# 1962 C10 Drag truck



## major (Apr 4, 2008)

Pay a visit to NEDRA.com and/or Facebook or their yahoo group discussion list. John Metric is their current president and member here under that username. Check out his posts. Some good data from some of the quickest passes. He also sells drag race batteries. See lonestarracing.com or something like that.

major


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## Duncan (Dec 8, 2008)

Hi
a 200 mile range and an 8.5 in the 1/4 are not mutually compatible

You can have a light weight drag machine - or you can have 200 miles

If you can live with 50 miles then the 1/4 miles is doable - maybe have a pallet of batteries that goes on the bed when you need 200 miles


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## 62Farmtruck (Sep 4, 2017)

Correct me if I am wrong but energy storage is the main issue. A 200mile range requires a lot of energy storage and I have to assume 8.5x in the quarter at 3100lbs requires a lot of energy storage as well. I can't yet speak to how much energy is needed for both but I'm also not planning to drive 200 miles then click off an 8.5x pass. They need to be thought of as two different scenerio.

Take the truck on light throttle cruises equalling 200 miles.

Tow to the track and click off 8.5x passes. How many, don't know. I have to assume I would be using my generator to top off the battery between rounds.

One customer of mine is working on a 50kwh battery for EV busses.

Another uses Sevcon gen 4 size 6 controllers in their EV.

I work with Tesla, Nio, Zero Motorcycles, Joby Aviation to name a few. Hoping to discuss some things with their EE's that I know.

I'm not afraid of putting a heavy battery in the truck. I figure I have 800-900lbs of EV drivetrain to net me back at my current 3100lb race weight.


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## Duncan (Dec 8, 2008)

Hi
You would be surprised at how little your drag racing will take

Say 160 mph - 70 m/sec - and 1500Kg that is 3,700,000 Joules or just over 1kWh in kinetic energy

It will take more than that - but probably only about twice as much

You are using a LOT of power - but only for 8 seconds!

Run it the other way around 1000 rwhp - call it 1000 Kw electrical for 8.5 seconds = 2.36 kWh

But you won't be using your 1000 kW for the whole period - you will be using more power as the speed rises - so if 1000 kW is the peak power then the average power is more like 500 kW


But your 200 miles will be about 80 kWh - 40 times as much!

I'm nowhere near as fast as that but I do have over 500 Hp in my 900Kg "Device"
After a day with four 1/8th mile runs I have used up less than 10% of my 14 kWh battery


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## major (Apr 4, 2008)

62Farmtruck said:


> Correct me if I am wrong but energy storage is the main issue. ...


Main issue for drag race is force / mass.

Main issue for range is energy stored / efficiency.



Duncan said:


> a 200 mile range and an 8.5 in the 1/4 are not mutually compatible


I agree with Dunc given today's battery technology and any limit on budget.

Just the way I'd call it.

major


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## brian_ (Feb 7, 2017)

Duncan said:


> You would be surprised at how little your drag racing will take
> 
> Say 160 mph - 70 m/sec - and 1500Kg that is 3,700,000 Joules or just over 1kWh in kinetic energy
> 
> ...


This completely ignores the energy required to overcome rolling drag and aero drag; that might be a reasonable starting assumption.

Unfortunately, I don't think the overall efficiency (including the driven tires) will be anywhere near as high as 50% at this high power level.



Duncan said:


> But you won't be using your 1000 kW for the whole period - you will be using more power as the speed rises - so if 1000 kW is the peak power then the average power is more like 500 kW


If the truck really uses 2 kW-h (7.2 MJ) in 8 seconds, that's 900 kW... _average_.


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## brian_ (Feb 7, 2017)

Duncan said:


> I'm nowhere near as fast as that but I do have over 500 Hp in my 900Kg "Device"
> After a day with four 1/8th mile runs I have used up less than 10% of my 14 kWh battery


That's a good baseline.

Now double the mass, double the power, but more importantly double the drag distance for much more than double the energy consumption, and that's a lot more energy... but still less than would be needed for cruising the desired distance.


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## brian_ (Feb 7, 2017)

62Farmtruck said:


> First thought was all wheel drive as some of the events I run are no prep races so traction is limited. If I went this route, I am thinking 2 motors up front, one for each wheel through a CV shaft. Perhaps a single Sevcon controller (or similar) could drive both? Then for the rear, do I go through my existing ford 9" rear with a dual motor set up? Not sure a single controller would be enough here.


It sounds like the plan is for brushed DC motors. One controller may be able to drive both left and right front motors, but when one unloads more than the other (due to the truck's reaction to driveline torque to the rear) this sounds like an issue, as the unloaded tire loses traction and spins.

There are AC motor controllers which are intended to drive two mechanically separate motors on the same axle, which would be suitable for the front.

There is also the issue of coordinating the front and rear, so you're not spinning one end when traction is still available to drive harder at the other end.



62Farmtruck said:


> For street driving I am thinking to have only 1 motor on for light cruise so this may require splitting the front motors using 2 controllers. IE kill the rear and 1 front motor by a couple switches wired through a relay to turn a signal wire off to the contrioller(s). Isolating front and rear would also be good for the burn out box at the track.


I understand the benefit of being able to switch front and rear off independently, but for street driving I don't see any benefit to switching anything off. Unless you use something like locking hubs, all the same mechanical parts will still be spinning, so there is no reduction in mechanical drag. Distributing drive force among fewer motors just means each takes more power.

