Help me save a crankset

[Kontact]

Originally Posted by dddd

But I never said that any of these things "were safe", that is the responsibility of the user, based on their familiarity with use of a torch for example.

You certainly can control the heat going into the metal, as I said, by shielding, by limiting exposure time, by chilling, and adding ice inside of the spindle.

That's a lot of control, but I wouldn't do any of that after drinking, or before using the other methods (as I already mentioned).

You can't shield one contiguous object from conduction when the part being heated is immediately adjacent to the part that would be damaged. You want to heat a part that is touching the carbon fiber.

Why suggest something that is unsafe? This is ridiculous. The OP isn't asking how to destroy his crank, but how to fix the problem without damage. And your suggestions are hitting it with a hardened chisel and holding a blowtorch on plastic.

Certainly, do whatever you want to your own stuff, but I hope I have made the problems with your suggestions clear enough that any sensible person would ignore you.

[dddd]

Funny how you seem to have issues with my posts today.

Please stop mis-quoting me. Has anyone mis-quoted you? If so, call them out on it, but don't mis-quote or deliberately mis-represent what I have said.

Because by now, you have done both. And don't pretend that the OP is a complete idiot.

[wildboar]

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[Kontact]

Originally Posted by dddd

Funny how you seem to have issues with my posts today.

Please stop mis-quoting me. Has anyone mis-quoted you? If so, call them out on it, but don't mis-quote or deliberately mis-represent what I have said.

Because by now, you have done both. And don't pretend that the OP is a complete idiot.

Where did I misquote you? I only have a problem with stuff that destroys things and hurts people. Geometry theories are only interesting, but you didn't explain yours enough to make sense to me.


Look, the problem with heat is best explained this way:

Take a block of wax and put a nail into it. Now immerse the block in ice water until only the nail is sticking up. Wax, like plastic, is a poor heat conductor. Now put a torch on the nail just above the wax for just long enough to make a serious temperature change in the nail.

Is the ice water going to keep the heat in the nail from melting the wax right where the nail goes in? No. Wax is a bad conductor, and the nail is a good conductor, so the heat will travel down the nail into the chilled wax and melt just the wax immediately touching the nail. It won't melt the whole block, but it will definitely affect the bond between metal and non-metal.


There is no way of controlling for that, except to use heat that is never above the melting point of non-metal. Which is a maybe 100° or so above boiling.

[dddd]

Originally Posted by wildboar

would it help chill the spindle using compressed air?

I wouldn't want to put that much heat into the spindle in the first place, since compressed air is going to be of very limited effectiveness unless there is a relatively large temperature drop from metal to air.
I wouldn't want to proceed to where the spindle itself got hot at all.

The spindle does have some good thickness that acts to resist rapid temperature increase, and water or ice would greatly increase that "thermal inertia" since liquid water has the highest "specific heat capacity" of any material on earth with ice adding latent heat of fusion to that!!

As for any concerns of the heated race damaging the epoxy, should it fail to pop off, it will lose it's modest heat to the thick spindle that it is pressed onto in very short order. I don't blame anyone for doubting me, but I've done this with a bigger race than this one and the speed of removal was pretty rapid.
The race isn't going to get very hot as long as it's still forcefully pressed onto the cooler spindle anyway, so it will simply come off or it won't during any judicious period of heating that would be worth attempting.
Cutting it off with a Dremel stone has it's own possible disadvantage related to scoring the spindle, but all things considered I did first advise using this method before resorting to heat.

As a bizarre side-note, my earliest recollection of ever being disciplined as a child was when my father discovered that, in his absence, I had absconded with his propane torch and proceeded to "test" it on just about every object about the house and yard. Some things it seems just never change.

[Kontact]

Originally Posted by dddd

I wouldn't want to put that much heat into the spindle in the first place, since compressed air is going to be of very limited effectiveness unless there is a relatively large temperature drop from metal to air.
I wouldn't want to proceed to where the spindle itself got hot at all.

The spindle does have some good thickness that acts to resist rapid temperature increase, and water or ice would greatly increase that "thermal inertia" since liquid water has the highest "specific heat capacity" of any material on earth with ice adding latent heat of fusion to that!!

As for any concerns of the heated race damaging the epoxy, should it fail to pop off, it will lose it's modest heat to the thick spindle that it is pressed onto in very short order. I don't blame anyone for doubting me, but I've done this with a bigger race than this one and the speed of removal was pretty rapid.
The race isn't going to get very hot as long as it's still forcefully pressed onto the cooler spindle anyway, so it will simply come off or it won't during any judicious period of heating that would be worth attempting.
Cutting it off with a Dremel stone has it's own possible disadvantage related to scoring the spindle, but all things considered I did first advise using this method before resorting to heat.

As a bizarre side-note, my earliest recollection of ever being disciplined as a child was when my father discovered that, in his absence, I had absconded with his propane torch and proceeded to "test" it on just about every object about the house and yard. Some things it seems just never change.

