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# DC motor with 30nm torque and more than 3000 RPM Answered

Hi I need DC motor with 30nm torque and more than 3000 RPM how to build this or form where I can buy this in India please guide me on this also tell me what should be battery specifications to run this for 100km with the total load of 250kg?

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## Discussions

Is 30 N*m (newton*meters) the stall torque (torque at zero speed), or is it the torque at 3000 RPM?

If its the second one, then this is kind of a beefy electric motor. I mean how much mechanical power is 30 N*m torque, multiplied by 3000 RPM?

Convert RPM to radians per second, by multiplying by (2*pi rad)/(60 s), so

So torque multiplied by speed, in SI units, is

P = (30 N*m)*(314 rad/s) = 9420 watt = 9.42 KW

Divide by 746 watts/horsepower, to get 9420/746 = 12.6 horsepower

Basically, you are asking us how to build an electric car.

Coincidentally, there was someone else on this forum, this week, asking us how to build an ultralight airplane.

I think your idea to build a car is more realistic, and, if you'll forgive the pun, more uh, "grounded".

XD

Back to what I was saying before, about torque and speed, I do not think an electric motor is fully characterized by just those two numbers. Rather, every motor has a characteristic torque-speed curve; i.e. the graph that you get when you plot the torque for each speed over a range from 0 RPM, to whatever the maximum speed is. Also the integral of this curve is a power-speed curve.

I was looking for a kind of tutorial on torque-speed curves. I could not find one I liked, but I am going to point you towards an example of one. It is on this page,

https://www.osvehicle.com/osv-platform/

under the tab labeled "Powertrain", and that is a page I wanted to point you towards anyways, because it is basically an open-source electric car.

I am kind of guessing the usual plan for an electric car uses a motor with a flat, or downward sloping, torque-speed curve, so that the motor can give you its maximum torque at zero speed, so that you can easily get the car rolling from a complete stop, and also you can do this without the need for a transmission with different gears, like is typically needed for an internal combustion (IC, ICE) engine.

All the nitty-gritty details of this OSV "TABBY" design are available for download, I think, here,

although I have not downloaded anything from them myself, because I was stymied by a lack of social credentials. I think they want me to "like" them via Facebook(r), or "tweet" or "retweet" them via Twitter(r), or something-something, them via GooglePlus(r), and I just cannot be bothered with any of that.

I also noticed there was a user here on instructables, named "bennelson",

https://www.instructables.com/member/bennelson/

who seems to have written a bunch of 'ibles on the subject of electric cars.

You'll see his username in many of the results that appear in a Let's make: search for "electric car".

https://www.instructables.com/howto/electric+car/