From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: DT rev. spokes vs all else
Date: 15 May 1998 01:31:03 GMT

Rafael Raban writes:

> I couldn't believe it when I saw it!  Given the crack's orientation,
> though, I wouldn't expect the spoke to fail there.  In fact, I've
> never heard of a spoke failing in that way under normal use....
> however, this may explain the holes in Jobst's ceiling!

This is while tightening the they broke.  It is the combined stress of
tension and torsion that causes the failure.  That is why I advise
against tightening spokes that are in line with your face, a common
position that wheel builders assume.  Even then, the face is often in
the plane of the wheel.  It is reasonable to assume that if the spoke
didn't break when being twisted, that it won't break from tension
alone, so you are probably safe if you don't turn the spoke in front
of your face.

I think you ought to send DT your URL so that they might review what
you found.  I doubt they looked at this discourse on the net and are
unaware of this.

http://www.aliasnet.it/pub/dt/

Jobst Brandt      <jbrandt@hpl.hp.com>

From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: Metal Fatigue Failure of Bike Wheel Spokes- Myth or Not?
Date: 7 Oct 1998 21:43:03 GMT

Hajaj writes anonymously (from the green room):

>>> So, if are riding a 'branch-free' course and don't need to toss
>>> your bike in the back of the car, you could get away with using
>>> much thinner spokes, couldn't you?

>> Well, you'd have to find a way to tension it.  Besides, there are
>> many wheels being used today that are close to the limit with
>> little reserve, the reserve you seldom recognize as your savior in
>> an awkward bump or slide.  Besides, one broken spoke should not
>> disable your bicycle.  Unfortunately with the highly asymmetric
>> wheels used today with closely spaced flanges, this is not the
>> case.  Most of the margin has been used up on the CAD system before
>> hub ever becomes a wheel.

> I must have misunderstood, I thought you said that with normal
> spokes, the tension that would collapse the rim, is nowhere near
> that which would snap a spoke.

No, the rim will be near its yield strength.  Unless you are using a
wheel with fewer than 32 spokes, the spokes will be not much above 50%
of yield.  They may snap just the same because tensioning them higher
than that puts a strong twist on them and the combined stress can snap
them.  That is why 1.5mm diameter swaged spokes went out of fashion
more than 20 years ago only to return now.

> About tensioning, I assume the problem is spoke windup. It seems to
> me it would be simple to make a pair of pliers that could grip the
> spoke while you tighten the nipple.

It is a combination of torque and tension that breaks the spoke, but
it may be more than half torque and rapidly increasing as the spoke
becomes thinner.  If you ever tried it, you will know that you cannot
hold a spoke unless you hold it with toothed jaws that dig into the
spoke.  This causes fatal damage to the spoke.  That is why it isn't
done.  Some spoking machines can press the rim inward, temporarily
unloading the spoke for nipple adjustment.

> I was thinking you might even make a combined tool. Perhaps
> something with a trigger.  When you pull the trigger half way the
> tool clamps onto the spoke, when you pull it the rest of the way it
> turns the nipple an adjustable amount, say between 1/2 and 1/8 turn.
> It might even be a quicker and more accurate way to tension your
> wheel.

I don't believe so.  If you are going to get that complex, you had
best use a machine that does the whole thing.  The 24 spoke wheels I
have built, tighter than normal tightening will permit, were done by
pulling the rim to one side while adjusting.  This is done in a rigid
wheel truing fixture that allows such side loads.  This works but is
tedious.

Jobst Brandt      <jbrandt@hpl.hp.com>

From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: Spoke strength question
Date: 13 Nov 1998 19:33:36 GMT

Chuck Schmidt writes:

>> Flat spokes are expensive and difficult to tension because they
>> have practically no torsional stiffness and easily wind up into a
>> twisted band.

> On the other hand...flat spokes are very easy to put an adjustable
> wrench on to keep the spoke from twisting...hee hee (repeat, this is
> not a troll)

This method will easily but a twist-kink in the spoke where it enters
the jaws of the wrench.  If the spoke does not withstand the torque of
tightening, then the short piece of transition outside the wrench will
also twist.  The only good method for tightening flat spokes is to
deflect the rim do temporarily de-tension the spoke while it is being
adjusted.

Holland-Mechanics wheel truing machines have this capability, most
manual builders do not.

