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Autore Topic: Brompton: elaborazioni  (Letto 116825 volte)

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Offline occhio.nero

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Re:Brompton: elaborazioni
« Risposta #30 il: Ottobre 24, 2012, 07:29:14 pm »
i contributi successivi sono stati dirottati in

Brompton: cannotto sellino
http://www.bicipieghevoli.net/index.php?topic=3019.0

Federico
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Offline beaturbano

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Re:Brompton: elaborazioni
« Risposta #31 il: Novembre 08, 2012, 02:39:58 pm »
da qui: http://www.bikeforums.net/showthread.php/629587-Some-lightweight-tuned-folders

Brompton Singlespeed, 7.29kg
Zipp 300 crankset
 Custom wheelset with titanium spokes
 KCNC seatpost
 KCNC brake
 Wellgo ti spindle pedals
 Mortop carbon handlebar
 I-link cables

« Ultima modifica: Aprile 28, 2017, 01:25:00 pm by occhio.nero »
citizen cyclist [utente leggero della strada]
non possiamo pretendere di risolvere i problemi pensando allo stesso modo di quando li abbiamo creati - albert einstein ||| è una questione di qualità - cccp

Offline giannib

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Re:Brompton: elaborazioni
« Risposta #32 il: Novembre 08, 2012, 03:21:02 pm »
Azz!
Ma al posto dei copertoni c'hanno messo due elastici!
brompton m2l-x 06/2011
mandrin 20"dallacinaconfurore" 05/2012

Offline alesblues

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Re:Brompton: elaborazioni
« Risposta #33 il: Novembre 08, 2012, 03:31:11 pm »
A dir poco fantastica!!! Mi piacerebbe sapere quanti denti ha la corona!! Ora sto scrivendo dal dell' ma appena sono a casa do' un occhiata!( ora che ho messo i parafanghi per l'inverno alla mia singlespeed...mi vien voglia di torglerle a vedere questa foto =) )
Brompton M3L black

Offline Fero

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Re:Brompton: elaborazioni
« Risposta #34 il: Novembre 08, 2012, 03:56:03 pm »
Sbaglio o manca un freno?
Dahon MU P7 - sella Brooks Flyer - Pedali MKS FD-7 - Big Apple 20x2.00

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Re:Brompton: elaborazioni
« Risposta #35 il: Novembre 08, 2012, 11:11:06 pm »
Manca un freno in effetti... Bella, ma mi ricorda un po' quella striscia di Garfield (il gatto) dove per riuscire a perdere peso voleva amputarsi qualche arto.  ;D
Mario
"La città è fatta per le persone, non per scatole di metallo". (Ayfer Baykal, assessore all'ambiente, comune di Copenhagen)
Brompton M6L blu cobalto, Strida Evo Silver

Offline beaturbano

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Re:Brompton: elaborazioni
« Risposta #36 il: Novembre 27, 2012, 01:32:48 pm »
un articolo vecchio, 2005, ma può essere uno spunto
http://www.atob.org.uk/folding-bikes/superlight-brompton/
Citazione
Superlight Brompton



Big strong men sometimes ask us why we put such an emphasis on reducing the weight of folding bikes. If you have to ask the question, you really don’t need to know the answer.Taking weight out of a bicycle has little effect on performance, but a great deal of effect on the ease with which it can be carried.

Many people would be willing to use a folding bike but cannot lift a 14kg (33lb) weight, let alone haul it upstairs or run for a train with it. Get the weight down to a reasonable 12kg, and most people can deal with it. At 10kg, we’re up to, perhaps, 90% of the adult population, and if weight can be pared down to less than 8kg (already feasible, but expensive), the bike becomes practical for almost anyone to carry.Weight reduction is a truly emancipating technology, bringing folding bikes to those previously excluded.You might argue that they still need to be pretty wealthy, but this is really only a state of mind problem. If a high-end folding bike eliminates the need for a second or third family car, a purchase price of £1,000 or so can represent great value for money.This technology is getting less expensive, but don’t expect fanciful titanium creations to ever be cheap.

