Torque at Wheels
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  1. #1
    Member DragoN's Avatar
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    Icon11 Torque at Wheels

    Does any one know how much torque a fast car(0-100km in 4sec) will have at the wheels in first gear.

    Ps my mate and i are working on electric car designs for a school project and at the moment have a pair of direct drive pancake motors that put out about 760n.m(560lbf.ft) of torque untill about 3000rpm

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  2. #2
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    Dragon, unfortunately, ultimate acceleration also depends on the kerb weight of the car. In addition, electric motors produce maximum torque from 0 rpm, unlike an internal combustion engine which develops torque gradually until a peak at about 3000-4000 rpm, so your question won't really have any relevance to your project.

    With that sort of torque you'd be able to gear them at +2x and any car under 1000kg would still fly off the line. Where did you get those motors? I can picture them in the rear of a Mini Moke at 600 odd kilos. Plenty of space for the batteries.

    Stu


    2003 PEUGEOT 206 GTi

  3. #3
    Fellow Frogger!
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    i have found a few links but none of them talk about the torque of the motor. But for the year 2000 the record for the quarter mile is -

    1/4mile : 8.801 sec @ 137.65 mph : 336V Dragster

    1/4mile : 9.450 sec @ 152.07 mph : 312V Motorcycle

    - thats quick

    '04 Citroen Xsara VTS

    Mallala - 1:29.96

  4. #4
    Tadpole
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    electric motors produce maximum torque from 0 rpm
    Also curious Dragon as to where you friend got this information, cause like Stuey says, electric MOTORS produce maximum torque at stall, i.e, not moving. Curb mass, tyre size, rim pull, displacement coeffcient (of the tyre, you seen how top fuelers tyres expand down the 1/4 with their speed) all play huge parts in how 'fast' a car can be.

  5. #5
    1000+ Posts U Turn's Avatar
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    Yeah there are lots of factors that play a part on top speed, even the splat of a gnat I'm sure would make a 0.0005% or so difference. Anyway, it looks like you want only ballpark figures. So I'm going to assume the 'fast car' that does 0-100 in 4 secs is something like the fastest ferrari/porsche/lambo etc. We could take all these cars that match the criteria and apply regression analysis but that's getting down to gnat's knob details again....So I think assuming a kerb weight of around 1500 kg and flywheel power of 400-500 kW and flywheel torque of 600-700 Nm. I think this safely constitutes a 'fast car'. Now let's assume a final drive ratio of around 3:1, and 1st gear ratio of 3:1. I haven't even checked this, but you can and can change the maths to suit. But it should be around the ballpark.

    So torque at the wheels IN first gear is = flywheel torque x final drive ratio x 1st gear ratio x transmission efficiency. (Transmission efficiency is same as drivetrain losses, and you can use a figure of 0.7). So roughly torque in first gear at the wheels = 600 x 3 x 3 x 0.7 = 3780 Nm. Rim size does not come into it because we are still dealing with TORQUE at the wheels, not the force acting on the ground. If you wanted force acting on the ground, divide the torque figure by the wheel diameter.

    I did this quickly, so someone please correct me if I stuffed up somewhere.
    Take the long way home....

    - 306 gti6

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