Need Jobst (and anyone else's) help: Twisted-spoke damping factor



On 5 Dec 2004 01:29:36 -0800, [email protected] (papercut)
wrote:

>From a recent post elsewhere:
>
>>citing gerd schraner from his book "the art of wheelbuilding" --

>
>>the twisting of spokes, instead of classic crossing work is a waste

>of time for >road use. tests have shown that it results in a very
>unstable wheel. the >lateral stability is about the same as a
>normally spoked wheel, but radially the >wheel reacts so sluggishly
>that encounters with momentary radial overloads the >highly praised
>damping effect is delayed. ... twisted spoking patterns are an
>>additional mechanical disadvantage resulting from the extreme angle

>of the spoke >directly at the nipple. (schraner, p. 60)
>
>So, there is a claim that wheels with twisted spokes have a
>significantly different "damping factor" than normally laced wheels.
>The above quote given as evidence.
>
>It is also claimed that this "damping factor" inherent in
>twisted-spoke wheels are good for trials riding. This conclusion
>deduced somehow.
>
>
>Sounds like a lot of pseudoscience to me. What's the scoop on this?


And yet another set of twisted spokes, this one a unicycle:

http://www.xs4all.nl/~klaasbil/107_0755.JPG

Note that these use the double twist that distinguishes mere
chain-link from chicken-wire.

I doubt that I'll find four spokes twisted together, but
maybe some daring soul has gone to a triple twist?

Carl Fogel
 
L

Leo Lichtman

Guest
<[email protected]> wrote: Note that these use the double twist that
distinguishes mere chain-link from chicken-wire. I doubt that I'll find four
spokes twisted together, but maybe some daring soul has gone to a triple
twist?
^^^^^^^^^^^^^^
I have a "concept" wheel which actually uses chain link fencing in place of
spokes, but my computer ability does not include Photoshop, so I haven't
been able to build it. Maybe someone else can help out here.
 
On Wed, 8 Dec 2004 16:23:15 +1100, waxbytes
<[email protected]> wrote:

>
>How's about this "Twisted Spoke Wheel"?
>
>Wrong type of 'bike' is all.
>
>
>+-------------------------------------------------------------------+
>|Filename: wheels-Chromed60GoldSpokeTwisted.jpg |
>|Download: http://www.cyclingforums.com/attachment.php?attachmentid=2495|
>+-------------------------------------------------------------------+


Dear WB,

Those purely cosmetic spiral spokes make it hard to google
for the truly intertwined ones.

It would be interesting to learn if the process of creating
the cosmetic twisting has any ill effects on these gaudy
straight spokes.

Does the metal-working leave strains that lead to spokes
breaking? Do the artistic sharp edges and corners act as
stress risers?

And what happens where such spokes cross each other? Your
example is a little unusual in that it uses a cross-spoke
pattern. Most of the ones that I saw while searching for
snowflake wheels used a radial pattern to avoid chafing of
the irregular twisted surfaces.

Carl Fogel
 
W

Werehatrack

Guest
On 5 Dec 2004 01:29:36 -0800, [email protected] (papercut)
wrote:

>From a recent post elsewhere:
>
>>citing gerd schraner from his book "the art of wheelbuilding" --

>
>>the twisting of spokes, instead of classic crossing work is a waste

>of time for >road use. tests have shown that it results in a very
>unstable wheel. the >lateral stability is about the same as a
>normally spoked wheel, but radially the >wheel reacts so sluggishly
>that encounters with momentary radial overloads the >highly praised
>damping effect is delayed. ... twisted spoking patterns are an
>>additional mechanical disadvantage resulting from the extreme angle

>of the spoke >directly at the nipple. (schraner, p. 60)
>
>So, there is a claim that wheels with twisted spokes have a
>significantly different "damping factor" than normally laced wheels.
>The above quote given as evidence.
>
>It is also claimed that this "damping factor" inherent in
>twisted-spoke wheels are good for trials riding. This conclusion
>deduced somehow.
>
>
>Sounds like a lot of pseudoscience to me. What's the scoop on this?


Dear PC,

Tucked away in all the theorizing below is the first actual
observation that I've found about a snowflake wheel in
action, from a unicyclist:

"My friend Jason has a MUni with twisted spokes. I did a
double take when I first saw it ans asked what was up with
the wheel. He said he bought the spokes too long and didn't
want to bother returning them!"

