Climb Every Mountain

Regarding Brompton gears (A to B 42), those who own the 6-speed machine would no doubt do well to experiment with sprocket changes, but owners of older machines (which I believe cannot be economically upgraded) don’t have this option. I think that the principal objection to multiple chainrings is that, so far as I am aware, there is no ‘mainstream’ conversion available. Inevitably, they do add complication but I liked the minimalist approach of a Brompton rider I encountered on the C2C who shifted his chain with a hand-held hook, apparently fashioned from a wire coathanger. My own design uses a Shimano braze- on mech and thumb shifter and is mainly aimed at filling the gaps in the standard Sturmey 5-speed range. I agree a wider range would be helpful but, pending the availability of better things, it seems we have to choose – never mind the width, feel the closeness!

I agree with what you say about possible chain-related problems; you might have added that the cage of the front mech has to be open at the bottom so as to allow the bike to fold. It occurs to me to add that a conversion provides an excuse to get rid of the rather down market standard chainset and benefit from shorter cranks.

George Winspur
Rochester, Kent

We’re still not keen. A multiple chainring adds more weight than a sprocket change and you have to fold the bike with care, particularly when the chain gets a bit old and slack – we’ve seen broken tensioner arms caused by misaligned, slack chains. For older Bromptons, we’d recommend either fitting the excellent Mountain or Speed Drive conversion (not cheap, but engineered for life), or trading the bike in for a new 6-speed with alternative sprockets. The secondhand value of grotty old Bromptons makes this very worthwhile. (Eds)

Extra Gears = More Speed?

I found the test of the Lafree Comfort ST interesting, because I’ve been using a SRAM 5- speed hub on my Lafree Lite since fitting it early this year. After nearly a thousand miles, I can confirm that the change does improve somewhat with time as Giant indicated, but it never gets anywhere near the slickness of the Nexus three speed. However, it soon becomes instinctive to stop pedalling and allow that moment extra for the ‘click’ from the hub. Given the hill climbing ability, it doesn’t matter if one involuntarily stops at a change down from second to first, since even a 1 in 7 hill start with a 14 kilogram trailer attached is easy with moderate assistance.

I’ve also tried both 18- and 17-tooth rear sprockets in place of the standard SRAM 19- tooth. Any hypothetical illegality due to the use of the 18-tooth is virtually undetectable, given that the power begins to phase out at higher crank speed. However, the legal position isn’t really the issue, particularly with a 17-tooth – it’s more the lack of available power. In fifth with the 17-tooth, the least incline or moderate headwind forces a premature change down to fourth, leaving one travelling slower than if the original 19-tooth was in use, so after extensive testing with both 18- and 17-tooth, I concluded the standard arrangement was best. Also, as ever with NiMh or Nicd battery power, what’s viable when the battery is fully charged can soon prove not to be so in the latter half of the charge usage as the voltage reduces.

Tony Flecchia
Croydon

One problem with the Lafree for enthusiastic cyclists is the rather limited top gear ratio of around 80-inches – if a higher gear is used, the bike will either run illegally fast or, as Tony found, give up on hills. A solution might be to fit the bike with a 5-speed hub and ultra-high gearing to give four power-assisted ratios, and a sort of overdrive top, for use with the motor turned off when the going is easy and you want to pedal at higher speed. (Eds)

Familiar Semi-recumbent

At the CTC York rally I had a brief try on a pedal-assisted semi- recumbent electric bike from an outfit called Urban Mover. It was twistgrip operated, but power only came on when pedalling. At around £850, I thought it was very competitive, and streets ahead of the Lafree in appearance.

But for ‘worried . mum of  Surrey’  (Letters, A to B 42), don’t   think of buying  your 14 year old an electric bike. Offer him a decent sports tourer with a reasonable rack/pannier/saddlebag arrangement. He’ll be fitter, stronger and more independent… never did me any harm anyway.

Jim Whitfield
Beverley,Yorkshire

Ah, those were the days. Incidentally, despite having a bus season ticket, editor David Henshaw cycled six miles each way to school for several years (and occasionally home to lunch), all on a single-speed bike, dreaming all the while of owning a Sturmey 3-speed (this is all true). However, that was in flat seaside terrain.We should have made it clear that the route described in the letter crosses the South Downs between Albury and Cranleigh – a climb of at least 500 feet each way.Throw in the stress of dealing with rampaging four-wheel-drives, and it’s definitely an electric bike job, unless the young man is really keen.

