Bicycle Mechanics - Looking for thoughts and advice on bending/realigning ALUMINUM rear stays...

I've got a new aluminum cyclocross frame and somehow in shipping or transport the stays were pinched so that the spacing between the rear dropouts is only about 80mm. I would like to save this frame and build it up as a city bike/commuter/fire road...etc. bike. I got the frame for $0.00 and there is no possibility of a warranty or getting it replaced so I want to try spread it to fit a 130mm wheel.

I have heard that it is not safe to cold set aluminum, but I have done a lot of searching and have read testimony of a few different people who have bent damaged aluminum stays back into alignment and then ridden the bikes for years without issue.

There are no sharp bends or creases and if you didn't know any better you would think the spacing is suppsoed to be so narrow. Because of this, I think there might be hope. I'll try to get some pictures up later.


How should I go about it? Sheldon's 2x4 method for steel frames?
Would applying heat help or would that weaken the frame? I've read up on re-heat-treating 7005 aluminum but haven't come to any conclusions as most of the stuff I've found is technical.
How about using some threaded rod with a nut on each end and gradually expanding them to 130mm? Maybe same concept with a vice?

If you know someone with a mini-jack... heh. I wouldn't heat it up, the re-treating and painting will cost you more than a new frame, I'd reckon.

If its new, get a replacement from the seller.

Uhmmm...50mm, that's quite a bit to bend it back to. I know that you said that the bend is not a sharp kink, but is it concentrated at short legnths of the stays? It will make it more questionable if you should bend it back if it is compared to a bend that was more gradua,l along longer legnths of the stays. I think that would be the deciding factor. if an attempt should even be tried.
Like you said though, the general rule out there is Al frames should not be cold set, so I suspect that you are on your own caus I think that all responsible bike shops and frame builders will not even try to fix it too.

Chombi

The issue is that aluminium gets very brittle when you bend it. For example motorcycle brake and clutch levers very happily bend in a fall to an almost crazy degree. But if you try to straighten them without annealing the metal they will snap like cheap glass. One bend to the customer. And your frame got the one and only allowable bend during shipment.

In your case without knowing the type and heat treatment level of the alloy used for the bike your best bet would be to toss it. You MAY be able to bend it back and ride it for years. But it could just as easily fail during bending it back or your first ride down a hill. Or possibly annealing it would allow you to bend it back. But if it isn't one of the metals that returns back to its original heat treat level after some days following the annealing (yes, that's right. It "heals" itself. A fact that a buddy in the aircraft remanufacturing business put me onto) then you may anneal it to allow it to be corrected but it may not go back to being springy and tough in which case even a stand up and mash on a hill may well make it fold up into a pretzel. There is just too many unknowns with aluminium to tell for sure without proper expert advice from a frame guy that knows his alloys and heat treatment peculiarities of the various tube sets.

what do you mean by annealing?

I'd use sheldon's 2x4 method in order to evenly re-space the dropouts, though you'll need to determine how offset they are from the original bending. It's unlikely that they will explode during use, rather they will crack as you attempt to bend them, if anything. Or they may develop a crack during use, which could leave you stranded somewhere.

I guess it depends on if you are committing any money to the buildup that you would not be spending anyway. IOW, doing the build up anyway with a different frame.

To address a few points:

Clasher - I would like to try re-heating and repainting myself, so cost would not be an issue. (frame is flat black too...so I would just have to do the stays).

San Rensho - I got the frame for free out of the trash, no replacement possible.

Chombi - You can't even tell it is bent. It just looks as if the spacing was supposed to be 80mm.

BCRider - They alloy is 7005. Any guess if it would be possible to 'anneal' that alloy?

rogerstg - I have all of the parts to build it up, and if this frame breaks I will try to source another frame to build with the parts.

what do you mean by annealing?Heating it up to just under the melting point. Can be done with steel easily because you can judge the temperature by the glow intensity. But with aluminium it doesn't change color and one moment it's solid and the next you have a molten puddle. I guess you can use an infrared thermometer and monitor temperatures as you heat it.

For the OP, I say scrap the frame and get a new one. It will most likely snap as you try to bend it back. And you'll probably need to widen it to 150mm in order for it to spring back to 130mm. In effect, you are overcoming the material's yield-strength twice. The 7005 alloy is stronger than the usual 6061-T6, but once you go over it's yield, it's still very close to collapse anyway. Not a good idea with either alloy since there is no fatigue-limit. There's very little life left.

Here are some pictures. I tried different angles to give a good perspective.
It looks to me like the stays themselves are bent very little and that most of the bend is in the dropouts themselves.

http://i733.photobucket.com/albums/ww335/telepciaka/IMG_0617.jpg
http://i733.photobucket.com/albums/ww335/telepciaka/IMG_0620.jpg

http://i733.photobucket.com/albums/ww335/telepciaka/IMG_0622.jpg
http://i733.photobucket.com/albums/ww335/telepciaka/IMG_0615.jpg

This last shot shows me spreading them to 130mm with an old axle I had. Went out to 130 easy, but sprung right back down to about 80 when I took it out. I think I'll do a little more reading about heating, annealing and bending. I've got nothing to lose...other than it catastrophically failing while riding, but that is unlikely. If a crack develops while bending I'll scrap it. And if I do get to ride it I will inspect it regularly.