Jobst Brandt      <jbrandt@hpl.hp.com>

From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: Truing wheels, spoke wrench
Date: 16 Jun 1999 20:46:58 GMT

Glenn Trent writes:

> [Park Tool] Black is 127, Green is 130, Red is 136 and there is a
> really fat one, 156, for BMX and/or lawn mowers or something.  I
> have the Black, Green and Red Park spoke wrenches, but recently a
> local bike shop (Franklin Street Cyclery) recommended a
> multi-spoke-size tool from Wrench Force (Snap-On), #59603.  I was
> skeptical at first, because I've never before seen a multi-size
> spoke wrench that was anywhere near as functional and convenient as
> the Park tools.  I mean, a spoke wrench has to fit your hand right
> for serious use, as well as your nipples (did I say that ???).  This
> one, though, is great.  I now use it instead of the one-size-only
> Park tools.  The shop uses them as well.  Park had better be careful
> of Wrench Force tools replacing them with better and cheaper designs

I have used various spoke wrenches but soon realized that a multi-slot
wrench always seems to be at the wrong slot when you aren't just
moving from spoke to spoke.  In that pursuit, I started looking for
ones that are only one size.  I don't work on wheels with several
sizes so I think this is a reasonable compromise, unless you can
finish a wheel in less than five minutes and have others with
different sized nipples.

The one I decided on was the VAR because it has a cylindrical snout
that one can spin with the fingers and it has broad ears that give
good leverage.  The tool is case hardened and slips on to nipples,
having parallel jaws.  Spoke wrenches that engage all four corners of
the nipple, tediously to axially engage the nipple.  Rounding nipples
is a problem I think is better solved by good lubrication than a
pseudo socket wrench.  In any case, I haven't rounded a nipple even
when building low spoke count wheels to the tension limit.

I don't work in a bicycle shop where all sorts of spoke nipples are
encountered so I have two VAR wrenches for the common sizes on road
bicycles.  One is chromed, the other is glossy black oxide finish.

In my tire patch kit, I carry a beautiful two size "dog bone" shaped,
hardened steel, one inch long wrench with the two common sizes, one on
either end.  I found it one day years ago in a deserted motel garage
in the midst of derelict cars and rusty automotive tools.  I'm sure no
one recognized this little jewel for what it was.

Jobst Brandt      <jbrandt@hpl.hp.com>

From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: Wheel question
Date: 1 Oct 1999 20:59:34 GMT

Mike Bales writes:

>> No fault to Sheldon, but Jobst Brandt's book outlines the best
>> method for determining the optimal spoke tension. In effect, it's
>> the maximum tension the rim will withstand. Tighten the spokes.
>> Stress relieve.  Repeat. Eventually, the wheel will start to
>> buckle. If you tighten in half turns, it will not damage the rim.
>> You can tell its starting to buckle when it assumes a slight potato
>> chip shape (about a quarter-inch or so out of true. Back off the
>> spokes one-half turn, true, and ride. This is the maximum tension
>> tolerated by the rim, and gives you the strongest wheel obtainable
>> for that combination of components.

> Oh man that sounds scary.

That could be because you haven't tried it.  This procedure is the
only practical way of assessing what tension to use.  It does not
damage the rim unless you exceed the maximum safe tension and grasp
the spokes with high force the first time you do this.  I came upon
this by accident while building wheels for a friend with 260g Super
Champion Medaille d'Or rims, tightening them to the tension I was
accustomed with 360g rims.  I never got to the stress relieving before
I ruined one of the rims.  That's when I realized that stress relieving
was a good test of tension margin remaining.

> This was a used rim - anodized Matrix Titan Tech.  I'd read some
> comments about the anodizing and the brittleness that may result.

All anodizing is brittle but it only affects the fatigue durability
of the rim by initiating crack growth out of the naturally cracked
surface of the anodizing.  It has no effect on the ultimate strength
of the rim.

> So around the spoke holes (reinforced) I noticed slight
> discolorizations, and don't know if I really observed or imagined a
> slight raise around the hole when I kept tightening.  I was
> concerned I was going to pull a piece out.  I don't know if I would
> be gutsy enough to tighten until I saw a buckle starting.  Is this
> concern warranted?

No.  However, the discoloration is possibly crazing in the anodized
surface.  Don't use anodized rims.  Oh for the "good old days" when
polished aluminum was the preferred finish of the day.  It cost
nothing and it was stronger than all the anodizing for which you can
pay extra.  I can't believe the desire of today's bicyclists to ride
dirty black rims that crack and pay extra for the inconvenience.  The
danger of anodizing structural aluminum parts is documented in the
aircraft industry at length.

