Author Topic: Brompton rear hinge (Read 52491 times)

rogerzilla · « **Reply #50 on:** 18 March, 2017, 08:01:52 pm »

I used standard nutlock and, hundreds of miles of rough roads later, no movement. Just as well, because the RH one would be a tad tricky to retighten on a ride (unless you have a happy accident of chainring size and/or chainring cutouts).

chriscross1966 · « **Reply #51 on:** 22 March, 2017, 09:11:00 am »

Just a note to say I managed to get a rusty, mistreated (not by me) for several years and at least 8 years installed without lube pivot out of an early-ish Mk4 frame wihtout sawing or drilling last night...

Having got the first screw out (2 decent long-arm 4mm allen keys required) i used an M6x50 allen cap-head bolt with a spring washer and a nut. The bolt doesn't need to be in hard, but the nut needs to be down as tight as you can get it. I reckon it's quicker than the other methods, doesn't involve power tools (can be an issue for some folks) and more importantly, won't scratch up the inside of your rear triangle... Found the basic technique on youtube (you'll have to google it, I haven't got a link to hand). The guy in it was using a plain washer, I found that wasn't as effective as a spring.

chrisc

drossall · « **Reply #52 on:** 22 March, 2017, 01:39:44 pm »

That will lock up the side where you've removed the bolt. However, the issue is shifting the other bolt. When I tried, we rounded the Allen key. Next up, on advice from LWaB, is heating to weaken the Loctite. Or am I misunderstanding you?

chriscross1966 · « **Reply #53 on:** 22 March, 2017, 04:54:01 pm »

Quote from: drossall on 22 March, 2017, 01:39:44 pm

That will lock up the side where you've removed the bolt. However, the issue is shifting the other bolt. When I tried, we rounded the Allen key. Next up, on advice from LWaB, is heating to weaken the Loctite. Or am I misunderstanding you?

No that was what was achioeved. First get all the crap out of the allen recess in the countersunk bolt out with a pin or a very small allen key or similar small stiff poky thing. Then use a decent long-arm allen key and hammer the damn thing into the socket... I reckon if I can get the screws out of a pivot in that condition (and they had rusted a bit even though the whole thing is supposedly stainless) then it is possible anywhere... better be cos I need to get the aftermarket titanium set out of my highly modded H3R (now H11R) at the weekend, it's nearly brand new and I'm swapping the Kinetics triangle for a vostok.bike one.

drossall · « **Reply #54 on:** 22 March, 2017, 11:03:20 pm »

The 4mm would help too, as that's slightly over-sized of course. I'll look at that, maybe in combination with the heat.

Got to get on and do it in the next few weeks, but the owner and I have both been short of time. However, I was talking to LWaB at the weekend and have promised some action soon.

chagzuki · « **Reply #55 on:** 23 March, 2017, 01:49:17 pm »

Quote from: chriscross1966 on 22 March, 2017, 04:54:01 pm

... better be cos I need to get the aftermarket titanium set out of my highly modded H3R (now H11R) at the weekend, it's nearly brand new and I'm swapping the Kinetics triangle for a vostok.bike one.

You bought a titanium spindle? I was wondering about those, they only save 20 grams or so but cost about the same as a brompton rear hinge kit, so if titanium stands up to the abrasive forces adequately it might be worthwhile. Intuitively steel strikes me as a more suitable material but I don't really have a clue.

chriscross1966 · « **Reply #56 on:** 24 March, 2017, 08:49:49 am »

Quote from: chagzuki on 23 March, 2017, 01:49:17 pm

Quote from: chriscross1966 on 22 March, 2017, 04:54:01 pm
... better be cos I need to get the aftermarket titanium set out of my highly modded H3R (now H11R) at the weekend, it's nearly brand new and I'm swapping the Kinetics triangle for a vostok.bike one.

You bought a titanium spindle? I was wondering about those, they only save 20 grams or so but cost about the same as a brompton rear hinge kit, so if titanium stands up to the abrasive forces adequately it might be worthwhile. Intuitively steel strikes me as a more suitable material but I don't really have a clue.

