Re: Uni5
On Fri, 05 Apr 2002 14:17:53 GMT, Johnny B
<centromachetestakethisout@takethisoutyahoo.com> wrote:
>The 2-speed ends up being a direct
>drive plus the 33% overdrive like Greg’s hub.
For all I know Greg’s hub is geared 1 to 1.5 (or 1.5 to 1?) which as I
see it is a 50% overdrive.
“To trigger/fool/saturate/overload Echelon, the following has been picked automagically from a database:”
“TWA, DONCAF, ReMOB”
Re: Re: Uni5
Klaas-
You are correct about the 1.5:1 ratio. Johnny was just pointing out that the second gear on the 2-speed fixed hub is for gearing up. I don’t think he was saying that the Uni.5 has a 1.33:1 gear ratio.
Re: Uni5
harper <harper.2nqja@timelimit.unicyclist.com> wrote in
news:harper.2nqja@timelimit.unicyclist.com:
>
> Klaas Bil wrote:
>> *On Fri, 05 Apr 2002 14:17:53 GMT, Johnny B
>> <centromachetestakethisout@takethisoutyahoo.com> wrote:
>>[color=darkred]
>> >The 2-speed ends up being a direct
>> >drive plus the 33% overdrive like Greg’s hub.
>>
>> For all I know Greg’s hub is geared 1 to 1.5 (or 1.5 to 1?) which as
>> I
>> see it is a 50% overdrive.
>>
>> Klaas Bil
>> *
>
> Klaas-
>
> You are correct about the 1.5:1 ratio. Johnny was just pointing out that
> the second gear on the 2-speed fixed hub is for gearing up. I don’t
> think he was saying that the Uni.5 has a 1.33:1 gear ratio.
>
>
> –
> harper - Greg Harper: Frequent Faller (oops)
>
> -Greg Harper
>
> (now able to meet the pavement at 1.5 times normal speed)
> “It takes twice the man to ride half the bike.”
>
> ------------------------------------------------------------------------
> harper’s Profile: http://www.unicyclist.com/profile/426
> View this thread: http://www.unicyclist.com/thread/17264
>
>[/color]
I’m going by input:output on the ratio. 2/3 rev of the cranks makes one
rev of the wheel, and all the ratios I’ve seen have had a 1 on the right
side of them. So, this would be a .67:1 ratio, same as a 1:1.5, thus the
33% overdrive. If I’m just completely being a dumbass, and am way off
base, let me know. I know that 2/3 is .666666666666666666 repeated
infintely, so I rounded up to .67. Actually maybe it’s .666 and harper is
Satan. Just kidding harper.
John
Re: Uni5
klaasbil_remove_the_spamkiller_@xs4all.nl (Klaas Bil) wrote in
news:3cadfd16.4484149@newszilla.xs4all.nl:
> On Fri, 05 Apr 2002 14:17:53 GMT, Johnny B
> <centromachetestakethisout@takethisoutyahoo.com> wrote:
>
>>The 2-speed ends up being a direct
>>drive plus the 33% overdrive like Greg’s hub.
>
> For all I know Greg’s hub is geared 1 to 1.5 (or 1.5 to 1?) which as I
> see it is a 50% overdrive.
>
> Klaas Bil
I’m thinking that a 50% overdrive would be .5:1, or 1:2. Half a crank
rev for a full wheel rev. Again, going by the input:output standard that
I’ve seen used on all gear ratios I’ve seen. Likewise, if I’m way off on
this, throw old tires at me or something. 
John
Re: Uni5
Percents can be strange things. They relate to a reference and it’s
just convention what you pick as a reference. In the case of geared
hubs I have no authority at all as to what the convention is. Your
calculation makes sense, it’s just a bit counterintuitive to me.
But then, if a price increases by 10%, and subsequently decreases by
10%, it ends up being 99% of was it was initially. Go figure.
You can have my old tyre if you want. Coincidentally I plan replacing
the tyre on my Semcycle 24" tomorrow.
