Speed?

General
1

A bit mathematical but:

We all know that at a given cadence, a bigger wheel will go faster than a small one.

We all know that for a given wheel size, smaller cranks will tend to allow a faster cadence than larger ones.

We all know that the ratio of crank size to wheel radius (or diameter) influences ease of mounting, idling and hill climbing/descending.

So, what is the best combination?

Yesterday I hit a top speed of 13mph and averaged 7.18 mph on the 24 with 102s in a ride of about 1 hour.

Today I hit a top speed of 14 mph and averaged 10.16 mph in approximately an hour on the Coker - a 26 with 125 mm cranks.

The top speed bit surprised me. As the computer only records this to a whole number, it is possible I did 13mph exactly on the 24, and 14.9 mph on the Coker, but applying the principle of mediocrity, I have to assume that the top speeds are only about 1mph apart, and that the Coker is about 7% faster. (Yes, I know skill and confidence come in here, but I feel my level of each is broadly similar on the two unis.)

The Coker averages about 41% faster, though. This is not entirely scientific, as the routes were different, and the Coker ride included a straight 10 km of level tarmac - but it also included riding across a field in the pitch dark. The rides were roughly equivalent in difficulty.

The Coker wheel is 50% bigger than the 24.
The 24’s cranks are about 19% shorter than the Cokers. Say 20%

50% minus 20% of is 40%.

The figures are near enough that it suggests to me that within certian limits, a % reduction in crank size is almost identical in effect to a % increase in wheel size for top speed.

Anyone who’s followed this far, thanks. Comments anyone?

2

Keep going with the crank size experiments Mike. I’m thinking of getting some small cranks and temporarily swapping my Gazz for the road tyre the Nimbus II came with to do some (relatively) fast riding. I know I should be getting a Coker, I’m working on it :wink:

I wouldn’t trust the top speed recorded on a trip computer when used on a uni as a couple of quick idles could give it a false reading. Where on the wheel, relative to the cranks, have you located the magnet? Have you used one or two magnets on the Coker?

Cheer, Gary

3

It was recommended to me (after reporting an unlikely speed reading) to do as Gary suggested- use two magnets and halve the roll out number.

I’m not sure that statements of efficencey are all that usefull- we’re all so different. Did you see that pic of the guy in the Unicon race with the 73’s (or something close, I think)? Those would be useless to me… I think he came in second or third.

“an hour on the Coker - a 26 with 125 mm cranks.”

What does this mean? Were the figures actualy for a 26" cycle? Considering the pace you set on the 24", I’d be surprised if you couldn’t hit 17 or 18 on the Coker, and maintain 13-14 mph on flat ground, for the durration of your previous rides.

-Christopher

4

I have found that the best way to make a unicycle go fast is to have Christian Hoverath ride it.

5

When I can do ‘a couple of quick idles’ on a Coker with 125s, i will bear that in mind. Not holding my breath…

One magnet only, but the speed readings seem plausible. the computer is there mainly as a distance counter, and I’m not over worried about accurate speed readings - I can’t read it when I’m riding anyway.

6

It means I’m a lousy typist. As every skuleboy kno, a Coker is a 36. :o

7

Re: Speed?

On Tue, 22 Oct 2002 13:36:32 -0500, Mikefule
<Mikefule.cxu5a@timelimit.unicyclist.com> wrote:

>(for max speed) the Coker is
>about 7% faster.

>The Coker averages about 41% faster, though.

>50% minus 20% of is 40%.
>
>The figures are near enough that it suggests to me that within certian
>limits, a % reduction in crank size is almost identical in effect to a %
>increase in wheel size for top speed.

For TOP speed? Judging from your data, I think you mean for AVERAGE
speed?
The issue of crank length and speed (top or average not specified) has
come up before. Roger argued that foot speed should be about constant
even if crank length varies. If I have time (oh when??) I will try out
125, 150 and 170 (!) mm cranks on a street 24". I will measure max
cadence. Maybe I’ll buy me some 102’s as well. If I have data, I’ll
post.

