[Joe Schornak]

My team is considering using a window motor to actuate an arm mounted to a forklift-style lifter. During the course of our testing, we determined that the motor could lift a four pound weight mounted 13" from the motor axle on a simple aluminum arm. However, the motor does not actuate smoothly under this load, and rotates somewhat too quickly for fine control. We suspect that it will work better when mounted into a gearbox.

There are a number of ways to attach things to the motor, depending on how much machining you're comfortable with. You could mount a sprocket onto the plastic axle adapter thing and build a frame around the adapter to hold it all together. This method is relatively simple, but the frame might make the chain and sprocket difficult to access. It's also quite heavy, since you'll need to use a short axle with a bushing for proper support and rotation.

Alternatively, drill and tap a hole into the end of the axle, and use a bolt to hold the plastic adapter onto the motor. This is legal under <R47>A, and is much more compact than the first method. However, it requires a specific set of tools and skills, so you might want to have one of your machine shop sponsors do this for you for best effect.

As Chris said, you should consider the thermal safety lock when designing your arm. The worm gear will hold the arm at an angle without stalling the motor, but the window motors will overheat if you try to move something too heavy. My team reduced this problem by installing external cooling fans around our window motors, but they still locked up after prolonged use.

Best of luck with your robot-building!