Too many spokes
Skippy
At what point does a wheel have too many spokes?
If you go above a certain number, I'm speculating that the increase in
number of holes weakens the rim. clearly the spokes are under lower
individual tension.
Also more spokes equates to undesired extra mass and (some) more drag for a
deminishing improvement in reliability.
As a base for conjecture:
A front wheel for a road bike (20lbs) with rider of 170lbs
700C box rim such as Mavic Open Pro or something available with lots of
holes. Eyelets or sockets fitted.
No specific front hub, but something large-flanged enough to take lots of
spokes. Drilled for the right number in each case.
Spokes guage to be determined by number used.
Brass nipples.
Laced 3x.
Built by the same guy.
It's common belief that a wheel can have too few spokes, but how about too
many?
Skippy
E&OE
(Hope this won't start another rant-fest, and that it's not FAQ)
bookieb
> Hi folks
<snip>
> If you go above a certain number, I'm speculating that the increase in
> number of holes weakens the rim.
All else being equal, this sounds correct..
However, all else isn't equal.
Take the extreme example of 40 hole tandem rims - although the extra
holes nominally weaken the rim, the rim is almost certainly a heavy
duty item, so overall, it comes out stronger.
Likewise, 40 hole tandem hubs generally have larger hubs to keep a
decent amount of material between the spoke hole drillings.
Equally, where the spoke count is low, the rim has been designed to
take that into account.
> clearly the spokes are under lower individual tension.
Ummm - dunno if that's right.... you'd need to see the spec sheet for
the hubs to see if they give different max. spoke tensions for the
various drillings of the same rim.
> Also more spokes equates to undesired extra mass and (some) more drag for a
> deminishing improvement in reliability.
Yep, but those using the higher spoke count wheels (typically
tandemists, heavily laden tourists, those doing long distance
unsupported rides, or the very large rider) see these trade offs as
worthwhile.
The loaded tourist is hauling luggage + extra kit (say 20-30kg) anyway,
and probably at a relatively low average speed, so the weight and
aerodynamic concerns are lower on their list of priorities that they
are for the unladen day rider.
>
> As a base for conjecture:
>
> A front wheel for a road bike (20lbs) with rider of 170lbs
> 700C box rim such as Mavic Open Pro or something available with lots of
> holes. Eyelets or sockets fitted.
> No specific front hub, but something large-flanged enough to take lots of
> spokes. Drilled for the right number in each case.
> Spokes guage to be determined by number used.
> Brass nipples.
> Laced 3x.
> Built by the same guy.
>
<snip>
Common range for that kind of wheel would be 28, 32 or 36 spoke.
Looking as Sheldon's table at:
http://www.sheldonbrown.com/gloss_sp-ss.html#spoke
.and taking the wheelsmith 2.0DB (2.0/1.8) as an example, the spokes
weigh 193 g. for 32, so each spoke weighs about 6g, plus a nipple, say
1g.
Each four extra spokes weighs an extra 7g x 4 = 28g - say 55g for
eight, two wheels 100g.
That's not nothing, but again, looking at:
http://weightweenies.starbike.com/listings/components.php?type=roadwheels
...light end wheelsets seem to come in at 1500g .
100g / 1500g - approx. 7% - not huge.
A more typical wheelset might come in at 2kg, or more - the difference
is proportionally less in that case.
Long experience has shown that conventional wheels with 28 to 36 spokes
are a good reliable balance between longevity and performance for most
riders. That doesn't mean that it can't be improved on,.
As regards aerodynamics, I've no idea, but I would suggest that for the
majority of bikes (my own included), the limiting factor is the engine,
and the biggest gains are available by working on that, rather than
saving 10% on wheel weight or wheel drag ;-)
bookieb
Tuschinski
more common.
Skippy
"bookieb" <tsgte...@yahoo.co.uk> wrote in message
news:1150975422....@m73g2000cwd.googlegroups.com...
> Skippy wrote:
>> Hi folks
> <snip>
>> If you go above a certain number, I'm speculating that the increase in
>> number of holes weakens the rim.
> <snip>
>
> All else being equal, this sounds correct..
> However, all else isn't equal.
> Take the extreme example of 40 hole tandem rims - although the extra
> holes nominally weaken the rim, the rim is almost certainly a heavy
> duty item, so overall, it comes out stronger.
> Likewise, 40 hole tandem hubs generally have larger hubs to keep a
> decent amount of material between the spoke hole drillings.
> Equally, where the spoke count is low, the rim has been designed to
> take that into account.
>
>> clearly the spokes are under lower individual tension.
>
> Ummm - dunno if that's right.... you'd need to see the spec sheet for
> the hubs to see if they give different max. spoke tensions for the
> various drillings of the same rim.
Sorry, I thought that generally, when the spoke count went down the tension
went up (that's what the E&OE's for). Is this just that boutique wheels use
deeper/stiffer rims? Does a 32 spoke wheel have similar tension to a 36 for
example?
Agreed that the increased loads on tandems and tourists may warrant a
tougher rim and more spokes. That's why I proposed the 'roadie' example.
The point I'm trying to get to is that yes 40/48 spoke wheels are in
practical terms no more reliable for the roadie. I'm just pondering whether
36 and then maybe 32 are too. I've got a 28 3x front wheel which seems to
be as durable as the 32 3x wheels I've had before. We're not into
'boutique' silliness here, but is 32 the optimum?
It seems to me that wheel components have got a bit better since it was
common to have 32/36 in a road wheel. A comment from the guy who built my
wheels was that 'well the rims are round to start off with these days. That
helps!'. I'm fairly sure spokes are better too.
So for the example roadie might we be 'over-building his/her wheels? I know
it's not much, but it would be one in the eye for the box wheel enthusiasts
to see a 24 spoker on proper hubs that looks as 'trendy' as theirs, costs
less, but doesn't turn into a Pringle when you look at it funny. Would such
a wheel be noticibly worse than 28, which seems no worse than 32 for me
anyway.
Just food for thought, not a crusade.
Skippy
E&OE
Qui si parla Campagnolo
Skippy wrote:
> Hi folks
>
> At what point does a wheel have too many spokes?
>
> If you go above a certain number, I'm speculating that the increase in
> number of holes weakens the rim. clearly the spokes are under lower
> individual tension.
Both points are not correct, I guess unless the rim had say 200 or so
spoke holes.
>
> Also more spokes equates to undesired extra mass and (some) more drag for a
> deminishing improvement in reliability.
>
> As a base for conjecture:
>
> A front wheel for a road bike (20lbs) with rider of 170lbs
> 700C box rim such as Mavic Open Pro or something available with lots of
> holes. Eyelets or sockets fitted.
> No specific front hub, but something large-flanged enough to take lots of
> spokes. Drilled for the right number in each case.
> Spokes guage to be determined by number used.
> Brass nipples.
> Laced 3x.
> Built by the same guy.
>
> It's common belief that a wheel can have too few spokes, but how about too
> many?
>
> Skippy
> E&OE
> (Hope this won't start another rant-fest, and that it's not FAQ)
Right....nobody will argue about this...kinda of a non argumant-yes?
In the world of what is available hole wise in hubs and rims, worry
about not enough, not too many..36, what is currently available as a
maximum for non tandem stuff, is not too many..
nikojorj_ja...@yahoo.fr
> If you go above a certain number, I'm speculating that the increase in
> number of holes weakens the rim.
Let's assume a hole in a continuous structure has an influence on (say)
3 times its diameter, ie that at more than 3 times hole radius, stress
is the same with or without the hole. If the above is correct, then
with 8mm holes and 600mm ERD you can put as much as (600*3.14)/3*8=75
spokes on a 622mm rim.
Of course, the "3time radius" hypothesis is rather optimistic, but the
point is that as the stress is not uniform on a wheel, the stress
concentration around the holes are a more weaker link that the general
decrease in supporting matter, ie the wheel will more likely fail
around a hole than elsewhere.
> clearly the spokes are under lower
> individual tension.
Doesn't seem so clear to me...
Spoke tension should be a compromise between two things:
- on one hand, keep it lower than the weaker of the following limits :
tensile strength of the spoke, or of the rim around spoke hole, or of
the spoke nipple thread (a common problem with the special Mavic FORE
nipples),
- on the other hand, keep it higher than the load exerted on spokes by
the sum of rider weight, shocks and pedaling or braking if any couples.
