Cup and axle bottom bracket woes

[Ian_1967]

Hi,
I'm rebuilding an old peugeot racer but really struggling on the bottom bracket
. 1st problem is that I can get the pedals turning beautifully going forwards. However, on turning the pedals backwards, the bb is sticking slightly.
2 nd problem- any advice for getting a really stuck fast fixed cup off!! I've soaked in wd40. No luck!
Thanks everyone

 

[sidevalve]

Not exactly sure on your meaning but the fixed cup is fixed - that's why it's called fixed. I doesn't come off.
As for the sticking problem there are several possibilities 1 - are you sure you have the right no of bearings if they are loose ball type - usually one less than seems right is correct. 2 - is it certain that the axle is 100% straight 3 - be careful nothing is 'tightening up' as you turn it backwards

 

[Yellow Saddle]

I have never come across a BB that sticks in one direction. Doesn't it stick too when you turn it several times forwards? Bearing balls don't rotate once per crank rotation and a bad ball won't show up at exactly the same place each time. If you inspect the bearings and races the problem should be obvious.

As for the problem with removing the cup.

1) Are you absolutely sure about your direction of removal? Remember, the right side is a left hand thread on English BBs but not on Italian. I have no idea about old French BBs but they had unique dimensions.
2) If your spanner isn't damaged by now and the flats on both the BB and spanner are still good, try and clamp the spanner onto the bb so that it cannot move to the right and disengage. Do this by wangling a bunch of washers or spacers so that the BB bolt can push them against the spanner and keep it in place no matter what. Then apply lots of leverage with a long instrument - a piece of pipe or such. However, the minute the BB starts to move, you have to remove the clamping device otherwise the BB cup can't come out and it will strip the threads.
3) If all that fails, weld a piece of flat bar onto the BB cup and turn it off. This obviously destroys the cup but it works like a charm.

 

[Ian_1967]

I've been careful not to damage the fixed cup so will try those ideas.

 

[arch684]

On vintage Peugeot bikes the fixed cup is right hand thread

 

[arch684]

R J the bike guy on you tube has a video of this,worth watching

 

[Ian_1967]

Excellent, I know which way to try now!

 

[Ian_1967]

Just checked the video. Awesome- thanks for that.

R J the bike guy on you tube has a video of this,worth watching

 

[Tim Hall]

Use the Sheldon Brown big nut and bolt method, rather than trying to get a spanner to stay on the flats or weld a bar on. It's my favourite bit of bodgery. Linky.

(scroll down to fixed cup tools)

 

[raleighnut]

Sounds to me like the cage has 'knife edged' with wear, just fit 2 new races of bearings.

 

[gbb]

Sounds to me like the cage has 'knife edged' with wear, just fit 2 new races of bearings.

I have known bearings to effectively lock up when trying to reverse, I always assumed the cage wore and allowed the balls to touch while rotating in opposite directions...thus locking up as they touched. Perhaps this is effectively what you're describing.
I cant remember if this was on a bike or in an engineering application, but it does happen.

 

[raleighnut]

I have known bearings to effectively lock up when trying to reverse, I always assumed the cage wore and allowed the balls to touch while rotating in opposite directions...thus locking up as they touched. Perhaps this is effectively what you're describing.
I cant remember if this was on a bike or in an engineering application, but it does happen.

The cage wears to a thin 'knife edge' by the bearings contacting it (insufficient lubrication or a very long service life) then as you try to reverse the direction the balls 'climb' the edge and lock as effectively as a stud extractor does ( or the pawlless freewheel in a Saab 96/95 gearbox)
Don't forget it is only by contacting the bearings that the race 'cage' rotates at all.

 

[gbb]

The cage wears to a thin 'knife edge' by the bearings contacting it (insufficient lubrication or a very long service life) then as you try to reverse the direction the balls 'climb' the edge and lock as effectively as a stud extractor does ( or the pawlless freewheel in a Saab 96/95 gearbox)
Don't forget it is only by contacting the bearings that the race 'cage' rotates at all.

While I cant visualise the knife edge in detail, I do know exactly what you mean re the balls locking, its the same principle as one way bearings we use in wire feed mechanisms and uplift conveyors that need to resist weight pulling the belt back down, with the use of one way bearings. I did strip one down once out of nosiness but can't remember the specific details \design. Interesting anyway