Spoke deflection - force

On Thursday, December 12, 2013 9:33:27 AM UTC-5, Király wrote:
Advantages of butted spokes according to Sheldon Brown:

Double-butted spokes do more than save weight. The thick ends make them
as strong in the highly-stressed areas as straight-gauge spokes of the
same thickness, but the thinner middle sections make the spokes
effectively more elastic, allowing them to stretch (temporarily) more
than thicker spokes.

As a result, when the wheel is subjected to sharp localized stresses,
the most heavily-stressed spokes can elongate enough to shift some of
the stress to adjoining spokes. This is particularly desirable when the
limiting factor is how much stress the rim can withstand without
cracking around the spoke holes.

To corroborate that: In situations where long bolts are subjected to fatigue (i.e. varying) stresses, it's not uncommon to have the center of the bolt reduced in diameter. The elasticity thus gained reduces the amplitude of the bolt's stress variation, and improves the fatigue life. The theory's a little complex, but the trick certainly works.

- Frank Krygowski

On Thursday, December 12, 2013 10:55:18 AM UTC-8, Frank Krygowski wrote:
On Thursday, December 12, 2013 9:33:27 AM UTC-5, Király wrote:

Advantages of butted spokes according to Sheldon Brown:



Double-butted spokes do more than save weight. The thick ends make them

as strong in the highly-stressed areas as straight-gauge spokes of the

same thickness, but the thinner middle sections make the spokes

effectively more elastic, allowing them to stretch (temporarily) more

than thicker spokes.



As a result, when the wheel is subjected to sharp localized stresses,

the most heavily-stressed spokes can elongate enough to shift some of

the stress to adjoining spokes. This is particularly desirable when the

limiting factor is how much stress the rim can withstand without

cracking around the spoke holes.



To corroborate that: In situations where long bolts are subjected to fatigue (i.e. varying) stresses, it's not uncommon to have the center of the bolt reduced in diameter. The elasticity thus gained reduces the amplitude of the bolt's stress variation, and improves the fatigue life. The theory's a little complex, but the trick certainly works.

I always thought the benefit was that a thin spoke under reasonable tension would elongate, and when the rim was compressed at the contact patch, the overlying spoke would not loosen. You could use lower tensions without the fear of the spoke unwinding whereas with a thicker spoke, you needed higher tensions to keep the wheel true, and that could crack the rim. This was the reason Jobst always recommended 15/16 spokes -- on any bike, touring, racing, etc.

-- Jay Beattie.

REI, with garantea, sells the wheel for $100...

what's JB and Shedlon selling those parts for ?

that's a lotta engineering finesse for your buck.

bolts stretch under load.

so ?

buy expensive spokes

http://www.universalcycles.com/shopp...ls.php?id=2460

you wanna commute, commute ! you wanna GT ? move to Denver.

oh yeah costs. buying Swiss costs twice what buying Mx or Chinese/Asian costs so the Swiss rim costs what the entire wheel is at REI.

Now uragonna tell us the DT rim is better than the Rhyno...why ?

METALLURGY !

PROCESSING !


FABRICATION !

BULL**** !

Stephen Bauman wrote:
Is this a front or rear wheel. If rear wheel, which side?

Front. I've concluded that 70 kgf is too low if the max spec is 122
kgf. I'll go back to the shop and tighten up the spokes a little more.

PS does anyone else have a "self-serve" bike repair shop in your town?
They have all the tools you could ever need, and you pay $6/hour to use
whatever tools you want to fix your own bike. It's awesome!

--
K.

Lang may your lum reek.

On Fri, 13 Dec 2013 14:08:30 +0000, Király wrote:

Stephen Bauman wrote:
Is this a front or rear wheel. If rear wheel, which side?

Front. I've concluded that 70 kgf is too low if the max spec is 122 kgf.
I'll go back to the shop and tighten up the spokes a little more.


snip


Did you take your spoke tension measurements with the tire on (inflated
at full pressure) or off?

Stephen Bauman

On Thursday, December 12, 2013 12:33:53 PM UTC-8, wrote:
oh yeah costs. buying Swiss costs twice what buying Mx or Chinese/Asian costs so the Swiss rim costs what the entire wheel is at REI.



Now uragonna tell us the DT rim is better than the Rhyno...why ?


I have no notable experience with either rim, and my point is
rhetorical since I am not made of money, but in general I have
the impression that...

The "enlightened societies" foster personal values that are more
in tune with Things That Really Matter (TM). I know this is vague,
and I know we're still wondering what this has to do with the
quality of a a widget, but I believe it matters if every step of
the way - from concept to design to development to production to
distribution to maintenance and continuous improvement - is
attended by people with the right attitude.

(I tend to be kind of anthropomorphic, and figure some of the
personality that man-made objects possess likely rubbed off from
the persons that built and used and cared for them, etc. Kinda
crazy, I know; but it is what it is :-)

METALLURGY !

PROCESSING !

FABRICATION !

Those are the "all else being equal" factors, right?

snip

Stephen Bauman wrote:
Did you take your spoke tension measurements with the tire on (inflated
at full pressure) or off?

No tire. I've compared the pitch of a plucked spoke with those on a
similar 36-spoke rear wheel I've had since 1997, built by a pro shop,
and never gone out of true. The pitches are a little lower than the
non-drive side and a lot lower than the drive side. Will tighten.

--
K.

Lang may your lum reek.

On Fri, 13 Dec 2013 16:17:08 +0000, Király wrote:

Stephen Bauman wrote:
Did you take your spoke tension measurements with the tire on (inflated
at full pressure) or off?

No tire. I've compared the pitch of a plucked spoke with those on a
similar 36-spoke rear wheel I've had since 1997, built by a pro shop,
and never gone out of true. The pitches are a little lower than the
non-drive side and a lot lower than the drive side. Will tighten.

1. Tire pressure compresses rim and thereby decreases spoke tension.

2. You want the spoke tension not to exceed the rim manufacturer's spec
with no tire. Reason: the rim spec is to prevent rim from cracking at
spoke holes. So, you prevent cracking at worst case by measuring spoke
tension with tire off.

3. If spoke tension in your "finished" wheel with no tire is
significantly below rim spec, you want to mount/inflate a tire and
recheck your tension. Your "finished" wheel may have insufficient spoke
tension.

4. The usual rule of thumb is that front wheel spokes and rear driving-
side spokes have same tension.

Stephen Bauman

On 14/12/13 05:29, Stephen Bauman wrote:
On Fri, 13 Dec 2013 16:17:08 +0000, Király wrote:

Stephen Bauman wrote:
Did you take your spoke tension measurements with the tire on (inflated
at full pressure) or off?

No tire. I've compared the pitch of a plucked spoke with those on a
similar 36-spoke rear wheel I've had since 1997, built by a pro shop,
and never gone out of true. The pitches are a little lower than the
non-drive side and a lot lower than the drive side. Will tighten.

1. Tire pressure compresses rim and thereby decreases spoke tension.

2. You want the spoke tension not to exceed the rim manufacturer's spec
with no tire. Reason: the rim spec is to prevent rim from cracking at
spoke holes. So, you prevent cracking at worst case by measuring spoke
tension with tire off.

3. If spoke tension in your "finished" wheel with no tire is
significantly below rim spec, you want to mount/inflate a tire and
recheck your tension. Your "finished" wheel may have insufficient spoke
tension.

4. The usual rule of thumb is that front wheel spokes and rear driving-
side spokes have same tension.


And if you use half as many spokes on the rear NDS than the DS, their
tension will be almost the same as the DS spokes.

--
JS