Brompton saddle resists charm

General cycling advice ( NOT technical ! )
nez
Posts: 1809
Joined: 19 Jun 2008, 12:11am

Brompton saddle resists charm

Postby nez » 25 Oct 2014, 5:19pm

Well, I dont know how else to describe it. No 1 son has managed to pullhis modern plastic saddle apart simply by pulling the bike, I think. Tried as we might, we have been unable to get the rails back into the plastic chassis/saddle base. I'll append photos below and would be grateful for any hints as to how it should be done. The rail is hollow chro-mo.
saddlectc1.jpg

saddlectc2.jpg

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Sooper8
Posts: 796
Joined: 20 Aug 2012, 7:53am
Location: Midlands

Re: Brompton saddle resists charm

Postby Sooper8 » 25 Oct 2014, 6:44pm

A big pair of adjustable grips, to squeeze it in?

Edit- apologies, I just looked closer and realise you mean the front to back, not sideways - grips would be no good.
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nez
Posts: 1809
Joined: 19 Jun 2008, 12:11am

Re: Brompton saddle resists charm

Postby nez » 25 Oct 2014, 6:58pm

I've had a good look round mountain bike forums (where they get the problem by crashing) and I think the consensus is it's dangerous to attempt to fix it. Who wants loose metal spikes springing out next to your undercarriage? Hmmm. Good point.

TonyR
Posts: 5390
Joined: 31 Aug 2008, 12:51pm

Re: Brompton saddle resists charm

Postby TonyR » 25 Oct 2014, 7:02pm

I doubt very much that its the result of bending the rails and almost certainly a result of bending the top. I'd be inclined to try replicating how it came out. Clamp the rails back on the seat pin, hold the bike down and try pulling up on the back of the saddle and pushing down in the middle. I suspect it will bend, rotating the sockets for the rails backward and that with some extra help to apply downward pressure on the saddle you'll be able to guide the ends of the rails back into their sockets. Doing the same on the bench will probably be very difficult/impossible but take heart that it went together in the first place so must be able to do so again.

Brucey
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Joined: 4 Jan 2012, 6:25pm

Re: Brompton saddle resists charm

Postby Brucey » 26 Oct 2014, 12:09am

if you have two strong 400mm MTB seat posts (preferably of the two-bolt variety) clamped onto the saddle rails, ideally as far apart as possible, you can usually flex the frame into the right position to allow the top to be popped back on. Usually it is easiest to pop the front in, but whichever end requires the least flexing is best.

However if you get it back in, it may well pop off again if it takes another knock; you'll just have to see how easily this can happen.

cheers
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sreten
Posts: 347
Joined: 29 Sep 2013, 10:59pm

Re: Brompton saddle resists charm

Postby sreten » 28 Oct 2014, 1:45am

Hi,

Well first you undo the front *, and put the rails back in the rear.

Then you reattach the front, which should be relatively easy,
as the rails have managed to pop out of the rear, so it is bent.

So after the the two stages above, you need to apply some
brute force to straighten the rails, the more brute force
you need to apply the more likely as a fix it will work.

rgds, sreten.

* If the front is simply restrained and can't be undone,
itsmuch more difficult. Some ingenuity is required.

nez
Posts: 1809
Joined: 19 Jun 2008, 12:11am

Re: Brompton saddle resists charm

Postby nez » 28 Oct 2014, 12:32pm

If only. Im afraid the rails are rigid and hollow. Anything more than minimal bending would be disastrous.

TonyR
Posts: 5390
Joined: 31 Aug 2008, 12:51pm

Re: Brompton saddle resists charm

Postby TonyR » 28 Oct 2014, 3:08pm

nez dans le guidon wrote:If only. Im afraid the rails are rigid and hollow. Anything more than minimal bending would be disastrous.


As I said, its highly likely that bending of the rails caused the problem but rather one of bending of the saddle to rotate the sockets off the rails. All you need to do is visualise the process by which that happened and then reverse it.