# Fastest speed on a coker?

The high speed gliding page lives!

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…

On Thu, 4 Sep 2003 12:48:17 -0500, Ken Fuchs <kfuchs@winternet.com> 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

That’s really pretty hardcore… But I think it’s nice that you’d have at least three different potential answers to the question “How quickly did your tyre wear out?”

Hi John,

Do you know what gear ratio (wheel size/crank length) and terrain was used in the 100 mile record? Quite a few of us NZ unicyclists are doing the Lake Taupo Cycle Challenge which is a 160km/100mile race around this big lake called Lake Taupo (funnily enough). It would be nice to have something to aim for, although I don’t imagine Takayuki Koike was riding a Coker.

The hour record is impressive too, but perhaps with a Coker someone would be able to approach 30-35km? I think from memory the first bicycle hour records were around about 35km!

Takayuki’s 100 mile uni was a 43" air tire heavy thing. Those old wheels had massive rims and tires that were designed for industrial use on rickshaws or something similar. Heavy! I’m not sure about the crank length. Probably around 125 but I don’t know if I was ever told that. Jack Halpern might know. I think the unicycle belonged to him, or was the same as one he owned.

Takayuki was also racing with fellow 100-miler Floyd Beattie, who had previously held the record. Floyd was probably on his 45" (unknown crank length), but lost the race by a wide margin.

I think the terrain for the record ride was pretty flat. It was a bike path, on which they rode back and forth. I think they even had to do tight turnarounds at each end, but not sure about that. Again Jack Halpern might be able to fill in some of the details.

If you are preparing for your first century, I would advise against working toward survival. After you’ve got a few centuries under your belt, you can shoot for the record. Takayuki’s record is way beyond all the previous 100 mile times, and impresses even bicyclists. I think the second-fastest century on a unicycle is somewhere over 8 hours, but I’m not sure. This should be researchable with old Guinness books.

Re: Re: Fastest speed on a Coker?

Just got a computer, and that 3% matches the figure I just calculated quite well.

I calibrated my computer for 36" tire (I did not specifically measure the Coker tire).

I managed a 0 UPD ride around the block; the computer read 2.738 miles.

Previously measured this ride, in the car, with a GPS at 2.65 miles.

Error calculation: 2.738 / 2.65 = 1.0332 that is 3.3% error.

CORRECTION:
Remove “against!” I meant to say I advise against trying for that amazing record on your first century attempt. It was not the first time Takayuki had done it.

Someone on a geared Coker might have a chance of breaking Takayuki Koike’s 100 mile record. Harper’s hub is geared at 1:1.5 (one turn of the pedals yields 1.5 turns of the wheel). Put that hub on a Coker wheel and you’ve got about a 54" effective wheel. You could go quite fast on that. I hope they wear appropriate safety equipment because a UPD at that speed would be nasty. A German fellow has a geared hub that is geared at around 1:1.67 which would give a Coker wheel a 60" effective diameter. Someone is going to challenge the 100 mile record and it will probably be on a geared up Coker wheel.

But 6:44 for a 100 mile ride on a unicycle is amazing. I’d be happy doing a century in 6:44 on a bike (but I take rest stops when I do a century on a bike )

Hmm, if there is a constant linear relationship between the two numbers, isn’t maintaining both like reporting tire diameter and circumference?

I’m sure the relationship isn’t linear, but I doubt anyone has the equipment to make anything other than a guess at wheel speed.

However, I can see you point. I would not like to brag about my wages after taxes have take their nibble, which is far greater than 3%.

Thanks John. That certainly is pretty amazing. I make that to be an average speed of 23.76km/h! But I was afraid you were going to say he rode a 24’ unicycle, not that it makes it any less impressive!

I took my Coker for a 30km spin today and managed little over 20km/h . That was over fairly hilly terrain with 150mm cranks. I think I’d be able to do 160km with a bit of training, but I doubt I’d average much more than 20km/h even with shorter cranks. Realistically we’re aiming for 8-10hrs. There should be quite a few of us doing this ride so hopefully we’ll go faster (As a Coker peleton???- is there such a thing???) I wonder if drafting at 20km/h will save us a few minutes over 160km?

Re: Fastest speed on a coker?