I certainly wouldn't want to run only one of two front motors; the steering reaction would be unpleasant.


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## brian_ (Feb 7, 2017)

major said:


> Main issue for drag race is force / mass.
> 
> Main issue for range is energy stored / efficiency.


Taking that a step further, force multiplied by speed is power, which is the real issue for the battery when racing.

A bigger battery is better for both energy stored and peak power, but for a given size the battery deign which stores the most energy is not likely the battery design which can deliver the highest power.

Maybe one approach would be to design to handle the drag power (because drag performance is going to be sensitive to mass), and see how much range that provides... it might be enough.


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## major (Apr 4, 2008)

brian_ said:


> Taking that a step further, force multiplied by speed is power, which is the real issue for the battery when racing.


The real issue is force. Power is a consequence.



brian_ said:


> A bigger battery is better for both energy stored and peak power, but for a given size the battery deign which stores the most energy is not likely the battery design which can deliver the highest power.
> 
> Maybe one approach would be to design to handle the drag power (because drag performance is going to be sensitive to mass), and see how much range that provides... it might be enough.


The ideal battery (EESS, electric energy storage system, could be a capacitor) would be depleted or zero SoC, at 1321 feet. That way you carry no unnecessary mass down the track. There are batteries getting to, or near, 200C. That's an 18 second complete discharge. Even at lower discharge, or easy driving, I don't think he'll see 800 times the 1/4 mile range with an EESS capable of 8.5s in a truck.

Regards,

major


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## brian_ (Feb 7, 2017)

major said:


> The real issue is force. Power is a consequence.


How much power is needed is determined by the force required to accelerate the vehicle, the speed, the efficiency of the mechanical and electrical systems, etc. How that power demand is calculated is important, but in the end irrelevant *to the battery*. 

The force applied to the vehicle, and even the resulting acceleration, are of no consequence to the battery - it must supply power. So calculate the power and put the rest of the dynamic data away for the remainder of the battery selection process.

The battery doesn't care if the power from it is accelerating the truck down the quarter mile or churning through a mud bog - it just delivers electrical power.


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## major (Apr 4, 2008)

brian_ said:


> ... irrelevant *to the battery*.
> 
> ...


Deja vu!

http://www.diyelectriccar.com/forums/showthread.php?t=36904

But let's not hijack his thread.

major


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## brian_ (Feb 7, 2017)

major said:


> Deja vu!
> 
> http://www.diyelectriccar.com/forums/showthread.php?t=36904
> 
> But let's not highjack his thread.


I'm not highjacking (or hijacking) anything... my comments are entirely about sizing a battery for the desired drag race / street truck.

The linked thread was about the importance of one value out of context. It would be nonsense to consider only voltage or only current output capacity when sizing a battery; you need to consider the combination. You don't need to know what that power is being used for: you can put the 1,000 kW into a fast low-torque motor with lots of reduction gearing, a slow high-torque motor with taller gearing - or a really huge toaster if you want - the battery doesn't care.

For most EV builders, the capacity of the required battery is reasonably straightforward: estimate energy consumption per unit distance (e.g. 360 W-h/mile), multiply by range (e.g. 50 miles), and you have required capacity (24 kW-h). In this example, a salvaged Nissan Leaf pack (rearranged as appropriate to the desired operating voltage) would match nicely.

For a drag racer of this performance level, that approach might not work. Four passes might need only 8 kW-h, or one-third of that Leaf pack. A Leaf pack contains 48 modules in series, so a one-third pack could simply be 16 modules in series, nominally running at 120 volts (perhaps suitable for the motor). Although containing more energy than required for a couple of 1/4 mile passes, this set of 16 modules is designed to deliver up to 27 kW (225 amps at 120 volts) in the car for which they are designed... but you briefly need over 30 times that much power. Aside from the interconnections between cells probably behaving more like fuses than wires at 8,000 amps, can the cells themselves handle that, even for a few seconds? The Leaf cells are not the 800C rate type mentioned.

It seems inevitable that the battery size and design is going to be driven by the power requirement, and the configuration (how many cells in series and parallel) will be driven by matching the voltage and current requirements of the motor. If cells designed for very high discharge rate (compared to their capacity) are used and the system is sized just big enough for sufficient power, it might not be able to store enough energy for acceptable range.

To put things in perspective, we're talking about a power level which is higher than that of a Tesla Model S Performance model in Ludicrous mode. The Tesla can only get that power level from the battery for a short duration, the power is limited by the battery, and this is an enormous 90 kW-h or 100 kW-h battery.


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## major (Apr 4, 2008)

http://www.ampahaulic.com

Here's the link to John Metric's website. I had it wrong in post#2. Click on batteries there up top of the homepage.

You'll need something like the sleeper-cell or better to get a force/mass ratio to enable an 8.5. 

Just my opinion.

major


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## Karter2 (Nov 17, 2011)

8.5 sec qtr is a serious performance vehicle, and i would suspect you dont want to compromise that potential on the track by hauling an extra few hundred pounds of unneccessary battery up the strip.
Consider a dedicated "race" pack (talk to J Metric) , and a bigger removeable "road" pack of suitable capacity for the trip, that can be left in the pits together with all the other gear that you dont keep in for runs.
Dont forget you are going to need chargers, generators etc , as well.


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## dain254 (Oct 8, 2015)

I believe there is a way to get your 8.5s and 200 mile range pickup. 

