Stuck Mercury EBB - what to do?

[quilkin]

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".

Hmmm- I tried to read up on this, and found differering opinions - many saying that copper slip was only useful in hot conditions. I'll try to decide before I fit the new EBB.

[Aleman]

You may well be right ... It just makes sense to me "metallurgically" ... It may well be that all it really requires is a normal grease with regular preventative maintenance, especially if used in wet and salty environments

[PH]

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".

Hmmm- I tried to read up on this, and found differering opinions - many saying that copper slip was only useful in hot conditions. I'll try to decide before I fit the new EBB.

I hadn't heard that, but then I haven't extensively researched it, just looked and my tin says effective down to -40C and up to 110C
I've been using it on my EBBs since 2004 without any issue, though as I said they get serviced at least once a year, so it may be that any grease would have been OK.
What is it that these reports are saying?  That the solids are not required, or that there's a failure with the grease they're in? 
Alternatives would be any anti-seize grease, there's several cycle specific ones from the likes of Park Tools, but I have a suspicion that such specific  products are generic and rebadged with a considerable premium. 
I have a tub of waterproof marine grease which I use in other applications where keeping the water out is a higher priority than preventing seizure, usually around bearings, chances are it would be just as good in the EBB shell, but my tin of Copaslip will last me this lifetime so I have no incentive to try it.
I have a friend who swears by Vasaline, his bikes run perfectly so it obviously works for him.

[PH]

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?

Yes - they're in just the right place to fill with muck which over a few month will solidify.  OK, probably never to the extent where you can't dig them out with a pointed object, but it's another job.  I have a small, good quality 8mm spanner that is fine, no need for a socket, it's in the touring kit because in the unlikely event of a shifting problem it'll change gear at the hub end.
I think Thorn have a preference for hex heads over socket heads on all the fittings, they certainly used to and you had to specify on the order form of you wanted cap heads.

[RobertW]

I had not removed the EBB from my mkII Mercury in over 2 years from new.  I was finding it increasingly difficult to turn the EBB to adjust for chain wear.  The supplied pin spanner was never enough.  Needed a large spanner on the BB removal tool, stanard shimano type square taper BB.  Reading this thread prompted me to try removing the EBB.  Using coins with the EBB securing bolt to open up the BB shell a fraction , the EBB  could be rotated using the large spanner and BB tool.  Careful tapping with a lump hammer got the whole BB assembly out without too much difficulty.  The EBB shell looked very much like the image posted above.  The inside of the BB shell was shiny and smooth (it is stainless ?).  Some light sanding with wet and dry paper removed the surface roughness from the bottom of the EBB.  I applied copaslip to the EBB and tapped it back in.  It still needs more leverage than the pin spanner can provide to rotate it.

I have ordered a new EBB, but plan to see how the old one fares , but plan to remove before and after winter to regrease.

[Mike Ayling]

+1 for the coin method.
Mine loosened enough to use the pin spanner.

[Andyb1]

This will not be a popular reply…..

When I wanted a Rohloff geared bike 2 years ago I logically should have bought from Thorn (who are 10 miles away from me).

Unfortunately I had previously had a bad experience with them when the Nomad frame I bought to fit with 3 x 9 transmission parts had a dent in the top tube…..only discovered when I removed the top tube wrapping after building the bike up.   The frame was returned, they could not replace it, I was refunded the frame cost so bought an alternative make of frame.  There were other problems I will not go into.  A shame as if it had worked out I planned to keep the Nomad frame and eventually change it from 3 x 9 to Rohloff.

When building the Nomad it gave me a chance to critically look at the EBB area.   I work with aircraft and alloys / steel / stainless steel fixed together produce corrosion.  The split in the frame allows water to be sprayed onto the EBB and adds a potential weakness.  And don’t mention the weight.

Service it regularly and it will probably be fine, but forget to do so (if you are not riding the bike regularly) and pretty soon it will corrode.   And corrode fast if the anodising on the alloy EBB has got scratched.

The other feature of the design I did not like is how the clamping bolts can dent the EBB.

So when the 3 x 9 bike I built up went to a friend and I was ready to buy a Rohloff geared bike I bought elsewhere - and bought a bike with a conventional BB and with the rear wheel adjustable fore / aft using Rohloff supplied parts.

