# Homework Help: Help, Need to calculate braking force? PLEASE HELP!

1. Apr 24, 2010

### a_u_nscopio

Hi guys, I am new to this forum, but I am in desperate need of help on something for my Final year university project. I have designed a Trolley and need to calculate some forces.

Does anyone know the formula to calculate the pushing forces required to stop this trolley from moving.

Weight of trolley is 1687 Newtons
the force of the spring pushing the rubber pad 98.1N.
The trolley is traveling around walking pace, 4mph.
Force required to move trolley forward is about 27N on level ground (road)

So currently 98.1N are pushing on the Pneumatic wheel, but I am not sure whether or not this force is strong enough to prevent trolley stopping when in motion.

It is a standard pneumatic wheel, with 50mm wide rubber material. The width of the rubber pad is 50mm x 50mm.

Is is possible to calculate the force of friction required to stop the wheel from spinning. The pneumatic wheel has textured rubber, as does the pad, which probably increases friction.
The pads act on two wheels.

[PLAIN]http://img714.imageshack.us/img714/1829/trolley1.jpg [Broken]

[PLAIN]http://img38.imageshack.us/img38/2768/trolleyv.jpg [Broken]

Thanks!

Last edited by a moderator: May 4, 2017
2. Apr 24, 2010

### rock.freak667

I am not sure if I can help you as I am only familiar with disc and band brakes. This was my thought process on your problem.

But you wheel will have a normal reaction to oppose the weight of the trolley. So there will be an associated rolling friction with that which will act in the same direction as the braking friction.

If you can find the torque needed to make the trolley move at 4mph, you can do a torque balance on the wheel:

Tpushing-Trolling-Tbrake=0, where you can get Tbrake and hence Fbrake.

So you can get the pressure needed to activate the braking system.

3. Apr 24, 2010

### a_u_nscopio

Hi thanks for you help, I forgot to mention, I carried out some testing, and the force needed to push the trolley was about 27N on level ground (road).

4. Apr 24, 2010

### rock.freak667

That would be your resultant force. So 27=Fpushing-Frolling friction

5. Apr 24, 2010

### a_u_nscopio

Again, thanks for your help. I'm still not quite sure, I am a design student, so my engineering skills are quite bad. Could you perhaps elaborate some more? Thanks

6. Apr 24, 2010

### rock.freak667

If you ignore the wheels for the moment, the force you found would be the resultant force. So if you use the equation

Resultant force =Fpushing-Ffriction

and find Fpushing, this will be the total force needed to push.