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Spread dropouts while frame is baking -- what do you think it will do?

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Spread dropouts while frame is baking -- what do you think it will do?

Old 01-16-11, 12:32 PM
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Don in Austin
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Spread dropouts while frame is baking -- what do you think it will do?

Monday UPS should bring me an EBay used RedLine Team Conquest cyclocross frame -- aluminum/scandium alloy. Its going to receive a Shimano Alfine 11 speed hub. There is a dropout discrepancy in that the hub is 135 mm and the dropouts 130. I am not too concerned about this in that I checked all the various frames on my other bikes and they can all be sprung open more than 5 mm by hand. However, I am going to have the frame powder coated which process involves it being baked at 400* F. So I though I might as well put an old axle with nuts on it in the rear dropouts to hold them to perhaps 140mm.

When I get the frame back and take the axle out one of three things will have happened:

--Nothing, springs right back to 130mm. I consider this likely.
--Springs back only partially so now its real close. I consider this possible.
--Stays at 140mm and will need thin washers. I consider this unlikely.

What do you think?

Oh, as a final note, if I can shave a couple of mm off of the locknuts or spacers on the hub I will probably pass on the experiment, but I haven't got the hub yet to know if this is possible. Should get here before the frame.

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Old 01-16-11, 01:01 PM
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you forgot the possibility that a weld will crack or the dropouts bending
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Old 01-16-11, 01:17 PM
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I'm going to vote for either nothing or frame damage.

I don't know anything about Al/Sc alloys, but 400 degrees F is not a lot of heat metallurgically speaking. If it were enough to soften the metal, I would be frightened to powder coat at all, as this would probably anneal the desired strength out of the metal. Many modern metal alloys are out of equilibrium when they have their desired properties. That's why they need complicated treatments - heat treat, quench, temper, etc. - to work correctly.

I often machine aluminum at work, and from what I've seen of it, it doesn't retain much strength once bent. I seriously hope that you can work down the OLD of the Alfine and get by springing the triangle open a few mm if at all. I strongly recommend against pushing the triangle open to 140mm.
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Old 01-16-11, 01:52 PM
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*Solution heat treatment is above 400 degrees, (I think)
then* the metal is just short of melting,so gets stress relieved..

I would look for an axle spacer substitution
on the hub .. to make it fit the frame, as it is .

IG hubs often have a left side that can be adjusted in that way..

Last edited by fietsbob; 01-16-11 at 02:21 PM.
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Old 01-16-11, 02:07 PM
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Anodizing can crack above 80C, so if you have any, beware.

Aluminium should never be bent like steel can be - it will weaken substantially.
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Old 01-16-11, 02:27 PM
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Originally Posted by FLYcrash View Post
I'm going to vote for either nothing or frame damage.

I don't know anything about Al/Sc alloys, but 400 degrees F is not a lot of heat metallurgically speaking. If it were enough to soften the metal, I would be frightened to powder coat at all, as this would probably anneal the desired strength out of the metal. Many modern metal alloys are out of equilibrium when they have their desired properties. That's why they need complicated treatments - heat treat, quench, temper, etc. - to work correctly.

I often machine aluminum at work, and from what I've seen of it, it doesn't retain much strength once bent. I seriously hope that you can work down the OLD of the Alfine and get by springing the triangle open a few mm if at all. I strongly recommend against pushing the triangle open to 140mm.
I can take any of my frames and open them up 10mm by hand. I don't think its that much.

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Old 01-16-11, 02:30 PM
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Originally Posted by Bianchigirll View Post
you forgot the possibility that a weld will crack or the dropouts bending
Without heat its nothing to spread a frame that much -- or more. I can do it by hand. I would use large flanged nuts on either side of the dropouts to maintain alignment.

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Old 01-16-11, 02:45 PM
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Heat treatment of aluminum alloys varies widely but much of it is conducted at fairly moderate temperatures. "Aging" in particular is done at well below 400°F. So saying "400 degrees F is not a lot of heat metalurgically speaking" can be very incorrect with aluminum alloys.

Since the frame was likely heat treated and stress releived by the manufacturer after fabrication and welding, I don't think it's a good idea to subject it to that much heat unless you know for certain you won't alter it's properties. I don't think you know that and I would certainly rethink powder coating it with a process that requires that high a temperature.
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Old 01-16-11, 02:48 PM
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Originally Posted by HillRider View Post
Heat treatment of aluminum alloys varies widely but much of it is conducted at fairly moderate temperatures. "Aging" in particular is done at well below 400°F. So saying "400 degrees F is not a lot of heat metalurgically speaking" can be very incorrect with aluminum alloys.

Since the frame was likely heat treated and stress releived by the manufacturer after fabrication and welding, I don't think it's a good idea to subject it to that much heat unless you know for certain you won't alter it's properties. I don't think you know that and I would certainly rethink powder coating it with a process that requires that high a temperature.
That's pretty much standard procedure for powder coating. Powder coating aluminum bike frames seems to be very commonly done with no ill effects.

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Old 01-16-11, 05:44 PM
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Originally Posted by Don in Austin View Post
That's pretty much standard procedure for powder coating. Powder coating aluminum bike frames seems to be very commonly done with no ill effects.

Don in Austin
Yes, but the coating is done by the frame manufacturer who is aware of it's thermal history and take the baking process into account.
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Old 01-16-11, 06:03 PM
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+1 I'd be concerned about the effect of the heat.

+1 I think the 140mm spindle is a bad idea.

