Main frame hinge 6.35mm pin

[rogerzilla]

Another factor is probably the significant leverage afforded by the atypically long stem on Bromptons compared to other bikes.

Yes, and the use of steel with a lower yield strength. Oddly, 1960s Moultons were made from real gaspipe (ERW steel, i.e. seamed tube) but it's rare to find a loose lower cup on those. The suspension no doubt absorbs a lot of the rocking motion that would stretch the head tube. The lower head cup on a Moulton is also bigger in diameter - it's a unique unobtanium size, but closer to 1 1/4" than the 1 1/8" on a Brompton.

 

[neilrichardson55]

well after long sleepless hinge dreaming nights.

ive had the frame hinge welded together ( im going to keep it i know it does no longer fold as small but i used to like riding it some it lives a as half folder. it might make a planter in the garden time will tell :-)

 

[wafter]

Crikey!

 

[Fastpedaller]

well after long sleepless hinge dreaming nights.

ive had the frame hinge welded together ( im going to keep it i know it does no longer fold as small but i used to like riding it some it lives a as half folder. it might make a planter in the garden time will tell :-)

if it's cast is the weld likely to last? If the welder had used the correct filler it should be ok.

 

[neilrichardson55]

Most prob not going to ride it just keep it. Yeah it should hold I’m going to repaint it and do something nice for it’s retirment lolol

 

[brommieinkorea]

Wonder if there's any evidence to support this claim by Brompton - would be interested to hear of any.
I have no plans to purchase a trifold, but keep an eye on developments in this area, as I have an interest in a lot of bike related stuff.
Singapore looks like the epicentre for trifolds of a similar design to Brommies, but with options like disk brakes, 20" wheels, and even belt drives. As said, not hearing of any hinge failures on them, and no idea of how folk would go about remedying such things if they occur.
All the non B trifolds I've seen on video appear to be TIG welded, and all look very neat to me. Can anyone explain why B choose to braze?

Brompton braises because it is easier to get right with respect to not overheating the affected area and creating stress lines over time. Most Chinese frames that fail do so at or on a weld, but lots are alluminum and thus tend to have a little less fatigue cycle strength too.

 

[brommieinkorea]

Crap. So I read this thread without much interest because I had yet to experience this with the Bromptons. Today , I noticed once again the main frame latch is working itself loose. Normally when a Brompton comes down with a problem, I put it in storage, grab a fully functional one, then deal with it after some contemplation and procrastination. However I'm currently "on tour" with only one Brompton (2016 S6R) in Japan. So I grab the frame about the hinge and there is considerable play. Tightening the clamp considerably mostly stops it. Hinge looks like it has a half mm of mis alignment/ pin fit slop. Is this likely to do anything horrible, like snap and kill me? Will it make it another 500 miles, and then I can fit an oversized pin ? Does anyone believe Brompton Junction Kobe could fix this in a day ?

 

[Fastpedaller]

Could it be that over-tightening hinge clamps until they are ineffective (I'm not directing this at the Op or previous poster) gives rise to or at least exacerbates hinge wear?

 

[neilrichardson55]

Crap. So I read this thread without much interest because I had yet to experience this with the Bromptons. Today , I noticed once again the main frame latch is working itself loose. Normally when a Brompton comes down with a problem, I put it in storage, grab a fully functional one, then deal with it after some contemplation and procrastination. However I'm currently "on tour" with only one Brompton (2016 S6R) in Japan. So I grab the frame about the hinge and there is considerable play. Tightening the clamp considerably mostly stops it. Hinge looks like it has a half mm of mis alignment/ pin fit slop. Is this likely to do anything horrible, like snap and kill me? Will it make it another 500 miles, and then I can fit an oversized pin ? Does anyone believe Brompton Junction Kobe could fix this in a day ?

It’s ware in the pin if you are lucky it’s the pin that’s warn it’s just a new same size pin. If it’s warn the casting it will be a obersize pin if there is more that .3 mm play it’s a new frame the claps could be a fact they need to be replace every few years they ware this cases the problem with the pin

 

[rogerzilla]

It’s ware in the pin if you are lucky it’s the pin that’s warn it’s just a new same size pin. If it’s warn the casting it will be a obersize pin if there is more that .3 mm play it’s a new frame the claps could be a fact they need to be replace every few years they ware this cases the problem with the pin

If you read the whole thread, it's more complicated than that. It seems some hinge pins turn in the frame where they should be held firmly, causing early failure.

 

[brommieinkorea]

Could it be that over-tightening hinge clamps until they are ineffective (I'm not directing this at the Op or previous poster) gives rise to or at least exacerbates hinge wear?

I actually replace hinge clamp plates before they bottom out, just like Brompton says to do. Usually I don't crank down on 'em , but in this case the movement of the frame seemed a bit much. I'm sure eventually I'll remove the pin, put a micrometer to it, and determine the appropriate course of action. One tends to get attached to an aging bike especially when it's travelled the globe with you, so I hope it isn't terminal.

 

[neilrichardson55]

If you read the whole thread, it's more complicated than that. It seems some hinge pins turn in the frame where they should be held firmly, causing early failure.

Yes I’ve seen that. Why I said it sometimes worce case it wares the casting past the repair point but when that happens it’s bad repair replacement that causes that. The way the pin is just pressing it in should lock it then the tool splays out the pin ends.
It’s the two big things with Brompton it’s the main hinge and rear triangle hinge.

My main hinge failed scrapping the frame it was not pin movement it was the main part of the hinge casting took passed the biggest 6.35 pin

 

[brommieinkorea]

6.35mm ? So what's the diameter of the original pin ( before it's trash of course)? ?

 

[neilrichardson55]

6.35mm ? So what's the diameter of the original pin ( before it's trash of course)? ?

orginal is 6 mm then 6.1 then 6.35mm as long as not to much damage is done so you have .35 mm max ware. depending on damage you should be able to change 2x