The first high limit is relatively constant according to the above (at
least around 36 spokes), as the second low limit is clearly linearly
decreasing with spoke count.
So, a higher-spoke-count wheel can be built with the same spoke
tension, it will only make it stronger (or to be more correct, less
prone to spoke slackening, which is the Big Bad Evil in a spoke-laced
wheel, isn't it?) unless holes are close enough to have significant
stress buildup between them.
It can also be built with proportionnally less tension, decreasing
stress arond holes. According to that, it would need the rim to be a
real Emmental-cheese before having the wheel weaker because of too many
spokes!
It reminds me of trial rims sold here in France, that are largely
hollow between spoke holes, made by (or sold by) Try All :
http://www.peppl.com/media/product/images/HDDB418fdfb02db1d.jpg
Didn't hear complaints about these rims being too weak. Of course, the
upper sectrion of the box is not hollow! That can make a difference,
specially with a non-eyelet or single-eyelet rim.
Practically, very high spoke count could have at least the disavantage
of being difficult to lace, as the cross count shall increase with
spoke count to keep spoke angles constant (ie a 24 spokes wheel built
2X has the same spoke angles as a 36 spokes 3X and as a 48 spokes 4X
and so on) : the 6X needed for a 72-spokes wheel should not be easy to
deal with.
nikojorj_ja...@yahoo.fr
> If you go above a certain number, I'm speculating that the increase in
> number of holes weakens the rim.
Let's assume a hole in a continuous structure has an influence on (say)
3 times its diameter, ie that at more than 3 times hole radius, stress
is the same with or without the hole. If the above is correct, then
with 8mm holes and 600mm ERD you can put as much as (600*3.14)/3*8=75
spokes on a 622mm rim.
Of course, the "3time radius" hypothesis is rather optimistic, but the
point is that as the stress is not uniform on a wheel, the stress
concentration around the holes are a more weaker link that the general
decrease in supporting matter, ie the wheel will more likely fail
around a hole than elsewhere.
> clearly the spokes are under lower
> individual tension.
Doesn't seem so clear to me...
Skippy
spokes.
I'd just picked that up from RBT.... Reduced spoke-count wheels using higher
tensions being noted on a number of occasions.
Skippy
E&OE, as ever!
dvt
> At what point does a wheel have too many spokes?
Here's my take on the subject... it's a practical limit.
In days gone by, a 36 spoke wheel would occasionally break spokes. That
failure rate was deemed acceptable at the time. If you used fewer spokes
of the same size and brought the wheel to the same tension, you would
experience more broken spokes because the stress in the spokes was
higher. One could possibly have used thicker spokes to compensate, but
then you'd need a deeper rim since the unsupported spans were larger. As
far as I can tell, deep section rims were not available in the 70s.
More than 36 spokes of the same diameter would reduce spoke failures,
but increase weight. Nobody wants to do that without good cause. Again,
one could have compensated with thinner spokes, but spoke windup would
be a problem during the build process.
So 36 spokes became a de facto standard.
Fast forward a few years... spoke quality improved, as did the
understanding of the wheel building process. The standard 36 spoke wheel
is now nearly immune to spoke failures. We can now use fewer spokes of
the same diameter (1.8 or 2.0 mm) with a low failure rate. Rim cross
sections have become deeper, allowing the larger unsupported spans
required.
The spoke windup problem has not changed; thin spokes are still a pain
in the butt to build with.
Note that this does not cover all of the pros and cons of different
spoke counts (i.e. failure mode, heavier riders, aerodynamics, and the
list goes on). It's my general opinion of the current state of affairs.
--
Dave
dvt at psu dot edu
Everyone confesses that exertion which brings out all the powers of body
and mind is the best thing for us; but most people do all they can to
get rid of it, and as a general rule nobody does much more than
circumstances drive them to do. -Harriet Beecher Stowe, abolitionist and
novelist (1811-1896)
jobst....@stanfordalumni.org
> At what point does a wheel have too many spokes?
> If you go above a certain number, I'm speculating that the increase
> in number of holes weakens the rim. clearly the spokes are under
> lower individual tension.
Can't you just ask without blurting out misinformation to show that
you really don't know much about it? This is a mix of MAS (male
answer syndrome) and wanting to find an answer. MAS: Give an answer
whether you know anything about it or not.
The rim is as weak as its smallest cross section and it doesn't get
worse with more spokes, spokes that give the rim radial rigidity. A
bare rim can be deflected manually more than 100 times what it does in
a wheel under heavy loading.
As for spoke tension, it is only needed to keep spokes from going
slack and the more of them the less individual loading they carry to
become slack. With your argument, taken to the limit, the best wheel
would have no spokes and no holes, not even a valve stem hole.
> Also more spokes equates to undesired extra mass and (some) more
> drag for a deminishing improvement in reliability.
So get some 10-spoke wheels and use them. You seem to have reasons in
favor of that.
> As a base for conjecture:
> A front wheel for a road bike (20lbs) with rider of 170lbs
> 700C box rim such as Mavic Open Pro or something available with lots
> of holes. Eyelets or sockets fitted.
> No specific front hub, but something large-flanged enough to take
> lots of spokes. Drilled for the right number in each case.
> Spokes guage to be determined by number used.
> Brass nipples.
> Laced 3x.
> Built by the same guy.
Spoke gauge is mainly a wheel building parameter. Too thin a spoke
cannot be tightened without twisting off in the process, so when fewer
spokes (that require higher tension) are used, they must be thicker.
That's how we came to the 1.6mm diameter spoke shaft because 1.5mm
ruptures when tightened for 36-spoke wheels. Causes and effects are
so often misrepresented that repeating them once more only helps
perpetuate these myths. Building with thin spokes is more difficult
than with thick ones.
> It's common belief that a wheel can have too few spokes, but how
> about too many?
So what's your point? BMX wheels with 72 spokes aren't unusual.
Today, spoke count is fashion!
Don't worry, the best number of spokes for durable 700c wheels was
pragmatically determined a long time ago at 36. As you see, cracking
rims are part of the landscape today (and formerly were not) with most
riders believing that this is to be expected. Today many people with
extra money are erasing the long development of reliable bicycle
wheels. Mavic appears to be pandering to those people.
> (Hope this won't start another rant-fest, and that it's not FAQ)
I'm not sure what you had in mind but by its nature this is a troll,
starting as it does.
Jobst Brandt
Sheldon Brown
> Don't worry, the best number of spokes for durable 700c wheels was
> pragmatically determined a long time ago at 36.
36 is good, but I think the Brits were even better off with 32/40.
Nobody ever has trouble with front wheels, it's the rears that fail, so
it really makes sense to have more in back, especially with
derailer-type wheels where the rear is weakened by dishing.
The older British bikes even managed to use the same spoke length
front/rear by going cross 3 in front, cross 4 in back.
If you have the same number of spokes front/rear, either the rear wheel
is weaker than it should be, or the front is heavier than it needs to be.
As a practical mater, however, with currently available parts, 36/36 or
32/36 makes more sense.
Sheldon "Anglophile" Brown
+----------------------------------------------------+
| I admit that reason is a small and feeble flame, |
| a flickering torch by stumblers carried in the |
| star-less night, -- blown and flared by passion's |
| storm, -- and yet, it is the only light. |
| Extinguish that, and nought remains. |
| -- Robert Green Ingersoll |
+----------------------------------------------------+
Harris Cyclery, West Newton, Massachusetts
Phone 617-244-9772 FAX 617-244-1041
http://harriscyclery.com
Hard-to-find parts shipped Worldwide
http://captainbike.com http://sheldonbrown.com
carl...@comcast.net
Dear Dave,
As a sidelight, here's the Morley Brothers 1916 catalogue:
http://www.fixedgeargallery.com/morley/21.jpg
Please note that Morley sells only 32 and 36 hole hubs and that all
rear hubs are 36-hole, even the grossly overpriced $2 rear concave
nickel-plated New Departure hub, turned from solid bar.
The controversial new-fangled Sturmey-Archer 3-speed hubs are 36-holes
standard; 28, 32, and 40 holes will be furnished on special orders:
http://www.fixedgeargallery.com/morley/22.jpg
The high-technology coaster-brake hubs from New Musselman, Morrow,
Corbin, and New Departure on the page above are all 36-hole.
