Electronic Solution to designing a Steering System

Hi all

I am building myself a remote controlled car with a lawnmower engine, and am currently having some difficulty in designing a steering mechanism, hoping all you guys could help.

What I have is a window wiper motor to operate the steering system and a servo, now I just need to design a system as basic as possible (hopefully just using switches, levers and wire).

What Im hoping to achieve is basically a variable steering system, i.e. you push the stick on the remote control half way and the motor turns the wheel in half the turning circle, push the stick all the way and the motor turns the wheel to the complete turning circle.

As I said, Im hoping to achieve this with as simple a solution as possible, i.e. with push-release switches, normal switches and wire.

If there are better ways of doing this please let me know as well.

If anyone can help me or give me ideas it would be much appreciated.
Thank You