Question on spoke tension

A quick question here. In a 3-cross lacing pattern, every spoke touches one
other spoke (at the third cross). Thinking through the mechanics of the
situation, it would appear to me that if both spokes are initially at the
same tension and you make a minor tweak (loosen or tighten) to one spoke,
that the change in tension will end up distributed nearly evenly across
both spokes. Is this correct?

On Sunday, June 8, 2014 9:13:12 PM UTC-7, Ralph Barone wrote:
A quick question here. In a 3-cross lacing pattern, every spoke touches one

other spoke (at the third cross). Thinking through the mechanics of the

situation, it would appear to me that if both spokes are initially at the

same tension and you make a minor tweak (loosen or tighten) to one spoke,

that the change in tension will end up distributed nearly evenly across

both spokes. Is this correct?

I think no, but some of the tension *is* distributed to
adjacent spokes and opposite spokes.

Actually, I think maybe *everything* relates to everything
else (ooooo, I can't wait to get to the quantum stuff in
my little Feynman books :-)

(This is all my "uneducated" sense - Std disclaimers apply,
YMMV, no deposit, no return, etc.)

On Sunday, June 8, 2014 9:42:32 PM UTC-7, Dan O wrote:
On Sunday, June 8, 2014 9:13:12 PM UTC-7, Ralph Barone wrote:

A quick question here. In a 3-cross lacing pattern, every spoke touches one



other spoke (at the third cross). Thinking through the mechanics of the



situation, it would appear to me that if both spokes are initially at the



same tension and you make a minor tweak (loosen or tighten) to one spoke,



that the change in tension will end up distributed nearly evenly across



both spokes. Is this correct?



I think no, but some of the tension *is* distributed...

(some of it inversely)

to

adjacent spokes and opposite spokes.



Actually, I think maybe *everything* relates to everything

else (ooooo, I can't wait to get to the quantum stuff in

my little Feynman books :-)



(This is all my "uneducated" sense - Std disclaimers apply,

YMMV, no deposit, no return, etc.)

On Mon, 09 Jun 2014 04:13:12 GMT, Ralph Barone
wrote:

A quick question here. In a 3-cross lacing pattern, every spoke touches one
other spoke (at the third cross). Thinking through the mechanics of the
situation, it would appear to me that if both spokes are initially at the
same tension and you make a minor tweak (loosen or tighten) to one spoke,
that the change in tension will end up distributed nearly evenly across
both spokes. Is this correct?

Nope. As I understand it, if you tighten one spoke, you change both
the spoke tension and apply rotational tension (torque) to the hub.
The hub will try to rotate very slightly in the direction of the
increased tension, resulting in an increase in tension to the spokes
radiating from the hub in the opposite direction. There will
simulaneously be a decrease in tension in the spokes going the same
direction as the tighened spoke. The tension in all the spokes in one
direction MUST equal the tension in all the spokes going in the other
direction. Tighten one spoke, and they all change tension.

You can verify this effect by measuring the pitch of the spokes when
plucked. I haven't tried either of these:
https://itunes.apple.com/us/app/spoke-tension-gauge/id518870820?mt=8
https://play.google.com/store/apps/details?id=jp.gr.java_conf.MagokoroStudio.checkspo ke
Change tension on ANY spoke, pluck any other spoke, and you should
hear (or see) a slight change in pitch.


--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On Monday, June 9, 2014 7:17:55 AM UTC+1, Jeff Liebermann wrote:
On Mon, 09 Jun 2014 04:13:12 GMT, Ralph Barone

wrote:



A quick question here. In a 3-cross lacing pattern, every spoke touches one

other spoke (at the third cross). Thinking through the mechanics of the

situation, it would appear to me that if both spokes are initially at the

same tension and you make a minor tweak (loosen or tighten) to one spoke,

that the change in tension will end up distributed nearly evenly across

both spokes. Is this correct?



Nope. As I understand it, if you tighten one spoke, you change both

the spoke tension and apply rotational tension (torque) to the hub.

