Tony Young and I were posting back and forth about motors for dip tubes. Tony mentioned using a threaded rod with a stepper motor to pull it back and forth. I pondered this for a while, and decided to grab a few bolts and see how the line would wind. I just chucked them in my lathe and turned the headstock by hand. Lo and behold, the line wound perfectly into the threads, without the need for a guide. I whipped up a spreadsheet to play with thread size and pitch, and discovered that a 4" length of 3/8-16 threaded rod will wind over 60" of line. I use 12# backing material for the line.

A lot of folks are using this motor already, so nothing new except for the line handling method. The threaded rod gives very tight control over speed, the diameter is not constantly changing as line is taken up or let out.

The stepper motor and controller are the ones sold by H&R (see the Rodmakers page). Part numbers are: TM93KIT2421 (kit) or TM93KIT2421/A (assembled unit).

I whipped up the support from some scrap MDF, covered with scrap pieces of plastic laminate. Note the "scrap" theme here.. this works, and is cheap! I cut a 4" length of threaded rod, and simply drilled the end in the lathe to be a light press fit onto the motor shaft. I drilled intersecting holes on the free end of the rod. The line is run through the holes, with a couple of knots retaining it inside the free end. In other words, the line exits the rod directly into a female thread. I mounted the motor on the support, with only a 4" piece of rod, there is no need for a bearing on the "free" end of the rod. I just put the support on the top of my cabinet with double sided tape. The rod is about 6" above the top of my cabinet, which allows the line to thread without the need for any kind of complicated guide. The line passes through a small hole in the top of the cabinet. It could just as easily be mounted inside most cabinets. I used a scrap power supply from a long defunct laptop. The power supply and the controller are mounted in the plastic box (available from Radio Shack, etc). To connect the controller and the motor, I went back to the computer junk box and found an old serial connector and cable. If I were to buy something, I'd probably spring for a mini DIN connector and cable. A 6 conductor cable is required. The motor is connected to the control as shipped (the assembled unit). It could be used just that way, but I wanted to be able to disconnect the cable from the box and motor. As you can see, I cut holes to allow the LED's to be visible. Although they do more or less display the operating mode, who cares, once the best one has been determined. If I did it again, I'd simply bend the LED's over and forgo the holes, it would simplify the layout for the top of the box.

Speed is infinitely variable, from waaay slow, to way to fast for our purposes. Motor is reversible, and stops instantly, one of the hallmarks of stepper motors.