Author Topic: Brompton rear hinge  (Read 19876 times)

LittleWheelsandBig

  • Whimsy Rider
Re: Brompton rear hinge
« Reply #25 on: January 08, 2017, 02:42:23 pm »
I have the tap needed to remove the old bushes but have to get a stainless grease nipple and appropriate tap before swapping the bushes on my Brompton.
Wheel meet again, don't know where, don't know when...

Re: Brompton rear hinge
« Reply #26 on: January 08, 2017, 03:12:51 pm »
So what reamer do you plan to use?

I was chatting to a friend today who is a very competent engineer (but not a cyclist). He wasn't sure how important precise alignment would be in a journal bearing for such an application, but said that, if it were him, he'd look to ream the bushes first, then fit them to the spindle, and only then fit them to the frame, as this should help with alignment.

He also said, interestingly, that the wear tends to be to the steel, because the softer parts flex rather than wear.

LittleWheelsandBig

  • Whimsy Rider
Re: Brompton rear hinge
« Reply #27 on: January 08, 2017, 03:49:57 pm »
A standard fixed reamer, unless I can find a proper Brompton reamer for sale somewhere in Europe for not more than £200.

Reaming before fitting the bushes is pointless as the bushes change internal dimensions as they are pushed into the frame. His method would work if the bushes were a close clearance fit and bonded in place. Having to push the bushes in from both sides also makes it difficult to fit them to the pivot before the frame.

He is right about wear to the pivot rather than the bushes.
Wheel meet again, don't know where, don't know when...

Re: Brompton rear hinge
« Reply #28 on: January 08, 2017, 04:11:03 pm »
Interested in where you source the fixed reamer from, especially if you find one with a pilot - and in how you get on. Still think this is an interesting project.

LittleWheelsandBig

  • Whimsy Rider
Re: Brompton rear hinge
« Reply #29 on: January 14, 2017, 05:03:25 am »
Ordered a Brompton reamer from outside the UK. It is all starting to come together.
Wheel meet again, don't know where, don't know when...

Re: Brompton rear hinge
« Reply #30 on: January 14, 2017, 08:23:58 am »
This thread is useless without pictures ;D

Re: Brompton rear hinge
« Reply #31 on: January 16, 2017, 07:32:43 pm »
The Cyclecare man said to me that new bushes don't always need reaming - he always tries the fit first.  He's done two frames for me and ISTR that one wasn't ever reamed after rebushing.
And Darkness and Decay and the Coronavirus held illimitable dominion over all.

Re: Brompton rear hinge
« Reply #32 on: January 16, 2017, 09:28:07 pm »
Maybe that answers my question?

It's a bit puzzling really.

Brompton sell bush and spindle kits, which are quite widely stocked. These only make sense for the home mechanic, because a shop wouldn't need a new drill and Allen key every time. However, DIY fitting isn't recommended.

LittleWheelsandBig

  • Whimsy Rider
Re: Brompton rear hinge
« Reply #33 on: January 28, 2017, 11:20:09 am »
The semi-mythical Brompton reamer actually made it to my door. Who'da thunk?

https://pbs.twimg.com/media/C3QMN3QXAAAhihV?format=jpg&name=large
Wheel meet again, don't know where, don't know when...

Re: Brompton rear hinge
« Reply #34 on: January 28, 2017, 03:09:45 pm »
Nice to see what one looks like :thumbsup:

Re: Brompton rear hinge
« Reply #35 on: January 28, 2017, 07:56:52 pm »
How much did it cost from the non-uk dealer?

LittleWheelsandBig

  • Whimsy Rider
Re: Brompton rear hinge
« Reply #36 on: January 28, 2017, 08:11:35 pm »
160 Euro plus postage. The package also had a tap to remove the old bushes, which I didn't know was included.
Wheel meet again, don't know where, don't know when...

Re: Brompton rear hinge
« Reply #37 on: January 28, 2017, 10:47:23 pm »
Pricey! I've been meaning to change the bushes on mine for the last 3 years (!)... last time I started to have a go at it I couldn't rotate one of the hinge bolts so figured it must have been loctited to the rear frame (i.e. a messy loctite job that spilled over). Not sure what to do about that; I tried hitting an allen key with a hammer to loosen it but to no avail. The bike was bought second-hand so I don't have an option to have a dealer or brompton fix that.

Edit: then again, if that were the case it ought to be loctited to the powder coat and that should flake off under force. Which makes me wonder why I couldn't budge it last time I tried.

Re: Brompton rear hinge
« Reply #38 on: January 29, 2017, 12:44:41 am »
The advice seems to be that you may well need to drill it out. One place I've seen recommends a hairdryer or heat gun (mind the paint) to help break the seal on the Loctite on the bolts. Google for more advice.

Re: Brompton rear hinge
« Reply #39 on: January 29, 2017, 11:13:02 am »


One day they'll wake up, smell the coffee, and use some sort of cartridge needle bearing.

 ;D

They're made in Great Britain.  I remember when that meant quality.  ;D

That was about 1851, no?
Sic transit and all that..

LittleWheelsandBig

  • Whimsy Rider
Re: Brompton rear hinge
« Reply #40 on: January 29, 2017, 12:01:38 pm »
Pricey!

Yes but I got annoyed enough to pay it anyway. Once our three Brommies have had their bushes replaced, it'll just about have paid its way.
Wheel meet again, don't know where, don't know when...

