From Tim at Bikes@Vienna ... a local Brompton dealer.

https://lovelybike.blogspot.com/2012/...-brompton.html

--Intro from the article--

Brompton folding bikes have remained virtually unchanged since they entered into production in the late 1980s. But before that happened, there was a small pilot run and the machines from this early batch were just a tad different. Only several hundred of these were made. Two of those recently ended up passing through Harris Cyclery on their way to the Brompton museum. And one of those I had the opportunity to photograph and ride. Pictured here is the 358th Brompton ever produced. Red and black 3-speed with upright handlebars, dynamo lighting, rear rack and fenders.*

I thought that the current Brompton bikes were an outcome of incremental improvements over many years. Learning that so much was already accomplished in the first design step makes me even more impressed.

thank you for that report. I would like to see a limited run of that frame,I think it is cool.

their Mk2 bike followed that .. they used a different bender, so as to smooth out the curve.

Cast hinge pieces came recently.. production volume need
exceeded the number of skilled fillet brazers to join forged hinge plates and tubes..

so the joint was redesigned and the production job de-skilled ..

Cast? Hmm, I wonder what the difference in strength is now.


Were the fillet brazed joints also dressed/cleaned-up? That's time consuming work.

Thanks for sharing. It is a bit like the original Thinkpad keyboard. You don't try to fix something that works so well. Apart from eliminating the humpback and machining a curved frame the fold concept has stood the test of time.

Unfortunately !

dont think the strength went down , there was some fatigue
on the brazed joint over time, Im told, so may be an improvement.

had a Mk2 which I have since resold. when I got a Mk4.

No, fillet build up is pretty smooth..
... they did the same thing all week long..

what the cast hinge assembly allows is a torch array jig, a production tool,
where the parts are heated in all directions, in alignment, to the brass melt point .
Lugged frames are similar in that regard. .. capillary penetration.

Thanks for the explanation, fietsbob. Good info.