James
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 posted on 1/8/02 at 04:48 PM |
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Bending square tubes
Is it possible to bend square tubing using the: fill with sand, stuff ends with rags then heat and bend method?
Or will it distort significantly?
If that's not possible, does anyone know how MK do their's?
Thanks,
James
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theconrodkid
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| posted on 1/8/02 at 05:21 PM |
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I think its done in a machine,easier to cut into the sides of the tube,bend and re weld
ps precky sunday? 
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jimmy
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| posted on 1/8/02 at 05:42 PM |
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James,
Try this www.tubela.com.
Bet thats how MK do it. 
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Alan B
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| posted on 1/8/02 at 07:07 PM |
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quote:
Is it possible to bend square tubing using the: fill with sand, stuff ends with rags then heat and bend method?
Or will it distort significantly?
If that's not possible, does anyone know how MK do their's?
Thanks,
James
James, nice idea but won't work very well. The theory behind sand stuffing is for the tube to keep it's cross-section, and most cross sectional area
you can have for a given perimeter is a round section, so any distortion of the perimeter shape would have to compress the sand, which is difficult if
jammed in tight. However, this is not true for square and it will tend to distort into a less dense arangement. That is why square tube has to have
external support around the section while bending, a bit like Ron shows in the screen section bender.
Hope that helps,
Alan
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merkurman
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| posted on 1/8/02 at 11:30 PM |
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one thing I have seen is diy hydraforming...this guy got a pressure tester for comerical pluming (rented) that is a hand pump for like 1500 psi, he
welded up a flat stock exspansion tank for a dirt pipe with a bung on one end then pumped it up into shape. he use a hammer to kinded help shape it.
I could see where a sinilar setup could work. bend tube with heat then "inflate" it.
nick
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locodude
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| posted on 2/8/02 at 05:15 PM |
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Hi
When MK bend sq section tubing it is done on a machine but even then the inside of the bend kinks into the tube so you don't get a true bent sq
section if you know what I mean. Still looks nice though.
Chris PTM
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Alan B
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| posted on 2/8/02 at 06:08 PM |
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Chris, FYI it's more than likely that the MK bending inside die/former has a deliberate ridge that forces the inner face to go inwards in a
controlled fashion, seeing as the kinking of the inner face is unavoidable. IIRC the procedure is called "crush bending", you see it a lot on bent
square tube furniture.
It's about 15 years since is was involved so my recollection may be a little hazy
Have a look next you see Martin, if only for my sanity  
Cheers,
Alan
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