Design Challenge

The challenge for designers is to get as close as possible to the 8kg weight goal without seriously compromising the strength and rideability of the machine. Current leader is Dahon, whose Helios SL weighed a genuine 8.65kg (19lb) when we tried it in August 2004.The Helios SL is a delightful machine, but it has 20-inch wheels, so it makes quite a big folded package. It also comes with beautiful, but frail Rolf wheels, and no mudguards, so it’s not really a daily commuter machine.

The Brompton is a classic commuter bike, but it’s heavy. In A to B 1, we built a lightweight Brompton weighing 10.9kg. Considering that the Brompton weighed 12kg at the time, this was, with hindsight, quite a good result for a broadly conventional three- speed bike.The following year we were at it again, fitting a 1950s alloy shell to the hub (saving a whacking 120g), fewer, slimmer spokes, a carbon fibre seat pillar, Birdy suspension polymer and a few other bits, hauling the weight down to 10.4kg (22.9lb).


Some lightweight parts are strikingly attractive in their own right.This is the TA AXIX Light bottom bracket
For the next few years, the bike clocked up several thousand miles. Most of the parts lasted well, the only weak spots being the aluminium rear roller securing bolts (they should have been titanium), and the carbon fibre seat pillar, which ate through two frame bushes and ended up dangerously worn itself. In the meantime, of course, the industry had been busy with its own weight reduction programme, and although some of the new stronger Brompton parts (such as the handlebars) were heavier, most were lighter…The company was gradually catching up.

In April 2005, Brompton launched the 9.7kg S2L-X and left our lightweight machine looking a bit sad. Could we do better using the S2L’s new technology – principally a two-speed derailleur hub and titanium frame parts?

A to B Bites Back

Eight years after putting together our original machine (the day of the Princess of Wales’ funeral, for those interested in historical minutia), we’ve built a new machine that’s both lighter and stronger.This isn’t a stripped-down special – our bike has mudguards and all the usual equipment you would expect to find on a Brompton S2L-X, but with the ‘traditional’ M-type Brompton handlebars, because that’s the way we like ‘em. This older design has a shorter stem, saving 60g, but a more complicated handlebar, adding 110g, giving a net weight increase of 50g. Drat and double drat.The taller handlebars also make it impossible to fit the S-type’s shorter Jagwire cables, adding another 50g, so before we’ve even started, our bike weighs 100g more than Brompton’s super-light model.

If our bike is effectively a standard machine, how is the weight taken off? The trick is to work methodically through the machine, replacing steel parts with lighter alternatives. For safety-related bits, this generally means titanium, which is as strong as steel, but about 40% lighter. Less critical things can be replaced with aluminium – 65% lighter than steel, cheaper than titanium (not much in these specialist areas), but weaker, so it needs to be treated with care. Cosmetic things can be made in plastic, or omitted altogether, but ‘easy’ weight savings of this kind will be hard to achieve if the development engineers have already done a good job.


Tranz-X clamp - note the reversed nut and pin preventing the clamp from rotating
As in 1997, we’ve laid out a table indicating the cost-effectiveness of each change. Today, most of these lightweight parts are easily obtainable from Brompton dealers and other specialist outlets, so they’re cheaper than they were eight years ago. At anything up to £1 per gram saved, it’s still an expensive business, but to paraphrase the RSPCA, titanium is for life, and not just for Christmas. Once you’ve raided the piggy bank and fitted the bits, they can be transferred from bike to bike until your knees give out, and then passed down as family heirlooms.

If you’re in the market for the bigger, more expensive chunks of titanium, it’s generally cheaper to go for broke and buy one of Brompton’s own lightweight machines. As fitting is so complex, the two-speed derailleur probably comes into this category too. Even if you’re hoping to upgrade a near-new six-speed bike, it will be easier (and cheaper) to sell the old one and buy a new two-speed.