Step 1: Buy Tesla P100D
Step 2: cut everything off of Tesla until it is a bare chassis
Step 3: meticulously reproduce your 62' pickup body into a 1 piece carbon fiber shell that weighs no more than 100lbs - shaving all joints and smoothing corners so as to increase it's aero efficiency
Step 4: Bungee/Zip tie truck body to Tesla Chassis, run 8's


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## wightsparks (Aug 21, 2017)

This makes me feel sorry for the guys with the years of experience, buckets of cash, blood, sweat and tears in their souped up motors.

https://www.youtube.com/watch?v=ARzujfRiQ3c


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## brian_ (Feb 7, 2017)

dain254 said:


> I believe there is a way to get your 8.5s and 200 mile range pickup.
> 
> Step 1: Buy Tesla P100D
> Step 2: cut everything off of Tesla until it is a bare chassis
> ...




But seriously, the Tesla structure is a unibody, so if you cut the roof off it isn't a driveable vehicle - the often-shown "skateboard" is just a collection of parts which can't hold up a load (the battery case has strength, but is not the frame). An 8.5-second drag truck requires a roll cage anyway, so Step 2 would need to be:

"build a truck-shaped tube frame and move all of the Telsa parts to it"
With any luck, that would save enough weight to bring the P100D quarter mile down enough from 10.44 @ 124.21 mph. Of course, one could forget the truck and just race the Model S, but even stripping the interior and replacing some panels with lighter composites doesn't look like it will make that light enough.

I think more-than-P100D power will be needed for the 8-second truck, but maybe just keeping the mass down will do it. Aero is a challenge, though...


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## 62Farmtruck (Sep 4, 2017)

In all fairness and no disrespect meacted here, but those of you that talking about cutting things up, concerned about the possibility of 200lbs additional in battery weight; how many of you have built a 10 second vehicle regardless of how it is powered? Now, how many of you have built something from the ground up that runs consistent 9.2x at 3,120lbs with the aerodynamics of a billboard wearing a construction hat? I have, not EV, but I get the weight/power needed to do it.

200lbs is +/- 0.2

Again, I have 800-900lbs to take out with the current ICE set up. If I added that amount back in, I would need to make an equivalent 800ftbs/1000rwhp. But, I am banking on a higher tq output and less hp could do it too. Explosive energy to the 330' makes up for lack of MPH in the 1/4.

My mph for 9.20 is considered off or slow. But that is because I focused on 60'


My goal may be lofty, but instead of picking it apart, let's figure out what needs to be done to make it happen...


For those of you that have provided positive and real input (you know who you are) THANK YOU.


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## 62Farmtruck (Sep 4, 2017)

BTW, the truck is a chrome alloy back half with full CM cage wearing an NHRA chassis cert. Cutting chassis up mean lots of work to get it legal again.


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## brian_ (Feb 7, 2017)

62Farmtruck said:


> My goal may be lofty, but instead of picking it apart, let's figure out what needs to be done to make it happen...


I'm not picking anything apart... except the idea that a Tesla Model S "skateboard" includes a chassis structure - it doesn't.

The Tesla chatter might seem irrelevant, but it's not. It's always helpful to have some benchmark for comparison, and the idea here is to assemble a vehicle which can turn a 1/4 mile time which turns out to be significantly faster than the fastest Tesla. If the truck has Tesla-like power (which is close to the truck's gas engine - lower peak power but broader power band), it is depending on being substantially lighter to be faster. To be lighter, it will need to have a reasonably light structure (which I assume it does) and a smaller battery... despite the need for massive power.


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## brian_ (Feb 7, 2017)

62Farmtruck said:


> BTW, the truck is a chrome alloy back half with full CM cage wearing an NHRA chassis cert. Cutting chassis up mean lots of work to get it legal again.


I'm guessing this is one reason for wanting to use the existing rear axle, rather than adapting it to an independent setup (which would allow using a production EV motor - the higher-output of the available Tesla Model S rear motors is actually a possible choice).

Whether the gearing is suitable depends on what motor you choose, and what speed it needs to reach. Too tall and you'll bog down at the start with inadequate torque to the wheels; too short and you'll hit the motor speed limit before the end of the 1/4 mile. And then there's the question of whether you run a single ratio or a two-speed transmission.

What trap speed are you expecting with the 8.50 ET?


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## 62Farmtruck (Sep 4, 2017)

Brian, my comment wasn't directed at you 8>) 


Let's figure it out with what I have. 


First thing we need to know:

1) How much the truck will weigh?

Let's assume the same race weight as it does with the current ICE set up. 3120lbs with me in it



2) How much power is needed? 

At 850ish rwhp and 700rwtq it went 9.20 at 144mph with a 1.35 60' there was a bit more in it as the torque conventer was a bit too loose on the bigger N20 hit.

I think an honest 1000rwtq with 1000rwhp would move the truck to an 8.50.


3) What drive train would net me that power level?

I'd like to do it as AWD.



Thanks again.


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## 62Farmtruck (Sep 4, 2017)

Brian, we were both typing at the same time. 

I to go 8.50 I likely need to be in the 161-163mph range.

A little further up I talk about gear ratio and motor rpm.


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## 62Farmtruck (Sep 4, 2017)

First link is my truck at a no prep 1/8 mile race call Eagle Field Drags.

Second is in Sacramento cutting a 1.35 60' on one of my smaller N20 tune ups running 9.4x at 138mph.

Third video is after a gear / tire change and tightening of the converter. 9.24 @ 144man on the same tune up.