You can cram a 130 axle in , ride it till it fails, next time have them put an axle in the frame before they ship it.
I bet there was nothing in the dropouts to prevent them from getting crushed, even a block of wood will be better.

how the hell did you get a frame that nice out of the trash????

You can cram a 130 axle in , ride it till it fails, next time have them put an axle in the frame before they ship it.
I bet there was nothing in the dropouts to prevent them from getting crushed, even a block of wood will be better.


how the hell did you get a frame that nice out of the trash????

The frame was not shipped to me and damaged en route...it happened to somebody else and there response was to strip it of all its parts (everything) and toss the frame. I then adopted it :)

This is a trick from my aircraft sheet metal fabricator buddy. They use it when custom deep shaping panels for cowls and the like to avoid stress cracking from overworking the metal. I've used it on clutch levers and a shift lever for motorcycles but have not had the guts to try it for brake levers for obvious reasons.

Danno, in this case you don't heat it to almost melting. Come to think of it bright cherry red is a long way from melting for steel as well but that is the anneal color for steel.

Anyhow, back to our aluminium. To anneal the part you need a candle and a propane torch. Or if you're a welder just an oxy-acetylene rig. Use the candle or a smoking flame to carbon blacken the aluminium so it is nice and sooty. This is your tracer marking that will tell you when the metal has been hot enough for long enough. Now use the propane torch or open up the oxygen to get a nice clean flame. Heat the part up evenly and as it comes up to the annealing temperature the blackening will begin to thin out. Keep heating it evenly all over until the black is gone and it is again silver. At this point you can let it cool slowly or you can dunk it in water to cool it quickly Although for a big thick forging this would cause some internal thermal stress but nothing we use on bicycles is that thick other than perhaps a crank arm. The aluminium is now annealled for some period of time. With 6061-T6 he told me that I had from 2 to 4 hours depending on how much it was worked. Serious forming would, of course, work harden it sooner. With non T rated metals that are not heat treated they stay annealed until work hardened again. I laughed and asked him what they did to the metal to make it "heal from the burn" and he just shrugged and said it was something about these metals and the way they are heat treated that restores the original heat treatment state after a few hours. He didn't know why but he knew that it works. I was able to bend some brackets for a project from 6061 T6 without cracking it. When I tried this with a piece that was not annealed even with a generous bending radius it snapped like a candy bar. To satisfy myself about all this I also made and bent an extra bracket and two days later I tried flexing it. The metal had restored its toughness and stiffness to bending and was, as far as my simple test went, as strong as it had been before I annealed it.

Now as to the frame. All aluminium alloys work differently. Your frame may or may not anneal this same way. The information I got about this was for 6061 alloy. And if there is one thing I know it is that aluminium alloys are very fickle. Your 7005 may not work the same way at all. I just don't know enough about 7005. And if it does I don't know if it will "heal" itself back to the original temper level if the metal has one. So your stays may remain softer than they are now. Hopefully someone that knows their bike frame alloys will come along and comment more on this for you.

I think you should ship it to me with a declared value of 2000 then we will put a claim in with UPS. I'm wondering if there is any way to send it back to felt to.get it fixed, even if they charged you a small amount, it could be worth it.

I think you should ship it to me with a declared value of 2000 then we will put a claim in with UPS.

Is this supposed to be a joke, or are you really advocating fraud?

I think I'd go along with the recommendation to stuff a 130 hub in there and just ride the thing.

Is this supposed to be a joke, or are you really advocating fraud?
Advocating fraud. OP send it my way please, while your at it, declare the value at 5000 so we can get 2 new bikes out of the deal.

There are no aluminums that heal themselves.There are some that will work harden,but NONE will magically come back to temper sitting on a bench.If you don't believe me,heat up some 6061 T-whatever for different times and let it cool, then do a rockwell test on it and see for yourselves.

Applying a thin coat of soot,then heating it until it's gone will get you in the 375-425 range.Your going to have to hold that temp for about 10-20 minutes if you actually want to anneal it back to dead soft.Otherwise you are just reducing the temper,not removing it.

You do not want to remove all of the temper,it will be too soft.The axles will chew the living crap out of the dropouts.

If this was mine,I would use a heat absorbing gel on the seat and chain stays to localize the heat zone to exactly where I wanted the bends.I would straighten the dropouts first and see where that gets you.If that didn't cure it,I don't think it will,I would brave the stays.

Your on your own trying to widen the stays.If a tube doesn't collapse on you,you have a chance.Good luck,hope it works!

There are no aluminums that heal themselves.There are some that will work harden,but NONE will magically come back to temper sitting on a bench.If you don't believe me,heat up some 6061 T-whatever for different times and let it cool, then do a rockwell test on it and see for yourselves.

