# I Starting torque to move vehicle

1. Feb 21, 2017

### Ole Forsell

I am currently working on designing a drive system for a vehicle, and I am calulating the necessary torque to accelerate a vehicle. I am using the guidelines of this source:
http://www2.mae.ufl.edu/designlab/motors/EML2322L Drive Wheel Motor Torque Calculations.pdf

I still feel that there is something missing. Isn't there a required force to even start the vehicle to move from rest? Some kind of friction force which need to be taken into account?

2. Feb 21, 2017

### Nidum

There is but it is seldom taken into account because there is no need . Any practical vehicle has more than enough power available to overcome it under normal operating conditions .

Starting resistance tends to be more of a problem in harsh environments and where a mechanism has been dormant for a long time .

It can be a particular problem in aerospace systems .

3. Feb 21, 2017

### Ole Forsell

So neither the static friction nor the kinetic friction have an impact that works as a counterveiling force? This means that only the rolling resistance is working against the acceleration on the wheels? In my case the rolling friction is very small and almost neglitiable. This means that only the air drag, and gradient force is working against the driving force. Is this right?

4. Feb 21, 2017

### Nidum

All shaft and bearing combinations and things like wheels on roads require a brief but relatively large torque to unstick them and take them from a motionless condition into a normal running condition .

Not a significant problem in normal vehicle design because available driving torques are almost always of overwhelming magnitude .

The only instance that I know of in ground vehicle design where any of this matters is in big trucks for use in oil exploration in the ice fields . Additional engine power has to be specified to ensure that they will start moving reliably when lubricant in bearings has almost set solid .

Last edited: Feb 21, 2017