Fourth is just to give you guys an idea of the chassis. I am planning on finishing the front frame / suspension in round CM to match the back. This will likely shave another 100lbs. I also need to do some work on the doors, removing the regulators and going lexar. Aprox another 75lbs there.

https://youtu.be/z_ax5cUON14

https://youtu.be/tOpRPmFJbGo

https://youtu.be/WhADFbXN4u4

https://youtu.be/00K37II7wW0


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## brian_ (Feb 7, 2017)

62Farmtruck said:


> My math tells me my current 3.90 gear coupled with a 30" tire and 7,000rpm would net me 160mph which should be just enough mph. 5,000rpm if I put a 2.73 gear in it.


Ah, yes... I forgot the trap speed and tire diameter were in the first post!

Those are low speeds by the standards of modern EV motors, but perhaps reasonable for brushed DC motors - time for someone who has pushed these motors hard for short runs to comment on what part of that speed range will be the low-speed/constant-torque portion, and how sharply the power will drop off above that point.


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## Karter2 (Nov 17, 2011)

62Farmtruck said:


> In all fairness and no disrespect meacted here, but those of you that talking about cutting things up, concerned about the possibility of 200lbs additional in battery weight; how many of you have built a 10 second vehicle regardless of how it is powered? .
> 
> 200lbs is +/- 0.2
> 
> For those of you that have provided positive and real input (you know who you are) THANK YOU.


 No offence taken , and none intended.
I respect your experience on the track , but a few educated questions..
Why do you dismiss "a few hundred pounds of battery" but at the same time intend to rework/re-engineer the front chassis , lexan etc etc, ..
....to save 75+100lb ?
In reality, the difference between a 200mile battery pack (80+kwh) and a dedicated 1/4 mile race pack may well be over 1000lb !
Would that be worth considering ?
Likewise , All wheel drive is going to add several hundred pounds..or more !
Finally, is your figure of 1000rwtq ...actually " rear wheel torque" ? (lbft ?)
If so, something is not right...
A standard Tesla has nearly 10 times that torque


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## 62Farmtruck (Sep 4, 2017)

If an 80kwh battery is needed to go 200 miles, and weigh 1,000lbs then I may need to rethink things a little 8>)

I doubt a Tesla make an average of 10x 1,000 rear wheel tq. My truck makes an honest 700 ftlbs at the rear tire at 6,000rpm and 850 hp at the rear tire at 7,200 rpm. I have a ton of dyno sheets at different power levels and time slips to go with them. If a tesla make 10k ftlbs tq at the tires, that would be more than top fuel power. I'd love to see an AWD dyno sheet from a Tesla.


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## brian_ (Feb 7, 2017)

To cover a quarter mile in 8.5 seconds requires an average acceleration over one g (more than the acceleration of gravity - 9.81 m/s2 or 32 ft/s2), so the average force on the vehicle by the tires will be greater than the vehicle's weight. Actual acceleration will be greater at the beginning because the vehicle won't have enough power to maintain constant acceleration for the entire run (almost 15,000 kW or 20,000 HP for a 3100 pound vehicle!), so it must accelerate substantially harder at the beginning.

Just one g of acceleration of a 3100 pound vehicle with 30" diameter tires (1.25 ft radius) requires 3875 lb-ft of torque split between the driven tires (simply the driving force multiplied by the tire radius).

6,000 rpm and 7,200 rpm are clearly not wheel speeds - they would correspond to 536 mph and 642 mph!

The 700 lb-ft torque is presumably calculated at the driveshaft or engine output. That would correspond to 2730 lb-ft at the axles, and make sense in combination with 6,000 rpm (an engine speed, or transmission output speed in a high gear)... still not enough, but close.

700 lb-ft @ 6,000 rpm is 800 HP, which is consistent with the other dyno values. 850 hp @ 7,200 rpm is 620 lb-ft... at the shaft which is turning 7,200 rpm. If that's at the transmission output, or at the engine and the transmission is in a 1:1 top gear, that would correspond to 2,418 lb-ft at the wheels.

I think the problem is just that the dyno people are measuring output at the rear wheels, and calculating what the corresponding torque would be at the speed of other points in the powertrain... although of course the actual torque is higher at those points, with some power being lost in gears and tires (and a tiny bit in bearings).


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## brian_ (Feb 7, 2017)

All the recent Tesla Model S performance data is for the all-wheel-drive ("dual motor" in Tesla-speak) models, but a now "old" P85 motor put out 443 lb-ft... and put it into a fixed-ratio gearbox, which I think is a 9.73:1 reduction for that model (the "big motor" RWD). That's 4310 lb-ft to the axle shafts. The "performance" dual-motor models put at least that out the rear, plus a smaller amount to the front.

You really do need thousands of pound-feet of torque to the tires to make a ton or two of vehicle accelerate at the rates we're discussing... and the truck is doing that now with the gas engine.


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## brian_ (Feb 7, 2017)

62Farmtruck said:


> I'd love to see an AWD dyno sheet from a Tesla.


They're out there. As the only widely available pure-electric (battery only, not hybrid) high-performance electric vehicle, the Tesla Model S has seen an enormous amount of acceleration testing, dyno study, and analysis. It's almost all about acceleration (rather than cornering, response, or braking), but that should match the interests of a drag racer. 

An old example is available from Drag Times:
http://www.dragtimes.com/images_dyno/27143-2015-Tesla-Model-S-Dyno.jpg
Note that the torque is clearly labelled as "ENG" (meaning at the engine output, not the wheels), even though the measurement is at the tires. I don't know why the torque takes so long to rise in that test - it makes me wonder about the test method. Anyway, there are lots more to be found in an internet search.

