My bike broke in half......

12boy

Über Member
Location
Casper WY USA
Frank, I presume you have read Sheldon Brown on Raleigh 20s? Bitchin rides in there.
 
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FrankCrank

FrankCrank

Professional layabout
Frank, I presume you have read Sheldon Brown on Raleigh 20s? Bitchin rides in there.
....yeah, no worries, I'm a fan of them now for sure. Twenties were Raleigh's best selling bike, there must be so many languishing in the back of garages looking sorry for themselves. It is 2020 after all, so dust off that Twenty and give it a new lease of life - definitely deserves it :notworthy:
 

doginabag

Senior Member
If it is going to fail, it's not an unexpected place for it to happen. When aluminium is welded, it's limit stress reduces to around 50%, depending on the grade.

when you stick a hinge int he middle of a the frame where the bending stresses are at their highest, you will end up needing a tube sizes twice the size of what you would need if the frames was continuous without any welded joints to compensate.
 

12boy

Über Member
Location
Casper WY USA
Here is my Al folder, a Xootr Swift. It's frame is fairly stout and the seat post, which holds it together is fairly thick. Earlier Al Swifts had breaks where the chainstays crossed the seat post and later ones such as mine, have beefier ones. Note the gusset below the head tube/top tube.
This is a very rigid little bike, although the wheelbase is actually the same as many hybrids.
area.
500377
 

Schwinnsta

Active Member
If it is going to fail, it's not an unexpected place for it to happen. When aluminium is welded, it's limit stress reduces to around 50%, depending on the grade.

when you stick a hinge int he middle of a the frame where the bending stresses are at their highest, you will end up needing a tube sizes twice the size of what you would need if the frames was continuous without any welded joints to compensate.
I think it likely that the heat treat takes place after the welding.
 

doginabag

Senior Member
I think it likely that the heat treat takes place after the welding.
It's possible, and maybe more likely in a high end product, but in my experience it's not the norm.

It isn't an issue as long as it is considered during the design, but if there is going to be a failure, the heat affected zone is where you would expect a failure to occur.

Some info and strength tables here, I would expects most bikes are made from a 6xxx grade.
https://www.esabna.com/us/en/education/blog/the-haz-in-aluminum-welds.cfm
 
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