Wheel building questions

On 20 Oct 2004 16:58:34 +0100 (BST), David Damerell
wrote:

Chalo wrote:
David Damerell wrote:
Chalo wrote:
jim beam wrote:
riding 16
spoke wheels however, the effect of cross winds is substantially less.
OK, that's an issue I had not considered. The effects of crosswinds
are not noticeable to me, even with 48 spoke wheels.
It's obvious nonsense, too; how do you suppose sock-boy imagines tandem
captains manage, with 48 spoke wheels and an extra rider stuck out the
back?
To extend "jim beam" the benefit of the doubt, I'll point out that a
tandem captain's situation is more like my own, with a heavily loaded
front wheel that is unlikely to be pushed around by wind due to its
sizeable contact patch. It's obvious if you ride one that a tandem
requires more force at the bars than a single bike, especially a
twitchy single.

I do ride one. It certainly requires more force at the bars, but it's by
no means unmanageable - even in heavy crosswinds, or with empty front
panniers (done that), or with no rider on the back.

Hence I don't believe for a minute that 20 extra spokes, with their
tiny area into the wind, present the slightest difficulty.

Dear David,

I wonder if it makes any difference that those 20 extra
spokes are spinning around 250 rpm when the rider is going
20 mph.

That is, in some ways spokes present a badly designed fan to
any crosswind, and 20 extra rapidly moving fan blades might
be different than 20 extra static wires.

Carl Fogel

Carl Fogel writes:

I do ride one. It certainly requires more force at the bars, but
it's by no means unmanageable - even in heavy crosswinds, or with
empty front panniers (done that), or with no rider on the back.

Hence I don't believe for a minute that 20 extra spokes, with their
tiny area into the wind, present the slightest difficulty.

I wonder if it makes any difference that those 20 extra spokes are
spinning around 250 rpm when the rider is going 20 mph.

You needn't wonder. The forward speed of the spoke does not affect
its lateral speed or the lateral drag it presents in a crosswind.
What does play a major role and has been reported by users here, is
that deep section aero rims cause significantly more interference
with steering in crosswinds.

That is, in some ways spokes present a badly designed fan to
any crosswind, and 20 extra rapidly moving fan blades might
be different than 20 extra static wires.

Rotating speed has no effect on the lateral drag.

Jobst Brandt

On Fri, 22 Oct 2004 02:21:04 GMT,
wrote:

Carl Fogel writes:

I do ride one. It certainly requires more force at the bars, but
it's by no means unmanageable - even in heavy crosswinds, or with
empty front panniers (done that), or with no rider on the back.

Hence I don't believe for a minute that 20 extra spokes, with their
tiny area into the wind, present the slightest difficulty.

I wonder if it makes any difference that those 20 extra spokes are
spinning around 250 rpm when the rider is going 20 mph.

You needn't wonder. The forward speed of the spoke does not affect
its lateral speed or the lateral drag it presents in a crosswind.
What does play a major role and has been reported by users here, is
that deep section aero rims cause significantly more interference
with steering in crosswinds.

That is, in some ways spokes present a badly designed fan to
any crosswind, and 20 extra rapidly moving fan blades might
be different than 20 extra static wires.

Rotating speed has no effect on the lateral drag.

Jobst Brandt


Dear Jobst,

Are you saying that a wheel's spokes (two faintly conical
arrangements) present the same resistance to a crosswind
whether the spokes are rotating or motionless?

Or am I misunderstanding you?

Carl Fogel

Carl Fogel writes:

Are you saying that a wheel's spokes (two faintly conical
arrangements) present the same resistance to a crosswind whether the
spokes are rotating or motionless?

Yes.

Jobst Brandt

Carl Fogel writes:

Are you saying that a wheel's spokes (two faintly conical
arrangements) present the same resistance to a crosswind
whether the spokes are rotating or motionless?

Your question alludes to the concept that if a car is driven fast
enough it will or will not have a side thrust from a side wind.
In a way, saying if you go fast enough the wind won't see you.

Jobst Brandt

wrote:
Carl Fogel writes:


Are you saying that a wheel's spokes (two faintly conical
arrangements) present the same resistance to a crosswind whether the
spokes are rotating or motionless?


Yes.

Jobst Brandt


how? you have the forward vector, the sideways vector, and assuming a
ninety degree crosswind, an effective wind velocity that would be the
root of the sum of the other two vectors, squared.

Rick Warner wrote:
jim beam wrote in message ...


no it's not "blind", but we've done it 6 times during the course of this
summer with the results described. tim, bottom line, i'm not trying to
force these things down your throat - i'm merely voicing my experience.
based on that, yes, i'm confident there is a measurable difference if
i were to instrument the two sets of wheels, but as you know, i don't
work in the materials biz any more, so i can't say i have plans on
renting the equipment unless someone's paying me to do it. if you find
yourself here in the bay area some time, let me know and i'll loan you a
bike for a spin across the bridge. if you don't detect any difference,
at least you'll have enjoyed the view while trying.