IN my case it was purely vanity really.... Henrietta's mods were initially started with the aim of making my idea of a practical Brompton (an H3R) better.... My first Brommie was a secondhand M3L (a not unusual way to start off I expect) and after a couple of years I had a list of what I wanted different, the C2W scheme opened at work and I bought an H3R with dynamo lighting and front luggage... a few bits and bobs got changed around over the next five years, but mostly just detail stuff, but then I was in a position to buy anew bike and tried to list what I wanted different and it said "Henrietta, with more gears and lighter would be nice..."... The more gears came courtesy of an 11-speed Alfine conversion currently in a Kinetics frame, hopefully the recently arrived vostok.bike titanium frame will be going inthis weekend.... the "lighter" just turned into flinging carbon and titanium components from the mini-velo Brompton modding scene in the far east at her.... the last bits of that should be going on this weekend too, and at that point the only Brompton bits left will be the main frame and the handlebar stem.... so the titanium pivot was just part of that... Most of her old bits are going onto an old T3/L3 short wheelbase frame along with an 8-speed sturmey hub running fairly low gears as a shopping and load-carrying (for the allotment) bike..... I seem to have acaught the bug for Bropmton modding so in the workshop atm there's also an early Mk4 frame that's being setup with full Campy groupset and Cinelli drops... ploughing through the technical issues with that ATM, but it will fold with those handlebars, mostly thanks to the Kuosac 25mm tyres, that will be a weekend racer to annoy the Bianchi tifosi with (it'll be painted in celeste)..... and I've just ordered a Nickel S1E that's getting a 5-speed hub and a mildly ridiculous 80T front chainring as a shiny sunny days commuter...

chagzuki · « **Reply #57 on:** 24 March, 2017, 09:17:28 am »

Wow. Pics please!

Efrogwr · « **Reply #58 on:** 24 March, 2017, 11:08:34 am »

Quote from: chagzuki on 24 March, 2017, 09:17:28 am

Wow. Pics please!

Yes! Pics!

rogerzilla · « **Reply #59 on:** 25 March, 2017, 11:27:55 am »

And I thought my red S-type was pimped

The black M-type, in comparison, has no weight-saving gizmos at all, and almost leaves ruts in the tarmac. It's fine for the completely flat mile to SO's place, because it lives by the front door and is the only bike I have without SPDs.

Jurek · « **Reply #60 on:** 25 March, 2017, 04:28:06 pm »

Quote from: rogerzilla on 25 March, 2017, 11:27:55 am

And I thought my red S-type was pimped

The black M-type, in comparison, has no weight-saving gizmos at all, and almost leaves ruts in the tarmac. It's fine for the completely flat mile to SO's place, because it lives by the front door and is the only bike I have without SPDs.

My bold.
You need to keep up, Roger.

Chriscross's Henrietta is well documented elsewhere throughout the interwebs.
I've reeled in the modification work I've been doing on my Brommie as it has ventured into the-finances-of-owning-an-ocean-going-racing-yacht territory.(And I don't have access to a lathe at the moment - actually, I do. I've just remembered we have a Colchester Student in the workshop at work - running on 3-phase that'll take your arm off if you don't treat it with respect).
After which, it still remains a relatively heavy bike.
If ever this was cry for Brompton to get up to speed with the 21st century, and get jiggy with upping their production techniques to be capable of dealing with (the difficulties of) titanium, then this is it.
I reckon they're a company with sufficient clout / pedigree to raise the finance to R&D and put this into production.
If they were to do so, it'd put them way ahead of a game which they're already at the front of.
Alternatively, someone in the far-east will do so first.

Coming back to your post....
Not unlike yourself Roger, my Brommie is the only bike I have which I can get on and ride, without any adjustment to apparel.
On which basis alone, it continues to win, hands down.

drossall · « **Reply #61 on:** 17 April, 2017, 01:54:48 pm »

Quote from: drossall on 19 February, 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.

