do dishless wheels ride differently?
Jan Steinman
...Am I imagining things, or is it possible that having nearly
identical tension in the spokes on both sides of a wheel would make
it behave differently from a wheel with substantially
higher-tensioned spokes on one side -- to a degree I could detect?
I'm sure it would make a difference. I can notice a difference on our
Jack Taylor tandem between a wheel with a disk brake (no dish) and one
without.
I've built heavy touring wheels with 45 spokes -- each freewheel-side
pulling spoke is doubled. I also thought this wheel rode "smoother".
It was still dished, but individual freewheel-side spokes have less
tension then they do on a 36, since there are 50% more of them.
"Plucking" them produces tones that are fairly close to the tones
produced by "plucking" the spokes opposite the freewheel.
My analysis: when hitting a bump on an unequally tensioned wheel, the
"soft" side (opposite the freewheel) is free to absorb the bump more,
causing the that side of the axle to drop slightly, causing the whole
bike to tip slightly to the left.
--
: : Jan Steinman stei...@is.morgan.com Bytesmiths : :
: : 2002 Parkside Court West Linn, OR 97068-2767 : :
: : 503/657-7703 212/956-8722 : :
Thomas H. Kunich
>
>Am I imagining things, or is it possible that having nearly identical
>ently from a wheel with substantially higher-tensioned spokes on one side --
>to a degree I could detect?
Yep, it's your imagination. While the tension on the spokes is
different, the loadings on the rim are the same.
John Whitmore
That isn't relevant; the rim is nearly rigid, it's the SPOKES
that can flex under stress. Since the spokes' behavior is determined
by their tension, the tension difference changes the coupling
between the axle and rim (in particular, by making the response to
torque less stiff than for a symmetric wheel).
John Whitmore
Charles Fineman
Hmmm. Wouldn't make a difference when lateral forces are applied to
the wheel?
Chuck
--
kis...@iowave.physics.uiowa.edu
I agree that it's the spokes that flex. Spokes with less tension can flex
more. So you get a softer ride, possibly at the expense of replacing
spokes more often, unless they were overtensioned to start with, which is
usually the case on a dished wheel.
The symmetry of the wheel is irrelevant, since (one would hope) your axel
and flanges are at least as rigid as the rest of your bike (and probably
a lot more considering how small they are by comparison). I'm not
convinced that someone might really notice the difference in the ride,
however, no matter how well calibrated your butt might be.
Allen Kistler
kis...@iowave.physics.uiowa.edu
Phil McCalley
>Over the weekend I retrued my rear wheel, which now has a 130mm axle, to
>take advantage of the fact that I'm only using ultra-six freewheels and so
>don't need much room on the right side. The result was a wheel with
>virtually no dish.
>Then yesterday I rode it down a steep, bumpy, twisty descent, and noticed
>that the bike felt more securely attached to the road. Nothing else about
>the bike had changed since the last time I'd done that hill.
>Am I imagining things, or is it possible that having nearly identical
>tension in the spokes on both sides of a wheel would make it behave differ-
>ently from a wheel with substantially higher-tensioned spokes on one side --
>to a degree I could detect?
>(BTW, the wheel was perfectly true before I started working on it, so any
>change I may have detected did not have to do with no longer being on a
>wobbly wheel.)
>--
Maybe every spoke was tighter, and with your wieght on it, it made a
difference. I used to call this tightening the spokes. Never did ride
no fancy shmancey bye-cycle. In my day, we didn't used to have no
seats. We went off jumps and poked holes in our butts, and that's the
way it was, and we liked it. And after a hundred or so jumps, when our
butts was all bleedin' and messed up, they spokes was loose. We tightened
them spokes up best we could, and went of some more jumps till our butts'
was like red swiss cheese. Thats the way it was, and we...loved it!
--
....................................................... Phil McCalley
David Keppel
>[The axles in my hubs, BTW, are 12mm-thick aluminum, and their
> maker, Bullseye, claims to have had a single bent axle in nearly
> 20 years of producing hubs with the same axles for tandems and mt.
> bike/BMX uses. The ease with which I was able to change my axles,
> about 2 minutes start to finish, convinces me that they are well
> designed.]
