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Are Brompton unhinged?
They've spent a LOT of time and money designing a new, improved hinge for their folding bike. Here's their photo documentary of a hinge going from raw casting to finished frame...
First their press release:
Brompton makes 100K investment in manufacturing capacity and reaffirms commitment to UK manufacturing in London.
The company has invested heavily in the redesign of the principal hinge on the world recognised Brompton Bicycle. The investment was driven by several key factors;
· Capacity; With the existing work force and workflow management, Brompton Bicycle Ltd was approaching maximum capacity. The introduction of the new hinge has increased capacity by 10% across the company.
· Efficiency; The capital investment in design, machinery and training has been high, but the new method for manufacturing & brazing is more cost effective. This improved efficiency is estimated to pay back costs within 3 years.
· Quality; The new socket braze hinge has double the fatigue life of the existing butt braze.
· Wheel Base; The design of the new hinge gave an opportunity to increase the length of the wheel base on the Brompton by 30mm, improving comfort and ride quality.
The 'Hinge Project' has touched all aspects of the company, in total some 25 jigs have been redesigned on CAD, over 250 frame parts have been tested, 500 transportation boxes modified, a CNC machine, Hydraulic press and Shot blaster purchased, all of which has required planning, training and commitment from the Brompton Team.
ends
From casting to cycle
The hinge was designed using AutoCAD Mechanical Desktop 6, resulting in two 3-D solid models for each side of the hinge. The models were then sent to a rapid prototyping facility, to generate resin models built up from 0.1mm layers, using laser technology. These models could then be sent to the iron foundry to make up aluminium patterns for production castings:
Raw hinge castings
The next challenge was to machine the castings to an accuracy of +/-0.3mm, on 4 axes, including boring, drilling, reaming, tapping and special cutters, all to be complete in 90 seconds! The solution was a HAAS VF-1 CNC machine with integrated 4th axis. As with all things Brompton everything is unique, requiring bespoke fixturing, tooling and programming. The result was a light aluminium cube, holding a hinge on each face, light enough to handle, designed to give access for the different tools (all modelled on CAD prior to actual use) and based on a simple 3 pin arrangement for solid positioning.
Operator loading raw hinge casting on to aluminium CNC fixture
The hinge is then machined: here a tap approaches the casting to create a screw thread:
Tap approaching hinge, clamped on aluminium fixture
The machined hinges are then prepared for brazing into the frame tubes:
Machined hinges, fluxed, ready for autobraze
Then the automated brazing process itself:
Hinge approaching melt temperature in autobraze flame array
The result is cleaned up, painted and ready to go in a new Brompton frame:
New hinge on painted frame
Posted on 12 December 2003
Your comments ...| From: Brendan ([email protected]) on 12 December 2003 |
| Have they taken this opportunity to put a stop of some sort on the clamp bolts, to prevent them vibrating loose and falling off in transit. If not it's a pity. |
| From: Murph ([email protected]) on 12 December 2003 |
| I wasn't aware that this was a problem...? Mind you I've only had my Brommie 11 years (-: |
| From: Ben - Kinetics ([email protected]) on 13 December 2003 |
The vibration is only a problem if you don't tighten up the clamps before travelling. A thin locknut on the inside cures it as well, but it is a bit of a non-problem...
Thanks for the pics Pete - Brompton told me about this a while ago, but it's good to see what it looks like. |
| From: Helge SCHYDLO ([email protected]) on 13 December 2003 |
If someone invests such a lot of money in aquiring fancy gadgets like CAD-design and CNC-mills,one would expect something more tricky,more innovative than this new hinge,which still takes a lot of time to handle.It reminds me of ancient,oldfashioned ship-engineering of the 18th century.Go and have a sharp look at your Formula-1 industry.They´ll show you.Sorry Brits,you can do better.
Regards from Helge,an anglophil and incorrigible Bromptonaut |
| From: Ralf Grosser ([email protected]) on 13 December 2003 |
Brompton is a company that always amazes me.
Unlike their competitors, they do most of the production of frames and frameparts themselves.
In todays age of outsourceing, they are still comited to produce in England instead of buying their stuff from Asia.
Ralf Grosser
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| From: small wheels bad (@ home) on 14 December 2003 |
| Now all they need to do is add larger wheels and a diamond frame - then they'll have a proper bike. |
| From: Ralf Grosser ([email protected]) on 14 December 2003 |
Someone is missing the point here.
A Brompton is a Smallwheeler to take on the train or in the boot of a car.