Again, the problem is that the race and spindle are excellent conductors and the spindle is embedded in an insulator - the CF. Any heat conduction is going to transport the heat to that insulating CF where it will only act on the metal to CF bond, instead of dissipating into it. Since the race is right up against the CF, there is no way that a coolant can hope to stop the heat conduction or cool the internal bond.

You are suggesting that butter won't melt in a skillet if you only heat the bottom of the pan for a little bit, and conduction does not work like that.

AND, you won't know how much damage you did to the bond until it fails, which is not pleasant with cranks.

[dddd]

Originally Posted by Kontact

Where did I misquote you? I only have a problem with stuff that destroys things and hurts people. Geometry theories are only interesting, but you didn't explain yours enough to make sense to me.


Look, the problem with heat is best explained this way:

Take a block of wax and put a nail into it. Now immerse the block in ice water until only the nail is sticking up. Wax, like plastic, is a poor heat conductor. Now put a torch on the nail just above the wax for just long enough to make a serious temperature change in the nail.

Is the ice water going to keep the heat in the nail from melting the wax right where the nail goes in? No. Wax is a bad conductor, and the nail is a good conductor, so the heat will travel down the nail into the chilled wax and melt just the wax immediately touching the nail. It won't melt the whole block, but it will definitely affect the bond between metal and non-metal.


There is no way of controlling for that, except to use heat that is never above the melting point of non-metal. Which is a maybe 100° or so above boiling.

I can't say what the temperature of the race would reach to during a quick blast of the torch, but I don't think that it is really in very good contact with structural carbon not covered by at least a layer of resin. The flow of heat from a modestly-heated race (it's still pressed onto the cool spindle) into carbon is very limited by composite's poor thermal conductivity, and one would not want to heat the race (however locally) to a smoking-hot temperature. It would either come off with a quick blast or it wouldn't, but I sure didn't advise more than a seconds-long blasting as an easy way to do what could be done with a simple Dremel stone. A grinding process, even if it scored the thick-walled spindle, could be polished away if one was concerned about the structural effect of such, but better to perhaps grind to where the metal was very thin by appearance, and then have a go with the sharpened softer-metal screwdriver as you suggested. Surely it would take less force to remove with any severe thinning of it's cross-section?

I must admit I am quick with the torch, it seems to be in my blood and only reinforced by frequent need to free stuck spoke nipples on very old bikes (and newer ones).
As with random tasks like bending one's chainstays to a modern OLD axle width, use of tools and methods to be in accordance with one's mechanical experience in all cases, and may the simplest method win the day.

[Kontact]

Originally Posted by dddd

I can't say what the temperature of the race would reach to during a quick blast of the torch, but I don't think that it is really in very good contact with structural carbon not covered by at least a layer of resin. The flow of heat from a modestly-heated race (it's still pressed onto the cool spindle) into carbon is very limited by composite's poor thermal conductivity, and one would not want to heat the race (however locally) to a smoking-hot temperature. It would either come off with a quick blast or it wouldn't, but I sure didn't advise more than a seconds-long blasting as an easy way to do what could be done with a simple Dremel stone. A grinding process, even if it scored the thick-walled spindle, could be polished away if one was concerned about the structural effect of such, but better to perhaps grind to where the metal was very thin by appearance, and then have a go with the sharpened softer-metal screwdriver as you suggested. Surely it would take less force to remove with any severe thinning of it's cross-section?

I must admit I am quick with the torch, it seems to be in my blood and only reinforced by frequent need to free stuck spoke nipples on very old bikes (and newer ones).
As with random tasks like bending one's chainstays to a modern OLD axle width, use of tools and methods to be in accordance with one's mechanical experience in all cases, and may the simplest method win the day.

I think the problem we are having is that you think "resin" and "carbon fiber matrix" are two different things. The Campy crank is a metal spindle that has been wrapped in resin and fiber. The resin is what makes the fiber stick to the metal.

That metal spindle is in such close contact with the race that the two are stuck to each other, so the conductivity is going to be excellent between them. 1mm away from the race is the resin that is keep the crank arm bonded to the spindle. There is no way heat one piece of metal without also heating the metal it is stuck on and the resin that is on that metal. Again, it is like trying to heat the bottom of the pan without melting some of the butter. It doesn't work like that.

The resin is not an expendable insulator - its the only thing keeping the crank arm on the spindle. You can't damage any of that.

[dddd]

Points taken, but the interference fit of the parts is quite small, lest the bearing roll "tight" on the inner race after being pressed on.

The heat required to sufficiently expand the race, immediately loosening it's grip to the point where no great thermal conduction is occurring, and then coming free before any resin-damaging temperature is reached is not going to require damaging temp's. That is the key here, that the press-fit interference is very small.

