# DIY 6 wheel electric vehicle platform. Help please! and a build log... :P



## peggus (Feb 18, 2008)

Have you considered something like this?
http://www.evalbum.com/1609


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## Woodsmith (Jun 5, 2008)

Interesting.

How big is it?
What is the payload? People? Goods?
What is it's purpose?

The overall weight will be a more important factor then the payload I think.


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## Woodsmith (Jun 5, 2008)

peggus said:


> Have you considered something like this?
> http://www.evalbum.com/1609


I was also thinking along similar lines and found this
http://cgi.ebay.co.uk/Crayford-argo...emQQptZLH_DefaultDomain_3?hash=item2c53201706


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## JRP3 (Mar 7, 2008)

Did someone mention an electric 6 wheeler 
I don't think any of your motor choices will be big enough. I used a 7.5 inch diameter by 11 inch long 60 lb Yale forklift motor running at 48 volts, and I wouldn't use anything smaller. I'm using a 400 amp Alltrax controller.


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## Woodsmith (Jun 5, 2008)

Another thing to look for is a pair of forklift motors.
Some of the smaller forklifts, usually 24-48v and around 1.5ton, have two motors driving each drive wheel through a reduction gearbox. There was the drive axle from one on Ebay Uk recently, it went for less then £100.

You could chain drive from the wheel hub to your three wheels on each side and then have a seperate controller for each motor. There would be no worries about capacity then.

Just look out for forklifts being broken for parts and have the whole drive axle assembly and the control gear. You would still need a modern controller but the forklift would give you a lot of contactor and relays and a lot of large cables.


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## mleec321 (Feb 17, 2010)

Well, heres the thing. I need to use at a minimum, two motors. This is because one of the design requirements is that it must be able to turn in place. To achieve this, you would turn the right wheels forward, and the left wheels backwards. Or vise versa. Im not sure of another way to turn in place, without some strange transmission with one motor. 

So, all the right wheels would be linked together. 

All the left wheels would be linked together.

With this in mind, if I put one motor on EACH wheel, and each motor was was say.... 
http://cgi.ebay.com/ELECTRIC-SCOOTE...BDDSIC&otn=10&ps=63&clkid=7898007980344824841

I would have 6 horsepower total, in a 24v system, at 2200 RPM. 

So, for a 25 inch tire to go 15ish mph, it must spin at 210 RPM. To get the 2200 RPM motor to 210 RPM, it requires a 10x gear reduction. That means that the motors torque, is increased 10 fold. 

So for this motor, it would output 25 ft-lb of torque, max. However, it would do this at 34 amps max. And thats only for 1 motor. If I put 1 motor on each wheel, I would have a draw of 205 amps, max. This would be enough to kill a 12v battery pack fairly quickly, from my understanding....


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## mleec321 (Feb 17, 2010)

Oh, and the use for this vehicle is basically, its going to be a mini paintball tank. Dont laugh, its gonna be cool. And its not personally mine, its being designed for a client. However, im a mechanical engineer, and this electrical business is throwing me for a loop 

Its function is going to be to carry one person around a field at a very low speed, for as long as possible.


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## JRP3 (Mar 7, 2008)

mleec321 said:


> To achieve this, you would turn the right wheels forward, and the left wheels backwards. Or vise versa. Im not sure of another way to turn in place, without some strange transmission with one motor.


Actually, the T-20 transmission in my Attex, also used in Max 6 wheelers and others, can be setup to shift independently, and can reverse one side while in forward on the other. It's essentially two transmissions in one.



> So for this motor, it would output 25 ft-lb of torque, max. However, it would do this at 34 amps max. And thats only for 1 motor. If I put 1 motor on each wheel, I would have a draw of 205 amps, max. This would be enough to kill a 12v battery pack fairly quickly, from my understanding....


No matter what motors you use, the vehicle will still use a certain amount of power to move. My 48 volt x 400 amp setup will almost stall the motor when climbing my steep hill with a trailer full of about 400 lbs of stone, total vehicle/trailer payload weight around 1100 lbs. If you're only going to be on the flat you could get by with less of course.