A friend of mine just got some for his tandem. They say they have
been making the hubs since 1976, introduced new axles for BMX in
1978, and since then they have seen two bent axles and no broken
ones. I've gone through more than that in conventional steel axles.
I will echo Eric's praise for the design: it is simple and seems to
last well. The axles come drilled and tapped for Allen-head bolts
(included) and you can use either the bolts or a conventional QR.
Allen-head bolts are also used in Phil Wood hubs, but you can't
switch back and forth on the Phils.
Allen-head bolts maybe don't make sense for racers, but I think they
are a good alternative for everybody else: they hold the wheel more
firmly than a QR, they can't be fiddled with by passers-by, a thief
needs to carry a tool to walk off with the wheel. Yet with an Allen
wrechn you can remove the wheel in 15 seconds to fix flats, mount the
bike on a rack, stow it, etc. Further, the Allen-head bolts plus an
Allen key is lighter than a standard QR and probably lighter than
fancy expensive QRs.
Bullseye hubs are simple but are as expensive as many other
high-quality hubs. They seem to go for around $120/pr, more for hubs
in fancy colors (you can get hub parts in about a dozen colors, and
you can have each of the the three hub pieces made in a different
color e.g., red, white, and blue).
They use cartridge ``sealed'' bearings. They claim they are a common
size and can be found in-stock in many bearing supply stores. The
bearings are easy to remove and replace, but one is glued using
Loctite(tm) or the equivalent -- I really don't know why. So to
replace the bearings, you're really supposed to have both the actual
bearing cartridges and the glue.
For gram freaks: A couple hours ago I weighed a 135mm-axle Bullseye
rear at 222g. For comparison, that's on par with conventional road
rear hubs; the lightest hub I know of is a Hi-E front track hub at
about 85g.
Please direct followups to the appropriate place -- tech for design,
marketplace for comparisons.
;-D oN ( Bulls* hubs ) Pardo
Peter C. Simpson
> In article <1992Aug25.1...@u.washington.edu>,
|> I agree that it's the spokes that flex. Spokes with less tension can flex
|> more. So you get a softer ride, possibly at the expense of replacing
|> spokes more often, unless they were overtensioned to start with, which is
|> usually the case on a dished wheel.
|>
Not exactly correct. Spokes act like metal strings - they are very flexible,
and provide support only in tension, so the spokes wouldn't flex (bend)
they would stretch. If we assume all spokes are pre-loaded enough that
they are always under some tension, then spokes of different tension would
stretch the same amount, under a given load. They are all operating in the
linear portion of the stress-strain curve, so a given increase in
stress at any point on the curve will produce a constant amount of strain
(stretching).
The difference in flex will be determined by the geometry of the dishing.
The portion of spoke tension that will resist lateral movement relative
between the axle and the rim is the equal to the sine of the angle of the
spokes on that side frokm the plane of the rim. So, if spokes on the left side
have an angle of, say 5 degrees (30 mm offset on a 685 mm dia wheel) and the
spokes on the dished side have an angle of only 2.5 degrees (15 mm offset),
the same lateral force would create twice as much increase in spoke tension
(and therefore twice as much stretching) when applied from the non-dished
side as opposed to the dished side. Note that when I push on the end of the
axle, the spokes on the OPPOSITE side are resisting this force - the
spokes on the side I am pushing on are already pushing in that direction,
and are more than happy to unload themselves as I apply my load.
The magnitude and cause of these lateral forces is not completely
trivial to determine, but I think we all agree that they exist.
BTW, from this discourse we can see that spoke tension in the dished side
will be higher than that in the non-dished side, in proportion to the
difference in spoke angles.
|> The symmetry of the wheel is irrelevant, since (one would hope) your axel
|> and flanges are at least as rigid as the rest of your bike (and probably
|> a lot more considering how small they are by comparison). I'm not
|> convinced that someone might really notice the difference in the ride,
|> however, no matter how well calibrated your butt might be.
|>
|> Allen Kistler
|> kis...@iowave.physics.uiowa.edu
simPSon
Peter Simpson
Product Design Manager
Network Computing Devices