"Yin-Yang" nesting telescoping extrusion 4

[TheTick]

Working on a project that requires a sliding, telescoping element. Tubing isn't quite accurate enough. I'm looking at extrusions. If I can make this work, I can double the volume of ordered extrusion and eliminate one profile...

What I am hoping to find (or design, if necessary) is a shape that can nest and telescope within/around itself, leaving only 1 degree of freedom of axial sliding movement.

Anyone ever see anything like this?

p.s. Yes, I Googled the living snot out of this already!

 

[MikeHalloran]

Two C-shaped extrusions can, I think, be self- conjugate, and nest and slide, but they/it will be torsonally flexible, and you may not want that.

Two extrusions shaped sort of like a lowercase 'a' can, I think, interlock with each other and slide. Because of the closed tube section, they can have reasonable torsional stiffness, but their centroids can't be colinear, so the combined column will have some flex in bending.

I did something topologically similar once, laser- cutting a generally C- shaped detail in the edges of sheet metal components such that the edges could be locked together with a short bolt and fender washers, so I'm sure it can be done.





Mike Halloran
Pembroke Pines, FL, USA

 

[handleman]

I don't know squat about designing extrusion for manufacture, but I was thinking along the same lines as Mike.

Pic and SW Part/Assembly attached.

http://files.engineering.com/getfil...a-0d9e-408a-82e4-b1fc637bad37&file=Assem1.zip

-handleman, CSWP (The new, easy test)

 

[rb1957]

personally (and sorry, tick0 that sounds way too obvious a solution and there must be something that precludes it ?

 

[ornerynorsk]

You may find that tubing can be made more accurately than an extrusion. Extruders always talk tough, but few are willing to be held to tolerances less than half of association tolerances.

 

[btrueblood]

Stars for Mike (concept) and handleman (pictures), short and sweet answers.

 

[TheTick]

Zowie! Double down on the LPSs. Much more elegant than what I was dreaming up!

 

[TheTick]

The grand prize goes to anyone who can find this in a catalog of existing profiles.

 

[mcgyvr]

aluminum extrusion dies are cheap... whip up your own shape and get a quote.

 

[btrueblood]

...or many quotes.

 

[DesignerGuy16]

I used to work for a company that designed and built aluminum extrusion dies. It's really not bad. Problem is with an exotic "yin & yang" type shape you may get some twist over a long extrusion.

Take a look at telescoping drawer slides, maybe that might give some idea's about holding a nice tight tolerance torsionally that gets away from the traditional extrusions, or it may just be a different style than what you're thinking.

Without knowing your application or seeing concept sketches I can only guess about a better way.

James Spisich
Design Engineer, CSWP

 

[EspElement]

Maytec makes this as an assembly. It uses pads on the inside to guide the inside extrusion

 

[GregLocock]

You'd probably halve your tooling cost if you eliminate the small triangle, and make the central circle a curly teardrop. Won't be as torsionally rigid.

Cheers

Greg Locock

I rarely exceed 1.79 x 10^12 furlongs per fortnight

 

[TheTick]

Quotes are easy enough to get. Having one common extrusion instead of two really helps.

Still, management gets shy about tooling cost. Anything off-the-shelf really helps.

Honesty may be the best policy, but insanity is a better defense.

http://www.EsoxRepublic.com

-SolidWorks API VB programming help

 

[iainuts]

Square telescoping tubing?

http://www.google.com/search?hl=en&q=square+telescoping+tubing&aq=f&aql=&aqi=&oq=

 

[dvd]

Another telescoping tubing vote:

http://www.unistrut.com/literature/index.php?doc=Telespar&pg=1

 

[MikeHalloran]

The 'a' could also be roll-formed from steel in large quantities.

In small quantities, it could be press-brake formed, but you'd need some tooling like that made for pressing hinge knuckles. To restore the torsional stiffness lost that way, you could stitch-weld it, where the triangle in the extrusion is, or laser-cut the blanks with rectangular slots there and mating tangs on an edge, in which case closing the knuckle would also engage the tangs in the slots. It's scary tinwork, but it can be done.



Mike Halloran
Pembroke Pines, FL, USA