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Bending square aluminum tubing

acam37

Well Known Member
I am looking for someone near me that can bend a radius in square 3/4? tubing? I have been to every machine shop and metal fab shop in East Texas and no one has a tubing roller capable of bending square tubing. I tried a few tricks of hand bending around a jig and all I got was ruined tubing. I?m building a RV-4 fastback canopy from scratch and this is the last piece I need before calling the tig welder. I?m out of options.
 
That is tough to do a good job on. When bending square tube the outside of the bend is stretching and the inside is squishing. Sometimes if it is not controlled the outside stretches more than the inside squishes or vise versa resulting in a week structure. Have you tried to bend some yet? You might be able to learn to do it if you do not mind making some scrap. Good luck and let us know how you do it.
 
It's 3/4 x 3/4 .062 6063 T52. The radius has to follow the profile of the instrument panel.
 
What's the center line radius of the bend? I'm guessing it is fairly small.

You need special dies machined for square tubing. Swag Off Road sells them. Their dies work with their rollers and with the Harbor Freight tube roller.

http://www.swagoffroad.com/SWAG-Tub...ble-With-Harbor-Freight-Tube-Roller_p_51.html

They also sell their own brand of tube rollers, but it's a large investment for rolling one piece.

I'd give them a call to see if they think the bend would be possible using their dies, but they'll ask you the center line radius.
 
I think it can be done by hand using wood forming blocks, of course there will be trial and error. It might help to make the inside forming block slightly convex so it will compress the middle of the tube in and give the metal somewhere to go on the inside of the bend instead of buckling, you wont have straight square sides all around. Thicker tubing will help for sure and possibly making sides on the form to reduce the sides of the tubing from ballooning out. I work in an aluminum fab shop and have been amazed at the stuff we have bent by hand, it is of course an art and can be very frustrating.
 
To do it right you need a roll bender with dies for .750 square tubing. Your bend radius should not be less than 4 times the OD of the tubing, in your case 3". Remember that's radius. You need dies so the sides of the tubing stay square to the top and bottom, the radius restrictions are there to limit the stretch/squish previously alluded to :)

This is not to say that you cannot get a good job over your knee. Your best chance to find a shop with this equipment is someone that makes specialty stuff like race car chassis, boat folding awnings, etc. Your typical local fab shop will not have it.
 
David makes a good point, but if your dies restrict the expansion in the outward direction there is little place to go except in. Keep in mind that this inward collapse of the sides of the square tube makes it a lot more difficult for the tube to resist future bends in either direction. A rule in the race car fabrication world is square tubing for straight runs and ease of interface with most everything else, round whenever the slightest bend is necessary.

I assume round tubing will simply not work for your application?
 
Thanks for all the good info and advice. The problem I have is that I don't want to spend $500 to bend a $5 piece of tubing. I guess I can call Vans and find out who makes the RV-4 canopy frame and send them a template of my instrument panel.
 
It's 3/4 x 3/4 .062 6063 T52. The radius has to follow the profile of the instrument panel.

Are you sure you want to use that alloy and heat treatment? It's a lot weaker than 6061-T6, by approximately half. And welding it will only reduce its already small strength.

That said, it'll be easier to bend, too, since the yield strength is so much lower.

Wicksaircraft.com sells that size of 6061-T6 square tube. It's part number SQ3/4X065-T6. With this, it would be better to put it into the -0 condition and bend it, and then re-heat-treat it.

Dave
 
That tubing material came straight off of my kit plans. That's what they use on the standard canopy frame. With that being said, if I cant find someone that can make this happen I will use round tubing. It will work just as good, but I was wanting to stay true to the original frame as possible. I don't have the stock canopy or I would just cannibalize it like Axel did when he built his fastback -4.
 
Have you tried packing the inside of the tube with sand, welding the ends shut, and then hand bending it around a wooden form? Because of springback, it may take a few tries to figure out the wood form radius. I would try this with a 4-5' foot piece of material so you got a long enough lever.
 
Call Me

Arlie - Give me a call (if you want) and I'll tell you my experiences with what you are considering. I did my HRII back in 1997 and my RV3 about two months ago - both with acceptable results.

David Howe
1 (559) 816-0433
 
Arlie---check with some race care fabricators. Some of the larger one may have the square tube dies needed and can make this for you.

Tom
 
Another option would be to fabricate the tube. Cut two profiles out of sheet, then use some bar stock or cut sheet for the top and bottom. Weld it all together. A lot of welding, but may come out better in the end if you can't get the right bending tools.
 
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