Re: Brompton rear hinge
« Reply #41 on: January 29, 2017, 01:08:12 pm »
Pricey! I've been meaning to change the bushes on mine for the last 3 years (!)... last time I started to have a go at it I couldn't rotate one of the hinge bolts so figured it must have been loctited to the rear frame (i.e. a messy loctite job that spilled over). Not sure what to do about that; I tried hitting an allen key with a hammer to loosen it but to no avail. The bike was bought second-hand so I don't have an option to have a dealer or brompton fix that.
It's a standard job that you can pay a dealer to do. It doesn't matter that the bike is second hand, because it's not a warranty job. However, see my recent post in this thread - at least one source suggests heating to loosen the grip of the Loctite. Otherwise, you drill the bolt out with the drill bit that comes with the replacement bush kit. Various walk-throughs linked here.

Re: Brompton rear hinge
« Reply #42 on: January 29, 2017, 01:11:21 pm »
One day they'll wake up, smell the coffee, and use some sort of cartridge needle bearing.
I've wondered that. There must be a reason why this is the chosen design, but it seems pretty obvious that replacement will be needed and it doesn't seem designed to be replaced, if so many bolts have to be drilled out.

Re: Brompton rear hinge
« Reply #43 on: January 29, 2017, 04:39:01 pm »
Brompton use a particularly psychotic grade of Loctite, I think.  The actual torque specified for the hinge bolts is pretty low.  I fitted mine with normal nutlock, torqued them as specified, and they've never come loose.  I got the shop to fit the bushes but said I wanted to fit the rear triangle myself, mainly so I could guarantee some grease went in there.

Drilling them out requires a few spare HSS bits (6.5mm), a lot of pressure, and low revs.  You want to try and avoid heating up the bolt, which can make it even harder.  An "egg whisk" hand drill works well if you put all your weight on it and turn the chuck rather than using the crank handle.
And Darkness and Decay and the Coronavirus held illimitable dominion over all.

Re: Brompton rear hinge
« Reply #44 on: January 30, 2017, 01:08:49 pm »
I've been giving the problem of stuck hinge pins some thought and think I've come up with two ways to solve the problem. The first will get out the current fitment, and the second won't just prevent it being an issue in future but will also improve the maintenance...

1: Make a locking bolt up put into the end that comes undone first.... This is a bolt that is drilled down the middle into which a small screw is screwed down, wedging the screw in place.

2: Drill and tap the pivot tube on the outside to take a grease nipple and cross-drill your pivot hinges in future. To remove all you need to do is unscrew the grease nipple adn put a small tommy bar through the hinge-pin to lock it into place.... They could do this at the factory, it would cost pennies, but make it a lot easier to service in future....

chrisc

LittleWheelsandBig

  • Whimsy Rider
Re: Brompton rear hinge
« Reply #45 on: January 30, 2017, 01:13:23 pm »
#2 on your list is a certainty for my Brommies. Steve Parry has done that sort of thing for many years.
Wheel meet again, don't know where, don't know when...

Re: Brompton rear hinge
« Reply #46 on: January 30, 2017, 10:22:59 pm »
So is the problem less that the bolts get irredeemably stuck, than that one bolt shifts and then the other spins with the spindle? In that case, this method would make a lot of sense. Maybe that's what chriscross1966 is describing, though it's a nut on a bolt and I'm not sure what the drilling down the middle is for.

Re: Brompton rear hinge
« Reply #47 on: February 04, 2017, 09:19:14 am »
So is the problem less that the bolts get irredeemably stuck, than that one bolt shifts and then the other spins with the spindle? In that case, this method would make a lot of sense. Maybe that's what chriscross1966 is describing, though it's a nut on a bolt and I'm not sure what the drilling down the middle is for.
I was going to fit a grease nipple but there isn't a very obvious place to do so.  It's all tight curves or welds around that tube.
And Darkness and Decay and the Coronavirus held illimitable dominion over all.

Re: Brompton rear hinge
« Reply #48 on: February 19, 2017, 09:37:09 am »
JE James have an interesting take (scroll down) that, as an alternative to drilling out bolts, you can cut away the nylon washers and use the resulting space to cut through the spindle.

I'm beginning to use this thread as a place to store all useful links on this :)

Should be looking at the Brompton I mentioned this afternoon - first investigation of whether the bolts will move.

Edit: average score, from what I can gather. One moved, one rounded.

Re: Brompton rear hinge
« Reply #49 on: March 16, 2017, 12:22:10 am »
JE James have an interesting take (scroll down) that, as an alternative to drilling out bolts, you can cut away the nylon washers and use the resulting space to cut through the spindle.

I finally serviced my brompton rear hinge today. I delayed it by around 2 years... the waggle in the rear didn't really worsen much over that time until a week or two ago, when I decided it was too risky to leave it any longer.

One of the bolts was stuck firm so I set about drilling it. I'd bought a couple of drill bits to use besides the one that comes with the Brompton hinge kit and I figured that'd see me through the process. But I should've researched how to sharped drill bits... I hadn't realized that would be necessary; it's not something I've done before. After about an hour of drilling and having gotten about halfway through I figured I'd try the process mentioned above. It didn't seem particularly easy to cut the washer with a knife so I used an oscillating tool, and also cut some way into the spindle. But in no time the oscillating tool blade was completely blunted and I tried a hacksaw instead. It looked to me as though I was managing to avoid contact with the frame but once I'd cut all the way through (it didn't take very long) it was clear that I'd damaged the frame to some degree... and I don't think this was particularly avoidable using this method. But I think it's really just the powdercoat, and most of what was damaged is on the inside of the hinge, i.e. not visible.

I did the reaming with a standard hand reamer thing... it didn't strike me that this was significantly inferior to using the special brompton reamer. Perhaps using the Brompton reamer would give a result with slightly greater longevity, the tolerances being fractionally tighter. But the end result that I've achieved appears to be waggle free and good enough.

I used loctite 243; I hope this is adequate. I really don't want to have to be drilling bolts again, it's a ludicrous thing to have to do. A staggering shit design. So fingers crossed the medium strength threadlocker will be adequate.