150 mph bicycle
Zupergee
I'm designing a bicycle for a land speed record attempt. Does anyone out
there know what tires were used on John Howards' bicycle or what tires
could handle that speed? Thanks!
Gordon Schuck
Sheldon Brown
They used motorcycle rims and tires.
I believe it was this land-speed record attempt that suffered mysterious
flatting at high speed. Had 'em buffaloed until they realized their
mistake: to save weight, they left off the valve caps. Unfortunately,
the "centrifugal force" at speed was compressing the springs of the
Schræder valves and let the air out!
If you are serious about this, there is one very clever invention that
was used by Alan Abbott when he set his record: The car had two
drivers!
One driver was facing forward, steering; the other was facing backward,
watching the bicycle and monitoring the gap between car and bicycle.
This second driver had control of the accellerator and, I believe, the
brakes.
In Howard's attempt, they tried to give Howard control of the car's
speed by radio remote, but it was too complicated, and he had enough
to do operating the bicycle without having to drive the car as well,
so they gave up on this gimmick.
Sheldon "Too Fast For Me" Brown
Newtonville, Massachusetts
+---------------------------------------------------------+
| We can be knowledgeable with other men's knowledge, |
| but we cannot be wise with other men's wisdom. |
| -- Michel de Montaigne |
+---------------------------------------------------------+
http://www.sheldonbrown.com/biz/hub/
Harris Cyclery, West Newton, Massachusetts
(617) 244-1040 FAX 244-1041
Pete Ruckelshaus
Zupergee wrote:
>
> I'm designing a bicycle for a land speed record attempt. Does anyone out
> there know what tires were used on John Howards' bicycle or what tires
> could handle that speed? Thanks!
>
I believe motorcycle road racing tires were used in JH's WR, and would
probably be the most logical choice. Of course, it would be more
impressive to do it on hackin' huge tractor tires :-)
Pete
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Tom C. Shaddox
Pete wrote:
>
> Zupergee wrote:
> > I'm designing a bicycle for a land speed record attempt...
> > ... know what tires were used ...
>
> I believe motorcycle road racing tires were used in JH's WR...
I seem to remember that the tires partially deflated during the first
run because the centerfugial force at 120mph+ caused the valve stems to
depress. Even though the laws of physics are the same for every one,
not many bicycle designers have practical experience at 100mph+. Bon
chance.
Tom
Stuart Paynter
In article <19970309043...@ladder01.news.aol.com>, zupe...@aol.com (Zupergee) writes:
|> I'm designing a bicycle for a land speed record attempt. Does anyone out
|> there know what tires were used on John Howards' bicycle or what tires
|> could handle that speed? Thanks!
One of the major tire manufacturers (Michelin??) makes a tire specifically
for the "Sun" racer, solar powered vehicles. They are used by almost all
the teams as bicycle tires don't stand up to the heat/sustained speed that
the vehicles are racing at. You might try one of the HPV newsgroups for more
info.
SP
Jobst Brandt
Sheldon Brown writes:
>> I'm designing a bicycle for a land speed record attempt. Does
>> anyone out there know what tires were used on John Howard's bicycle
>> or what tires could handle that speed?
> They used motorcycle rims and tires.
> If you are serious about this, there is one very clever invention
> that was used by Alan Abbott when he set his record: The car had two
> drivers! One driver was facing forward, steering; the other was
> facing backward, watching the bicycle and monitoring the gap between
> car and bicycle.
More important is how you build the air ducting of the windscreen.
Since this is an aerodynamic problem and no bicycle rider has enough
strength to rotate only a wheel at those speeds, the power must be
transmitted to the rider by air ducting. With appropriate design, the
rider can, as did Howard, use the brakes while setting the record.
Make sure you are turning the pedals, lest someone records this as a
coasting event. A fixed gear is dangerous, but it helps.
Jobst Brandt <jbr...@hpl.hp.com>
Bill
Jobst Brandt <jbr...@hpl.hp.com> wrote in article
<5g9i01$a...@hplms2.hpl.hp.com>...
> More important is how you build the air ducting of the windscreen.
> Since this is an aerodynamic problem and no bicycle rider has enough
> strength to rotate only a wheel at those speeds, the power must be
> transmitted to the rider by air ducting. With appropriate design, the
> rider can, as did Howard, use the brakes while setting the record.
> Make sure you are turning the pedals, lest someone records this as a
> coasting event. A fixed gear is dangerous, but it helps.
I did not know this? So it really was a "air turbine" powered bike. Cute.
Bill
P.S. I don't think people realize just how hard it will be to take the
unassisted flying 200m record of 68 mph, accomplished at high altitude, and
get to 75 mph at near sea level (decimach challenge prize) ... darn near
impossible.
Zupergee
Jobst Brandt writes
Do you think that a derailleur would not function on the secondary drive
due to the centrifugal force of the chain? Could added spring tension, a
chain guide, and the lightest chain out there be enough to work or would I
need to do any shifting in the primary drive? Should I abandon the idea of
gears altogether?
Thanks in advance!
Gordon Schuck
Paradox Metalworks
Jobst Brandt
Stuart Paynter writes:
> One of the major tire manufacturers (Michelin??) makes a tire
> specifically for the "Sun" racer, solar powered vehicles. They are
> used by almost all the teams as bicycle tires don't stand up to the
> heat/sustained speed that the vehicles are racing at. You might try
> one of the HPV newsgroups for more info.
They also use the Avocet-Goodyear tire that is more widely used by
such vehicles. By the way, where is all the heat coming from to which
you refer? If there were measurable heat, the whole exercise would be
moot because these vehicles have so little power they could not afford
to use tires that generate perceptible heat.
Jobst Brandt <jbr...@hpl.hp.com>
Jobst Brandt
Gordon Schuck writes:
>> A fixed gear is dangerous, but it helps.
> Do you think that a derailleur would not function on the secondary
> drive due to the centrifugal force of the chain? Could added spring
> tension, a chain guide, and the lightest chain out there be enough
> to work or would I need to do any shifting in the primary drive?
I don't think I said that right. The rider cannot have any affect on
the speed of the bicycle except to use the brakes. The pedaling is
there only for appearances. John Howard was towed up tot he speed
where the windscreen eddies became large enough to propel him. The
fixed gear only made his feet go around.
You can do some calculations from the assumption that you can put out
1/3 horsepower and use the speed of 150 mph to see what that converts
to in thrust. Spreading 1/3 HP out at 150 mph leaves insufficient
thrust to just turn the wheels in air, if they are smooth disks.
> Should I abandon the idea of gears altogether?
Yes. You should first get a perception of the scale of things involved.
Jobst Brandt <jbr...@hpl.hp.com>
Jobst Brandt
Gordon Schuck writes:
>> A fixed gear is dangerous, but it helps.
> Do you think that a derailleur would not function on the secondary
> drive due to the centrifugal force of the chain? Could added spring
> tension, a chain guide, and the lightest chain out there be enough
> to work or would I need to do any shifting in the primary drive?
I don't think I said that right. The rider cannot have any affect on
the speed of the bicycle except to use the brakes. The pedaling is
there only for appearances. John Howard was towed up to a speed at
which the windscreen eddies became large enough to propel him. The
fixed gear was used only to make his feet go around.
