Kevlar Spokes

ed said:

I keep hearing about emergency kevlar spokes but can't find in my area. Just who is carrying
this item?

We've got 'em. See: sheldonbrown.comspecial.htmlOpen ↗

Sheldon "Bullet Resistant" Brown +-----------------------------------------+
| The wind and waves are always on the | side of the ablest navigators. | --Edward Gibbon |
+-----------------------------------------+ Harris Cyclery, West Newton, Massachusetts Phone
617-244-9772 FAX 617-244-1041 harriscyclery.comharriscyclery.comOpen ↗ Hard-to-find parts shipped Worldwide
captainbike.comcaptainbike.comOpen ↗ sheldonbrown.comsheldonbrown.comOpen ↗

"Sheldon Brown" <[email hidden]> wrote in message
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Quoted message said:

ed said:

I keep hearing about emergency kevlar spokes but can't find in my area.

Would you be able to lace a wheel entirely with kevlar cords? And have it be useful/long-lasting?

--
Phil, Squid-in-Training

"Phil, Squid-in-Training" <[email hidden]> wrote in message

Quoted message said:

Would you be able to lace a wheel entirely with kevlar cords? And have it be useful/long-lasting?

Kevlar has poor fatigue characteristics.

In article <[email hidden]>, [email hidden] says...

Quoted message said:

Would you be able to lace a wheel entirely with kevlar cords? And have it be useful/long-lasting?

IIRC, John Tomac use to ride such a wheel. Besides the cords, it also had an outside cover making it
into a disc wheel. I have no idea if they were durable, but I don't recall seeing any recently.
-----------------
Alex __O _-\<,_ (_)/ (_)

Andrew Lee said:

"Phil, Squid-in-Training" <[email hidden]> wrote in message

Quoted message said:

Would you be able to lace a wheel entirely with kevlar cords? And have it be
useful/long-lasting?

Kevlar has poor fatigue characteristics.

Were are the facts on this statement? Having worked with Kevlar I would never had thought this
to be true.

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Phil said:

Would you be able to lace a wheel entirely with kevlar cords? And have it be useful/long-lasting?

Maybe. Chafing of the surface fibers could be an issue, and might be why composite-spoked wheels
have used resin to encapsulate fibers into a somewhat-rigid spoke. Spoke stretch (and therefore
wheel rigidity) would almost certainly be a problem, and it's difficult to imagine what advantages
such construction might have to offset its higher material and development costs compared to a
conventional wheel.

Spinergy Spox are one example of wheels made with synthetic fiber spokes. The earlier Sugino Tension
Disc used a web of aramid cords radiating out in several diractions from each nipple, with the whole
web for each side sandwiched in plastic film.

Chalo Colina

"S. Delaire "Rotatorrecumbent"" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

Kevlar has poor fatigue characteristics.

Were are the facts on this statement? Having worked with Kevlar I would never had thought this to
be true.

I guess to be accurate, it would be better to say how it is used. I got this impression from a
climbing perspective, where it is fairly common knowledge that kevlar has poor flex fatigue and is
that is a consideration for cord where there is constant flexing. Thus you wouldn't want to tie and
untie knots in the cord regularly, but you can tie it once into a loop for your Hexes (a form of
rock protection or anchor). You can google this for more information... I also found references to
it loosing strength in sail cloth applications (where they also found Kevlar had problems with long
term UV exposure, a problem that can be overcome though I think). I'll leave it up to you to google
for perhaps a more scientific paper with testing...

I also found these old Jobst posts:

Ed Chait said:

I would think that at least on a single speed, or fixed gear bike, a narrow, toothed Kevlar belt
and aluminum sprockets would be lighter, cleaner, quieter and never require lubrication. I'm sure
a belt drivetrain has been tried before. Why has it never caught on?

It's good you say that in the subjunctive, there being no proof that it is possible or practical.
Kevlar is definitely not the medium, it fails in fatigue as soon as it absorbs a little moisture,
and it IS hygroscopic. Kevlar has limited uses and timing belts is not one of them.

Jobst Brandt G? said:

Quoted message said:

Yes, that's the kind I also had in mind when replying, and it is such belts where the Kevlar
fibers break in fatigue with the absorption of humidity. I doubt that anyone makes timing belts
with Kevlar these days. Their frailty must be common knowledge in the business.

A quick Excite net search revealed quite a few companies with sales info for Kevlar reinforced
belts. Maybe it's not a major problem for certain products or conditions. I'd be curious to
learn more.

We don't know where the Kevlar is and how it is used. It's somwhat like the sticker "Intel Inside"
on a product.

Quoted message said:

Jobst - do you have quantitative data, references or experience that would be informative for the
rest of us ?

I was involved in the development of paper moving plotters at HP before their ink jet plotters.
These plotters used timing belts to move the carriage and paper (X&Y). We tested all sorts of belts
and discovered that, in the humidity chamber, all Kevlar belts failed. We used conventional Rayon
backed belts after that with no trouble.

No papers were published on these findings, they being insignificant in that sort of work.

