14/15/14 vs. straight-gauge 15

David Damerell wrote in message ...
Michael wrote:
(Qui si parla Campagnolo) wrote
Should be 36 hole(at least the rear) and 14/15, built well, of course.
Why 36 holes?

It's the most robust equipment that is available without a significant
price penalty. Why _not_ 36 holes, eh?

Why not 24 holes? Why not 48 holes? etc.

I look for components that perform well while being as light as
possible while being sufficiently durable for my application. It's
also nice if they are standard sizes for easy replacement and/or
swapping between my bikes. If that means a wheel with 24 or 32 or 36
or 48 spokes, I don't care, but I was asking if anyone has valid
analytical or anecdotal reasons for one over the other.

Michael wrote:
David Damerell :
Michael wrote:
(Qui si parla Campagnolo) wrote
Should be 36 hole(at least the rear) and 14/15, built well, of course.
Why 36 holes?
It's the most robust equipment that is available without a significant
price penalty. Why _not_ 36 holes, eh?
Why not 24 holes? Why not 48 holes? etc.

Not 24 because it is less robust. Not 48 because it is more expensive and
requires larger hub flanges, which is starting to take the weight penalty
into the realms of the meaningful as well as making it less likely that
spares will be readily available.

I look for components that perform well while being as light as
possible while being sufficiently durable for my application.

Wheel failures certainly still happen, so I think we can say that an
increase in wheel durability that does not carry a significant penalty is
always good. That's true when going from any number 36 to 36, where the
weight penalty is practically nothing, but it's not true when going above
36 because the equipment is significantly more expensive.

I was asking if anyone has valid
analytical or anecdotal reasons for one over the other.

As you can see, I do.
--
David Damerell Distortion Field!

Michael Press writes:

Why 36 holes?

It's the most robust equipment that is available without a
significant price penalty. Why _not_ 36 holes, eh?

Why not 24 holes? Why not 48 holes? etc.

I'm glad you asked. There is a best ratio between rim cross section,
spoke diameter and number of spokes. As the spoke count is reduced,
spoke tension must be increased to prevent slackening in use. This
demands a greater rim strength in bending to bridge between spokes and
it requires a stronger rim bed to prevent spoke pull-outs. At the
other end, hubs must be made stronger to retain higher spoke tension.

Since spoke tension is limited by the circumferential compressive
strength of the rim, more spokes don't hurt although they cannot be as
tight as fewer spokes, but they can support a greater load because it
is distributed among more spokes. That is why 48 spokes have served
tandems well for those willing to ignore the fad of fewer spokes. It
boils down to how many spokes per length of rim and for 700c rims it
comes down to 36.

All this was developed from over 100 years of trial and error, back in
the days when the bicycle was an important transportation vehicle and
racers were not rich professional athletes who could afford replacing
wheels that failed readily. Of course this doesn't affect riders who
ride mainly new wheels and several sets of them.

I look for components that perform well while being as light as
possible while being sufficiently durable for my application. It's
also nice if they are standard sizes for easy replacement and/or
swapping between my bikes. If that means a wheel with 24 or 32 or
36 or 48 spokes, I don't care, but I was asking if anyone has valid
analytical or anecdotal reasons for one over the other.

I'm glad to see you qualify that with "for my application".
That puts a different spin on it.

Jobst Brandt

Palo Alto CA

Till Rosenband writes:

It's the most robust equipment that is available without a
significant price penalty. Why _not_ 36 holes, eh?

Why not 24 holes? Why not 48 holes? etc.

I'm glad you asked. There is a best ratio between rim cross
section, spoke diameter and number of spokes. As the spoke count
is reduced, spoke tension must be increased to prevent slackening
in use. This demands a greater rim strength in bending to bridge
between spokes and it requires a stronger rim bed to prevent spoke
pull-outs. At the other end, hubs must be made stronger to retain
higher spoke tension.

Since spoke tension is limited by the circumferential compressive
strength of the rim, more spokes don't hurt although they cannot be
as tight as fewer spokes, but they can support a greater load
because it is distributed among more spokes. That is why 48 spokes
have served tandems well for those willing to ignore the fad of
fewer spokes. It boils down to how many spokes per length of rim
and for 700c rims it comes down to 36.

All this was developed from over 100 years of trial and error, back
in the days when the bicycle was an important transportation
vehicle and racers were not rich professional athletes who could
afford replacing wheels that failed readily. Of course this
doesn't affect riders who ride mainly new wheels and several sets
of them.

You write that for regular bikes 36 holes are optimal, and "48
spokes have served tandems well". I'm curious how the optimum spoke
count scales with load. I think it's reasonable to assume that the
tandem's wheels will carry twice the load of the 36 spoke wheels.
Yet they only have 1/3 more spokes. I would expect a 48 spoke wheel
to serve two riders about as "well" as a 24 spoke wheel serves one.

It is a matter of how many spoke fall in the load affected zone ad
that is not linear with load. I'm not saying that 48 spoke tandem
wheels are optimal, only that there is benefit in that number of
spokes using otherwise conventional dim profiles. I'm sure a better
cross section could be achieved for tandems.

