The Basics of Wheel Alignment and Wheelbuilding

The spoke head will bed into an aluminium hub flange of its own accord.
Ride bike hard and nip up a little if found necessary.
TJ


Trevor Jeffrey wrote in message ...

Peter Cole wrote in message 5PqPc.195614$a24.110765@attbi_s03...

Practically speaking, whether momentary overloading increase spoke fatigue
life by reducing residual manufacturing stresses or by "bedding in" the
spoke/flange interface is immaterial, as long as it works, it's a
procedure
that should be followed.

I do not believe that all constructors using the method of
overtensioning spokes have had an equal benefit. As I have said
previously,
overtensioning, accidentally, partially forms the bend in the spoke at the
crossing point so as to reduce the angular displacement at the hub during
the cyclic variation of loading. With a reduced angular displacement at
the
hub interface the MTBF is increased due to the lowered rate of fatigue.
The
fatigue rate is primarily dependant upon the angular displacement and not
the tensile force or variation in thereof.
Relatively the momentary overloading is a waste of time compared to
specifically shaping the spoke correctly.
TJ

Weisse Luft wrote in message ...
That spoke takes a
compressive load, manifested as a decrease in tension. And the wheel
is under a compressive load from the sum of the sopke tensions but it
also can take a tensile load, manifested by a reduction in the
compressive stress.

Please mind your language. A decrease in tension is not compression. It
cannot be so. It is the rim which is under a compressive load and the
spokes under a tensile load, it is therefore wrong to declare the whole
wheel as under a compressive load. You are confused.
TJ

Trevor Jeffrey Wrote:
Weisse Luft wrote in message ...
That spoke
takes a
compressive load, manifested as a decrease in tension. And the wheel
is under a compressive load from the sum of the sopke tensions but it
also can take a tensile load, manifested by a reduction in the
compressive stress.

Please mind your language. A decrease in tension is not compression.
It
cannot be so. It is the rim which is under a compressive load and the
spokes under a tensile load, it is therefore wrong to declare the
whole
wheel as under a compressive load. You are confused.
TJ

No, I am not confused. If you know how to draw a free body diagram,
you will see the error in your ways if you can accurately measure the
rim deflection.

Pretensioned structures easily confuse those who study them. Rest
assured, a wheel stands on its spokes, be they wire, rope or pegs.


--
Weisse Luft

"Weisse Luft" wrote in
message ...

Peter Cole Wrote:
"
Practically speaking, whether momentary overloading increase spoke
fatigue
life by reducing residual manufacturing stresses or by "bedding in"
the
spoke/flange interface is immaterial, as long as it works, it's a
procedure
that should be followed. For the "bedding" theory to be correct, it
would
require that the bulk material in both the spoke and flange to be taken
beyond
yield. I don't think that's the recommended practice. Your version of
"bedding", since it involves higher forces, would necessarily also
perform the
reduction of residual stresses, so the claim that it works by that
particular
mechanism would seem impossible to prove. In fact, those of us who
don't
stress relieve to yield, yet observe improved spoke lifetimes, would
seem to
have experiences which refute that theory.

Yielding occurs only in a partial cross section of the spoke during the
stress relieving process. Because the entire cross section does not go
to yield, the tension can and does remain the same.

Of course. But that's what's wrong with the "bedding" argument, it requires
yield at the elbow and at the flange.

"Trevor Jeffrey" wrote in message
...

Peter Cole wrote in message 5PqPc.195614$a24.110765@attbi_s03...

Practically speaking, whether momentary overloading increase spoke fatigue
life by reducing residual manufacturing stresses or by "bedding in" the
spoke/flange interface is immaterial, as long as it works, it's a procedure
that should be followed.

I do not believe that all constructors using the method of
overtensioning spokes have had an equal benefit. As I have said previously,
overtensioning, accidentally, partially forms the bend in the spoke at the
crossing point so as to reduce the angular displacement at the hub during
the cyclic variation of loading. With a reduced angular displacement at the
hub interface the MTBF is increased due to the lowered rate of fatigue. The
fatigue rate is primarily dependant upon the angular displacement and not
the tensile force or variation in thereof.
Relatively the momentary overloading is a waste of time compared to
specifically shaping the spoke correctly.