[in4]

Interesting and a reminder to check my MK2 Nomad EBB although after circa 5000 miles I’ve not noticed any issues. In a previous thread I posted a photo of the MK3 Nomad EBB. It’s different to the MK2 Nomad.

[PH]

The other feature of the design I did not like is how the clamping bolts can dent the EBB.

I'm not sure which models of Nomad and types of EBB you're referring to?
The Mk3?  It's the only one I know of designed for either Rohloff or derailleur.  If so, how can the insert be dented?  In previous models, it wasn't that the insert could be dented, it was intended to be, that's how it works.

Service it regularly and it will probably be fine

By service, you mean remove and grease, or similar, every year or two?  I don't know of any bicycle component that doesn't benefit from some maintenance, that includes all types of EBB's and sliding dropouts.
I doubt the amount of water getting into the EBB shell is significantly worse then that getting into a standard one. The most common point of entry is down the seat tube. If you search Google images for used BB's, you won't find many that are corrosion free.  it can be avoided of course, by the same level of servicing required to keep an EBB corrosion free.  Thorn's stainless steel shell makes the corrosion less likely in the frame itself.  And one of the most common frame failures, damaged BB threads, is avoided by putting those on an economically replaceable component.

This will not be a popular reply…..

Did you set out with the intention of making it unpopular?  I'd rather share experience than concern myself with popularity.  My experience of EBB's (3 types), sliding dropouts (2 types), chain tensioners (3 types) and one type of horizontal dropouts, is that each has advantages and disadvantages, but none of them require much effort to use or maintain. On balance I prefer the clamp type EBB over all the others, though I'd rather the full split as used by Tout Terrain than the partial split used by Thorn. 
Like this:

[Andyb1]

Hi PH,
To answer your questions….

1. The Nomad frameset I bought new in 2021/22, so a MkIII?  It was sold to me as a frame that I could fit my 3 x 9 gearset to, but could change to Rohloff later if required.  I have read threads here about how the clamping bolts can dent the EBB and that this then gives adjustment problems - are you saying that denting is not a problem with the EBB on the MkIII Nomad?

2.  I realised my reply might not be popular as many here ride Thorn bikes with EBBs so presumably must be happy with the EBB design.  I just came to a different view point.

3. I totally agree with you that regular servicing of bikes is important - but the reality is that often this does not happen.  So corrosion at unseen places starts.   As shown by photo in this thread.

4.  I am not sure how water gets into the BB area from running down the seat tube if the seat tube has a capped end?   Personally I would be more worried that spray from the front wheel would get into the BB area through the slit in the frame.

5.  Agree with you that it is good that a failed EBB can be replaced rather than having stripped BB threads in the frame, but greasing the BB threads on assembly in a steel frame does seem to sort this potential problem out.  With no diss-similar metals between a steel frame and a plated steel BB corrosion will be less likely.

[PH]

are you saying that denting is not a problem with the EBB on the MkIII Nomad?

I can't see how it's even possible, which is what prompted me to question which frame you were talking about. 
EBB's have been around for a century, it's the usual way for adjusting the tension on a tandem timing chain.  Here's Sheldon Brown's  explanation of the types:
https://www.sheldonbrown.com/synchain.html
Or the summery "All three types work well, with reasonable care, and none of the designs would be a reason to reject one model of tandem or another."
I'd say the same about hub gear bikes and include the dropout type of chain adjustment as well.  Plenty of reasons for someone to choose one bike over another, but unless everything else was equal (Which it never is) basing that choice on how the chain is adjusted seems irrational.  The only method that might be considered inferior is using a tensioner, rather than moving the fixed points, even then the  disadvantages can be overestimated. 

  I realised my reply might not be popular as many here ride Thorn bikes with EBBs so presumably must be happy with the EBB design.  I just came to a different view point.

I doubt many Thorn users give it much thought, for most it just works without issue, for the few where there is a problem it's no more than with any other bike.  Coming to a different viewpoint won't be unpopular, I was asking what experience and knowledge you base that on and it turns out you've never used an EBB and had misunderstood how this type works.