The JE James method worked well

drossall · « **Reply #62 on:** 07 May, 2017, 11:50:54 pm »

All done

It's actually really easy once the bolts are out or (as above) the pivot has been cut. This afternoon, we removed the old bushes, cleaned out the tube, fitted new bushes, reamed them (a few turns on each side, nothing more) and re-assembled the bike.

I've gone at this really carefully and taken several sessions, not least because of wanting to get the bike apart before borrowing the tools or ordering spares. Also I had to go round to the owner's house each time and take the right tools. With everything to hand and a bit of focus, it should be a relatively straightforward job.

All working brilliantly, and many thanks to LWaB. I'll see about returning your tools.

LittleWheelsandBig · « **Reply #63 on:** 09 May, 2017, 10:09:38 pm »

Glad to see that everything has ended well Mr D.

My mate in Oz will be checking this thread before doing a couple of Brommies out there.

Oxford_Guy · « **Reply #64 on:** 09 May, 2017, 10:50:28 pm »

Quote from: Jurek on 25 March, 2017, 04:28:06 pm

You need to keep up, Roger.
Chriscross's Henrietta is well documented elsewhere throughout the interwebs.

I've seen it in the flesh, it's a spectacular thing!

LittleWheelsandBig · « **Reply #65 on:** 19 August, 2020, 03:18:02 pm »

Well, that is a touch annoying. Trying to replace the extremely worn swingarm pivot on HK’s Ti Brompton resulted in the 5/32” Allen key (from B’s pivot kit) taking a set without loosening the bolt on one side. Trying the other side resulted in a larger set, also without loosening the bolt. One tool binned.

Wondering about the next step:
- Hacksawing through the bolts seems likely to damage the swingarm or frame.
- Drilling out both bolts meant a hell of a lot of drill sharpening the one time I needed to do it previously and I don’t have a bench grinder (or other grinder) here.
- Do I assume the metal is a little soft on this tool and try to break another Allen key? There was no sign of rounding out but I was leaning pretty hard on some extra leverage.

rogerzilla · « **Reply #66 on:** 19 August, 2020, 09:19:22 pm »

Cheap Wilko drill bits. Hand drill (egg beater type). Put all your weight on it and turn the chuck directly. Use cutting fluid if you like.

LittleWheelsandBig · « **Reply #67 on:** 19 August, 2020, 09:44:51 pm »

Used up every 1/4” drill bit in the house and just squeaked through both sides. Bushes removed, replaced and reamed, swingarm refitted, Loctite curing.

Ordered three cobalt drill bits for future use but will keep your tips in mind. Won’t bother with 5/32” Allen keys in future, just the Bondhus 4mm.

drossall · « **Reply #68 on:** 19 August, 2020, 10:33:28 pm »

Too late now, but when I borrowed your tool I successfully picked up a tip from the Internet. This argued for cutting away the nylon washers/bushes. This creates enough gap to put a hacksaw throught the pivot. Very easy.

See for example here, although I found the idea on a shop's site, illustrated with photographs.

LittleWheelsandBig · « **Reply #69 on:** 19 August, 2020, 11:28:00 pm »

I though about that option but was a little dubious of avoiding accidental damage. I might have been happier doing it if only only one bolt wouldn’t loosen.

Gattopardo · « **Reply #70 on:** 20 August, 2020, 10:28:39 pm »

Quote from: LittleWheelsandBig on 19 August, 2020, 03:18:02 pm

Well, that is a touch annoying. Trying to replace the extremely worn swingarm pivot on HK’s Ti Brompton resulted in the 5/32” Allen key (from B’s pivot kit) taking a set without loosening the bolt on one side. Trying the other side resulted in a larger set, also without loosening the bolt. One tool binned.

Wondering about the next step:
- Hacksawing through the bolts seems likely to damage the swingarm or frame.
- Drilling out both bolts meant a hell of a lot of drill sharpening the one time I needed to do it previously and I don’t have a bench grinder (or other grinder) here.
- Do I assume the metal is a little soft on this tool and try to break another Allen key? There was no sign of rounding out but I was leaning pretty hard on some extra leverage.

Having had the 'fun' of doing this, have you got access to heat. The loctite set stuff they use on the bolt takes alot of heat to break have heated the allen key to get heat in to the bolt. Have also used a impact driver with sucess.