You can do some calculations. Assuming that you can put out 1/3
horsepower, use the speed of 150 mph to see what that converts to in
thrust. Spreading 1/3 HP out at 150 mph leaves insufficient thrust to
turn just the wheels in air, if they are smooth disks.
Zach Kaplan
I tried to order some Avocet Freestyle 47-406mm (20 x 1.75") tyres a
couple months ago and was told by the Avocet rep they are no longer
in production and no longer available. Too bad, this was one of my
favourite wide 406mm tyres. I understand Ritchey is developing a similar
width 406mm version of the Tom Slick.
Zach Kaplan
Stuart Paynter
In article <5gfn71$c...@hplms2.hpl.hp.com>, jbr...@hpl.hp.com (Jobst Brandt) writes:
> Stuart Paynter writes:
>
> > One of the major tire manufacturers (Michelin??) makes a tire
> > specifically for the "Sun" racer, solar powered vehicles. They are
> > used by almost all the teams as bicycle tires don't stand up to the
> > heat/sustained speed that the vehicles are racing at. You might try
> > one of the HPV newsgroups for more info.
>
> They also use the Avocet-Goodyear tire that is more widely used by
> such vehicles. By the way, where is all the heat coming from to which
> you refer? If there were measurable heat, the whole exercise would be
> moot because these vehicles have so little power they could not afford
> to use tires that generate perceptible heat.
>
> Jobst Brandt <jbr...@hpl.hp.com>
I was refering to the fact that these are "solar" vehicles and the races are
nice sunny warm locations like across the Australian desert, or southern Cal.
Given that the air temperatures tend to be in the 35-40C range, the heat I
am talking about would be coming from the asphalt surface, not friction from
the tires. You know, black surface, hot sun, don't try and walk across it in
your bare feet kind of hot.
Heat is just one of the factors involved in the breakdown of a bicycle tire
in the sun-racer application. They just don't stand up to the application.
Consequently, Avocet-Goodyear, as you mentioned, have developed a tire that
more closely resembles a motorcycle tire specifically for this vehicle.
Stu
Ted Nichols-Payne
Jobst Brandt wrote:
>
>
> I don't think I said that right. The rider cannot have any affect on
> the speed of the bicycle except to use the brakes. The pedaling is
> there only for appearances. John Howard was towed up to a speed at
> which the windscreen eddies became large enough to propel him. The
> fixed gear was used only to make his feet go around.
>
> You can do some calculations. Assuming that you can put out 1/3
> horsepower, use the speed of 150 mph to see what that converts to in
> thrust. Spreading 1/3 HP out at 150 mph leaves insufficient thrust to
> turn just the wheels in air, if they are smooth disks.
>
>
Hmmm... I don't really like the Jobst baiting that goes on here, I find
it uncool, so please don't think I'm jumping on the "let's bash Jobst"
bandwagon when I say...
That's a load of crap.
You think there's some way to design an air dam on the back of a vehicle
to direct the turbulence in such a way that it will actually provide
thrust for a bicycle and rider? At 150mph? We're not talking about a
piece of paper here, we're talking about 150-200 lbs of man and bike.
The idea is for the pace vehicle to provide a 'dead zone,' a pocket of
air behind it for the cyclist to ride in, so the rider only has to
overcome friction from the bike (which can be considerable at 150mph)...
in practice, there is still wind resistance, as no air dam will provide
_total_ isolation from the atmosphere.
For the sake of argument, let's say the rider slipped back, out of the
relative calm provided directly behind the air dam, and into the "eddies"
to gain some type of thrust from them in an attempt to be pulled along
like debris behind a semi on the highway. What do you think the
turbulence at this point is going to be like? Anyone that owns a
motorcyle will tell you - that wind beats you up. Tailing a semi at
60mph on my Honda has taught me to stay back, lest I want to find myself
in the next lane unexpectedly...
And as to someone not being able to generate the horsepower to simply
spin a bicycle wheel at 150mph... considering I can spin my 36 spoke rear
wheel at approx 45-50mph _by hand_ (on the rack, wheel of the ground, top
gear, spin it as fast as you can with one hand), I think that given the
proper gearing, simply spinning a wheel at that speed (even a heavier
weight wheel) is definitely within the abilities of even an average
bikie.
Sorry, Jobst, this one doesn't fly.
Ken Ferschweiler
Ted Nichols-Payne (ank...@flash.net) wrote:
: And as to someone not being able to generate the horsepower to simply
: spin a bicycle wheel at 150mph... considering I can spin my 36 spoke rear
: wheel at approx 45-50mph _by hand_
And given that power to overcome air drag is roughly proportional to
v^3, do you really think you can put out 27-37 times as much power with
your legs as with your arms?
========================
Ken Ferschweiler Internet: ken...@cs.orst.edu
Department of Computer Science
Oregon State University
Ted and Jennifer Nichols-Payne
Ken Ferschweiler wrote:
>
> And given that power to overcome air drag is roughly proportional to
> v^3, do you really think you can put out 27-37 times as much power with
> your legs as with your arms?
>
> ========================
> Ken Ferschweiler Internet: ken...@cs.orst.edu
> Department of Computer Science
> Oregon State University
Jesus. Hell, I'm an ex-disc jockey, not a science professor, so I
probably am out of my league in this debate... I mean, I don't even know
if I spelled 'professor' right.
Still, life isn't an equation, and while I understand that the
aerodynamics of an object at 50mph are much different than that of an
object at 150mph, I stand by my original assertion... if you give me a
gear that will spin a wheel at 150mph at a pedaling cadence of 100 or so,
make that wheel spin freely off the ground, I'll get that wheel to 150.
And so will you.
Mark Drela
In article <332E2B...@flash.net>, Ted Nichols-Payne <ank...@flash.net> writes:
|> Jobst Brandt wrote:
|> > I don't think I said that right. The rider cannot have any affect on
|> > the speed of the bicycle except to use the brakes. The pedaling is
|> > there only for appearances. John Howard was towed up to a speed at
|> > which the windscreen eddies became large enough to propel him. The
|> > fixed gear was used only to make his feet go around.
|> >
|> > You can do some calculations. Assuming that you can put out 1/3
|> > horsepower, use the speed of 150 mph to see what that converts to in
|> > thrust. Spreading 1/3 HP out at 150 mph leaves insufficient thrust to
|> > turn just the wheels in air, if they are smooth disks.
|> >
|> >
|>
|> Hmmm... I don't really like the Jobst baiting that goes on here, I find
|> it uncool, so please don't think I'm jumping on the "let's bash Jobst"
|> bandwagon when I say...
|>
|> That's a load of crap.
No, Jobst is correct.
|> You think there's some way to design an air dam on the back of a vehicle
|> to direct the turbulence in such a way that it will actually provide
|> thrust for a bicycle and rider? At 150mph? We're not talking about a
|> piece of paper here, we're talking about 150-200 lbs of man and bike.
|> The idea is for the pace vehicle to provide a 'dead zone,' a pocket of
|> air behind it for the cyclist to ride in, so the rider only has to
|> overcome friction from the bike (which can be considerable at 150mph)...
|> in practice, there is still wind resistance, as no air dam will provide
|> _total_ isolation from the atmosphere.
What does the weight of the man+bike have to do with the aerodynamics?
