Tree Climbing Robot

Step 14 Mounting the Spine

There are a couple problems with getting a threaded spine to spin smoothly.  First, it must be coupled to the motor well, and second it must have some sort of bearing fixed to it on which it can spin.  One of the first things I found while trying to couple the motor shaft to the threaded rod was that the connection should be flexible for smooth operation.  I made my coupling out of two segments of clear nylon tubing.  A wider diameter segment fits tightly over the gear attached to the motor shaft, while a thinner segment fits into the larger tubing and tightly over the outside of the threaded shaft.  The coupling is secured with a zip tie.  

With only the coupling, the threaded shaft still can not bear any load, because it would just pull off the motor.  To support load, I made a bearing for the shaft out of an old hard drive read/write head bearing.  I drilled out the center so that the threaded rod could pass through it.  I then fed the rod through it, and fastened a nut on each side of the bearing, to hold the threaded rod in place.  I then bolted the bearing down to the back of the robot's frame.