I have built a tank/rover and I have a scissor jack to lift the weapon,
12 volt motor turning an acme shaft to the lift, my question is how to
remote control the motor forward and reverse. I have the rest of the
tank/rover connected to the radio, receiver. I hope this is clear enough.
Thanks, Dave
There’s lot’s of different ways to approach this.
Simplest way would probably be using an extra servo to actuate a switch, which in combination with end-switches on the scissor system gives a complete circuit.
There are electronic ways too, you can substitute the servo with a PIC microcontroller for example, which will drive the motor and check the end-switches to know when to stop.
Offcourse you could also filter the RC output with a low-pass filter, hook it up to an opamp configured as comparator and use that to drive a relay which in turn drives the motor, etc etc.
As you can see there’s lots of possibilities, it all depends on your skill, time, and cashflow 
Exactly what kind of 12 volt motor are you using?
Brand…etc.
SamQ
Current draw???