Spoke length calculations

Ok so now that I manage my first wheel build using the spoke lengths that
Andrew sent and now I have been going over spoke calculators. It seems that
they vary in the spoke length to use but normally not by much. My question
is if most you round down, or up? Also just how much of a fudge factor do
you get in the calculations. Most of the manufactures will list or tell you
the ERD but do you need to make you own determination since sometimes I here
differences in the figures. I have the tools and the measuring abilities to
be very precise about getting the proper flange diameter, and figures but
they can differ from what the manufacturer says. My OCD sometimes kicks in
and I think it must be down the the exact amounts.

I keep reading things from Sheldon and other sources but just cannot nail
down anything specific on the usual procedure. Now the questions is by how
much the a spoke elongate or the the rim compress? Is this figured in the
calculations or does the fudge factor make the issue go away. The wheel I
built has 278 mm spokes on the front and 292 on the rear same each side
since it was a offset rim. I took a left over spoke and turned the nipple to
the end of the threads and then measured the distance to the point I ran out
of thread. It seems I have maybe about 2-3 mm of distance and in a a pinch
from the point of contact with the thread to the spoke to the end, no more
adjustment I have 5 mm of distance. My wheel came out great but the Yellow
Jersey made all the calculations and I would have been a bit lost and even
now wonder what I might have used had I made calcs myself.

Finally have you ever built a wheel and had an issue that you ran out of
spoke adjustment or it was too short? Crazy things I need to know and
probably none of it made sense.

Deacon Mark Cleary
Epiphany Church

On Feb 24, 5:01 pm, "Mark Cleary" wrote:
Ok so now that I manage my first wheel build using the spoke lengths that
Andrew sent and now I have been going over spoke calculators. It seems that
they vary in the spoke length to use but normally not by much. My question
is if most you round down, or up? Also just how much of a fudge factor do
you get in the calculations. Most of the manufactures will list or tell you
the ERD but do you need to make you own determination since sometimes I here
differences in the figures. I have the tools and the measuring abilities to
be very precise about getting the proper flange diameter, and figures but
they can differ from what the manufacturer says. My OCD sometimes kicks in
and I think it must be down the the exact amounts.

I keep reading things from Sheldon and other sources but just cannot nail
down anything specific on the usual procedure. Now the questions is by how
much the a spoke elongate or the the rim compress? Is this figured in the
calculations or does the fudge factor make the issue go away. The wheel I
built has 278 mm spokes on the front and 292 on the rear same each side
since it was a offset rim. I took a left over spoke and turned the nipple to
the end of the threads and then measured the distance to the point I ran out
of thread. It seems I have maybe about 2-3 mm of distance and in a a pinch
from the point of contact with the thread to the spoke to the end, no more
adjustment I have 5 mm of distance. My wheel came out great but the Yellow
Jersey made all the calculations and I would have been a bit lost and even
now wonder what I might have used had I made calcs myself.


Not exactly answering your question (better authorities may yet weigh
in), but if you get longer spokes and there's an LBS nearby that can
cut and roll them for you as may be required, that's nice.

snip

Mark Cleary wrote:
Ok so now that I manage my first wheel build using the spoke lengths
that Andrew sent and now I have been going over spoke calculators. It
seems that they vary in the spoke length to use but normally not by
much. My question is if most you round down, or up? Also just how much
of a fudge factor do you get in the calculations. Most of the
manufactures will list or tell you the ERD but do you need to make you
own determination since sometimes I here differences in the figures. I
have the tools and the measuring abilities to be very precise about
getting the proper flange diameter, and figures but they can differ from
what the manufacturer says. My OCD sometimes kicks in and I think it
must be down the the exact amounts.

I keep reading things from Sheldon and other sources but just cannot
nail down anything specific on the usual procedure. Now the questions is
by how much the a spoke elongate or the the rim compress? Is this
figured in the calculations or does the fudge factor make the issue go
away. The wheel I built has 278 mm spokes on the front and 292 on the
rear same each side since it was a offset rim. I took a left over spoke
and turned the nipple to the end of the threads and then measured the
distance to the point I ran out of thread. It seems I have maybe about
2-3 mm of distance and in a a pinch from the point of contact with the
thread to the spoke to the end, no more adjustment I have 5 mm of
distance. My wheel came out great but the Yellow Jersey made all the
calculations and I would have been a bit lost and even now wonder what I
might have used had I made calcs myself.

