving at about 50kph - 1800rpm after a run
> ...


Hi Dunc,

Motoring at a light nice and easy load is good. Having current thru the brushes is essential in building the film. As long as the comm is cooling you're doing some good.

Regards,

major


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## galderdi (Nov 17, 2015)

I received a suggestion to start posting my results as well as the pics and vids. So here are the results from the last event last year.


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## galderdi (Nov 17, 2015)

I have finally managed to get a real charger for my car. So I am going from a 3 week turnaround to around a 3 hour turnaround. Yay!!!!


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## Duncan (Dec 8, 2008)

Hi
Just thinking about your AutoKhana car

The front wheels have to do a lot - with drive and steering and the rear wheels and suspension is pretty simple

How about steering the rear wheels as well? 
It would not be that difficult to fit a rear rack and then a shaft to the main steering rack

My Mazda had four wheel steer - they steered the opposite way at low speed and the same way at high speed 

You need really agile - I even thought about rear wheel steer for you - but I think 4 wheel steer would be better

On a separate point - have you got an LSD? - when I spin the tires I spin both rear tires - makes it bloody difficult to control!


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## galderdi (Nov 17, 2015)

Duncan said:


> Hi
> Just thinking about your AutoKhana car
> 
> The front wheels have to do a lot - with drive and steering and the rear wheels and suspension is pretty simple
> ...


Yes you are absolutely correct. However 4 wheel steer is specifically against the rules unless it was an original feature of a production car. Similar to all wheel drive. 
If it wasn't for that I would be all over it.

Yes I theoretically have an LSD however I am not convinced it is a very effective LSD as I can quite easily smoke a single tyre.


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## Duncan (Dec 8, 2008)

Easily smoke a single tire?

- you can see your front end - it's more difficult to see what is happening with mine but the video shows both smoking at the same time

I'm fairly sure that I used to smoke the left rear well before the right 

Maybe you need to do the corner jacking thing?

Do you feel that you can detect and control the loss of traction the way you used to be able to with the IC car?

It feels to me like it is much less controllable - BUT it has been about 27 years!


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## galderdi (Nov 17, 2015)

Duncan said:


> Easily smoke a single tire?
> 
> - you can see your front end - it's more difficult to see what is happening with mine but the video shows both smoking at the same time
> 
> ...


From 0 it does feel harder to control. My theory is: In an ICE car you get to know the ideal revs to sit at before dumping the clutch for a launch. In an EV you don't rev the motor and you don't dump the clutch so the perfect launch is about knowing exactly how much throttle to apply. That is dificult to get correct, quickly in real time. I tend to just hit the throttle 100% and deal with the consequences. The alternative is to push it slower and aim for some mid point. I think the results from that approach will be inconsistant. But that is why I think my launch control will play a big part in my results. After a couple of runs I can dial the launch back to a point where I get a little churp but no real wheel spin. Then once moving wheel spin is no longer an issue so I release the button making 100% of the throttle available again.

My launch button is effectively another dial with another set of resistors. When the button is idle the resistors are bypassed. When the button is pressed the chosen resistor is placed in parrallel with the throttle thus reducing the resistance seen by the controller. (Sorry if I am repeating myself). The launch resistors are compatible with the other power dial. The launch resistor reduces the throttle further in addition to any reduction from the power dial. (I hope this makes sense). In other words I can set my power dial to 80% and then apply a further reduction of 50% off the 80%. This will mostly come into play when I compete in the wet or on dirt.

Aside from launch I don't feel like control is an issue. I can still feather the throttle in real time when necessary. 

But much of this is still hypothetical for me as I really haven't had enough time behind the wheel. At least not with it's current potential. With the old controller it was a different story because I was pretty much after 100% or nothing, very little need to feather the throttle. Plus I was still a bit timid with the handling. But as I get more comfortable the performance will improve.

I can understand your dificulty when driving on dirt as you can't really hear the tyre spin. But on bitumen you should still hear it right?


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## Duncan (Dec 8, 2008)

My last event was tarmac! - video link on my thread

I can spin the rear tires at almost any time - and I can hear them spin at the same time as the car snatches out of line!