Klaas Bil
On Sat, 06 Apr 2002 05:58:43 GMT, Johnny B
<centromachetestakethisout@takethisoutyahoo.com> wrote:
>klaasbil_remove_the_spamkiller_@xs4all.nl (Klaas Bil) wrote in
>news:3cadfd16.4484149@newszilla.xs4all.nl:
>
>> On Fri, 05 Apr 2002 14:17:53 GMT, Johnny B
>> <centromachetestakethisout@takethisoutyahoo.com> wrote:
>>[color=darkred]
>>>The 2-speed ends up being a direct
>>>drive plus the 33% overdrive like Greg’s hub.
>>
>> For all I know Greg’s hub is geared 1 to 1.5 (or 1.5 to 1?) which as I
>> see it is a 50% overdrive.
>>
>> Klaas Bil
>
>
> I’m thinking that a 50% overdrive would be .5:1, or 1:2. Half a crank
>rev for a full wheel rev. Again, going by the input:output standard that
>I’ve seen used on all gear ratios I’ve seen. Likewise, if I’m way off on
>this, throw old tires at me or something.
>
>John[/color]
–
“To trigger/fool/saturate/overload Echelon, the following has been picked automagically from a database:”
“CESID, NRC, rail gun”
Re: Uni5
On Fri, 5 Apr 2002 13:03:08 -0800, John Foss <john_foss@asinet.com>
wrote:
>I don’t see how you are more or less exposed to the elements on a different
>sized wheel. You are presenting exactly the same profile to the wind, and
>sitting in the same position. The difference is you don’t have all that
>wheel causing wind drag.
I disagree here. Firstly, there is always a wind speed gradient (if
there’s wind at all): wind speed is close to zero near the ground and
increases with height. So sitting higher up on a large wheel the rider
feels more wind. The absolute amplitude of wind gusts will also be
larger. Secondly, a larger wheel will itself be more susceptible to
get pushed off course by side wind just because it has more surface
area (and on average farther from the “vertical axis”) that the wind
is pushing against.
Klaas Bil
“To trigger/fool/saturate/overload Echelon, the following has been picked automagically from a database:”
“CESID, NRC, rail gun”
Re: Uni5
Percents can be strange things. They relate to a reference and it’s
just convention what you pick as a reference. In the case of geared
hubs I have no authority at all as to what the convention is. Your
calculation makes sense, it’s just a bit counterintuitive to me.
But then, if a price increases by 10%, and subsequently decreases by
10%, it ends up being 99% of was it was initially. Go figure.
You can have my old tyre if you want. Coincidentally I plan replacing
the tyre on my Semcycle 24" tomorrow.
Klaas Bil
On Sat, 06 Apr 2002 05:58:43 GMT, Johnny B
<centromachetestakethisout@takethisoutyahoo.com> wrote:
>klaasbil_remove_the_spamkiller_@xs4all.nl (Klaas Bil) wrote in
>news:3cadfd16.4484149@newszilla.xs4all.nl:
>
>> On Fri, 05 Apr 2002 14:17:53 GMT, Johnny B
>> <centromachetestakethisout@takethisoutyahoo.com> wrote:
>>[color=darkred]
>>>The 2-speed ends up being a direct
>>>drive plus the 33% overdrive like Greg’s hub.
>>
>> For all I know Greg’s hub is geared 1 to 1.5 (or 1.5 to 1?) which as I
>> see it is a 50% overdrive.
>>
>> Klaas Bil
>
>
> I’m thinking that a 50% overdrive would be .5:1, or 1:2. Half a crank
>rev for a full wheel rev. Again, going by the input:output standard that
>I’ve seen used on all gear ratios I’ve seen. Likewise, if I’m way off on
>this, throw old tires at me or something.
>
>John[/color]
–
“To trigger/fool/saturate/overload Echelon, the following has been picked automagically from a database:”
“CESID, NRC, rail gun”
Re: Uni5
On Fri, 5 Apr 2002 13:03:08 -0800, John Foss <john_foss@asinet.com>
wrote:
>I don’t see how you are more or less exposed to the elements on a different
>sized wheel. You are presenting exactly the same profile to the wind, and
>sitting in the same position. The difference is you don’t have all that
>wheel causing wind drag.
