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Old 02-22-11, 04:35 AM   #1
Fabien1
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What goes xrong in my 3 speed hub?

Hello,
Please excuse my very plane english. I need your advise because in France
Sturmey Archer internal gear hubs are totally unknown.
I just restored an old Sparta bicycle with a Sturmey Archer AB (drum brake version) gear hub from 1984. The Hub does something very strange that is driving me nuts:

- On every pedal revolution, the left pedal is falling a bit to quick like there is no resistance inside the hub for an half second. It's like something slips inside the hub. The problem occurs a every speed position, always at the same pedal position. Even with a fine cable tuning, the problem stills. I can minimize it by searching the perfect cable tension but the problem stills anyway.
I've also noticed that the problem disappears on big efforts for example: riding a bridge, or an hill.

Thanks to Youtube videos, I took apart the hub 3 times to control the planet pinions, clutch, etc. I put every thing together, clean and lubricate.

But I just can't get rid of this problem.
Can someone help me ?

Best,
Fabien
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Old 02-22-11, 05:21 AM   #2
Esteban32696
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Welcome to the site. Your plain English is better than most Americans . I cannot diagnose your exact problem but it sounds like it is " slipping " a little. This site should be able to help. Pay special attention on the " inspection section."

http://www.users.globalnet.co.uk/~ha...samaintind.htm
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Old 02-22-11, 09:55 AM   #3
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If it happens every pedal stroke, it is not the hub. Check the bottom bracket and the pedal very carefully, also the chain ring.
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Old 02-22-11, 10:01 AM   #4
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I agree with waldo that nothing inside the hub will be exactly synchronized with the pedal stroke, especially if this happens in every gear. I'd suspect that one of your crank arms is loose or that there's some play in your bottom bracket bearing adjustment.
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Old 02-22-11, 10:37 AM   #5
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Count me as a third confirming that you are not describing a hub problem.

You are describing the classic symptoms of a loose crank arm. If it's a steel crank you have a loose or damaged cotter pin and it's easily fixed by replacing the cotter pin. If it's cotterless, there is a decent that the square tapered area is worn and the crank may need replacing.

To confirm the diagnosis, set the pedals horizontal and stand on both, then gently backpedal and stand and I'll bet that you feel one crank drop.

Keep in mind that it may not be the left crank that's loose or damaged. It could be secure on the spindle which is slipping in the right crank, so be sure to check and tighten both sides.
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Old 02-22-11, 10:52 AM   #6
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Quote:
Originally Posted by Fabien1 View Post
... in France
Sturmey Archer internal gear hubs are totally unknown.
They act like that down at my LBS, too! Lucien Petit-Breton, call your office!: 1, 2
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Old 02-22-11, 11:20 AM   #7
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Quote:
Originally Posted by Fabien1 View Post
- On every pedal revolution, the left pedal is falling a bit to quick like there is no resistance inside the hub for an half second. It's like something slips inside the hub. The problem occurs a every speed position, always at the same pedal position.
I think the problem is the crank cotter pin. Grab both crank arms and see if one of them is loose. Remove the pin on that arm and replace it with a new one.
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Old 02-22-11, 01:01 PM   #8
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tip put a block of wood under the crank so you do not damage the bottom bracket bearings
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Old 02-23-11, 04:30 AM   #9
Fabien1
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Waow thanks everyone for your quick answers.
In fact the right crank cotter pin is the one that is causing so much trouble!
Sometimes you don't see the most simple things... the crank, pedals and thompson bearing are new so I didn't check it. But the cotter was to much filed (newbie mistake) and after a few miles it was just worn out.
I'll set it right and then tell you if every thing is in order.
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Old 02-24-11, 07:08 AM   #10
Fabien1
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So it was cotter pins on both sides. Problem solved. Thanks again
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