Brompton rear frame hinge rod?

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SA_SA_SA
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Joined: 31 Oct 2009, 1:46pm

Brompton rear frame hinge rod?

Post by SA_SA_SA »

How good a repair is just replacing the pin in a worn rear hinge likely to be?
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Brucey
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Re: Brompton rear frame hinge rod?

Post by Brucey »

without wishing to appear too flippant, it depends on how worn the pivot spindle is.

I don't think replacing the bushings is anywhere near as bad as you might expect if you reduce the OD slightly and bond them in position; I think you can often avoid the reaming this way.

cheers
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rootes
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Re: Brompton rear frame hinge rod?

Post by rootes »

waste of time just doing the pin..

Also they tend to wear more on one side - I have worn 5 out to date on two different bikes - non-drive side always seems to wear more.

You always have to ream the bushes, they are designed to be oversize and to then make sure thay are reamed to correct for size but also to get them concentric after installation

also the kit comes with a spindle, bushes (inc flat nylon ones), new bolts and if you like a drill to remove the old stuck ones.

I reckon brompton would be better to increase the diameter of the pin and bushes a little to make them longer lasting..
Brucey
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Re: Brompton rear frame hinge rod?

Post by Brucey »

rootes wrote:You always have to ream the bushes, they are designed to be oversize and to then make sure thay are reamed to correct for size but also to get them concentric after installation...

if a greased new shaft is used as a guide during adhesive bonding of reduced OD bushes (they can be sanded down on the OD in a drill arbor) then reaming may not be necessary.

I reckon brompton would be better to increase the diameter of the pin and bushes a little to make them longer lasting..


yes; a grease nipple wouldn't go amiss either.... :roll:

cheers
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rootes
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Re: Brompton rear frame hinge rod?

Post by rootes »

yep a grease nipple would be good. interesting the Glacier acetal bearings used in in their normal industrial setting are recommended to be lubricated...

also I noted that Simspon cycles now in London do a collect, fix and return service for rear hinge, main hinge and stem hinge replacements.. and they do the work themselves as they are certified to do the work so no need to return the factory.
mjstrong
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Joined: 27 Jun 2021, 1:39pm

Re: Brompton rear frame hinge rod?

Post by mjstrong »

No idea where to ask this or if start new topic but as so brompton bushes topics i will ask here..

having done this several times when lived/worked on Bristol (Bike Shop we serviced lots of Bromptons)

I now live oop north😁 and decided do my own brompton after leaving it way to long and now find bush on drive side is so worn there is nothing for 7/16ths tap to cut thread into as first half bush non existent so nothing for tap to grip.. is it possible to get the frame where bush goes reamed out to accept new bush or am i looking at new frame here..
Last edited by mjstrong on 28 Jun 2021, 10:32am, edited 1 time in total.
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simonineaston
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Re: Brompton rear frame hinge rod?

Post by simonineaston »

Hmmm, got me thinking about my Brompton now... !!
(rides: Brompton nano & ever-changing Moultons)
rogerzilla
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Re: Brompton rear frame hinge rod?

Post by rogerzilla »

They can get corroded in and an M10, or even 7/16", tap rips out. Same problem.

The frame is not scrap as long as some bush is left. They are actually steel with brass facings and an acetal inner liner, so quite hard in the core. You have two options:

1. Get a bearing puller that will expand behind the bush and can then be used to drift it out. This is how Kinetics do it.

2. Carefully cut a slot in the bush with a junior hacksaw blade and then collapse it inwards with a punch (or awl). As soon as it loses most of its grip, it will knock out easily from behind. I did this two weeks ago where the bushes had been in for 16 years.
mjstrong
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Re: Brompton rear frame hinge rod?

Post by mjstrong »

Thanks for the answers gentlemen (i presume it is gentlemen 😁)
rogerzilla
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Re: Brompton rear frame hinge rod?