> But if I do - let me imagine - at the end of the whole thing, you
> true, tighten a half-turn, and then notice a big out of true
> difference, and then back off to where you where just at.  This is
> right?

All but the "big out of true" part, yes.  The big should be in
reference to the waves of the rim, not the displacement but then you
knew that and said that only for a laugh.

>> Many report their wheels requiring no truing at all in thousands of
>> miles. Wheels go out of true usually because the spokes are too
>> loose, and go slack under load. When they are slack, the nipples
>> can turn.  With proper tension, the spokes won't go slack, and the
>> nipples won't turn. The only time the wheel becomes less straight
>> is if you ding it on something hard-edged.

> Well, it's good to know I built them stronger then when the LBS
> retrued the first set.

I'm not sure what you mean by this, but make those spokes as tight as
they should be.

Jobst Brandt      <jbrandt@hpl.hp.com>

From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: DT-Avocet Tensiometer
Date: 22 Oct 1999 22:30:26 GMT

Roger Musson writes:

> By chance, the new DT catalogue turned up today. It again refers to
> a DT-Avocet tensiometer but has a different photograph. Is this made
> to your design? I put a copy of the photograph at:

> http://www.wheelpro.co.uk/tensiometer.jpg

Yes that is the same instrument and the picture is of a pre-shipment
model because it does not yet have either the Avocet logo at the upper
left nor the DT Swiss logo just under the serial number.  There were
only 125 made and then DT canceled.  People in the US did not think a
tensiometer was worth getting at $250.

As you can see in the photo, the dial can be zeroed with the thumb as
the instrument is placed against the spoke in one hand operation.  The
support bearings and dial probe approach from the same side of the
spoke and the anvil depresses the spoke when released.  Deflections on
such a precision arrangement can be held to less than 0.3mm, the full
scale of the dial being 1mm.  The light load for this does not
materially affect the existing spoke tension as the Hozan with it's
monster force does.  Since it doesn't measure across the spoke
thickness, it can measure all thicknesses and give fairly the same
result for thick and thin spokes, a set of three closely spaces curves
in the conversion chart being for 2, 1.8, and 1.6mm spokes.

> BTW they show a copy of your book in their catalogue "The Bicycle
> Wheel" by the classic American author...

I'm impressed.  I'll have to thank them for that.  I seem to have been
rehabilitated.  My problem was that I said something to the effect
that DT Revolution spokes were going to present tensioning problems
when they were announced, having not yet seen them.  I discovered that
this was not taken lightly when communication between DT and Avocet
ceased and my book and tensiometer vanished from their repertoire.

I am curious how they list my book ($) and whether it is available in
German as it originally was at DT.  I expected to see their own
effort, "The Art of Wheelbuoilding" by Schraner to be there.  I got
both the German and English versions of his book and got them
autographed at the show.  The Englinsh version is a poor translation
and is missing many of the grahics.  However, the content is
essentially the same.

Jobst Brandt      <jbrandt@hpl.hp.com>

From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: Last wheel question, I promise. JB?
Date: 29 Jan 2000 23:11:59 GMT

John Bigboote writes:

> After pestering the group for a few weeks, and reading "The Bicycle
> Wheel" as advised (in one day--a good, quick read, that), I now feel
> I know about 200x more about wheels and wheelbuilding than most
> normal people will need in a lifetime. So I've got that going for
> me.

Thanks for the solid endorsement.

> Anyway, there was one point JB omitted, from the book and from
> earlier threads. He (you?) suggested that building with 1.8mm swaged
> spokes is desirable but difficult--and beyond the skills or patience
> of most builders--because they are more prone to twisting during the
> tensioning process.

Oh, I don't recall saying that anywhere, only that the reason race
teams often use 2mm straight gauge spokes is that they build faster
for lack of windup and have less elastic interaction among spokes.

> So my last inane question is: Wouldn't it be simple enough to grasp
> the spoke near the nipple (on the "butted" part, if possible) while
> tightening, using needlenose pliers or somesuch, thereby eliminating
> the possibility of twisting and ensuring the integrity of the build
> once the wheel is ridden?

This suggestion often comes up and it boils down to that you can't
hold a tight spoke against rotation without damaging the it. I used to
watch Wheelsmith build wheels with smooth jawed pliers until I
challenged Rick to put some post-its on the spokes to see how much
good it was doing... end of exercise.  When you consider how hard it
is to get 2.0-1.5mm spokes tight, you'll understand why not to build
wheels with flat spokes.  The only way to tighten these is to unload
the spoke while adjusting it.  That requires either a radial
hydraulic/pneumatic piston, as Holland Mechanics has on their
machines, or bending the wheel sideways at the spoke to unload it.
This is the method I used to build 24 spoke track wheels.  The fewer
spokes the tighter they must be to hold the load of a rider.

