Servo… Tubing… You get the idea…
We will have it on the website today, or tomorrow. 8)
Neat.
Probably not where you intend to go with this but it opens up some interesting linear actuator ideas to tinker with.
Here’s the product link:
lynxmotion.com/Product.aspx? … egoryID=89
Package includes 2x hubs and 2x 1/4" 4-40 screws.
Linear?
More like a big drive shaft!
Alan KM6VV
Yeah this is one of those parts that will have:
a few really cool uses,
a bunch of uses it will look like it will work but it won’t,
and probably the most successful implementations haven’t been thought of yet. lol 
Yeah well that’s one of the obvious choices. I was thinking more along the lines of a nut at the tube end opposite the servo and some threaded rod. Position feedback requires some external mechanism probably, and you wouldn’t want to make it very long, but it’d be real seriously torquey and have zero holding current. Ah well.
Is linear, its a drive shaft, it’s supper pole! Yeah! 
I’ve done that with a 422 by replacing the internal pot with an external slider pot and converting it to CR. It worked pretty well, it’s just slow.
For linear motion, then a hub with a 6-32 or 8-32 thread would allow drive of a simple lead screw. A few blocks threaded to match would then give you the transverse action. If one could also gear a 10-turn pot on on the lead screw, you’d have the feedback. A shaft encoder would be better, but the R/C servo stuff isn’t set up for it. Maybe add a PIC to read the shaft encoder, and run the servo motor?
That could almost run the CNC stuff someone was trying to do with an SSC-32 and R/C servos.
Yeah, it would be slow!
Alan
Robo-giraffe?
I’ve looked at making a linear actuator using threaded rod, but working out thrust bearing issues put it on the back burner. With some installed bearings, the rods could be used as winch spools for some different types of applications.
For light applications, back-to-back sealed flanged bearing races work well. They can be lightly loaded. This is done in the Sherline CNC’s mill and lathe. These are most often driven by stepper motors, but DC Servo motors are also used.
Alan KM6VV
For bearings I went to the local roller rink and got some used skate wheel bearings for free (new genaric ones were $.50 each, but the guy couldn’t find the bulk bag of them). The inside hole of the bearings is ~5/16" or ~8mm. The outside seems to be ~7/8" or ~22mm. Below is a link showing a quick shaft adapter setup I made to check using a servo to turn a wooden shaft. I think a fairly large winch based arm could be made using yard sticks, but I could not find the small block&tackle pullys that would be needed.
Try a “boat” store, like West Marine (CA, USA)
Alan KM6VV
The local harborfreight has the below pullys. A little heavy, but the price is right. I looked at old photos of steam shovels and derricks that were all operated by cables and thought that a string/cable operated arm would be unique. It would also involve more setup than a typcal servo arm.
Yeah, but what size! Probably fairly heavy. I’d want to use nylon or similar material for the pulleys, and a light weight aluminum frame.
Yes, a steam shovel would be interesting, especially if you actually had it run on steam! (one of my other hobbies).
Alan KM6VV
MarconettEngineering.com
Can you imagine a version of this designed to attach to a standard GHM series motor? I bet you can! 
Something like that could provide some interesting possibilities for propelling a small robot along…
8-Dale