But again, I suggested this method last, after two other very simple method suggestions.
In the very unlikely scenario where the heating was deemed to be required, I am confident that you would be surprised by how rapidly that the race lost it's grip on the spindle. Race falls off, nothing left smoking or even very hot. And the resin has a temperature tolerance below which no degradation would occur, even if we take the assumption that the "critical" structural bond or fiber tension is in immediate contact with the heated race.
But you can't go too far wrong with assuming worst cases, and in any event you sure wouldn't want to be having to sell a bike to someone while disclosing how you "took a propane torch to the joint in the carbon crankset", lol.

Speaking of heat, after re-installing rails into plastic saddles a few times, I wondered if heat was perhaps used to expand the base of your saddles temporarily? Or are the rails flexed? I've used modest heat for this task.

I saw your saddle designs and wouldn't you know that I have been sourcing "flatter"-topped saddles for some years now, after suffering years ago with the likes of the Turbo and others that wedged the pelvis and make riding "on the rivet" more of an emergency procedure. I'll keep an eye out for these, but so far have chosen saddles with a bit of a rearward uplift to give added leg extension before sliding aft of the rear "edge" of the saddle.

[Kontact]

Originally Posted by dddd

Points taken, but the interference fit of the parts is quite small, lest the bearing roll "tight" on the inner race after being pressed on.

The heat required to sufficiently expand the race, immediately loosening it's grip to the point where no great thermal conduction is occurring, and then coming free before any resin-damaging temperature is reached is not going to require damaging temp's. That is the key here, that the press-fit interference is very small.

But again, I suggested this method last, after two other very simple method suggestions.
In the very unlikely scenario where the heating was deemed to be required, I am confident that you would be surprised by how rapidly that the race lost it's grip on the spindle. Race falls off, nothing left smoking or even very hot. And the resin has a temperature tolerance below which no degradation would occur, even if we take the assumption that the "critical" structural bond or fiber tension is in immediate contact with the heated race.
But you can't go too far wrong with assuming worst cases, and in any event you sure wouldn't want to be having to sell a bike to someone while disclosing how you "took a propane torch to the joint in the carbon crankset", lol.

Speaking of heat, after re-installing rails into plastic saddles a few times, I wondered if heat was perhaps used to expand the base of your saddles temporarily? Or are the rails flexed? I've used modest heat for this task.

I saw your saddle designs and wouldn't you know that I have been sourcing "flatter"-topped saddles for some years now, after suffering years ago with the likes of the Turbo and others that wedged the pelvis and make riding "on the rivet" more of an emergency procedure. I'll keep an eye out for these, but so far have chosen saddles with a bit of a rearward uplift to give added leg extension before sliding aft of the rear "edge" of the saddle.

The race was a slip fit, but metallic corrosion has filled the clearance up to where it is now a firm press fit (it's stuck). That's why I think the heat will go right through it to the spindle (on top of the fact that the flame is as wide as the race).

Thermoforming plastics, like the nylon base material of saddles, will become more elastic with modest heat, allowing more flex up until the point that it actually melts or burns. They will also take new shapes if restrained in them as they cool - other wise they tend to go back to normal. Some can even be melted over and over.

Epoxy and most composite resins are generally thermosetting, and they don't change properties much when heated - until they are damaged. This is why CF is not recycleable - you can't melt or dissolved the resin out of the fiber.


If I can help you with saddle questions, feel free to PM or use the contact feature on our website.

[m_sasso]

Do you guys midnight as suburban arsonists? Use the proper tool, a Bearing Splitter easy as pie!
Available in many sizes at an decent automotive shop.
Heat near last resort!

[Dead Man]

pretty much no way a few seconds of halfway coordinated application of heat from a $2.50 bodega crack torch is going to melt the carbon resin

lotta arguing about nothin boys

[Kontact]

Originally Posted by ariw

When I disassembled my c40, I (regretfully) neglected to remove the bearings from the fulcrum ut cranks for a while, and now I have this:



I used the park campy bearing puller tool, and the bearing assembly just came apart. Drive side came off just fine, but the outside race is stuck on the nds. I drizzled some lube on it in hopes of loosening it, but haven't attacked it again yet. Ideas?

Tia,
Ari

Where is the C-clip groove in this picture?

[dddd]

Originally Posted by Dead Man

pretty much no way a few seconds of halfway coordinated application of heat from a $2.50 bodega crack torch is going to melt the carbon resin

lotta arguing about nothin boys

But I don't ever use a bodega crack torch, honest!

One time long ago I used a propane torch to flash off some of the liquid solvent in my freshly-lubed chain, so that the solvent-diluted lube wouldn't tend to fly off and get onto the rim.
I thoughtlessly held the torch in one place while turning the cranks, managed to "black spot" the rear tire sidewall.
Another time, even longer ago, I was torch-soldering an open seam at the bottom end of a gutter down spout, when unbeknownst to me some dry organic material inside of the spout pipe suddenly began burning. I was startled to see the paint suddenly change color and start peeling away from the pipe which by now was sucking air noisily while acting as a tall chimney.
At least the roof didn't catch fire, I can't remember much else but there must have been a garden hose nearby and I probably had to do some explaining.

[Mackers]

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