Imagine a 24 spoke wheel that is sitting on the floor and is
carrying 100 lbs. It is bent out of round a bit to accommodate the
load. If we now double the spoke count while simultaneously
doubling the load, nothing should move. That's assuming the rim
really acts like a wet noodle, the way you describe it in your book
"The Bicycle Wheel". Even if rim rigidity played a role, the tandem
rim might be twice as strong as the regular one, so I would expect
the tandem wheel carrying 200 lbs to look very similar to the 24
spoke wheel carrying 100 lbs. Hence the cyclical stresses will be
similar in 48 spoke tandem wheels and 24 spoke regular wheels, and
their durability should be the same, too.

I've never ridden a tandem. Are 48 spoke wheels considered durable?
Does anyone feel the need for more spokes?

I started the 48 spoke concept with Spence Wolf of Cupertino Bike Shop
when tandems in the 1950's suffered spoke and rim failures at a great
rate. In those days one cold request rims with different drillings.
In any case, the wheels made a big difference and have been used by
average sized tandem riders who travel.

Jobst Brandt

Palo Alto CA

"Gary Kamieneski" wrote in message
om...

This one will get quickly shot down but as at least two people here
are eminently more qualified to address the science, but I've always
contended that the 32h wheel was stronger because the spoke count was
Base 2. Just for consideration, note how the 32h wheel has 8 pairs of
spokes on each side rather than 9 pairs. My theory is that this
allows more equal opposing longitudinal forces while sharing the
opposition to latitudinal forces that the 9 pairs do on the 36h wheel.
Wait,...let me put my helmet on.

That's not so at all. The fact is, 32 spoke wheels have only become
feasible since rims were welded at the seam. With unwelded rims, if you
lace 32 spokes and leave a gap at the valve hole for your pump, then you
leave a corresponding gap at the seam, which of course pulls the seam apart
straight away. With 36 spokes (or 28 for that matter) the spokes either
side of the seam pull it together. Of course now, with welded rims, you're
relying on that weld not letting go.

That's the _real_ reason the experts advocate 36 spoke rims.

Regards,

Suzy (tongue firmly planted in cheek)

Suzy Jackson writes:

This one will get quickly shot down but as at least two people here
are eminently more qualified to address the science, but I've
always contended that the 32h wheel was stronger because the spoke
count was Base 2. Just for consideration, note how the 32h wheel
has 8 pairs of spokes on each side rather than 9 pairs. My theory
is that this allows more equal opposing longitudinal forces while
sharing the opposition to latitudinal forces that the 9 pairs do on
the 36h wheel. Wait,...let me put my helmet on.

That's not so at all. The fact is, 32 spoke wheels have only become
feasible since rims were welded at the seam. With unwelded rims, if
you lace 32 spokes and leave a gap at the valve hole for your pump,
then you leave a corresponding gap at the seam, which of course
pulls the seam apart straight away. With 36 spokes (or 28 for that
matter) the spokes either side of the seam pull it together. Of
course now, with welded rims, you're relying on that weld not
letting go.

That's the _real_ reason the experts advocate 36 spoke rims.

I take it you say that in jest, yet it is amazing how popular that
belief was for all the years before a stress analysis was published.
The number of bicycle shop owners and mechanics that do not read and
are unaware that some of their their customers are better informed
about wheels than they are, amazes me. I recently overheard your
comment about spoke patterns in a bicycle shop.

On that subject, Fiamme rims used a rivet on either side of the butt
joint and then for a long time had none before reverting to rivets in
their waning days. No MA-2 rims (of which I have a reasonable cache)
have anything holding them together at the joint except friction from
the alignment insert. These shenanigans, among others, moved me to
write "the Bicycle Wheel."

http://www.avocet.com/wheelbook/wheelbook.html

Jobst Brandt

Palo Alto CA

their waning days. No MA-2 rims (of which I have a reasonable cache)
have anything holding them together at the joint except friction from
the alignment insert.

jobst, i think they are jointed by diffusion welding. it's a common
solid-phase method of joining aluminum.

jb

jim beam writes:

their waning days. No MA-2 rims (of which I have a reasonable
cache) have anything holding them together at the joint except
friction from the alignment insert.

Jobst, I think they are jointed by diffusion welding. It's a common
solid-phase method of joining aluminum.

The joint can be pulled apart by hand to expose a well fitting sleeve.
Pleas explain how my rims could be diffusion welded, these or the
Fiamme rims remaining from the days of tubulars.

Jobst Brandt

Palo Alto CA

relax

i said "i think" because some rims were and my ma2 looks similar to
those examples. i do not however plan on pulling my ma2 apart just to
argue with you.

have a beer. go to bed.

diffusion welding is really cool though.



wrote:
jim beam writes:


their waning days. No MA-2 rims (of which I have a reasonable
cache) have anything holding them together at the joint except
friction from the alignment insert.


Jobst, I think they are jointed by diffusion welding. It's a common
solid-phase method of joining aluminum.


The joint can be pulled apart by hand to expose a well fitting sleeve.
Pleas explain how my rims could be diffusion welded, these or the
Fiamme rims remaining from the days of tubulars.

Jobst Brandt

Palo Alto CA

Gary- This one will get quickly shot down but as at least two people here
are eminently more qualified to address the science, but I've always
contended that the 32h wheel was stronger because the spoke count was
Base 2. Just for consideration, note how the 32h wheel has 8 pairs of
spokes on each side rather than 9 pairs. BRBR

Right and a compact frameset is stiffer...

As are integrated HS...


Peter Chisholm
Vecchio's Bicicletteria
1833 Pearl St.
Boulder, CO, 80302
(303)440-3535
http://www.vecchios.com
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