Main frame hinge 6.35mm pin

[rogerzilla]

I have a degree in engineering and I find the rear hinge/pivot quite offensive too - but, compared to the Moulton hinge on which it is undoubtedly based, it lasts remarkably well. The Moulton hinges use Oilite or plastic bearing bushes whereas the Brompton uses small, but rather more complex, mixed-material glacier bushes which are designed to retain grease and have an enormous load capacity per square mm. The main practical issue with the Brompton design is that it is not easily serviced or replaced using standard tools.

Sorry, not entirely on-topic, but it fits the "poor design that usually holds up ok" theme.

 

[wafter]

I have a degree in engineering and I find the rear hinge/pivot quite offensive too - but, compared to the Moulton hinge on which it is undoubtedly based, it lasts remarkably well. The Moulton hinges use Oilite or plastic bearing bushes whereas the Brompton uses small, but rather more complex, mixed-material glacier bushes which are designed to retain grease and have an enormous load capacity per square mm. The main practical issue with the Brompton design is that it is not easily serviced or replaced using standard tools.

Sorry, not entirely on-topic, but it fits the "poor design that usually holds up ok" theme.

Snap

That said I think the back one is far, far better thought out than the front - at least it uses replaceable bushes so removes the wear faces from the frame itself.. while also avoiding the situation on the front that requires the frame to essentially be damaged every time a new pin is fitted and the splined section driven into the frame itself.

It seems the big issue with the rear hinge is the need to remove both bolts - if you attack both at the same time the more stubborn side holds allowing the less secure bolt to be extracted, but then you're unable to restrain the hinge pin's rotation to allow the remaining bolt to be removed, so have to drill the head off...?

Still, far less nasty than the lash up on the front though. I'm concerned that the loose splined end of the pin has at worst made future replacements non-viable if it's enlarged the hole in the frame; at best meant that I'll have to go up several sizes of pin to get something to engage (potentially only for it to happen again).

Trying to explain this situation to a probably technically-vacuous customer service muppet at Brompton (who probably has a brief to fob off such claims as "wear") is certainly no fun.

 

[FrankCrank]

Brompton have often claimed the hinges are very hard to get right and are where most clones fail

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?

 

[neilrichardson55]

Yeah, as much as the setup makes my inner engineer sick in his mouth you can't argue with that innings. Sadly mine appears like it will last nowhere near as long as that, or that it's failed in the way one might expect through legitimate wear.

That's interesting about the failure mode; I've since read that cast steel "isn't brittle" however I can't see a piece of ductile "normal" steel failing in the way you describe. I assume a bit actually fractured and fell off..?

I'm not necessarily suggesting it had already been weakened; more that the example I saw elsewhere was resulting from accident damage so not necessarily a suggestion that it's excessively weak; just prone to a questionable failure mode.


Yes, I'd expect the factory to have some sort of jig that attaches to the frame / clamp somewhere to ensure everything lines up during this process.

My response from Brompton
Hello Neil,

Thank you for contacting us here at the Brompton factory.

Based on the information provided, the 6.35mm hinge pin is the largest we offer, and once this does not fit the hinge anymore, the next thing to be done is to replace the frame.

However, based on the age of your Brompton, our frames have developed over the years, and our newer frame parts are incompatible with your model, meaning that to replace the mainframe, you would also have to replace the front forks and the stem, as these would not be compatible.

The costs of replacing all these frame parts, cables, and the servicing involved would be an approximation of £700+; if you'd like, I can get an exact figure of all the parts that would need replacing and a quote attached to that, although it would still not be a total price due to us not having the bike in person to provide an exact figure.

In similar situations, we usually recommend the purchase of a new Brompton instead of the repair costs for your Brompton, which may be more than half of the price of a new model. However, we understand the connection between the owner and their bikes, if you wish to have this repaired,

 

[wafter]

My response from Brompton
Hello Neil,

Thank you for contacting us here at the Brompton factory.

Based on the information provided, the 6.35mm hinge pin is the largest we offer, and once this does not fit the hinge anymore, the next thing to be done is to replace the frame.

However, based on the age of your Brompton, our frames have developed over the years, and our newer frame parts are incompatible with your model, meaning that to replace the mainframe, you would also have to replace the front forks and the stem, as these would not be compatible.

The costs of replacing all these frame parts, cables, and the servicing involved would be an approximation of £700+; if you'd like, I can get an exact figure of all the parts that would need replacing and a quote attached to that, although it would still not be a total price due to us not having the bike in person to provide an exact figure.

