Reply to: One for the bicycle geeks

[DaveB]

Yep; I think what he'll have is a big gear or two at the back, with a chain powering the two smaller cogs on the front gear, and a chain from the big front cog to the back wheel, possibly with a derailleur on the back just like you see on racing bikes and mountain bikes. You can't make the speed with just one gear and chain; even if you could pedal an enormous 50cm wide gear, the cog would be so big it would cut through his gut, if you see what I mean.

From the article:

To reach that speed, he will be pedalling in a gear, which is around three times bigger than the top gear on a road racing bike. The pedals turn a chain which drives one set of gears, which then transfer the power to the rear wheel through a second chain, doubling the pedal power of a conventional bike.
A single turn of the gear will propel his bike around 30ft – compared with around 10ft achieved by a road racer's top gear.
"You just roll it and go up through the gears. If you get into the top gear you are already doing 80mph," he said.

[Mich the Tester]

I just did, thanks for that! So he'll have a chain to there, from his pedals when fitted, which will connect to teh real wheel.

Now that does make mroe sense!

Yep; I think what he'll have is a big gear or two at the back, with a chain powering the two smaller cogs on the front gear, and a chain from the big front cog to the back wheel, possibly with a derailleur on the back just like you see on racing bikes and mountain bikes. You can't make the speed with just one gear and chain; even if you could pedal an enormous 50cm wide gear, the cog would be so big it would cut through his gut, if you see what I mean.

[Old Hack]

Look closer; there aren't any pedals under his belly, just a gearwheel (or two gears actually) in between two bars.

I just did, thanks for that! So he'll have a chain to there, from his pedals when fitted, which will connect to teh real wheel.

Now that does make mroe sense!

[Mich the Tester]

So the ones under his belly are just 'there'. OK, makes sense now

Look closer; there aren't any pedals under his belly, just a gearwheel (or three gears actually) in between two bars.

[Old Hack]

He hasn't fitted the pedals yet, only the front gear; the pedals will be at the back.

So the ones under his belly are just 'there'. OK, makes sense now

[Mich the Tester]

I may be missing soemthing obvious, but hows he going to cycle it, with the pedals where they are?

He hasn't fitted the pedals yet, only the front gear; the pedals will be at the back.

[Old Hack]

I may be missing soemthing obvious, but hows he going to cycle it, with the pedals where they are?

[Mich the Tester]

It's high time people shot officialdom that would hamper innovation in bicycle technology.

I think most UCI officials would be dead if murder wasn't illegal. Having spent years hampering Obree and others (usually Brits) who used their brains to innovate and win, they've dreamt up a new wheeze, making bicycle manufacturers pay several thousand euros per new model to get bikes certified with a little UCI sticker for racing, whether it's track racing, bmx, mountain or road. Now firstly this hampers the small manufacturers who build a limited number of custom bikes, but secondly hampers people trying to ride on a limited budget, because the big manufacturers who get the sticker then bump up the price as supply of approved bikes is limited. At the moment there are only 5 track bikes on the list of UCI approved bikes; either you pay a couple of grand for one of those or you buy a pre 2010 model bike and hope that when the officials turn up with their measuring jigs you're alright and they don't find that your saddle is 1mm too short or your toes stick out 1mm too far ahead of the pedal (yes, that's how sad the regulations are). Now of course, this scheme reeks of corruption, and some cyclists, particularly in the USA, are setting up their own races outside of the UCI jurisdiction.

Cycling, especially track cycling could be on the edge of another golden age, given the publicity in Britain Europe around the Olympics, the brilliant facilities in London, Manchester, Newport, Amsterdam, Apeldoorn (where I ride) and of course the strong British, French and German presence at the olympics, the GB-Aus rivalry etc. The crowds could be packed in for evening races and have-a-go sessions, but if people see disqualifications on stupid technicalities and all innovations like aerodynamic compression suits, plastic coverings for helmets etc being banned, why should they turn up? Why should anyone invest in a bike if he's scared of being disqualified? It won't go through a new golden age with these anti-innovation dickheads at the UCI.