I believe what you're concerned about is what Jobst Brandt describes as
"improving the spoke line". The difference being that his concern is bends
(loaded) at the flange and nipple, while you worry about the crossing. The
concept seems the same, only the forces seem larger in the misalignments he
describes.

Trevor Jeffrey:


Jose Rizal wrote in message ...

Just how do you do this, and how do you account for the dynamic loads
put on the wheel which exceed the static rider/bike weight?

Put water into pan, light gas, place egg in water, bring to boil, turn off
gas.
It would help if questions were more spcific than how do you do this?
specifically which part of my explanation do you think requires further
explanation?

The question followed your last statement "tighten to a point where the
riders (sic) full weight does not releive (sic) the bottom spoke"
immediately. It's not hard to figure out which part the question refers
to.

7/5(rider+bike+load) Front wheel loading.

Where does this magic figure come from?

As another answer explains it is a simple matter to tension the wheel a bit
more if the rider finds the wheel wobbly.

Trial and error is what you're suggesting.

What the hell is "a wheel which will fail safe"?

Will not lock up in the frame due to buckling.

There is no such thing. Buckling is largely dependent on the magnitude
and direction of the load on the rim. A large enough load can buckle a
wheel enough to wrap it around your fork.

Since buckling is also load magnitude dependent, "severre" buckling
cannot be avoided if the load is high enough, and especially since you
only tensioned the spokes enough to take up your static weight.

Spoke quality is not an issue.

Plastic spokes will be fine then.

Steel is an excellent material for bicycle spokes. Plastics are not
renowned for their ability to work in tension and I doubt any plastic could
replace the steel spoke. Aramid fibre of course is exceptionally strong and
may provide an alternative at increased cost.

Hence spoke quality is an issue.

jim beam:

Jose Rizal wrote:
jim beam:

it's only the practical issues
of price, of needing a spoke that resists torque sufficiently to be able
to tighten a nipple and indeed, ability to thread a nipple in the first
place that lead to the use of single strand.

This made-up story doesn't even look nor sound good. Spokes still do
twist, and a threaded nipple is not the only way to have an adjustable
tightening mechanism on a rim.

what method do you propose? the threaded nipple method is cheap,
reliable and has stood the test of time. and of course spokes still
twist, but not as much as the equivalent multi-strand. brake cable's
about the same as a spoke, try the comparision.

This has nothing to do with the claim you made befo "it's only the
practical issues of price, of needing a spoke that resists torque
sufficiently to be able to tighten a nipple and indeed, ability to
thread a nipple in the first place that lead to the use of single
strand."


Does it matter that they bend
around pulleys in a constant side-to-side flexing different
than spokes?

yes, and those pulleys cause wear and bending stresses, but that's why
you use multi-strand in the first place.

Hence spokes and cable are not the same "application".

maybe your definiton of tension is different to mine.

Bending stresses do not result in only tension in cables or solid rods.
One side will experience compression. You do not have this issue with
spokes.

also, one strand breaking in a
rope of 100 leaves 99 others - pretty comforting.

Nonsense. If a cable is loaded such that a strand breaks, the effective
cross section of the cable is reduced and hence the load results in a
higher stress for the remaining strands, which will rapidly lead to
failure of the cable. If a strand was broken by other than a load (eg
cut), the same effect on cross section will be observed. You can't cut
a strand on a solid spoke.

read some fracture mechanics. crack propagation in a single piece leads
to failure of the whole. fracture of a single strand does not.