Finally have you ever built a wheel and had an issue that you ran out of
spoke adjustment or it was too short? Crazy things I need to know and
probably none of it made sense.

If one's building a lot of the same wheel, as we do, I write
it on a grid sheet on my wall. After the first one you know
exactly, that is, you can see if it should have been
slightly longer or shorter. With a change of part
dimensions, I just amend and note the year. A chart's a
handy thing when the parts in question are not here in the
shop.

My younger staff do a calculation each time using a standard
utility into which they have recorded a huge bulk of rims
and hubs. Yes manufacturer spec changes despite catalog or
tech sheet dimensions, some of which have been noted here on
r.b.t. over the years. You can't go wrong with a careful
measurement and the time for that is slight. We enter the
changed new dimension as an entry with the year in that
spreadsheet.

Within a millimeter is great as spokes are commonly
available in 2mm increments. Within 2 is acceptable in most
cases. I generally round down, my employees generally go
long. We would consider end of spoke in the slot of the
nipple as perfect length

If you're off by 4mm, you are just plain wrong. Admit it,
bail out, start over with the correct spokes.

--
Andrew Muzi
www.yellowjersey.org/
Open every day since 1 April, 1971

On Feb 24, 6:01*pm, "Mark Cleary" wrote:
Ok so now that I manage my first wheel build using the spoke lengths that
Andrew sent and now I have been going over spoke calculators. It seems that
they vary in the spoke length to use but normally not by much. My question
is if most you round down, or up?

Round down for several reasons.
1. Spokes may stretch but they will never shrink.
2. Rims may compress but they will never expand.
3. A "too long" spoke may run out of threads and become
"unadjustable.".
4. A "too long" spoke will protrude beyond the nipple and make even
initial tightening with a flat bladed screwdriver difficult, if not
impossible.

Also just how much of a fudge factor do
you get in the calculations. Most of the manufactures will list or tell you
the ERD but do you need to make you own determination since sometimes I here
differences in the figures.

Yup, ERD is a bit of a guesstimate because it "measures" to some
arbitrary point in space. (less arbitrary after the wheel is buiIt and
theres is a spoke end at that point). ERD has, unfortunately, become
the widely accepted standard.
To accommodate your "OCD" side determine the TRUE ERD (for the
pieces you will be using) by measuring the actual inner diameter of
the rim (surface to surface) and then add the ACTUAL depth within the
rim of the nipples (x2) you plan to use. Published ERD figures have
make some assumption (i.e. the type of nipples being used) for this
latter value, although 5mm is usually pretty close.


I have the tools and the measuring abilities to
be very precise about getting the proper flange diameter, and figures but
they can differ from what the manufacturer says. My OCD sometimes kicks in
and I think it must be down the the exact amounts.

Precision won't ever hurt, except when it leads to paralysis.
Do the best you can and assume that unavoidable errors in measurement
will, in the scheme of things, balance out.

I keep reading things from Sheldon and other sources but just cannot nail
down anything specific on the usual procedure. Now the questions is by how
much the a spoke elongate or the the rim compress? Is this figured in the
calculations or does the fudge factor make the issue go away. The wheel I
built has 278 mm spokes on the front and 292 on the rear same each side
since it was a offset rim. I took a left over spoke and turned the nipple to
the end of the threads and then measured the distance to the point I ran out
of thread. It seems I have maybe about 2-3 mm of distance and in a a pinch
from the point of contact with the *thread to the spoke to the end, *no more
adjustment I have 5 mm of distance. My wheel came out great but the Yellow
Jersey made all the calculations and I would have been a bit lost and even
now wonder what I might have used had I made calcs myself.

Finally have you ever built a wheel and had an issue that you ran out of
spoke adjustment or it was too short?

Too long? Yes. Too short? No.

Crazy things I need to know and
probably none of it made sense.

I didn't quite follow the "measured the distance to the point I ran
out
of thread" part but, otherwise, your concerns make perfect sense.

DR

On Feb 24, 7:28*pm, AMuzi wrote:
If one's building a lot of the same wheel, as we do, I write
it on a grid sheet on my wall. After the first one you know
exactly, that is, you can see if it should have been
slightly longer or shorter.

Adjusting by trial and error is cheating. But it is VERY effective.