The Urban Glider UM30 is a fascinating machine, very similar to the unassisted Giant EZB semi-recumbent, but with NiMH power and a competitive claimed weight of 26kg. If you want one you’ll have to hurry, as Giant is taking action to get it removed from sale due to copyright infringements, which is hardly surprising. (Eds)

Which Tyre Size?

I was interested in Nils Hoglund’s letter in A to B 42. I have no personal experience of folding bikes but I am hoping to buy one in the near future, and have been carefully scrutinising the reviews in A to B to select my model. Despite the acclaim given to the Brompton, I am rather put off by what appear – to someone used to a conventional bike – to be its very small wheels, which look like a lot of hard work, and I have been considering the Dahon Helios as an alternative, simply because of the 20-inch wheel size.

I would welcome some information and discussion on this point, and contributions from other readers’ experiences. Are 16-inch wheels really too tiring for anything more than short journeys nipping around town?

Peter Bolwell
Hastings, East Sussex

Although we’re evangelists for small wheels, we can’t deny that rolling resistance rises as wheel diameter decreases, but with modern tyres the effect is quite small.The best 20-inch (406mm) bikes are almost indistinguishable from big wheelers – in fact, the reduced mass and lower wind resistance probably makes them faster on good road surfaces.With the smaller 347mm tyre fitted to the Brompton, the performance gap is beginning to widen, but we’ve ridden 100 miles (once!), and many 50 mile days without exhaustion. If you can find a comfortable wind-cheating position, the tyre size becomes relatively unimportant. Sub-347mm sizes really are limited to short distances, although oddly our rolling resistance figures don’t seem to bear this out. Perhaps the extra fatigue results from the choppier less forgiving ride, rather than rolling resistance alone? (Eds)

Fluctuating Thingies

It is well known that a fluctuating magnetic field will produce a fluctuating electric current in a conductor and that conversely a fluctuating electric current will produce a fluctuating magnetic field. Can someone explain why an electric bike is designed to be run by pedal power on a level road and power-assisted to climb a hill but not arranged to charge the battery and at the same time provide braking assistance when travelling downhill.

Alex Massie
Chirnside, Berwickshire

Professor Pivot Replies: ‘Regenerative’ braking is something of a Holy Grail for cyclists and by far the most common question about electric bikes. My negative replies are always met with rather crestfallen, gloomy looks! Firstly, electrical braking can be and very occasionally is built into electric bikes, but it’s hardly worthwhile for a number of reasons. As a general rule, motors turn much faster than road wheels, so a fair amount of energy is required simply to turn the gears and motor. Consequently, most are fitted with a one-way clutch to disengage the motor when the rider is coasting or pedalling without assistance. For the motor to be available as a brake, it would have to be permanently engaged, with all the energy losses that would entail.

A few sophisticated wheel-speed AC motors have been produced, eliminating the frictional loss problem (and, incidentally, most of the noise). As AC motors are inherently well suited to providing regenerative braking, these are usually fitted with such a system. However, when you take into account chemical, electrical and frictional losses in the battery, controls, wiring, motor, drive system and tyres, plus vehicle wind resistance, there may be very little power left to store. A few years ago I experimented with a Zappy scooter, and found that the descent was regenerating a mere 20% of the energy consumed on the climb! I suspect that suitable AC motors will eventually become commonplace, but the impetus for regenerative braking will have more to do with reducing stress on the conventional braking system than improved power-assist efficiency.

Whacky Fringe

We all know that the Association of British Drivers is a small group of right-wing nutters with a tenuous grasp of reality. However, they have garnered a huge amount of media attention, out of all proportion to their real significance.

So, let’s set up the Association of British Cyclists (ABC) whose job will be to pronounce similarly whacky views, albeit from a two-wheel perspective.The ABD wants to ban speed cameras (except for those few in ‘appropriate places’ of course) – the ABC will counter with a demand for cameras placed every 100 metres on every stretch of road, everywhere.The ABD wants the motorway speed limit raised; the ABC would like to see it cut to 40mph, with the inside lane reserved for bikes. And so it goes on.

