Stuck Mercury EBB - what to do?

[quilkin]

Hi, this is a follow-on from my earlier question about changing a chainwheel (http://thorncyclesforum.co.uk/index.php?topic=14330.0).

To cut a very long story short, I have now succesfully managed to fit a new chain with my preferred chainwheel & sprocket (39/17). The EBB is still totally stuck, and I have tried every trick in the book to free it (coins to open the EBB casing, heating the EBB, PlusGas down the seat tube....).
The new chain is reasonably tight (about 25mm of slack after riding 150 hilly miles) but I effectively have no way of adjusting it when it gets too much slack.
One option is to send the whole frame back to Thorn to see if they can free the EBB, although I have spoken to them and tried all the methods they would use, so they may not be able to fix it.
The other option is just to change the chain (very) prematurely when it gets too slack. At £16 a time this could be cheaper than returning the frame .
From peoples' experience, how many more miles would I expect to get from a chain (8-speed) before it gets to the critical 60mm of slack?

[B cereus]

I would strongly advise you to persevere with freeing up the EBB, it will only get worse over time.  Better that you fix the problem now and in future regular removal and re-greasing should prevent a reoccurrence.

I'm sure somebody will be able to fix this, if not SJS then perhaps someone more local to you. If all other methods fail then selectively machining away the aluminium should allow the insert to be folded inwards and removed. A decent  frame builder should be up to the task.

[geocycle]

It will last for quite some time without adjustments, initial wear appears quick then seemed to slow down. Or perhaps the difference is less detectable. Not sure I can put a figure but I’d guess more than 1000 miles. But, it needs sorting so I’d definitely take it to SJS or a LBS if the logistics don’t allow.

[JohnR]

There's some discussion about chain life here http://thorncyclesforum.co.uk/index.php?topic=14115.0 . I'm currently using a KMC E1 (bought at a reasonable price from Amazon Warehouse) which has done over 4500 miles and hasn't yet needed adjusting. However, it's inside a Chainglider and fairly well protected from muck. A further benefit of the Chainglider is to make it difficult for a slack chain to jump off. However, if you go down the Chainglider route (which I don't regret) then you might need to change to a thinner chainring. I got mine from https://www.sourcebmx.com .

[Aleman]

I wonder if this is a very severe case of Galvanic "Corrosion"/"Welding" ... If the anodising of the Eccentric has become damaged, and salt water has got in there (one reason whey they should be greased ... and then greased again), then that Aluminium is going to corrode incredibly fast, if left for too long then there will be no shifting it. ... Penetrating oil is unlikely to help.

A bit like a stuck seat post, I suspect that a drift and a big hammer is going to be the only way to free it. Possibly bolting together a couple of steel discs just smaller than eccentric on the either side, and then hitting the bolt, or using a slide hammer. Either way the frame and the eccentric shell will need support.

Cutting slots and a V out of the bottom of the eccentric with a hacksaw, shouldn't be too much of an issue, which would allow you to knock it out section by section with a very old screwdriver and a hammer.

[Kipper]

I have exactly the opposite problem in that I cannot stop my EBB from rotating when tightening the bottom bracket cups.  Even with the pinch bolts torqued to the recommended 8Nm the EBB rotates without excessive tightening force being applied via the bottom bracket tool and a socket handle.  This leads me to suggest that trying to rotate the EBB in the shell may provide an answer.  Now for a few words of caution!  I have a Phil Wood square taper bottom bracket which has strong stainless steel cups both of which screw in and compress the BB between them.  There are no flanges on the cups so the BB can be shifted left and right to achieve the desired chain line.  This means that as you tighten either cup it also turns the BB and the opposite side cup until the whole assembly clamps itself in position.  Any turning force is thus distributed across the cup threads on both sides of the EBB.  I would be wary of applying too much force to a single conventional aluminium cup as it would probably split the flange, strip the thread or destroy the tool mating slots.  Just a thought but you may be able to jury rig something to either replicate the mounting of a Phil Wood bottom bracket or in some other way apply a significant rotational force to the EBB.

[quilkin]

I have exactly the opposite problem in that I cannot stop my EBB from rotating when tightening the bottom bracket cups.  Even with the pinch bolts torqued to the recommended 8Nm the EBB rotates without excessive tightening force being applied via the bottom bracket tool and a socket handle.  This leads me to suggest that trying to rotate the EBB in the shell may provide an answer.  Now for a few words of caution!  I have a Phil Wood square taper bottom bracket which has strong stainless steel cups both of which screw in and compress the BB between them.  There are no flanges on the cups so the BB can be shifted left and right to achieve the desired chain line.  This means that as you tighten either cup it also turns the BB and the opposite side cup until the whole assembly clamps itself in position.  Any turning force is thus distributed across the cup threads on both sides of the EBB.  I would be wary of applying too much force to a single conventional aluminium cup as it would probably split the flange, strip the thread or destroy the tool mating slots.  Just a thought but you may be able to jury rig something to either replicate the mounting of a Phil Wood bottom bracket or in some other way apply a significant rotational force to the EBB.

