Allen Key Brand - to protect bolt head on Rare EBB

[531colin]

You can use the existing Allen key; just grind off the broken bit, but don’t get it hot!
I would be looking for a way to increase friction between frame and eccentric without wringing the head off that bolt.
Carbon assembly paste?
If the eccentric has a sliding wedge arrangement can that be improved?
The death knell of EBBs is if they start to rock.Theres a fairly recent thread on EBBs I’ll have a look for it if I fire up the PC.

[Nearholmer]

I do recognise the design flaw in needing to tighten it so much, and i guess why so few bike adopted this style of EBB. As well as my bike i've only ever found one model (a chumba) which uses the same EBB.

Can you point a to a picture, or even better a diagram, f the way this all fits together?

I’m trying, and failing, to visualise it, with the hope of being able to suggest a fix that avoids needing to tighten a screw to the degree that you have to now.

[Brucey]

so the bolt is crucial,eh? One suggestion is to make sure you get the biggest bang for your buck, tightening-wise. This means good grease (with solid lubricants) on the wedge surfaces, screw threads etc. and perhaps some carbon grip paste on the outside of the insert. The other thing that might also help is to leave the eccentric away from the 90 deg. point at which the chain will exert the greatest torque on the BB insert.

Of course it almost goes without saying that if there is space for a shim you should fit one. Even a turn of Al tape might help. However, steel isn't especially grippy, so not all shims are created equal, even if they are the same thickness. A thin shim of annealed copper would be nice; but a thicker shim might also let you use a slightly smaller eccentric insert too. If the hole in the frame isn't exactly circular, ream it until it is, even if it means the hole ends up a little oversized and you need a different shim.

In the longer term.I'd recommend that you trade the 'special bolt' for a studding + spacer + nuts arrangement, if possible. Not only will this allow easier tightening, but it will also take the fear out the whole thing; it will never get truly stuck because you can always cut the nut off and renew the studding.

[LuckyLuke]

Hi, I like Bondhus brand allens.
Much nicer in use than a Halfords or Draper set I had. The ball ends were a better fit.
Bondhus have a colour coded set that I’ve found to be a nice touch. Especially when your workbench (kitchen table) is as messy as mine…
Makes sense splashing out on tools like allens which one uses frequently.

Best wishes,

Luke

[st599_uk]

Wera are nice, they aren't traditional hex to prevent rounding out bolt heads and the entire tool set they produce has consistent colour coding for size.

[drossall]

I've just ordered a Wera on the basis of recommendations here and elsewhere, for the hinge bolts on my Brompton.

[slowster]

The bolt in question, is the bolt which tightens up an wedge type EBB. Its an incredably rare EBB with a 51.2mm OD...I'd need to take it out again to double check but I believe the bolt has a flange about halfway down the shaft.

If the thread is interrupted by a flange (or is not continuous), I suspect that on one side of the flange the thread is reversed. The Bushnell eccentric bottom bracket similarly uses a bolt with normal and reverse threads to push the two wedges away from each other (see photographs in the link below). However, the bolt in the Bushnell eccentric bottom bracket does not have a flange, and I would guess that your EBB uses a slightly different design/specification from the Bushnell eccentric bottom bracket to avoid falling foul of any patent/design copyright (so I doubt you could use a Bushnell bolt, even if you could buy one separately).

https://cdn.shopify.com/s/files/1/0754/ ... 1683832210

[Jupestar]

Some photos below.
It looks like the flange is there to ensure the non drive side wedge gets pulled back. The flange is fixed. Between the flange and the bolt head is non threaded. The rest is normal thread.

I reckon you could replace the bolt with a full threaded bolt and lock nuts. But you would have to destroy the bolt to get it out. The head is fine and the Wera is doing the job as recommended. I'll keep it as is.

If/when the bolt gets stripped and the EBB is in the frame it's going to be an absolute pig to get out.

I don't think I can get any sort of shim in.

I will continue to handle with care and enjoy every commute.

[Jupestar]

[Jupestar]

You can use the existing Allen key; just grind off the broken bit, but don’t get it hot.

I thought about this. For at least 5 seconds.

Then I realized a decent 5mm Allen key was likely to be less than a £10. And my ability to grind the one I have straight and true was dubious at best.

Then I considered the reasonable worst case, which was scrapping the frame.

I feel the Wera was worth the £8 or £9 I spent.

[Jupestar]

studding + spacer + nuts arrangement

Struggling to understand what this is.

[Jupestar]

The death knell of EBBs is if they start to rock.Theres a fairly recent thread on EBBs I’ll have a look for it if I fire up the PC.

My other frame has grubber screws, and is a bigger OD much easier to find think it's 53.8. I read some where that wedge style was better. So I oce replaced the EBB with a wedge. The thing would slip all the time. And didn't take long till I stripped the bolt. And £30 was in the bin. I put it down to being conned by marketing and went back to the grubber screws EBB.

I've had the grubber screws head stripped and that's a real pain. I have a whole bag on them now, any slightest fear on the head and the grubber is binned.

[Nearholmer]

Thanks for the pictures; I get it now.

I can think of several completely different ways of designing the arrangement to prevent the eccentric rotating, but TBH I’m at a bit of a loss to suggest ways of preventing the arrangement you have now from slipping.

The best I can come up with is to use paste with metal filings or fine sand in it, electrical jointing paste for instance, or possibly coating the exterior of the eccentric with contact adhesive, then dabbing it into a tray of fine sand/filings.

[cycle tramp]

Deleted

[Pebble]

I suspect the wedges don't run true when tightening, my guess is they will probably angle upward and only form a small contact area. Using abrasives could make this worse

Maybe - File the leading edge of the wedge so it is less likely to bind. Use lots of oil on the plastic to plastic surface, may be soap on the metal to plastic surface (soap possibly looses it slippieness after a week or two?). And then when tightening, half a turn in, quarter of a turn back, some very light tapping with a hammer to create a little viabration. that may get the wedge to move further and create a wider contact area.

At the end of the day it is a poor design, the wedges should be moving outwards to grip the outside, rather than inwards to create a centre high spot for it to wobble on

If all that fails I would explore the BB to see if there was room to tap two holes and then bolt the thing into the frame,