On Fri, 5 Sep 2003 15:58:49 -0500, john_childs
<john_childs.tdcge@timelimit.unicyclist.com> wrote:

>A German fellow has a geared hub that
>is geared at around 1:1.67 which would give a Coker wheel a 60"
>effective diameter.
You probably mean Frank Bonsch? His hub gear ratio is actually
1:1.5833 so the Coker would effectively be 57".

## Klaas Bil - Newsgroup Addict

If the crank is moving then it really sounds as if it’s loose. - onewheeldave trying to pinpoint the cause of a clicking crank

Re: Fastest speed on a coker?

On Fri, 5 Sep 2003 17:21:31 -0500, iunicycle
<iunicycle.tdcgi@timelimit.unicyclist.com> wrote:

>Hmm, if there is a constant linear relationship between the two numbers,
>isn’t maintaining both like reporting tire diameter and circumference?
Yes but I don’t assume a constant linear relationship (only within a
ride but not between rides). Tyre speed is derived from a measured
rollout, road speed from the number of revolutions over a marked
distance on a road. I measure each one separately though not on every
ride.

>I’m sure the relationship isn’t linear, but I doubt anyone has the
>equipment to make anything other than a guess at wheel speed.
With wheel speed do you mean what I call tyre speed? There is no
special equipment involved. A tape measure to measure rollout, a
mind-and-mouth system for counting revolutions, and a stopwatch. Oh
and Excel.

## Klaas Bil - Newsgroup Addict

If the crank is moving then it really sounds as if it’s loose. - onewheeldave trying to pinpoint the cause of a clicking crank

Re: Fastest speed on a coker?

john_childs <john_childs.tdcge@timelimit.unicyclist.com> wrote:

>Someone on a geared Coker might have a chance of breaking Takayuki
>Koike’s 100 mile record. Harper’s hub is geared at 1:1.5 (one turn of
>the pedals yields 1.5 turns of the wheel). Put that hub on a Coker
>wheel and you’ve got about a 54" effective wheel. You could go quite
>fast on that. I hope they wear appropriate safety equipment because a
>UPD at that speed would be nasty. A German fellow has a geared hub that
>is geared at around 1:1.67 which would give a Coker wheel a 60"
>effective diameter. Someone is going to challenge the 100 mile record
>and it will probably be on a geared up Coker wheel.

I would agree almost 100%, John! I would rule out big wheels larger
than the Coker. Direct ride may still triumph!

>But 6:44 for a 100 mile ride on a unicycle is amazing. I’d be happy
>doing a century in 6:44 on a bike (but I take rest stops when I do a
>century on a bike )

John Foss reminded us that Takayuki’s unicycle for this Guinness record
was a 43" wheel with pneumatic tire. It is still extremely impressive
that he did that 100 mile ride in 6:44, since he averaged 14.85 MPH for
nearly 7 hours!

Sincerely,

Ken Fuchs <kfuchs@winternet.com>

Re: Re: Fastest speed on a coker?

Yes, I was thinking of Frank Bonsch.
I somehow got in in my brain that his hub was 1:1.67 which is incorrect. Harper has corrected me on that on more than one occasion.

Now that you have reminded me of his name I can find his web site.
UniFrank
He has a picture of his hub under “unicycle prototype”

The big advantage to Frank’s hub ratio is that it will result in even tire wear. Harper’s hub ratio of 1:1.5 will still cause tire wear in two spots so you’ll still need to rotate the tire on the rim to get even tire wear.

Hey! I can nit pick too!

Klaas wrote:

From Ken Fuchs’ Coker tire roll out dimensions I calculate the effective diameter of a Coker tire to be 34.7" so with the Frank Bonsch hub the Coker would be effectively 55".

John Childs wrote:

Actually Harper’s hub will result in four wear spots 90 degrees apart instead of two. Also John, you forget about switching the hub to 29" mode … there’s three possible places to anchor the arm dingus so if the hub is switched from 29" to 43.5" often, the tire should wear fairly even.

To further nit pick …

I measure the roll out circumference of the 29" Big Apple to be 89.6". That’s a diameter of 28.52" so the Harper hub actually makes an effective wheel diameter of 42.8" … with that tire anyway.

So there!!