I was running on 100% - I should probably have limited it - but on nice tarmac I thought I could handle it

I should have sacrificed one run to an 80% power - but I only had three runs

(1) - took it easy
(2) - brain fade went the wrong way at one corner - we hit that corner twice - first turn left - second turn right
(3) - my best run
If I had had another I would have tried with less power - I'm sure that I am being far too tender in the corners because I know I have enough torque to spin the tires


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## galderdi (Nov 17, 2015)

Yes, I did see those videos. I guess when you were saying I could see my wheels I wasn't sure if you were implying that seeing the wheels spin give a control advantage over hearing the wheels spin. Maybe it's just a reaction time thing? Or maybe we don't want to lift off because we think we will lift off too far and lower our overall performance. I'm not sure, but I do think the best results will come from keeping just under the wheel spin.


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## galderdi (Nov 17, 2015)

A quick reminder. My next motorkhana is this Sunday (March 12) at the back of the Willowbank drag strip. If anyone is in the area feel free to pop by, spectators are free.


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## Duncan (Dec 8, 2008)

Hi galderdi
I had great fun at another grass event on Saturday

How low can I take my tire pressure? on grass - any advice?

The guys I'm running with seem to be advising much higher pressures than I was used to back on the 80's

Last run I got between the two Miata's that were running - one of them just beat me


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## galderdi (Nov 17, 2015)

Looks like weboth had some EV fun over the weekend.

It is a difficult question to answer. It really depends on the tyres. The higher the performance of the tyre the lower the pressure. This is because higher performance tyres have stiffer side walls. The better tyres I have owned would be quite good as low as 23PSI (cold on Tarmac). Some of the mid price R spec tyres I currently own are better at around 25PSI (cold on Tarmac). If you were running normal road tyres I wouldn't go below around 28PSI. Plus I would add an extra PSI or 2 for dirt. I have rolled a tyre off a rim on dirt because I was trying to run the tyres at the same pressure as tarmac. I think the difference is mainly that tarmac generates more heat in the tyre which results in a slightly higher pressure while driving. What Tyres are you running?

My weekend was great although a little stressful at the end. Our club had a come and try Motorkhana with a decent turn out. I took my new slicks but couldn't get motivated to swap them on. Plus they are expensive tyres to waste on a come and try event. The car went really well. I set it on 750amps for most of my runs. That was plenty of power to spin the wheels. I was starting to get the hang of feathering the throttle. My adjustment of the throttle has made it much more controlable. 3 of the 5 motorkhana specials dropped out after a few runs. 2 were due to mechanical issues and 1 due to a driver's previous health issue. The other special was quicker than me, as expected. Not because of power but because his car is smaller, lighter and more nimble. I will gain a little at the next event by swapping to my new tyres but I doubt I will beat him (for the same reasons). Hence why I am starting my next project. I am fairly confident I beat all the road cars so I would have come about 2nd if it wasn't a come and try day. But then, just before the last test, my car suddenly died. I checked all the usual causes but couldn't see anything obvious. Eventually we pushed it on the trailer and I called it a day. I sorta hoped the trip home would cool it off and it would be OK again, but that wasn't it. Then I got to thinking the SOC was getting sorta low by that stage. I had run it lower with the old controller but this is the lowest I had run it with the new controller. So maybe I had exceeded the controller threshold. So I went to connect the charger and realised the controller was set to "Stationary Mode". So I switched it back to "Running Mode" and it worked again. I will try and replicate this scenario this coming weekend to understand if my theory is correct. But I was quite concerned while it wasn't working because I was unsure if I would make the next 2 events on MArch 25/26 in Gladstone. But it has all worked out.


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## galderdi (Nov 17, 2015)

Oh and the rear alignment is now great. Much more stable than the Feb tests. Here are the videos from Sunday:

External view:
https://www.youtube.com/watch?v=_uXDdvUHg6Y

With GPS:
https://www.youtube.com/watch?v=asit5SQQSZc
https://www.youtube.com/watch?v=xa2w1gjgRIQ
https://www.youtube.com/watch?v=c3y_nly2_mw
https://www.youtube.com/watch?v=YYa9lguj_I4
https://www.youtube.com/watch?v=XnaZaJxcd5U
https://www.youtube.com/watch?v=KD0WnfrfIDc
https://www.youtube.com/watch?v=Tf6WaTz6M04
https://www.youtube.com/watch?v=4QpN9s1WFsM
https://www.youtube.com/watch?v=6blm59_tczY
https://www.youtube.com/watch?v=DGEAs0eIJkI