[TimberWolf]

Someone on the torygraph site worked out he needs to produce 900 watts for the four seconds that he goes flat out; that's very do-able, but I'm not sure how much power he needs to produce as he works up through the gears. Anyway, I'd expect, given his athletic ability that he can produce about 1500watts in a short burst, allowing for the fact he's 46 and probably produced about 2000 watts in a sprint at his peak.

I think he started with 900 watts and worked back for aerodynamic consequences. And what it meant is that it's a very tall order. Someone also made an interesting observation that Obree's bike will be wider at the rear, conjecturing that this shape would negatively impact aerodynamic performance. It's all about getting that shape tested in a wind tunnel and comparing it with the current record holder, and being crammed inside like a sardine.

What's mind boggling is that if a bike can do 100 mph, doing 30 mph would be something like 1/10 as hard and use 1/30 of the power. It's high time people shot officialdom that would hamper innovation in bicycle technology.

[Mich the Tester]

Maybe, though the difference in going 82mph probably isn't inconsiderable because of the square and cube power relationships with the formulas for force and power respectively.

To save plugging into the entire formula, just looking at the major drag force, the air:

Force = (100/82)^2 = 1.5. 50% more.
Power = (100/82)^3 = 1.81. 80% more.

That's worse-case, it won't be as bad as that if he has a really slippery shape , since other losses not related to air speed play a greater role, but I haven't run the numbers.

Someone on the torygraph site worked out he needs to produce 900 watts for the four seconds that he goes flat out; that's very do-able, but I'm not sure how much power he needs to produce as he works up through the gears. Anyway, I'd expect, given his athletic ability that he can produce about 1500watts in a short burst, allowing for the fact he's 46 and probably produced about 2000 watts in a sprint at his peak.

[TimberWolf]

Perhaps it's also a factor that by lying on his front the force he produces is all going backwards; in a recumbent position, you're pushing forwards, effectively pushing the bike backwards in the direction you don't want to go and relying on the mechanical stuff to translate that into forward motion; maybe the power is more effectively transferred in his forward facing position; maybe it's only a tiny difference, but enough.

Maybe, though the difference in going 82mph probably isn't inconsiderable because of the square and cube power relationships with the formulas for force and power respectively.

To save plugging into the entire formula, just looking at the major drag force, the air:

Force = (100/82)^2 = 1.5. 50% more.
Power = (100/82)^3 = 1.81. 80% more.

That's worse-case, it won't be as bad as that if he has a really slippery shape , since other losses not related to air speed play a greater role, but I haven't run the numbers.

[Mich the Tester]

He's forgotten the chain. Back to the drawing board.

And from past experience, no chain = sudden agonising pain in the goolies/coccyx. And the pain is probably even worse when you have no pedals either.

Give him a chance to finish building it, boys.

[Mich the Tester]

Yes, he has a background of developing his own Heath-Robinson record breaking bikes. I was disappointed to learn that his last innovation was banned. If I were going for a record I'd imagine that shape to be the better than recumbent too, if only for psychological reasons. It seems to attack the road aggressively. It's important to minimise frontal surface area and have a nice streamlined shape (hard to say what difference from the classic recumbent style would be), which is where most of the power losses would occur:

power = weight * velocity * friction (tires, bearings, chain) + aeroDrag * velocity^3

At that speed this boils down to aerodrag * the cube of the velocity,

where aerodrag = 0.5 * airDensity * CoEffAirResistence * frontalArea

where CoEffAirResistence will be measured in a wind tunnel.

So he wants a nice slippery shape (long is usually good) and minimising frontal area, and secondary considerations being weight and frictional losses.

Perhaps it's also a factor that by lying on his front the force he produces is all going backwards; in a recumbent position, you're pushing forwards, effectively pushing the bike backwards in the direction you don't want to go and relying on the mechanical stuff to translate that into forward motion; maybe the power is more effectively transferred in his forward facing position; maybe it's only a tiny difference, but enough.

[TimberWolf]

He's forgotten the chain. Back to the drawing board.

And from past experience, no chain = sudden agonising pain in the goolies/coccyx. And the pain is probably even worse when you have no pedals either.

[Mich the Tester]

Yes, he has a background of developing his own Heath-Robinson record breaking bikes. I was disappointed to learn that his last innovation was banned.

Yep, the UCI are currently trying to take cycling back to the 19th century.