As for rims, Morley sells only 32 or 36 hole rims:
http://www.fixedgeargallery.com/morley/24.jpg
You may choose between reliable wood rims (natural finish or painted,
with up to 4 hair-line blue stripes), steel-lined wood rims (sorry,
only a maximum of 2 hair-line gold stripes), or the daring new
all-steel rims (black finish, supply your own damned hair-line
stripes), shipped 15 pair in a crate.
Morley's fine selection of butted spokes in every gauge:
http://www.fixedgeargallery.com/morley/21.jpg
Remember, all of Morely's No. 2 spokes are finely nickeled and hand
buffed! Available in 15-17 or 14-16 gauge (or for tandems in 13-15 and
12-14 gauge).
For the most demanding customers, Morely offers Diamond E spokes in
lengths of 11 & 7/8ths, 12 inch, and 12 & 1/8th. True, Diamond E
spokes cost 40% more than ordinary spokes, but the extra 70 cents for
a box of 100 high-quality spokes is well worth it.
Cheers,
Carl Fogel
carl...@comcast.net
Dear Sheldon,
Your spineless 32/40 Anglophile attitude makes me turn over in my
grave!
Everyone knows that 54/40 is best!
And everyone knows that we gave in on a craven 49/0 compromise with
the British due to the likes of you----
I beg your pardon. I mistook the subject for political geography, not
bicycle spokes. Still, I would prefer a 54/40 pattern for my
penny-farthing--no, my penny-dollar!--had I not died before its
invention.
http://geography.about.com/od/politicalgeography/a/5440orfight.htm
Jingoistically yours,
J.K. Polk
Werehatrack
>Hi folks
>
>At what point does a wheel have too many spokes?
Practical answer: Over 36 per wheel on a single-seat bike not used
for hauling heavy loads; it varies in other applications.
>If you go above a certain number, I'm speculating that the increase in
>number of holes weakens the rim. clearly the spokes are under lower
>individual tension.
This is not necessarily true; most 36-hole rims could support 40 or 48
without significant weakening, and the spoke tension need not be
reduced in the process.
>Also more spokes equates to undesired extra mass and (some) more drag for a
>deminishing improvement in reliability.
That's why 36 is a common number of spokes.
>As a base for conjecture:
>
>A front wheel for a road bike (20lbs) with rider of 170lbs
>700C box rim such as Mavic Open Pro or something available with lots of
>holes. Eyelets or sockets fitted.
>No specific front hub, but something large-flanged enough to take lots of
>spokes. Drilled for the right number in each case.
>Spokes guage to be determined by number used.
>Brass nipples.
>Laced 3x.
>Built by the same guy.
>
>It's common belief that a wheel can have too few spokes, but how about too
>many?
72 is too many, and so is 144, in most applications. Both are seen on
chrome-plated 20" low-riders. "Too many" is a function of a number of
things, and is, in the final analysis, mostly a matter of opinion.
--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
Words processed in a facility that contains nuts.
Skippy
> you really don't know much about it? This is a mix of MAS (male
> answer syndrome) and wanting to find an answer. MAS: Give an answer
> whether you know anything about it or not.
>
asking a question! I've already apologied for comments in the original
posting that were wrong. There is a reason i put E&OE at the bottom. If I
knew everything, I wouldn't ask questions.
> The rim is as weak as its smallest cross section and it doesn't get
> worse with more spokes, spokes that give the rim radial rigidity. A
> bare rim can be deflected manually more than 100 times what it does in
> a wheel under heavy loading.
No chance for crack propogation from a drilled hole? If so the probablity
of such a failure increases with the number of holes.
>
> As for spoke tension, it is only needed to keep spokes from going
> slack and the more of them the less individual loading they carry to
> become slack. With your argument, taken to the limit, the best wheel
> would have no spokes and no holes, not even a valve stem hole.
>
Yes, if reduced to absurdity. Things cardinal in nature have a tendancy not
to work with either 0 or 1 elements.
> So get some 10-spoke wheels and use them. You seem to have reasons in
> favor of that.
>
Have I? What makes you say that? As it happens, I haven't and it's not
what I'm asking.
>
> Don't worry, the best number of spokes for durable 700c wheels was
> pragmatically determined a long time ago at 36.
'A long time ago' is sort of my question. It is just possible that
components have improved in that time. If so, might the 'best number' be
32, or maybe 28?
>As you see, cracking
> rims are part of the landscape today (and formerly were not) with most
> riders believing that this is to be expected. Today many people with
> extra money are erasing the long development of reliable bicycle
> wheels. Mavic appears to be pandering to those people.
I find it hard to believe that there is a company driven push to produce
parts that fail so easily. There must a market pull in some form given the
duration of the fad.
>
>> (Hope this won't start another rant-fest, and that it's not FAQ)
>
> I'm not sure what you had in mind but by its nature this is a troll,
> starting as it does.
>
> Jobst Brandt
Troll? No. If you really thought this was a troll message, you wouldn't
have responded, would you? I didn't want people ranting about how crap box
wheels are. I think that's been done to death. I was merely asking if the
'36' might now be a bit conservative for a certain usage.
Skippy
E&OE
Skippy
"dvt" <dvt+u...@psu.edu> wrote in message
news:e7ehqk$thi$1...@f04n12.cac.psu.edu...
Thanks.
Skippy
E&OE
carl...@comcast.net
>> Can't you just ask without blurting out misinformation to show that
>> you really don't know much about it? This is a mix of MAS (male
>> answer syndrome) and wanting to find an answer. MAS: Give an answer
>> whether you know anything about it or not.
>>
>Is this an insult?
[snip]
Dear Skippy,
Unfortunately, yes.
Jobst is famous for such snarls. He does try to control it, but he
really just can't help himself.
You can see his more pleasant side here:
Well, okay, you still have to skip a few threads and posts--
All right, you have to skip a lot of them . . .
But this one is nice:
http://groups.google.com/group/rec.bicycles.rides/msg/88b060e0f3fee376?hl=en&
Jobst is off soon for his annual ride in the Alps, so we should get
more of this kind of good stuff:
http://groups.google.com/group/rec.bicycles.rides/msg/659034a39253c5b9?hl=en&
Cheers,
Carl Fogel
jobst....@stanfordalumni.org
>> Don't worry, the best number of spokes for durable 700c wheels was
>> pragmatically determined a long time ago at 36.
> 36 is good, but I think the Brits were even better off with 32/40.
> Nobody ever has trouble with front wheels, it's the rears that fail,
> so it really makes sense to have more in back, especially with
> derailer-type wheels where the rear is weakened by dishing.
Although front wheels are not as heavily loaded as rear wheels, they
often take shock loads greater than rear wheels with hard braking and
hitting road bumps while doing so. When I ride in the forests of the
Santa Cruz mountains, its the front wheel that I try to protect when
descending rough dirt roads. These impacts do not contribute
significantly to spoke fatigue but it is those moments that a full
complement of tight spokes are essential to prevent wheel failure.
Therefore, 36 spokes are warranted in front wheels as is not having
different rims front and rear so 36 spokes in the rear is a good
compromise.
> The older British bikes even managed to use the same spoke length
> front/rear by going cross 3 in front, cross 4 in back.
Well, that's only because it is not reasonably possible to x4 a small
flange front hub. My wheels have always been x4 rear and x3 front to
make spokes lie as tangential as possible from the hub (for flange
life). That's why I am still riding 1960's Campagnolo Record hubs
with the DT spokes with which they were built... more than 300K miles
ago.
> If you have the same number of spokes front/rear, either the rear
> wheel is weaker than it should be, or the front is heavier than it
> needs to be.
As I said there are other considerations than those alone.
> As a practical mater, however, with currently available parts, 36/36
> or 32/36 makes more sense.
Oh! Practicality of equipment has not been a subject on wreck.bike in
a long time. Wait, it's weight and carbon that counts.
Jobst Brandt
jobst....@stanfordalumni.org
>> Can't you just ask without blurting out misinformation to show that
>> you really don't know much about it? This is a mix of MAS (male
>> answer syndrome) and wanting to find an answer. MAS: Give an answer
>> whether you know anything about it or not.
> Is this an insult? Wanting to find an answer - what a strange reason for
> asking a question! I've already apologied for comments in the original
> posting that were wrong. There is a reason i put E&OE at the bottom. If I
> knew everything, I wouldn't ask questions.
So why do you tell us how these things work if you want to know. This
is old hat on this forum. We get a long dissertation on a technical
subject with a faint disclaimer at the very end of "That's right isn't
it?" Just ask and let it ride.