"As for strength, in theory the wheel could go either way.
When pulled tight, the twists in the spokes will shorten,
then lengthen. This could add some springiness to the wheel
(making it more robust in the long run), but the movement of
the spokes could cause the to weaken at the twist and
possibly break. In practice, the untensioning of the
bottom spokes is a much bigger factor than tighhtening of
the top ones. In any case, Jason's wheel creaks and groans
when he rides, so the spokes are indeed moving."

http://www.unicycle-forum.com/unicycling/Spoke_patternswhy_do_this_108028.html

The creaking and groaning from a unicycle wheel doesn't
sound (pun intended) reassuring.

Buying too-long spokes seems to be a common reason for this
strange spoke pattern:

http://groups-beta.google.com/group..._doneTitle=Back+to+Search&&d#73d77100b9de61c1
or http://tinyurl.com/44snj

Carl Fogel
 
Carl Fogel writes:

> Tucked away in all the theorizing below is the first actual
> observation that I've found about a snowflake wheel in action, from
> a unicyclist:


> "My friend Jason has a MUni with twisted spokes. I did a double
> take when I first saw it and asked what was up with the wheel. He
> said he bought the spokes too long and didn't want to bother
> returning them!"


> "As for strength, in theory the wheel could go either way. When
> pulled tight, the twists in the spokes will shorten, then lengthen.
> This could add some springiness to the wheel (making it more robust
> in the long run), but the movement of the spokes could cause them to
> weaken at the twist and possibly break. In practice, the
> untensioning of the bottom spokes is a much bigger factor than
> tighhtening of the top ones. In any case, Jason's wheel creaks and
> groans when he rides, so the spokes are indeed moving."


> http://www.unicycle-forum.com/unicycling/Spoke_patternswhy_do_this_108028.html


The item above about the untensioning of bottom spokes is telling.
That has little to do with sprinyness since deflections are amazingly
small (in the few 0.001") so the upshot is that it shortens fatigue
life... but then how many miles does a unicycle get?

> The creaking and groaning from a unicycle wheel doesn't sound (pun
> intended) reassuring.


I'd like to hear that.

> Buying too-long spokes seems to be a common reason for this strange
> spoke pattern:


If you believe that baloney you'll believe most any dodge. Can you
imagine how a spoke that is too long can be made right by this method.
Consider that spoke lengths need to be within 2mm of the right length
to work reasonably. What are the chances that a spoke that was bought
for a specific wheel and was found to be a little too long would reach
the rim if wrapped around an adjacent spoke?

My take is that those who use this excuse are embarrassed that they
built such a wheel and want to pass it of as something that had to be
done that way rather than by choice.

Jobst Brandt
[email protected]
 
On Wed, 08 Dec 2004 19:22:15 GMT,
[email protected] wrote:

>Carl Fogel writes:
>
>> Tucked away in all the theorizing below is the first actual
>> observation that I've found about a snowflake wheel in action, from
>> a unicyclist:

>
>> "My friend Jason has a MUni with twisted spokes. I did a double
>> take when I first saw it and asked what was up with the wheel. He
>> said he bought the spokes too long and didn't want to bother
>> returning them!"

>
>> "As for strength, in theory the wheel could go either way. When
>> pulled tight, the twists in the spokes will shorten, then lengthen.
>> This could add some springiness to the wheel (making it more robust
>> in the long run), but the movement of the spokes could cause them to
>> weaken at the twist and possibly break. In practice, the
>> untensioning of the bottom spokes is a much bigger factor than
>> tighhtening of the top ones. In any case, Jason's wheel creaks and
>> groans when he rides, so the spokes are indeed moving."

>
>> http://www.unicycle-forum.com/unicycling/Spoke_patternswhy_do_this_108028.html

>
>The item above about the untensioning of bottom spokes is telling.
>That has little to do with sprinyness since deflections are amazingly
>small (in the few 0.001") so the upshot is that it shortens fatigue
>life... but then how many miles does a unicycle get?
>
>> The creaking and groaning from a unicycle wheel doesn't sound (pun
>> intended) reassuring.