THis reminds me of the story that at a Bicycle trade fair, Dr, Alex Moulton was ask when he would start building susspended bigwheelers.
Poeple still don^t understand that for a susspension to work well smaller wheels are better because the susspension works better if you keep the unsprung weight down.
As for largewheel folders, well some suspended bikes with big wheels have folded under the riders without having been designed to do so.
Some people working a local junkyard are amazed how many aluminium frames they get to recycle.
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| From: Roger the Hilldodger (@cyclemagic) on 14 December 2003 |
It was a joke! Aimed at Rabid Jason.
But I don't like most small two wheeled bikes, and yes I have tried them and Cyclemagic ownes several. I just don't like them. |
| From: Steve ([email protected]) on 14 December 2003 |
| Although I can see the advantages to Brompton in greater production efficiancy, are there any real practical advantages to the user? |
| From: murph ([email protected]) on 15 December 2003 |
| The wheelbase is longer - one assumes that Brompton believe this will make the bike ride better so yes, there is intended to be an advantage to the user. |
| From: Peter Clinch ([email protected]) on 15 December 2003 |
| If double the fatigue life (as trumpeted in the blurb) isn't an end-user advantage then you wonder just what they have to do to impress people. And as for they could do better with their high powered CAD and computer mills, if someone could think of a better design to do what the Brompton does they've had about 15 years and not managed yet... It's good to see they're not just resting on their well deserved laurels and continue to tweak a great machine even better. |
| From: BRUCE ([email protected]) on 15 December 2003 |
I just ordered a new Brompton, which arrives this week, here in the U.S. I am very curious to know: When WILL / DID this newly redesigned hinge appear in production Brompton bikes?
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| From: Dave Holladay ([email protected]) on 16 December 2003 |
As a Brompton owner & user since 1989, and very nearly a Mk 1 owner in 1980, I think I know a fair bit about the bike.
The major failure mode after the rear triangle was fixed, and the main frame Y improved with a load spreading flange has been the main hinge & clamp. This casting follows on from the new steerer clamp casting which was introduced about 2 years ago. I've lost count of the number of front frame sections collapsing on me. None has failed at speed, and there is ample warning of impending collapse, which once it starts can be rapid, but rarely total. The new hinge overcomes a major stress raising problem in the massive change in section where the tube meets the casting, and HAZ issues in the old production process - that said I've had no problems over the past year, and that is probably also due to the fact that I've not had a trailer towing rig on the road very much (this arrangement puts severe loads on the front clamp & hinge, especially when your all-up-weight is around 250Kg (rider 95Kg, front carrier 25Kg, Trailer box & load of tyres 80-90Kg, Bike rack for bus 30+Kg)
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| From: BRUCE ([email protected]) on 16 December 2003 |
| QUESTION -- Can anyone tell me when the re-designed main hinge start appearing on Bromptons? Thanks. |
| From: Rainer ([email protected]) on 16 December 2003 |
| The German importer told that within eight weeks all bikes will have the new hinge. This was in mid of November. |
| From: andy scaife ([email protected]) on 17 December 2003 |
Great to see a brilliant product being refined, as has already been said. It would be easy for Andrew Richie to let the bike sell itself and go for a long holiday somewhere, but this constant evolution is a sign of a healthy company. It's just a pity we spent £600 on a new one only the other month. B****r!
The Brom reminds me of my old 1966 Morgan car. It looks like a modern Morgan, but when you put the two together, there is not one component in common. Same with Land Rovers, but that wasn't the case with the Mini, and look what happened to that horrible old box. I'm surprised how few bicycles there are in that same position. Windcheetah obviously, Trice and Dawes Galaxy. Handbuilts like the Mercian as well, but others like Moulton and the model-names like the Stumpjumper have basically carried a name through to different machines.
I know Hilary Stone has done a 'design classics' spot in that racy-boy magazine C+, but there might be a place for an occasional 'icon' piece in VV. |
| From: Mikes245 ([email protected]) on 18 December 2003 |
The bigger wheel-base is a great development but Brompton do need to look at the design limitations that prevent decent gearing systems being available. Since the bike first appeared in the late 80s bike gearing has been transformed yet the Brompton has hardly evolved.