The "dead-zone" behind a well-shaped windscreen is usually called a
"recirculation zone" in aero jargon --- for good reason. This zone
can have a forward velocity (relative to the car) of up to 20% or so
of the vehicle speed. So at 150 mph, Howard felt a ~30 mph tailwind,
whose negative drag delivered at least several horsepower to him.
Any pedaling effort of significant duration would have been puny
by comparison.
Mark Drela
_______________________________
o/LO .'
O .' Gravity-Powered Technologies Lab
.' MIT Aero-Astro Department 37-475
'
Ted and Jennifer Nichols-Payne
Mark Drela wrote:
>
> In article <332E2B...@flash.net>, Ted Nichols-Payne <ank...@flash.net> writes:
> |> Jobst Brandt wrote:
> |> > I don't think I said that right. The rider cannot have any affect on
> |> > the speed of the bicycle except to use the brakes. The pedaling is
> |> > there only for appearances. John Howard was towed up to a speed at
> |> > which the windscreen eddies became large enough to propel him. The
> |> > fixed gear was used only to make his feet go around.
> |> >
> |> > You can do some calculations. Assuming that you can put out 1/3
> |> > horsepower, use the speed of 150 mph to see what that converts to in
> |> > thrust. Spreading 1/3 HP out at 150 mph leaves insufficient thrust to
> |> > turn just the wheels in air, if they are smooth disks.
> |> >
> |> >
> |>
> |> Hmmm... I don't really like the Jobst baiting that goes on here, I find
> |> it uncool, so please don't think I'm jumping on the "let's bash Jobst"
> |> bandwagon when I say...
> |>
> |> That's a load of crap.
>
> No, Jobst is correct.
No, he's not. So there. (Okay, so I'm spending a lot of time with my 3
year old daughter, I'm picking up some bad habits)
>
> |> You think there's some way to design an air dam on the back of a vehicle
> |> to direct the turbulence in such a way that it will actually provide
> |> thrust for a bicycle and rider? At 150mph? We're not talking about a
> |> piece of paper here, we're talking about 150-200 lbs of man and bike.
> |> The idea is for the pace vehicle to provide a 'dead zone,' a pocket of
> |> air behind it for the cyclist to ride in, so the rider only has to
> |> overcome friction from the bike (which can be considerable at 150mph)...
> |> in practice, there is still wind resistance, as no air dam will provide
> |> _total_ isolation from the atmosphere.
>
> What does the weight of the man+bike have to do with the aerodynamics?
It takes a lot more force to move a man than it does to move a piece of
paper. Just trying to point out we're not talking about a small,
lightweight object being swept along...
> The "dead-zone" behind a well-shaped windscreen is usually called a
> "recirculation zone" in aero jargon --- for good reason. This zone
> can have a forward velocity (relative to the car) of up to 20% or so
> of the vehicle speed. So at 150 mph, Howard felt a ~30 mph tailwind,
> whose negative drag delivered at least several horsepower to him.
> Any pedaling effort of significant duration would have been puny
> by comparison.
> Mark Drela
> _______________________________
> o/LO .'
> O .' Gravity-Powered Technologies Lab
> .' MIT Aero-Astro Department 37-475
> '
30mph wind delivers several horsepower?
Just so I get this right - the car's velocity is 150mph, the bike/rider
velocity is 150mph, the air in the recirculation zone is approx. 180mph.
The airspeed relative to bike/rider is -30mph, a 30mph tailwind. Just
want to make it perfectly clear that we're talking about 30mph, and
that's giving bike/rider "at least several horsepower". So, if I go
outside on a windy day, gusts of up to 30mph, why aren't I swept off my
feet? If you ride your bike into a 15mph wind and your speed is 15mph,
do you have several horsepower of force working against you and your
measly 1/3 horsepower? This aerodynamic theory may work for you in the
lab, but it doesn't work in the real world.
Let's say the theory is correct, and we go back to Jobst's original
assertion, that John Howard could have coasted at 150mph, propelled along
by the 'windscreen eddies' in his words, recirculation zone in yours.
This assertion is backed up by you (and to be honest with you, I can't
believe I'm arguing with someone from M.I.T.). This means that the at
the speed of 150mph, the force of the recirculation zone alone equals the
mechanical drag on the bike and rider. Why then would the rider not add
his 1/3 horsepower to the equation to further raise the speed of the
bike? It seems another 20 or 30mph would be easily possible... just add
a little more gearing, top speed goes up, that entry in the Guinness book
of records gets a little more impressive.
This reminds me of a story I read in a book about sports science. An
engineer writes a paper with equations that prove that if someone drinks
scotch, the alcohol lowers body temperature more than the amount of the
calories in the scotch, forcing the body to use fat stores to maintain
body temperature. In theory someone could sit around drinking scotch and
water all day and lose weight like crazy. In an addendum to the paper,
he wrote, "I tried this and it didn't work."
Ken Ferschweiler
Ted and Jennifer Nichols-Payne (ank...@flash.net) wrote:
: Ken Ferschweiler wrote:
: >
: > And given that power to overcome air drag is roughly proportional to
: > v^3, do you really think you can put out 27-37 times as much power with
: > your legs as with your arms?
: Jesus. Hell, I'm an ex-disc jockey, not a science professor, so I
: probably am out of my league in this debate... I mean, I don't even know
: if I spelled 'professor' right.
: Still, life isn't an equation, and while I understand that the
: aerodynamics of an object at 50mph are much different than that of an
: object at 150mph, I stand by my original assertion... if you give me a
: gear that will spin a wheel at 150mph at a pedaling cadence of 100 or so,
: make that wheel spin freely off the ground, I'll get that wheel to 150.
Life isn't an equation, but equations do a pretty good job of describing
things like how much power it takes to spin a wheel.
: And so will you.
You can do what you want. I've ridden rollers enough to be pretty sure
I couldn't get a pair of wheels up to that speed, and I have no reason
to believe I could get a single wheel up there.
Ken Ferschweiler
: >
: > In article <332E2B...@flash.net>, Ted Nichols-Payne <ank...@flash.net> writes:
: > |> That's a load of crap.
: >
: > No, Jobst is correct.
: No, he's not. So there. (Okay, so I'm spending a lot of time with my 3
: year old daughter, I'm picking up some bad habits)
Yes, he is. Nyah, nyah, nyah.
: > What does the weight of the man+bike have to do with the aerodynamics?
: It takes a lot more force to move a man than it does to move a piece of
: paper. Just trying to point out we're not talking about a small,
: lightweight object being swept along...
I think we should be dealing with Newtonian as opposed to Aristotelian
physics here :-).
: 30mph wind delivers several horsepower?
: Just so I get this right - the car's velocity is 150mph, the bike/rider
: velocity is 150mph, the air in the recirculation zone is approx. 180mph.
: The airspeed relative to bike/rider is -30mph, a 30mph tailwind. Just
: want to make it perfectly clear that we're talking about 30mph, and
: that's giving bike/rider "at least several horsepower". So, if I go
: outside on a windy day, gusts of up to 30mph, why aren't I swept off my
: feet? If you ride your bike into a 15mph wind and your speed is 15mph,
: do you have several horsepower of force working against you and your
: measly 1/3 horsepower?
No, because you're not going 150mph. Power = force X speed. That 30mph
tailwind at 150 mph gives you 10 times as much power as you would expend
riding at 15mph into your 15mph headwind.
: This aerodynamic theory may work for you in the
: lab, but it doesn't work in the real world.