>> The rim is as weak as its smallest cross section and it doesn't get
>> worse with more spokes, spokes that give the rim radial rigidity.
>> A bare rim can be deflected manually more than 100 times what it
>> does in a wheel under heavy loading.
> No chance for crack propogation from a drilled hole? If so the
> probablity of such a failure increases with the number of holes.
Not if the rim has sockets, but then you may have noticed that Mavic
got rid of sockets... they weigh too much for the modern rider.
Before Mavic scraped the NA-2, the western world's most common rim,
all good rims had sockets and rim cracking was reserved for ultra
light models. Rim cracking is dependent on bearing area of spoke
loads (no sockets) and anodizing, a hard brittle skin on aluminum
rims.
>> As for spoke tension, it is only needed to keep spokes from going
>> slack and the more of them the less individual loading they carry
>> to become slack. With your argument, taken to the limit, the best
>> wheel would have no spokes and no holes, not even a valve stem
>> hole.
> Yes, if reduced to absurdity. Things cardinal in nature have a
> tendancy not to work with either 0 or 1 elements.
>> So get some 10-spoke wheels and use them. You seem to have reasons in
>> favor of that.
> Have I? What makes you say that? As it happens, I haven't and it's not
> what I'm asking.
How many spokes are you trying to justify?
>> Don't worry, the best number of spokes for durable 700c wheels was
>> pragmatically determined a long time ago at 36.
> 'A long time ago' is sort of my question. It is just possible that
> components have improved in that time. If so, might the 'best number' be
> 32, or maybe 28?
I don't see any. As I said, I am riding on rims from the past and
have no cracks nor do I have spoke failures that were not cause by
foreign objects getting into the wheel. These are ancient spokes and
hubs as bicycling goes. As another contributor mentioned, 28 and
32-spoke wheels have been around for a long time as well but riders
were aware of the drawbacks.
>> As you see, cracking rims are part of the landscape today (and
>> formerly were not) with most riders believing that this is to be
>> expected. Today many people with extra money are erasing the long
>> development of reliable bicycle wheels. Mavic appears to be
>> pandering to those people.
> I find it hard to believe that there is a company driven push to
> produce parts that fail so easily. There must a market pull in some
> form given the duration of the fad.
Naive, is the word. Can you imagine what motivated Mavic to
discontinue the MA-2 and offer hard anodized, welded, machined rims in
its place at three times the price? After all, that came right after
Look Ski bindings bought Mavic, a reliable old rim company.
>>> (Hope this won't start another rant-fest, and that it's not FAQ)
>> I'm not sure what you had in mind but by its nature this is a
>> troll, starting as it does.
> Troll? No. If you really thought this was a troll message, you
> wouldn't have responded, would you? I didn't want people ranting
> about how crap box wheels are. I think that's been done to death.
> I was merely asking if the '36' might now be a bit conservative for
> a certain usage.
At times I find responding to trolls like this one with some
corrective comments appropriate, lest the reading audience blandly
absorbs its misinformation.
Jobst Brandt
jobst....@stanfordalumni.org
>> Can't you just ask without blurting out misinformation to show that
>> you really don't know much about it? This is a mix of MAS (male
>> answer syndrome) and wanting to find an answer. MAS: Give an answer
>> whether you know anything about it or not.
> Is this an insult? Wanting to find an answer - what a strange reason for
> asking a question! I've already apologied for comments in the original
> posting that were wrong. There is a reason i put E&OE at the bottom. If I
> knew everything, I wouldn't ask questions.
So why do you tell us how these things work if you want to know. This
is old hat on this forum. We get a long dissertation on a technical
subject with a faint disclaimer at the very end of "That's right isn't
it?" Just ask and let it ride.
>> The rim is as weak as its smallest cross section and it doesn't get
>> worse with more spokes, spokes that give the rim radial rigidity.
>> A bare rim can be deflected manually more than 100 times what it
>> does in a wheel under heavy loading.
> No chance for crack propogation from a drilled hole? If so the
> probablity of such a failure increases with the number of holes.
Not if the rim has sockets, but then you may have noticed that Mavic
got rid of sockets... they weigh too much for the modern rider.
Before Mavic scrapped the MA-2, the western world's most common rim,
all good rims had sockets and rim cracking was reserved for ultra
light models. Rim cracking is dependent on bearing area of spoke
loads (no sockets) and anodizing, which is hard brittle skin on
aluminum.
>> As for spoke tension, it is only needed to keep spokes from going
>> slack and the more of them the less individual loading they carry
>> to become slack. With your argument, taken to the limit, the best
>> wheel would have no spokes and no holes, not even a valve stem
>> hole.
> Yes, if reduced to absurdity. Things cardinal in nature have a
> tendancy not to work with either 0 or 1 elements.
>> So get some 10-spoke wheels and use them. You seem to have reasons in
>> favor of that.
> Have I? What makes you say that? As it happens, I haven't and it's not
> what I'm asking.
How many spokes are you trying to justify?
>> Don't worry, the best number of spokes for durable 700c wheels was
>> pragmatically determined a long time ago at 36.
> 'A long time ago' is sort of my question. It is just possible that
> components have improved in that time. If so, might the 'best number' be
> 32, or maybe 28?
I don't see any. As I said, I am riding on rims from the past and
have no cracks nor do I have spoke failures that were not cause by
foreign objects getting into the wheel. These are ancient spokes and
hubs as bicycling goes. As another contributor mentioned, 28 and
32-spoke wheels have been around for a long time as well but riders
were aware of the drawbacks.
>> As you see, cracking rims are part of the landscape today (and
>> formerly were not) with most riders believing that this is to be
>> expected. Today many people with extra money are erasing the long
>> development of reliable bicycle wheels. Mavic appears to be
>> pandering to those people.
> I find it hard to believe that there is a company driven push to
> produce parts that fail so easily. There must a market pull in some
> form given the duration of the fad.
Naive, is the word. Can you imagine what motivated Mavic to
discontinue the MA-2 and offer hard anodized, welded, machined rims in
its place at three times the price? After all, that came right after
Look Ski bindings bought Mavic, a reliable old rim company.
>>> (Hope this won't start another rant-fest, and that it's not FAQ)
>> I'm not sure what you had in mind but by its nature this is a
>> troll, starting as it does.
> Troll? No. If you really thought this was a troll message, you
> wouldn't have responded, would you? I didn't want people ranting
> about how crap box wheels are. I think that's been done to death.
> I was merely asking if the '36' might now be a bit conservative for
> a certain usage.
At times I find responding to trolls like this one with some
Sorni
o...@ozarkbicycleservice.com
LOL!!
....and remember, he stoops to conquer!
Barnard Frederick
> Is this an insult? Wanting to find an answer - what a strange reason for
> asking a question! I've already apologied for comments in the original
> posting that were wrong. There is a reason i put E&OE at the bottom. If I
> knew everything, I wouldn't ask questions.
For an encore to "The Bicycle Wheel", Jobst intends to write his own
version of "How to Make Friends and Influence People." I know I'll be
camping outside Barnes & Nobles for my copy.
Werehatrack
>Oh! Practicality of equipment has not been a subject on wreck.bike in
>a long time. Wait, it's weight and carbon that counts.
I keep waiting for someone to ask where they can get carbon components
that employ only Carbon 12 because they don't want any of that heavy
Carbon 14 isotope.
nikojorj_ja...@yahoo.fr
> >As you see, cracking
> > rims are part of the landscape today (and formerly were not) with most
> > riders believing that this is to be expected. Today many people with
> > extra money are erasing the long development of reliable bicycle
> > wheels. Mavic appears to be pandering to those people.
>
> I find it hard to believe that there is a company driven push to produce
> parts that fail so easily. There must a market pull in some form given the
> duration of the fad.
Alas!
We do not live in the perfectness of Eden's Garden, and as long as
companies are for better or worse tied to profits, it will be much
better for them to sell hightech things twice a year than lowtech ones
once every 12 years...
The above has been much proven with wheels, from the FORE threads
ripping out of the rim, to the PTFE ring used in place of a
way-too-heavy ball bearing in the freewheel worn after 500km, passing
by the breakage of the 20 aluminium spokes, and not to mention tension
discrepancies on new wheels exceeding 1 and 1/2 tone... All these are
Mavic examples, because it's what we see most here in France, but does
apply to other manufacturers going the same way, of course. But this is
finally another debate!
And it is simply up to you not to buy high-tech disposable wheels.
