Author Topic: Brompton rear hinge  (Read 23482 times)

Re: Brompton rear hinge
« Reply #75 on: 10 January, 2022, 01:35:12 pm »
Good post with all the links. But I think you should point out explicitly that your BrommiePlus link is to a reamer that is (a) available for sale and (b) cheaper than the official Brompton one.

Re: Brompton rear hinge
« Reply #76 on: 10 January, 2022, 02:24:25 pm »
Coincidentally, I ordered one a few days ago.

I used a standard hand reamer, long enough to go through both sides, when I last did a Moulton F-frame.  In theory the bushes on those should be just right when fitted, but they are all made by little cottage industry suppliers now, so mine were a little tight.  It can be tricky to find one where the parallel section of the flutes is long enough.
And Darkness and Decay and the Coronavirus held illimitable dominion over all.

Re: Brompton rear hinge
« Reply #77 on: 10 January, 2022, 02:52:42 pm »
Good post with all the links. But I think you should point out explicitly that your BrommiePlus link is to a reamer that is (a) available for sale and (b) cheaper than the official Brompton one.

Ahh, if any rules have been broken I apologise - I'm happy with a basic adjustable reamer bought on eBay in the UK TBH - proceed with caution and it's reasonably easy and precise enough.

I'm still thinking of adding SS washers - getting anal nerdy here but I'm measuring the following on my Brompton:

Front frame width 68.40mm, + 2 x nylon washers (1.55mm thick) so total 71.50mm, pivot pin 71.80mm in length, 'OLD' rear frame 72.40mm so 0.6mm to play with.

So if adding 2 x 1mm SS washers (between pin end and rear frame) you'd only need to mill say 0.55mm off each end of the pin, use 1.0mm nylon washers and adding the 2 x 1.0mm SS washers it would be spot on with exactly the same 0.15mm excess each end of the pin and the fitment down to 0mm gap.

Errrrrrmmm...I think...    ;D

Re: Brompton rear hinge
« Reply #78 on: 10 January, 2022, 05:59:33 pm »
Not at all. I simply meant that you've found a more reasonably-priced, and available, reamer, which various people have been looking for. But that wasn't apparent until I followed your link out of curiosity to see to what you were linking. No broken rules that I know of, and anyway it's not my place to enforce any.

Re: Brompton rear hinge
« Reply #79 on: 13 January, 2022, 12:35:16 pm »
If anyone is interested in following this I'll pop up some updates.  As I say I might get the spindle and tolerances tidied up a bit but as the paint was a bit uneven anyway I carefully took off the main thickness with a soft aluminium edge and tidied up the traces with a rather Heath Robinson dare I say '400 grit facing tool' but more to give a nice clean surface to measure from.  It's actually pretty blooming flat now with just a couple of thou' across the face.  Just tighten up and turn the squares gently to clean things up.




Re: Brompton rear hinge
« Reply #80 on: 13 January, 2022, 02:27:16 pm »
The nylon washer performs three functions:

1. Allows for unevenness in the faces of the pivot tube and "ears"
2. Provides a thrust bearing
3  Improves sealing against water and dirt ingress

If you compare a Moulton rear end, they use flanged bushes to provide a thrust bearing but the length of the sleeve is ever-so-critical to give free movement without play, and the sealing is sufficiently bad that they provide a grease nipple.  The Brompton design has its merits; it's just a pain to overhaul.
And Darkness and Decay and the Coronavirus held illimitable dominion over all.

Re: Brompton rear hinge
« Reply #81 on: 13 January, 2022, 03:44:44 pm »
Good points.  I'm very tempted to not use Loctite at all and have it freely accessible for access to the rear end not just the 'bearing'.  As you might have guessed  ;D I'm an inveterate tinkerer/fiddler/checker/experimenter and pretty much check bolts etc habitually so torqued up right and checked often there is no concern.

Re: Brompton rear hinge
« Reply #82 on: 13 January, 2022, 04:13:00 pm »
Bear in mind that the RH bolt is usually inaccessible if it comes loose during a ride.  You sometimes get lucky with chainring cutouts.
And Darkness and Decay and the Coronavirus held illimitable dominion over all.

Re: Brompton rear hinge
« Reply #83 on: 13 January, 2022, 04:52:43 pm »
Bear in mind that the RH bolt is usually inaccessible if it comes loose during a ride.  You sometimes get lucky with chainring cutouts.

Sure, TBH I have never carried a 5/32" Allen key anyway ;D but might start...