Dead Roman

anybody keeping up with this? The new bike looked like a pile of crap at first is now looking like something that might actually work. It seems he has had tons of problems getting things together for whatever reason. Is beyond the realm of possibility that he could actually make this happen?

Mobile 155

A Prone Bike? A long shot at best.

Dead Roman

They said the same thing abt his track bikes.

cplager

Beyond the realm of possibility? No, absolutely not. Likely? No, absolutely not.

I heard him taking the bike outside and riding it, but absolutely nothing as far as what kind of speeds were reached just tootin' 'round.

Even if it were possible, it almost certainly wouldn't be Graeme who could put out enough power himself. Maybe earlier in his career, but he's not exactly young anymore.

Edit: Graeme's apparently only 5 years older than Sam Whittingham, so maybe not as too old as I thought

All that being said, I'd love to see a proper attempt. And if he tries, I'm rooting for him.

Dead Roman

Graeme has said he has done 40mph with no aero shell, confirmed by a pace car. I reckon he could do pretty damn good with the fairing. It looks like he really is payig a lot of attention to te aeros. A lot of the stuff Hoerner talks about in his aubject matter on interference drag describes shapes very similar to his shell.

I wouldnt be suprised if he actually does go fast. Whittingham isnt an amazing physical specimin at that. Put a real pro cyclist in varna diablo and I be it would get a lot closer to 100mph.

cplager

Remember air resistance grows (at least) speed squared. So we're looking at more than 50% more resistance at 100 mph. I doubt anybody could get the Varna to go that fast.

Hopefully Graeme was not going full bore when he hit 40. (100/40)^2 = 6.25. I doubt the shell makes his bike behave as if it had 1/6th the cross section. I'll consider Graeme's attempt hugely successful if he breaks 80 mph, and that's only a factor of four he needs to find...

fietsbob

Theres a NL Uni engineering dept, working on a web-cam & monitor scheme to lower the profile further,
reducing the windows to ones on the sides, & no head bubble.

rm -rf

It's even worse than that. Power increases by the velocity cubed. The drag increases as the square of the velocity, but then the work is done in half the time, making it 8 times as much power to go twice as fast. See the wikipedia explanation.

Obree's bike frontal area must be bigger than a prone rider riding between the wheels, just off the ground. That'll make it harder to go fast.

Dead Roman

What do you need a university engineering dept working on monitors for? Jesus I could bodge that up with some radio shack security gear.

Dead Roman

Maybe not 1/6th the cross sectional area, but thats not what you look at when calculating drag. You look at the aerodynamic "flat plate area". Reducing cross sectional area does not automatically reduce drag. I think its VERY likely that the flat plate area with the shell will be 1/6th of that without also, do your calcs assume the power output will be the same on the record attempt as it was for him going 40mph?

fietsbob

But they made the body out of Carbon fibers, and used Wind tunnels to test and optimize the shape
Maybe with a big enough computer, and the right data streams that can be modeled and changed
without making a physical model.

and By using the monitor to see the course center line,
they cannot see where they are going any other way But, as the benefit they don't even have to raise their head
so the highest oint on the body is clearance for the wheels inside.

Obree is in a prone position, face down.. recumbents are in a supine position, face Up..

Prone is a Position Snipers shoot from , laying on the ground.

yea and the wind tunnel testing can be done during the spring Tornado season
.. on the cheap too..

cplager

The cross sectional area itself will actually increase very slightly when he puts on the fairing. What he will do is reduce the drag coefficient. And I don't think he'll drop this coefficient by a factor of 6.

And rm -rf is right; I was talking about force. If you talk about power (which we cyclists usually do), we're talking about the cube, not the square.

Yes, we don't know if he was putting out anything near full power on his 40mph test run. If he was, he's completely sunk. Even if he wasn't, there's a big difference between riding at 40 mph (which I can do if the hill is big enough) and 80 mph, not to mention his goal of 100 mph.

If I were a betting man, I'd bet against him. I'm not, so if he tries, I'll root for him. But I won't be holding my breath.

hueyhoolihan

you know, if it were possible to just design the various dimensions of the bike and it's drag, etc. and measure the rider's output the max speed could be calculated without even building the bike, let alone making it ride-able and then actually riding it. yet they do. so i have to assume it is not all that clear cut...

Dead Roman

Im not talkig about cross sectional area. Im talking about The sum of the drag of the whetted area of the surface of the vehicle. Which is MUCH greater without the shell. This is neither drag coeficient nor cross sectional area.



Just trying to clarify.

Mobile 155

I would be pulling for him as well. That being said I have been to a few HPV events and prone bikes fell out of favor back in the late 80s. On a prone bike it is all legs, on a bent you can use the seat back to push against. I don't understand how the reverse bents work or how they pilot the machines but they are fast. If you lived closer to me I would wager lunch he doesn't make it. I also think, IMHO, that Battle Mountain is the perfect course to set the record or has been. https://www.ihpva.org/hpvarec3.htm#nom01

StephenH

Just glancing over his website and all, I am reminded of the world-land-speed record attempts for automobiles. Craig Breedlove was working trying to break the speed of sound, basically by experimenting and fixing what broke and hoping he didn't die in the process. Richard Noble invested time and money in a proper attempt, with a driver that knew what he was doing, and the record was set. Graeme Obree seems to be very much on the Breedlove-approach, and does not inspire a lot of confidence.

I like the little quote on Graeme's site: "When a true genius appears, you can know him by this sign: that all the dunces are in a confederacy against him.” Unfortunately, it's not that easy. You can be like Tesla, a certified genius and still a crackpot.

Dead Roman

While I understand what you are saying, you cant really apply to Obree, since he has already set world records on his kitchen built bicycles.

cplager

I do agree that Mr. Obree has proven himself in the past. But given that he claimed he'd hit 100 mph before even building the bike, I'm shall we say, skeptical. And that hasn't improved much since seeing the bike.

What a story it would be if I'm wrong! But I'm probably not.

Jeff Wills

Sam was on the Canadian National Team a few years back. George recruited him because he's a smaller rider but still managed to win road races in sprints- an attribute usually reserved for larger riders. He's as close to a "real pro rider" as anybody else in the HPV world.

Also, the Varna bikes have had the same basic design for almost 20 years. (I hosted George Georgiev and his previous rider, Paul Buettemer, when they came to Portland for some test track time in 1996. The current bikes are somewhat similar.) So they have many years of testing, working out the details of what makes a fast HPV fast. I'll bet Sam has more time riding an HPV above 70 mph than everyone else combined.

That being said, I hope Obree refines his machine to where it is competitive with other high-speed HPVs. He brings a spotlight on this odd corner of the bicycle world.

Looigi

ooops

flatlander_48

I think I see your problem...

Dead Roman

*rolls eyes*

Im an electrician and data tech. Ive got tons of experience with cameras. I could have a panoramic camera setup rigged up in Graemes bike in a few days. Connecting a camera to an LCD just isnt a difficult task. All I am saying is everything one needs to to it is available at your local electronics supply store.

StephenH

Craig Breedlove set some records too, but was still outclassed by people who did it better.

But consider that with the current HPV and record attempts, the major issue is optimizing aerodynamics, which can become a very involved problem, and one on which Mr. Obree doesn't seem to have started yet.

fietsbob

it's not the camera per se ,it's what the low drag body shape can be if you dont need to see out a window,at all .

chaadster

I'm not sure I follow you here.