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Removing a chainset - the hard way?

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  • 16-03-2011 10:17pm
    #1
    Closed Accounts Posts: 76 ✭✭


    Toolbox here stripped the threads on my chainset with a crank extractor a few months back and now Im kind of thinking that I could do with a new BB. - Anyone got any ideas on how to get the thing off. It's an old tapered type if thats any good to ya - The only thing I can think of is to remove the bold and pedal around in circles for miles in hope that it works itself loose! It might work??


Comments

  • Registered Users Posts: 4,076 ✭✭✭gman2k


    Maybe bring it to your LBS and they could tap out the threads, then pull it with a remover


  • Registered Users Posts: 724 ✭✭✭Keep_Her_Lit


    If the chainset/crank isn’t worth a packet, you could just cut it off and treat yourself to a new replacement at the same time as your BB. Just don’t let your hacksaw blade stray into the frame!

    If you want to remove it intact, then a small external bearing puller might do the trick, e.g.

    http://www.howdentools.ie/product.php?id=184&PHPSESSID=e7556bebdded2d3bc3b6a2fb416772d8

    If you know a fitter or mechanic you might be able to borrow one (too pricey to buy yourself for a once only job like this and probably not stocked by most tool hire shops).

    If you can’t get your hands on a bearing puller, then you might be able to lever it off, though you’ll need to be careful not to damage the bottom bracket shell on the frame. Applying some heat may also help it to come off, since aluminium alloys expand more than steel for a given temperature increase.


  • Registered Users Posts: 7,525 ✭✭✭kona


    A hub/bearing pullers of the right size would do it. As would a forked balljoint splitter.


  • Closed Accounts Posts: 76 ✭✭Fiachra cork


    Oky doky - definately don't want to wreck the chainset and cant afford to 'treat myself' just yet... Never saw these bearing puller things but will have a look around.
    Thanks


  • Closed Accounts Posts: 981 ✭✭✭Side Show Bob


    Toolbox here stripped the threads on my chainset with a crank extractor a few months back and now Im kind of thinking that I could do with a new BB. - Anyone got any ideas on how to get the thing off. It's an old tapered type if thats any good to ya - The only thing I can think of is to remove the bold and pedal around in circles for miles in hope that it works itself loose! It might work??

    Very lighty heath it with a small blow lamp, from a distance so as not to discolour the crank, alloy expands much faster than the steel axel. dond beat with hammer it wont work


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  • Registered Users Posts: 7,525 ✭✭✭kona


    Very lighty heath it with a small blow lamp, from a distance so as not to discolour the crank, alloy expands much faster than the steel axel. dond beat with hammer it wont work

    Have you tried this method to remove anything seized? If there are options before it Id use them before the blowtorch, its all too easy to get a nasty burn, and I have used a blowtorch in desperatation, it solved the problem, but by no means did the bolts or tapers come without a fight, Its all to easy to slip and burn yourself off whatever your heating, especially if the part isnt secured.


  • Closed Accounts Posts: 339 ✭✭SurferDude41


    Dude, you need to get yourself a 3 armed bearing puller. I think mine cost around €12. It's vitally important you Wear safty goggles, just incase something flies loose.
    Only use it on an alloy chainset spider, a carbon chainset spider may splinter and crack.
    Here is a photo of mine,

    Happy Cycling.....SD..

    3ArmedBearingPuller001.jpg


  • Registered Users Posts: 68,317 ✭✭✭✭seamus


    Dude, you need to get yourself a 3 armed bearing puller. I think mine cost around €12. It's vitally important you Wear safty goggles, just incase something flies loose.
    Only use it on an alloy chainset spider, a carbon chainset spider may splinter and crack.
    These are surprisingly tricky and may not work depending on the shape of your crankset. I managed to destroy an alloy MTB crankset with one of these by snapping off one of the spider arms. Had to cut the crank arm off with a dremel and buy a new chainset (oh noes ;))

    You do have to consider that this is going to be a problem every time you replace a bottom bracket.

