Fastest speed on a coker?

On Wed, 3 Sep 2003 13:01:15 -0500, Ken Fuchs
wrote:

To calculate wheel size, one must ride a carefully measured one turn
of
the wheel or several turns / number of turns. Measuring my wheel
without riding resulted in a circumference that was about 2% longer
(2839mm) than measuring when riding (2834mm). Riding appears to
compress the tire slightly, giving a smaller than expected
circumference.

Ken, you've probably made a typo in the numbers or misplaced a decimal
point. The difference between those two rollouts is actually about
0.18%.

There is also unclarity in my mind about the definition of 'speed'. I
can think of two definitions for speed. One is the circumference of the
wheel multiplied by the cadence, I call that tyre speed. The other is
the distance covered per unit of time, I call that road speed. The two
are different for (again) two reasons; for both of these, their effect
is in the same direction:

1. Wobble.
2. Tyre compression.

The first is fundamental, and it is a philosophical question what the
'best' definition of speed would be. The second could be avoided by
measuring the rollout while sitting on the uni. I measured the rollout
of my wheels when unloaded but when I sit on them the tyre compresses
and the effective wheel radius decreases. According to my measurements,
the two effects combined cause a difference on the order of 3%.

Klaas Bil


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Klaas Bil wrote:
*I can think of two definitions for speed. One is the circumference of
the wheel multiplied by the cadence, I call that tyre speed. The other
is the distance covered per unit of time, I call that road speed. The
first is fundamental, and it is a philosophical question what the
'best' definition of speed would be. *

With all due respect....

Philosophy Shmilosophy.

If you're racing your Coker against a car, and when you get to your max
speed and they're still with you they yell their speedometer reading out
the window at you for encouragement, what is the number they're
yelling?

TB

"Putting the "oup" in "newsgroup".....


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tomblackwood wrote:
*Philosophy Shmilosophy.

If you're racing your Coker against a car, and when you get to your
max speed and they're still with you they yell their speedometer
reading out the window at you for encouragement, what is the number
they're yelling?*

Thank you for the example because that refers precisely to my point. A
car has no wheel wobble to speak of - or something is terribly wrong. So
they are yelling your road speed (in my terms). If you have calibrated
your cyclometer on a straight (and loaded) rollout it measures your tyre
speed. The difference is (in my experiments) about 3%. Shmilosophy? You
may call it that but I wouldn't.

Klaas Bil


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On Wed, 3 Sep 2003 13:01:15 -0500, Ken Fuchs
wrote:

To calculate wheel size, one must ride a carefully measured one turn of
the wheel or several turns / number of turns. Measuring my wheel
without riding resulted in a circumference that was about 2% longer
(2839mm) than measuring when riding (2834mm). Riding appears to
compress the tire slightly, giving a smaller than expected
circumference.

(Klaas Bil) wrote:

You've probably made a typo in the numbers or misplaced a decimal
point. The difference between those two rollouts is actually about
0.18%.

Thanks for pointing out that error. The corrected sentence should read:

Measuring my wheel without riding resulted in a circumference that was
about 2% longer (2839mm) than measuring when riding (2789mm). A
difference of 50mm and not 5mm as previously stated.

There is also an unclarity in my mind about the definition of 'speed'.
I can think of two definitions for speed. One is the circumference of
the wheel multiplied by the cadence, I call that tyre speed. The other
is the distance covered per unit of time, I call that road speed. The
two are different for (again) two reasons; for both of these, their
effect is in the same direction:

1. Wobble.
2. Tyre compression.

My measurement didn't take into account wobble. I simply pedaled my
Coker exactly one rotation of the wheel on a straight line, next to a
support like a fence to help keep me straight. Thus, I measured the
wheel circumference with rider weighted tire compression, but definitely
wobble was not accounted for. I'm measuring tire speed with
compression; wobble effects should be included as well.

The first is fundamental, and it is a philosophical question what the
'best' definition of speed would be. The second could be avoided by
measuring the rollout while sitting on the uni. I measured the rollout
of my wheels when unloaded but when I sit on them the tyre compresses
and the effective wheel radius decreases. According to my
measurements, the two effects combined cause a difference on the order
of 3%.

As I measured it, tire compression effectively reduces wheel
circumference by 1.76%. Taking Klass' total reduction of 3% and
subtracting the tire compression of 1.76% would give us a wheel wobble
reduction of 1.24%. However, this 1.24% doesn't mean much, because it
is a composite measurement of two riders, Klass Bil and myself.

Tire compression probably varies with rider weight, tire wear and tire
pressure.

Wheel wobble probably varies with speed, Q factor, rider leg, crank and
pedal mass. (Maybe rider skill can affect it too, but that might
as a side effect actually reduce speed; effort making the wheel wobble
less is not expended in actually making it go faster.)