Dodging again. Study some basic engineering. Fracture of a single
strand in a cable decreases the load-bearing cross-section of the cable,
which decreases the maximum load it can withstand. If the break happens
because of a high enough load, the rest of the strands will experience
higher stresses since there are less of them, and the cable will
eventually fail.

next
time you fly, check out the skin of the plane and notice that it's made
of many parts riveted together. is this because manufacturers can't
weld? no, it's because crack proagation in one piece does not propagate
to the whole - it's a policy of fracture containment.

An absolutely ridiculous contention. A plane's skin is NOT a
significant load bearing structure. The FRAME is. An airplane's skin
is riveted for ease of manufacture, assembly and replacement. It has
nothing to do with "fracture containment".

So to you a cable = spoke = airplane skin. These are erroneous
comparisons.

and there's a small
degree of freedom to move between strands which reduces cross sectional
stress considerably.

Again, nonsense. What can move between strands? The only way to move
loads between strands is if the strands are able to move along the
cable's length. This is a bad event since the strands will not take up
the load evenly amongst themselves.

take a cable and cut the end exactly square. then bend it about some
kind of mandrel. notice how the end is no longer square and the strands
are staggered? they move relative one to another. this is why rope is
flexible.

And so? The ends of elevator cables are not free; nor of any cables
used in any load-bearing application. These are crimped/welded/looped
together to prevent movement of the strands relative to each other. One
of the reasons this is done is to ensure that the tensile load is shared
equally amongst the strands.

Peter Cole wrote in message ...

"Trevor Jeffrey" wrote in message
...
I do not believe that all constructors using the method of
overtensioning spokes have had an equal benefit. As I have said
previously,
overtensioning, accidentally, partially forms the bend in the spoke at
the
crossing point so as to reduce the angular displacement at the hub during
the cyclic variation of loading. With a reduced angular displacement at
the
hub interface the MTBF is increased due to the lowered rate of fatigue.
The
fatigue rate is primarily dependant upon the angular displacement and not
the tensile force or variation in thereof.
Relatively the momentary overloading is a waste of time compared to
specifically shaping the spoke correctly.

I believe what you're concerned about is what Jobst Brandt describes as
"improving the spoke line". The difference being that his concern is bends
(loaded) at the flange and nipple, while you worry about the crossing. The
concept seems the same, only the forces seem larger in the misalignments he
describes.

I am concerned about the movement of the spokes during the wheel's
cyclic rotation and associated variance in spoke loading leading to that
movement. I am also concerned about the lateral stability of the rim. The
failure point is not the source of the problem. The fatigue failure of
spokes at the hub interface will generally be due to not pre-forming the
spoke at its crossing with the result that the crossing point moves in and
out with cyclic load variance, and also torque applied to the rear wheel,
bending the spoke at its contact point with the hub. Same as snapping a
paper clip, bend it back and forth many times and it breaks.

On wheels with spokes not shaped at the crossing point.
If you take a straight edge to your 32x3 or what have you, lay it upon a
spoke and slacken off a nipple, you will clearly see the spoke bend into the
path of least resistance. Not a nice clean straight line required of a
tensile component but loopy. When tight, the forces still remain, as each
spoke in a pair fights against its brother. The tighter spoke will push
harder and the not so tight will give because it is acting as a spring
instead of a tensile member.
If the spokes are pre-formed the spokes stop behaving as springs and
the lateral stability of the wheel is much improved along with increased
spoke life.
TJ

Jose Rizal Wrote:

Bending stresses do not result in only tension in cables or solid
rods.
One side will experience compression. You do not have this issue with
spokes.
...Dodging again. Study some basic engineering. Fracture of a single
strand in a cable decreases the load-bearing cross-section of the
cable,
which decreases the maximum load it can withstand. If the break
happens
because of a high enough load, the rest of the strands will experience
higher stresses since there are less of them, and the cable will
eventually fail.
...An absolutely ridiculous contention. A plane's skin is NOT a
significant load bearing structure. The FRAME is. An airplane's skin
is riveted for ease of manufacture, assembly and replacement. It has
nothing to do with "fracture containment".

