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 Post subject: crank help!
PostPosted: Sat Jun 01, 2013 6:21 pm 
Dirt Disciple

Joined: Mon Sep 19, 2011 9:34 pm
Posts: 23
hi,

trying to strip my latest project ready for paint, but i'm well and truly stumped as I've never removed a crank like this (see pictures)

does anyone know how to remove this type of crank??
if it helps, the frame is an old sun worksop, 'sun stanga'

this is the drive side, which chainring removed, and nut from the bolt removed:
Image
Image

I've loosened the only thing i can see that can be loosened, which is a bolt going through the crank (same on both left and right crank). but this seems to have done nothing.

any help appreciated!!!


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 Post subject: Re: crank help!
PostPosted: Sat Jun 01, 2013 6:27 pm 
Retro Guru
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Joined: Sat Apr 02, 2011 11:16 am
Posts: 799
Location: Camden, London
it's a cottered crank, the pin with the thread where the bolt is removed is the cotter pin and to remove the crank need to remove the pin. Various ways of increasing violence. The pins are replaceable, check out on line searches for various cautionary approaches, BITD I used to partially screw nut back on and hit with a hammer to partially dislodge pin.

See also Sheldon Brown................

http://sheldonbrown.com/cotters.html


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 Post subject: Re: crank help!
PostPosted: Sat Jun 01, 2013 6:33 pm 
Dirt Disciple

Joined: Mon Sep 19, 2011 9:34 pm
Posts: 23
Cheers for your help!, looks like I've got a fun job on my hands, especially lacking most of the tools mentioned lol

Here goes.. :s


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 Post subject: Re: crank help!
PostPosted: Sat Jun 01, 2013 6:36 pm 
Retro Guru
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Joined: Sat Apr 02, 2011 11:16 am
Posts: 799
Location: Camden, London
chuck some oil down round the pin, leave overnight and the main tool is a big hammer :D


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 Post subject: Re: crank help!
PostPosted: Sat Jun 01, 2013 10:40 pm 
Retro Guru

Joined: Sun Aug 22, 2010 7:07 pm
Posts: 1321
Location: Cotswolds
Apart from using special tools, my favourite method was to use 2 hammers.
Support the bottom bracket however you can. Hold 1 hammer on the cotter pin and hit the first hammer with the second. This gives an easier target and keeps fingers out of it, so more likely to be effective. You hit the threaded end.


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 Post subject: Re: crank help!
PostPosted: Sat Jun 01, 2013 11:31 pm 
Old School Grand Master
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Joined: Fri Oct 14, 2011 8:41 pm
Posts: 8226
Location: Cumbria
.......customers used to get pretty shirty if you missed the end of the cotter pin and hit their chainset........Never swing the hammer at the end of the cotter pin, we had a block of metal hanging around which was cheaper to damage than a second hammer :)

Shaun


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 Post subject: Re: crank help!
PostPosted: Sat Jun 01, 2013 11:42 pm 
Old School Hero

Joined: Sun Apr 28, 2013 8:56 pm
Posts: 209
Location: Flipping between Wigan and Lincoln
And if you are going to hit one hammer with another... Wear some kind of eye protection!

I haven't worked on cottered cranks for a long time but I do remember that you need to support the back side of the crank with something to reduce the chances of damaging something - helps to prevent movement of the arm too (in my youth a couple of house bricks did the trick!)

Don't expect to be able to reuse the cotter pin either, they were always treated as a one-use item BITD (very often the threads would get damaged on extraction anyway).


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 Post subject: Re: crank help!
PostPosted: Sun Jun 02, 2013 1:08 pm 
rider | rBoTM Winner
rider | rBoTM Winner
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Joined: Fri Jan 25, 2008 1:42 pm
Posts: 5131
Location: Wakefield, Yorkshire
Cotter pins are a taper fit which fits into a tapered 'groove' in the axle. The threaded portion pulls the cotter pin into the hole and tightens the tapers together. If they've been fitted for some time there may be a bit of corrosion on the tapers which is why a good slug of penetrating oil/PlusGas etc. may help before attempting to use the hammer. Reattach the nut with the top flush with the end of the threads of the pine. Provides a larger target!


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