Brompton Bicycle is a bicycle manufacturer based in Kew Bridge, London, in the United Kingdom. It is notable for its folding bicycle and being the last transport manufacturer of any kind based in the capital city. It is the largest volume bicycle manufacturer in Britain, the other being Pashley Cycles. Approximately 22,000 bicycles are produced by the company each year of which 70 percent are exported. The company was awarded the The Queen's Award for Export in 1995.
The Brompton folding bicycle and accessories are the company's core product, noted for its self-supporting compact size when stored. All available models of the folding bicycle are based on the same hinged bicycle frame and 16 inch (349 mm) wheel size. Components are added, removed, or replaced by titanium parts to form the variations. The modular design has remained fundamentally unchanged since the original patent was filed by Andrew Ritchie in 1979, with small details being refined by continual improvement. Ritchie was awarded the 2009 Prince Philip Designers Prize for work on the bicycle. In reviews of folding bicycles, the Brompton is often the winner.
Folding bicycle
All Brompton folding bicycle models share the same curved frame, consisting of a hinged main tube, pivoting rear triangle, and hinged handle-bar stem. The steel sections use brazing to join the steel (instead of welding). Wheels are 349 mm rim size, carrying tyres with 16" tread diameter. The handlebars and some periphery components are aluminium.
A Brompton bicycle uses over 1,200 individual pieces, eighty-percent of which are manufactured purely for the Brompton design.
The fold
The "Brompton fold" is unique to Ritchie's design, allowing the bicycle to shrink both vertically and lengthwise during folding, but keeping all of the parts attached to one another. The elements which allow the design to work are:
- Pivoting rear triangle, allowing the length to be shortened, whilst keeping the bicycle chain in the same alignment, there is a slight curve in the main frame to allow the wheel to swing under.
- Chain tensioner arm capable of swinging through a wide arc, in order to absorb the full length of the chain during folding without the chain coming loose. The chain ends up looped back on itself.
- Angled handle-bar stem, on a bicycle the handle bars are at right-angles to the rest of the bicycle. Having the hinge placed at 45-degrees to the rest of the bicycle means that the handle-bars swing through ninety degrees and lay parallel with the wheels when folded
- Main frame hinge, the fold in the centre of the bicycle allows the front wheel to be swung around and placed against the rear-wheel. As the front wheel also rotates freely for steering purposes, the front wheel remains pointing forwards even when folded.
- Seat post combining the function of variable height adjustment and locking. When lowered during folding, the base of the post locks against the lower stop disc preventing the folded package from swinging open
The final folded package is 565×545×250 millimetres (22.2×21.5×9.8 in) and weighs between 9–12.5 kg (20–28 lb) depending on the configuration. Folding takes 10–20 seconds meaning that normally the bicycle can be pushed or cycled until the very last minute and only folded before stepping onto the train or entering a building.
Models
Models are named using a code containing two letters either side of a number to describe the handle bar type, number of gears and factory attached fixtures. An optional suffix is appended to show the inclusion of titanium upgrades. As an example, the model code of "M3R" refers to classic "M" handle bars, "3" gear speeds using an internal hub and an "R" for having a rear rack. The same model, but making use of titanium where possible would be "M3R-X".
- ^ a b Until 2007, all Brompton bicycles had "M"-style handle bars, with the fixtures being "C" (no mudguards), "L" (mudguards) or "T" (rear rack and dynamo lighting). These roughly map to the present "E", "L" and "R" models. Only "3" or "5" (later "6") gears were offered, and this was written after the type. A late 1990s "T5" would be similar to a present "M6R", while a "C3" would be close to the present "M3E". The old marketing terms were C ompanion , L ightweight and T ouring .
Factory additions
"R" models may have the wheels on the corners of the rack replaced with larger eazy wheels , to aid pushing when folded. All models can choose to have no lights , lighting powered from battery , bottle shaped tyre dynamo or front wheel hub dynamo . Seat posts can be swapped between standard length, extended or telescopic for tall riders (each with a titanium equivalent). Bicycles are offered in black or red matt colours as standard, with the optional selection of further colours, or transparent raw lacquer coating. Titanium areas are left unpainted, in their natural titanium colour. The standard Brompton saddle can be substituted by a Brooks B17 Special leather saddle ladies' or men's versions. Non-titanium models have braze-on fittings for holding the supplied Zefal HP compact high-pressure bicycle pump.
All models may have the front luggage block fitted to carry cargo, this is fitted to the main frame (rather than to the forks or handle bars) to avoid interference with the steering. The hub dynamo option uses a special narrow-width SON XS hub dynamo fitted at the centre the front-wheel and manufactured by Schmidt Maschinenbau.
A full superlight variant uses titanium to save weight, combined with lighter wheel components. The option replaces the rear triangle, front forks, seat post and other smaller parts. The main frame structure remains steel. This upgrade represents the largest cost increase of any upgrade, and reduces some variants to below ten kilograms in weight.
Tyres can be swapped at any point between Brompton yellow , kevlar based Brompton green , heavier Schwalbe Marathon or very narrow Schwalbe Stelvio .
- ^ Whilst no longer factory fitted, Brompton bicycles originally used Raleigh Record tyres and continued to do so on the lower end model until the 2000s.
Accessories
A small saddle bag can be fitted behind the saddle for the Brompton cover and any tools or spares.
When fitted with a front luggage block, a choice of folding basket , large touring pannier or two variants of bicycle- messenger style flip-over bag can be attached to the bicycle. These bags internally share a common design of lugguage frame , which can also be used separately.
History
The core design has proved to be very close to the optimum; the folded package being restricted roughly to the size of the wheels used, plus a small overhead. As such, design improvements have generally been subtle and introduced in such a manner as that they can be retrofitted on earlier production models of the bicycle.
Customisation
Further modifications are provided by some Brompton dealers or skilled individuals, the most prominent examples being:
Replacements
Brompton owners and designers with suitable engineering expertise regularly try to improve the design, although there is limited scope to do so as any additions attached are likely to compromise either the final folded size, carried weight or folding action.
- SP . In the United Kingdom, builder Steve Parry specialises in producing a bicycle called the SP , based on Brompton components combined with a seven-speed derailleur, V-brakes, carbon fibre seat post and a suspension handlebar system.
- "Brekki" recumbent upgrade kit. A collection of add-ons offered by a German bicycle to convert a basic Brompton in a recumbent bicycle design and the cost of a larger folded package and heavier weight.
- Ultimate Folding Bicycle. An on-going development involving wholesale replacement of virtually all original Brompton frame components with titanium or lightweight versions. The result is a sub 8-kilogram bicycle with a Brompton fold and luggage compatibility.
- "Nano Brompton" - an upgrade to convert a basic Brompton to an electric bike by adding a powerful electric front hub motor to the Brompton, the motor adds some 2 kg to the overall bikes weight.
- "Brompton E-Freedom" - an upgrade to convert a basic Brompton to an electric bike by adding a powerful electric front hub motor to the Brompton, with nano-technology batteries, the wh
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