My younger staff do a calculation each time using a standard
utility into which they have recorded a huge bulk of rims
and hubs. Yes manufacturer spec changes despite catalog or
tech sheet dimensions, some of which have been noted here on
r.b.t. over the years. You can't go wrong with a careful
measurement and the time for that is slight. We enter the
changed new dimension as an entry with the year in that
spreadsheet.

Bottom line - do your own measurements.

Within a millimeter is great as spokes are commonly
available in 2mm increments. Within 2 is acceptable in most
cases. I generally round down, my employees generally go
long. We would consider end of spoke in the slot of the
nipple as perfect length

No argument here. I'm a "round down" guy. End of spoke at bottom of
nipple slot is the (elusive) goal.

If you're off by 4mm, you are just plain wrong. Admit it,
bail out, start over with the correct spokes.

Yes, but take the opportunity to verify WHY you were off by 4
mm. So that you can avoid "trial and error" the next go 'round.
Some of us don't build enough wheels to rely upon "trial and error."
But there's little problem getting it right the first time with
accurate measurements AND accurate calculations.

I should add that rim diameter is the most critical measurement, since
an unlaced rim can easily have significant variations in diameter
measured on different axes.
Measure twice - lace once.

DR

Mark Cleary wrote:
Ok so now that I manage my first wheel build using the spoke lengths that
Andrew sent and now I have been going over spoke calculators. It seems that
they vary in the spoke length to use but normally not by much. My question
is if most you round down, or up? Also just how much of a fudge factor do
you get in the calculations. Most of the manufactures will list or tell you
the ERD but do you need to make you own determination since sometimes I here
differences in the figures.


I would trust Andrew's data.

I like the spoke end to at least reach bottom of the slot in the
nipple, but not protrude beyond the top of the nipple. That gives you
a couple of mm of acceptable range.

The only caveat is with Mavic rims. Mavic creates confusion by using
"Spoke Support Diameter" or "Spoke Bed Diameter" instead of ERD. I
think you have to add 3 mm to their number to obtain ERD.

Art Harris

no one effing listens to me. effing morons. lazy slugs. what the
effing are you here for ? robotic wheel building. effing deleted.
you build a wheel dishing device from a straight 2x4, block up the
dish height, bore a hole for axle or hub roundness, place the rim on
the dishing blocks, hub in nthe hole then tape measure sophe distance.
then you drag your lazy slug ass down to the LBS and buy 8 spokes that
length-2 each quadrent.
and see if this works.

]uneffing believable.

kolldata wrote:
no one effing listens to me. effing morons. lazy slugs. what the
effing are you here for ? robotic wheel building. effing deleted.
you build a wheel dishing device from a straight 2x4, block up the
dish height, bore a hole for axle or hub roundness, place the rim on
the dishing blocks, hub in nthe hole then tape measure sophe distance.
then you drag your lazy slug ass down to the LBS and buy 8 spokes that
length-2 each quadrent.
and see if this works.

]uneffing believable.


How much steel is needed for any given bridge?
1. Build a bridge
2. Run a tape measure over it.

--
Andrew Muzi
www.yellowjersey.org/
Open every day since 1 April, 1971

THAT'S HOW IT STARTS ! before you know it, all the expletive deleted
ferry operators are out of work.
]
no craftsmanship,left. its like GPS. No longer do I have to think
about where the rocks are, GPS tells me where the rocks are, how fast
I'm going, when I will get to rock 3A and can you effing believe it,
if the rock is under water or not and if can clear it with my draft.
JUST LIKE SPOC CALC !!!

takes all the fun out of it.

kolldata wrote:
THAT'S HOW IT STARTS ! before you know it, all the expletive deleted
ferry operators are out of work.
]
no craftsmanship,left. its like GPS. No longer do I have to think
about where the rocks are, GPS tells me where the rocks are, how fast
I'm going, when I will get to rock 3A and can you effing believe it,
if the rock is under water or not and if can clear it with my draft.
JUST LIKE SPOC CALC !!!

takes all the fun out of it.

http://www.dot.wisconsin.gov/travel/water/merrimac.htm

"Note: The Colsac III ferry is closed for the winter season
due to ice on the river. An announcement will be made in the
spring of 2011 when the free ferry service will resume."

We just ride to the nearby Highway 12 bridge when there's no
ferry service. YMMV.

http://mapq.st/fMPxXJ

--
Andrew Muzi
www.yellowjersey.org/
Open every day since 1 April, 1971