My BB is aluminium (like this one https://www.sjscycles.co.uk/bottom-brackets/english-shimano-bbrs500-bottom-bracket-cups/) but but before I read your post I did try using torque on the BB itself, overtightening it to try free the EBB. I have now almost destryoyed the teeth on the BB, but the EBB did move a bit (about 12mm of cicrmference). It didn't want to move any more. This required hitting the end of the BB spanner with a lump hammer. 
Refitting the cranks , the chain was then too short, so I managed to reverse what I had done - this was a tiny bit easier.
I have now squirted in more PlusGas, and will ride it a few miles (without any fixing bolts) to see if it frees up any further. I'm resigned to buying a new EBB and BB, if only I can get out the old ones!

[PH]

the EBB did move a bit (about 12mm of cicrmference). It didn't want to move any more. This required hitting the end of the BB spanner with a lump hammer. 

If it's moved you've broken the bond, it's now just a matter of working it.  Leverage will be better than brute force, a metre pipe on a pin spanner will do more than a lump hammer, lean on it in one direction, then the other, spray Plus-gas, repeat... Do all this with the pennys inserted and the screws tightened against them as much as you're comfortable with.

[lewis noble]

It may take several 'sessions' to sort it out, bit by bit, with more releasing fluid each time.  Patience is worth it, it sounds as though it will come out eventually, and the effort will be well worth it, enabling you to regrease/ reinstall everything and use it properly.

I guess it had been neglected before you got it at some stage:- a reminder to us all!!

Lewis

[quilkin]

Leverage will be better than brute force, a metre pipe on a pin spanner will do more than a lump hammer, lean on it in one direction, then the other, spray Plus-gas, repeat... Do all this with the pennys inserted and the screws tightened against them as much as you're comfortable with.

+1. Thank you - leverage has worked. (I couldn't find a steel pipe the correct size to fit the BB spanner so I made an extension with 12" Meccano angle girders!). Since I was overtightening the BB to get enough torque on the EBB (using the 4mm holes provided would never have shifted it) the BB is now permanently embedded in the EBB, so I will order new of both (the teeth on the BB are now knackered anyway as you can see).
I assume the dirty gray/white residue is aluminium oxide, due to extended length of time with water being sprayed up into the slotted section of the frame. It won't wash off or dissolve in alcohol, so it's not just dirt. The anodising doesn't appear to have done a great job.
I wonder how long this had been left to corrode without anyone adjusting it?

[JohnR]

Well done.

This reminds me that I should check / service my EBB before winter arrives. What do people recommend as the best anti-seize grease for such situations?

[PH]

leverage has worked.

Yay, well done.  That doesn't look like it's ever seen much grease! 
While it's out I'd clean the inside of the shell with some fine wet and dry paper, it's stainless so should clean up bright.

[PH]

What do people recommend as the best anti-seize grease for such situations?

I've always used some form of copaslip, it has some copper solids in it, the idea being that if the grease should dry out those solids will keep the two serfaces apart.
Really, the most reliable element is frequency.  All my bikes get stripped and cleaned and greased annually, my most used twice a year. IMO it's time well spent.

[Aleman]

What do people recommend as the best anti-seize grease for such situations?

If it's two dissimilar metals coming together (Especially Steel and Aluminium) Then I'll use copaslip of some sort, and plenty of it. The copper contained in the grease acts as a "sacrificial anode". We don't use the tandem(s) during the winter, but if I was to, then I'd clean and inspect at the start and end of the gritting season(s) It's not a massive chore. ... unless your BB is of the loose bearing type ... then it's a tittle more tricky

[quilkin]

Interesting (I hope) postscript to this, which may be of help to others.

I sanded down and regreased the EBB and tried fitting it as a trial before ordering the new parts. It was difficult to get it in, except in certain orientations: as I turned it, it got easier and harder to turn; at the worst point I couldn't turn it using my max hand force on the (now embedded) BB cup. So something still 'eccentric' apart from the internal borehole itself.

At this stage I still had the bolts and 'coins' (large washers) fitted to the clamps, so I removed these. A slight improvement. I then tightened them slightly in the normal way (i.e. from the correct side, without washers) and - hey presto - the EBB now turns smoothly for the complete cirucmference! So, in my case at least, forcing the clamps open with washers was actually making the orginal problem worse, by distorting the bearing shell.

Tightening the four bolts completely to 6Nm has made the assembly tight enough to refit the other BB cup without the wole thing rotating. Now for a test ride....

BTW, does anyone know why Thorn use hex-head bolts for this? They need an 8mm socket which isn't part of a normal cycling toolkit. What's wrong with standard 5mm socket-head bolts, using a 4mm Allen key?