The hub will try to rotate very slightly in the direction of the

increased tension, resulting in an increase in tension to the spokes

radiating from the hub in the opposite direction. There will

simulaneously be a decrease in tension in the spokes going the same

direction as the tighened spoke. The tension in all the spokes in one

direction MUST equal the tension in all the spokes going in the other

direction. Tighten one spoke, and they all change tension.



You can verify this effect by measuring the pitch of the spokes when

plucked. I haven't tried either of these:

https://itunes.apple.com/us/app/spoke-tension-gauge/id518870820?mt=8

https://play.google.com/store/apps/details?id=jp.gr.java_conf.MagokoroStudio.checkspo ke

Change tension on ANY spoke, pluck any other spoke, and you should

hear (or see) a slight change in pitch.

Way I read Jobst's book The Bicycle Wheel, Jeff's got it right, you can't change tension in any spoke in isolation, which is what Ralph really wants to know.

Took a look at the spoke tension app on iTunes -- thanks for the link, Jeff -- but even for Euro 4.49 I don't think so. It isn't simple at all; you need too much information to feed the thing first; it isn't generic: it is linked to very particular setups, and you can bet none of those "popular" setups are on any bike I be seen dead owning. In any event a simple tension gauge that works on every spoke and that everyone can understand, and that doesn't need a ton of extraneous input, is generally available and doesn't in the scheme of a decent bicycle cost all that much:
http://www.chainreactioncycles.com/i...q=park+tension

Interesting thread, Ralph.

Andre Jute
Precision engineering: track control arms on a Porsche designed to flex

On 6/8/2014 11:13 PM, Ralph Barone wrote:
A quick question here. In a 3-cross lacing pattern, every spoke touches one
other spoke (at the third cross). Thinking through the mechanics of the
situation, it would appear to me that if both spokes are initially at the
same tension and you make a minor tweak (loosen or tighten) to one spoke,
that the change in tension will end up distributed nearly evenly across
both spokes. Is this correct?


Yes, any tension change affects the entire wheel to some
extent. The total tension change from one spoke moved 1/2
turn (1/112 of an inch) is minuscule, but exists. The change
to the adjacent laced spoke is probably more than to the
others as you suspect but I haven't found that to be
significant.

--
Andrew Muzi
www.yellowjersey.org/
Open every day since 1 April, 1971

On 6/9/2014 12:13 AM, Ralph Barone wrote:
A quick question here. In a 3-cross lacing pattern, every spoke touches one
other spoke (at the third cross). Thinking through the mechanics of the
situation, it would appear to me that if both spokes are initially at the
same tension and you make a minor tweak (loosen or tighten) to one spoke,
that the change in tension will end up distributed nearly evenly across
both spokes. Is this correct?

I think Jeff's response is correct - that changing one spoke's tension
results in changes in all the other spokes' tensions. But two things to
note:

First, the tension change in those other spokes will be much smaller
than the tension change applied to the spoke by the spoke wrench. The
reaction gets shared, so to speak.

Second, it seems that Ralph is visualizing a different effect, an
interaction between only the two spokes that actually touch. I think
that effect would be due only to the minuscule change in the angle of
the bends at the contact point. I think any tension change generated
that way would be practically undetectable. IOW, I think the tension
change in the touching spoke would be no different than the tension
change in any other spoke on the same side of the wheel.

--
- Frank Krygowski

On Mon, 09 Jun 2014 11:01:57 -0400, Frank Krygowski
wrote:

Second, it seems that Ralph is visualizing a different effect, an
interaction between only the two spokes that actually touch. I think
that effect would be due only to the minuscule change in the angle of
the bends at the contact point. I think any tension change generated
that way would be practically undetectable. IOW, I think the tension
change in the touching spoke would be no different than the tension
change in any other spoke on the same side of the wheel.