Sorry, but it really does work. You have to understand the theory
correctly first, though.
: Let's say the theory is correct, and we go back to Jobst's original
: assertion, that John Howard could have coasted at 150mph, propelled along
: by the 'windscreen eddies' in his words, recirculation zone in yours.
: This assertion is backed up by you (and to be honest with you, I can't
: believe I'm arguing with someone from M.I.T.). This means that the at
: the speed of 150mph, the force of the recirculation zone alone equals the
: mechanical drag on the bike and rider. Why then would the rider not add
: his 1/3 horsepower to the equation to further raise the speed of the
: bike?
Umm ... because there's a car a few inches in front of him that he'd
rather not run into?
: This reminds me of a story I read in a book about sports science. An
: engineer writes a paper with equations that prove that if someone drinks
: scotch, the alcohol lowers body temperature more than the amount of the
: calories in the scotch, forcing the body to use fat stores to maintain
: body temperature. In theory someone could sit around drinking scotch and
: water all day and lose weight like crazy. In an addendum to the paper,
: he wrote, "I tried this and it didn't work."
This is a variation of an old trivia question (that has shown up on a
few exams in introductory thermodynamics courses) which hinges on
whether the subject knows that food values are expressed in
kilocalories, but referred to as Calories. I would be extremely
surprised if any engineer had ever been naive enough to write such a
paper; and as support for your arguments, it's a pretty weak strawman.
Thomas H. Kunich
In article <5gncd0$a...@senator-bedfellow.MIT.EDU>,
Mark Drela <dr...@athena.mit.edu> wrote:
>|> Jobst Brandt wrote:
>|> > I don't think I said that right. The rider cannot have any affect on
>|> > the speed of the bicycle except to use the brakes. The pedaling is
>|> > there only for appearances. John Howard was towed up to a speed at
>|> > which the windscreen eddies became large enough to propel him. The
>|> > fixed gear was used only to make his feet go around.
>The "dead-zone" behind a well-shaped windscreen is usually called a
>"recirculation zone" in aero jargon --- for good reason. This zone
>can have a forward velocity (relative to the car) of up to 20% or so
>of the vehicle speed. So at 150 mph, Howard felt a ~30 mph tailwind,
>whose negative drag delivered at least several horsepower to him.
>Any pedaling effort of significant duration would have been puny
>by comparison.
I have a real problem with this. While I find myself seduced by
Jobst ideas, I have never seen this powerful recirculation to
actually be the case. Are we to believe that the durnie racing
in Europe wouldn't have found a way to use this idea?
I wish that John Howard would simply be asked by someone who knows
him. That would settle a lot of questions.
Ted and Jennifer Nichols-Payne
Ken Ferschweiler wrote:
>
> : >
> : > No, Jobst is correct.
>
> : No, he's not. So there. (Okay, so I'm spending a lot of time with my 3
> : year old daughter, I'm picking up some bad habits)
>
> : > What does the weight of the man+bike have to do with the aerodynamics?
>
> : It takes a lot more force to move a man than it does to move a piece of
> : paper. Just trying to point out we're not talking about a small,
> : lightweight object being swept along...
>
> I think we should be dealing with Newtonian as opposed to Aristotelian
> physics here :-).
LOL, part two. My point, again, is that it is easier for a piece of paper is swept
along by the atmosphere much easier than a human body. Less mass to put into motion,
higher drag coefficient, easier to be swept along. I think Newton and Aristotle would
actually agree on this point. Now, if you were to drop my 22lb Raleigh 753 and my 30lb
Stumpjumper off the leaning tower of Pisa at the same time, it would make me cry.
> : 30mph wind delivers several horsepower?
>
> : Just so I get this right - the car's velocity is 150mph, the bike/rider
> : velocity is 150mph, the air in the recirculation zone is approx. 180mph.
> : The airspeed relative to bike/rider is -30mph, a 30mph tailwind. Just
> : want to make it perfectly clear that we're talking about 30mph, and
> : that's giving bike/rider "at least several horsepower". So, if I go
> : outside on a windy day, gusts of up to 30mph, why aren't I swept off my
> : feet? If you ride your bike into a 15mph wind and your speed is 15mph,
> : do you have several horsepower of force working against you and your
> : measly 1/3 horsepower?
>
> No, because you're not going 150mph. Power = force X speed. That 30mph
> tailwind at 150 mph gives you 10 times as much power as you would expend
> riding at 15mph into your 15mph headwind.
>
> : This aerodynamic theory may work for you in the
> : lab, but it doesn't work in the real world.
>
> Sorry, but it really does work. You have to understand the theory
> correctly first, though.
I have no answer for this. I concede defeat in this debate. I'm still not convinced
you're right, but I can't back up my beliefs with any kind of scientific fact.
> : Let's say the theory is correct, and we go back to Jobst's original
> : assertion, that John Howard could have coasted at 150mph, propelled along
> : by the 'windscreen eddies' in his words, recirculation zone in yours.
> : This assertion is backed up by you (and to be honest with you, I can't
> : believe I'm arguing with someone from M.I.T.). This means that the at
> : the speed of 150mph, the force of the recirculation zone alone equals the
> : mechanical drag on the bike and rider. Why then would the rider not add
> : his 1/3 horsepower to the equation to further raise the speed of the
> : bike?
>
> Umm ... because there's a car a few inches in front of him that he'd
> rather not run into?
Umm... couldn't they get a faster car? While I understand it would be hard to pull that
air dam through the air at 150mph... well, okay, maybe they couldn't get a faster car.
Hell, by brain hurts.
> : This reminds me of a story I read in a book about sports science. An
> : engineer writes a paper with equations that prove that if someone drinks
> : scotch, the alcohol lowers body temperature more than the amount of the
> : calories in the scotch, forcing the body to use fat stores to maintain
> : body temperature. In theory someone could sit around drinking scotch and
> : water all day and lose weight like crazy. In an addendum to the paper,
> : he wrote, "I tried this and it didn't work."
>
> This is a variation of an old trivia question (that has shown up on a
> few exams in introductory thermodynamics courses) which hinges on
> whether the subject knows that food values are expressed in
> kilocalories, but referred to as Calories. I would be extremely
> surprised if any engineer had ever been naive enough to write such a
> paper; and as support for your arguments, it's a pretty weak strawman.
Well, I never really intended it as support for my arguments as much as illustrate that
you can explain a lot of things away using all sorts of scientific theories and physics
books - things that the real world and life experience prove.
Another story in the same vein... in the book "The Right Stuff," there's an episode
where Chuck Yeager and Neil Armstrong are supposed to go land on some dry lake bed
somewhere, I forget why. Yeager says forget it, this time of year it'll be too muddy,
the landing gear will get all fouled up and we won't be able to take off again.
Armstrong replies that the lake bed should not be muddy, quoting recent weather factors.
Yeager says I've been flying over these lakes for 20 years, I know that it's muddy.
Armstrong stands by his assertion, so they fly to the lake. You know the punch line,
they land, the gear gets fouled up with mud, they can't get out. It's been a while
since I read the book, so I forget how they get out, and I forget why Yeager went with
Armstrong when he knew they would get stuck... hell, now I'm rambling.