To answer your more specific question about rim cracking around hole,
I'll second Jobst : mechanically, the problem is the same whether ther
is 1 or 40 holes, and it does not worsen until holes are close enough
to have stress buildup between them. I would think that this does not
occur before something like 64 or 72 holes...
Do not forget that in a built and tensioned wheels, holes are partly
supported by the spoke nipple (it is one of the parts of the eyelet to
help that) - you must not think of it as a hollow hole.
As Jobst said, the "rim cracking around hole" problem was very rare at
the time of 36 spoke wheels, and did appear with 2 factors :
- spoke count decreasing, because the load condition implies to have
more tension in the spokes for them not to slacken, and therefore
_more_ stress around the holes under a certain spoke count (may be the
near-optimum 32 or 28?),
- the (technically unjustifiable) omission of double eyelets on
high-end rims.
Pat Lamb
> On 22 Jun 2006 20:22:30 GMT, jobst....@stanfordalumni.org wrote:
>
>> Oh! Practicality of equipment has not been a subject on wreck.bike in
>> a long time. Wait, it's weight and carbon that counts.
>
> I keep waiting for someone to ask where they can get carbon components
> that employ only Carbon 12 because they don't want any of that heavy
> Carbon 14 isotope.
Will the new marketing slogan be, "98.9% C12" or (for carbon from
petroleum) "99.9% C12?"? Or maybe, "Carbon frame, <0.01% heavy carbon"?
Pat
Mike Reed
Sheldon Brown wrote:
> Jobst Brandt wrote:
>
> > Don't worry, the best number of spokes for durable 700c wheels was
> > pragmatically determined a long time ago at 36.
>
> 36 is good, but I think the Brits were even better off with 32/40.
>
> Nobody ever has trouble with front wheels, it's the rears that fail, so
> it really makes sense to have more in back, especially with
> derailer-type wheels where the rear is weakened by dishing.
>
> The older British bikes even managed to use the same spoke length
> front/rear by going cross 3 in front, cross 4 in back.
>
> If you have the same number of spokes front/rear, either the rear wheel
> is weaker than it should be, or the front is heavier than it needs to be.
>
> As a practical mater, however, with currently available parts, 36/36 or
> 32/36 makes more sense.
>
I'm a proud builder/rider of my 32/36 Velocity Deep Vs -- built my bro
in law some too...
Only 1000 miles each on the four wheels so far, but they still pluck
the same notes on the spokes. He and I both push 200 lbs (though I'm at
a buck eighty five lately for some reason).
-Mike
jim beam
oh, you're quite shameless. or stupid. many many times jobst, it's
been pointed out that the cracking evidenced in rims is NOT the same as
that seen when initiated by anodizing. therefore your supposition,
[which was (incredibly) based on a totally inappropriate dye-penetrant
test btw], is WRONG. now, go to the library and look into extrusion
faults will you?
and correction of your immortal words "[spoke] tension as high as the
rim can bear" will do more for longevity of the western world's bike
wheels than any amount of your blaming rim manufacturers.
if your audience /didn't/ absorb misinformation, you'd never sell a
single book.
jim beam
old days was because jobst hadn't written his book yet. then
publication propagated this extraordinary concept of spoke tension "as
high as the rim can bear" in the bizarrely mistaken belief that
increasing tension means increasing wheel strength. and hence rim
cracking became an immediate industry-wide problem.
the only tangible thing with which jobst can really be given credit in
this whole fiasco is the birth of the pre-built wheel - it's the only
means by which a manufacturer has any chance of control against abuse of
their product.
Skippy
news:449b03ea$0$65496$742e...@news.sonic.net...
> Skippy Peanut Butter writes:
Another attempt at insult, or possibly humour? Not exactly effective as
either.
>
[edit]
>
> How many spokes are you trying to justify?
I was asking at what point the dimishing return in increased reliability
becomes small enough not to matter for a certain application. I'm not
trying to justify anything. 36 spokes has been suggested by you as a
historic value. 'It's the way we've always done it' isn't necessarily the
optimum. As you have 'noted' rim construction has changed. I am led to
believe that spokes have changed for the better. Hubs may have changed too.
[edit]
>> Troll? No. If you really thought this was a troll message, you
>> wouldn't have responded, would you? I didn't want people ranting
>> about how crap box wheels are. I think that's been done to death.
>> I was merely asking if the '36' might now be a bit conservative for
>> a certain usage.
>
> At times I find responding to trolls like this one with some
> corrective comments appropriate, lest the reading audience blandly
> absorbs its misinformation.
>
> Jobst Brandt
It's still not a troll.
I'm not seeing much evidence on your part here, so I'd be foolish to absorb
what you've written.
Skippy
E&OE
Pete Biggs
> <jobst....@stanfordalumni.org> wrote in message
> news:449b03ea$0$65496$742e...@news.sonic.net...
>> How many spokes are you trying to justify?
>
> I was asking at what point the dimishing return in increased
> reliability becomes small enough not to matter for a certain
> application.
What is your application?
> I'm not trying to justify anything. 36 spokes has been
> suggested by you as a historic value. 'It's the way we've always
> done it' isn't necessarily the optimum. As you have 'noted' rim
> construction has changed. I am led to believe that spokes have
> changed for the better. Hubs may have changed too.
The amount of dishing has increased too and spokes still break and wheels
still buckle. If your rear wheel has 32 spokes, you're practically riding
on just 16 of them, almost. I've experienced problems even with 36-spoke
9-speed rear wheels, so I'm not going to opt for an even less reliable
wheel just to save 20 grams, especially as a problem that couldn't be
fixed by the roadside would cause me a great deal of inconvenience. Frame
clearance has reduced too, meaning you may not get your wheel to go round
after a spoke has broken, even after adjusting other spokes to try and
compensate.
I suppose it's different if you are racing or have someone standing by all
the time ready to drive out 40 miles or however far away from home you
are.
~PB
fol...@innercite.com
on our tandems!
Skippy
"Pete Biggs" <p...@biggspomegranateremovehighlyimpracticalfruit.tc> wrote in
message news:4g838kF...@individual.net...
> Skippy wrote:
>> <jobst....@stanfordalumni.org> wrote in message
>> news:449b03ea$0$65496$742e...@news.sonic.net...
>
>>> How many spokes are you trying to justify?
>>
>> I was asking at what point the dimishing return in increased
>> reliability becomes small enough not to matter for a certain
>> application.
>
> What is your application?
A front wheel for a road bike (20lbs) with rider of 170lbs. This would be a
training wheel, with racing pretentions of course!
>
>> I'm not trying to justify anything. 36 spokes has been
>> suggested by you as a historic value. 'It's the way we've always
>> done it' isn't necessarily the optimum. As you have 'noted' rim
>> construction has changed. I am led to believe that spokes have
>> changed for the better. Hubs may have changed too.
>
> The amount of dishing has increased too and spokes still break and wheels
> still buckle. If your rear wheel has 32 spokes, you're practically riding
> on just 16 of them, almost. I've experienced problems even with 36-spoke
> 9-speed rear wheels, so I'm not going to opt for an even less reliable
> wheel just to save 20 grams, especially as a problem that couldn't be
> fixed by the roadside would cause me a great deal of inconvenience. Frame
> clearance has reduced too, meaning you may not get your wheel to go round
> after a spoke has broken, even after adjusting other spokes to try and
> compensate.
Indeed. And as some have posted here dual-pivot brakes don't follow the rim
when it's out of whack. For sake of argument here, might we consider
anything that requires opening the QR on the brake, or getting the key out
would be a failure.
>
> I suppose it's different if you are racing or have someone standing by all
> the time ready to drive out 40 miles or however far away from home you
> are.
>
> ~PB
>
>
Also true. I don't have a personal team car, unfortunately. Perhaps I
could make money running a 'rescue' car for all the unreliable wheels
around. Perhaps it could be yellow with 'Mavic' on the side!
Skippy
E&OE
jobst....@stanfordalumni.org
> Another attempt at insult, or possibly humour? Not exactly
> effective as either.
So what is your name if you don't like aliases.
> [edit]
>> How many spokes are you trying to justify?
> I was asking at what point the dimishing return in increased
> reliability becomes small enough not to matter for a certain
> application. I'm not trying to justify anything. 36 spokes has
> been suggested by you as a historic value. 'It's the way we've
> always done it' isn't necessarily the optimum. As you have 'noted'
> rim construction has changed. I am led to believe that spokes have
> changed for the better. Hubs may have changed too.
