Custom lots-of-titanium Brompton

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  • I can understand why. Making something from carbon is fundamentally different from making it from steel or even ali given the nature of the material. If you just copy the design but make it from carbon instead then it's very unlikely to work well. I've done a fair bit of work with carbon myself, both wet lay-up and pre-preg (vacuum-bagged in a home-made curing oven) and the only way of making a Brompton-esque frame from carbon would involve high pressure moulds. That would require either an autoclave or inflatable internal bladders, and even a simple mould (machined from a large block of aluminium billet) would cost tens of thousands to produce. Making the fixtures like the frame clamps and pivots together with the pivot tube for the rear triangle would be a total nightmare in carbon.

    In some ways carbon would be an ideal material for a Brompton - the stiffness would be useful given that it's essentially a single beam frame. But in lots of other respects it'd be a disaster, I suspect.

  • I reckon it'd be great but they know what they're doing with tubing and the costs sound prohibitive if they can't make it work so I can understand their reaction to the question.

  • I can't see that the ramps and pins will have any effect, but if the lowered teeth are a problem (and at present I suspect they won't be)

    I'll never ride s/s with a geared ring again.

    There's a transit van driver somewhere in Glasgow that'll be able to explain why.

  • I'll never ride s/s with a geared ring again.

    Same here. The gravel rash healed, but the bib-tights I wrecked cost more than a good SS chainring.

  • Chain break?

  • No, just jumped off as I was caning it up a small slope.

  • Oscc

  • It was a jacket, front light, front rack, 2 brake levers and a saddle for me.

    And almost my life.

    All items that individually cost more than a basic ss ring and together, a lot more than a good one.

  • @ OP So ... let me get this straight ... you need lots of gears to achieve +37mph on a Brompton up a slope that's a pond? Weird.

    I'd build your own plastic one, go on, it's there for the taking.

  • i like this project. really looking forward to seeing how it turns out. put a smile on my face.

  • It was a jacket, front light, front rack, 2 brake levers and a saddle for me.

    And almost my life.

    All items that individually cost more than a basic ss ring and together, a lot more than a good one.

    Odd, because my SS MTB uses the standard geared middle ring, and I've never had any problems with the chain dismounting. Mind you, my track bike and fixed-gear bikes both have SS chainrings, so to err on the side of caution, a 52t Miche 135BCD chainring is winging its way to me. Means I'll have to use a 1/8" chain rather than the 3/32" one I had set aside, but that's no great hardship, although I suppose I may as well get a 1/8" sprocket for the SA 5-speed hub rather than the 3/32" one I've got at the moment.

  • I've used gear components to run ss in the past too without much hassle.

    It only takes one instance of seeing a tranny can struggle to find the grip required to stop before squashing your head to convince you it's a ss chainring is a worthwhile investment though.

  • Not that proper equipment makes you completely immune to chain drop. I had the chain off my TT bike once on a bumpy downhill section, and to head off the OSCC, I had to undo the track nuts to get it back on so there was nowt wrong with my chain tension.

  • Heh. That's my one! Better more recent pic of it here with racing wheelchair tyres and Aerohead rims:­28174_312ccc20aa_b.jpg

    [Thanks for the props!]­/3093828174/in/set-72157615886030030

  • That is such a sick set-up. Love it.

  • I'd like to race that

  • ^

    Oh and these look great. My dad's ones are quite wide (stake wheels I think) and sometime catch on my trousers.

    I bought some of those luggage wheels a couple of years ago, unfortunately whilst they look lovely I found they were very unstable and the rubbers came off within a couple of weeks.
    If only they were a little thicker they would have been great.
    I bought some of these in the end and they have been great, very stable and hardwaring.

    Rest of the build looks great!

  • The standard QR seat clamp on the Brompton, which came with the main frame, is good for two reasons. Firstly, it stays in place and doesn't spin round due to the fact that there's a slot in the steel seat clamp which forms part of the main frame and a matching ridge in the QR seat clamp. Secondly, it fits and is designed to work with the steel band brazed around the seat tube.

    But it's a bit boring and fugly, so I decided I'd replace it with a Hope QR seat clamp. However, the Hope seat clamp doesn't have the ridge to keep it in position, and the shaft on the QR lever is too short. So the first thing to do was to disassemble it.

    In order to keep the QR lever from spinning round when it's undone, I got a spare bit of brass tube out of the offcuts bin, machined a recess in one end on the lathe which the brass bush from the Hope QR lever fits into, and milled the locating ridge on the other end. This is part way through the machining process on the lathe:

    I also needed to make a longer pin for the QR lever, with 5mm threads at both ends but a 6mm diameter in the middle (to match the rear triangle release catch), so I used a long stainless 6mm bolt and turned it down to suit. I also had to machine down the Hope aluminium nut. Reassembled, it looks like this.

    And in place it looks like this:

    Took hours to do, of course. And the Hope sign on the QR lever is still upside down...

  • nice seeing the process steps

  • Looks good, I'd suggest possibly replacing the silver nut that came with the Hope QR as the aluminium is very soft and has a habit of stripping.

    I like upside down logos (This is irrelevant but I thought I'd share).

  • I have lathe envy

  • If it does then I'll machine a new pin with an M6 thread on one end and M5 on the other and just use a standard M6 nyloc to replace the Hope ali nut. But it can stay for now, 'cos I think it's mighty purty...

  • I have lathe envy

    It's in the dining room, along with the milling machine, pillar drill and TIG welder...

  • It's in the dining room, along with the milling machine, pillar drill and TIG welder...

    wtf. pics pretty please. I'd love to live like that. I think.

  • What an epic "man house".

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Custom lots-of-titanium Brompton

Posted by Avatar for Brommers @Brommers