Yep. Working it backwards, if there were an effect due to the
crossing of the spokes, the tension on either side of the points of
contact would need to be different. That's obviously not the case due
to the lack of friction between spokes at the point of crossing. Even
if the spokes were tied at the point of crossing, there would be no
direct effect (except for a lateral change in tension as Frank
mentioned). However, if the spokes were welded together at the points
of contact, there would certainly be a tension change in the formerly
crossed spokes. Also, if there was a direct effect on the tension of
the crossed spokes, the standard 3 point tension gauge would not work
because it relies on the tension being constant over the entire length
of the spoke.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On Monday, June 9, 2014 8:01:57 AM UTC-7, Frank Krygowski wrote:
On 6/9/2014 12:13 AM, Ralph Barone wrote:

A quick question here. In a 3-cross lacing pattern, every spoke touches one

other spoke (at the third cross). Thinking through the mechanics of the

situation, it would appear to me that if both spokes are initially at the

same tension and you make a minor tweak (loosen or tighten) to one spoke,

that the change in tension will end up distributed nearly evenly across

both spokes. Is this correct?



I think Jeff's response is correct - that changing one spoke's tension

results in changes in all the other spokes' tensions. But two things to

note:



First, the tension change in those other spokes will be much smaller

than the tension change applied to the spoke by the spoke wrench. The

reaction gets shared, so to speak.



Second, it seems that Ralph is visualizing a different effect, an

interaction between only the two spokes that actually touch. I think

that effect would be due only to the minuscule change in the angle of

the bends at the contact point. I think any tension change generated

that way would be practically undetectable. IOW, I think the tension

change in the touching spoke would be no different than the tension

change in any other spoke on the same side of the wheel.


Take a strong sedative, sit down, cross your legs, close
your eyes, and meditate. (Or just fondle a wheel - squeeze
some spoke pairs... squeeze *pairs* of spoke pairs at
different distances to get the feel - until it comes to you.)

If you tighten a spoke, the ~directly opposite spoke will
tighten ~equally. Spokes adjacent to that spoke will tighten
also, but progressively less until you come to the spokes
on the same side of the rim, where they will have progressively
*lost* tension as you come around to the spoke you tightened
with the wrench.

The tension change is a function of the angle relative to the
"tightened" spoke.

That's an oversimplification, but closer, I think.

On Monday, June 9, 2014 9:52:04 AM UTC-7, Dan O wrote:
On Monday, June 9, 2014 8:01:57 AM UTC-7, Frank Krygowski wrote:

On 6/9/2014 12:13 AM, Ralph Barone wrote:



A quick question here. In a 3-cross lacing pattern, every spoke touches one



other spoke (at the third cross). Thinking through the mechanics of the



situation, it would appear to me that if both spokes are initially at the



same tension and you make a minor tweak (loosen or tighten) to one spoke,



that the change in tension will end up distributed nearly evenly across



both spokes. Is this correct?







I think Jeff's response is correct - that changing one spoke's tension



results in changes in all the other spokes' tensions. But two things to



note:







First, the tension change in those other spokes will be much smaller



than the tension change applied to the spoke by the spoke wrench. The



reaction gets shared, so to speak.







Second, it seems that Ralph is visualizing a different effect, an



interaction between only the two spokes that actually touch. I think



that effect would be due only to the minuscule change in the angle of



the bends at the contact point. I think any tension change generated



that way would be practically undetectable. IOW, I think the tension



change in the touching spoke would be no different than the tension



change in any other spoke on the same side of the wheel.





Take a strong sedative, sit down, cross your legs, close

your eyes, and meditate. (Or just fondle a wheel - squeeze

some spoke pairs... squeeze *pairs* of spoke pairs at

different distances to get the feel - until it comes to you.)



If you tighten a spoke, the ~directly opposite spoke will

tighten ~equally. Spokes adjacent to that spoke will tighten

also, but progressively less until you come to the spokes

on the same side of the rim, where they will have progressively

*lost* tension as you come around to the spoke you tightened

with the wrench.



The tension change is a function of the angle relative to the

"tightened" spoke.



That's an oversimplification, but closer, I think.

.... all this on only one side of the hub, of course.

It's probably best not to think too hard about it, to
just let things go, and...

Be the wheel.