# Planning VW T3 syncro EV



## Devious (Feb 13, 2015)

Any thoughts would be nice :-$


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## matthiaswm (Nov 23, 2010)

I *love* these cars. Do it! I converted a T2 for the same reason for additional load for the batteries.

Now, if I understand the concept of the Tesla 4WD correctly, you should get two different electric motors, and - depending on your speed - put more power to the motor that fits the torque curve.

I am located in Germany, and I would love to see the results of your work ;-)


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## eldis (Sep 3, 2013)

The two motor - two diffs concept is nice, I was also thinking about making my next EV like that. Probably nothing wrong with that, as long as you can fit your two motors in the tunnel (probably not without major cutting or having smaller diameter motors). I'll be definitely watching your progress 

400Nm sounds like a lot - is it with two motors combined?
You've mentioned that original diesel engine: 51KW 138Nm


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## Devious (Feb 13, 2015)

eldis said:


> The two motor - two diffs concept is nice, I was also thinking about making my next EV like that. Probably nothing wrong with that, as long as you can fit your two motors in the tunnel (probably not without major cutting or having smaller diameter motors). I'll be definitely watching your progress


The rear one would fit in the engine compartment. The front one may fit to the front of the van, in to the spare weel space in front of the diff



eldis said:


> 400Nm sounds like a lot - is it with two motors combined?
> You've mentioned that original diesel engine: 51KW 138Nm


No gearbox means no gears. The diff's have a gear ratio of 5,43:1 (gearbox: low gear 6,03:1 high gear 0,78:1) diesel engine: 51KW 138nm So to have at least the same off-road capability's as the ICE with gearbox I would need: 
Engine Tork x low gear / motors = tork per motor
138x6,03/2= 416nm
2 motors with 416nm max


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## eldis (Sep 3, 2013)

Devious said:


> No gearbox means no gears. The diff's have a gear ratio of 5,43:1 (gearbox: low gear 6,03:1 high gear 0,78:1) diesel engine: 51KW 138nm So to have at least the same off-road capability's as the ICE with gearbox I would need:
> Engine Tork x low gear / motors = tork per motor
> 138x6,03/2= 416nm
> 2 motors with 416nm max


Okay - I don't really know much about torque requirements for extreme off-road cases, but it still sounds off. I mean how wide is your 138Nm torque band on the engine curve?
Electric motor provides full torque at 0RPM, combustion engine has practically zero Nm at low RPM (therefore a clutch is needed to start moving). Maybe someone more experienced with combustion engines will be able to put more light on this, but I would still say that your number is way too high - we can try to compare with the Tesla Model S. It has 600Nm (one motor) with a single speed gearbox, 9.73:1, car weights 2100kg and does 0-100km/h in 5.4sec


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## Devious (Feb 13, 2015)

My calculations are best case scenario.
So with 400 nm there is no point in the rev range the ICE van would be stronger then the EV van.

Of course this means the EV will be far superior over the ICE version. Since the torque starts, like u sad, at 0 rpm

If I would go with less torque this means that the ICE version would be stronger at its sweet spot rpm.

I don't know how much torque would be sufficient to be over all equal in terrain


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## MalcolmB (Jun 10, 2008)

Hi Dirk

I suggest you start out by estimating the maximum gradient that you are likely to tackle.

For example, if the maximum gradient is 1 in 3, then you need enough traction at the wheels to lift 1/3 of the weight of your vehicle, say 1200 lbs.

If your tyres have a radius of 1 foot, that means you need 1200 ft lbs of torque at the axles.

If you use a diff with a ratio of 5.43:1, it means you need around 220 ft lbs at the motor shafts (1200/5.43).

So each motor would need to produce at least 110 ft lbs of torque.

The main reason this number is so much lower than the number you calculated is that internal combustion engines require higher gear ratios because they produce their peak torque over a relatively small rpm range.

Neat lego model!


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## Devious (Feb 13, 2015)

So the ICE can tackle a 60% incline.
that's 60/100
Wheel radius: 0.33 meters

so:
(car weight in N x gradient x wheel rad) / diff ratio
(16000 x (6/10) x 0,33) / 5.43 = 583 Nm (430 ft lbs)

sow 290 Nm (215 ft lbs)

and that's assuming the car doesn't put on any weight in the conversion.

it's less but still...

found the lego model picture with google ;-)


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## eldis (Sep 3, 2013)

Considering your requirement on the hill climbing and general off-road-ness, I would vote for keeping the gearbox and the original 4x4 configuration. You will then be able to use much smaller motor, also you don't need two inverters for it, less mechanical work, etc.
What most people around here suggest is to go direct drive only if your expectations on low speed performance are not that high (as high ratio diffs are hard to come by), or you have some serious motors in mind.

Alternatively you could aim for an AC motor with many poles - typical number is 4 poles, but if you get let's say 8 or more, it acts as "an electronic gear" - higher torque, proportionally lower RPM (not taking the field weakening into consideration).


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## Devious (Feb 13, 2015)

I'm starting to think your right. There is just no need to out preform the Tesla ;-)
Or go over 100 mph 

My torque requirements are just to high at low speeds. I only need about 100 Nm to get to my top speed of 130 km/h


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