Need help removing cranks

[jacsmi]

Hi, I have an old Golden Sports ZebraKenko Thunder bike probably from the late 70s that I'm trying to upgrade. But I'm stomped on how to take off the cranks. There's only one nut on the each of the left and right cranks to remove, but that nut seem to do nothing.... Can someone point me in the right direction?

Pics of the cranks and nut below.

Thanks.

[cyclerUK]

These are known as "cottered" cranks. There is a flat on one side of the pin which locates against a flat on the bottom bracket axle. After removing the nuts you have to knock out the "cotter-pin". Put a piece of hardwood on top of the cotter-pin thread, hit the wood with a hammer to knock the pin out.

I used to slacken the nut a few turns and leave it on to protect the thread so that I could re-use it later. Sometimes these pins are stuck fast and you may damage them so buy some new ones. (I'm not sure if there are different sizes as well??)

N.B. Make a note of which way the pin is inserted as, if I remember rightly, it is supposed to go in only from one side.

See:-
Sheldon Brown for more info'.
http://sheldonbrown.com/cotters.html

and
http://www.sheldonbrown.com/tooltips/cotters.html

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Also, if you can, rest the crank on something solid to take the shock. If you hit the crank with just the bearing to support it then you are liable to damage the bottom bracket bearing. I used to rest the crank arm on 2 bricks. One either side of the pin head.

[jacsmi]

I tried your technique of putting a couple of bricks under. Works like a charm, thanks. =)

[Bill]

WOW, my 65 Armstrong 3speed uses these! I have not got to this part but definitely have this bookmarked for future ref. Nice Bike jacsmi .