Jobst Brandt [email hidden], it may be that Kevlar is not "bad" in fatigue characteristics
when used in pure tension,it is doubful that it can compare to steel operating at stress below the
fatigue limit. I amnot familar with how the fibers would be secured at the ends, but if there are
lots of bendsthat might cause problems with the constant stress cycling of loading rolling wheel...I
don't know for sure though. In what applications have you worked with Kevlar?

"Phil, Squid-in-Training" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

"Sheldon Brown" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

ed said:

I keep hearing about emergency kevlar spokes but can't find in my

area.

Quoted message said:

Would you be able to lace a wheel entirely with kevlar cords? And have it be useful/long-lasting?

--
Phil, Squid-in-Training

Sugino T-Disc ( aka Tioga T-Disc) were 256 kevlar strands mounted in a mylar sheet. They were
32-hole format for use with a standard hub and rim and worked just fine. They were actually lighter
than 32 spokes. Really. yellowjersey.orgwheel.htmlOpen ↗
--
Andrew Muzi www.yellowjersey.org Open every day since 1 April, 1971

(TBGibb) said:

There is a wheel like that, the Topolino, page 30 in the Colorado Cyclist catalog. The
kevlar/carbon spokes "span the entire wheel" and are held to the hub by a sleeve (personal
observation while drooling in CC's showroom). The tension goes from side to side of the rim with
very little tension on the flange. No more elbows to break. I've no clue as the durability and will
certainly not be the first one on the block to have personal experience with a set of them.

I wonder what would happen if, as a physics experiment, you laced a wheel with a single steel cable,
using appropriate sized pulleys at the hub and the rim, and a single inline tension adjuster at one
point. The pulleys would have to have fairly heavy duty bearings to roll under 200 kg tension,
though, I don't think a bushing is gonna do that trick. On the other hand, even at relatively severe
deflections of the rim, the pulleys would have very little actual movement to do in order to
equalise the spoke tension across the wheel.

Hmm. If 'spoke' tension is always equal on each of the spokes, then there's no force holding up the
hub, and thus the hub would fall down to the ground instead of being held up.

Oh well, there goes my experiment.

Jasper

Quoted message said:

Oh well, there goes my experiment.

I think it would always be sagging because tension would hold it up. Equal spoke tension means that
if you have an out-of-true wheel, it will always be out of true and you won't be able to correct it.
Bah, just run it with discs! 😉

--
Phil, Squid-in-Training

Quoted message said:

Sugino T-Disc ( aka Tioga T-Disc) were 256 kevlar strands mounted in a

mylar

Quoted message said:

sheet. They were 32-hole format for use with a standard hub and rim and worked just fine. They
were actually lighter than 32 spokes. Really. yellowjersey.orgwheel.htmlOpen ↗

Hey cool - I see my idea has some validity!

--
Phil, Squid-in-Training

Jasper Janssen said:

I wonder what would happen if, as a physics experiment, you laced a wheel with a single steel
cable, using appropriate sized pulleys at the hub and the rim, and a single inline tension adjuster
at one point. The pulleys would have to have fairly heavy duty bearings to roll under 200 kg
tension, though, I don't think a bushing is gonna do that trick. On the other hand, even at
relatively severe deflections of the rim, the pulleys would have very little actual movement to do
in order to equalise the spoke tension across the wheel.

Hmm. If 'spoke' tension is always equal on each of the spokes, then there's no force holding up the
hub, and thus the hub would fall down to the ground instead of being held up.

Oh well, there goes my experiment.

As someone pointed out in email, I missed an important thing: As the hub does its sagging, the
"spoke"/wire angles change and provide a net force upwards. So the wheel should behave more or
less[1] as the rigid-rim/rubber spoke model: as you're riding along, the hub will be positioned
slightly (or maybe a lot) below the center of the rim.

Jasper

[1] In several ways less, of course.

I am in search of a Tioga T-Disc or Sugino T-Disc for MTB like the ones formerly used by Tomac and Overend in the early 90's. If you have one new or used please contact me. Willing to pay a good premium. Green for you, smiles for me. Thanks!

Tucker Snedeker
TS1 @ Mountainbikes.net
630-435-6353

Quoted post said:

Originally posted by Jasper Janssen

BOn Fri said:

I wonder what would happen if, as a physics experiment, you laced a wheel with a single steel
cable, using appropriate sized pulleys at the hub and the rim, and a single inline tension adjuster
at one point. The pulleys would have to have fairly heavy duty bearings to roll under 200 kg
tension, though, I don't think a bushing is gonna do that trick. On the other hand, even at
relatively severe deflections of the rim, the pulleys would have very little actual movement to do
in order to equalise the spoke tension across the wheel.

Hmm. If 'spoke' tension is always equal on each of the spokes, then there's no force holding up the
hub, and thus the hub would fall down to the ground instead of being held up.

Oh well, there goes my experiment.

As someone pointed out in email, I missed an important thing: As the hub does its sagging, the
"spoke"/wire angles change and provide a net force upwards. So the wheel should behave more or
less[1] as the rigid-rim/rubber spoke model: as you're riding along, the hub will be positioned
slightly (or maybe a lot) below the center of the rim.

Jasper

[1] In several ways less, of course. [/B]