Anyhow, you win, I bow before your superior intellect. If you're ever in Dallas, we can
play guitar together so I can prove that I'm the better man, once and for all. :)
Joseph Riel
Jobst Brandt (jbr...@hpl.hp.com) wrote:
: You can do some calculations. Assuming that you can put out 1/3
: horsepower, use the speed of 150 mph to see what that converts to in
: thrust. Spreading 1/3 HP out at 150 mph leaves insufficient thrust to
: turn just the wheels in air, if they are smooth disks.
1/3 HP is 200W which is rather low for a trained athlete in a short duration
event. I've computed that the spoke drag of a 700mm 32 spoke wheel spinning
in still air with "velocity" of 150mph is about 700W (the error could
be rather large, consider this a ballpark figure). A disk wheel should
have significantly less drag, so it is conceivable that someone could spin
two such wheels up to 150mph.
Joe Riel
--
j...@sparc.sandieogoca.ncr.com
Thomas H. Kunich
In article <333064...@flash.net>,
Ted and Jennifer Nichols-Payne <ank...@flash.net> wrote:
>LOL, part two. My point, again, is that it is easier for a piece of paper is swept
>along by the atmosphere much easier than a human body.
For what it's worth. This 'push by recirculation' argument was used
when Mile a Minute Murphy set his record. They had already thought
of that argument and had dropped a hankerchef in the dead zone and
it dropped straight down until well behind the bike/man.
(Sorry I lost this attribution)
>> No, because you're not going 150mph. Power = force X speed. That 30mph
>> tailwind at 150 mph gives you 10 times as much power as you would expend
>> riding at 15mph into your 15mph headwind.
This is a great one -- some 30 mph tailwinds are more equal than other
30 mph tailwinds. Real science here. Regardless of what the originator
does to the argument do not change the subject. A 30 mph tailwind is
a 30 mph tailwind.
I agree that it's possible to get a significant boost through recirculating
air currents in the dead zone behind such a vehicle. But I disagree
that it is possible to get 100% of the power that way.
As I recall, in the biggest incarnation of this argument a real live
aerodynamist put it through the computer and got the break-even point
at 350 mph.
Mark Drela
A "barn door" with bent edges, like the one Howard drafted,
has a larger drag coefficient and hence a larger backdraft than
a flat-backed vehicle like a bus. Also, drafting very close
to a bus at 30 mph might get you a 3-5 mph backdraft at most.
The resulting propulsion would not be noticable.
|> I wish that John Howard would simply be asked by someone who knows
|> him. That would settle a lot of questions.
Yeah, that would be good. But I wouldn't hold my breath.
I doubt he would admit to having used the brakes on his speed run.
Mike Garrison
Thomas H. Kunich wrote:
>
> In article <333064...@flash.net>,
> Ted and Jennifer Nichols-Payne <ank...@flash.net> wrote:
>
> >along by the atmosphere much easier than a human body.
>
> when Mile a Minute Murphy set his record. They had already thought
> of that argument and had dropped a hankerchef in the dead zone and
> it dropped straight down until well behind the bike/man.
So what? Nobody said there was any lift (aerodynamic force acting against gravity) in
this setup, just thrust.
>
> (Sorry I lost this attribution)
> >> No, because you're not going 150mph. Power = force X speed. That 30mph
> >> tailwind at 150 mph gives you 10 times as much power as you would expend
> >> riding at 15mph into your 15mph headwind.
>
> This is a great one -- some 30 mph tailwinds are more equal than other
> 30 mph tailwinds. Real science here. Regardless of what the originator
Unfortunately for your argument, it IS real science. The point was that the force is
proportional to the tailwind. But the power is the force*speed. Thus, even though a
thirty mile tailwind produces the same force at any speed, it produces 10 times as
much power at 150 as it does at 15.
> As I recall, in the biggest incarnation of this argument a real live
> aerodynamist put it through the computer and got the break-even point
> at 350 mph.
Hey, I'm a "real live aerodynamicist." Mark Drela (earlier in this thread) is an
internationally known areodynamicist. What do you do for a living?
Ken Ferschweiler
Thomas H. Kunich (to...@netcom.com) wrote:
: (Sorry I lost this attribution)
That would be me.
: >> No, because you're not going 150mph. Power = force X speed. That 30mph
: >> tailwind at 150 mph gives you 10 times as much power as you would expend
: >> riding at 15mph into your 15mph headwind.
: This is a great one -- some 30 mph tailwinds are more equal than other
: 30 mph tailwinds. Real science here. Regardless of what the originator
: does to the argument do not change the subject. A 30 mph tailwind is
: a 30 mph tailwind.
Well, it may be, as you say, "a great one", but that doesn't change the
fact that what I stated is correct. Sorry if you don't understand "real
science", but there's not much I can do about that.
Jobst Brandt
Zach Kaplan writes:
>>> One of the major tire manufacturers (Michelin??) makes a tire
>>> specifically for the "Sun" racer, solar powered vehicles. They are
>>> used by almost all the teams as bicycle tires don't stand up to the
>>> heat/sustained speed that the vehicles are racing at. You might try
>>> one of the HPV newsgroups for more info.
>> They also use the Avocet-Goodyear tire that is more widely used by
>> such vehicles. By the way, where is all the heat coming from to which
>> you refer? If there were measurable heat, the whole exercise would be
>> moot because these vehicles have so little power they could not afford
>> to use tires that generate perceptible heat.
> I tried to order some Avocet Freestyle 47-406mm (20 x 1.75") tyres a
> couple months ago and was told by the Avocet rep they are no longer
> in production and no longer available. Too bad, this was one of my
> favourite wide 406mm tyres. I understand Ritchey is developing a
> similar width 406mm version of the Tom Slick.
And I just checked with Avocet and these tires are again in stock.
Jobst Brandt <jbr...@hpl.hp.com>
Jobst Brandt
Stuart Paynter writes:
>> They also use the Avocet-Goodyear tire that is more widely used by
>> such vehicles. By the way, where is all the heat coming from to which
>> you refer? If there were measurable heat, the whole exercise would be
>> moot because these vehicles have so little power they could not afford
>> to use tires that generate perceptible heat.
> I was referring to the fact that these are "solar" vehicles and the
> races are nice sunny warm locations like across the Australian
> desert, or southern Cal. Given that the air temperatures tend to be
> in the 35-40C range, the heat I am talking about would be coming
> from the asphalt surface, not friction from the tires. You know,
> black surface, hot sun, don't try and walk across it in your bare
> feet kind of hot.
Rolling resistance becomes lower when tires get warmer so that
shouldn't be a problem. These tire casings don't lose on strength in
that temperature range either.
> Heat is just one of the factors involved in the breakdown of a
> bicycle tire in the sun-racer application. They just don't stand up
> to the application. Consequently, Avocet-Goodyear, as you
> mentioned, have developed a tire that more closely resembles a
> motorcycle tire specifically for this vehicle.
The Avocet-Goodyear tires are again in stock at Avocet. I just checked.
Jobst Brandt <jbr...@hpl.hp.com>
Jeffrey L. Bell
Did he use a quick release.
-Jeff Bell
Jobst Brandt
Tom Kunich writes:
> I agree that it's possible to get a significant boost through
> recirculating air currents in the dead zone behind such a vehicle.
> But I disagree that it is possible to get 100% of the power that
> way.
Why? A 30mph tailwind at 150 mph is a 180mph wind with respect to the
road. It all depends on what you use as reference.
