Spoke Length: Measurement Methology And Criticality?

On Feb 22, 1:33 pm, A Muzi wrote:

Yeah, we knew that already:http://groups.google.com/group/rec.b..._thread/thread...

27 Sep 2002, quite possibly the best r.b.t. post of all time

"(squeeze chicken from bottom to neck several times)"

Per Clive George:
mm, sounds quite likely.

So: what hub

Sturmey X-FDD Dynohub.

what rim?

Ancient and honorable Ayra 26 x 1.75 as supplied with the
original 1982 StumpJumper. I want to stick with it bc it looks
ugly but does the job.

This is my utility/who'd-to-steal-it bike.
http://tinyurl.com/37d4ko

Granted the Dynohub is at odds with that characterization... but
I figure the nastier the rim looks, the more the POS image will
be preserved - especially with sufficient grease/dirt/crud on the
Dynohub.


Are they in the database?

If not, what are their dimensions? Need distance between centre and flange
for both sides (would be the same for a normal front hub),

That's where it gets sticky. Using calipers and a meter stick,
I get an outside flange width of 61 mm and it *seems* tb
symmetrical. http://tinyurl.com/3a9t2z

But when I double check by measuring inside of flange to a metal
strap bolted to the axle, there is a good 2 mm dif between the
two sides: http://tinyurl.com/3e3r8g


diameter of flange.

92 mm outside of spoke-hole-to-outside-of-spoke-hole
http://tinyurl.com/2ofbyz


Number of spokes

36.

Dunno... whatever's safe and does the job.

Consensus is that current lacing is 4x.


ERD of rim.

537 mm inside hole-to-hole, top-of-dimple-to-top-of-dimple.
http://tinyurl.com/36r78k


Is the rim symmetric or offset?

Not sure what that means, but it's a front wheel and the spoke
holes are about 3mm out from the center of the rim:
http://tinyurl.com/22fm3r


My current guesstimate for spoke length is 244 or 246.
--
PeteCresswell

Per A Muzi:
You could just look over at the tattoo of the guy standing next to you:
http://www.yellowjersey.org/photosfr...t/SPOKFORM.JPG

Tattoo? You want to see a tattoo?
http://tinyurl.com/2sp4yb
--
PeteCresswell

Per (PeteCresswell):
(lacing)
Dunno... whatever's safe and does the job.

Consensus is that current lacing is 4x.

OTOH, I observe that on my Rohloff rear wheels, the lacing is
only two across. Justified, IRRC, by the larger flange
diameter. FWIW the Rohloff hub's outside-of-spoke-hole flange
diameter is about 9 mm greater than the Sturmey's.
--
PeteCresswell

"(PeteCresswell)" wrote in message
...
Per Clive George:
mm, sounds quite likely.

So: what hub

Sturmey X-FDD Dynohub.

what rim?

Ancient and honorable Ayra 26 x 1.75 as supplied with the
original 1982 StumpJumper. I want to stick with it bc it looks
ugly but does the job.

This is my utility/who'd-to-steal-it bike.
http://tinyurl.com/37d4ko

Granted the Dynohub is at odds with that characterization... but
I figure the nastier the rim looks, the more the POS image will
be preserved - especially with sufficient grease/dirt/crud on the
Dynohub.


Are they in the database?

If not, what are their dimensions? Need distance between centre and flange
for both sides (would be the same for a normal front hub),

That's where it gets sticky. Using calipers and a meter stick,
I get an outside flange width of 61 mm and it *seems* tb
symmetrical. http://tinyurl.com/3a9t2z

But when I double check by measuring inside of flange to a metal
strap bolted to the axle, there is a good 2 mm dif between the
two sides: http://tinyurl.com/3e3r8g

You need the centre of the flange. So subtract a bit. The 2mm offset makes
sod all difference - put the numbers into the spreadsheet and see.

diameter of flange.