LittleWheelsandBig · « **Reply #71 on:** 20 August, 2020, 10:36:42 pm »

The problem has already been solved this time round but an impact driver is probably the quickest option. Carefully applied heat would certainly work but I worry (probably unnecessarily) about nearby things.

Max-Brompton · « **Reply #72 on:** 10 January, 2022, 10:13:21 am »

Hi guys, very pleased to join here and just to say hello and apologise for pulling up a slightly old topic but I wanted to join the forum as this is the most useful discussion on this particular subject that I have found.

After 45 years fiddling and fixing bikes I have just tackled my first Brompton hinge pin bush refurb and it did not go too badly.

To add in a few other points for others who might stumble across this excellent resource:

Like everyone else one bolt will come out fine, one will remain stuck. I really did not want to go anywhere near the pin with a drill so used the blowtorch on a sacrificial Allen key method to directly transfer the heat to the bolt and then half a dozen attempts with an M6 bolt and two locknuts (also a large penny washer and rubber washer against the rear frame - pictured) locking the other side as per YT video below. M6 is not exactly the correct thread but goes in and locks up fine. Took quite a few goes but eventually it will lock up the boltless side enough for the other side to free off.

I used an M10 tap to go into the old bushes but beware of going too far as the bushing depth areas are reamed out to around 11.75mm and the inner section of the rear frame pivot tube is narrower at around 10.75mm.

One thing that concerns me about the set up is that the SS pivot pin as others have noted sits against the inner face of the rear frame and will cause wear. I really don't know why Brompton don't refine this with a 'through axle' and cartridge bearings into the rear frame.

Where the pin meets the rear frame is also where the opposite of the countersink is deepest for the bolts so there is not much metal there.

I wondered about adding a thin form 'D' large 0.8mm SS washer to each side as a 'sacrificial' surface for the pin to sit against? See pic - any thoughts on this? good or bad!

Not sure there is enough tolerance to take the extra 0.8mm thickness each side though as I measure my pin at only 0.4mm less than the inside rear frame.

Rather than the factory super HD thread locker I'd much rather use a very light Loctite or none at all and check regularly for wear etc this way.

A very useful YT video here:

https://youtu.be/PZS_wtoNu8c?t=524

Also these links:

https://chestercycling.wordpress.com/2012/08/29/brompton-rear-frame-replacement/

https://www.perennialcycle.com/shopcast/replacing-brompton-rear-hinge/

http://www.shanecycles.com/brompton-hinge-repair/

Reviews/comments here: https://www.sjscycles.co.uk/consumables-brompton/brompton-rear-hinge-bush-kit-inc-spindle-tools-etc-workshop-use-only-note-on-ordering-comments/

https://www.brommieplus.com/portal_c1_cnt_page.php?owner_num=c1_343119&button_num=c1&folder_id=40985&cnt_id=862315&search_field=&search_word=&search_field2=&search_word2=&search_field3=&search_word3=&bool1=&bool2=&search_type=1&up_page=1

PICS:

rogerzilla · « **Reply #73 on:** 10 January, 2022, 10:51:09 am »

If the bolts are tight and threadlocked, the sleeve cannot move against the "ears", so doesn't wear them. It happens sometimes on Moultons with bronze bushes, where the sleeve seizes to the bushes and then the rear end rotates on the bolt, causing wear, but a Brompton sleeve is highly unlikely to seize in the plastic-faced bushes.

I just drill the heads off the old bolts with a cobalt drill.

An M10 tap will sometimes rip out with badly corroded bushes. The best option is a 7/16" tap, which is what Brompton used to supply when they would sell you a reamer.

Max-Brompton · « **Reply #74 on:** 10 January, 2022, 11:56:26 am »

Thanks Roger, in hindsight the 'wear' on mine is I think just the paint and a maybe a fraction into the metal but only on the RH side which I think suggest it happened by being ground slightly against the pin when trying to lock it up with the lock bolt a few attempts - the LH turned back forth a few times before it finally gave way.