>
>I'd like to hear that.
>
>> Buying too-long spokes seems to be a common reason for this strange
>> spoke pattern:

>
>If you believe that baloney you'll believe most any dodge. Can you
>imagine how a spoke that is too long can be made right by this method.
>Consider that spoke lengths need to be within 2mm of the right length
>to work reasonably. What are the chances that a spoke that was bought
>for a specific wheel and was found to be a little too long would reach
>the rim if wrapped around an adjacent spoke?
>
>My take is that those who use this excuse are embarrassed that they
>built such a wheel and want to pass it of as something that had to be
>done that way rather than by choice.
>
>Jobst Brandt
>[email protected]


Dear Jobst,

James Annan has explained that no spokes of the right length
were available when he ruined a wheel on a trip and that's
why he used the odd lacing.

Your familiar paranoid theory that people must be lying is
even less convincing than usual in this case. If they're
embarrassed as you claim, why are they taking the trouble to
tell everyone and post pictures of their shame?

Carl Fogel
 
On Wed, 08 Dec 2004 19:22:15 GMT,
[email protected] wrote:

[snip]

>Can you
>imagine how a spoke that is too long can be made right by this method.
>Consider that spoke lengths need to be within 2mm of the right length
>to work reasonably. What are the chances that a spoke that was bought
>for a specific wheel and was found to be a little too long would reach
>the rim if wrapped around an adjacent spoke?


[snip]

>Jobst Brandt
>[email protected]


Dear Jobst,

Actually, the odds look pretty good when I measure the three
sections of a double-twisted spoke, add them up, and compare
them to the straight-line distance with a graphics ruler
program: http://www.markus-bader.de/MB-Ruler/

For the unicycle picture on my screen, a straight spoke from
hub to nipple looks like about 142 units, while the three
sections of the double twisted spoke look like 64+35+47=146
units:

http://www.xs4all.nl/~klaasbil/107_0755.JPG

For the Australian snowflake wheel on my screen, a straight
spoke looks like about 112 units, while the three sections
of the double-twisted spoke look like 30+21+63=114 units.

http://www.ozbizz.com/melton/kensbikes/snowflake.htm

My measurements are hardly exact, but the weird twisting
pattern seems to require only slightly longer spokes than a
normal pattern--and there are plenty of posts on
rec.bicycles.tech from people who have spokes that are close
to the right size, but not close enough.

So if the spokes are just a few millimeters too long to work
in a normal pattern, then the strange twisted spoke pattern
might well let you use them. (Your 2 mm minimum strikes me
as a bit low.)

And if they're still just a little too long with a single
twist, then a double twist might adjust things. So far, I
haven't found anything about how to calculate the required
spoke length for these oddball lacing patterns.

Thanks for leading me to do some actual measuring--until I
thought about it, I assumed that the spokes would have to be
much, much longer to make the twisted pattern work, but it
looks as if just a little longer is enough.

Carl Fogel
 
J

Jay Beattie

Guest
<[email protected]> wrote in message
news:[email protected]
> On Wed, 08 Dec 2004 19:22:15 GMT,


[big snip]

> So if the spokes are just a few millimeters too long to work
> in a normal pattern, then the strange twisted spoke pattern
> might well let you use them. (Your 2 mm minimum strikes me
> as a bit low.)


Or you could just do the reasonable thing and increase the spoke
cross, but I guess that would be too easy. Note that the
snowflake wheel is only three cross (from what I can tell). Same
with the unicycle wheel. Going from three to four cross on a 700c
wheel would add almost 8mm to the spoke length, and going five
cross would add about 15mm. Only after about the 20mm mark would
the "oops, I bought the wrong length spoke" seem to justify a
twisted spoke pattern -- and that assumes that with a three cross
700c wheel, 20mm reasonably can be taken up with a twist or
two. -- Jay Beattie.
 
J

Jim Smith

Guest
"Jay Beattie" <[email protected]> writes:

> Or you could just do the reasonable thing and increase the spoke
> cross, but I guess that would be too easy. Note that the
> snowflake wheel is only three cross (from what I can tell). Same
> with the unicycle wheel. Going from three to four cross on a 700c
> wheel would add almost 8mm to the spoke length, and going five
> cross would add about 15mm. Only after about the 20mm mark would
> the "oops, I bought the wrong length spoke" seem to justify a
> twisted spoke pattern -- and that assumes that with a three cross
> 700c wheel, 20mm reasonably can be taken up with a twist or
> two. -- Jay Beattie.



Five times twenty degrees is 100, so if you have a 36 hole hub cross
five is going to be troublesome.
 
