I am trying to make an arm the extends out of nested square tubes. I was excited to see that McMaster sells 1-3/4X1-3/4X1/16wall Square Al tube:
6546K7 Multipurpose 6061 Aluminum Rectangular Tube 1/16" Wall Thickness, 1-3/4" High x 1-3/4" Wide
But, no joy, 5-7week lead time.
Does anyone have a source for this tube? I don’t care about 6061 vs 6063 or whatever for my application, Aluminum is Aluminum is Aluminum.
Thanks,
Joe J.
I wasn’t able to find any from a quick search of local retailers or anything online. Sorry. Good luck in your search.
Online metals has 1.75"x1.75" 1/8" wall if that helps.
Metal supermarket carries it.
Edit: Oops, sorry, that is 1/8" wall.
Edit2: If you don’t need the strength and if machinability is not critical, Metal supermarket does carry 1.75" x 1.75" x 0.065 in 6063-T5 alloy.
6063 is perfectly fine. Strange that that particular flavor of tube is only available for in bricks and mortar locations, and can’t be ordered online. But, there is a location not too far away, I’ll call them tomorrow. If they have it, I’ll figure out how to pick it up.
Thanks a ton.
Joe J
Alcobra has telescoping tubes that we are using for our climbing structure. Turnaround is about 4 business days.
Oooh, a telescoping elevator?
are those going to slide on themselves or with bearings?
We are using cf springs to power them out. No bearings.
I can’t wrap my head around this, how are you using CF springs to extend this?
This looks heavy, is it 1/8" wall on all of those or is my scale perception just off?
This is a similar concept to 33’s climber in 2016. I don’t have any pics on hand but you can look around on TBA and do some CD searches to find stuff.
Basically the CFS drum is mounted to the top of the first stage and the tail is mounted to the bottom of the next moving stage. This means the CFS wants to retract, pulling the bottom of the moving stage to the top of the previous stage.
If you get your tube sizes and wall thicknesses right, you can have the CFS go in-between the ID of the first stage and the OD of the next stage, keeping things very compact and light.
Do you intend for the aluminum walls to run against each other under load?
Nick is not only correct that this concept is similar to 33’s, it is based on the designs of teams 33 and 2056. In order to have enough space to insert the CF springs into the tubes we are milling two parallel sides on each (interior) tube. They are currently 0.11" thick, and the parallel sides are being milled to 0.05" thick each. On the non-milled faces, the gap is large enough that we will put a piece of Teflon tape at the top and bottom of the tube on each side, preventing aluminum-on-aluminum contact.
I think I posted a chart of CoF for aluminum on aluminum when we were discussing robots sliding during hang…but I can’t find the picture now. It was very reassuring, assuming we use an aluminum hook. But it’s very scary, if one intends aluminum parts to move inside other aluminum parts.
I would be very concerned with the aluminum galling
I understand what you’re doing with cf springs but I can’t understand how you’re gonna attach the spring to the tube. You can use a rivet but then the head is gonna scrape against the tube that tube is sliding inside of. If you countersink it, you have to countersink the cf spring and wouldn’t that cause the hole to get too big reducing the holding power?
Aluminum+Aluminum+Motion=BAD!
Even with lube it is still bad, only a matter of time before it seizes up. Nearly cost us getting to Einstein in 2014.
This. At a minimum I’d expect to see at least a UHMW-PE tape in between the sliding aluminum members, such as this:
https://smile.amazon.com/TapeCase-423-5-UHMW-Tape-Roll/dp/B00823JEUO
