Measuring tension on short DB spokes?

"(Pete Cresswell)" <[email hidden]> wrote in message "]news:[email hidden]...

Quoted message said:

The WheelSmith tensiometer I got last week seems to work OK, but the instructions say it has to be
applied away from the butted area.

Only problem is that on my rear wheels the hub is so big that there's not

enough

Quoted message said:

space between the non-butted area and where the spokes cross to fit the instrument.

I'm guessing the conversion factor just changes to something between the

narrow

Quoted message said:

diameter and the butted diameter. Does anybody have a fudge factor for

this

Quoted message said:

situation?
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PeteCresswell

I would suggest you forget accuracy and go for repeatability by measuring each spoke in the same
way. High even tension is what you are after. While having the foot of the gauge on the thicker part
of the spoke will throw the reading off, at least measuring all the spokes the same way should give
similar readings if their tension is the same.

Mike

Michael Dart said:

Quoted message said:

The Wheelsmith tensiometer I got last week seems to work OK, but the instructions say it has to
be applied away from the butted area.

Quoted message said:

Quoted message said:

Only problem is that on my rear wheels the hub is so big that there's not enough space between
the non-butted area and where the spokes cross to fit the instrument.

Quoted message said:

Quoted message said:

I'm guessing the conversion factor just changes to something between the narrow diameter and the
butted diameter. Does anybody have a fudge factor for this situation?

Since there is no in-situ zero on this instrument, you cannot determine what the tension is over two
spoke thicknesses, the thickness differences being larger than the measurement of interest. This was
an obvious problem when I designed the instrument shown in "the Bicycle Wheel" that does this for
every measurement.

Quoted message said:

I would suggest you forget accuracy and go for repeatability by measuring each spoke in the same
way. High even tension is what you are after. While having the foot of the gauge on the thicker
part of the spoke will throw the reading off, at least measuring all the spokes the same way
should give similar readings if their tension is the same.

That's not a good idea because it serves no purpose except to make wheel truing and tensioning
extremely tedious. Since equalizing tension is a repetitive and individual process, it should go
rapidly with quick feedback after adjustments. That is why this is done by the tone of plucked
spokes for all but the seriously tone deaf, who are at a great disadvantage in this business. I
wouldn't wish that hurdle on people who want to build wheels.

Jobst Brandt [email hidden]

RE/

Quoted message said:

That's not a good idea because it serves no purpose except to make wheel truing and tensioning
extremely tedious. Since equalizing tension is a repetitive and individual process, it should go
rapidly with quick feedback after adjustments. That is why this is done by the tone of plucked
spokes for all but the seriously tone deaf, who are at a great disadvantage in this business. I
wouldn't wish that hurdle on people who want to build wheels.

I'm among the seriously tone-deaf.

But actually, when I did a wheel from scratch (i.e. backed all the nipples off until the spoke was
even with the top of the nipple) then tightened each spoke an exact number of turns, dished the
wheel the same way, and then trued it; the tensions came out within 5 kg of each other.

Seems to me like my main use of the tensiometer is to keep me from exceeding the rim manufacturer's
spec and, when trying to true a wheel, to spot grossly out-of tension spokes.
-----------------------
PeteCresswell

Pete Cresswell said:

Quoted message said:

That's not a good idea because it serves no purpose except to make wheel truing and tensioning
extremely tedious. Since equalizing tension is a repetitive and individual process, it should go
rapidly with quick feedback after adjustments. That is why this is done by the tone of plucked
spokes for all but the seriously tone deaf, who are at a great disadvantage in this business. I
wouldn't wish that hurdle on people who want to build wheels.

Quoted message said:

I'm among the seriously tone-deaf.

Quoted message said:

But actually, when I did a wheel from scratch (i.e. backed all the nipples off until the spoke was
even with the top of the nipple) then tightened each spoke an exact number of turns, dished the
wheel the same way, and then trued it; the tensions came out within 5 kg of each other.

Quoted message said:

Seems to me like my main use of the tensiometer is to keep me from exceeding the rim
manufacturer's spec and, when trying to true a wheel, to spot grossly out-of tension spokes.

I hadn't seen any tension specifications given by rim manufacturers. Which rims have such
information?

Jobst Brandt [email hidden]

RE/

Quoted message said:

I hadn't seen any tension specifications given by rim manufacturers. Which rims have such
information?

Mavic gives a figure of, in their words, "90-110 daN" - which I take to be about 100kg.

So I just check my wheels for tensions excess of that.

Interestingly, the wheel I did myself came out with the spokes within 5 kg of each other while the
wheel I just picked up from the "professional wheelbuilder" (who said he had a "$300
tensiometer"...but didn't name the brand) had spoke tensions all over the place....so much variation
that I'm already getting the urge to unscrew all the nipples and start over....but the problem is
that wheel has DB spokes and my dinky little WheelSmith can't give an explicit reading because the
distance is too short between the end of the butts and the crossover. OTOH, I could probably average
the readings of the newly-built wheel and call that "100 kg"....

I've got a PDF that came from Mavic, but don't know the URL. I'll mail you a copy of the .PDF
if you want.
-----------------------
PeteCresswell

Pete Cresswell said:

Quoted message said:

I hadn't seen any tension specifications given by rim manufacturers. Which rims have such
information?

Quoted message said:

Mavic gives a figure of, in their words, "90-110 daN" - which I take to be about 100kg.

Quoted message said:

So I just check my wheels for tensions excess of that.

Quoted message said:

Interestingly, the wheel I did myself came out with the spokes within 5 kg of each other while the
wheel I just picked up from the "professional wheelbuilder" (who said he had a "$300
tensiometer"... but didn't name the brand) had spoke tensions all over the place... so much
variation that I'm already getting the urge to unscrew all the nipples and start over... but the
problem is that wheel has DB spokes and my dinky little WheelSmith can't give an explicit reading
because the distance is too short between the end of the butts and the crossover. OTOH, I could
probably average the readings of the newly-built wheel and call that "100 kg"...

Quoted message said:

I've got a PDF that came from Mavic, but don't know the URL. I'll mail you a copy of the .PDF if
you want.

That might be interesting. Sure, send me a copy.

Jobst Brandt [email hidden]