On Wed, 8 Dec 2004 14:08:54 -0800, "Jay Beattie"
<[email protected]> wrote:

>
><[email protected]> wrote in message
>news:[email protected]
>> On Wed, 08 Dec 2004 19:22:15 GMT,

>
>[big snip]
>
>> So if the spokes are just a few millimeters too long to work
>> in a normal pattern, then the strange twisted spoke pattern
>> might well let you use them. (Your 2 mm minimum strikes me
>> as a bit low.)

>
>Or you could just do the reasonable thing and increase the spoke
>cross, but I guess that would be too easy. Note that the
>snowflake wheel is only three cross (from what I can tell). Same
>with the unicycle wheel. Going from three to four cross on a 700c
>wheel would add almost 8mm to the spoke length, and going five
>cross would add about 15mm. Only after about the 20mm mark would
>the "oops, I bought the wrong length spoke" seem to justify a
>twisted spoke pattern -- and that assumes that with a three cross
>700c wheel, 20mm reasonably can be taken up with a twist or
>two. -- Jay Beattie.


Dear Jay,

I'm not sure that "reasonable" or "justify" are exactly the
kind of words running through the minds of people who build
snowflake wheels.

I assume that your 8mm increase for 3 to 4 cross normal
lacing is roughly correct, so for spokes 8mm too long, going
to 4 cross would seem reasonable.

But I think that the twisted spoke trick is actually for
shorter mismatches--that is, spokes too long for normal 3
cross, but too short for 4 cross.

When I measured the spokes in the pictures, the crossed
spokes seemed to be only slightly longer than a straight
run. And that was for small wheels, where the angles are
greater. For 700c wheels, the crossing takes place
relatively closer to the hub and requires an even smaller
increase in spoke length.

Or so I think. I haven't found a spoke-length calculator for
twisted spokes and their variants. I may experiment with a
spare wheel and some string to see what the actual length
differences are.

Carl Fogel
 
B

Benjamin Lewis

Guest
[email protected] wrote:

> Or so I think. I haven't found a spoke-length calculator for
> twisted spokes and their variants. I may experiment with a
> spare wheel and some string to see what the actual length
> differences are.


If you do this, try to find string that similar in thickness to a spoke,
since this will make a difference in the winding portion.

--
Benjamin Lewis

Seeing is deceiving. It's eating that's believing.
-- James Thurber
 
On Wed, 08 Dec 2004 16:00:02 -0800, Benjamin Lewis
<[email protected]> wrote:

>[email protected] wrote:
>
>> Or so I think. I haven't found a spoke-length calculator for
>> twisted spokes and their variants. I may experiment with a
>> spare wheel and some string to see what the actual length
>> differences are.

>
>If you do this, try to find string that similar in thickness to a spoke,
>since this will make a difference in the winding portion.


Dear Benjamin,

String, hell!

The trip to the garage revealed a long-forgotten 27 & 1/4
inch 36-spoke cross-3 front wheel, probably from a 1980's
Schwinn.

After undoing four spokes, I found that I could cross each
pair once (give a pair of crossing spokes a half-twist) and
still get them to thread into the nipples.

On a 36-spoke wheel, this means half-twisting spokes
separated by six other spokes on the hub, a pair that
already crosses.

It looks as if about 4mm more spoke was exposed, so this
weird pattern would have allowed using a spoke that was
about 4mm too long for normal spoking. If you had nothing
but such too-long spokes handy, you could shove a pair into
a wheel to replace a broken spoke and a good spoke and hope
that no one noticed the weird pair.

God knows how hard it would be to true such a wheel, since
tightening or loosening one spoke would tighten or loosen
the one that it was twisted around.

There must be a number of odd patterns for this sort of
weird twisted-spoke lacing. The next obvious step up on a
36-spoke hub (I think) might be to re-arrange the spoke
heads in and out to allow crossing pairs of parallel spokes,
the ones separated by eight other spokes. This would require
longer than original spokes and a lot of fuss.

But the Australian 36-spoke wheel seems to cross spokes
separated by only four other spokes and uses a double twist:

http://www.ozbizz.com/melton/kensbikes/snowflake.htm

So does the 36-spoke unicycle:

http://www.xs4all.nl/~klaasbil/107_0755.JPG

The 32-spoke example uses a different pattern, but I can't
make out the details because the hub is obscured by the disc
brake:

http://www.dtonline.org/structures/...d=0&_DontCache=1062613691&_Where=AllValidated
or http://tinyurl.com/5jhy4

I still doubt that this crossing has any benefit (other than
allowing emergency use of too-long spokes), but it's amusing
to see how much fuss it requires in its more exotic forms.
Somewhere, I suspect that an enthusiast must have posted
some details about patterns and lengths.

