Converting Wheelchair controller to hand throttle

[catch22]

Hi.  I am new to this board and a novice when it comes to DC systems.  I am building a small wood car.  I have purchased a set of 24V wheelchair motors with the controller and throttle.  This is a joystick system.  I am planning to change this to a twist throttle and set this up as a pedal throttle.  The controller is a Penny & Giles.  The joystick has 4 wires. 

I want to use reverse for the car.  In the wheelchair, you would just go backwards on the joystick to get the unit to go backwards.  I know I will need to add a switch to activate the reverse.  In looking at schematics for the P&G.  It shows the red wire as the reverse. 

Can someone give me assistance in how to hook up the reverse so that I can run it off the hand throttle. The hand throttles come with three and 4 wires.

[Soeren]

Hi,

For starters, post all the wiring diagrams that you have.