The rider has a power reference of the road, so to achieve one pound
forward thrust at 150mph (220fps) he must exert 220 ft-lbs/sec or 0.4 HP.
It takes more than that just to spin the wheels at that speed.
> As I recall, in the biggest incarnation of this argument a real live
> aerodynamicist put it through the computer and got the break-even
> point at 350 mph.
That's pure rumor.
Jobst Brandt <jbr...@hpl.hp.com>
Jobst Brandt
Ted Nichols-Payne writes:
> You think there's some way to design an air dam on the back of a
> vehicle to direct the turbulence in such a way that it will actually
> provide thrust for a bicycle and rider? At 150mph? We're not
> talking about a piece of paper here, we're talking about 150-200 lbs
> of man and bike. The idea is for the pace vehicle to provide a
> 'dead zone,' a pocket of air behind it for the cyclist to ride in,
> so the rider only has to overcome friction from the bike (which can
> be considerable at 150mph)... in practice, there is still wind
> resistance, as no air dam will provide _total_ isolation from the
> atmosphere.
You think there is a way to create dead air from a 150mph wind in the
course of an airdam. I see you have never ridden in a convertible car
with the top down. The wind forces that you experience there scale
with speed. That strong forward wind speed is obtainable is obvious
to most observers, but what is less obvious is that propelling a
bicycle's wheels to 150mph is beyond the power of a bicyclist from the
outset. This is why the bicyclist (John Howard) was towed to near
maximum speed where the wind forces are great enough to propel him.
The rider has no ability to accelerate anyway, let alone maintain such
wheel speeds.
> For the sake of argument, let's say the rider slipped back, out of
> the relative calm provided directly behind the air dam, and into the
> "eddies" to gain some type of thrust from them in an attempt to be
> pulled along like debris behind a semi on the highway.
Slipping out of the designed spot is the end of the attempt. You
cannot ride in that vortex. Letting go and dropping out of the slip
stream is highly dangerous and usually leads to a crash.
> What do you think the turbulence at this point is going to be like?
> Anyone that owns a motorcyle will tell you - that wind beats you up.
> Tailing a semi at 60mph on my Honda has taught me to stay back, lest
> I want to find myself in the next lane unexpectedly...
And sitting on moving van with minimal ground clearance has been done
by bicyclists, and the sweet spot is close to the truck as you can get.
> And as to someone not being able to generate the horsepower to
> simply spin a bicycle wheel at 150mph... considering I can spin my
> 36 spoke rear wheel at approx 45-50mph _by hand_ (on the rack, wheel
> of the ground, top gear, spin it as fast as you can with one hand),
> I think that given the proper gearing, simply spinning a wheel at
> that speed (even a heavier weight wheel) is definitely within the
> abilities of even an average bikie.
You don;t know what you are talking about.
> Sorry, Jobst, this one doesn't fly.
You are speaking about your own claims, no doubt.
Jobst Brandt <jbr...@hpl.hp.com>
Thomas H. Kunich
In article <5guf9s$p...@hplms2.hpl.hp.com>,
Jobst Brandt <jbr...@hpl.hp.com> wrote:
>
>Why? A 30mph tailwind at 150 mph is a 180mph wind with respect to the
>road. It all depends on what you use as reference.
>
>The rider has a power reference of the road, so to achieve one pound
>forward thrust at 150mph (220fps) he must exert 220 ft-lbs/sec or 0.4 HP.
>It takes more than that just to spin the wheels at that speed.
Look, all you have to do is go out on a smooth straight road when
there is a tailwind blowing. I have tried this in winds up to
40 mph.
Ride up to about 20 mph and coast -- invariably I've come to a complete
stop without peddaling.
Jobst Brandt
Tom Kunich writes:
> Look, all you have to do is go out on a smooth straight road when
> there is a tailwind blowing. I have tried this in winds up to 40
> mph.
> Ride up to about 20 mph and coast -- invariably I've come to a
> complete stop without peddaling.
I think you mis-estimated the wind. The power that transfers to a
riders in a 40 mph wind is the same as the power it takes you to ride
40 mph minus rolling resistance. First off, there are seldom 40 mph
surface winds that blow consistently and if your bike rolls to a stop,
then you had better get an overhaul, because your brakes are dragging
or you have Mr Tuffys that you didn't know about.
Jobst Brandt <jbr...@hpl.hp.com>
Mr D.M. Whittle
> >
> spin a bicycle wheel at 150mph... considering I can spin my 36 spoke rear
> wheel at approx 45-50mph _by hand_ (on the rack, wheel of the ground, top
> gear, spin it as fast as you can with one hand), I think that given the
> proper gearing, simply spinning a wheel at that speed (even a heavier
> weight wheel) is definitely within the abilities of even an average
> bikie.
>
SOme guy in the UK (forget his name) has set the speed record on rollers at
something like 180mph, which suggest jobst is a trifle less than correct for
once......
dave
Thomas H. Kunich
In article <E7K0A...@liverpool.ac.uk>,
Mr D.M. Whittle <dwh...@liverpool.ac.uk> wrote:
>SOme guy in the UK (forget his name) has set the speed record on rollers at
>something like 180mph, which suggest jobst is a trifle less than correct for
>once......
I thought that I had heard this also. Then I tried to ride just 60 mph
on rollers and guess what? I couldn't. You have the rolling resistance
of the bike, the wind resistance of the spokes/wheels and the bearing
friction of the rollers.
And I haven't been able to get any information on this guy who was
supposed to be so fast.
Jobst Brandt
Mr D.M. Whittle writes:
>> spin a bicycle wheel at 150mph... considering I can spin my 36 spoke rear
>> wheel at approx 45-50mph _by hand_ (on the rack, wheel of the ground, top
>> gear, spin it as fast as you can with one hand), I think that given the
>> proper gearing, simply spinning a wheel at that speed (even a heavier
>> weight wheel) is definitely within the abilities of even an average
>> bikie.
>>
>> Sorry, Jobst, this one doesn't fly.
> Some guy in the UK (forget his name) has set the speed record on
> rollers at something like 180mph, which suggest Jobst is a trifle
> less than correct for once...
Oh how cute: " a trifle less than correct for once"
Yes, this and many other "I can't recall exactly where" facts are used
to support all sorts of claims. I am sure that I can design a set of
rollers and a small wheeled bicycle that could develop such a surface
speed, but it wouldn't look much like bicycle wheels. Had you seen
John Howard's bicycle, with its large double reduction chainwheels,
one mounted on a shaft above and behind the cranks, you would quickly
see that to spin not only the back wheel, but also the front wheel at
150 mph, is more than a rider can do.
The 24" wheels Howard used had to turn at 2100 rpm to reach 150 mph
and required a 20:1 ratio to get the pedals to a reasonable cadence.
For most technically inclined riders with some experience on a
bicycle, no more need be said. It's a substantial wind-trainer.
Jobst Brandt <jbr...@hpl.hp.com>
Dave Blake
>Mr D.M. Whittle writes:
>> Some guy in the UK (forget his name) has set the speed record on
>> rollers at something like 180mph, which suggest Jobst is a trifle
>> less than correct for once...
150 MPH = 3 miles/minute = 15840 feet/minute =
190080 inches/minute.