One thing to watch for if searching for Tesla performance data is a lot of it is what the car itself monitors and records. That's all great, but it's not externally measured output.


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## Karter2 (Nov 17, 2011)

Yes Brian, there are many reported dyno tests of the Tesla showing 540 bhp and 920-950 ftlbs torque "at the wheels" , with coresponding rpm of 3000.
They are clearly rubbish (but one at least showed "motor" figures)
We know the 3000rpm peak is a motor speed and with Teslas 9.7:1 drive reduction, that would results in 310 rpm at the wheels, which would mean over 9000 ftlbs at the wheels.....admittedly above that speed the torque drops away.
But you get the general picture..a lot of torque !
And yes, it seems like many dyno jockeys dont understand what they are seeing.


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## 62Farmtruck (Sep 4, 2017)

Correct me if I am wrong, but a dyno jet drum weighs 2,500lbs. Rwtq is measured by the dynojet based on time it takes to accelerate said drum. 

My pulls are made in high gear which is a 1:1 other than rear gear and tire size. 

My experience on the dyno tells me rotating weight of the rear tires/wheels and tires construction (bias vs radial) will also skew the numbers seem.

But on a dynojet, it reports 850rwhp at 7,200band 700ftlbs at 6,000. Yes, I can easily do the math tq * rpm/ 5252 = hp.

So, for me, on the same dyno, I need to make 1000rwhp and 1000rwtq to go 8.5x at 160mph at 3120lbs.


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## Karter2 (Nov 17, 2011)

But you cannot ignor the rear gear for measuring torque.
As brian said , with a 3.9 rear your 700ftlbs is actually 2730 ftlbs at the wheels.
Thats just the way gearing works with torque ( but not hp !)
Tyre size wont change the torque available, but it would have to be calibrated into the dyno to get an accurate result
RRDyno results are quoted as "at the wheel" figures, only because that is how they are measured..litterally at the wheels. Whilst the hp result can be adjusted to "flywheel" hp , by allowing for some efficiency losses on the transmission, flywheel Torque has to be calculated by allowing for gearing as well as frictional losses.


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## 62Farmtruck (Sep 4, 2017)

You do not input gearing figures in to the dyno. It does not know what gear sets it is seeing. Numbers are based off accelerating the drum. Going from a 3.90 to a 4.22 to a 4.88 gear dyno numbers very little. 

I understand torque multiplication of gearing in both Trans and rear. Heck, the converter also multiplies torque prior to it coupling. You can often see unrealistic torque spike with a loose converter as rpm flashes prior to coupling, it does settle down. One reason I pull up to roughly 60mph on the dyno before I hit it. 

Again, on the same dyno, I need to make 1000rwtq average power band to go 8.50. We must use the same tool to measure.


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## Karter2 (Nov 17, 2011)

62Farmtruck said:


> You do not input gearing figures in to the dyno. It does not know what gear sets it is seeing.


 It wii know the gearing if you input motor rpm.
Which i guess you have as you quoted them with the hp figs.

Have you any direct data on what your engine torque is ?
Engine dyno graphs maybe ?


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## 62Farmtruck (Sep 4, 2017)

Dyno pulls rpm via spark plug wire. But, it doesn't know if you are in a 1:1 Trans gear, doesn't know if you have a 2.73 gear with a 22" tire or a 4.88 with a 33" tire. It simply looks at how fast you accelerate the 2,500lb drum.

All my dyno sheets are on the computer at the shop I tune at. I am sure I can get a screen shot. But I am not so sure how helpful they will be as the instant I stand on it, rpm goes from 3,500ish to 6,200rpm because the converter slips (purposely). Once it couples at 6,200 it pulls to 7,200 very quickly. 

I guess we could look at the time it took to accelerate the drum and try to work that backwards ending up with a required motor output .


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## major (Apr 4, 2008)

62Farmtruck said:


> Dyno pulls rpm via spark plug wire. But, it doesn't know if you are in a 1:1 Trans gear, doesn't know if you have a 2.73 gear with a 22" tire or a 4.88 with a 33" tire. It simply looks at how fast you accelerate the 2,500lb drum.
> ...


The dyno has the engine RPM and the drum RPM so doesn't need gear or tire info. It has the ratio and uses it to transform drum torque to engine torque. And the chassis dynos I've had experience with used a torque arm with load cell for drum torque measurement. 

All this really gets back to what I called the real issue: force, or tractive force.

You were looking for info on Tesla so perhaps this attachment will help.

Regards,

major


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## 62Farmtruck (Sep 4, 2017)

Thanks for the attachment, it confirms some math I did on my end. 

I need to look at my current average power used to get my truck down the track, meaning I am always in the 6,200-7,200 rpm range the minute I let go of the trans brake button. 

The average power to the tires in that rpm range needs to be equaled by the EV motor(s) from 0 rpm to max rpm. To go faster at the same weight I need more average power.

Rough number for current average power is 660ftlbs / 838hp.


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## brian_ (Feb 7, 2017)

62Farmtruck said:


> Correct me if I am wrong, but a dyno jet drum weighs 2,500lbs. Rwtq is measured by the dynojet based on time it takes to accelerate said drum.


The Dynojet measures the rate of angular acceleration of a rotating mass of known inertia. If it is really based on the time to a specific speed, it is measuring the time to deliver a set amount of energy, which is power by definition. This is the easiest possible form of power measurement device to build.