    I do have a bearing puller that I don't see myself ever needing in future that you can have, but I'm guessing you're in Cork, so that's no good to you :)


  • Registered Users Posts: 2,615 ✭✭✭happytramp


    Have done this a few times and will be doing it again next week for a new BB. Heat the crank with boiling water/blow lamp to expand metal (not totally necessary). Rest the crank on a couple of bricks so that it is supporting the weight of the bike. Insert a used/spare crank bolt half way in and hit it with a hammer. This will tap out the axle arm causing the bike to drop so put something soft under it.


  • Registered Users Posts: 724 ✭✭✭Keep_Her_Lit


    happytramp wrote: »
    Have done this a few times and will be doing it again next week for a new BB. Heat the crank with boiling water/blow lamp to expand metal (not totally necessary). Rest the crank on a couple of bricks so that it is supporting the weight of the bike. Insert a used/spare crank bolt half way in and hit it with a hammer. This will tap out the axle arm causing the bike to drop so put something soft under it.

    That sounds like the most promising suggestion so far. Nice one. Must add that to my "box of tricks" list!

    I was in Kilmainham Jail recently - doesn't seem to be much scope for a decent spin in there. :D


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  • Closed Accounts Posts: 76 ✭✭Fiachra cork


    happytramp wrote: »
    Have done this a few times and will be doing it again next week for a new BB. Heat the crank with boiling water/blow lamp to expand metal (not totally necessary). Rest the crank on a couple of bricks so that it is supporting the weight of the bike. Insert a used/spare crank bolt half way in and hit it with a hammer. This will tap out the axle arm causing the bike to drop so put something soft under it.

    Right - not totally with ye on this - Its the chainset thats stuck so am I resting the chainset on the bricks and whacking the BB axel from the other side? - Hang on that doesnt make to much sense. What am I saying? Am I basically smashing the BB Axel out? I suppose if this is the case. I'de be hitting if from the chainsed side and driving it back into the BB?


  • Registered Users Posts: 7,525 ✭✭✭kona


    happytramp wrote: »
    Have done this a few times and will be doing it again next week for a new BB. Heat the crank with boiling water/blow lamp to expand metal (not totally necessary). Rest the crank on a couple of bricks so that it is supporting the weight of the bike. Insert a used/spare crank bolt half way in and hit it with a hammer. This will tap out the axle arm causing the bike to drop so put something soft under it.

    How does the Bottom Bracket fare?


  • Registered Users Posts: 724 ✭✭✭Keep_Her_Lit


    Right - not totally with ye on this - Its the chainset thats stuck so am I resting the chainset on the bricks and whacking the BB axel from the other side? - Hang on that doesnt make to much sense. What am I saying? Am I basically smashing the BB Axel out? I suppose if this is the case. I'de be hitting if from the chainsed side and driving it back into the BB?

    Whoa! Steady on.

    I'll try to describe it. If my description isn't clear enough, let me know and I'll mock it up using my own bike and take a photo to illustrate it for you.

    1. With the bike upright, rotate the crank so that the RHS pedal is at its lowest point.

    2. Now lie the bike on its LHS so that the chainset is facing up [it is the chainset that's stuck and not the LHS crank arm - correct?].

    3. When you stand over your bike, you are now looking directly down into the seized BB axle. [OK?]

    4. Now imagine that the bike is still on its LHS but is elevated one foot above the floor and that it is being held there by the chainset, e.g. imagine that the crank arm attached to the chainset is clamped into a hefty vice.

    5. If you now screw the crank arm bolt several turns into the BB axle (but not all the way in) and then give it a sharp blow, it will drive the BB axle out of the crank arm.

    6. But the crank arm can't move because it is clamped. So instead, the rest of the bike will move and will fall to the floor when the BB axle is driven completely back out of the crank arm.