360 degree:
https://www.youtube.com/watch?v=CUJe4m1k4ZE
https://www.youtube.com/watch?v=ojP3m5nVLEY
https://www.youtube.com/watch?v=L46Kg-hptzU
https://www.youtube.com/watch?v=-3eUchGXwdM
https://www.youtube.com/watch?v=eZBPCqvG9sU
https://www.youtube.com/watch?v=ABUpOKKD9W0
https://www.youtube.com/watch?v=9mYojBCwMa0
https://www.youtube.com/watch?v=BclkWfzSe9A
https://www.youtube.com/watch?v=2RhTYfb5e_0


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## galderdi (Nov 17, 2015)

Just got the results from Sunday. It is about what I expected. 
• Every time was my personal best. 
• I only placed 7th outright because I missed 2 tests (I didn’t even realise I missed the one earlier in the day).
• Of the tests I completed I came 5th once, 4th twice and 3rd twice.
• Of those that beat me only one will be heading to Gladstone. This means I should move into second place for the club championship.
• On average I was roughly 1.5 seconds off the pace (behind first place). I don’t think I will be able to pick up the full 1.5 seconds but my good tyres will get me fairly close in Gladstone. Plus more feathering of the throttle will help too.

It is a bit of a stretch for me to expect to beat the fastest cars outright because mine is a bit bigger and heavier. But attrition plays a big part, so if I can be consistant through the year I can still place well in the motorkhana championship.

Really though the car is much better suited to Khanacross. So I am mostly focused on that championship for 2017 and I aim for a more serious crack at the motorkhana championship when I build my new car.


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## galderdi (Nov 17, 2015)

I was competing in Rounds 1 & 2 of the Queensland Motorkhana Championship in Gladstone over the weekend. 
In preparation for the event I had a trailer brake pad seperate from it's backing plate. So I replaced that before leaving as travelling for about 18 hours round trip with no trailer brakes didn't appeal to me.
I tried to adjust my clutch cable, but in the end the cable gave way and sunk into the sheath. Luckily I didn't need the clutch for this weekend anyway. 
Then when loading the car on the trailer I realised the throttle was playing up. I eventually reverted to an older throttle I had as a spare.
Luckily the weather held out despite the looming tropical Cyclone further north.
The first day the car was running very well and I was positioned in 3rd for most of the day. 
But later in the day the heat got to me and I had a brain fade moments. 
I still managed to place 6th outright which isn't bad considering I got 3 tests wrong out of 12.
At the end of the last run on day 1 it was apparrent I had developed a significant vibration. I beleived it to be a loose bolt from the flywheel or clutch plate putting the flywheel out of balance. Or potentially a worn gearbox bearing. The motor itself still seems to spin smoothly.
With little time and without my workshop facilities I could not risk separating the motor and gearbox to inspect the problem.
At the end of day 1 I was faced with the decision to protect the vehicle or continue with day 2. If the event didn't figure in the season standings I would have pulled out. 
But as it was Round 2 of the Motorkhana season I decided I would proceed with caution. 
I figured I would coast through the day with the aim to complete at least 50% to at least earn some more points towards the season championship.
On day 2 I found the vibration was worse at low revs. I was hoping it was just the clutch out of centre, but my clutch cable was out of action so I could not release the clutch to help it re-centre (if that was the problem).
But I pushed on. For any medium to long tests I selected 2nd gear from the start and turned the current up. 
This was my attempt to keep the revs at a managable level and not do any further damage. I also periodically cooled my head with ice, which I think helped me concentrate, resulting in better results.
In the end I managed to achieve 3rd outright for day 2 which was about my target coming into the weekend and well exceeded my expectation after developing the vibration.
I have packed the car away as we have some really bad weather looming for the next few days. Hopefully this weekend I will be able to pull it apart and identify the problem.
My next event is a khanacross on April 9th (2 weeks). Hopefully it is a quick fix other wise I will miss my second khanacross in a row. 
That would be devastating as the car is much better suited to khanacross and I have been really looking forward to seeing the car's true potential.