So to get an accurate wheel circumference, one really should ride a long
accurately measured course in the way one expects to ride. One should
go about the speed one most often expects to go. The Q factor is a
constant for the Coker until the hub is changed. The Wobble mass is a
constant for the Coker and rider until the cranks/pedals are changed or
the rider bulks up (or loses weight in) his legs.

If one gets an accurate wheel rotation count, one can simply divide the
distance by the count to get the effective wheel circumference,
including both wobble and tire compression effects.

Otherwise, one can simply enter one's best guess of the effective wheel
circumference. Ride the measured course and compare the real (measured)
distance to the computer's distance. Compute the difference as a +/-
percentage and adjust the computer's circumference by the same
percentage.

Thank you Klass for your clear comments and insight into the bike
computer calibration problem for unicycles.

Sincerely,

Ken Fuchs

Klaas Bil wrote:
*Shmilosophy? You may call it that but I wouldn't.*


Deal....


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The way speed is usually measured in sports competitions is by timing
something over a measured distance. This is how it's done for runners,
race cars, and bikes. This gives the rider the freedom to zig zag all
they want, or not, as whatever "speed" is contained in those motions
it's irrelevant to getting from A to B.

Onboard cyclometers are good for training and comparison from one ride
to the next, but are not real good for comparing one to another. To do
so accurately, calibration must be very accurate on the part of both
riders. It would (should) not be used in setting speed records, or
racing.

All of that said, there are a few "recognized" existing records out
there. We race 10k fairly regularly, though I don't know what the record
is. That should be researchable, and the fastest time is probably from
one of the last three UNICONs. Hopefully their 10k distances were all
accurately measured. This can establish for us a 10k speed record.

I remember reading a thing from 1888 or so, in which a guy went out and
established speed records in one mile increments all the way up to 14.8
or so. This was how far he got in an hour. In 1888! His wheel size is
unknown, but was probably in the range of common bike front wheels of
the day.

The IHPVA (International Human Powered Vehicle Association) keeps speed
records for various types of pedal powered vehicles. In 1986 or 7, Floyd
Beattie went to their meet in Indianapolis and set a "sprint" record,
using their 200 meter speed trap. To establish a record, you must ride
the course in both directions, and then the two times are averaged to
eliminate wind effects. He was riding on a brand new 45" Tom Miller big
wheel, that had just been assembled so he wasn't yet used to it. I don't
remember the details, but his times meant a speed of about 23 mph.
That's the only such record I know of for top speed over a short
distance. Even Floyd knows it wasn't that fast, and I'm sure he could
have gone much faster after getting acquainted with the cycle.

Floyd Beattie also did an hour record on a velodrome. He was a purist
about the whole thing, and only drank the water he carried with him,
refusing to pick up any he hadn't brought along. Anyway, he used up all
his water pretty quick, got dehydrated, and then had to "retire" in the
last few minutes to heave ho. He covered something like 14.89 miles,
about the same as the guy in 1888. This is from memory; not sure about
the exact numbers other than that it was real close to 15 miles.

Of course we know the 100 mile record is 6:44, which is amazingly fast
over such a long distance. That one is also supposedly the world record
for longest unicycle ride without a dismount (Takayuki Koike, 1987).

The Budweiser Rocket Car, making a run at the land speed record in 1982
or so, went up onto its single front wheel for more than 100' when
shockwaves formed on the rear part of the car. That's the world's
fastest *powered* unicycle.

Brett Bymaster has done gliding at speeds over 20mph, which is pretty
dang scary. He says he has approached 25, but I don't know if he ever
quite got there. That's just dangerous. Someone in Germany, maybe Arne
Tilgen (?) has gone over 40 kph gliding, while being towed by a
motorcycle.

Possibly the fastest glide I ever saw was done by Yuichiro Kato at
UNICON IV in 1988, at the world's first-ever Gliding competition. He
went flying down that hill at an unknown speed, his pedals a blur, until
he lost it and went sliding about 10m on his hands and knees.
Fortunately that was also the first year UNICON required everyone to
wear kneepads and gloves! He was unharmed. His second run was much more
conservative, and he didn't win. The winner of the contest was Fuyuki
Tsuchiya, who now works for Miyata and the JUA, and may be one of the
hosting persons at UNICON next summer.

Coasting? You just don't go fast. I've never seen anyone coast faster
than they do in one of our flat-ground coasting competitions. To do it
downhill would be spectacular to watch, but very dangerous for the
rider.

So, I believe what I've heard about Christian Hoverath. He's probably
the fastest unicyclist on earth, but it's unofficial. He's got to do
some kind of repeatable speed trap record for it to be a "real" record.
30mph? I'm not going that fast...


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Good stuff John. According to Brett's (now dead) High Speed Gliding
page, he's gone 25.5mph gliding.