I disagree here. Firstly, there is always a wind speed gradient (if
there’s wind at all): wind speed is close to zero near the ground and
increases with height. So sitting higher up on a large wheel the rider
feels more wind. The absolute amplitude of wind gusts will also be
larger. Secondly, a larger wheel will itself be more susceptible to
get pushed off course by side wind just because it has more surface
area (and on average farther from the “vertical axis”) that the wind
is pushing against.
Klaas Bil
“To trigger/fool/saturate/overload Echelon, the following has been picked automagically from a database:”
“CESID, NRC, rail gun”
John, Bill.
Hang on a minute I think your both missing a simple principle of physics here. It’s not the wheel that is most influenced by the wind but the rider, as the rider has a larger cross-sectional area (some more than others). Whilst it is true that a coker has a greater cross-section area than a 20" due to the size of the wheel and is therefore more influenced by wind a 5’ girraffe is even more influenced than the coker and yet the cross-sectional area much smaller than a coker. Reason - you have to take into account how the cross-section area is distributed in relation to hieght and the most significant part of this is the rider.
The principle of wind gradient is well documented in that wind increases with altitude or more practically speaking wind decreases with lower altitude due to the influence of ground clutter and meterological influence. The reason why we don’t have 200mph jet streams at low altitude is that all the weather we have at low altitude has a braking effect, go out to the further planets which have smaller meterological effects such as Neptune and the jet stream gets up to almost sonic speeds.
However wind gradient is only significant in relation to aircraft and the construction dynamics of tall buildings. The differences in altitude between a rider on a 20", a coker or a 5’ giraffe are too small to show any significant difference in windspeed. At these differences in altitude windspeed is most influenced by local ground topography eg. a rider on a 20" will be less affected by wind than a rider on a coker if they both ride behind a 6’ wall as more of the coker rider is exposed above the wall than the rider on the 20".
If we ignore local ground topography and put our theoretical riders out on a grass playing field then both are experiencing tthe same wind speed and therefore the same force on their bodies when riding in the same direction. But the higher the rider is the greater the influence of the wind due to their higher moment of inertia.
Think of the riders as being vertical levers. The point of contact between ground and tyre is the fixed point and the rider is the point where the force is applied. Simple school physics tells you that the higher a rider is the greater the influence when the same force is applied.
Come on guys, it’s a simple principle a twelve year old could have told you. The bigger the wheel, the higher you sit - the higher you
sit the greater the influence of the wind.
Further to my previous post - would the physics specialists in the group please forgive me if the statement about moment of inertia is the wrong way round and should have said “a lower moment of inertia” it’s a been a while since I did school physics, but I’m sure you followed the train of thought.
**That wouldn’t be the only thing you’ve got backward, Noel:
Christopher
**For those of you who don’t use the forum: Noel uses this image inverted as an Icon.
As far as height above the ground, I doubt that there is any significant difference between a rider on a Coker, a 26", or even a 16" in terms of average ambient wind speed. The difference in height is probably less than 20% of the height of the rider for most riders and crank combinations. This is easy to see when you consider that ground topography, especially ground cover like bushes and trees, has a more significant effect on ground wind speed than weather systems, etc. Compared to the size (height and windage) of these objects, raising myself up 10" or so makes no difference as far as the wind I experience. Taking the turbulence of ground air movement into account eliminates that small of a difference completely.
As far as height above the ground, I doubt that there is any significant leverage difference between that of those wheels either, for the same reason: the difference in height above the ground compared to the overall height of the rider/cycle is not that much.
At uni speeds, I doubt also that there is much effect of the size of the Coker wheel in terms of “wind drag”; that is, the air resistance to forward motion induced by the frontal area of the wheel and the motion through the air of the spokes. At speeds above, say about 14 mph, perhaps there is some spoke drag. Compared to the drag caused by the rider’s frontal area, however, these things are negligible at any Coker speed.
I imagine that the most significant wind effects that the Coker and other larger wheels experience (more than other, smaller unis) would be the vertically-aligned twisting motions and sideways linear pressure caused by side winds, especially gusts. 1) The sideways area (windage) of the larger wheels is significant compared to that of the rider, and 2) the moment arm of the larger wheel about the vertical axis is significantly larger. Think of the vast difference in force required for riding with 170mm cranks as opposed to 150mm cranks; the difference in moment arm for a Coker vs a 20’ or 24" is more significant than that. The forces produced by these wind effects induce control issues for the rider that make efficiency go down. The rider has to work harder to counteract the forces to stay on course, and travels a longer distance because his/her travel line is less efficient. This is one case where a geared-up uni with a smaller actual wheel, but equally-sized effective wheel, may have an advantage.
