Using two motors on one axle

Our robot has a long arm for picking up Elevation cubes (up to 4 at a time). The arm has rotating wheels and two motors to drive the wheels. This arm works very well, except raising and lowering it is very slow because we had to gear it down in order for the motor to lift it. We also added rubber bands to help the motor lift it.

We would like to add a second motor to lift the arm and gear it so that it moves faster.

Do we need to worry that the two motors might be slightly out of sync with one motor actually causing strain on the other while they raise the arm?

No problem, the two motors tend to self-balance. The slightly faster/stronger motor will take more of the load, which will slow it down a bit until the slower/weaker motor starts to contribute.

This advice does not quite apply to servos, since if they get a few degrees out of sync with each other, they will burn energy in a tug-of-war (turn-of-war?).


  • Dean

just make sure you use clutches in case you accidentally reverse the motor directions.

That is what I thought when I first started working with Vex, but now I think otherwise. There has been a lot of discussion about whether clutches do any good or not. The consensus as far as I can tell is that the clutches won’t do anything at the torque generated by the VEX motors - they are intended to protect the motors from “shock loads” such as a motor being strongly back-driven by an external force (like somebody pushing down on a robot’s arm).

As an experiment, I hooked two VEXplorer motors together through a clutch, and ran them both at full power in opposite directions. The motors stalled and the clutch did not pop.

So, certainly use the clutches to protect the motors from external forces, but I don’t think they do anything to protect the motors from themselves.


  • Dean

Depending on how the Motors are attached, they might need to be Reversed or Not.

Thats true marko. The odd thing is that one time i hooked to regular vex motors together without clutches and stripped the internal gears.(that was with both motors at full power going opposite directions)

Just use a vex y-cable. I had four motors hooked to and geared down to lift an extremlely heavy arm and it worked fine.

y cable will not work if the axle is directly connecting the two motors. They need to spin in opposite directions.