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PostPosted: Wed Jun 20, 2012 12:47 am 
Retro Guru

Joined: Sun Mar 27, 2011 11:36 pm
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Location: Liverpool
After much thought this came out as an illustration of how to achieve greater drive ratios / more power per turn. It's only me messing about don't forget, it's not a technicians diagram :-) Later everyone, Laz.

PS: If i'm not mistaken a 58t x 15t = about 45-50mph in perfect conditions before it free wheels. Diagram illustrates low cadence / high output.

PPS: "If anything comes of this ALL ideas are sole ownership of Graeme Obree ... if he wants them :-)


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Obree NEW bike.jpg
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Last edited by Lazarus on Wed Jun 20, 2012 12:49 am, edited 1 time in total.
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 Post subject:
PostPosted: Wed Jun 20, 2012 12:48 am 
Devout Dirtbag

Joined: Sat Jul 23, 2011 5:58 pm
Posts: 134
lazzarus
you sound like a very knowledgable kind chap sounds like a great idea
if i could advise i would but alas i fear it would be like teaching you to suck eggs mate
so everyone else its over to you


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PostPosted: Wed Jun 20, 2012 12:56 am 
Retro Guru

Joined: Sun Mar 27, 2011 11:36 pm
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Location: Liverpool
Haha Rocky :-) Thought everyone was in bed mate :roll: "It's just a bit of a laugh really, but me being me, it helps because I do know some stuff about un-invented things ... been doing it a long time now :-) I know the concept is there, but it will take a small army of wealthy technicians to iron it out, the materials just to knock 1 up as a test piece would set me back £2000 (had a good look last night at titanium sheet metal to make the special tubes myself .. used to be TIG welder once in my past).

Maybe, some of what I post will ring bells for someone who knows the guy, and maybe, just maybe ... "I'm right'ish" and it'll give the guy the credit he deserves. ALL of this from me is solely because of him, his concept has certainly lit my fire :-) I'm just good at trouble shooting / making concepts for viable :-) Later buddy, Laz.

PS: I don't know what speeds a 700c wheel directly powering a 12t rear cog will bring, but it's got to be in excess of the 100mph mark. The current riders are using 58t-60t x 12t equivelants to get their speeds. I guess a 700c wheel is about 360t in total ?


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PostPosted: Wed Jun 20, 2012 4:48 am 
Old School Grand Master
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Lazarus wrote:
quite impressive looking concept bikes, but why only so slow for all that technology? I'm not knocking what they do, but it seems obvious to me that something is wrong with the concept itself, even if it has hit 82mph.

They're not concept bikes. This is the competition.

All bikes are power-limited (by the rider). Power expended overcoming aerodynamic drag increases with the cube of speed (i.e. the power required to cruise at 80mph is eight times the power required to cruise at 40mph). It's all about the fairing.

Quote:
I get the impression they are using front wheel drive ? Why not twin wheel drive ?

Some (e.g. the Diablo) are using a driven front wheel. Others (Kyle Edge, Blue Yonder) use a driven rear. There's no point using two driven wheels. It's a flying-start competition on a straight road. Traction doesn't come into it.


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PostPosted: Wed Jun 20, 2012 5:29 am 
Retro Guru

Joined: Sun Mar 27, 2011 11:36 pm
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Location: Liverpool
Hi again Jim :-) Thanks for all the info, its nice to hear from someone up on the sport & the rules.

"All bikes are power-limited (by the rider)".

True my friend, but placement & sizes of the parts that permit this power are an open field except for overall bike dimensions. I called them concept bikes because no 2 are alike really, except that they have shells to reduce drag / control airflow.

"Power expended overcoming aerodynamic drag increases with the cube of speed (i.e. the power required to cruise at 80mph is eight times the power required to cruise at 40mph)".

I totally understand what you're saying here, but where does this equation come from that "twice the speed of a bike requires 8times the power to achieve that doubling of speed ?" Have engineers written it down, or calculated it ? It seems an odd piece of science/physics. I only know bits & pieces about aerospace/flying and don't recall learning that an aeroplane needs 8times more power to achieve a velocity capable of liftoff ? If this equation were true, it would apply to ALL vehicles would it not ? ie: a car ? Not questioning your knowledge, simply trying to grasp where it came from :-) In essence translated to bike speak, " a bike cruising at 40mph on a 56t x 13t (which it probably will) would need a factor of x8 to reach & hold a speed of 80mph ? I'm confused by the maths. This is obviously a resistance question, not a power question :-)


"It's all about the fairing."