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## JRP3 (Mar 7, 2008)

mleec321 said:


> Oh, and the use for this vehicle is basically, its going to be a mini paintball tank. Dont laugh, its gonna be cool. And its not personally mine, its being designed for a client. However, im a mechanical engineer, and this electrical business is throwing me for a loop
> 
> Its function is going to be to carry one person around a field at a very low speed, for as long as possible.


I see, in that case you could use a smaller motor, or two. The problem with two is controlling them and having them reversible becomes more complicated.


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## mleec321 (Feb 17, 2010)

JRP3 said:


> I see, in that case you could use a smaller motor, or two. The problem with two is controlling them and having them reversible becomes more complicated.



Lol! We seem to be posting over top of eachother. So yes, the goal is to carry one person around, BUT, inherently this vehicle is going to be heavy. 

-The 'armor' is consisting of 5 mil corrugated plastic. This in itself if very light, but it will have a light steel framework to support it.

-Power source will be heavy. Car batteries are around 30-40 lbs each? I was thinking, if it were a 24v system, to have 4 car batteries, two for each set of 3 wheels. If the 4 car batteries doesnt work, then 8 car batteries, 4 for each side. (4 batteries, 120 lbs. 8 batteries, 240 lbs)

-Driver. The client is a bigger man, at around 240 lbs

- The motors will be heavy. For those motors I linked, the shipping is for 10 lbs. So if I went with 4 motors, that would be another 40 lbs.

- Batterys + driver+motors= 520 lbs alone, minimum!


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## mleec321 (Feb 17, 2010)

So, with these requirements in mind, what motor do you think I could get away with? Do you think that 1 hp motor would work? I could put a total of 2 motors on each side, on the front and back wheel of each side.

Thoughts?


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## JRP3 (Mar 7, 2008)

The 1 hp scooter motor might work if you had 4 of them, but it says it's "non reversible".


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## Woodsmith (Jun 5, 2008)

For what you are planning I would forget small bike motors.

For it to be any fun at all on a paintball site it will need power to get across rough terrain and climb slopes all at a reasonable speed.

I would get the fork lift twin motor arrangement I described earlier. It means that you have ample power, motors that can be reversed, the main gear reduction built in so you you only need two and not six gear/chain reductions.

Even if you only used one controller to save money you can still reverse the motors with contactors so that as you apply throttle the motors spin in opposite directions.
the contactors can give motor on, motor off and motor reverse on each side that will give you some variable steering.

Oh, also forget car batteries, you will kill them on about second outing if not first. Fine to have one to see if your motor works before buying it but you should get deep cycle batteries. LiFePO4 (lithium) may be a bit costly but it will save a lot of weight.


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## AmpEater (Mar 10, 2008)

For your application I would stick to PM motors, as they "want" to maintain a certain speed at a given voltage, and will draw more or less current as required to do so. Since you need both your motors to turn at exactly the same speed to move in a straight line, I feel like a set of PM motors would behave more predictably than a set of series motors, especially when turning, and even moreso turning while moving forward at speed. (just a gut feeling)

Also much easier to reverse.

Also, personally, I would want very strong regen in a vehicle I was going to be driving up and down steep inclines. This way you could have a single throttle/joystick/whatever for accel and braking, which in my mind is much more suited to off-road use. Rock buggies have special control panels to allow the brakes and throttle to be operated by hand, mainly to deal with the limitations of ICE drivelines, though, in my mind. (hi-torque electric hub motors would totally blow that whole crowd away)

If you go chain drive, you can get your primary gear reduction, and power transmission all in one. 

This is a blatant ad, but I was planning a similar project at one point, and I have some parts that might be perfect for you;

A matched pair of Leeson 6.5hp 48v permenant magnet motors I could part with. They are around 35-40lbs each. Both new in box, never run. I've seen reports of [email protected] continuous, which is around 20hp.

