wheelbuilding question

Tom Sherman wrote:
Jonesy wrote:
I rode around and did my best to put side loads on the wheels....
How does one do this on a single-track vehicle?

Get out of the plane of the bike, so you lean to one side and the bike
leans to the other, with your CoG (obviously) still above the wheel track?
--
David Damerell Distortion Field!

Jonesy wrote:

Tom Sherman wrote in message ...

Jonesy wrote:


...
I rode around and did my best to put side loads on the wheels....

How does one do this on a single-track vehicle?


I am assuming you are asking a serious question.

Every turn you make generates some side load on the wheel. Otherwise
you wouldn't turn. Have you ever seen cyclists who move the bike from
side to side as they pedal? That also generates wheel side-loading.
I did side-to-side hops, hard turns, and the pedalling I describe.

I'm not sure if my regular MTB trails would put as much stress on the
wheels, but that test is next.

However, when a single-track vehicle is leaned to one side, it also
turns in that direction, greatly reducing the lateral loadings on the
wheels. While these cycling maneuvers will certainly produce some
lateral loading to the wheels, the magnitude would not be that great.

If you want to put some significant lateral loads on a spoked wheel, I
suggest cornering at high speed on tadpole trike with a low center of
gravity.

--
Tom Sherman – Quad City Area

Jonesy wrote:

Tom Sherman wrote in message ...

Jonesy wrote:


...
I rode around and did my best to put side loads on the wheels....

How does one do this on a single-track vehicle?


I am assuming you are asking a serious question.

Every turn you make generates some side load on the wheel. Otherwise
you wouldn't turn. Have you ever seen cyclists who move the bike from
side to side as they pedal? That also generates wheel side-loading.
I did side-to-side hops, hard turns, and the pedalling I describe.

I'm not sure if my regular MTB trails would put as much stress on the
wheels, but that test is next.

However, when a single-track vehicle is leaned to one side, it also
turns in that direction, greatly reducing the lateral loadings on the
wheels. While these cycling maneuvers will certainly produce some
lateral loading to the wheels, the magnitude would not be that great.

If you want to put some significant lateral loads on a spoked wheel, I
suggest cornering at high speed on tadpole trike with a low center of
gravity.

--
Tom Sherman – Quad City Area

jim beam wrote:
Mark McMaster wrote:

jim beam wrote:

Mark McMaster wrote:

Indeed, you're supposition that "increasing spoke tension makes
absolutely no difference in lateral strength" is directly
contradicted by Rinard's conclusion from his test. From the web
page referenced above:

"A wheel whose spokes become slack while riding is a weak wheel,
because slack spokes cannot support the rim. This can be avoided to
a large extent by building wheels with tighter spokes. If spokes are
tighter initially, then the sudden increase in flexibility shown in
data points 9 and 10 is less likely to occur in use because a
tighter wheel can bear a higher load before spokes become slack."




there's no contradiction. the left part of the graph is essentially
a flat line. leftwards is increasing tension. once you're in the
flat line region, increasing tension is not increasing lateral
stiffness.



There's more to it than simply stiffness. The sharp decrease in
stiffness occurs at the point when some of the spokes no longer
contribute to supporting the wheel. You claim seem to claim spoke
slackening make no difference in wheel strength - Damon Rinard claims
it does (and I agree with him).


it makes no difference to lateral deflection while the spokes still have
tension - the flat line part of the graph!!! it's only when the spokes
are slack that any difference in lateral deflection is observed - just
like the tow rope analogy. that's why the graph has two distinct regions.

(Sorry for the late reply - I was away on business last
week.) You have just hit upon the exact reason that spoke
tension affects wheel strength. I think we agree that in
some situations, forces on the wheel during riding can
exceed the yield strength of the rim - for example, hitting
a bump or pothole hard enough can bend the rim. For the rim
to bend, it has to strain (deflect) beyond it's yield point.

As you point out, what Rinard's graph shows us is that when
loaded, there are two distinct regions of deflection - a
high stiffness (low deflection) region when all the spokes
remain tight, and low stiffness (high deflection) region
when some of the spokes slacken. With loose spokes, the
majority of the load is taken up in the low stiffness
region, where there is high deflection for a given load.
With tighter spokes, more of the load is taken up in the
high stiffness, low deflection region, so the total
deflection for a given load will be less. With higher spoke
tension, a higher load is required to reach the yield point
of the rim.

Obviously there are other factors that may limit to how high
the spoke tension can be for a given wheel. But it clearly
apparent that the static spoke tension plays a vital role in
determining the load required to yield the rim.

Mark McMaster

jim beam wrote:
i've read the radial loading argument of high tension [and i know the
difference between strength & stiffness!]. regarding lateral loading,
this adds to the spoke pre tension on one side and subtracts from the
other. radial loads subtract only. if a spoke has a yield strength of
say 300kg, preloading it to 200kg only gives 100kg of lateral load
before yield. if the spokes have 100kg preload, it means they can take
twice as much lateral.

(Sorry for the late reply - was traveling on business last
week.) This argument falls down for several reasons.
Firstly, because of the geometry of the wheel, a lateral
load on wheel does not create a proportional load on the
spokes (i.e., a 100 kg side load does produce a 100 kg
change in spoke tension). Secondly, for the vast majority
of wheels, the rim will fail (yield) well before any spokes
do (even in a highly tensioned wheel). And finally, lateral
loads are not present without radial loads - and as we all
know, radial loads serve to lower spoke tension, not raise
it. In standard bicycle wheels, spoke yield strength is not
the limiter on static spoke tension.

Mark McMaster