Standard rollout = PI * 27" (roughly) * gear =
84.8 times gear = 84.8 * (60/11) = 462.6 inches.
60x11 is a pretty big gear.
So, if someone were to hit 150 MPH on rollers,
he would be spinning a 60x11 at 411 RPM. That
only sounds off by a factor of 2 ie: maybe
maybe maybe 90 MPH is possible. But 180 MPH
on a bike with very large gearing is not
possible. And that is on rollers ignoring the
wind resistance of the wheels, which I doubt
is small enough to ignore.
--
Dave Blake
dbl...@phy.ucsf.edu
http://www.keck.ucsf.edu/~dblake/
Ken Ferschweiler
Dave Blake (dbl...@phy.ucsf.eduDELETETHISPART) wrote:
: So, if someone were to hit 150 MPH on rollers,
: he would be spinning a 60x11 at 411 RPM.
Howard's bike used a double reduction gear to acheive a very
high gear ratio. You can see a picture of the drivetrain
at http://www.internetnow.com/hujsak/speedbik.html.
djw
> This reminds me of a story I read in a book about sports science. An
> engineer writes a paper with equations that prove that if someone drinks
> scotch, the alcohol lowers body temperature more than the amount of the
> calories in the scotch, forcing the body to use fat stores to maintain
> body temperature. In theory someone could sit around drinking scotch and
> water all day and lose weight like crazy. In an addendum to the paper,
> he wrote, "I tried this and it didn't work."
No, it has to be ice cubes, eat ice cubes...
Hey, it's too cold and wet to ride, so instead I digress...
mmm ...scotch...
Don Mackie
In article <5hegsp$1k...@itssrv1.ucsf.edu>,
dbl...@phy.ucsf.eduDELETETHISPART (Dave Blake) wrote:
> So, if someone were to hit 150 MPH on rollers,
> he would be spinning a 60x11 at 411 RPM.
The Guinness Book of records I had as a child (>20 years ago) had a photo
of a Belgian drafting a motorbike. His chainwheel was huge, almost the
same diameter as his crank circle, easily 120+teeth.
--
Don at his place
David G.
Thomas H. Kunich wrote:
>
> In article <E7K0A...@liverpool.ac.uk>,
> Mr D.M. Whittle <dwh...@liverpool.ac.uk> wrote:
>
> >something like 180mph, which suggest jobst is a trifle less than correct for
> >once......
>
> I thought that I had heard this also. Then I tried to ride just 60 mph
> on rollers and guess what? I couldn't. You have the rolling resistance
> of the bike, the wind resistance of the spokes/wheels and the bearing
> friction of the rollers.
>
> And I haven't been able to get any information on this guy who was
> supposed to be so fast.
It's not a UCI event so it's not clear what would be an "official"
record but the 'Guiness Book of Records' lists it as 153+ in 1989 in the
USA.
Perhaps Thomas should spend less time on the keyboard and more time on
the bike !
David.
Steve
>SOme guy in the UK (forget his name) has set the speed record on rollers at
>something like 180mph, which suggest jobst is a trifle less than correct for
>once......
>
Yes it is true his name is Dave Le Grys.
Mr D.M. Whittle
In article <tomkE7o...@netcom.com>, to...@netcom.com (Thomas H. Kunich) writes:
> In article <E7K0A...@liverpool.ac.uk>,
> Mr D.M. Whittle <dwh...@liverpool.ac.uk> wrote:
>
> >something like 180mph, which suggest jobst is a trifle less than correct for
> >once......
>
> on rollers and guess what? I couldn't. You have the rolling resistance
> of the bike, the wind resistance of the spokes/wheels and the bearing
> friction of the rollers.
>
> And I haven't been able to get any information on this guy who was
> supposed to be so fast.
>
>
he used disc wheels to reduce drag.
dave
Mr D.M. Whittle
In article <5heej4$7...@hplms2.hpl.hp.com>, jbr...@hpl.hp.com (Jobst Brandt) writes:
> Mr D.M. Whittle writes:
>
>
> > rollers at something like 180mph, which suggest Jobst is a trifle
> > less than correct for once...
>
>
> Yes, this and many other "I can't recall exactly where" facts are used
> to support all sorts of claims. I am sure that I can design a set of
> rollers and a small wheeled bicycle that could develop such a surface
> speed, but it wouldn't look much like bicycle wheels. Had you seen
> John Howard's bicycle, with its large double reduction chainwheels,
> one mounted on a shaft above and behind the cranks, you would quickly
> see that to spin not only the back wheel, but also the front wheel at
> 150 mph, is more than a rider can do.
>
> The 24" wheels Howard used had to turn at 2100 rpm to reach 150 mph
> and required a 20:1 ratio to get the pedals to a reasonable cadence.
> For most technically inclined riders with some experience on a
> bicycle, no more need be said. It's a substantial wind-trainer.
>
> Jobst Brandt <jbr...@hpl.hp.com>
Well some of us have better things to do than memorise every detail of every
article we read or see. The British guy in question was nationally televised
doing it, the chain ring was almost as big as the wheels (which were of a
standard size), and he was running on standard rollers. And hes' in the
Guiness book of records for it. So if a reference is so important then there
you are. Or was the entire television audience the subject of some government
experiment into mass hallucinations? Better call Scully, eh jobst?
dave
Mark Drela
Yeah, but for a 1.8 mm, 32-spoke wheel *rolling* at 150 mph, I calculate
about 3000 Watts just for the spokes.
A rolling wheel always absorbs WAY more power than when it is spinning
at the same speed on rollers -- this is true for both spoke and disk wheels.
The stationary wheel sees the full 150 mph speed only at the tire, while
the moving wheel sees 150 mph at the center and 0-300 mph at the tire.
Aero drag power scales like V^3 and the 300 mph peak speed dominates.
The earlier posting stating that 180 mph "has been done" on rollers
is not really pertinent to the case of a moving bike.
Tom Lawrence
A rolling wheel always absorbs WAY more power than when it is spinning
at the same speed on rollers -- this is true for both spoke and disk wheels.
The stationary wheel sees the full 150 mph speed only at the tire, while
the moving wheel sees 150 mph at the center and 0-300 mph at the tire.
Aero drag power scales like V^3 and the 300 mph peak speed dominates.
The earlier posting stating that 180 mph "has been done" on rollers
is not really pertinent to the case of a moving bike.
I'm not pronouncing any opinion one way or another on whether or not
this bike can actually be ridden, but I do want to point out that the
"150 mph" bike is supposedly ridden in dead air drafting behind an air
dam, so it is in fact equivalent to riding rollers.
Jobst Brandt
Mr Dave Whittle writes:
> Well some of us have better things to do than memorise every detail
> of every article we read or see. The British guy in question was
> nationally televised doing it, the chain ring was almost as big as
> the wheels (which were of a standard size), and he was running on
> standard rollers. And he's' in the Guiness book of records for it.
> So if a reference is so important then there you are. Or was the
> entire television audience the subject of some government experiment
> into mass hallucinations? Better call Scully, eh Jobst?
Why so petulant? I didn't say such a record could not be set. What I
said was that John Howard's bike could not be pedaled at 150mph, at
least not for any length of time that one could set a speed record
over a course. His was a bicycle with exposed spokes and fat tires,
not exactly a roller 180mph setup. His bicycle was towed up to more
than 100 mph at which time the wind force at his back enabled him to
release the tow bar and coast through the traps. What makes you want
to believe that one could propel a bicycle at those speeds without
motor power even in dead air?