What's fairing Jim ? "About how air travels over certain shapes/objects"

What you write is very interesting, so please don't get angry at me if I dig around a little. It's info like this that keeps my brain flowing. Thanks again buddy, yours Laz.

PS: "My design wouldn't be disallowed then ?" Does it contravene any rules you know of ? I've read a fair bit now, but not the exact rule book. What I have read gave the impression of it being open ended in design so long as it has NO assistance from motors/non human powered elements. Use of / conversion of resistance was I assumed within the limits ? Later buddy, Laz.


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PostPosted: Wed Jun 20, 2012 5:29 am 
Retro Guru

Joined: Sun Mar 27, 2011 11:36 pm
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Location: Liverpool
Oh forgot to ask, "It's a flying-start competition on a straight road. Traction doesn't come into it."

It's not a time trial run as such over a very short distance is it Jim ? ie a sprint race against the clock so that maths determines the speed rather than the actual speed being measured over distance ? I got the impresion that they rode 100km from 1 part of the web page. Maybe I misread it ?

Oh well, I'll have to read some more tomorrow :-) Later Jim, Laz.


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PostPosted: Wed Jun 20, 2012 5:51 am 
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Lazarus wrote:
placement & sizes of the parts that permit this power are an open field except for overall bike dimensions.

True, and if Obree's design allows him to design a more aerodynamic envelope, it could give him an advantage - as long as it doesn't significantly limit the power he can produce.

Quote:
I totally understand what you're saying here, but where does this equation come from that "twice the speed of a bike requires 8times the power to achieve that doubling of speed ?" Have engineers written it down, or calculated it ? It seems an odd piece of science/physics.

http://en.wikipedia.org/wiki/Drag_equation

Classically, aerodynamic drag (force) increases with the square of velocity. Power is force x velocity, so the power required to overcome aerodynamic drag increases with the cube of velocity.

Quote:
What's fairing Jim ?

The aerodynamic shell that encloses these bikes is called a fairing.

Quote:
My design wouldn't be disallowed then ?

No, not as far as I can tell. If it's purely human-powered, it's allowed.

Lazarus wrote:
It's not a time trial run as such over a very short distance is it Jim ?

If he's going for the IHPVA absolute World Speed Record (and from what I can tell, he is) it's a straight run through a speed trap. So he has a long run-up to build up to top speed, but only has to maintain that speed for the length of the trap. I think it's about 200 metres.


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PostPosted: Wed Jun 20, 2012 9:04 pm 
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one-eyed_jim wrote:
He has a long run-up to build up to top speed, but only has to maintain that speed for the length of the trap. I think it's about 200 metres.


Yup, it's a five mile run up, then a flying, timed 200m.

I've been following Obree's HPV project with some interest. The guy is a legend! The prone position piqued my interest, I figured that in a stretched out, prone position, you're not using your back and leg muscles at their most effective length, so I did some reading up, and it turns out that the prone position is 20% less powerful than the 'traditional' recumbent position. So, I guess the question is, if Obree's position is 20% less efficient than an 80mph recumbent, is his teardrop design going to be aero enough to get him up to 100mph?

With no disrespect to Obree, he is a formidable endurance athlete, but the current holder is a sprinter. Way back in 2001, Jason Queally - Olympic kilo champ at the time - had a pop at the record in a £250,000 HPV designed and manufactured for him by an F1 chassis maker, and got beaten by a 15yr old girl!! (albeit still riding at 65mph).

I REALLY hope he can do it, but, I think the deck is stacked against him on this one.


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PostPosted: Thu Jun 21, 2012 4:25 pm 
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Joined: Sun Mar 27, 2011 11:36 pm
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Hi again Jim :-) "Thanks for the extra info buddy, nothing like a horses mouth the hear something from" :-) I'll now start to digest what it all means, and post again with how it pans out. Really appreciate your input, all the best my friend, Laz.

Hi S Bob :-) Great piece of info there, espcially the 15year old girl beating the £250,000 machine. It's info like this that proves "theoretical on paper science is not always up to its claims / expected results." I'll keep scribbling away at my ideas and see how they pan out in here. Couldn't pick a better audience for feedback.

I doubt they are many who will not be rooting for Graeme :-) He has that effect on people ... "he's just that kind of rank outsider we all cheer for". I'm sure he'll stop being obsessed with this and become more focussed, especially as the reality bites. I'm hoping he rises to the challenge and doesn't let it beat him down :-) All the best, Laz.


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 Post subject: Speed record Attempt
PostPosted: Fri Jun 22, 2012 12:07 am 
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Joined: Sat Jun 16, 2012 4:17 pm
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Location: Isle of Man
One of the last true cycling milestones without the usual red tape


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