Top of the ‘worth doing’ list are things like pedals, handlebar grips and reflectors, lighter versions of which can be found quite cheaply.We chose to leave the wheel reflectors off altogether, but you may feel it’s not worth compromising safety for the sake of a few grams. Other parts, like alloy spoke nipples and lighter 14-gauge rear spokes, are cheap, but fitting can involve a great deal of labour, and the long-term strength of the bike will be slightly compromised.The S-type’s Stelvio Light tyres and tubes come into this category too – they are lighter, but more vulnerable to punctures.

Some standard parts are hard to beat – for example, there’s very little to choose between 3/32” chains.We spent £26 and saved a paltry 16g by fitting a KMC X9 Gold chain which is, believe it or not, gold plated. Still, it goes very nicely with the exposed brazes on the Raw Lacquer frame. It’s difficult to beat the weight of the standard Brompton saddle too. On our original bike, we fitted a Terry Race Vanadium saddle weighing 227g.We were able to reuse it, which is fortunate, because it no longer seems to be available.The best we could find today was the Fizik Vitesse Twintech ladies saddle, weighing a claimed 230g and costing £60.This sort of upgrade could never be cost-effective, but saddles are a personal thing, and in the final analysis, a lightweight bike is a fashion statement. Like any other fashion statement it wouldn’t be complete without a few decadent touches.


Anything we’ve missed? The cables and brakes could be lighter, but it’s unlikely the weight and complication would be worthwhile. Otherwise, apart from odd nuts and bolts, we’ll probably have to wait for Brompton to introduce a titanium mainframe, which would save perhaps another kilogram.

On the Road

If you’re worried about the lack of gears, don’t be. Under most conditions, the two-speed derailleur performs much like a conventional three-speed Brompton.The bottom gear of 56″ can tackle hills of up to 12.5% (1 : 8 ) with a suitably enthusiastic rider, and the top gear of 74″ is adequate for most urban situations. If you can live with a slightly high pedal cadence, it’s OK on the open road too.As we’ve suggested elsewhere, it may be possible to change the 16-tooth sprocket for a 17-tooth (a 53″ gear) without any other work, and with a bit of titanium-bashing, an 18-tooth can be squeezed in, giving a bottom gear of 50″.That’s almost as low as first on the old three-speed, but a bit of a jump down from top gear, so we’ve left the gearing unchanged and will see how we get on.

In theory, the lightweight parts make next to no difference in terms of speed, but the lighter rotating bits improve acceleration, and they certainly make the bike feel livelier and sharper to ride.We can only say that our lightweight bike seems to accelerate well, and it’s a delight to ride. If it feels good, that’s all that really matters…

Carrying the bike is obviously a lot easier. It’s difficult to visualise how light it is, but try taking the wheels off a Brompton L3 and lifting it…

What does the bike actually weigh? Er, um, a bit of a dispute here. All the parts, old and new, passed over our traditional scales, so we’re quite certain that our bike weighs 2.5kg less than a standard M3L, or L3 as it used to be called. But according to our electronic scales, the finished bike weighs 9.5kg, which is two or three hundred grams more than we were expecting. Drat and double drat!

And how much did it cost? This is another tricky question, because the costs depend on how you do it.To upgrade an elderly Brompton would cost around £800, excluding the two-speed kit, which is not really cost-effective as an upgrade. If buying a new Brompton, the cheapest option is to start with the M2L-X, which comes with most of the Brompton lightweight kit for £873. Adding the Stelvio tyres and the A to B bits and pieces would cost another £250 or so, and bring the weight down to 9.2kg or 9.5kg, depending whose scales you believe.