Just acceleration considerations make clear that from 120 to 150 mph
is impossible in the length of the speed strip if all his energy went
only to acceleration.
Jobst Brandt <jbr...@hpl.hp.com>
Jobst Brandt
Mark Drela writes:
> A rolling wheel always absorbs WAY more power than when it is
> spinning at the same speed on rollers -- this is true for both spoke
> and disk wheels. The stationary wheel sees the full 150 mph speed
> only at the tire, while the moving wheel sees 150 mph at the center
> and 0-300 mph at the tire. Aero drag power scales like V^3 and the
> 300 mph peak speed dominates.
Except that these wheels were not exposed to air at ground speed.
They were in effect spinning in place in a turbulent backdraft.
> The earlier posting stating that 180 mph "has been done" on rollers
> is not really pertinent to the case of a moving bike.
That too.
Jobst Brandt <jbr...@hpl.hp.com>
Thomas H. Kunich
In article <5ib8if$l...@hplms2.hpl.hp.com>,
Jobst Brandt <jbr...@hpl.hp.com> wrote:
>Mark Drela writes:
>
>> A rolling wheel always absorbs WAY more power than when it is
>> spinning at the same speed on rollers -- this is true for both spoke
>> and disk wheels. The stationary wheel sees the full 150 mph speed
>> only at the tire, while the moving wheel sees 150 mph at the center
>> and 0-300 mph at the tire. Aero drag power scales like V^3 and the
>> 300 mph peak speed dominates.
>
>Except that these wheels were not exposed to air at ground speed.
>They were in effect spinning in place in a turbulent backdraft.
BINGO, you just struck the note I needed to believe your claims
about 150 mph bicycles.
i.e. There is still rolling resistance and there is no way to get
around that. I have been somewhat dismayed by knowing that a
trailing wind current like that on the record attempt wasn't
nearly enough to push the rider as you claim. Particularly when
I also knew that it is highly unlikely that anyone could turn the
spokes of that bike through the air resistance at 150 mph. So
you just dropped the final piece into place.
As I see it. The recirculating wind overcomes the wind resistance
of the spokes. There may be some small additional push on the form
of the rider but I find it difficult to believe that it is more than
the rolling resistance of those tires. So it would appear to me
that the record attempt was merely someone overcoming rolling
resistance at 150 mph -- no small feat, mind you, but certainly
not a 150 mph record in my book.
Remember that Mile-a-minute Murphy ran his 60 mph behind a train
and that as proof of the _lack_ of recirculating air currents they
dropped a hankerchief and it fell straight down in the area that
the rider was situated. It is now plain that that wasn't the case
with the 150 mph record and we should probably no longer pay
any attention to any motorpaced records.
Jobst Brandt
Tom Kunich writes:
> As I see it. The recirculating wind overcomes the wind resistance
> of the spokes. There may be some small additional push on the form
> of the rider but I find it difficult to believe that it is more than
> the rolling resistance of those tires. So it would appear to me
> that the record attempt was merely someone overcoming rolling
> resistance at 150 mph -- no small feat, mind you, but certainly
> not a 150 mph record in my book.
No, you still missed the part that at max speed the brake was the most
important control on the bike and that it was used to keep the front
wheel at the position that puts the rider in the "sweet spot" of the
windscreen. As I said, the bike was towed to over 100mph, I don;t
recall how fast, but there being no manpower sufficient for
acceleration to 150mph let alone propel the bicycle, the recirculating
air furnished the thrust.
Apparently you haven't ridden in a convertible car, top down, lately
or you would be aware off the strong backdraft that occurs even though
the manufacturer is interested in not having it there. Some recent
sports cars have rear wind protectors that come up behind the
passengers and prevent blowing off hats and messing hair. It doesn't
work all that well just the same.
> Remember that Mile-a-minute Murphy ran his 60 mph behind a train
> and that as proof of the _lack_ of recirculating air currents they
> dropped a handkerchief and it fell straight down in the area that
> the rider was situated. It is now plain that that wasn't the case
> with the 150 mph record and we should probably no longer pay
> any attention to any motorpaced records.
There is a difference. There is no doubt that riders can ride a
treadmill at 60mph in dead air. The enclosure used for that stunt was
also a deep shell with walls that went beyond the rider.
Jobst Brandt <jbr...@hpl.hp.com>
Mr D.M. Whittle
In article <5i1r13$n...@hplms2.hpl.hp.com>, jbr...@hpl.hp.com (Jobst Brandt) writes:
> Mr Dave Whittle writes:
>
> > Well some of us have better things to do than memorise every detail
> > of every article we read or see. The British guy in question was
> > nationally televised doing it, the chain ring was almost as big as
> > the wheels (which were of a standard size), and he was running on
> > standard rollers. And he's' in the Guiness book of records for it.
> > So if a reference is so important then there you are. Or was the
> > entire television audience the subject of some government experiment
> > into mass hallucinations? Better call Scully, eh Jobst?
>
> Why so petulant? I didn't say such a record could not be set. What I
> said was that John Howard's bike could not be pedaled at 150mph, at
> least not for any length of time that one could set a speed record
> over a course. His was a bicycle with exposed spokes and fat tires,
> not exactly a roller 180mph setup. His bicycle was towed up to more
> than 100 mph at which time the wind force at his back enabled him to
> release the tow bar and coast through the traps. What makes you want
> to believe that one could propel a bicycle at those speeds without
> motor power even in dead air?
provide a ref it must have been seen by hundreds of thousands of people
on T.V in the UK. And I accept that the bikes were different. Apparently
the brit that did it on the roller was also mechanically accelerated to
~100mph, as he couldnt physically turn the pedals below that speed.
I think both the roller and and paced records are meaningless, but that
doesnt mean theyre impossible. They just need a bit of,well, cheating, thats
all.
>
> Just acceleration considerations make clear that from 120 to 150 mph
> is impossible in the length of the speed strip if all his energy went
> only to acceleration.
>
> Jobst Brandt <jbr...@hpl.hp.com>
dave
Al Williams
In article <5ijce4$o...@hplms2.hpl.hp.com> Jobst Brandt,
jbr...@hpl.hp.com writes:
(snip)
>No, you still missed the part that at max speed the brake was
the most
>important control on the bike and that it was used to keep
the front
>wheel at the position that puts the rider in the "sweet spot"
of the
>windscreen. As I said, the bike was towed to over 100mph, I
don;t
>recall how fast, but there being no manpower sufficient for
>acceleration to 150mph let alone propel the bicycle, the
recirculating
>air furnished the thrust.
>
In the 70's I used to commute on US 30 in eastern Pa., and I
would draft behind 18-wheelers when available. (There weren't
any good speedometers then, so I don't know how fast we would
go.) When following full-height vans, once we would get going
well, there was an area where air speed would be negative.
That is, sweat drops would blow forward, between the wheels of
the truck. This wasn't true when following dump trucks, flat
beds, or car carriers, in general. I never had to drag my
brakes to avoid running into a truck, but I would occasionally
ride toward the side of the truck, rather than centered behind
it, in order to get a little more drag. It was easier to move
from side to side to manage the drag than to move forward or
back behind the center of the truck.
Al Williams
San Jose CA