In case you're not really sure what gliding is, vs coasting, check out
these photos of Brett and John:
http://www.unicycling.org/unicycling/skills/glide.html

John, remember that time at Tahoe when Brett decided to glide down that
steep hill by the cabin before we left for Mr Toads? No safety gear, no
nothing, in seconds he was FLYING down that hill. I think he said that
run felt like under 20mph, so I'd hate to see 25.5.

---Nathan


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On Thu, 4 Sep 2003 12:48:17 -0500, Ken Fuchs
wrote:

So to get an accurate wheel circumference, one really should ride a long
accurately measured course in the way one expects to ride. One should
go about the speed one most often expects to go. The Q factor is a
constant for the Coker until the hub is changed. The Wobble mass is a
constant for the Coker and rider until the cranks/pedals are changed or
the rider bulks up (or loses weight in) his legs.

If one gets an accurate wheel rotation count, one can simply divide the
distance by the count to get the effective wheel circumference,
including both wobble and tire compression effects.

Otherwise, one can simply enter one's best guess of the effective wheel
circumference. Ride the measured course and compare the real (measured)
distance to the computer's distance. Compute the difference as a +/-
percentage and adjust the computer's circumference by the same
percentage.

That is all clear. Of course we have to bear in mind that the
difference between the two kinds of speed is only of the order of 1%,
as pointed out by Ken. So many people would consider the following
argument to be nitpicking; but hey, I like to pick a nit every now and
then :-)

It is a matter of taste what one should consider as the real speed (or
real distance, for that matter). Probably most would agree that road
speed is real speed, or 'effective' speed as Ken almost called it.
Yet, contradictorily (SP?), most people seem to calibrate their
computers on a straight-line rollout, sometimes even unloaded.

However, tyre speed (and distance) are equally real in their own
right. For one thing, tyre speed is the real physical speed with which
the tyre contact point travels. Also, tyre distance (as opposed to
road distance) determines tyre wear (combined with a lot of other
factors, including funnily enough wheel wobble in itself). And when
you race between a start line and a finish line 100 metres apart, the
wheel will actually have travelled (say) 101 metres, in a wobbly line
indeed.

Not being able to make a single choice in this matter, the spreadsheet
in which I record my road rides calculates both tyre speed and road
speed.

Klaas Bil - Newsgroup Addict
--
I go a sort of ok speed on my Coker... - Roger Davies

The high speed gliding page lives!
http://www.unicycling.com/brett/hsg.shtml

Brett hasn't maintained his content in a long time. He basically turned
it over to me, so it's waiting in line, behind my own site, to be
brought together and updated. That includes the "Official MUni FAQ,"
circa 1998 or so...


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the Uni-Cyclone
www.unicycling.com
________________

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"Where's my unicycle?" -- Andy Cotter
spoken one right after the other, mostly to themselves, at NAUCC 2003

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On Thu, 4 Sep 2003 12:48:17 -0500, Ken Fuchs
wrote:

So to get an accurate wheel circumference, one really should ride a
long
accurately measured course in the way one expects to ride. One
should
go about the speed one most often expects to go. The Q factor is a
constant for the Coker until the hub is changed. The Wobble mass is
a
constant for the Coker and rider until the cranks/pedals are changed
or
the rider bulks up (or loses weight in) his legs.

If one gets an accurate wheel rotation count, one can simply divide
the
distance by the count to get the effective wheel circumference,
including both wobble and tire compression effects.

Otherwise, one can simply enter one's best guess of the effective
wheel
circumference. Ride the measured course and compare the real
(measured)
distance to the computer's distance. Compute the difference as a +/-
percentage and adjust the computer's circumference by the same
percentage.

That is all clear. Of course we have to bear in mind that the difference
between the two kinds of speed is only of the order of 1%, as pointed
out by Ken. So many people would consider the following argument to be
nitpicking; but hey, I like to pick a nit every now and then :-)

It is a matter of taste what one should consider as the real speed (or
real distance, for that matter). Probably most would agree that road
speed is real speed, or 'effective' speed as Ken almost called it. Yet,
contradictorily (SP?), most people seem to calibrate their computers on
a straight-line rollout, sometimes even unloaded.

However, tyre speed (and distance) are equally real in their own right.
For one thing, tyre speed is the real physical speed with which the tyre
contact point travels. Also, tyre distance (as opposed to road distance)
determines tyre wear (combined with a lot of other factors, including
funnily enough wheel wobble in itself). And when you race between a
start line and a finish line 100 metres apart, the wheel will actually
have travelled (say) 101 metres, in a wobbly line indeed.

Not being able to make a single choice in this matter, the spreadsheet
in which I record my road rides calculates both tyre speed and road
speed.

Klaas Bil


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