This way, the ABC can be dismissed as a radical fringe, leaving the CTC and LCC looking terribly moderate and responsible.Well, it’s a thought isn’t it?

Peter Henshaw
Sherborne, Dorset

Trundling and Musing

While trundling home in a downpour recently, I managed to enter a higher mental plane by contemplating on the design of a folding tandem. I’ve thought for a long time that there is an empty niche for a Brompton- or Birdy-esque tandem, folding to public transport size in less than a minute without disassembly.

The problem has always been, what to do with the timing chain? Folding the rear wheel under interferes with the chain. All obvious solutions involve removal and filth. My mind drifted back to articles in recent A to B’s and the piece in issue 39, on shaft drives. I think that this is the answer.A shaft drive connecting front and rear cranks, with a chain final drive.

The bike would fold in the same places as a Brompton, have 349mm wheels, suspension front and rear, drum brakes and an 8-speed hub.The solution seems so obvious that I think that I must have missed something. Nothing in cycling design is really new, so has this been done before?

Davy Nichol
Symington, Ayrshire

It can be made to work – see the folding shaft-drive on the Di Blasi trike, page 36. (Eds)

Peak Oil

Tony Raven (Letters, A to B 42) was right to be wary of any pundit using the phrase ‘running out of oil’. But those in the ‘70s with access to the best data were predicting that output would reach an absolute maximum around the year 2000 and then go into permanent decline. In the event, the year-on-year increase in global demand was substantially curtailed following the oil crises, but after a short-lived decline, consumption resumed its upward trajectory. Contrary to Tony’s impression, those leading the wake-up call on Peak Oil are primarily retired geologists. See the Association for the Study of Peak Oil (www.peakoil.net).

Bill Jamieson
Stow, Borders

Clip Your Own

You might be interested in visiting www.bikesmithdesign.com/peters_pedals/ which describes some removable SPD pedals I made using MKS Promenade pedals and a cleat from another pedal.The pictures are on the Minnesota Human Powered Vehicles Association website for reasons that are too complicated to go into! I have replaced my folding toe clips with this new solution. Much better when clipped in and much more convenient when using ordinary shoes.

Peter Amey
Bradford on Avon,Wiltshire

The MKS Promenade demountable pedals (see Helios SL) are a useful folding bike accessory, but cost in the region of £60 a pair. Any good bike shop should be able to order them, although Norman Fay Cycles is the only stockist we’ve yet come across – tel: 0191 456 1055. (Eds)

Electrifying

I have two 5-speed Bromptons both with front and rear carriers etc, the older with two gear levers, the younger (inherited from my late son) with one. I keep one in southwest Scotland where it is moderately hilly, and being of free TV licence age I would appreciate some power-assistance on the hills! The nearest shop and pub are five miles return away along the coast road, but I would be tempted to go further with a little help.

As an avid A to B reader,I have sensed that you are coming round to the idea of folding electric bikes? Presumably a brake upgrade would also be recommended?

B.E.Sayers
Wolverhampton

We’d recommend contacting either Kinetics in Glasgow (tel: 0141 942 2552) or E-go (tel: 07974 723996). Both have experience in fitting small motors into small wheels. (Eds)

The Final Word

In which you get your say… briefly

Excellent – more of the same for twelve months please! Genuinely useful, interesting and entertaining . Super – don’t change it . Vastly overpriced . Excellent value . Fantastic mag, monthly please, pretty please! PS Less electric bikes, more folders . Thanks for the article on brakes . More about trips and maintenance of folders, a bit less on electric bikes Just the right balance – I read every item . Could you do folding tandems? Too many electric bikes! Please include more articles from Japan and Asia . Rob Cope’s rail guide is sadly missed . Different but interesting . I like the politics related to all forms of transport Required reading on the way to the Le Mans 24 hour race . Rekindles my enthusiasm amongst all the gloom . I love the magazine, but my wife hates being ignored while I’m reading it Creates domestic dramas as we both try to grab it . Best thing since our homemade bread A voice of sanity, and fun besides! My bi-monthly dose of sanity – keep pedalling it!