Hub dynamo wheelbuild - spoke length

Alan Braggins said:

I'm using http://www.dtswiss.com/spokescalc/Calculator.aspx to plan
buying some spokes to rebuild my existing rim with a hub dynamo.
Any advice on measuring "Diameter / ERD" for a user defined rim?
Am I right in thinking it's the diameter of the circle where I want
the ends of the spokes to end up, so the inside diameter of the rim?

I find Spocalc better than the DT one and it has far more rims and
details in it as standard. You can also download it and run it from
your PC without being online.
http://www.damonrinard.com/spocalc.htm

--
Tony

"I did make a mistake once - I thought I'd made a mistake but I hadn't"
Anon

"Alan Braggins" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

I'm using http://www.dtswiss.com/spokescalc/Calculator.aspx to plan
buying some spokes to rebuild my existing rim with a hub dynamo.
Any advice on measuring "Diameter / ERD" for a user defined rim?
Am I right in thinking it's the diameter of the circle where I want
the ends of the spokes to end up, so the inside diameter of the rim?

Use spocalc.xls instead (on sheldon's site). It's got a database of all
these things already in it, so you don't need to look them up.

(However I think your answer is probably yes).

Dunno how rich you're feeling, but if you're spending 40 quid on a hub, 10
on spokes, I reckon you may as well spring for the extra 15-20 quid for the
rim and have an entire spare wheel.

(hmm, ok, I didn't do that for the tandem - but those rims are a bit harder
to find)

cheers,
clive

Alan Braggins said:

I'm using http://www.dtswiss.com/spokescalc/Calculator.aspx to plan
buying some spokes to rebuild my existing rim with a hub dynamo.
Any advice on measuring "Diameter / ERD" for a user defined rim?
Am I right in thinking it's the diameter of the circle where I want
the ends of the spokes to end up, so the inside diameter of the rim?

It's easy.

Take two nipples. Insert them into rim holes that are exactly opposite
each other (count to be sure). Now either hold them in with sellotape
or have someone else press them in, while you measure the distance
between the free ends with a rule or tape measure. Write the distance
down. Do it twice more at different locations in case the rim is
slightly eccentric. Now average the three figures and subtract the full
length of the two nipples. That is your ERD.

It sounds complicated but only takes 2 minutes. Don't use the inside
diameter of the rim - this is far too small, especially for a double
socketed rim.

In message <[email hidden]>

Clive George said:

"Alan Braggins" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

I'm using http://www.dtswiss.com/spokescalc/Calculator.aspx to plan
buying some spokes to rebuild my existing rim with a hub dynamo.
Any advice on measuring "Diameter / ERD" for a user defined rim?
Am I right in thinking it's the diameter of the circle where I want
the ends of the spokes to end up, so the inside diameter of the rim?

Use spocalc.xls instead (on sheldon's site). It's got a database of all
these things already in it, so you don't need to look them up.

(However I think your answer is probably yes).

Dunno how rich you're feeling, but if you're spending 40 quid on a hub, 10
on spokes, I reckon you may as well spring for the extra 15-20 quid for the
rim and have an entire spare wheel.

Thats exactly what I did. I even keep my spare tyre on it, fully inflated
in case I find I have a puncture when I am about to leave for work.

--
Typed by monkey #27662472869676 on typewriter #7552416572242
When emailing me, please include the word Banana in the subject line.

Zog The Undeniable said:

Now average the three figures and subtract the full
length of the two nipples. That is your ERD.

ITYM add the full length

--
Tony

"I did make a mistake once - I thought I'd made a mistake but I hadn't"
Anon

Zog The Undeniable said:

Alan Braggins said:

I'm using http://www.dtswiss.com/spokescalc/Calculator.aspx to plan
buying some spokes to rebuild my existing rim with a hub dynamo.
Any advice on measuring "Diameter / ERD" for a user defined rim?
Am I right in thinking it's the diameter of the circle where I want
the ends of the spokes to end up, so the inside diameter of the rim?

It's easy.

Take two nipples. Insert them into rim holes that are exactly opposite
each other (count to be sure). Now either hold them in with sellotape
or have someone else press them in, while you measure the distance
between the free ends with a rule or tape measure. Write the distance
down. Do it twice more at different locations in case the rim is
slightly eccentric. Now average the three figures and subtract the full
length of the two nipples. That is your ERD.

It sounds complicated but only takes 2 minutes. Don't use the inside
diameter of the rim - this is far too small, especially for a double
socketed rim.