In similar situations, we usually recommend the purchase of a new Brompton instead of the repair costs for your Brompton, which may be more than half of the price of a new model. However, we understand the connection between the owner and their bikes, if you wish to have this repaired,

Pretty much as I was expecting and as much as detest their customer service department currently, I think that's a pretty fair and informative response.

I guess there are other avenues but none particularly appealing - flog it as a spares or repair, break it for parts, use the bits to build up another used frame of a similar age...?

I can't see a lot of value in the rest of the bits, although you never know - there may be a market for owners of older bikes if they can't get appropriate parts new.

 

[rogerzilla]

I didn't realise they'd changed the front end of newer frames. Have they finally dumped the quill stem?

 

[neilrichardson55]

You are right it will be going to scrapper but wheels brakes and seat post and bits off worth I will keep I still have a 2006 bike and might buy a burnt orange new one. 1700 for 10 years maybe ?

 

[wafter]

I didn't realise they'd changed the front end of newer frames. Have they finally dumped the quill stem?

They did change the stem format but it's still the quill; I think there's a bit about in my thread on mine; perhaps went from a tapered expander to a wedge..?

You are right it will be going to scrapper but wheels brakes and seat post and bits off worth I will keep I still have a 2006 bike and might buy a burnt orange new one. 1700 for 10 years maybe ?

That's a shame, but it is what it is. I wonder if you could get some benefit from it before it's scrapped - section it along its length for science perhaps? Certainly worth keeping all the bits anyway.

Not sure they still do burnt orange - think it was replaced with the (IMO inferior) pinkish "fire coral".. also, shop around - I believe some places are doing discounts on some models..

 

[Gunk]

It may be worth trying to find a decent lightly used bike instead, £700 buys quite a lot of used Brompton

 

[rogerzilla]

I've bought several as projects but, with the exception of one, they were too good and needed very little work! Bromptons out here in the provinces tend to be very lightly used. Those in the Home Counties can get absolutely hammered from train-based commuting, with lots of folding, scratches from luggage racks, and all-weather riding.

Besides the hinges, an apparently loose headset can be a stretched (belled) head tube, so check for rocking with the front brake held on. Gap-filling bearing adhesive between the lower headset cup and frame buys you some time but there is no real fix for this when it happens.

 

[Gunk]

I've bought several as projects but, with the exception of one, they were too good and needed very little work! Bromptons out here in the provinces tend to be very lightly used. Those in the Home Counties can get absolutely hammered from train-based commuting, with lots of folding, scratches from luggage racks, and all-weather riding.

Besides the hinges, an apparently loose headset can be a stretched (belled) head tube, so check for rocking with the front brake held on. Gap-filling bearing adhesive between the lower headset cup and frame buys you some time but there is no real fix for this when it happens.

Very true, both project Bromptons I have bought from London over the years were both completely knackered.

 

[FrankCrank]

I've bought several as projects but, with the exception of one, they were too good and needed very little work! Bromptons out here in the provinces tend to be very lightly used. Those in the Home Counties can get absolutely hammered from train-based commuting, with lots of folding, scratches from luggage racks, and all-weather riding.

Besides the hinges, an apparently loose headset can be a stretched (belled) head tube, so check for rocking with the front brake held on. Gap-filling bearing adhesive between the lower headset cup and frame buys you some time but there is no real fix for this when it happens.

On a couple of klunkers I've built, a loose headset cup was remedied with a shim cut from a drinks can.
I expect this bodge may invalidate the warranty on a B.

 

[wafter]

On a couple of klunkers I've built, a loose headset cup was remedied with a shim cut from a drinks can.
I expect this bodge may invalidate the warranty on a B.

Seems like a viable stop-gap while waiting for a legit warranty claim, that can easily be removed before inspection.

 

[rogerzilla]

I've used a beer can shim to get a Raleigh upper head cup into an ISO frame with a Raleigh fork. The problem with a Brompton head tube, which has no lugs or reinforcing rings, is that it will keep stretching in use and eventually you'll need another wrap of beer can.

It's been known for decades that lugless or welded frames need external reinforcing rings to prevent head tube stretch, but plenty of manufacturers ignore this. It takes a lot of miles to happen, and chances are the bike has been sold on by then so the warranty is void.

 

[wafter]

I've used a beer can shim to get a Raleigh upper head cup into an ISO frame with a Raleigh fork. The problem with a Brompton head tube, which has no lugs or reinforcing rings, is that it will keep stretching in use and eventually you'll need another wrap of beer can.

It's been known for decades that lugless or welded frames need external reinforcing rings to prevent head tube stretch, but plenty of manufacturers ignore this. It takes a lot of miles to happen, and chances are the bike has been sold on by then so the warranty is void.

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