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## galderdi (Nov 17, 2015)

Having now seen the full results from the weekend I can report that I only missed 2nd place by 0.27 secs on Sunday. One less hesitation or a little more power or a little more grip and I could have had it....Yeah I know coulda, woulda, shoulda. I am still very happy with the result.
I have also now had the chance to pull the front of the car apart and diagnose the vibration. It turns out there were two issues. I am sure one caused the other but I am not sure which came first. Two of the four springs from the clutch plate popped out. The other is retainer bolt that attaches the flywheel/adaptor to the motor output shaft snapped. 
I suspect the bolt came lose ever so slighty and then this allowed the flywheel to vibrate enough to continually wack the head of the bolt until finally it gave way. Then the vibration was able to get worse and combined with a stint of higher than usual revs shook the springs lose. The main reason I suspect this is because the remains of the retainer bolt were way too easy to remove.
The other thing I found as a result of last weekend was a surprising amount of under steer. I had expected the big sticky tyres on the front to resolve the understeer, but that wasn't to be. I plan to address this with a couple of adjustments. 
I think the toe out on the front wheels might be a touch too extreme, so I will wind that in slightly.
I think the negative camber on the front is a touch too much (3 degrees). That doesn't sound like much but the geometry is designed to add more negative camber as the wheel loads up. So under load it would be more than 3 degrees. I think I will adjust it back to be 2 degrees.
Last weekend I was runnign with semi slicks on the back. I think for motorkhana I will return to running with my old/hard/cheap tyres on the back which should cause the rear to want to break lose a bit more. 
So the good news is this is all quite easy to resolve and I am confident I will have it all back together by the end of this weekend ready for the event next weekend (in time to beat some more Porsches and Clubmans).


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## Duncan (Dec 8, 2008)

Sounds good!

There don't seem to be any more events down here for me so I'm just driving around - I will get involved at the start of next season's events - not just start in the middle

I have managed to get some tone wheels so I will see if I can't sort some type of traction control


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## Karter2 (Nov 17, 2011)

Duncan said:


> I have managed to get some tone wheels so I will see if I can't sort some type of traction control


 ?? tone wheels ?? 

Galderdi.... I hope you are on high ground up there ?


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## Duncan (Dec 8, 2008)

Hi Karter
The Subaru suspension that I used had tone wheels on each corner - used for the ABS
When I put it together I had the really bad idea that I should just cut them off and throw them away - so I did

Now I'm having traction problems and I want new ones

The "plan" is to measure the speed of all four wheels and reduce throttle when the rear wheel speed starts to exceed the front wheel speed

Rather than the current situation when the first thing I know is the rear wheels smoke and I go sideways


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## galderdi (Nov 17, 2015)

Oh I wish true traction control was allowed in my sport. Along with all wheel drive and all wheel steer. Man o Man that would be fun. 

All good in my area. We did see a lot of water but it never threatened my property. There are still a few towns doing it tough. The volume of water was/is amazing.

I have reconstructed the car and it is running really smooth again. I also removed 1 degree from the front camber (from neg 3 to neg 2 degrees). I was surprised by how much more resistance to steering I now feel. I am really looking forward to beating them Porsches and Clubmans this Sunday.


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## galderdi (Nov 17, 2015)

Hi again,
The car is all ready for the next event. This one is the first Khanacross for 2017. I have been looking forward to this for many months. The car is very well suited to this format and the car is performing better than it ever has before. This is my best cahnce so far to show what it is really capable of.
The event will be at Willowbank on Sunday May 21.


