Understanding Wheel Building

HKEK wrote:
Might this be because the spoke line on the outside of the flange is
better and fewer fatigue failures occur on spokes outside the flange?

I don't see it. And considering Shimano's poor reputation with their
factory wheels, I wouldn't put too much stock in their recommendation.
If they can't be bothered to explain their rationale, then I can't be
bothered to follow directions that don't make sense.

BTW I didn't realize the post above was made early (thought I was on
the 2nd page). My apologies.

On Jan 3, 7:39*pm, Andre Jute wrote:
Ron Ruff wrote:
Tim McNamara wrote:
Do you have a copy of _The Bicycle Wheel_? *You'll find the analysis of
the effects of braking and pedaling on spoke tension in there.

You weren't addressing me, but in my version (2nd edition) disc and
hub brakes are not considered.

Is someone claiming that in the 3rd (latest) edition disc and hub
brakes are considered? I don't see anything specific about disc and
hub brakes.

But I do wonder if you cannot take the "drive force" indicated as a
proxy for a disc or hub brake. The brake force applied on the hub
would be the same as the drive force but in reverse, and the spokes on
each side are symmetrical backwards and forwards, not so?

Be tricky to handle this if you insist on realism (you don't always
stop pedalling fully before you brake -- will the spokes enunciate an
S and hiss sibilantly?) but it might do for a theoretical
approximation.

Andre Jute
Where are you when we need you, Dr de Bono?



Several
factors are involved, one of them being the much higher deceleration
that can be achieved by braking compared to acceleration by pedaling.

That is not true. Traction and endos will limit the forces due to
braking. And as I've shown in a much earlier thread on this forum,
even on a road bike if you have low gears, and apply maximum force to
the pedal, traction is likely again be the limiter... and they end up
being very close... and *not* trivial. Anyone with an understanding of
gear ratios and geometry can calculate this themselves.

Preamble to avoid flames: I am not an engineer and don't even play
one on T.V. With that said, this is how I see it. When I put force
to the rear wheel, the bike moves -- the force is turned in to forward
motion.. When I lock up my front disc, the force is transmitted in to
the wheel and is relieved only when the tire loses traction. It seems
to me that rear drive torque is different from front braking torque.
With my considerable weight, and on the steep hills that I descend on
my disc brake bike, I can put a lot of braking force in to the front
hub. -- Jay Beattie.

In article
,
Ron Ruff wrote:

Tim McNamara wrote:
Do you have a copy of _The Bicycle Wheel_? You'll find the
analysis of the effects of braking and pedaling on spoke tension in
there.

You weren't addressing me, but in my version (2nd edition) disc and
hub brakes are not considered.

They are by implication, Ron. The forces would be the same as those for
pedaling (just imagine you're looking at the wheel from the other side),
except larger in magnitude by quite a bit.

Several factors are involved, one of them being the much higher
deceleration that can be achieved by braking compared to
acceleration by pedaling.

That is not true. Traction and endos will limit the forces due to
braking. And as I've shown in a much earlier thread on this forum,
even on a road bike if you have low gears, and apply maximum force to
the pedal, traction is likely again be the limiter... and they end up
being very close... and *not* trivial. Anyone with an understanding
of gear ratios and geometry can calculate this themselves.

In 40+ years of riding bike, Ron, despite being 200+ pounds and quite
strong I've never spun a tire on clean pavement by pedaling, even in my
racing days when I was at my peak strength and fitness. Traction is not
the limiter IME as far as maximum pedaling torque is concerned. On the
other hand, I can exceed the traction limit or do an endo at will on all
my bikes while braking. One can decelerate a bike at about 0.6 g (the
generally accepted figure, although as Joe Riel has shown it may be
possible to reach 0.83 g if the rider repositions himself behind the
saddle- see link below) whereas very few if any cyclists can accelerate
a bike at 0.6 g, let alone 0.83 g. (As a comparison, Formula 1 cars are
reported to be able to brake at 5 g, accelerate at 2 g and corner at 4
g. Even in this situation, braking forces are much higher than
acceleration forces- and a Formula 1 car has about 1000 hp compared to
an elite cyclist's 0.8).