This machine doesn't measure torque anywhere. It calculates the torque from the power, using whatever speed is indicated by the spark frequency... so it is calculating what the torque output of the engine (or transmission because it is in a 1:1 gear) would be if there were no gear or other losses.

"Rwtq" isn't a physical quantity, or a unit of measurement. The way you're using it here, it means the torque which would correspond to the power transmitted by the rear tires but at the engine speed, in units of lbf-ft.

The test method is not really suitable to determine engine performance under anything but brief and accelerating conditions, but that suits drag racing well.



major said:


> And the chassis dynos I've had experience with used a torque arm with load cell for drum torque measurement.


An engine or chassis output measuring machine can have just a brake (the source of the term "brake horsepower"), which measures torque and speed, from which it can calculate power. This is much more useful to determine the power (and thus torque) output of an engine over a range of speeds, but is limited by how long the brake can dissipate power before overheating.

Using a drum (to simulate the mass of a moving vehicle) with direct measurement of the torque applied to it is an advance on the simple time-and-speed drum.

Better is both: a drum (for inertia) plus a brake (for drag) with measurement of both force (torque) and speed. Current technology is simpler: the rollers run a generator, which is controlled to set the desired drag. Torque is measured by a shaft coupling equipped with load cells. Any desired operating scenario can then be programmed, and there's no estimation of what is being put out by the vehicle. This level of hardware is routinely used by adequately funded race teams and even individual enthusiasts with enough cash.

Regardless of the hardware, it seems that chassis dyno computers are routinely programmed to report torque at engine speed, because that's a number people want for comparison.



major said:


> All this really gets back to what I called the real issue: force, or tractive force.


Right - force applied to the ground (reacting against the vehicle to drive it) and the speed of movement are the two measurable quantities which fundamentally matter; power is the product of the two.

Since the variance of power availability with speed is different between gas engines and electric motors, it helps to understand what needs to be delivered, not just the peak power output of the gas engine which produces the same performance.


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## brian_ (Feb 7, 2017)

62Farmtruck said:


> Dyno pulls rpm via spark plug wire. But, it doesn't know if you are in a 1:1 Trans gear, doesn't know if you have a 2.73 gear with a 22" tire or a 4.88 with a 33" tire. It simply looks at how fast you accelerate the 2,500lb drum.


As Karter2 and major explained, it has both the engine speed and the drum speed, so it is scaling the torque (proportional to rate of acceleration of the known-inertia drum) to the speed to report an equivalent torque for the engine speed.

If you still had a distributor, you could put the plug wire pickup on the coil wire instead of a plug wire - then the dyno would see a spark frequency eight times higher, and report one-eighth of the torque... because it _is_ dividing by the ratio of engine speed to drum speed. It doesn't know the gear ratio or tire size, but it does know the overall speed relationship.

If you change the tire diameter or gears you're not changing the power output of the engine, so you don't see a corresponding change in the measured power or calculated torque. Specifically for tires: spinning smaller tires at a higher rotational speed to achieve the same drum speed makes no difference to the dyno.



62Farmtruck said:


> I guess we could look at the time it took to accelerate the drum and try to work that backwards ending up with a required motor output .


That's exactly what the dyno is doing... and all that it is doing.


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## brian_ (Feb 7, 2017)

62Farmtruck said:


> My experience on the dyno tells me rotating weight of the rear tires/wheels...
> ... will also skew the numbers...


Yes, that's one of the problems of this inertia-drum dyno method. It is measuring the time to deliver a known amount of energy into the spinning drum, but ignoring the energy which goes into the spinning wheels and tires (and engine and other driveline components). Of course those bits all need to be spun up in a real run, too, so the machine is a reasonable way to assess change in drag race performance produced by an engine change - it's just not a very accurate way to measure actual engine output.



62Farmtruck said:


> My experience on the dyno tells me...
> ... tires construction (bias vs radial) will also skew the numbers ...


This is a problem with all chassis dynos in which the tires run on rollers (which is most of them). They're not a great simulation of a flat road surface, so the tires are distorted more than they are on a real road and the energy dissipated distorting them represents unrealistic extra drag. Tire construction and size and pressure affect this drag, and not necessarily in quite the same way that they affect drag on a real road.

Some chassis dynos link directly to the hubs, with the wheels removed, to eliminate tire effects entirely. What machine is appropriate depends on what aspect of the vehicle is being studied.


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## 62Farmtruck (Sep 4, 2017)

The bigger issue on a chassis dyno with regards to tire change is where the rotational weight is put. 

A 30" radial is heavier than my 32" slick, but the weight of the slick is further out from axle center line. This alone makes it more difficult to turn the tire. Same height radial vs bias, the bias normally shows a little higher output on the dyno.


I have to disagree a bit with how the tire distorts. My slick distorts a ton at the starting line and for about 60' the side wall is wrinkled and the contact patch sees cupping do to the side wall distortion. You don't see this on dyno as the drum does not put the same force to the tire, it simply does not weigh enough. You rarely see a radial wad up at the track let alone on the dyno.

Now, if we are talking contact patch and resistance, then yes, a static foot print check using a sheet of metal with chalk dust shows the radial has less front to back contact than a comparable sized slick. This is due to a couple of things. A bias has 2 belts that run the around the circumference where a radial is in the sidewall going side to side stiffening the sidewall and contact patch. A radial has typically runs more air pressure than a slick. Same power, comparable sized bias/radial, the radial goes +/-0.15 faster onyou truck with more mph as long as it hooks, simply due to the rolling resistance even though it is heavier.