Klaas Bil

I posted only a single copy of this message.

8

Re: Speed?

That sounds right to me. At the Muni race at Unicon I had a spare Telford
that I wanted to have go fast, so I gave it to Christian to ride and he came
in 4th, beating me and most other “serious Muni guys”!(Obviously your real
point is that the rider matters more than the equipment.)

—Nathan

“harper” <harper.cxyjp@timelimit.unicyclist.com> wrote in message
news:harper.cxyjp@timelimit.unicyclist.com…
>
> I have found that the best way to make a unicycle go fast is to have
> Christian Hoverath ride it.
>
>
> –
> harper - Gearhead

9

Re: Re: Speed?

Hey, aren’t you the guy who beat me in the 10k on my own unicycle? I had a one-of-a-kind high-tech machine and you still beat me with my clunky Coker.

10

“50% minus 20% of is 40%”

???

11

Re: Speed?

D
“GILD” <GILD.cz7gc@timelimit.unicyclist.com> wrote in message
news:GILD.cz7gc@timelimit.unicyclist.com…
>
> “50% minus 20% of is 40%”
>
> ???

Depends on what exactly you read into the question.

If you take 50% of something and then reduce what you now have by 20%,
you get 40% of the original amount remaining.

If you take 50% of something then remove another amount equal to 20% of
the original, then yes, you get just 30% of the original remaining.

The mathematics is stated somewhat unclearly but .
re-write the statement something like :

reduce 50 by 20% and you get 40 (or 0.5 reduced by 20% = 0.4 )

and you will find it easier to understand what I think Mikefule is getting
at…

Whether I agree that a 20% reduction in crank might equate to a 20% increase
in speed, is a different matter. Crank length governs acceleration,
ability to climb inclines, and how big a circle your feet have to make.
It doesn’t DIRECTLY affect speed, as Mikefule obviously knows. I think this
will have a lot more to do with personal abilities and strengths as well.
So 20% for Mike: 35% for Fred etc etc.

Naomi ;-).

…

12

Firstly, an apology. My original post on this thread was written in haste and, bearing in mind it dealt with a number of mathematical and technical matters, I should have been more careful in my phraseology and my typing.:o

Crank length does not directly affect speed, I agree - but it does directly affect the maximum rpm available to a given rider at a given level of ability. My guess is that both maximum and ‘comfortable average’ footspeeds are more or less constants for a given rider at a given level of his/her development. Thus, taking 25% off the length of the cranks will mean 33% more rpm, all other thngs being equal. (Take off 25% - put back 33% to return to where you started. Try it with 4 apples if the maths seems obscure.)

Wheel diameter (or radius) does not directly affect speed, but it does determine the speed of the unicycle at any given cadence (rpm).

So, in simple terms, a bigger wheel should make it possible for you to go faster; smaller cranks should make it possible for you to go faster.

My interest is in which is most important or effective. There are many variables, including the level of confidence of the rider, the hilliness or bumpiness of the ground, and so on. I suspect that the RATIO is critical to top speed because of its effect on control and fore & aft balance.

However, take two broadly similar unis (say a Nimbus 20 and a Nimbus 28) and a selection of crank sizes. Take a piece of flat and level ground, and a reasonably experienced rider. What will be the fastest combination of wheel and crank size?

Put 102s on a 28 and you have a leverage ratio of 28.6% which is more leverage than a standard Coker. That makes fine control difficult, and I suggest may mean that 102s on a 28 will produce a lower sustainable maximum cadence than 102s on a 20.

So which would be faster - a 28 with 125s, or a 20 with 102s?
The 28 is 40% bigger, so 40% faster at a given rpm.

The 102s are 18% shorter, so offer (potentially) 22.5% more rpm.