Post by rogerzilla »

On the subject of reaming, the special piloted reamer made for Brompton (by Trubor, marked 9.505mm which is, oddly, slightly under 3/8") is no longer sold to mere owners, presumably to give dealers more work. However, Brommieplus in Taiwan sell one which looks at least as good a design, if not a little better. It is also a fraction of the price, even after taxes and shipping.

The reaming is very easy with the right tool. Brompton say to only go in 15mm on each side to start with, and this turned out to be exactly right for the perfect fit. The Brommieplus one may be a little different in this respect, but the principle remains the same - don't run the flutes all the way through at first.
Sidlaws
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Re: Brompton rear frame hinge rod?

Post by Sidlaws »

rogerzilla wrote: 29 Jun 2021, 4:06pm On the subject of reaming, the special piloted reamer made for Brompton (by Trubor, marked 9.505mm which is, oddly, slightly under 3/8") is no longer sold to mere owners, presumably to give dealers more work. However, Brommieplus in Taiwan sell one which looks at least as good a design, if not a little better. It is also a fraction of the price, even after taxes and shipping.

The reaming is very easy with the right tool. Brompton say to only go in 15mm on each side to start with, and this turned out to be exactly right for the perfect fit. The Brommieplus one may be a little different in this respect, but the principle remains the same - don't run the flutes all the way through at first.
Has anyone bought or used this tool? I have a bog-standard 3/8" parallel reamer (non-piloted) which I was intending to use to ream the main-frame hinge bushings, but at £50 + whatever? for delivery I could be tempted by this...
hoogerbooger
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Re: Brompton rear frame hinge rod?

Post by hoogerbooger »

Do the pre-2004 SWB frames use the same rear triangle hinge bush & spindle kit ? can't seem to find anything online to confirm or not.

[ As it is looks like the bush and spindle replacement parts are becoming not available to home mechanics ? :

" This product must be fitted by us at our shop....." ( to quote one source: Brilliant Bikes)

I can see on youtube some advice on installation that may not be good on reaming using other tools.... which presumably may lead to imperfectly aligned/cut bushes & short longevity. But I can't see why Brompton should prevent sale ( if this is the deal for dealers now) ?...... just advise ( as they do) that this is a task requiring care and specialist tools to get right. I presume railure to use thread-locker on the screws could lead to a big problem if one backed out before the owner noticed....but I can't see why this risk can't be covered by clear advice and health warnings on the instructions.

( I see Condor charge £55 labour. While SJS don't provide a fixed labour charge)
rogerzilla
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Re: Brompton rear frame hinge rod?

Post by rogerzilla »

It's very easy with the Brompton reamer. 10 minute job. Getting the old bushes out can be a lot more grief if they have corroded in place and the tap just rips out.
drossall
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Re: Brompton rear frame hinge rod?

Post by drossall »

I've also done it with a borrowed tool, on a friend's bike. I've now got the tool and a spare kit in stock because of my own Brompton.

Shane Cycles have a good photo guide, but the killer trick that another shop pointed out, for stuck bolts, is that you can cut away the nylon washers with a Stanley knife. That gives enough clearance to put a hacksaw, carefully, through the old pivot. You're replacing it all anyway so it doesn't really matter, as long as you avoid damage to the frame.

Kinetics offer a slightly different approach.
rogerzilla
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Joined: 9 Jun 2008, 8:06pm

Re: Brompton rear frame hinge rod?

Post by rogerzilla »

The bushes are standard engineering parts available from Ashley Power, among others. The bolts are trickier, being strengthened steel, but I did find them. The nylon washers shouldn't be too tricky although it is a weird size.

Bushes: https://www.ashleypower.co.uk/06dx06-sp ... -1532-x-38

Bolts: https://www.ebay.co.uk/itm/141008261192

The spindle is fairly bespoke but (a) barely wears and (b) is made for Brommieplus in Taiwan if you get stuck.

The rear hinge is the same on older models. All dimensions are relentlessly imperial.

Anyway, SJSC will sell you all these parts at the current time.
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