Quote Originally Posted by DaveintheGrave View Post
It seems to crawl backwards as well as it does forward. I tried it this weekend.
One problem is that since the motor crank rotates so close to the ground, it's easy for the power wire to get wrapped around the motor shaft as it progresses backwards. Unless there's a way to suspend the power cord above the skeleton.
The tether idea would have the same problem, spinman. Also the fact it doesn't move in a PERFECTLY straight line. I might not trip the switch properly.

You use the tether to guide the prop. Use a tube to guide the prop on the tether line.

I think one of the circuit guru's here could help you with a simple circuit that would respond to a signal using a a pair of wiper contacts mounted on the tube. At each end of the tether you wrap the line with conductive tape. The wipers travel along the line until they hit the conductive tape. This will provide a signal to set a latch to close a relay wired for forward travel. Once the prop reaches the end of its forward movement, the wipers hit another section of conductive tape and the signal resets the first latch to off and sets the reverse latch and reverse relay to on or closed.

This is going to require a circuit, but I feel confident someone here could diagram a circuit for you.

You could likely do it with switches, but getting them to actuate reliably might be an issue.

Another idea is to do the switching from outside of the prop. Kind of like how a garage door opener works. Still will need a circuit to make it work thought I figure.