The six-speed was a move in the right direction - but for about the same price, £600, you can buy a Dahon 24 speed using the Sram 3x8 system. The Brompton may fold better but with gear ratios from 22-112 inches you can ride the Dahon anywhere. |
| From: andy scaife ([email protected]) on 18 December 2003 |
| And I've got a Dahon as well and I don't like it one little bit. I find it a floppy thing with no charm. Deraillers have no place on a folder. Brom should be looking at the new Sturmey Phoenix 8, and I hope to hell they are! Ours will be getting one built into it as soon as they're available. I think a gripshift would be an improvement as well. It suits Brom's market, as well as being one less sticky-out bit. The new colours should help dispell the 'besuited Mister Sensible' image, too. My daughter wants a mauve one, but having six bikes at 12 years old is quite enough I think. (Jacob (8) has a christmas KMX coming though!). |
| From: Mikes245 ([email protected]) on 19 December 2003 |
What a silly comment - "derailleurs have no place on folders". The overall functionality of a bike is determined by its gearing. If your low gear is 40" then you can ride to far fewer places than if you have a 22".
I hated my Brompton - the riding position was dreadful, the brakes (this was in 1991) had little stopping power, and it had only three gears. I got rid of it when I first acquired a Moulton APB. The only good thing it did well was fold. I've now got an APB Dual Drive 24 which I can pedal anywhere. Having a wide range with lots of intermediate gears is so liberating and the APB is much pleasanter bike to ride.
A long wheel-base Brompton with a Rohloff - well that might be attractive. |
| From: andy scaife ([email protected]) on 22 December 2003 |
| Re my comments about my Dahon...Dual drive APBs are indeed fine. As a Moultoneer myself you'll find no argument from me. However, when we go to France we can get 5 Bromptons into our car roofbox. We can also take the Broms onto crowded trains on our weekly Friday trip to our cottage. I've been turned away with a Moulton. I used to be a proper 'gearing fascist' myself, and I still advocate triples to my roadie friends, but I love my little Sturmeys, (I never seem any slower on rides with a single or 3-speed either). My 'Rescue bike Number 1'(see vv11)has a Sram Spectro 5, and has pulled the trailer with 3 bikes up a few nasty hills. Number 2 has a DualDrive which needs constant lubrication, and that's why deraillers have no place on a folder. Too much oily gunge on your clothes (and fellow train passengers). The choice with folders is either wear old shorts all the time or get some leg muscles. |
| From: Dave Minter ([email protected]) on 22 December 2003 |
It is a little unfair to compare an early model Brompton with a current competing machine. I recall early Dahons being rather dubious machines by any measure.
Having vast numbers of gears on a bicycle is not entirely necessary. The human body can produce power over a remarkable cadence range with little effect on efficiency. Refer to virtually any study on cadence vs efficiency.
Anything that can be bumped on a folding bike will get hit eventually, a fact of life unless you are rather more careful than I care to be. Rear derailleurs are an obvious 'delicate' item on a bike.
To add to the 'noise', a Rohloff Brompton can be obtained from Steve Parry, for a suitable price, slightly increasing folded width. |
| From: andy scaife ([email protected]) on 22 December 2003 |
| Or you could try a current 6-speed Brom (DP brakes, fine even down French hills) with a Speed-Drive. Anyone tried it? |
| From: Ben - Kinetics ([email protected]) on 23 December 2003 |
| You really can't compare a Brompton with an APB - they're totally different bikes for totally different purposes. For what it's designed for, the Brompton is fantastic - if you want to do serious touring or off-road, then buy something more suitable (like a Birdy or APB) - jsut don't expect it to fold as quickly or easily. |
| From: Mikes245 ([email protected]) on 23 December 2003 |
As I've got nearer to 60 the thing that you notice you lose is not your staminia but your stength. On the flat I can still keep up with my son who is half my age and ride on all day. But when it comes to hills I need the low low gears more than he does. The Brompton 6 speed with reduced gearing gives a 36 inch bottom which is still too high.
The Brom's foldability is still unsurpassed even though it was designed in the 1980s - but for me I need a broader range of gears. I hate to think what a Steve Parry Rohloff would cost - but it does appear to be very attractive. |
| From: Ben - Kinetics ([email protected]) on 24 December 2003 |
| The Speed Drive is a very good option - giving you a much wider range and a smaller, neater chainset. Also very easy to fit... |
| From: Mikes245 ([email protected]) on 24 December 2003 |
By my calculation putting a Mountain Drive on a Brompton 6 speed would give the following gears:-
16, 18, 22, 25, 30, 34, 40, 46, 55, 63, 75, 87.
Not quite the range of a Rohloff; and not quite the even spacing but a simpler and much cheaper solution.
Would having three separate gear systems reduce efficency?
Very interesting and worth considering.
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| From: J Turvey ([email protected]) on 31 December 2003 |
I have a 5-speed Brompton with a Mountain-Drive to give 10 gears of:
94, 79, 62, 49, 42,
37, 32, 25, 20 17.