Mostly hubs and rims have changed for the worse.
I explained why 36 spokes is a reasonable number. It is not historic
but rather a number pragmatically arrived upon. Just because
expensive wheels with fewer spokes are promoted through various venues
doesn't mean they are a reasonable solution for general use. Most
people who respond to the new wheel syndrome get no benefits from them
but carry the unreliability that we read about so often here.
> [edit]
>>> Troll? No. If you really thought this was a troll message, you
>>> wouldn't have responded, would you? I didn't want people ranting
>>> about how crap box wheels are. I think that's been done to death.
>>> I was merely asking if the '36' might now be a bit conservative
>>> for a certain usage.
>> At times I find responding to trolls like this one with some
>> corrective comments appropriate, lest the reading audience blandly
>> absorbs its misinformation.
> It's still not a troll.
> I'm not seeing much evidence on your part here, so I'd be foolish to
> absorb what you've written.
The evidence is in the wheel complaints you can read here in this
space, my comments are supported by these failures.
Jobst Brandt
jim beam
> <jobst....@stanfordalumni.org> wrote in message
> news:449b03ea$0$65496$742e...@news.sonic.net...
>
>>Skippy Peanut Butter writes:
>
>
> Another attempt at insult, or possibly humour? Not exactly effective as
> either.
>
>
> [edit]
>
>>How many spokes are you trying to justify?
>
>
> I was asking at what point the dimishing return in increased reliability
> becomes small enough not to matter for a certain application. I'm not
> trying to justify anything. 36 spokes has been suggested by you as a
> historic value. 'It's the way we've always done it' isn't necessarily the
> optimum. As you have 'noted' rim construction has changed. I am led to
> believe that spokes have changed for the better. Hubs may have changed too.
of course they have. i ride a pair of mavic cosmos wheels. they're 28
spoke rear, 24 spoke front, i weigh 205#, and the wheels remain
perfectly true. i had to re-rim them a few months ago because of a
pothole incident, but the spokes and hubs are still excellent after two
winters of wet commuting.
the most important feature of these wheels are the use of straight pull
spokes which eliminate the single most fundamental problem with spoke
fatigue, that of bending at the spoke elbow. once the fatigue is
eliminated, a lower spoke count is perfectly satisfactory. all this
b.s. about 36 spokes dates back to the old days when spokes were much
inferior and broke constantly. but you won't get jobst to acknowledge
that because it blows holes in one of his pet theories about how he can
eliminate fatigue with spells and incantations.
>
> [edit]
>
>
>>>Troll? No. If you really thought this was a troll message, you
>>>wouldn't have responded, would you? I didn't want people ranting
>>>about how crap box wheels are. I think that's been done to death.
>>>I was merely asking if the '36' might now be a bit conservative for
>>>a certain usage.
>>
>>At times I find responding to trolls like this one with some
>>corrective comments appropriate, lest the reading audience blandly
>>absorbs its misinformation.
>>
>>Jobst Brandt
>
>
> It's still not a troll.
>
> I'm not seeing much evidence on your part here, so I'd be foolish to absorb
> what you've written.
steady on there skippy - you'll be burned as a heretic if you state the
obvious like that. folks round here like to think the emperor is
clothed - so you'd better fall into line there, y'heah?
>
> Skippy
> E&OE
>
>
Pete Biggs
> i ride a pair of mavic cosmos wheels. they're 28
> spoke rear, 24 spoke front, i weigh 205#, and the wheels remain
> perfectly true. i had to re-rim them a few months ago because of a
> pothole incident, but the spokes and hubs are still excellent after
> two winters of wet commuting.
Would stronger wheels survived that pothole?
~PB
Pete Biggs
> "Pete Biggs" <p...@biggspomegranateremovehighlyimpracticalfruit.tc>
> wrote in message news:4g838kF...@individual.net...
>> Skippy wrote:
>>> <jobst....@stanfordalumni.org> wrote in message
>>> news:449b03ea$0$65496$742e...@news.sonic.net...
>>
>>>> How many spokes are you trying to justify?
>>>
>>> I was asking at what point the dimishing return in increased
>>> reliability becomes small enough not to matter for a certain
>>> application.
>>
>> What is your application?
>
> A front wheel for a road bike (20lbs) with rider of 170lbs. This
> would be a training wheel, with racing pretentions of course!
I'm just a bit lighter and happy enough with 32 front, though JB puts up
an interesting argument for 36.
>>> I'm not trying to justify anything. 36 spokes has been
>>> suggested by you as a historic value. 'It's the way we've always
>>> done it' isn't necessarily the optimum. As you have 'noted' rim
>>> construction has changed. I am led to believe that spokes have
>>> changed for the better. Hubs may have changed too.
>>
>> The amount of dishing has increased too and spokes still break and
>> wheels still buckle. If your rear wheel has 32 spokes, you're
>> practically riding on just 16 of them, almost. I've experienced
>> problems even with 36-spoke 9-speed rear wheels, so I'm not going to
>> opt for an even less reliable wheel just to save 20 grams,
>> especially as a problem that couldn't be fixed by the roadside would
>> cause me a great deal of inconvenience. Frame clearance has reduced
>> too, meaning you may not get your wheel to go round after a spoke
>> has broken, even after adjusting other spokes to try and compensate.
>
> Indeed. And as some have posted here dual-pivot brakes don't follow
> the rim when it's out of whack. For sake of argument here, might we
> consider anything that requires opening the QR on the brake, or
> getting the key out would be a failure.
It woud be a failure but not a very serious one. Personally, I wouldn't
be too bothered as long as I could carry on riding the bike. Trouble is,
with minimal-clearance frames, the wheel may not turn even if the brake
was removed as the tyre jams in the stays.
>> I suppose it's different if you are racing or have someone standing
>> by all the time ready to drive out 40 miles or however far away from
>> home you are.
>
> Also true. I don't have a personal team car, unfortunately. Perhaps
> I could make money running a 'rescue' car for all the unreliable
> wheels around. Perhaps it could be yellow with 'Mavic' on the side!
Please do, then I could switch to 28 spoke wheels :-)
~PB
nikojorj_ja...@yahoo.fr
> i ride a pair of mavic cosmos wheels. they're 28
> spoke rear, 24 spoke front, i weigh 205#, and the wheels remain
>
> the most important feature of these wheels are the use of straight pull
> spokes which eliminate the single most fundamental problem with spoke
> fatigue, that of bending at the spoke elbow.
You imply then that fatigue comes from shear only, not pure tension, as
a straight spoke has the same (or may be worse, depending on the exact
geometry of hub attachment) stress concentration at its head, where it
sits in the hub, than a .
That mechanical theory is not widely supported...
To be more particular about the cosmos wheels, it seems a rule by
Mavic's that the lower the product price, the better the resistance
;o).
Frankly, the examples I gave above were mostly found on high-end wheels
(CrossMax SL or some Ksyrium). That supports the theory that the higher
the spoke count, the more resistant the wheel, as a Ksyrium wheel
sports only 18/20 spokes ;o))).
Sandy
> jim beam wrote:
>
>> i ride a pair of mavic cosmos wheels. they're 28
>> spoke rear, 24 spoke front, i weigh 205#, and the wheels remain
>> perfectly true. [...]
>>
>> the most important feature of these wheels are the use of straight pull
>> spokes which eliminate the single most fundamental problem with spoke
>> fatigue, that of bending at the spoke elbow.
>>
>
> You imply then that fatigue comes from shear only, not pure tension, as
> a straight spoke has the same (or may be worse, depending on the exact
> geometry of hub attachment) stress concentration at its head, where it
> sits in the hub, than a .
> That mechanical theory is not widely supported...
longtime standard, you would be suggesting that spoke elbows are a
miserable invention that came about to save wheelbuilders some lacing
time cost ? Are you saying that bent metal, with residual stress,
requiring expert manipulation after building, that tears hub flanges is
the right way to go ?
--
Sandy
The above is guaranteed 100% free of sarcasm, denigration, snotty
remarks, indifference, platitudes, fuming demands that "you do the
math", conceited visions of a better world on wheels according to
[insert NAME here].
nikojorj_ja...@yahoo.fr
> Why do I get the impression, that if straight-pull spokes had been the
> longtime standard, you would be suggesting that spoke elbows are a
> miserable invention that came about to save wheelbuilders some lacing
> time cost ?
