Brompton - advice on rear fold problem after Nano conversion

u_i

Active Member
Location
Michigan
to make room for a 10sp cassette wheel i had to widen the rear triangle.
What is the chain slack situation for you after the fold? When I tried to mount a conventional rear derailleur on Brompton, I found that its tensioner struggled to pick up the chain slack, unlike the standard Brompton tensioner. My situation was additionally complicated though, compared to yours, by multiplying the front rings that added to the maximal slack. Have you had any issues in mounting the rear derailleur/mech?
 

Schwinnsta

Active Member
But in the OP case just the front was modified. In your case just the rear.
 

kais01

Regular
Location
Sweden
(ot) u_j, as you may see on the photos, slack chain hangs itself over the seatstay while folded, but remains tensioned around the derailer. not ideal, but it works. this is somewhat made easier by positioning the left crank rearward before the fold. start out by folding the left pedal inside the rear triangle (ditch the pump). in folded state left pedal will then end up downward, which as a side effect makes carrying the folded bike much easier. and also no more stains above the knee on your trousers:smile:

had originally planned for an extra tensioner sitting on the lower jockey wheel like steve parry or birdy, but have not got around to it..

have a long-cage dura ace derailer and a merida s1 hanger which is positioned over the wheel axle, inside right fork member, wheel dished accordingly.

hope ts soon gets his nano brommie up and running!
 
OP
B

Blaugrana

Über Member
Location
North London
Is the fold not going all the way round because one of your chain stays is catching on the frame? Is the rear end that far out?

I must admit, it looks all kind of wrong to me in the picture. The tyre is what should be butting up against the seat tube (and the main frame tube when fully folded), yet yours looks like the mudguard would hit the seat tube first. They haven't fiddled with the brakes and put the mudguard on the wrong side of the brace have they?

[...] this is where the wheel should be when fully folded.

View attachment 472504
Thanks Kell.

I'm doing the fold right, but my rear wheel is over an inch from the main frame. Something very wrong, but I am baffled as to the cause. I hope I have not blamed installer unfairly.

Mudguard is on right. Stays not catching.

I have now spoken to main nano people and they are being very helpful and seem willing to resolve this.

Thanks to all.
I hadn't seen recent replies as an email notification went to spam.
 

chriscross1966

Über Member
Location
Swindon
Am I going mad or have you put your seat down before folding the rear wheel under, and therefore the post is catching on the frame stop. Thats whats stopping your fold.... seat down is last move on the fold.
I am sure that a competent mechanic could weld up the crack in your frame (seat post tube) then grind it back down flush to save you buying a new one, they are only mild steel.
No they can't the heat from the welding buggers the brazing of the frame joints. Ive got a frame on a bike i bought that has had that happen and its horrific. The way to fix the crack is to drill a stopping hole at the end of it, make sure the tube is round then braze a small piece of slightly bigger tube over it. I also have a frame where that has been done and its fine. Don't let a welder anywhere near a Brompton, you need a proper brazer.
 
OP
B

Blaugrana

Über Member
Location
North London
No they can't the heat from the welding buggers the brazing of the frame joints. Ive got a frame on a bike i bought that has had that happen and its horrific. The way to fix the crack is to drill a stopping hole at the end of it, make sure the tube is round then braze a small piece of slightly bigger tube over it. I also have a frame where that has been done and its fine. Don't let a welder anywhere near a Brompton, you need a proper brazer.
Thanks ukoldschool. I need to get a second opinion as to whether the main frame really is cracked. I can't see anything there.
 
OP
B

Blaugrana

Über Member
Location
North London
Update.

Today I took a new Brompton B75 and my converted old Brompton to Nano's main workshop. There I was welcomed by the boss and an engineer and they had a look at my old bike.

They couldn't see anything wrong with the installation or anything else to cause the folding problems.

They then, kindly, took the Nano kit of my old Brompton and fitted it to my new B75, which I rode and folded without problems.

So, chapeau to Nano for sorting out the problem.

Thanks also to Graham for his advice and offer to fix my old Brompton.

Thanks to Velorution for suggesting a B75.

Thanks all here for your helpful contributions.

I will, in a few weeks, look at what needs to be done to the old Brompton and whether fixing it would be worthwhile.

Fingers crossed - my Bavarian Bike Bummel is back on.
 

ukoldschool

Well-Known Member
No they can't the heat from the welding buggers the brazing of the frame joints. Ive got a frame on a bike i bought that has had that happen and its horrific. The way to fix the crack is to drill a stopping hole at the end of it, make sure the tube is round then braze a small piece of slightly bigger tube over it. I also have a frame where that has been done and its fine. Don't let a welder anywhere near a Brompton, you need a proper brazer.
I agree witht he hole drilled at the end of the crack, but not on the weld point unless you mean gas welding old school style?
I've done it myself with a MIG and it didnt affect the braze at all, I was careful to only do a cm bead at a time and quench the heat (think the crack was about 3/4 inch from memory, it was a long time ago...)
 

chriscross1966

Über Member
Location
Swindon
Looks like whoever had a go at the one ive got was using MIG... brazing really isnt intended to be near anything that hot, theyve then tried to mig the failed joints and the frames just fallen apart.
 
Top Bottom