So taking the 28 should go (put crudely) 40 % faster but 18% slower. 1 X 1.4 x 0.92 = 1.29. If so, then the 28 should average around 29% faster and should max out at 29% faster.

Applying this to my real situation, I found that there is little difference in top speed between my 36 on 125s, and my 24 on 102s, but the difference in average speed roughly corresponds with what the maths would suggest.

13

Re: Speed?

To start to answer this, you have to define the question a little better. Do you want pure speed? If so, over a short, medium, or long distance? Each might have a different answer.

All of these answers will also be relative to the person riding. Some people prefer big wheels, while others are less confident on them and ride a little more conservatively. These people might do better on 28" for example.

In other words, we are not machines. To compare results on a 24", say, with the cranks you use all the time, with results from a single ride with a new size of cranks will give you false results. Your body is used to the cranks you use all the time, but there is a “break in” period for sizes you’re not used to. The same is true for wheel sizes. Riding a Coker, if all you’ve had before is 24", is very different, and it may take weeks or months of riding to get truly efficient on it.

Lastly, I think leg lengh and knee condition can be factors in the cranks vs. wheel size debate. I have relatively long legs, and 125mm cranks on my Coker. I can ride it to work just fine, but if I ride it home the same day, my knees will be toast. I think I may have to use longer cranks for a while, and work my way down to shorter ones and see how my knees react.

Then there are the additional factors of cycle weight, friction from different tire types (high with a Coker tire), and especially wind resistance as you go faster. If speed is the goal, this is a constant, except you’ll get more drag with a bigger wheel (and if you wobble more).

So the human (and other) elements make these type of mathematical conclusions of limited use. Real world examples will often defy the numbers. Nathan’s example pointed out the biggest variable in all of this, which is what I refer to as “the engine.” Using a different “engine” for different tests will skew your results. You have to use the same engine for each test. But you also have to test with a variety of engines. People, that is. Get some Coker-lovers and some 24" lovers for best results. They may be surprised as well.

Keep these variables in mind, and happy testing!

John Foss

14

I am aware of many of the variables, and agree with all or most of what you say. However, I reckon my posts are long enough as it is, without putting all the caveats and exceptions in. :o

I’d say that on the whole, a bigger wheel will produce a smoother action, but the rider will be more cautious about ‘revving out’.

I’d say, on the whole, that a smaller leverage ratio will produce a lower top speed for the same reason. Thus, 125s on a Coker might produce (for example) a max cadence of 150, but 125s on a 24 might produce a max cadence of, say, 175 (for a given rider, example only, I have never worked out my max cadence).

So many variables, so much fun to be had from so few components. One of the beauties of unicycling is that the uni is such a simple device. Assuming the seat - pedal distance is more or less constant for a given rider, then what can (s)he vary? Crank length and wheel size, weight, section of tyre. Of these, wheel size is a fundamental choice (if you can only have one uni) and crank size is a variable.

On another thread someone asked which would be the best starter unicycle - the best 'all rounder, if you like. I started this thread partly because I was impressed by the all round flexibilty of the 24. My ‘experiments’ show a top speed which is, shall we say, comparable to a Coker (for me) and has a very respectable average speed. I guess that my 24 would top speed faster than my Coker with 150s in a very short burst. Other experiments have shown that the same 24 with 150s will sail up hills which stall my 26.

None of it matters, but it’s interesting (to me) and if the results help someone else to choose a uni, or to experiment with different set ups, then that’s too the good. :wink:

15

Attached is Roger’s wheel size/crank length/cadence Excel spreadsheet - might add some amusement.

-Christopher

cranklength.zip (3.24 KB)

16

Re: Speed?

harper <harper.cxyjp@timelimit.unicyclist.com> wrote:

> I have found that the best way to make a unicycle go fast is to have
> Christian Hoverath ride it.

Or Marc Hafliger. The 400m race at UNICON between these two
was absolutely fantastic…

Paul

Paul Selwood
paul@vimes.u-net.com http://www.vimes.u-net.com