[teasing mode]The fact is that spoke elbows are the long-time
standard... [/teasing mode]
And btw, I've never laced a straight-spoke wheel but I would think it
is slightly easier?
> Are you saying that bent metal, with residual stress,
> requiring expert manipulation after building, that tears hub flanges is
> the right way to go ?
Not quite... But a few things came to my mind :
- the fact that the spoke elbows tears a bit of the hub flange might be
a favourable thing about stress concentration in this area, by
extending the supported area of the spoke,
- the fact that better metallurgy techniques can reduce residual
stresses in bent spokes.
To the latter regard, it might be significant that spokes fail
generally just after the elbow, at the end of the section supported by
the hub flange, and not in the elbow itself.
Otoh, you are right in pointing that the "pre-stressing" required
during wheel tensioning, to ensure all spoke elbows sit rightly in the
hub, is some kind of mechanical torture it would be better not to
inflict to an innocent new wheel.
What I wanted to express is that straight spokes do not seem, to my
intuition, as a _much_ better thing than bent spokes, as wrote jim
beam, and that they may be overrated in this regard.
I do not imply they're worse! And I apologize for any misunderstanding
related to my difficulties to write in english : you may know how we
Frenchmen are impaired in foreign languages.
jim beam
so maybe if it had motorcycle rims, yes, a "stronger" wheel would have
survived. "stronger" is not defined solely by spoke count.
jim beam
> jim beam wrote:
>
>>i ride a pair of mavic cosmos wheels. they're 28
>>spoke rear, 24 spoke front, i weigh 205#, and the wheels remain
>>perfectly true. [...]
>>
>>the most important feature of these wheels are the use of straight pull
>>spokes which eliminate the single most fundamental problem with spoke
>>fatigue, that of bending at the spoke elbow.
>
>
> You imply then that fatigue comes from shear only, not pure tension,
i imply nothing of the sort. shear doesn't enter the equation at all.
spoke elbow fatigue is due to the bending that by definition takes place
each time load is cycled on a component so shaped.
nikojorj_ja...@yahoo.fr
> nikojorj_ja...@yahoo.Fr wrote:
> > You imply then that fatigue comes from shear only, not pure tension,
>
> i imply nothing of the sort. shear doesn't enter the equation at all.
> spoke elbow fatigue is due to the bending that by definition takes place
> each time load is cycled on a component so shaped.
My questioning was : Doesn't it apply also on the deformation induced
by tension near a straight spoke's head?
jim beam
less in straight pull as loading is axial, compared to elbowed where the
loading creates bending.
jobst....@stanfordalumni.org
No. The damage in such an event is not to spokes or spoke support
(they only slacken under such an impact) but is a dent in the tire
bead and a flat or inward bend of the rim. The bead of a rim is no
different for various rims.
What were you thinking that a "stronger" wheel might offer in such an
event? I am also uncertain what you mean by "stronger".
Jobst Brandt
nikojorj_ja...@yahoo.fr
jim beam wrote:
> fatigue in pure tension is definitely possible, but the stress is much
> less in straight pull as loading is axial, compared to elbowed where the
> loading creates bending.
Hope I'll manage to summarize my point of view this time ;o)...
I would think :
1) that the local stress concentration around a straight spoke head,
and especially at the edge of the nail-head-like part, can also be
significant (even if the load is axial, there are strong tension
stresses there),
2) and that a comparison with bent spokes should take into account that
as the elbow sits more or less on the hub flange, load does not bend
the spoke as much as if the spoke head was the only supporting part of
the spoke.
To give some flesh to this bare theory, it would be interesting to know
how do straight pull spoke fail in real-world : do they fail a few mm
away from hub insertion, as do bent spokes, or does the nail-head-like
part of the spoke head pop out of the rest of the spoke? (the latter
would go in my theory's direction)
Or do straight spoke NEVER fail at all?
jobst....@stanfordalumni.org
>>> You imply then that fatigue comes from shear only, not pure
>>> tension,
>> i imply nothing of the sort. shear doesn't enter the equation at
>> all. spoke elbow fatigue is due to the bending that by definition
>> takes place each time load is cycled on a component so shaped.
> My questioning was : Doesn't it apply also on the deformation
> induced by tension near a straight spoke's head?
Elbow spokes in proper hubs have their curve entirely supported as it
lies in the dent of the aluminum flange. Only the long crook spokes
briefly made by DT (for easier insertion) failed from dangling-hook
syndrome. Straight spokes have present problems, that of hanging from
the worst formed part of the spoke, the head... and that they must be
held against rotation during initial tightening.
If you were to cross section a spoke lengthwise through its head and
etch it for microstructure, you would find a wrinkled randomly
squashed form caused by upset ramming of the spoke end. Inspecting a
spoke head with a magnifying glass reveals how crudely it is formed.
Straight spokes, like elbow spokes, must be stress relieved after
building to reduce residual stress from cold forming of head and
threads.
Jobst Brandt
Pete Biggs
I was thinking of events where where the highly-inflated tyre hasn't
totally compressed to allow the rim to be dented by the road directly, but
the wheel has buckled. By stronger, I was particularly thinking of more
spokes. I was thinking, when all else is equal, that a wheel with more
spokes will be stronger in general, not just less likely to break spokes
through fatigue.
I understand that spokes go slack from perfectly square-on impacts, but
I've had wheels buckle in pothole accidents -- ones that did survive
proper stress relieving (so I don't think the spokes were over-tight by
Brandt standards).
~PB
jobst....@stanfordalumni.org
>>>> i ride a pair of mavic cosmos wheels. they're 28 spoke rear, 24
>>>> spoke front, i weigh 205#, and the wheels remain perfectly true.
>>>> i had to re-rim them a few months ago because of a pothole
>>>> incident, but the spokes and hubs are still excellent after two
>>>> winters of wet commuting.
>>> Would stronger wheels survived that pothole?
>> No. The damage in such an event is not to spokes or spoke support
>> (they only slacken under such an impact) but is a dent in the tire
>> bead and a flat or inward bend of the rim. The bead of a rim is no
>> different for various rims.
>> What were you thinking that a "stronger" wheel might offer in such
>> an event? I am also uncertain what you mean by "stronger".
> I was thinking of events where where the highly-inflated tyre hasn't
> totally compressed to allow the rim to be dented by the road
> directly, but the wheel has buckled. By stronger, I was
> particularly thinking of more spokes. I was thinking, when all else
> is equal, that a wheel with more spokes will be stronger in general,
> not just less likely to break spokes through fatigue.
I'm sorry, I misunderstood. I didn't see that this was a wheel
collapse event but rather a pot hole damage that generally dents a rim
and causes a snake bite.
> I understand that spokes go slack from perfectly square-on impacts,
> but I've had wheels buckle in pothole accidents -- ones that did
> survive proper stress relieving (so I don't think the spokes were
> over-tight by Brandt standards).
You have some mighty pot holes. The ones I suffer from are in paved
streets with square edged asphalt rims.
Jobst Brandt
Pete Biggs
> Pete Biggs writes:
>
>>>>> i ride a pair of mavic cosmos wheels. they're 28 spoke rear, 24
>>>>> spoke front, i weigh 205#, and the wheels remain perfectly true.
>>>>> i had to re-rim them a few months ago because of a pothole
>>>>> incident, but the spokes and hubs are still excellent after two
>>>>> winters of wet commuting.
>
>>>> Would stronger wheels survived that pothole?
>
>>> No. The damage in such an event is not to spokes or spoke support
>>> (they only slacken under such an impact) but is a dent in the tire
>>> bead and a flat or inward bend of the rim. The bead of a rim is no
>>> different for various rims.
>
>>> What were you thinking that a "stronger" wheel might offer in such
>>> an event? I am also uncertain what you mean by "stronger".
>
>> I was thinking of events where where the highly-inflated tyre hasn't
>> totally compressed to allow the rim to be dented by the road
>> directly, but the wheel has buckled. By stronger, I was
>> particularly thinking of more spokes. I was thinking, when all else
>> is equal, that a wheel with more spokes will be stronger in general,
>> not just less likely to break spokes through fatigue.
>
> I'm sorry, I misunderstood. I didn't see that this was a wheel
> collapse event but rather a pot hole damage that generally dents a rim
> and causes a snake bite.
Thanks. I think Jim might have experienced dent & snake bite (?), but I
didn't know it at the time I posted my question.
