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New Brompton six-speed details

We spotted this at Eurobike - now details direct from Brompton. From the press release:

Intro

[These are]... the more significant product developments being introduced to the Brompton range from 1 January 2009 ... The product announcements ... come in addition to the improvements introduced to our bike range over the course of the past nine months – dual compound tyres, new polymer suspension blocks and improvements to brakes, cranks and to our gear-free hubs; in addition, a stiffened version of the new suspension block will be available from January for heavier riders, or those who prefer a firmer ride.

Brompton Wide Range Hub

The new configuration for 6-speed Bromptons will feature a wide-range hub of our design, manufactured by Sturmey Archer; the present 6-speed arrangement, employing a SRAM hub, will be discontinued from 1 January 2009. We believe that the Brompton Wide Range Hub [BWR], together with Brompton's derailleur system, sets a new standard in folding bike gearing systems. It offers:

- An evenly-stepped gear range (302%) that is comparable to the leading 8-speed hubs; but
- It uses only a single epicyclic gear train (instead of three), thereby maximising efficiency;
- At 0.94kg, it weighs almost half as much as other hub gears;
- It comes in the same small package as the current three-speed hub, allowing existing owners to upgrade easily; and
- It is typically-Brompton: robust and built to last... owners can expect the same reliability as with the classic three-speed hub.

We will be supplying a 16-tooth and a 13-tooth sprocket with the BWR which, with a 50-tooth chain wheel, will give the following distances of travel:

Gear 1: 33.0 gear inches (2.63 metres along the ground)
Gear 2: 40.5 gear inches (3.23 metres travel)
Gear 3: 51.5 gear inches (4.11 metres travel)
Gear 4: 63.5 gear inches (5.06 metres travel)
Gear 5: 81.0 gear inches (6.45 metres travel)
Gear 6: 99.5 gear inches (7.94 metres travel)

This represents a gear range (top gear/bottom gear) of 302%; by comparison, the current SRAM 6-speed arrangement offers a range of 215%. Like our existing 6-speed offering, however, the gearing may be raised or lowered by fitting a 54-tooth (+8%) or 44-tooth (-12%) chain wheel in place of the standard.


The technical details

- The BWR is an epicyclic geared hub with a 34-tooth sun pinion, 60 tooth annulus and four 12-tooth planet pinions;
- In addition to direct drive (1:1), it offers a high gear of 1.567 (+56.7%) and a low gear of 0.638 (-36.2%); for comparison, the Sturmey Archer hub employed on our 3-speed bikes offers 0.75, 1:1, 1.33 and the SRAM hub currently employed on 6-speed Bromptons offers 0.73, 1:1, 1.36;
- Percentage change for a gear step is 23% or 27%;
- Hub weight without sprockets is 0.94 kg;
- It utilises the same indicator as the current Sturmey Archer 3-speed;
- It employs Shimano-type sprocket splines, the same as on our current 2-speed.

*******************

Other news from the press release includes:

- Availability of a new standard saddle with hollow, cromoly rails


- Availability of a new metal-caged non-folding pedal


- Availability of a 'superlight' front wheel (only on new bikes) with double-butted spokes, a new hub and aluminium nipples. Weight saving 85 g.


- Luggage: "For January, we are: a. Launching an updated cloth pannier with a more modern design, featuring a comfortable and stowable shoulder strap and a practical 'courier bag' style flap closure; the general quality is also improved with better materials and finish; b. Offering our rain-proof cover free of charge with all our front luggage options.

- S-Type bars: "The S Type bar length is being increased in response to feedback from riders; extra length will make the ride more stable and allows the use of longer and more comfortable grips. By using special lightweight grips, the new longer bar (with grips) is actually even lighter than the weight of the current bar (with grips)."

Posted on 17 September 2008
 

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