Carl Fogel
 
On Tue, 07 Dec 2004 17:48:43 -0700, [email protected]
wrote:

>On 5 Dec 2004 01:29:36 -0800, [email protected] (papercut)
>wrote:
>
>>From a recent post elsewhere:
>>
>>>citing gerd schraner from his book "the art of wheelbuilding" --

>>
>>>the twisting of spokes, instead of classic crossing work is a waste

>>of time for >road use. tests have shown that it results in a very
>>unstable wheel. the >lateral stability is about the same as a
>>normally spoked wheel, but radially the >wheel reacts so sluggishly
>>that encounters with momentary radial overloads the >highly praised
>>damping effect is delayed. ... twisted spoking patterns are an
>>>additional mechanical disadvantage resulting from the extreme angle

>>of the spoke >directly at the nipple. (schraner, p. 60)
>>
>>So, there is a claim that wheels with twisted spokes have a
>>significantly different "damping factor" than normally laced wheels.
>>The above quote given as evidence.
>>
>>It is also claimed that this "damping factor" inherent in
>>twisted-spoke wheels are good for trials riding. This conclusion
>>deduced somehow.
>>
>>
>>Sounds like a lot of pseudoscience to me. What's the scoop on this?

>
>And here's an even better pair of pictures of the snowflake,
>chain-link, twisted-spoke wheel:
>
>http://www.ozbizz.com/melton/kensbikes/snowflake.htm
>
>Note that these Australian wonders have a double-twist,
>producing God knows what kind of effect.
>
>Technically, this has moved beyond chain-link to
>chicken-wire.
>
>Now I'm hoping to find a wheel with four spokes twisted.
>
>Carl Fogel


Yes, twisted spoke wheels with 4 twists are out there:

"The rear wheel is totally unique as far as lacing is
concerned. No one in this region has copied it yet (phew).
Its 3X on the static side and 2X-Twist on the drive side.
And to make it even stranger, while most twisted/snowflake
pattern wheels use two wrappings of the spokes, I used 4
wrappings. It was a ***** to dish right (tensioning
snowflake pattern spokes is more involved anyways but...)."

http://home.ca.inter.net/~kroberge/9000.html

More and more this twisted-spoke stuff sounds like
decorative art, much like the extended forks of chopper
motorcycles, something that shows how a robust design can be
distorted to ridiculous extremes and still work.

Carl Fogel
 
W

Werehatrack

Guest
On Wed, 08 Dec 2004 13:13:27 -0700, [email protected] wrote:

> ([Jobst's] 2 mm minimum [for the correct length of a spoke] strikes me
>as a bit low.)


I would say that if anything, it's a trifle generous; plus or minus
1mm is the standard that I find acceptable, though I'll go with plus
two or three (and apply a little elective surgery if necessary) if I
don't have one that's within the preferred spec.
--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
Words processed in a facility that contains nuts.
 
On Thu, 09 Dec 2004 15:00:09 GMT, Werehatrack
<[email protected]> wrote:

>On Wed, 08 Dec 2004 13:13:27 -0700, [email protected] wrote:
>
>> ([Jobst's] 2 mm minimum [for the correct length of a spoke] strikes me
>>as a bit low.)

>
>I would say that if anything, it's a trifle generous; plus or minus
>1mm is the standard that I find acceptable, though I'll go with plus
>two or three (and apply a little elective surgery if necessary) if I
>don't have one that's within the preferred spec.


Dear Werehatrack,

I think that you're right in that I didn't make myself
clear. For "correct" or "acceptable" length, people on
rec.bicycles.tech often fuss about 1mm differences in spoke
lengths.

But for a spoke length that will work in the crudest sense
of being not quite too short to thread into the nipple and
not quite so long that the spoke sticks out alarmingly past
the nipple, the full range is probably around 6mm or so.

Many spoke suppliers reduce inventory and fuss by carrying
spokes in 2mm increments---292, 294, 296, and so on--without
any real problems.

The illusion of even more range is created by the different
methods used to measure spoke lengths, as suggested by
frequent posts and replies here about adding or subtracting
a millimeter on spoke calculators according to manufacturer.

Carl Fogel