Also, a set of etek PM motors. Something like 8hp cont, 20+ peak. Only 22lbs or so each (!). Good for around [email protected] continuous, perhaps a bit more. Also NIB.


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## mleec321 (Feb 17, 2010)

AmpEater said:


> For your application I would stick to PM motors, as they "want" to maintain a certain speed at a given voltage, and will draw more or less current as required to do so. Since you need both your motors to turn at exactly the same speed to move in a straight line, I feel like a set of PM motors would behave more predictably than a set of series motors, especially when turning, and even moreso turning while moving forward at speed. (just a gut feeling)
> 
> Also much easier to reverse.
> 
> ...



Pm sent m8. Let me know!


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## mleec321 (Feb 17, 2010)

Well, if I went with a large forklift motor, I would need a large battery pack. Thats kinda why I was interested in smaller motors. 

But, I used to race electrathon cars. We used an etek motor, on a 24v setup with 2 optima red top batteries. We would race these things as far as possible, for one hour. Granted, these were very efficient vehicles, with 3 20" wheels. (Picture attached for those who dont know electrathon) But also, these vehicles went way faster then I want to go. So my thought is that I can trade speed for high torque, and keep the same battery life. 

As far as power is concerned. I guess the vehicle would operate for about an hour, then go back to be recharged. Another potential option, is to have a small generator onboard. This could recharge the batteries continuously during operation. 

Thoughts?


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## Woodsmith (Jun 5, 2008)

Unless your paintball gaming is on a carpark I would worry about its ability in the rough if there isn't enough torque and power from the motors. Granted you can gear it down but then it get really slow. Unless you make it really light weight, aluminium chassis and lithium cells.

Have you looked at Agni motors?
Higher voltage but efficent.


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## JRP3 (Mar 7, 2008)

The vehicle will take a certain amount of power to move it no matter what the motor. A higher voltage motor will probably be more efficient since you'll draw fewer amps to get the same power. For comparison, a 24 volt setup might run two 100 amp hour batteries while a 48 volt setup could run four 50 amp hour batteries, both setups have 2400 watt hours. To produce the same power the 24 volt setup will have to draw twice as many amps as the 48 volt.
I think adding a generator in something that small is a waste, plus it will be hard to fit everything.


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## Zanthic (Jul 2, 2008)

I designed the electronics and communication protocol for the following vehicle
http://zanthic.com/project4.htm
It was quite a while ago but you might get some ideas for the suspension system, that part worked well!


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## gor (Nov 25, 2009)

mleec321 said:


> Well, heres the thing. I need to use at a minimum, two motors. This is because one of the design requirements is that it must be able to turn in place. To achieve this, you would turn the right wheels forward, and the left wheels backwards. Or vise versa. Im not sure of another way to turn in place, without some strange transmission with one motor.
> 
> So, all the right wheels would be linked together.
> 
> ...


 


mleec321 said:


> Lol! We seem to be posting over top of eachother. So yes, the goal is to carry one person around, BUT, inherently this vehicle is going to be heavy.
> 
> -The 'armor' is consisting of 5 mil corrugated plastic. This in itself if very light, but it will have a light steel framework to support it.
> 
> ...


providing your 6-wheeler would weight like light motorcycle, ~320lbs+180 lb rider weight = 500lbs; - to move it 45 degree uphill (outroad application) it would require 380 ft lbs of torgue - more than ten of 25 ft lb motors mentioned above (providing none of wheels would loose traction);
gearing it down (say twice) - from 1:10 to 1:20 would deliver necessary torque, but reduce speed accordingly (from ~15 mph to 7.5)


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## JRP3 (Mar 7, 2008)

Something doesn't sound right with your math. My 7.5 inch motor has a max of maybe 20 hp, I'm geared 16:1, the vehicle weighs about 700lbs, and I can go up a 30 degree hill with a trailer full of about 400lbs of stone.


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