Re: PING ALL COKEURS: Share your rollout data (Was Re: What circumference did

>Cokerhead writes:
>Here’s my scientific method. I stole data from other people. I entered
>it into my computer. I adjusted from time to time, based on
>observations from other road markings and bicyclists and car odometers. I
>am happy to get within 2% accuracy(I usually ere on the fast/long side).
>I give myself a break and don’t try to discount for wobble(I don’t wobble
>as much as some)
To add to Mark’s methods, here is what I do:
I rode over a ‘measured mile’ on a bike path and counted the revs, getting
about 577. I made sure the cycle computer gibed with that. This takes into
account the wobble of my riding. Here are the calcs:
Wheel height: 35.75"
Theoretical revs per mile [5280/(35.75 x pi)] = 564
Actual revs per measured mile: 577
Wobble effect: 2.3% (I ride an extra 23 feet for every thousand revs)
This means I’m riding an extra 115’ or so every mile.

If you factor your measured mile (revs per mile) into the cycle computer,
you get a truer idea of your actual speed than if you just go by
>Now to answer the questions:
>C:Varies from ride to ride:)
>I did a rollout(unloaded) long ago and don’t remember the number
>Right now I have 281 entered into my cyclometer and I’m happy with that
I can’t recall the # I entered. It’s certainly around that one.

I won’t post a rollout or method, but please allow me to post an opinion.

There are several things that are dynamic – they change from ride to ride, during a ride, and from rider to rider. They include:

A) Average “wobble”, both single-cycle and multi-cycle. This includes percentage of time “wobbling” and degree of wobble.

B) One’s exact path choice from A to B, assuming A and B are fixed points. Examples include the radius of one’s turn at a given corner, the way one stands up and torques a hill, and one’s approach to avoiding static obstacles, such as rocks, potholes, dirt patches, and dynamic obstacles such as automobiles, squirrels, bicycles, and the like.

C) The purpose of the ride: whether for training, or a time trial, or a race, or simply to go from A to B.

D) Tire choice and pressure.

E) Rider weight.

To include these highly changeable aspects into a number that goes into a cyclometer is very “dirty” scientifically and engineering-wise.

Since we are sharing information such as rollout with others, hopefully for one another’s convenience, I suggest that we as a community exclude as many of these dynamic factors as possible from our rollout figures.

For time trials, all that counts is an officially measured (i.e., with a calibrated wheel specifically designed for the purpose) course and a stopwatch. It is up to the rider to minimize the distance he actually travels to achieve the best time. The establishment of the start and end points is very important.

For all other purposes, the actual distance travelled by the rider is less rigorously important.

Of course, for everyday use one’s weight and pressure are factors that make it easy to read the cyclometer. But for purposes of sharing, it would be better to have a single clean number that is meaningful to other riders without further qualification. We could call this number the Uncalibrated Rollout. That is, it is uncalibrated to the individual rider’s characteristics. The number that takes all that individual rider stuff into account could be called the Calibrated Rollout.

I suggest the following approach.

Let’s put the tire at 50 psi and determine the average of two cycles unweighted, pushing the uni in a very straight line. This determines the wheel’s Uncalibrated Rollout.

An individual rider can then easily calibrate that number to his or her individual riding style. He or she can easily determine a single multiplier that takes into account of wobble, weight, typical tire pressure, etc… Call this multiplier the RCF, or Rider’s Characteristics Factor. Multiplying the Uncalibrated Rollout by the RCF gives the Calibrated Rollout. The rider can either put the calibrated rollout into the cyclo, or use the RCF after the fact to calibrate speed and distance.

For a simplified example, say my wobble reduces my actual distance covered by 3%. That is, my cyclo says I rode one mile, but I didn’t actually reach B, one mile away from A, because that mile was done in a wobbly way. All I have to do is multiply the cyclo reading by an RCF of 0.97 to get actual linear distance covered from A to B.

If I put the Uncalibrated Rollout into my cyclo, then I can easily give that number to another person. That other person will use that number and eventually get a feel for what that actually means for his or her individual characteristics.

So everyone on a tour could use the same rollout.

Everyone in an official time trial doesn’t care, because the time trial doesn’t make use of an individual’s cyclo.

People doing practice rides and practice time trials on their own aren’t making use of the rollout in an official way so they are free to do their own thing.

In essence, then, we could have one official Uncalibrated Rollout for a Coker tire on an Airfoil rim at 50 psi. It is up to the individual to determine his or her RCF for actual use.

As an additional incentive, note that many cyclos have room for two different wheel sizes, A and B. So a person could store his Uncalibrated Rollout and Calibrated Rollout in the same cyclo and use whichever fits the occasion best.


Re: PING ALL COKEURS: Share your rollout data (Was Re: What circumference did

On Tue, 9 Sep 2003 11:38:07 -0500, U-Turn
<> wrote:

First of all, I respect your opinion which you have so carefully
phrased. Thanks a lot! From the data that people post I hope to be
able to assess a typical (or ‘best’) Uncalibrated Rollout. And I will
include that number as a key result. Only I don’t like the name.
Uncalibrated sounds as if no care has gone into it, e.g. you just take
the nominal 36" and multiply by pi. I’ll try and think of another

>He or she can easily determine a single
>multiplier that takes into account of wobble, weight, typical tire
>pressure, etc… Call this multiplier the -RCF-, or Rider’s
>Characteristics Factor
I wouldn’t say that the effects of wobble, weight etc can /easily/ be
determined. Indeed, that is precisely what this little project is
about. But I like your way of reasoning and ideally the results of my
endeavour should include the Uncalibrated Rollout (by whatever name)
and a formula that calculates an estimated RFC from the parameters
mentioned in my ‘original’ post.

I won’t have time, BTW, to do the math until after next weekend.

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