Jobst Brandt      <jbrandt@hpl.hp.com>

From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: Last wheel question, I promise. JB?
Date: 1 Feb 2000 18:42:53 GMT

Mike Jacoubowsky writes:

>> When you consider how hard it is to get 2.0-1.5mm spokes tight,
>> you'll understand why not to build wheels with flat spokes.  The
>> only way to tighten these is to unload the spoke while adjusting
>> it.  That requires either a radial hydraulic/pneumatic piston, as
>> Holland Mechanics has on their machines, or bending the wheel
>> sideways at the spoke to unload it.  This is the method I used to
>> build 24 spoke track wheels.  The fewer spokes the tighter they
>> must be to hold the load of a rider.

> OK, help me out here.  Why is it more difficult to bring a bladed
> (flat) spoke to high tension than a non-bladed one?  I find it much
> easier, since you have a flat surface to hold so it doesn't twist.

There are two parts to this.  1. the torsional stiffness of a shaft is
proportional to the 4th power of the largest inscribed diameter (the
stiffness of an equivalent round wire).  A flat rectangular bar 2x4
like has twice the stiffness of a 2 diameter piece while a single
2-3/8 diameter piece is also twice as rigid.  2. The torsional
strength is not length dependent so that a flat spoke that will
plastically twist will also do so if you hold it near its round end.
The only difference is that it will yield sharply over a short length
if not break off.

> For what it's worth, we use a slotted piece of plastic to hold the
> spoke without damage...real high-tech...any piece of plastic will
> do, you just slot it with a hacksaw.

That may reduce windup, but if the spoke is to be tight, it will
exceed yield.  I don't believe you are making these spokes as tight as
they probably should be.  I have taken my tensiometer to bike shows
and found nearly all flat spoke wheels to have loose spokes.  My
tensiometer is insensitive to spoke thickness for spokes of 2.0 or
less diameter.

> By the way, you're right on the money regarding how to adjust
> tension on spokes that are very tight and resistive to normal means
> (without simply twisting the spoke around).  I find it easiest to do
> this while in the frame, and simply push the rim in the direction of
> the spoke you're adjusting.  Somehow I have a feeling you were doing
> this many years before me!

As you probably know, this works best with rear wheels between the
chain stays where a sideways push is easy to do and the frame is able
to take these loads.  However, a heavy cast iron truing stand as
Wheelsmith had on their logo, is even better if you want to do this
manually.  Holland Mechanics Robot does it better.

Jobst Brandt      <jbrandt@hpl.hp.com>

From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: Very butted spokes
Date: 5 Feb 2000 01:18:22 GMT

Shawn (who?) writes:

> I am planning on building a new set of climbing wheels--and yes
> I have read Jobst's book...I was also thinking of using the
> new (new to me at least) DT 14/17/14 or 15/17/15 spokes.

> 1) They are black!  Look good to me but will I have problems
> similar to hard-anodized rims?

I don't know how DT blackens spokes.  It is not by anodizing but must
be either black paint or blackened chrome, neither of which affect
spoke strength.

> 2) Should I also use these on the rear wheel?  Perhaps, go
> 14/17 on the rear and 15/17 on the front? (2x F&R lacing)

If you have the book, then you know the answer to that one.

> 3) Considering the very thin central section, will torsion
> breaks be a problem while building the wheel--even oiled nipples.

Unless you use your cider press, you will most likely not get the
spokes tight enough.  They are strong enough but only if you can get
them tight.

> I was even considering building some cider-press type apparatus
> to put 200LB pressure on the rim (versus hub axle) at the
> spoke being tightened--take the pressure off the spoke and
> alloy nipple while tightening... does anyone have any experience
> with such a contraption.

That is the only way of tightening spokes on 20 or fewer spoked wheels
adequately.  Rolf furnishes a spoking "box" that supports the rim
while a press pushes on the axle to unload all the spokes on one side
of the wheel.  This is tedious because you have to undo the box to
check alignment and then put it back in the box to make an
adjustment.

Forget about the "cool look" and build some useful wheels and go for a
ride.

Jobst Brandt      <jbrandt@hpl.hp.com>