Stuck Crank
- Thread starter Smokin Joe
- Start date
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Yellow Saddle
Guru
- Location
- Loch side.
It is more difficult to locally heat a mass of aluminium than a mass of steel because the aluminium is an excellent cponductor of heat and it would tend to distribute the heat to the whole workpiece rather than concentrate it locally like steel would. Some steels, especially stainless is such a poor conductor of heat that you get forget about heating the extremes of the workpiece unless you actually apply the heat to the individual areas.
Further, some metals require more heat to raise the temperature by a given notch. For instance, to raise the temperature of a gram of aluminium requires just under 1 Joule of energy per degree Celcius. To heat a piece of iron by one degree Celcius you need only half that amount of energy. It therefore requires less energy to heat steel. It is not only energy input but also how quickly the energy dissipates. Aluminium's thermal conductivity is high and to heat something like a crank means you have to heat the entire crank (or just about) whereas if you want to heat a steel crank stuck in the same way, just a little bit of local heat will do the trick.
Will the steel and aluminium expand at the same rate and therefore make the exercise futile? For this you have to look at how much they expand when heated. This is the co-efficient of expansion. The coefficient of expansion of aluminium is 22 and for steel it is 11. Forget about the units but look at the number only. It shows that for a given amount of heat, aluminium will expand twice as much as steel.
Long story short: bring on the blow torch but.... and there is always a rider to these things. It is no substitute for a proper puller and proper technique.
Yellow Saddle
Guru
- Location
- Loch side.
No, this is not true. Cranks (other than ones which were not torqued correctly in the first place) will squirm up the taper, not down the taper, when ridden forcefully. This is why you sometimes find a loose crank bolt inside the dust cap. It is not because the crank has come loose, it is because the crank squirmed further up the taper, leaving the bolt behind and effectively "loose".cranks with loose crank bolts tend to come loose when ridden... ride round the block until the crank loosens itself and push the bike home.
Yellow Saddle
Guru
- Location
- Loch side.
Not a workable plan. A taper does not tighten with directional forces in such a way that a reverse force will loosen it. Whilst a taper does squirm tighter in use, pedaling in reverse will simply make it tighter still.
Ajax Bay
Guru
- Location
- East Devon
+1. Solid object against the BB, 'tap' as a(n almost) directly opposing force, on a shortish (say 10cm) bar/spanner handle.
and again.
MontyVeda
a short-tempered ill-controlled small-minded troll
- Location
- Lancaster... the little city.
well it's worked for me on both tapered and splined cranks... so much so i don't bother with the extraction tool these days.
gbb
Squire
- Location
- Peterborough
Me too on one particular occasion when I didnt have a puller. Took a while in my case...but off it came.
50/50 chance, it might work, it might not.
Yellow Saddle
Guru
- Location
- Loch side.
Tapered and splined cranks are similar in that both squeeze onto an every enlarging BB axle. If your crank came off without a puller, it was not installed properly in the first place. If this happens more than once it simply tells you that your making the same mistake more than once. It is not a case of chance, it is a question of whether it was installed correctly. If you keep on installing it incorrectly, your chance is 100%. If you install it correctly, your chance is 0%. Some of you got it right half the time. I suppose it is better than never.
gbb
Squire
- Location
- Peterborough
If it was installed incorrectly...if...who knows. Regardless, its an option worth trying.
Last edited:
FrankCrank
Old layabout
Agree 100% with this, gentle persuasion is all that's needed...........if not, then a hefty whack
Yellow Saddle
Guru
- Location
- Loch side.
gbb
Squire
- Location
- Peterborough
Bring back cottered cranks, never had this trouble when i were a lad...
Oh....
Oh....
MontyVeda
a short-tempered ill-controlled small-minded troll
- Location
- Lancaster... the little city.
You're on your own with this one. Most of us don't need a torque wrench to mend a bike. Some of us have real world experience of removing stuck cranks the easy and hard way... 'my' easy way is worth a try, but that's for the OP to decide rather than anyone else.