>> I understand that spokes go slack from perfectly square-on impacts,
>> but I've had wheels buckle in pothole accidents -- ones that did
>> survive proper stress relieving (so I don't think the spokes were
>> over-tight by Brandt standards).
>
> You have some mighty pot holes. The ones I suffer from are in paved
> streets with square edged asphalt rims.
I was particularly thinking of the time where I got catapulted over the
bars by a hole in the road in London that perhaps was too large to call a
"pothole". Fortunately most of the holes and bumps I hit just damage my
nerves rather than my wheels at all.
~PB
Michael Press
<1151337185....@p79g2000cwp.googlegroups.com>,
nikojorj_ja...@yahoo.Fr wrote:
Metal fatigue is a complex matter. It occurs when a metal
member is cyclically stressed in such a way that a portion
of the metal is stressed above a certain value. The
microscopic structure changes; grain boundaries change;
grains change; the inter atomic forces are reduced. A
crack will form, and then stresses at the crack are
multiplied and the member will fracture. Ultimately we
could say that we smelted and formed the metal to optimize
its strength, and any change is downhill away from the
strength maximum we built.
The measure of a metal's fatigue capacity it called
fatigue limit. It is much less than the plastic limit.
Fatigue failure in spoke elbows occurs because of stress
from the elbow formation. In manufacturing the spoke elbow
is cold formed by bending the spoke. After it is bent, the
spoke springs back. Different portions of the freshly
formed bend want to spring back more than others. The
result is a balance of shear stresses frozen into the
elbow.
When the spoke is tensioned in a wheel the spoke elbow
angle changes a bit. When the wheel is ridden the spoke
periodically undergoes tension changes so that the elbow
flexes periodically, and at the built in elbows stresses
the cyclic changes fluctuate about the fatigue limit. When
we stress relieve a wheel we temporarily add stress to the
built in stresses past the plastic limit of the steel, so
that in the spoke's working state cyclic changes in
tension do not take the steel past the fatigue limit.
--
Michael Press
diann...@yahoo.com
I've seen plenty of straight pull spokes fail. Pulstar hubs were
especially bad. Of course they're not around any more.
The FAQs at the Velomax web site have something to say about spokes,
straight pull and otherwise:
quote http://www.velomax.com/faqfull.php3#12 :
=======================
Q. How is a Velomax spoke different than a common straight pull spoke?
Common straight pull spokes have eliminated the bent elbow, but still
have the cold formed head. This head seats against the inside of the
hub, or, in some designs, the nipple bed of the rim. Velomax spokes are
threaded on both ends, eliminating the cold-formed head altogether.
This offers significant advantages over straight pull spokes.
While it was generally believed that common straight pull spokes would
be stronger than conventional spokes with an "elbow" bend, this has not
proven to be the case. In addition, common straight pull spokes have
some notable disadvantages. First, there is nothing to keep the spoke
from spinning in the hub during tensioning. This means that you may
have manually inhibit the spoke from rotating by using pliers or
similar. These tools can damage the surface of the spoke. Even a tiny
surface nick can lead to a stress riser in the shaft of the spoke,
which creates an area susceptible to breakage.
The second disadvantage is that the head, which is the weakest part of
the spoke, is directly loaded in tension, i.e. - the weakest part of
the spoke bears the most load. Dynamic stresses concentrate precisely
in the area that is least capable of handling them.
The Velomax spoke threads into the hub for a direct and positive
connection. The threads are completely buried in the hub, and therefore
fully supported.
===========
end quote
quote http://www.velomax.com/faqfull.php3#14 :
===============================
Q. If T3 spokes are made from the same materials as common spokes, what
makes them stronger?
Our wheels use premium stainless steel stock, as do many of our
competitors. What makes our spokes stronger is how stresses are
distributed and disbursed. Our goal when designing the Velomax hub was
to minimize the various forces that lead to fatigue and failure of a
spoke. The Velomax T3 spoke is better able to withstand the various
forces imposed upon it, and here's why:
There are three kinds of stresses in bike spokes.
1. Peak static stresses (when the wheel is not being ridden, due to the
spoke tension).
2. Dynamic stresses (when the wheel is being ridden, due to the
changing loads the rider puts on it).
3. Residual stresses (due to forming the spoke end).
In all wheels (including Velomax), the first two stresses, static and
dynamic, are about the same, so they do not vary significantly between
ordinary wheels and Velomax wheels. What is different between Velomax
and ordinary wheels is where static and dynamic stresses hit the spoke.
In headed spokes, these two stresses exist at the same location as the
residual stresses (from forming the head or bend). This is bad. You can
use the principle of superposition to find the total stress at that
spot by adding the three kinds of stress that occur there: residual
stress plus static stress plus peak dynamic stress gives the total
stress on the spoke at that spot. That's the highest stressed spot on
the spoke, and that's where it typically breaks in fatigue.
The benefit of T3 is that static and dynamic stresses decrease along
the threaded length. That means these stresses decrease as you follow
the spoke farther into the threads in the hub. The static and dynamic
stresses are maximum at the external edge of the hub - but there is no
residual stress there since the threads are buried inside the hub. The
part of the spoke at the hub edge is virgin metal, with no residual
stresses or stress risers. Threads and the small residual stresses that
remain from forming them are farther down in the
hub, where the static and dynamic stresses have already begun to
dissipate from their peak at the outer edge of the shell. For this
reason the peak total stress is lower in a T3 spoke. Therefore, Velomax
spokes can withstand a greater number of stress cycles. That is, they
last longer.
============
end quote
jim beam
now /that/ is a choice piece of misconceived drivel. two sets of
threads are better than a properly designed head? WRONG!!! about 10%
of failures are at the threads - this doubles the chances! better than
an elbow, but /definitely/ not better than a good quality upset head.
jim beam
> Nikojorj who? writes:
>
>
>>>>You imply then that fatigue comes from shear only, not pure
>>>>tension,
>
>
>>>i imply nothing of the sort. shear doesn't enter the equation at
>>>all. spoke elbow fatigue is due to the bending that by definition
>>>takes place each time load is cycled on a component so shaped.
>
>
>>My questioning was : Doesn't it apply also on the deformation
>>induced by tension near a straight spoke's head?
>
>
> Elbow spokes in proper hubs have their curve entirely supported as it
> lies in the dent of the aluminum flange. Only the long crook spokes
> briefly made by DT (for easier insertion) failed from dangling-hook
> syndrome.
jobst, sadly, you just won't get this concept of failure analysis, will
you. saying that the elbow is fully supported is like saying that the
tacoma narrows bridge isn't affected by wind.
FACT: spokes break at the elbow.
FACT: spokes evidence fatigue initiating and propagating from the elbow.
ERGO: spokes /do/ bend under load. if they didn't, they wouldn't.
or we can approach this from a position that even a basic engineering
grad can understand: consider the shape of the piece. it's not loaded
from the axis, therefore by definition, it experiences bending. duh.
> Straight spokes have present problems, that of hanging from
> the worst formed part of the spoke, the head... and that they must be
> held against rotation during initial tightening.
more presumptive jobstian drivel. see this:
http://www.flickr.com/photos/38636024@N00/175952574/
large radius shoulders under the head, [greater than the radius of a
spoke elbow in fact], very high quality surface finish, flattened
section to hold against rotation. duh.
>
> If you were to cross section a spoke lengthwise through its head and
> etch it for microstructure, you would find a wrinkled randomly
> squashed form caused by upset ramming of the spoke end. Inspecting a
> spoke head with a magnifying glass reveals how crudely it is formed.
so fucking what??? the whole freakin' spoke is cold worked, dumb-ass!!!
don't you understand a damned thing about processing or manufacture???
[that's a rhetorical question since you think all butted spokes are
"swaged".] and you /***definitely***/ don't understand a damned thing
about the relationship between microstructure and mechanical
properties!!!!!!!
>
> Straight spokes, like elbow spokes, must be stress relieved after
> building to reduce residual stress from cold forming of head and
> threads.
so did you do the stress corrosion residual stress testing i suggested?
[another rhetorical question.] it's quite pitiful how the world's
greatest wheel expert somehow managed to miss the concept of elbow
bending being responsible for fatigue, but instead arrives are some
bizarre mis-conclusion about residual stress to explain failures. it's
like blaming the tacoma narrows bridge failure on the wrong kind of
wind. quite incredible. [and you wonder why manufacturers don't take
you seriously...]