So to you a cable = spoke = airplane skin. These are erroneous
comparisons.
...
And so? The ends of elevator cables are not free; nor of any cables
used in any load-bearing application. These are crimped/welded/looped
together to prevent movement of the strands relative to each other.
One
of the reasons this is done is to ensure that the tensile load is
shared
equally amongst the strands.

If you EVER get compression in a strand of wire rope (cable is for
television), I want to be far away because something BAD is going to
happen. Wire rope unwinds when you put it in compression. Wire rope
has a lower elastic modulus than say a spoke. Someone needs to read up
on Roebling et al.

Its unlikely that failure of a single strand in a wire rope will cause
any failure given the lower elastic modulus of wire rope. Yes, you can
make it fail but the analogy here is not accurate.

And yes, an airplanes skin IS an IMPORTANT part of the total structure.
I learned this back when I was a kid building model sailplanes. The
structure is WEAK until the covering (silkspan, fabric or any of the
shrinkable Mylar films) is applied, shrunk and painted. When the wing
is positively loaded, the tension in the top is partially relieved
while that on the bottom surface increases. For ultra high performance
aircraft, the first third or so of the wing is sheeted in balsa, obeechi
or light ply because no covering is strong enough for the compression.
Enough aircraft, I forgot more than you know now.

Wire ropes are ALWAYS wound with tension to ensure the inner strands do
not go into compression. Since the wire is helical, the stresses are
normalized except for the CORE which is usually INDEPENDENT as in
Independent Wire Rope Core (IWRC).


--
Weisse Luft

One spoke without pre-tensioning is more than adequate to support my static
weight

Dynamic loads
If the wheel is built to cope with a load of 7/5(rider + bike + luggage)
this will be found to be adequate on a road bike. The capability of the
wheel is simply tested with a weight equivalent to the calculated maximum
force. The calculation is based on maximum wheel load attained on a front
wheel during braking assuming a co-efficient of friction of almost 1 on a
flat road(use of trigonometry). Maximum braking in a bend with positive
banking may see this force may exceeded. I do not know whether the same
test figure could be used for a track sprinter, but expect it to be not far
off.

Tensioning a wheel with pre-formed spokes.
There is some trial and error until a person becomes practised and
therefore skilled and so knows the particular feel with the spoke key as
when to stop. If the mechanic starts with the spokes just a little bit
tighter than slack then adds 1 turn and tests by placing weight on axle with
rim on floor and it is found to be loose add 1/2 turn to all nipples. The
torque required to turn the nipples will quickly increase and be felt in the
fingers. This is the time to make any truing up, winding in the odd, not so
tight spokes, as necessary, which will be found much easier than with spokes
not pre-formed. Test again, add 1/4 turn if necessary. When suitably
tensioned it should be found that all nipple movements will have an effect
on rim position. Stiff , heavy rims may make this difficult to see without
some form of indicator.
The mechanic, after satisfying himself than all spokes are working
equally, judged by equal rim movement with nipple turn, and that the rim
will support the riders weight without reduction in lateral stability,
judged by attempting to wiggle the bottom nipple in the spoke hole, can
allow the rider to take a test ride.
If the rider returns and says the wheel was wobbly, add 1/4 turn to all
nipples and true up. try again or add load, ask rider to ride harder. If
at any time the rider feels a wobble it is simple to add 1/4 turn and true
up. A skill is something learnt with practice, and lots of testing and
re-testing will be eliminated with experience of the method. Familiarity
with the components using will also help to cut down the number of steps
and uncertainty which accompanies any new method and associated skill. The
use of the dynamic load calculation with static test would be the preferred
method for a professional wheelbuilder.
The likelihood of a wheel buckling that will lock up in the frame is
greatly reduced with my preferred method of building a wheel, as the
technique results in a wheel with a greater lateral stability and the lower
compression levels in the rim allow a greater overhead available for dynamic
load due to impact.
Commonly available cheap steel spokes are required. It is unnecessary
to seek out a particular brand or type.

The load required to buckle my regular wheels would most probably bend the
forks or frame first.
TJ