We’ve had quite a few emails over recent weeks, and the greatest interest and debate seems to be on Tommy’s machine – and how much a disadvantage it would actually have been when compared to bikes available to today’s riders.
Bruce Dance had this to say:
“Whilst I agree Tommy’s bike was rather different from modern ones, I feel that this idea is somewhat overplayed on your website.A 531 frame and fork back then (as today) would weigh around 6lbs. Although I do not know that they were used, light alloy parts including wheel rims, brakes, handlebars etc were certainly available.
The selection of a hub gear (and doubtless other components) would have been taken not with ultimate speed and efficiency in mind necessarily so much as a compromise with reliability as a dominant factor. Politics/sponsorship aside (Raleigh owned SA and in fact refused to market derailleur gears until the 1950s…) had he wanted them, he could have had a 3×4 derailleur setup at least.
Hub gears are often portrayed as heavy and inefficient. They are neither; tests reported in the IHVPA publication unexpectedly demonstrated that a well-worn humble SA 3-speed (included in the tests on a whim) was more mechanically efficient than modern transmissions, especially when the duty cycle in each gear is taken into account (the direct drive gear, as efficient as a fixed gear, would be the most used in a 3s or 4s SA gear). Back then a 4s derailleur would have been little lighter than a 4s hub gear, but far less reliable. Even today the adoption of an IGH incurs a small weight penalty only.
I happen to own a bike (originally built for training on) with a steel five speed SA hub gear (heavier than TG’s four speed I think), a steel SA hub generator, and a 531 frame. The frame isn’t as nice as it could be (it has PG main tubes and non-531 rear stays) and it doesn’t have especially lightweight components fitted to it. It weighs 28lbs, so I would say a fair estimate of TG’s bike weight (in the absence of any further info) might be 28-30lbs. I’ve ridden this bike somewhere in the region of 40000 miles in all conditions; unlike TG it has taken me many years to rack up these miles, but the bike has been fantastically durable and reliable as intended. [BTW The most I’ve managed is 100 miles a day for about 6 weeks; it nearly killed me, since I physically couldn’t eat enough food to maintain my weight]
Arguably the (absolutely brilliant) invention and production of the hub generator was a key facilitator for TG’s record-breaking efforts; without it he would have been unable to have a reliable and efficient light source. (It might be a good idea if you could show a picture of an SA hub generator and not a tyre-driven generator BTW). Modern hub generators can be more powerful, but it seems they are no more efficient; I have carried out some ad-hoc efficiency tests on SA hub generators from the 1950s, and they indicate ~3W drag @ 1 to 1.5W output, and a no-load drag of
I don’t wish to downplay TG’s achievement in the slightest, but an additional 10lbs bike weight wouldn’t have slowed him very greatly. With the parts he was using vs modern ones I estimate he would have scope for maybe 1% improvement in efficiency in transmission/parasitic losses, not without compromise to reliability etc. Rolling resistance losses are unknown, but I’d be surprised if there is very much to be gained there; modern low CRR tyres are starting to look remarkably like 27×1″ HPs in fact. By contrast modern bicycle aerodynamics could have netted TG a useful benefit; having said this his riding position (for an endurance rider) was already very aerodynamic, and the bulk of the drag is on the rider, not the bike.
I am very pleased to see TG’s record commemorated on this website, and I do hope you find my comments of interest.”
Do you agree, disagree – or have anything else to add? Please leave your comments below.
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