Steve Howard

Speaking on behalf of myself and the other idiots I represent, I must ask “Why”? The uni appears to roll forward in a consistent manner, so why would there be four wear places? I understand why on a giraffe which gets idled a lot over the same part of the tire, but don’t see why it would happen on a uni that doesn’t get idled (much) and pretty much just does distance or speed riding.

Tom - “Why” you ask? The truth is “I don’t know”. It’s just that it’s so rare that I can pretend that John Childs has made a mistake I had to post!

Here’s what I think though: When you are riding down the road and your cranks are level (at 3:00 o’clock and 9:00 o’clock), that’s roughly the point where the most torque is being applied to the cranks and that’s what causes the slight “wobble” that unicycles demonstrate. The wobble scrubs the tire slightly and over time will wear the tire in two places more that the rest of the tire.

Here’s why I think Harper’s Hub will wear the tire in four places: The wobble happens every 180 degrees, or roughly when the right crank is at 3:00 o’clock and 9:00 o’clock. If you look at the pattern of cranks vs. wheel it looks like this -

right crank - 3:00 first tire scrub - 6:00
right crank - 9:00 first scrub - 3:00 new scrub 6:00
right crank - 3:00 first scrub - 12:00 second scrub 3:00 new scrub 6:00
right crank - 9:00 first scrub - 9:00 second scrub 12:00 third scrub 3:00 new scrub 6:00

Then the pattern repeats.

Probably completely wrong but there you have it anyway.

Steve Howard

Based on my uni racing experience I can’t recommend it. When done by bicyclists with lots of training and racing experience, drafting can still be fairly dangerous. Add the extra things that can go wrong on unicycles at high speeds, along with what I think would be a reduced aero benefit, and the return would seem to diminish quite a bit.

For those not familar with the situation, these are things that can go wrong in a drafting situation:

1. Rider in front falls–guaranteed fall for rider in rear, plus landing on front riders’ unicycle.

2. Touching tires front to back. If they touch pretty hard, it can throw off both riders–see #1.

3. Overlapping wheels–since our wheels generally don’t go straight but have some wobble, this could be disasterous. If the wheels touch and the rider’s center of mass is in the wrong place, it might be impossible to recover from the position.

Coker riders are generally going slower than bike in a race, so the amount of advantage you get from drafting will be less. I don’t know if the riders’ bodies are any closer than bike bodies, but the fact that we generally sit up much straighter, and are less aerodynamic, may increase the amount of “benefit” you could get from drafting.

But for me, I don’t think it would be worth the risk.

The general rule on bikes is that you need to be going over 15 to 17 mph (24 to 27 kph) before drafting becomes worth it. Below those speeds you are not getting enough of a draft off the front rider to give you much benefit. At speeds above 20 mph (32 kph) drafting gives you a very noticable advantage on a bike.

The thought of drafting another unicyclist at 17 mph is craziness. Too much risk of a very high speed UPD and a bad crash. Dangerous.

However, drafting behind a bike at 17 mph would be a little less crazy, but still crazy. You’d need the bike to cooperate and maintain a very consistent speed. It would be an exercise in intense concentration on the part of the bicyclist to be able to maintain a very consistent speed and communicate with the unicyclist about speed, road conditions, etc. The bicyclist would also have to sit up to create as big of a windbreak as possible.

Drafting at 17+ mph on a unicycle would be something to put on John Foss’ Things Not To Do page.

I’ve done A LOT of drafting on bikes, and John Childs is exactly right - it’s generally not helpful below something like 17mph. Biking in a tight paceline at 25-30mph is a fantastic feeling and not all that crazy as long as everyone knows what they are doing. This is where your front tire is 1 to 6" from the rear tire ahead of you. (Sometimes even touching!)

I’ve “drafted” on a unicycle going 10-12 mph (for photos), but it isn’t really drafting - you’re just riding behind the person in front.

There is one case where drafting on a unicycle actually makes sense: in a headwind. If you are able to push say 8-10mph into a 15mph wind, you actually do get some benefit from drafting. The reason is that John’s 15-17mph isn’t the speed of the cyclist, it’s the speed of the cyclist plus the headwind. So you’re relative speed to the air here is 23-25mph. Be very careful doing this on a unicycle!

—Nathan