92 mm outside of spoke-hole-to-outside-of-spoke-hole
http://tinyurl.com/2ofbyz

Again, centre of spoke holes, so substract a bit - this one is more
important, though the numbers suggest you can get a surprisingly large
change in diameter at 3/4x. (ok, not that surprising I suppose).

Number of spokes

36.

Dunno... whatever's safe and does the job.

Consensus is that current lacing is 4x.


ERD of rim.

537 mm inside hole-to-hole, top-of-dimple-to-top-of-dimple.
http://tinyurl.com/36r78k

Ok - to quote spocalc, "ERD is measured to the end of the spoke, usually
flush with the head of the nipple". There are quite a few Araya rims in
there with an ERD of 547mm - TBH I'd guess at that being the answer. Your
rim definitely looks bigger than 537mm on that photo.

Is the rim symmetric or offset?

Not sure what that means, but it's a front wheel and the spoke
holes are about 3mm out from the center of the rim:
http://tinyurl.com/22fm3r

Symmetric. There are rims both spoke holes offset to one side, intended to
reduce dish in rear wheels. Hence OSB - which will be zero in your case.

My current guesstimate for spoke length is 244 or 246.

I'm guessing 268 for 4x. Personally I'd use 3x, so 254mm. Spocalc with your
numbers doesn't give 244 or 246 either.

In your situation I'd go through the measurements again. Play with the
flange ones a bit in the spreadsheet to satisfy yourself that they're not
actually that critical, check the ERD, then see what the answer is.

cheers,
clive

Pete Cresswell writes:

Dunno... whatever's safe and does the job.

Consensus is that current lacing is 4x.

OTOH, I observe that on my Rohloff rear wheels, the lacing is only
two across. Justified, IRRC, by the larger flange diameter. FWIW
the Rohloff hub's outside-of-spoke-hole flange diameter is about 9
mm greater than the Sturmey's.

The deciding effect is the angle at which spokes enter the rim. With
large hub flange diameters, fewer crossings should be used to keep
that angle small. If you look at motorcycle wheels, their spokes
emanate from spherical bulges in the rim at fairly large angles from
radial. They being thick and stiff have no options but to go in-line
to the flange from the holes that are drilled by the wheel builder for
custom wheels, that being the cross pattern decider.

Bicycle rims have holes angled left and right but not fore and aft, so
that angle wants to stay near radial to prevent spoke fractures at the
spoke nipple that cannot swivel to larger angles than close to
radial. The Rohloff hub will do well with cross-1 or cross-2.

Jobst Brandt

Per Clive George:
In your situation I'd go through the measurements again. Play with the
flange ones a bit in the spreadsheet to satisfy yourself that they're not
actually that critical, check the ERD, then see what the answer is.

At my current stage of confusion... I think the logical thing to
do is take the hub and rim down to an LBS that I can deal with
and throw myself on their mercy.... -)

I figure somebody who has it down pat can lace and true a wheel
in about 45 minutes. Dunno what that comes to in shop billing
dollars... but I think I'll explore that tomorrow.
--
PeteCresswell

Per A Muzi:
You could just look over at the tattoo of the guy standing next to you:
http://www.yellowjersey.org/photosfr...t/SPOKFORM.JPG

(PeteCresswell) wrote:
Tattoo? You want to see a tattoo?
http://tinyurl.com/2sp4yb

Yes, cute in its own way.
But it doesn't help with the problem at hand, calculate spoke length.
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

well, I guess its ok to ask this now.
JB sez the Rohloff takes a 2 cross lacing. Does that mean the Rohloff
isnot indicated for rough over the road long distance riding?

Gene Daniels writes:

well, I guess its ok to ask this now. JB sez the Rohloff takes a 2
cross lacing. Does that mean the Rohloff isnot indicated for rough
over the road long distance riding?

Huh? What does the cross patten have to do with road surfaces or long
distances? You aren't new to this newsgroup so I wonder why you ask.

Jobst Brandt