For headwinds or tailwinds, it seems as though they would be slightly more significant control-wise for a larger actual wheel. Although the force on the rider/cycle would be essentially the same as the force on the rider/cycle of a 20", the momentum of the larger wheel means that the falling-forward or -backward torque for a given relative speed of headwind or tailwind would be more significant for the larger wheel. In essence, the momentum of the larger wheel keeps the wheel anchored at speed while the head/tailwind pushes the rider backward/forward. This is not true for the 20"er because the wheel has no significant momentum. Although the head/tailwind pushes as hard on the 20"er, the wheel doesn’t want to keep going it’s own way nearly as hard. There are two aspects of this momentum: rotational inertia and translational inertia. The translational inertia (the inertia of the wheel going forward without considering its rotation) is obviously much higher for the Coker, assuming the same horizontal velocity, because the wheel is heavier (has more mass). The rotational inertia difference isn’t clear to me because, although the Coker wheel has a larger diameter, the smaller wheel is rotating faster for a given ground speed. Since inertia is essentially mass times velocity, the faster rotation of the smaller wheel may make up for its lower rotational mass. We’d have to look at the equations to be clear.
Noel - when you said "But the higher the rider is the greater the influence of the wind due to their higher moment of inertia. " you meant to say that the influence of the wind would be greater because the moment arm would be greater - that is, the same force is applied farther away from the pivot. To say “lower moment of inertia” would be incorrect because making the rider/cycle longer would actually increase its angular inertia. But here you are talking about the force (the wind), not the inertial properties of the rider/cycle.
Re: Uni5
Ah, my secret identity is undone! Time to book another appointment with the
plastic surgeon.
It’s not really a negative but was produced by heavy solarisation, double
bleach toning and selective etching. Basically I was mucking about in the
darkroom one day and trying to see how many different B&W techniques I could
use and still end up with a reasonable image image. The final 8x10 glossy
has been the first image in my portfolio for 5 years now and I also use it
on some of my contact cards.
“rhysling” <rhysling.2qvym@timelimit.unicyclist.com> wrote in message
news:rhysling.2qvym@timelimit.unicyclist.com…
>
> **That wouldn’t be the only thing you’ve got backward, Noel:
>
> [image: http://users.telepak.net/~rhysling/whoyourunningfrom.jpg]
>
> Christopher
>
>
>
> **For those of you who don’t use the forum: Noel uses this image
> inverted as an Icon.
>
>
> –
> rhysling - Last of the Mississippi Unicyclists
>
> “Have you considered the name Gregory C. Harper for your baby? I think
> it’s a gender neutral name so it should be appropriate for anyone.”
> ------------------------------------------------------------------------
> rhysling’s Profile: http://www.unicyclist.com/profile/411
> View this thread: http://www.unicyclist.com/thread/17264
>
With out adding any more wind to this discussion: the more upity I get, the more the wind slaps me around like a 2 bit pimp. Ya, that’s right- that wind’s freak’n brutal.
Christopher
Re: Uni5
Noel,
You may be right about the larger leverage on the higher-seated rider.
But you also have to realise that a higher-seated rider takes a longer
time to fall to such an extent that he gets outside his balance
envelope. Getting off-balance is just a more sluggish process if
you’re sitting high so you have more time to correct it.
About wind gradient: there are some data on various places on the www
including
http://ourworld.compuserve.com/homepages/lestergilbert/Gradient/Gradient.htm
that suggest that the effect of wind gradient certainly does play a
role at heights up to a few meters (and not only at heights relevant
to air craft and tall buildings). I continue to believe that a Coker
rider feels more wind at the same speed than a 24" wheel rider.
“To trigger/fool/saturate/overload Echelon, the following has been picked automagically from a database:”
“counterintelligence, ANDVT, Carlos”