No overlaps or duplicated gears and the range is really almost too wide - I use the 94 inch gear only rarely, and the 17 inch gear is almost too low to balance the bike.
Fitting the Mountain-Drive was relatively straightfrward, and one I got the chain alignment right it has worked without any problems. |
| From: Mikes245 ([email protected]) on 31 December 2003 |
Ben's suggestions of using the Speed Drive with a small chainring seems to give a much better range and spacing compared with the Mountain Drive.
With a 30t chainring on a Brompton L6 you get:-
24 28 33 38 40 45 46 52 54 63 74 86
Such a set-up makes the Brompton a very attractive proposition. The down side is that you have to use THREE separate gear systems and I would imagine that this takes some getting used to and I would be interested to hear from other cyclists to find out whether this is as diffifcult as it appears.
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| From: andy scaife ([email protected]) on 01 January 2004 |
well i'm currently rebuilding an f-frame Moulton with a 4-speed sturmey and a speed drive, and am debating chainring sizes. looks like the 30 might be good. now where's htat calculator.
BTW, to appease the moulton rivet-counters, i know its not the done thing, but the bike was a wreck saved from a skip last week. WheyHey!!! I caught the bloke with it in his wheelbarrow, just about to cast in into oblivion. Early Chrissie pressie for Andy. The bloke sees us on our Moultons, and sees the BikeRescue rigs outside, but it didn't dawn on him! Drives a Merc tho, so there you are!
Happy new year velovisionaries.
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| From: John Turvey (as above) on 01 January 2004 |
I have 3 cycles with three sets of gears - a Greenspeed trike with Mountain-Drive and 3by8, a Trice Micro trike with Speed-Drive, 2 ring front derailleur and 9 cog rear deraileur, and a TranSport (2-wheel load carrying recumbent) with Mountain-Drive and 3by7.
My experience is that the rear derailleur is the primary gear system - the other gears systems are used to select a range and the rear derailleur is used as much as possible until another range is required.
Changes involving all 3 gear mechs should be planned in advance and not left till the last second - it is too late by then! |
| From: John Turvey (as above) on 01 January 2004 |
| Can the Speed-Drive take a 30 tooth chainring? - on my Micro I replaced the smaller (40 tooth) chainring with a 34 toother - and I had difficulty getting that on - IF I had removed the Speed-Drive from the trike and put the ring on from the other side of the Speed-Drive it would have been easier, but even then I suspect that 32 teeth is the smallest you can go as the chainring bolts would interfere if a smaller chainwheel was used. |
| From: Ben - Kinetics ([email protected]) on 01 January 2004 |
The smallest standard chainring you can fit to a Speed Drive is 34t, but there's a 29t version which uses a custom sprocket which is part of the gear housing. On the Brompton, I generally suggest the Brompton with a 34t ring - this gives a good gear range, extended at both ends, and a very tidy geartrain. The Mountain Drive is better for people who need very low gears but no higher gears.
If you want to try playing around with ratios, I've written a gear calculator which can handle all the possibilities - get it at:
http://www.kinetics-online.co.uk/html/k_gear.html |
| From: Mikes245 ([email protected]) on 01 January 2004 |
According to the Schlumph website it is a 27 tooth chainring, not a 29t, that is available and is part of the speed-drive housing.
I really like Ben's gearing calculator which is well worth down-loading. |
| From: Ben - Kinetics ([email protected]) on 02 January 2004 |
| You're right, of course ;-) I was thinking of the High Speed Drive... |
| From: John Shackford ([email protected]) on 16 January 2004 |
Friday 16th Jan 2004. My new longer length Brompton arrived today. It has a new look about it as it is noticeably longer! Looking forward to the ride.
All the best,
John.
http://www.pbase.com/john28july
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| From: Sam Powrie ([email protected]) on 22 May 2004 |
Hi Velofolk from Adelaide, Australlia,
(and hi Ralf too) - I have just bought a Birdy-Black kit very cheaply. I wanted a folding bike with an adjustable stem and couldn't afford anything built up, When this became available I snapped it up. It just needs hubs, wheel building and a drive train. What is recommended? It probably won't see too many steep hills nor will it ever go much above 25-30kmh! I have a 56 tooth ring and a double crank in the shed. Will a straightforward 7 or 8 speed set up using a 56 ring and an 11-28 do the trick? This frame has a front derailleur mount but I need the hassle of playing with small wheels and a front d. like a hole in the head!
Thanks in advance for any advice,
Sam Powrie.
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