Crank Removal Problems

[Pebble]

I can't see how you could retap it unless you went to a bigger size, when the crank puller stripped all the threads from the crank, material was lost so the hole is now too big.


As to how I am dealing with the problem. Well I just painted the BB with the crank on, put it all back together and that was 200 mile ago. I will get a new crank and BB in stock for when the time comes. If a two leg puller doen't get it I will try the nut removal and ride, and if that doesn't work will just cut it off (probably through the BB for quickness)

But in the mean time, which could be another 20,000 miles (4 years) until the BB fails, then there is not much point trying to get it off.

How very strange re reading this, 4½ years and 25,630 miles later - that job now needs doing

[Cyclothesist]

Buy a lottery ticket while your predictive powers are still functioning!

[Brucey]

with minimal effort, I think it ought to be possible to make and use a 'rubbodraulic' type crank extractor, using an old BB spindle. In use, it would simply be a matter of giving it 'what for' with a lump hammer, no extractor threads required.

[mig]

popped up to see a friend on Saturday and found him having woes in attempting to remove an Octalink left hand crank. are they , generally, more prone to seizing on? the bike has only seen dry miles and/or turbo use so i thought it odd unless the design has proved to be prone to troublesome..?

[AndyK]

popped up to see a friend on Saturday and found him having woes in attempting to remove an Octalink left hand crank. are they , generally, more prone to seizing on? the bike has only seen dry miles and/or turbo use so i thought it odd unless the design has proved to be prone to troublesome..?

Might be a silly question, but... could he be trying to use a square taper crank extractor to remove the Octalink crank?

[Brucey]

..... an Octalink left hand crank. are they , generally, more prone to seizing on?......

IME the answer to this question is 'YES' without question. If you talk to an engineer they will happily tell you that holding a tolerance of a few microns (which is what you need with octalink) in production is not very difficult, with modern equipment. Even so, they probably didn't get the design quite right first time, hence octalink V1 and octalink V2. Who knows what changes were made to the interference fit, but the splined part of the interface was made larger, for sure. I have always assumed that the V1 design would occasionally (in hard use) work loose. If this is caught early enough, you can simply use threadlock in place of grease, and the joint will be quite secure, albeit some heat will be required for disassembly. I have seen this used with V1 parts, but not with V2 parts. Note that the presence of the adhesive usually suppresses both fretting and corrosion in the interface.

The thing about Al is that it wants (very badly) to revert to its oxide form. This means that it will miss no opportunity to oxidise, eg. it will soon develop an oxide skin, even in a fairly hard vacuum. If this is translated into a pressure, that pressure is very high indeed; this is what is needed to mechanically suppress corrosion (the oxide being less dense than the metal). It is also the kind of pressure that can develop inside a joint if any active corrosion is present. This can exert a considerable 'grip' onto an octalink BB spindle, greatly increasing the difficulty of removal. A few drips of sweat is quite sufficient to foster the corrosion required for this. The good news is that there is a differential thermal expansion coefficient, working in your favour; ie. the Al of the crank always expands faster than the steel of the BB spindle. Too bad most octalink cranks are painted and will show scars from being heated very easily. Perhaps it is worth trying to cool the spindle too.

[slowster]

popped up to see a friend on Saturday and found him having woes in attempting to remove an Octalink left hand crank. are they , generally, more prone to seizing on? the bike has only seen dry miles and/or turbo use so i thought it odd unless the design has proved to be prone to troublesome..?

The one time I removed an Octalink chainset, I was in a hurry and did not appreciate that there was a washer that must be removed before inserting and using the crank extractor. My memory is somewhat hazy, but the piston of the extractor pressed on the washer, which prevented it from making contact with the end of the spindle.

[mig]

'tis possible that this washer hasn't been removed.....will ask the question....thanks.

from the look on his face when he described the attempts to remove i think that at least some of the 'corroded on' aspect to the equation also applies!