Applying a thin coat of soot,then heating it until it's gone will get you in the 375-425 range.Your going to have to hold that temp for about 10-20 minutes if you actually want to anneal it back to dead soft.Otherwise you are just reducing the temper,not removing it.

You do not want to remove all of the temper,it will be too soft.The axles will chew the living crap out of the dropouts.

If this was mine,I would use a heat absorbing gel on the seat and chain stays to localize the heat zone to exactly where I wanted the bends.I would straighten the dropouts first and see where that gets you.If that didn't cure it,I don't think it will,I would brave the stays.

Your on your own trying to widen the stays.If a tube doesn't collapse on you,you have a chance.Good luck,hope it works!

So you are saying I don't want to remove all of the temper because it will make the DO's too soft, but that I should apply some heat? Any advice on how to go about it for somebody with zero experience doing such a thing?

And also, if I remove all of the temper (20ish minutes at 400 degrees) then the alum. would be soft and no good? Is there a way to re-heat-treat it or would I then be SOL?

The act of moving the metal work hardens it again.

Solution heat treating is probably way out of the shade tree capabilitys.

SNAP!....sigh.

The good news is that I have it spread to 130mm exactly and a wheel sits 100% straight in the frame.

The bad news is that both seat stays cracked right under the brake bridge. I tried the 2x4 method and very very gradually applied pressure. It flexed a little then I eased up and it went back down to where it was. I tried again, still gradual and SNAP. Just for grins I tried the same thing on the other side only more gradual and ended with the same result.

I might try to weld the cracks and use it as a beater frame but I already ordered a replacement frame. The new one is nashbar and not Felt though. I'm sure the end result will be fine.

http://i733.photobucket.com/albums/ww335/telepciaka/100_0729.jpg

Well, I say you recycle it into a six pack and if a Neal comes along, tell him to buy his own...

If you pay a good welder with a TIG torche to weld that up for you, you'd still be ahead. Would cost about $75-100, maybe less with his favourite 6-pack and pizza thrown in.

The other thing I was going to say before the crack was to simply spread it out by hand to fit in a 130mm wheel each time. But don't try to cold-set it.

Get out the hacksaw , and cut it up for scrap.

If you pay a good welder with a TIG torche to weld that up for you, you'd still be ahead. Would cost about $75-100, maybe less with his favourite 6-pack and pizza thrown in.

The other thing I was going to say before the crack was to simply spread it out by hand to fit in a 130mm wheel each time. But don't try to cold-set it.

I might be able to get it welded for free...that is what I'm going to try next.

One stay was bent more than the other so it wouldn't have been straight. Also, I tried to spread it but could only get it to about 120mm or so by hand. With a vice I could spread it to 130 but there was no feasible way to stuff a wheel in there...and if I ever needed to change the wheel or had a flat or something I would need my vice to get the wheel out!!

Well, this proves the rule of thumb about "one bend to a customer". But I'm still sorry to see the ending come out like this.

Booger, the claim that the temper restores itself came from my buddy in the aircraft industy. Maybe it comes back due to working the metal. I don't know. I DO know that the spare angle bracket that I bent up was back to very tough and springy and not at all soft like it was when I bend it following the annealing process. It may have been the act of bending it that toughened it back up, I don't know enough about it other than what my aircraft metal guy told me and my own results that seem to go counter to your information.

Booger, the claim that the temper restores itself came from my buddy in the aircraft industy.I think that's correct for 6061 depending upon which temper is desired. Normal precipitation age-hardening takes place over the course of several weeks and brings the material up to a T3/T4 temper. There are post-weld processes like quenching that generates this temper quickly. To get T6 temper, you need to do a solution heat-treatment at around 450C for a couple hours to dissolve some of the previous precipitation.

Danno, that sounds about right. And the material I got from him courtesy of their scrap box was 6061 in either T4 or T6 temper.

Either way a lot of the temper was restored even after just two days. Likely the restoration is on a exponential curve sort of basis where the first part of the return is quick while the last bit takes a while.


For those wondering the actual annealing is good for any sort of work hardened aluminium. While much of the last couple of posts has been about the aircraft sheet metal I also had good luck with straigtening forged aluminium clutch levers using the same carbon and anneal process. I've done three levers using this method now and all worked well for as long as I owned the bikes afterwards.

I also used this trick while workng on making an aluminium bowl from some .050 alloy to try out some autobody metal forming hammers. I was able to hammer stretch the metal into a mixing bowl like form of about 6 inches diameter by 2 inches deep using the hammers and some soft wood as an anvil. I carboned and re-annealed the metal twice during this process.

and on the motorcycle adage, having raced motorcycle and turfed myself off them at varying speeds up to around 100mph, the idea of using a bike frame that was "maybe" ok after being put back into shape would certainly make my pretty darn uneasy.

this was a very interesting read, but 4stars, Im glad in a way that it ended like this and that you will be going with a new frame. I dunno, the idea of a "perhaps" sudden event, even if it wasnt a total failure, but could cause a weird swerve or rear lock up, is not something I would want to have happen. (but I completely understand trying to see what could be done with this)