But I think we are getting off topic a bit. 



If a tire was directly driven by a motor that made 150ftlbs at 1,000 rpm, would the dyno report that as 150ftlbs?


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## brian_ (Feb 7, 2017)

62Farmtruck said:


> I have to disagree a bit with how the tire distorts. My slick distorts a ton at the starting line and for about 60' the side wall is wrinkled and the contact patch sees cupping do to the side wall distortion. You don't see this on dyno as the drum does not put the same force to the tire, it simply does not weigh enough. You rarely see a radial wad up at the track let alone on the dyno.


I'm not surprised that the dyno doesn't simulate starting line conditions well. For one thing, load transfer is not likely the same. That's not where you'll be at the motor power limit anyway... but torque to the tires will matter to your launch, and while the electric setup will have constant torque from some low speed all the way down to zero, it won't have the torque multiplication of a torque converter.

Sidewall distortion due to load (changed by rollers versus flat surface) is not the same as sidewall distortion due to torque (the launch effect which you don't see on the dyno).



62Farmtruck said:


> A bias has 2 belts that run the around the circumference where a radial is in the sidewall going side to side stiffening the sidewall and contact patch...


Radials have under-tread circumferential belts, too; proper belts (often steel) are why these tires don't grow very much with high speed. A bias-ply tire with those belts is properly called a bias-belted tire, but since in recent decades people seem to just call them bias-ply.









Bias-ply drag slicks may still be non-belted (street "bias-plys" are bias-belted). If radial drag slicks didn't have belts, they would be (as far as I know) the only non-belted radials in existence... which seems exceptionally unlikely.

Since we're into tires, to get it back to EV conversion...
The advantage of bias-ply drag slicks is the "springy" effect of those wrinkle-walls, which can be helpful, particularly for cars with clutches (rather than torque converters). The electric powertrain will not use a clutch to start, and doesn't need clutch slipping or torque converter slipping or tire wrinkling to allow the motor to produce full torque without "bogging".



62Farmtruck said:


> If a tire was directly driven by a motor that made 150ftlbs at 1,000 rpm, would the dyno report that as 150ftlbs?


Yes, assuming that the motor speed signal to the dyno came from that motor or anything else that produced one pulse per revolution of the axle.

Of course, in this case we're talking about wanting something more like 4,000 lb-ft of torque from zero up to some wheel speed (up to 1100 rpm if 838 hp is available)... then reducing torque as the power-limited motor runs at up to 1700 rpm (and something less than 2500 lb-ft if still producing close to 838 hp) of the end of the run.

Of course that's way too slow for the motor (it would be too heavy if required to produce that power at such a low speed), so the motor will be running faster with proportionately lower torque.


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## dain254 (Oct 8, 2015)

62FarmTruck - I'm assuming your irritation was at my Tesla suggestion. Brian and Karter like to correct my suggestions because I leave out a lot of assumptions, such as a spaceframe would have to be fit to the dismantled Tesla to REALLY make it work... of course. 

The joke is, that nobody has discussed cost of any of this - do you have a budget in mind? Believe it or not - some of us have an extensive racing background and there is reason we stick to good ol' internal combustion when wanting to go fast. Slap some turbos on an LS engine and make 1000hp good for a few 8 second passes for $5k, or build a reliable NA big block for around $20k that'll do 1khp - but there is no cheap way to go fast with electric! To do your project correctly in my mind would run somewhere between $60-80k if you want to build with new parts. This includes a pair of 60kwh chevy "Bolt" batteries (because they would package in your bed) giving you 120kwh total to push a heavy brick 200 miles down the road. Two tesla rear drive units MAY get it there in performance? (one front/one rear) - a person could also use dual custom warp 13 motors that may also get you there power-wise through a turbo400? 2speed powerglide? THEN all of the computer equipment required to link this all together - BMS for the 2 96S packs, charger... it is an obscene amount of nonsense and tinkering required to do all of the above - which makes finding a wrecked P100D for $40k and remaking it into a pickup actually pretty damn practical.


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## Duncan (Dec 8, 2008)

I agree with dain
For moderate performance like my Device - 800 Kg and 500 Hp - electric is cheaper than IC - 

But for an 8.5 second machine anything is going to be expensive


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## brian_ (Feb 7, 2017)

I had not addressed cost, both because I have little expertise to offer in that area, and because I was waiting for a proposed direction to emerge for both motor and battery.

The Tesla approach - with complete motor/transaxle units - really can work, but is more like starting a new vehicle than developing the existing truck.

One approach puts a motor (or set of motors) in place of the engine and retains the general configuration; I think the approach which 62FarmTruck was expecting to use. I don't see the point of a conventional automatic transmission (such as a THM 400) with an electric motor since the converter's torque multiplication doesn't seem worth the slip; however, it does provide multiple gears and a mechanical reverse in case the specific motor used is not readily reversible. Perhaps the torque converter can be omitted - there's a massive thread in this forum about using automatic transmissions.

It would likely be helpful to have the torque multiplication of one lower gear for the launch, so a two-speed drag racing transmission (Lenco or whatever) would make sense to me; it could even be left in high gear (1:1) for street use, and a reverser is available. Maybe the THM400 is the affordable way to get similar functionality, and some sort of PowerGlide variant would work too, but the Lenco would be simpler, more efficient, and likely more reliable. Unfortunately, it looks like Lenco only offers up to 1.73:1 in a CS2 two speed... maybe not worth doing, depending on the motor.