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## galderdi (Nov 17, 2015)

I had a khanacross yesterday. I didn’t quite get the results I was hoping for yesterday. 
The car was fairly good but not quite the fastest on the day. I obviously still need to find a little more performance. I have a few ideas. I wasn’t far off the pace but I was aiming to be top three so being slightly down the leader board is a bit disappointing. I have a few ideas for some improvements to bridge the gap. 
Aero is one big consideration. Currently the car has a very flat nose so effectively I am pushing a lot of air in front of the car at speed. I think I will change the design to get the air flowing around the nose better. 
On this particular occasion the driver was an issue too. I had three significant issues that impacted my results. The first was as a result of running late for my turn I thought I was changing a setting to increase my power, but I was changing the wrong setting (reflection from the sun also didn’t help). So when I took off the power was woeful. The second was not noticing that my she was damp, which caused my foot to slip off the brake twice. That gave a few people a heart attack including me. Lastly I was just launching when I heard the time keeper say “Wait for it” I thought she was talking to me so I stopped. It turned out she was talking to someone else. That cost me about 2 seconds on that run. 
All in all though I am fairly happy as the car was solid and predictable, I just need to find about 5% to start winning.
The next one is a motorkhana on June 18 and then another khanacross July 19. 
Here are a few of the videos from the day:
https://www.youtube.com/watch?v=Kb_TR1vTK9M
https://www.youtube.com/watch?v=5QKFux4Py90
https://www.youtube.com/watch?v=0K4EeR4FK_Y
https://www.youtube.com/watch?v=pSW2TtCgI1s
https://www.youtube.com/watch?v=mITwJPNXGI8
https://www.youtube.com/watch?v=tJ7h19VpIfA


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## galderdi (Nov 17, 2015)

The results are in. I managed 20th from 42 on Sunday. That's not great on the surface but I literally lost 10 places with the brake slip alone. So with a few improvements (including the driver) I should see better results next time.


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## galderdi (Nov 17, 2015)

My next event is a motorkhana and is coming up soon. It will be held at Willowbank on June 18. IF anyone is local feel free to come and take a look. Spectators are free. I'll post another update after the event.


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## itchyback (May 28, 2014)

im interested, probably can come out after lunch. I'll pm you.


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## galderdi (Nov 17, 2015)

Excellent, I hope to see you there. Our events usually run till 3pm or so.


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## galderdi (Nov 17, 2015)

Darn you and your prank Itchyback.

The motorkhana was great although my results were less that stella. Half way through the day I noticed some unfamiliar faces watchign from the side lines. So I walked over and said "Are you Itchy?" As you can imagine I got some wierd looks in response to such a question. You must have been setting me up for that for a very long time Itchyback


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## galderdi (Nov 17, 2015)

I managed to get an extra set of springs working in the rear end. It took way longer than expected as I needed to make a second set of brackets to increase the clearance between the springs. I just managed to get it all done and on the trailer ready for Sunday.

The car started off fairly good and reasonably competitive. The extra rear springs made a noticeable difference by keeping pressure on the front wheels. But I started to sense something wrong in the steering in my second run. The attached link is the video from the 2nd run. If you look at the steering wheel you can actually see the angle changes even though I am travelling straight.

A couple of runs later it broke free and became virtually un-drivable. It turned out the mount that stops the steering rack from moving sideways had broken free. The friction from the other mount was insufficient to hold the rack so it was sliding sideways every time I turned the wheel. It made for some exciting driving.

In hindsight I should have gone back out and limped around for a couple more runs at half (aka safe) speed. That way I would have completed greater than 50% and my points would have counted. 

This is a 360 degree video, so move it around to choose you’re preferred angle. Watch the angle of the steering wheel change while driving straight (seems like almost 90 degrees)


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## galderdi (Nov 17, 2015)




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## galderdi (Nov 17, 2015)

Not quite sure what went wrong with the previous youtube post, but it won't even let me try to edit it/fix it.


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## galderdi (Nov 17, 2015)

I had another competition day yesterday. I was competing in round 4 of the Queensland Motorkhana Championship. 

Runs 3,5 & 7 are terrible, My fault not the car's. But those 3 out of 12 runs were enough to ruin my chances for the day. I finished mid field.

I 'll post a couple of the better videos shortly.


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## galderdi (Nov 17, 2015)




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## galderdi (Nov 17, 2015)




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## galderdi (Nov 17, 2015)

3 x 2nd places
2 x 3rd places
Out of 12 runs, shows that I can indeed drive and the car can be competitive but I just need to work on consistency. 

When I came 2nd or 3rd I was only around 0.1 - 0.3 secs behind the leaders.

11th outright after all that


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## Duncan (Dec 8, 2008)

The last two video's don't work

I suspect my problem is the 

_I can indeed drive and the car can be competitive 
_
Because I don't think I can!


