lightweight/racing internal hub system, how light/efficient could it be built?

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The utility cyclist
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lightweight/racing internal hub system, how light/efficient could it be built?

Post by The utility cyclist »

So I was mulling some ideas as to where racing kit/transmission might go in the future.

I suggested replacing the derailleurs with a wirelessly shifted internal hub with say 18 straight through gears so as to not have the bigger jumps you get in a Rohloff which at 13%+ are not ideal for racing (or any cycling IMHO but that's for any day).

So could an internal gear hub be made using carbon fibre for the shell with say a carbon axle, could the internal gear sprockets be made lighter with materials that aren't required for circa 60,000 mile longevity? Could those gears be made in such a way to take up less space (thus a smaller overall size) or is there a completely different way to actually get the gearing without any individually spaced sprockets at all?
Could you build it with fewer than 32 holes
Could the gears be changed using a wireless system instead of mechanical?

Given the already smallish difference in % efficiency of transfer of power (not sure what they measure against tbh) an internal hub purely designed for racing/low mileage would have an even higher % of efficiency, if you are losing both derailleurs plus a chainring wouldn't that theoretical gear system be more aerodynamic than is current?
Whilst the weight of the hub will still be heavier than a high end rear hub + cassette, I would presume that weight in the centre of the wheel isn't going to make much difference even on a pro bike as you'll still be under the UCI weight limit as is.

Thoughts?
BigFoz
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Re: lightweight/racing internal hub system, how light/efficient could it be built?

Post by BigFoz »

It's an interesting concept. Would a larger diam carbon hub provide shorter spoke run and lighter / stiffer wheels? You wouldn't have to offset it as you do now, which might help longevity. It would be more aero. I think 18 internal is a bit of a stretch though. But Aqua Blu are attempting to ride 1x11 next year, so less might work out. If the internal gears were on a cassette, like a MotoGP bike etc, you could still do ratio changes appropriate to stages. Could you combine it with a limited internal gearbox in the BB, like Colnago / Ferrari tried in the '80s? Bet that could be done smaller and more reliably now too - maybe a 3x7 or 3x8?

Unfortunately, my imagination is fine, but my engineering skills lacking, so I suspect someone will now say why it's a rubbish idea...
Brucey
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Re: lightweight/racing internal hub system, how light/efficient could it be built?

Post by Brucey »

I can see that working; 18 = 3x3x2, so you could have a two-stage rear hub (2x3) and a 3s bottom bracket gear, or something like that.

Unfortunately the system is liable to be a bit lossier than a good derailleur gear but maybe you could recover some of that with improved aerodynamics or something, as you suggest. A singlespeed chain drive inside a case is pretty slippery; the case could be made structural.

Stuff like wheel/tyre changes would have to be thought through though.

cheers
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PH
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Re: lightweight/racing internal hub system, how light/efficient could it be built?

Post by PH »

There's no advantage to the pros with their teams of mechanics and custom gearing to suite the rider and stage, with an idea of longevity that doesn't see past the finish line. And that sport drives fashion which is why you see so many people on unsuitable bikes.
Could it be done? Yes, electronic hub shifting is already here, as are frame mounted gearboxes, there's no shortage on engineering skills or lightweight materials, weight probably isn't an issue which is why the UCI have a minimum limit. All that's lacking is a motive.
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The utility cyclist
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Re: lightweight/racing internal hub system, how light/efficient could it be built?

Post by The utility cyclist »

PH wrote:There's no advantage to the pros with their teams of mechanics and custom gearing to suite the rider and stage, with an idea of longevity that doesn't see past the finish line. And that sport drives fashion which is why you see so many people on unsuitable bikes.
Could it be done? Yes, electronic hub shifting is already here, as are frame mounted gearboxes, there's no shortage on engineering skills or lightweight materials, weight probably isn't an issue which is why the UCI have a minimum limit. All that's lacking is a motive.


Don't quite understand what you're saying, if a system can be built that is more reliable compared to what exists (less chance of dropping a chain under duress for instance) and thus is more likely to get you over the finish line and to boot is more aerodynamic to the point it overcomes any deficiency in weight/transmission then surely that would be something racing teams would want.

I also don't understand what you mean by unsuitable bikes, unsuitable for what, it's nothing to do with the discussion in any case but if it could be proven that x has a gain over y in terms of racing or comfort or indeed make people want to ride more then that isn't fashion is it, that's performance. People want as much help as they can get especially at times when you're getting older but also if you want to go that little bit faster for the sheer hell of it, whatever the top teams/riders are using gives that why is it unsuitable, who dictates what any given bike is unsuitable just because you don't agree with what you deem to be a 'fashion', isn't it down to individuals to make their own choices,just because something isn't always perfect/ideal doesn't make it unsuitable and what is suitable for one isn't the same for another.

If racing went to enclosed chain and hub gears would you deem that to be a fashion and the bikes made to be sold to your average punter unsuitable? What about the fashion for other modern tech like derailleur gears and braking systems, synthetic materials for saddles, tyres, alloy rims etc?
PH
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Re: lightweight/racing internal hub system, how light/efficient could it be built?

Post by PH »

The utility cyclist wrote:Don't quite understand what you're saying, if a system can be built that is more reliable compared to what exists (less chance of dropping a chain under duress for instance) and thus is more likely to get you over the finish line and to boot is more aerodynamic to the point it overcomes any deficiency in weight/transmission then surely that would be something racing teams would want.

So which pro bike race has been lost recently by bike unreliability? I'm sure it happens, but so rarely that I doubt hub gears would be any more reliable. The case for an enclosed system being more aerodynamic and that compensating for the weight increase isn't a given, my feeling is that at best it would be neutral and there isn't a problem at the top level waiting to be solved. The real advantages of enclosed gearing systems comes from long term reliability and lower maintenance requirements, they're not going to be seen as advantages in top level sport. Where I am surprised they are not more common is in off road sport, though I suppose that doesn't attract the sponsorship that would drive the manufacturers.
As for unsuitable bikes - I've only done a few miles this morning, seen maybe twenty people out on their bikes. Despite it being a bit damp less than half had guards, despite all the broken tarmac many had very narrow tyres, a fair proportion appeared to have the bars lower than optimal for their fitness, even on the slight slopes some were struggling away in bottom gear. Please don't get me wrong, people out on bikes is good, any bike. But if you put fashion aside a good proportion of the cyclists I saw out today would IMO have enjoyed their cycling more on a different bike.
Brucey
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Re: lightweight/racing internal hub system, how light/efficient could it be built?

Post by Brucey »

leaving aside the rather larger and insoluble question of whether folk are riding 'the right bikes' on a sunday morning, I think that professional level road racing is currently blighted by equipment that isn't really reliable enough. This year's TdeF was very nearly lost because of equipment failure. A TT stage outcome on this years ToB was almost certainly altered by equipment failure. Whether it is widely acknowledged or not, there is certainly room for improvement there.

cheers
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mattsccm
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Re: lightweight/racing internal hub system, how light/efficient could it be built?

Post by mattsccm »

Equipment does fail but so rarely that changes are probably not worth it. It would be daft to assume that at the top racing level no stone is left unturned at finding the optimum within regulations.
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