ENGINEERING NOTES

Not all these parts can be bought off the shelf. The locknut on the Tranz-x seatpost clamp has been turned down to fit inside the Brompton frame lug, with two pegs fitted at the other end to stop the clamp assembly rotating, effectively mimicking the action of the Brompton clamp.The Birdy yellow suspension polymer is a useful upgrade, especially for lighter riders, but needs some shaping to fit – ours is also drilled like an Emmenthal cheese to give a softer ride. We used an aluminium bolt in the suspension, but this should really be titanium.The axle on the AXIX titanium bottom bracket has marginally less bias towards the chainring than the Brompton’s FAG axle. We fitted a 1mm shim, but tolerances vary – we probably didn’t need to. Two home-engineered bits we didn’t reuse this time were the alloy three-speed cable-guide nut (not needed) and the steering head alloy expander nut, which is now a standard fitting.
citizen cyclist [utente leggero della strada]
non possiamo pretendere di risolvere i problemi pensando allo stesso modo di quando li abbiamo creati - albert einstein ||| è una questione di qualità - cccp

Offline beaturbano

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Re:Brompton: elaborazioni
« Risposta #37 il: Novembre 27, 2012, 01:42:09 pm »
dello stesso periodo, sulla stessa rivista, sempre in tema di elaborazioni.
http://www.atob.org.uk/folding-bikes/the-sp-brompton/

Citazione

The SP Brompton
Hand-fettled derivatives of the popular folders
Produce any interesting machine and someone will want to customise it. Engineer Steve Parry has been producing custom folding bikes to order for over a decade – concentrating on the Brompton in recent years.

In practice, you can order a Brompton from Mr Parry with just about any choice of parts and accessories, from the single-speed on this page to the all- singing, all-dancing 14-speed overleaf.

The basic single speed weighs 9.7kg (21.3lb) – around two kilograms lighter than a standard L3. This weight saving is achieved largely with high-tech materials: titanium/carbon fibre telescopic seat pillar, carbon fibre forks, stem and cranks, with MKS demountable pedals.

The single-speed rear hub is a Shimano freehub with all but the 11-tooth sprocket removed to save weight. Unusually, the bike is fitted with slightly oversize Birdy 18-inch wheels and Schwalbe Stelvio tyres. Price is £1,200 – broadly the same as the equivalent Bike Friday, Airnimal or Bridgestone Moulton.

In contrast, the Rohloff version features every conceivable accessory and weighs 13.9kg (30.5lb).The seat pillar is the same, but the lightweight saddle has been replaced with a Brookes leather item, and the cranks are Shimano 105.The handlebar stem is carbon fibre again, but this time with integral suspension. Brakes are superb – Hope hydraulic discs front and rear, giving a best stop of around 0.75G before lifting the rear wheel.The Brompton rear rollers are replaced with SP narrow discs and the rear suspension is fitted with a hook to prevent involuntary folding. Finally, there’s that hub… Steve fabricates his own rear frames to accommodate the much wider 14-speed Rohloff, but the folded size of the bike is little changed, and the system works well. Price? About £2,000 depending on the exact spec.That’s about the same as the Birdy Grey or Airnimal Ultima.


   

 
citizen cyclist [utente leggero della strada]
non possiamo pretendere di risolvere i problemi pensando allo stesso modo di quando li abbiamo creati - albert einstein ||| è una questione di qualità - cccp

Offline occhio.nero

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Re:Brompton: elaborazioni
« Risposta #38 il: Novembre 28, 2012, 09:33:01 am »
le fascette intorno all'ammortizzatore servono a regolarne la rigidezza?
interessante!
Federico
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Offline beaturbano

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Re:Brompton: elaborazioni
« Risposta #39 il: Novembre 28, 2012, 12:02:55 pm »
le fascette si, evitano che si comprima troppo. l'uncino è un sistema di bloccaggio artigianale del telaietto posteriore, quando questo non aveva alcun fermo.
citizen cyclist [utente leggero della strada]
non possiamo pretendere di risolvere i problemi pensando allo stesso modo di quando li abbiamo creati - albert einstein ||| è una questione di qualità - cccp

