Two modifications we would recommend to the 4qd control system -

Fitting a Speed Govenor

This involves fitting a 10k potentiometer in line with the existing controller potentiometer. This gives you the opportunity to restrict the top speed from 100% to 0%. Alternatively you could turn the handheld controller up full, put it in the cab, and drive the loco from the speed govenor pot.

Left. The speed govenor (top pot) is wired into the back of the bulgin socket.

Fitting a Deadmans Button

Without doubt this is probably one of the cheapest and simplest modifications to do. For those times when the brain doesn't know what the hand is doing then this could save a lot of hassle and avoid many disasters.

Using a good quality switch which is not too strong to press.

Left - inside a 4qd hand held controller as supplied. Install a push to make switch into the blue wire circuit. i.e. de solder the blue wire from the pots centre pin and solder to deadmans terminal then solder a new wire from the deadmans to the centre pin on the pot. .