Caster Angles in Shopping Carts: How to Control Wheel Paths

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Charles123
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Can you draw a force diagram to explain how a positive caster angle makes wheels return to a straight line in a shopping kart (as an example), while a negative caster angle would have the opposite effect.
Thx
 

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Charles123 said:
Can you draw a force diagram to explain how a positive caster angle makes wheels return to a straight line in a shopping kart (as an example), while a negative caster angle would have the opposite effect.
Thx

For this question you don't want the PF crowd, you want the people who set up and drive race cars.
 
A shopping cart wheel uses a caster displacement, the pivot axis is vertical, and the wheel axis is behind the pivot axis, so that if the wheel if off to the side, it gets pushed back to straighten it up when the cart is pushed forwards.

A car uses an angled pivot to get a similar caster effect. Wiki article:

http://en.wikipedia.org/wiki/Caster_angle
 
I understand the idea, but I would like to see a force diagram of it. Thx