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## galderdi (Nov 17, 2015)

Duncan said:


> The last two video's don't work
> 
> I suspect my problem is the
> 
> ...


 Yes, I think the method of embedding videos has been retired by Youtube. I am not sure if there are alternatives. But here are the links:

 
Runs 3,5 & 7 are terrible if you want to have a laugh. 
Runs 8,9,10,11 & 12 pretty good (12 is my favourite from the day)


2:https://www.youtube.com/watch?v=PDwdjfYKk5Q
3:https://www.youtube.com/watch?v=D8LrygHz0m4
4:https://www.youtube.com/watch?v=vvBsC7YJ1SM
5:https://www.youtube.com/watch?v=Fm-zKuxrKEs
6:https://www.youtube.com/watch?v=4F9nJ2t_HKs
7:https://www.youtube.com/watch?v=qQr4w1PMj3o
8:https://www.youtube.com/watch?v=mc1RuSsrd2I
9:https://www.youtube.com/watch?v=CZLO8vEBDFc
10:https://www.youtube.com/watch?v=0ENtvAPMcsE
11:https://www.youtube.com/watch?v=PEqGeqMG7Dc
12:https://www.youtube.com/watch?v=DGY1onXw8Vg

It has taken me over 10 years of regular competition to get to where I am from a skill point of view (not suggesting I am the best). But I was actually much more competitive in my $400 Pulsar. I think much of it is due to the steering. It is extremely difficult to drive well at speed when you working the wheel so hard. You can see what I mean from the videos. just watch how hard/fast my left arm has to work between the wheel and hydraulic handbrake. I did purchase a steering quickener but it's really too hard to install for the remaining couple of events so I will keep it for the new car.

I am getting more and more excited for the new car with every passing week. It will be awesome, although I am unsure about it's ability to perform handbrake turns.

My next event will hopefully be a khanacross on Aug 27th (assuming they have spots available)


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## galderdi (Nov 17, 2015)

I have entered for the Khanacross on Aug 27th. So far they have not pushed back regarding my EV competing against the Dinosaur Juiced vehicles. It will be held on the small circuit at the back of Lackside.I am really looking forward to this event as I haven't raced at that track before and it's being hosted by the Lotus club so there should be some interesting scalps to claim.


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## galderdi (Nov 17, 2015)

I had a ball at the Lotus Khanacross at lakeside. The track is quite tricky with a couple of blind corners. It really would help to have track time on this one. My first few runs were average at best but I did improve on my last few runs. I really struggled due to rear end grip. You know it’s bad when you are over steering in a front wheel drive car. I managed to come 34th from 66 competitors. That’s not bad considering the quality of the field. I beat 6 out of 13 Lotuses and 9 out of 16 Porsches. If I wasn’t retiring the car I could put better tyres on the rear and improve the rear geometry and I would be confident of picking up quite a few places. Overall I am quite happy. 

I had a problem with my camera and only got 1 video with telemetry. It’s not the fastest run and watch for the plover at about 1:22





 
https://www.youtube.com/watch?v=XXhOVGg55hI


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## Duncan (Dec 8, 2008)

I followed the youtube link
That looks great fun - love to see what the device would have done there!

I have an event coming up on the 30th Sept - I may see about some new tires for it


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## galderdi (Nov 17, 2015)

Duncan said:


> I followed the youtube link
> That looks great fun - love to see what the device would have done there!
> 
> I have an event coming up on the 30th Sept - I may see about some new tires for it


Yeah it was a real hoot. I can't wait to get back there. Hopefully with my new car. I would have actually been competitive if I had better rear suspention geometry and rear tyres. I would have been able to maintain much higher corner speed. I think I would have taken a couple of seconds off each run.

I definitely have another event on Sept 10. But I am also contemplating a hill climb on Sept 30. But I would need new rear tyres before I would commit.

Good luck with the tyres. What size do you run and what sort are you aiming for?


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## Duncan (Dec 8, 2008)

Hi galderdi

I have 215/45/17 tires at the moment - Dunlop LeMans LM 700 they are the ones that came with my Subaru and are probably at least 8 years old

I was going to ask one of the local motor-sports garages to supply me something that would work with my relatively light weight 

The biggest problem is getting past my innate Scottish nature and replacing tires that still have good tread on them 

What are your thoughts on low profiles - any advantages/disadvantages?