Offline Sbrindola

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Re:Brompton: elaborazioni
« Risposta #40 il: Novembre 28, 2012, 12:24:25 pm »
quindi se telefono a Steve e lo pago il giusto mi fa una Brompton come voglio io? .... tipo con dei comandi cambio meno orripilanti?

molto particolare la soluzione di ammortizzazione anteriore: non si ammortizza la forcella ma il piantone sterzo e quindi il manubrio.
Alla fine 2000£ per una Brompton con Rolhoff freni a disco e biammortizzata non sono poi così esagerati.
« Ultima modifica: Novembre 28, 2012, 12:27:25 pm by Sbrindola »

Offline Hopton

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Re:Brompton: elaborazioni
« Risposta #41 il: Novembre 28, 2012, 01:44:03 pm »
Riporto da PM:

Caro Mario/Hopton,
desidero chiederti un piacere in nome della nostra amicizia, se per te non è di troppo disturbo. Ultimamente sono molto stressato per situazioni personali, lavorative e non. Questo inevitabilmente ha incominciato a riflettersi sul mio grado di lucidità, per cui alle volte scopro (in ritardo) di avere scritto per esempio una cosa completamente diversa sul forum rispetto a quella che intendevo.
La mia richiesta è quindi la seguente: se dovessi notare che ho scritto delle cose palesemente senza senso e/o opposte a quanto io penso, saresti così gentile di correggerle per me? Altrimenti corro il rischio di non notarle subito, o di non notarle affatto, e potrebbero sorgere spiacevoli malintesi.
Ti ringrazio per la disponilità, un saluto.
Raffaele/Sbrindola


Caro Raffaele, ma figurati, ci mancherebbe che per così poco io non debba aiutare un amico in (temporanea) situazione di difficoltà. Anzi guarda, comincio subito:

quindi se telefono a Steve e lo pago il giusto mi fa una Brompton come voglio io? .... tipo con dei comandi cambio meno orripilanti ancora più entusiasmanti di quelli di serie?

Come dice sempre Crozza/Marchionne, non occorre che mi si ringrazi.   8)

Mario
"La città è fatta per le persone, non per scatole di metallo". (Ayfer Baykal, assessore all'ambiente, comune di Copenhagen)
Brompton M6L blu cobalto, Strida Evo Silver

Offline Sbrindola

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Re:Brompton: elaborazioni
« Risposta #42 il: Novembre 28, 2012, 01:52:40 pm »
 :D :D mi hai fatto scassare dal ridere.... ed il bello è che mentre leggevo il pm mi stavo bevendo tutto!
Chiedo venia per non avere dato sfoggio della mia ars diplomatica ..... ma quella specie di acceleratori per tagliaerba  ;D sono la cosa che meno digerisco di tutta la bici.

Per farmi perdonare ti dico però che in questi giorni sono colto da ivoxite acuta..... ma la prognosi è ancora incerta.
« Ultima modifica: Novembre 28, 2012, 02:01:12 pm by Sbrindola »

Offline ivox

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Re:Brompton: elaborazioni
« Risposta #43 il: Novembre 28, 2012, 03:20:01 pm »
........
Per farmi perdonare ti dico però che in questi giorni sono colto da ivoxite acuta ..... ma la prognosi è ancora incerta.

Purtroppo per te sappi che non c'è cura, la malattia farà il suo corso e ti ritroverai con giannite cronica in men che non si dica :-)

P.S. per tua informazione sappi che: chi di ingiuria ferisce di ingiuria perisce! sai quello che ti aspetta caro :-)

i.
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Re:Brompton: elaborazioni
« Risposta #44 il: Novembre 28, 2012, 03:21:50 pm »
@ mario/hopton: il fake pm è una delle cosa più divertenti che ho letto su questo forum :-)
Ivo - Brompton S8L Raw Lacquer - Brompton S2E-X Orange (in ritardo di consegna)

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