How to make a vehicle move?

Question

hi everyone,
Does anyone know how to choose an electric motor for a small vehicle like an electric wheel chair base on the torque requirement.The vehicle that i want to build have an overall weight of 150kg. What do i do first? i had an initial idea where if i specify the speed of the vehicle say v m/s, then i can just simply use the equation P=Fv,where P is the power from the engine,F is the frictional force. is this correct? how about inertial force?

Is there a good website for me to analyse this problem?

Answer 1

To get the torque requirement, you need a better analysis.

Torque = power/speed.  You can meet your torque requirement by varying the transmission ratio between the motor and your wheels (half the torque at double the speed is the same power).  What you really want to find out (and you'll have to do this yourself) is two things:

1.  What kind of starting/holding force do you need?  This will include all the drag forces of the motor and reduction train, to the static rolling resistance of the wheels AND whatever surface they're on (like deep-pile carpet?), PLUS the force from any slope you might be trying to climb.
2.  What power do you need?  Worst case, what speed do you need to go against how much drag/gravity?  All the drivetrain drag figures into this too.

Just specifying the problem well enough will probably show you your answer, or most of it.  That's pretty much how it works in engineering; you can't get the answer until you have learned how to ask the right question!

Answer 2

you also need to find stall torque, no load speed these along with your motor power should help you find the motor you want

Answer 3

Yes there is..try www.askjeeves.com!! It really works wonders...this one time..at band camp, we had to look upa classical piece of music that was not in our music books and sure enough!!!! I found what I was looking for..ta da!!! So you go try it out and lemme know how it goes...
Chao!!