    This is exactly what you want to do, except that the crank arm is going to rest on top of a few bricks instead of being clamped into a vice. Does this make any sense? I think it would also help if someone can assist you; they can support the bike by the saddle and stem, lifting them off the floor by a few inches so that bike is horizontal. This would also minimise the shock transmitted to other components when you whack the BB axle.

    Actually, this method was happytramp's suggestion and he/she has done it before, so may have something to add.


  • Registered Users Posts: 2,615 ✭✭✭happytramp


    Yep 'Keep her lit' that is exactly what I was talking about, you are effectively knocking the bike off the chainset and not the other way around as you pointed out. Another person to assist would be ideal to prevent and damage to the bike. In my experience a heavy but well placed blow from a hammer frees the bottom bracket fairly easily and so far has never damaged the bike or BB. I would point out however that it will almost certainly damage the crank bolt so use an old or spare one. Good luck!


  • Closed Accounts Posts: 76 ✭✭Fiachra cork


    Whoa! Steady on.

    I'll try to describe it. If my description isn't clear enough, let me know and I'll mock it up using my own bike and take a photo to illustrate it for you.

    1. With the bike upright, rotate the crank so that the RHS pedal is at its lowest point.

    2. Now lie the bike on its LHS so that the chainset is facing up [it is the chainset that's stuck and not the LHS crank arm - correct?].

    3. When you stand over your bike, you are now looking directly down into the seized BB axle. [OK?]

    4. Now imagine that the bike is still on its LHS but is elevated one foot above the floor and that it is being held there by the chainset, e.g. imagine that the crank arm attached to the chainset is clamped into a hefty vice.

    5. If you now screw the crank arm bolt several turns into the BB axle (but not all the way in) and then give it a sharp blow, it will drive the BB axle out of the crank arm.

    6. But the crank arm can't move because it is clamped. So instead, the rest of the bike will move and will fall to the floor when the BB axle is driven completely back out of the crank arm.

    This is exactly what you want to do, except that the crank arm is going to rest on top of a few bricks instead of being clamped into a vice. Does this make any sense? I think it would also help if someone can assist you; they can support the bike by the saddle and stem, lifting them off the floor by a few inches so that bike is horizontal. This would also minimise the shock transmitted to other components when you whack the BB axle.

    Actually, this method was happytramp's suggestion and he/she has done it before, so may have something to add.

    Right - was a bit tired last night and couldn't make sense of it - I get it now, no need for the visuals unless you really want to! (You'd never know - The thing is, the BB is still Ok (I think) but its in there a few years now and has quite a few miles up on it - no play though as far as I can tell. I can see how this method would work - a bit of a gamble though? It seems to work for you anyhow - I might hold off a while and give it a lash when I need to - Its an awful pain but its a retro bike I have and I really like the old chainset.

    Thanks again.


  • Registered Users Posts: 724 ✭✭✭Keep_Her_Lit


    The thing is, the BB is still Ok (I think) but its in there a few years now and has quite a few miles up on it - no play though as far as I can tell.

    If the BB shows no signs of play and turns smoothly, then leave it there. You could get years more out of it!

    I can see how this method would work - a bit of a gamble though?


    The only risk I can see with this procedure is to the threads in the BB axle and on the crankbolt, since the force of any blows applied to the crankbolt will be transmitted to the axle via the threads. You can minimise this risk by screwing the crankbolt well into the axle before striking it. This will distribute the force of the blows over a good number of turns. If you only screw the bolt in by 2 turns, say, then you are much more likely to mangle the threads when you start getting lively with the hammer.



    Once the BB axle starts to shift, you may need to progressively unscrew the crankbolt to allow further progress. But this should be OK, since the most force will be needed just to get some initial movement. Further movement should then be possible with significantly reduced force.

    I don’t think there is any risk to either the BB bearings or the frame. All of the applied force will be directed at breaking the unwanted seal between the crank arm and BB axle. As soon as that seal is broken, the bike is free to move in response to any further applied force, i.e. it will just fall a few inches to the floor.


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