Perhaps you are talking about climbing up a 30% grade in a 20 x 28 gear
with 60 pounds of camping gear on your bike. You could generate quite a
bit of torque in a situation like that because the extra weight raises
the traction limit and reduces the risk of lifting the front wheel.
It's a pretty unusual situation, though.

http://www.industrializedcyclist.com...-pitchover.pdf

In article ,
_ wrote:

On Sat, 03 Jan 2009 17:15:34 -0600, Tim McNamara wrote:

In article ,
_ wrote:

On Sat, 03 Jan 2009 10:53:12 -0800, jim beam wrote:



braking torque increases spoke tension more than pedaling torque.

Wow.

Another revalation from the master.

There are now (at least) *two* kinds of torque, and one inceases
tension in spokes more than the other.

Like to see then math on that - so many inch-pounds of torque
increasing tension by x% if it's from braking, y% if it's from
pedaling.

How did those spokes get so smart, that they can tell braking
torque from pedaling torque.

Maybe they're magic Mavic spokes...y'know, modern materials and
superior technology or something.

Kind of like Doug's two kinds of being dead.

Do you have a copy of _The Bicycle Wheel_? You'll find the
analysis of the effects of braking and pedaling on spoke tension in
there. Several factors are involved, one of them being the much
higher deceleration that can be achieved by braking compared to
acceleration by pedaling. Another is how those forces are
addressed to the spokes (the force is applied to the hub with
pedaling and with hub brakes, to the rim with sidepull, dual pivot,
cantilever, direct-pull, etc. brakes).

Yup, first edition.

Are you agreeing with beamo that there are two kinds of torque?

Torque is torque. Not having seen "jim's" entire post, I don't know
where you got the "two kinds of torque" from. Torque from pedaling and
torque from a hub brake will be the same as far as the spokes are
concerned.

Look at the diagrams for pedaling forces. Forces from a hub brake would
be the same- just imagine that you are seeing that wheel from the other
side while braking. The forces from braking will be much higher than
those from pedaling in the vast majority of circumstances.

On Sun, 04 Jan 2009 11:25:33 -0600, Tim McNamara wrote:


Torque is torque. Not having seen "jim's" entire post, I don't know
where you got the "two kinds of torque" from. Torque from pedaling and
torque from a hub brake will be the same as far as the spokes are
concerned.

Not according to beamo (this was quoted in the post to which you replied):

"braking torque increases spoke tension more than pedaling torque."

On Sun, 04 Jan 2009 11:20:24 -0600, Tim McNamara
wrote:

In article
,
Ron Ruff wrote:

Tim McNamara wrote:
Do you have a copy of _The Bicycle Wheel_? You'll find the
analysis of the effects of braking and pedaling on spoke tension in
there.

You weren't addressing me, but in my version (2nd edition) disc and
hub brakes are not considered.

They are by implication, Ron. The forces would be the same as those for
pedaling (just imagine you're looking at the wheel from the other side),
except larger in magnitude by quite a bit.

Several factors are involved, one of them being the much higher
deceleration that can be achieved by braking compared to
acceleration by pedaling.

That is not true. Traction and endos will limit the forces due to
braking. And as I've shown in a much earlier thread on this forum,
even on a road bike if you have low gears, and apply maximum force to
the pedal, traction is likely again be the limiter... and they end up
being very close... and *not* trivial. Anyone with an understanding
of gear ratios and geometry can calculate this themselves.

In 40+ years of riding bike, Ron, despite being 200+ pounds and quite
strong I've never spun a tire on clean pavement by pedaling, even in my
racing days when I was at my peak strength and fitness. Traction is not
the limiter IME as far as maximum pedaling torque is concerned. On the
other hand, I can exceed the traction limit or do an endo at will on all
my bikes while braking. One can decelerate a bike at about 0.6 g (the
generally accepted figure, although as Joe Riel has shown it may be
possible to reach 0.83 g if the rider repositions himself behind the
saddle- see link below) whereas very few if any cyclists can accelerate
a bike at 0.6 g, let alone 0.83 g. (As a comparison, Formula 1 cars are
reported to be able to brake at 5 g, accelerate at 2 g and corner at 4
g. Even in this situation, braking forces are much higher than
acceleration forces- and a Formula 1 car has about 1000 hp compared to
an elite cyclist's 0.8).

