Dyne's Treadwell

[Dyne]

I think it's awesome you're planning on releasing plans. Can't wait to seem 'em

It might be awhile before I finalize anything enough to actually release any plans, but yeah.  One of my goals is to document stuff enough to take out some of the unnecessary guesswork and hopefully encourage more Treadwell builds.


Pondering the telescoping neck mechanism.  There are several ways to go about it, but here's what I'm thinking...

The physical neck is mostly decorative (and hollow).  It might be made of short overlapping sections, or a few longer subsections that connect (if I went with aluminum pipe, I would probably do the former for cost, as shown here).




Either way, inside the physical neck there is a long hollow 1/2" shaft attached to the pistoning section of the neck.  If it were made of PVC, then the 0.8" OD of 1/2 inch PVC would just barely fit within the lowest and thinnest section of the neck.  If it's aluminum tube, which is still fairly cheap, then a couple of 1/2 ID bushings would be used to center it, and that's what I've modeled for now.  These would allow the shaft to both slide vertically (to raise and lower the head) and rotate around its axis (to turn the head).






The shaft has a slip ring at the bottom end (for the head tilt servo -- the arm wires don't need it). I know the original uses a slip ring at the top, but it makes more sense to me to put it nearer the point of rotation. The slip ring rests on a sandwich of two washers (I didn't bother to model these) with a thrust bearing in-between, something like McMaster-Carr 5909K24, which sit on the lift platform.  The washers are because the lift platform and slip ring flange wouldn't be precision surfaces.

This entire assembly can then be raised and lowered by some mechanism, be it a linear actuator like I was thinking upthread, a crank shaft powered by a wiper motor, or -- as I have it here -- a lead screw.  There should also be something to keep it reasonably level (which I haven't modeled yet, but could be something simple like a pair of drawer slides or even 3d printed rails).




The thrust bearing is there so the shaft can also be rotated by a friction wheel (similar to how R2's rockler is turned by a small wheel, at least on those that aren't using dome gears).  Thus, the head is both lifted and rotated via the same shaft.  This wheel and motor would probably be mounted in the region shown below, under the top plate of the logic housing between the two bushings.




I'm thinking I would probably need some form of omni wheel there to allow the shaft to slide vertically when the friction wheel isn't rotating.


Yeah, it's possible to raise and lower the head with a coaxial lead screw, but then rotating the head and routing the wires becomes a bit harder.