I had a very different experience with the Ultegra version of the
wheelset, the 6500.

i'm only aware of the wh-r535, wh-r540, wh-7700 & wh7701 for road.
what's the 6500 look like & what's its spoke count?

Did not seem to be any faster on those wheels,
and did not like the feel of the ride. Much happier with my 32 spoke
Open Pro w/ Ultegra hub wheels on the same bike; just as fast, easier
to change tires, wheels not quite so stiff, and lighter to boot. Felt
lucky that some suck..., er, rider was willing to pay me close to what
I paid for the wheels.

- rick

wrote:
Carl Fogel writes:


Are you saying that a wheel's spokes (two faintly conical
arrangements) present the same resistance to a crosswind whether the
spokes are rotating or motionless?


Yes.

Jobst Brandt


No. Lateral force from a crosswind is not independent of forward
speed, whether or not that forward speed results from being part
of a rotating wheel, or just moving with the whole bike.

Consider a vertical round rod. When stationary, but in a side wind
of 10 mph, some sideways force F results. If the rod is now moved
forward at 10 mph, the apparent wind is 14.14 mph, and the force
magnitude is now 2F, with a sideways component of 1.414F and a
backwards component of 1.414F. For a forward speed of 20 mph,
apparent wind is 22.36 mph, force magnitude is 5F, with a sideways
component of 2.236F and a backwards component of 4.472F.

In a spoked wheel, the results can't be so easily calculated, since
the spokes are somewhat in the wake behind the leading part of the
wheel, but there is no reason to suspect that this effect would
exactly cancel the increase in side force due to drag being
proportional to velocity squared.

Dave Lehnen

On Thu, 21 Oct 2004 21:38:11 -0700, jim beam
wrote:

Rick Warner wrote:
jim beam wrote in message ...


no it's not "blind", but we've done it 6 times during the course of this
summer with the results described. tim, bottom line, i'm not trying to
force these things down your throat - i'm merely voicing my experience.
based on that, yes, i'm confident there is a measurable difference if
i were to instrument the two sets of wheels, but as you know, i don't
work in the materials biz any more, so i can't say i have plans on
renting the equipment unless someone's paying me to do it. if you find
yourself here in the bay area some time, let me know and i'll loan you a
bike for a spin across the bridge. if you don't detect any difference,
at least you'll have enjoyed the view while trying.


I had a very different experience with the Ultegra version of the
wheelset, the 6500.

i'm only aware of the wh-r535, wh-r540, wh-7700 & wh7701 for road.
what's the 6500 look like & what's its spoke count?

Did not seem to be any faster on those wheels,
and did not like the feel of the ride. Much happier with my 32 spoke
Open Pro w/ Ultegra hub wheels on the same bike; just as fast, easier
to change tires, wheels not quite so stiff, and lighter to boot. Felt
lucky that some suck..., er, rider was willing to pay me close to what
I paid for the wheels.

- rick

Dear Jim,

Far down on this page:

http://www.changing-gear.com/acatalo...heels_188.html

Sixteen bladed spokes with a lubricating strip--er, sorry,
too many shaving commercials.

Rim height 30 mm.

The other wheels may be on the same page for comparison.

Carl Fogel

wrote:
On Thu, 21 Oct 2004 21:38:11 -0700, jim beam
wrote:


Rick Warner wrote:

jim beam wrote in message ...



no it's not "blind", but we've done it 6 times during the course of this
summer with the results described. tim, bottom line, i'm not trying to
force these things down your throat - i'm merely voicing my experience.
based on that, yes, i'm confident there is a measurable difference if
i were to instrument the two sets of wheels, but as you know, i don't
work in the materials biz any more, so i can't say i have plans on
renting the equipment unless someone's paying me to do it. if you find
yourself here in the bay area some time, let me know and i'll loan you a
bike for a spin across the bridge. if you don't detect any difference,
at least you'll have enjoyed the view while trying.


I had a very different experience with the Ultegra version of the
wheelset, the 6500.

i'm only aware of the wh-r535, wh-r540, wh-7700 & wh7701 for road.
what's the 6500 look like & what's its spoke count?


Did not seem to be any faster on those wheels,
and did not like the feel of the ride. Much happier with my 32 spoke
Open Pro w/ Ultegra hub wheels on the same bike; just as fast, easier
to change tires, wheels not quite so stiff, and lighter to boot. Felt
lucky that some suck..., er, rider was willing to pay me close to what
I paid for the wheels.

- rick


Dear Jim,

Far down on this page:

http://www.changing-gear.com/acatalo...heels_188.html

Sixteen bladed spokes with a lubricating strip--er, sorry,
too many shaving commercials.

Rim height 30 mm.

The other wheels may be on the same page for comparison.

Carl Fogel


thank you!