+1 You should be able to get that hub down to 130mm without trying too hard.
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Old 01-16-11, 08:12 PM
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I've heard you can respace the alfine to 130mm, have you searched the IGH yahoo group? I'm sure there old posts about this.
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Old 01-16-11, 08:42 PM
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Offhand, I think I'd cold set the frame to the right width & square the dropouts. Then fixture it there while baking in hopes of getting some degree of stress relief.
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Old 01-16-11, 09:08 PM
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Originally Posted by HillRider View Post
Yes, but the coating is done by the frame manufacturer who is aware of it's thermal history and take the baking process into account.
I was referring to custom powder coating frames post-manufacture. As well as automotive wheels and all kinds of motorcycle parts -- many structural.

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Old 01-16-11, 09:12 PM
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4oo degrees is Pizza temperatures.. happens, I suppose, to be the melting
point for the polyester powder. too.
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Old 01-16-11, 10:38 PM
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Originally Posted by fietsbob View Post
4oo degrees is Pizza temperatures.. happens, I suppose, to be the melting
point for the polyester powder. too.
Not much of a pizza oven if only 400*. Serious pizza oven is 600* or more.

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Old 01-16-11, 11:26 PM
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Anyhoo Don , alter the hub not the frame.
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Old 01-17-11, 01:07 AM
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The melting point of AL is about 1220 F. You are not not going to get the frame to take a set with 400 degrees. An AL/SC alloy has very similar properties to 7000 series AL, but has about 10% more yield strength.

As fietsbob said, alter the hub, not the frame. You could take the nuts securing the hub shell to the axle to a machine shop and have them reduced 2 to 3 mm each in thickness for very little cost.
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Old 01-17-11, 01:16 AM
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My money's on an easily-removed 5mm spacer doing the trick
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Old 01-17-11, 05:54 AM
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Originally Posted by FBinNY View Post
Offhand, I think I'd cold set the frame to the right width & square the dropouts. Then fixture it there while baking in hopes of getting some degree of stress relief.
This isn't a steel frame. Aluminum doesn't have the ductility of steel, any steel. You run the risk of ruining your frame. Check out Sheldon Brown, and other experts on line. Or (rather, AND) go to someone who actually practices frame building, and ask if they will cold set your rear end as you ask. If they won't, ask why. If a real expert (Dave Kirk for example, or Tom Kellog) is not comfortable cold-setting your frame, you shouldn't be comfortable doing it yourself.

Don't just believe a bunch of Internet chatterers. Some of us know a little bit, and some of us don't.
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Old 01-17-11, 06:17 AM
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Originally Posted by Road Fan View Post
This isn't a steel frame. Aluminum doesn't have the ductility of steel, any steel. You run the risk of ruining your frame. Check out Sheldon Brown, and other experts on line. Or (rather, AND) go to someone who actually practices frame building, and ask if they will cold set your rear end as you ask. If they won't, ask why. If a real expert (Dave Kirk for example, or Tom Kellog) is not comfortable cold-setting your frame, you shouldn't be comfortable doing it yourself.

Don't just believe a bunch of Internet chatterers. Some of us know a little bit, and some of us don't.
I did read Sheldon Brown. What I am doing is not remotely the same as the cold setting process he describes. The cold setting process involves prying the dropouts with 2x4s or similar for leverage to the point where they are altered. To do that the dropouts would have to be pryed probably an inch or two. Spreading 10 mm is no further than can be done by hand easily as I have checked on multiple frames. If they relax opened up a little while baking that will NOT be cold setting. I think the most likely scenario is I take the spreader out when the frame comes back and it will be unaltered. The other likely scenario is that when the hub gets here I will find 5mm I can remove from it and the discussion becomes academic. Yet another scenario is that when I precisely measure the hub and the frame the interference will be some number other than exactly 5mm -- hopefully less.

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Old 01-17-11, 06:21 AM
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Originally Posted by MikeWinVA View Post
The melting point of AL is about 1220 F. You are not not going to get the frame to take a set with 400 degrees. An AL/SC alloy has very similar properties to 7000 series AL, but has about 10% more yield strength.

As fietsbob said, alter the hub, not the frame. You could take the nuts securing the hub shell to the axle to a machine shop and have them reduced 2 to 3 mm each in thickness for very little cost.
Already thought of that and know the machine shop to use. I e-mailed Harris Cyclery about this and the reply was that there was nothing to be removed from the hub but we shall see. I also consider it likely that despite the ostensible specs, the interference will measure to some other # than 5mm.

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Old 01-17-11, 07:09 AM
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Originally Posted by Don in Austin View Post
I also consider it likely that despite the ostensible specs, the interference will measure to some other # than 5mm.
I'm afraid you're probably right... but yeah, 3mm would be nice
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Old 01-17-11, 08:19 AM
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Originally Posted by MikeWinVA View Post
The melting point of AL is about 1220 F. You are not not going to get the frame to take a set with 400 degrees. An AL/SC alloy has very similar properties to 7000 series AL, but has about 10% more yield strength.

As fietsbob said, alter the hub, not the frame. You could take the nuts securing the hub shell to the axle to a machine shop and have them reduced 2 to 3 mm each in thickness for very little cost.
So that means despite the dire prophecies I get the frame back and it is unchanged. That would not surprise me at all.

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Last edited by Don in Austin; 01-17-11 at 05:39 PM. Reason: grammar mistake
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Old 01-17-11, 10:22 AM
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Depending on the hub we are now down to 4mm interference. UPS gal brought the frame and the dropouts measure 131MM!
This is not going to be a problem.

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