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## galderdi (Nov 17, 2015)

Tyre rubber only has a certain life. They begin to harden as soon as they are manufactured and the process continues for the life of the tyre. It is partly due to age and partly due to heat cycles. So if you can store your tyres in a cool, dark place they will last longer.

tread wear is only a good indicator for tyres being used regularly, resulting in the tread wearing quicker than the compond hardening.

You can use a product like Octopus Grip. Basically you paint it evenly over the trye surface and leave it to soak in. It makes the surface of the tyre stickier but only soaks in a couple of mm and probably only lasts for a single event. But it can be useful if you are at the end of the tyre's life but can't replace them just yet. 

As far as performance tyres go you really should change them every 3 years regardless of tread. Although over there you can probably stretch that another year because of the lower temps. 
Road tyres only have a life of 5-6 years.
Tyres used only on dirt are totally different as they are relying more on the tread and less on the compound so you can squeeze quite a few more years out of them.

Low profile are useless for motorsport. They do look great and sometimes they are necessary to get the correct rolling diameter on big wheels used to clear big brakes. But ideally, if you have the choice go for something like a 50 profile. The difference isn't the level of grip, that is determined by the width, tread and compound. The difference is signficant when you are exploring the boundaries of grip. Low profile will give way suddenly and will be more difficult to regather. Medium profile give you more feel around their grip limits, so you can feel them before they go and then rebound better once you catch them. I am sure there will be people that disagree but just take a look at almost all major motorsport teams and you'll struggle to find any running low profile tyres. 

I hope that makes sense.


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## Duncan (Dec 8, 2008)

Hi Galderdi

I'm on 215/45/17 tires and 7.5 x 17 rims

I kind of like the look of the 17's - I only NEED 15's for my brakes!

What would you recommend? - not 45's then, 

What do you mean by "medium" - 50, 55, 60, 65 ?

I LOVE the idea of something that would break away more gradually!


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## galderdi (Nov 17, 2015)

Duncan said:


> Hi Galderdi
> 
> I'm on 215/45/17 tires and 7.5 x 17 rims
> 
> ...


45s are perfect on 17 inch rims (IMHO) but it depends if you stick with those rims. 45s on 17 inch have a side wall of 3.8inch compared to my 205/50 R15 which have a side wall of 4 inches. I think anything in the 4 inch ball park is about right.


Use a calculator like this one to work it out https://tiresize.com/tyre-size-calculator/


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## galderdi (Nov 17, 2015)

Oh and also, just in case it becomes important. For some reason the profile for road tyres is provided as a percentage of the width. But for race tyres it is provided as the tyre diameter in mm......Totally different.
My slicks are 250/570 R15 which means the side walls are about 3.7 inches


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## galderdi (Nov 17, 2015)

I had a great event on Sunday. 

For a while the results were up in the air.....quite literally. We had a mini tornado which flattened our timing tents and associated equipment. The timing tents were thrown about despite being weighed down with concrete blocks. Our volunteers conducting the timing were shaken but unhurt. When I first looked over to understand the cause of the commotion I first thought a wayward car had somehow bowled over the time keepers. I am so glad that was not the case. A handful of timing result sheets were sucked up into the vortex and continued to rise almost straight up until they eventually reached sufficient height to become too distant to view.

But now the results are up in the cloud. So I can confirm I managed 6th place outright. That isn’t too bad, as usual one particular test cost me quite dearly but overall I think that only cost me one place realistically. Looking at the times I am confident all the improvements going into the new car will have me competitive against the guys at the top. I don’t expect to be consistently quicker than them as they will still have a significant size advantage. But I will be closing that gap to some degree and I will have other advantages that will somewhat compensate for the rest of the gap.

Here are a handful of videos from the day:
https://youtu.be/0WW2Wu9H7eA
https://youtu.be/lU-Li3Wa-Mo
https://youtu.be/U6m5F40kJJU
https://youtu.be/_Sh8p1PlSPs
https://youtu.be/LZOc9XA-aSQ
https://youtu.be/PXTGIv1CNE8


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