Perhaps you are talking about climbing up a 30% grade in a 20 x 28 gear
with 60 pounds of camping gear on your bike. You could generate quite a
bit of torque in a situation like that because the extra weight raises
the traction limit and reduces the risk of lifting the front wheel.
It's a pretty unusual situation, though.

http://www.industrializedcyclist.com...-pitchover.pdf

Dear Tim & Ron,

Jobst on hub brake and pedal effect:

"Pedaling causes nonuniform torque that varies during the pedal stroke
and with rider effort. A hub brake, on the other hand, produces
uniform torque, but its torque still causes dynamic changes as the
wheel rolls. For a small-flange hub, torque from strong pedaling or
braking causes tension changes as large as plus and minus 5%."

-The Bicycle Wheel, 3rd edition, p. 22

A searchable 3rd edition makes it easier to find things. Anyone with a
question about what's in the text of the three editions can email me.

The passage quoted corrects previous editions, which used "10 kg"
instead of "5%", possibly a unit confusion (10 kg when 10 lbs was
meant for 5% on 200 lb spoke tension), or perhaps a plus/minus
confusion (+5 kgf and -5 kgf would have been a range of 10 kgf).

For the computations for figure 8, braking load, see table 2, page
134.

Cheers,

Carl Fogel

_ wrote:

On Sun, 04 Jan 2009 11:25:33 -0600, Tim McNamara wrote:


Torque is torque. Not having seen "jim's" entire post, I
don't know
where you got the "two kinds of torque" from. Torque from
pedaling and torque from a hub brake will be the same as far
as the spokes are concerned.

Not according to beamo (this was quoted in the post to which
you replied):

"braking torque increases spoke tension more than pedaling
torque."

To say that more than one phenomonen produces X in no way
implies that there is more than one kind of X (in other than
the question-begging sense of there being a difference in X's
history or origin).

John

In article ,
_ wrote:

On Sun, 04 Jan 2009 11:25:33 -0600, Tim McNamara wrote:


Torque is torque. Not having seen "jim's" entire post, I don't
know where you got the "two kinds of torque" from. Torque from
pedaling and torque from a hub brake will be the same as far as the
spokes are concerned.

Not according to beamo (this was quoted in the post to which you
replied):

"braking torque increases spoke tension more than pedaling torque."

Nits are being picked there and this is not helpful to understanding.

Tim McNamara wrote:
In 40+ years of riding bike, Ron, despite being 200+ pounds and quite
strong I've never spun a tire on clean pavement by pedaling, even in my
racing days when I was at my peak strength and fitness.

But have you tried? Lowest gear, going slow or stopped... now stomp on
the pedal with full force. This isn't "normal" pedaling, but then
locking up the front wheel and/or doing endos isn't normal braking on
a road bike either.

On a MTB where these things go to extremes, the gears are much lower,
and flirting with endos and front wheel skids are more common.

On Mon, 05 Jan 2009 06:17:41 +1100, John Henderson wrote:

_ wrote:

On Sun, 04 Jan 2009 11:25:33 -0600, Tim McNamara wrote:


Torque is torque. Not having seen "jim's" entire post, I
don't know
where you got the "two kinds of torque" from. Torque from
pedaling and torque from a hub brake will be the same as far
as the spokes are concerned.

Not according to beamo (this was quoted in the post to which
you replied):

"braking torque increases spoke tension more than pedaling
torque."

To say that more than one phenomonen produces X in no way
implies that there is more than one kind of X (in other than
the question-begging sense of there being a difference in X's
history or origin).


True.

And irrelevant - read beamo's post again, and you will see that he is not
saying that more than one phenomenon produces x, but that there are *two*
different types of that "phenomenon" (torque) which somehow are
distinguishable by the presumably sentient spokes.