What transmission is the truck running now?


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## Karter2 (Nov 17, 2011)

62farmtruck...read this thread for background info..
http://www.diyelectriccar.com/forums/showthread.php/assault-n-battery-build-thread-74539.html
The thread is practically a shopping list and illustrated build manual for a 8 sec EV.
..it will answer many of the questions you have yet to think of.
Then talk to the author, John Metric, to get the inside word on how to get a EV into the 8sec bracket.


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## brian_ (Feb 7, 2017)

Karter2 said:


> 62farmtruck...read this thread for background info..
> http://www.diyelectriccar.com/forums/showthread.php/assault-n-battery-build-thread-74539.html
> The thread is practically a shopping list and illustrated build manual for a 8 sec EV.
> ..it will answer many of the questions you have yet to think of.
> Then talk to the author, John Metric, to get the inside word on how to get a EV into the 8sec bracket.


Great idea. I'm only a couple of pages in, but I see similar numbers and some of the same components being discussed (including what is apparently a Lenco CS1 transmission, but with Gear Vendors overdrives); however, it seems like most of the images are now missing, so it's a bit like watching a movie with your eyes closed most of the time, depending only on the dialogue!

Keep in mind that "_Assault n Battery_" uses a Miata body, so it's a much smaller (and aerodynamically better) vehicle than the truck.

This car uses overdrives because it uses relatively slow DC motors; if you use AC motors that are suited to higher speeds, lower gearing would be suitable.

... and by the end of 213 posts, the discussion may be about an entirely different vehicle.


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## Karter2 (Nov 17, 2011)

Shame about the photos and videos, i suspect John will still have them on his Facebook page.
But yes, A&B was an earlier project of Johns, he followed up with the DC powered rail "PID" , and is now on to an AC version i believe.
http://www.diyelectriccar.com/forums/showthread.php/panic-detroit-update-171338p2.html
http://www.diyelectriccar.com/forums/showthread.php/2000hp-bldc-215lb-10-motor-179521.html

Apologies to those who are already familiar with these threads.


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## 62Farmtruck (Sep 4, 2017)

700ftlbs currently

700 * 1.76 first * 4.22 = 5,200ftlbs

Estimated Converter multiplication of 2x means I am hitting the tires with over 10k ftlbs.


Instead of a th400, the 80e would provide the same first gear to help with starting line ratio but give an overdrive. This configuration would allow me to keep the rear motor in the higherror part of the torque curve until I needed the MPH of the over drive. I just don't like the weight (prefer it in the battery) and losses with the hyd system. Not sure I'd want to add a converter to the mix, but if I did it is a lock up. 

Might be able to mount the trans right at the back of the cabest and run a short drive shaft.

Not sure how to deal with the front though. Maybe a center section with 2.73 gear to an IFS using either Trail Blaze SS or Jeep SRT8 spindles. 5,000rpm and a 30" tire gives me 163mph.

I did speak to one of my customers. They are entertaining the battery testing platform.


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## Karter2 (Nov 17, 2011)

62Farmtruck said:


> 700ftlbs currently
> 
> 700 * 1.76 first * 4.22 = 5,200ftlbs
> 
> Estimated Converter multiplication of 2x means I am hitting the tires with over 10k ftlbs.


....im glad we clarified that issue .




> .....I did speak to one of my customers. They are entertaining the battery testing platform.


?? What are they "entertaining' exactly ?
Offering you a battery pack ?
Testing your battery pack?
Sponsoring you for a battery pack?
Unless they have serious experience of EV drag performance, they will just be playing catch up to folk like J Metric , S Lawless, J Wayland, HTS, etc...who have done the testing and proven what is needed for a race pack.
Best to just beg for their money and buy the proven pack.


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## 62Farmtruck (Sep 4, 2017)

The battery company I am referring to currently developes their own cells, does all the battery management of the cells and produces finished packs. They are one of the top 10 suppliers for EV packs today. Their focus has been less on high out put but they want to get in to that market.

This would give them a test bed for new development in high throughput cells to pack.


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## Karter2 (Nov 17, 2011)

make sure you have the data aqusition and logging facilities to fully understand how the pack, controller and motor are performing.
Infact i would want to see some convincing high current lab test data before entertaining a new pack supply.
You are not looking for "high output" cell performance, ....but more like "extreeme output" cell performance.... A pack that can surge 4000+ amps with minimal voltage drop, and minimal weight.
I doubt a producer of cells for mass EVs will want to develop cells to the extreme level that you will need.


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## John Metric (Feb 26, 2009)

62Farmtruck said:


> Correct me if I am wrong but energy storage is the main issue. A 200mile range requires a lot of energy storage and I have to assume 8.5x in the quarter at 3100lbs requires a lot of energy storage as well.


Actually I estimate your 8 second run would only consume about 2KWH.
My 7 second runs only consume about 1.5kwh in a lighter car.

To drive 200miles you are going to need 80-100kWH.


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## John Metric (Feb 26, 2009)

I have the system you need sitting in my shop.
Motors plus OD = 1500ftlbs zero to 6000rpm
direct bolt up Lenco CS2 three speed (available) and a good battery (available) and controller system (available) and you are there.

Give me a call. 979-665-5621


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## John Metric (Feb 26, 2009)

bump and PM sent...


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