smart51
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| posted on 21/1/12 at 09:50 PM |
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Bending CrMo tube
I'm building a pedal trike and I've bought some lovely CrMo tubing. I'm having a bit of trouble bending it. A while ago I made a
plywood tube bending frame that would put a 250mm diameter bend in 1" tube. I bent some mild tube in it very nicely. It was surprising how
little force it took to bend the tube. Now I've tried to do the same thing with the CrMo but it all went wrong. First it took a whole lot more
strength to get it to go but then it buckled rather than bent nicely round the former. Any tips for making it bend more easily or do I need a
redesign?
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TAZZMAXX
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| posted on 21/1/12 at 10:27 PM |
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I was speaking to a guy at Autosport about this (his company supplies 4130 tube) and he said that it won't bend the same way T45 does, that you
will struggle to achieve a 90 degree bend. Shallow angles are achievable but the inability to properly heat treat the welded fabrication of a space
frame will result in cracks on and around the welds. Apparently, the drag boys don't paint their cages/frames specifically so that they can see
where the cracks appear. What sort of bender are you using? as I suspect you will struggle with anything other than a mandrel bender.
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designer
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| posted on 21/1/12 at 11:43 PM |
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I am afraid CrMo tube is a step too far for the home workshop as, as said, it is very difficult to work with.
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Arnie
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| posted on 22/1/12 at 07:33 AM |
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Bending CrMo tube
Have heard but never tried it myself. Filling up the tube with dry sand then trying to bend it may help. Only a suggestion.
Regards,
Arnie
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clairetoo
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| posted on 22/1/12 at 08:26 AM |
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I used to build drag bike frames from 4130 - I used a record plumbers pipe bender (with a long brace welded across the base and an extended
handle....)
The largest tube was 1 1/4 .062 wall , and that would bend through 90 degrees no trouble - the only thing to watch was the temperature of the former
(too cold and they would split !)
Its cuz I is blond , innit
Claire xx
Will weld for food......
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smart51
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| posted on 22/1/12 at 08:34 AM |
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Sounds like a hasty redesign is needed. Its very strong stuff, though, for thin wall tube.
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