Or alternatively, what I do is measure the diameter of the rim, from
outer edge to outer edge [call that measurement A], then put just one
nipple into a hole and measure the distance from the screw head end of
the nipple to the outer edge of the rim [measurement B].
Your ERD is A - (B + B]

Garry

Alan Braggins said:

I'm using http://www.dtswiss.com/spokescalc/Calculator.aspx to plan
buying some spokes to rebuild my existing rim with a hub dynamo.

Your ERD question has been answered by others, but perhaps you'll be
interested in my recent experience building a wheel. I built my first
wheel a week ago, with a dynamo hub (Shimano 3N70) and a Mavic A319 rim.
I used three spoke length calculators:
http://www.wheelpro.co.uk/spokecalc/
http://www.tech-mavic.com/uk/calcul.htm
http://www.damonrinard.com/spocalc.htm

These calculators gave various spoke lengths in the range 286-287mm.
After building the wheel with 287mm Sapim Race (butted) spokes I was
surprised to find the ends of the spokes protruded by 3mm from the
nipples. I've still not worked out what I measured wrongly, but I'm
hoping that the thread engagement will still be sufficient. I'll be
trying out the wheel tomorrow. If anyone who is experienced in these
matters believes I should rebuild the wheel with shorter spokes, please
tell me!

Bob

"Bob Johnstone" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Alan Braggins said:

I'm using http://www.dtswiss.com/spokescalc/Calculator.aspx to plan
buying some spokes to rebuild my existing rim with a hub dynamo.

Your ERD question has been answered by others, but perhaps you'll be
interested in my recent experience building a wheel. I built my first
wheel a week ago, with a dynamo hub (Shimano 3N70) and a Mavic A319 rim. I
used three spoke length calculators:
http://www.wheelpro.co.uk/spokecalc/
http://www.tech-mavic.com/uk/calcul.htm
http://www.damonrinard.com/spocalc.htm

These calculators gave various spoke lengths in the range 286-287mm. After
building the wheel with 287mm Sapim Race (butted) spokes I was surprised
to find the ends of the spokes protruded by 3mm from the nipples. I've
still not worked out what I measured wrongly, but I'm hoping that the
thread engagement will still be sufficient. I'll be trying out the wheel
tomorrow. If anyone who is experienced in these matters believes I should
rebuild the wheel with shorter spokes, please tell me!

My copy of spocalc has two versions of the A319 - one with 604.5 ERD and one
with 602.5 ERD - the latter is marked as 'A 319 D 05' so might be a newer
version. This could be some of the difference.

cheers,
clive

Clive George said:

My copy of spocalc has two versions of the A319 - one with 604.5 ERD and one
with 602.5 ERD - the latter is marked as 'A 319 D 05' so might be a newer
version. This could be some of the difference.

Aha! That'll be the problem (sort of). I was actually using an ERD of
607mm, which the DT Swiss spoke calculator
(http://www.dtswiss.ch/spokescalc/Calculator.aspx) assured me was
correct for the Mavic A319 rim. That'll teach me to trust someone else's
measurement.

Bob

Tony Raven said:

Zog The Undeniable said:

Now average the three figures and subtract the full length of the two
nipples. That is your ERD.

ITYM add the full length

Bugger! You're right.

Clive George said:

"Alan Braggins" <[email hidden]> wrote in message

Quoted message said:

I'm using http://www.dtswiss.com/spokescalc/Calculator.aspx to plan
buying some spokes to rebuild my existing rim with a hub dynamo.
Any advice on measuring "Diameter / ERD" for a user defined rim?
Am I right in thinking it's the diameter of the circle where I want
the ends of the spokes to end up, so the inside diameter of the rim?

Use spocalc.xls instead (on sheldon's site). It's got a database of all
these things already in it, so you don't need to look them up.

I wasn't going to bother installing Office (or OpenOffice) on this machine
until I'd got round to buying a bigger disk, but I'll have a look on
the other machine.

Quoted message said:

(However I think your answer is probably yes).

Dunno how rich you're feeling, but if you're spending 40 quid on a hub, 10
on spokes, I reckon you may as well spring for the extra 15-20 quid for the
rim and have an entire spare wheel.

I thought about that, but I have a spare rim lying around anyway, and a new
one puts the shipping into the "bulky items" category.

Quoted message said:

(hmm, ok, I didn't do that for the tandem - but those rims are a bit harder
to find)

cheers,
clive

In article 435a841c.0@entanet said:

Alan Braggins said:

I'm using http://www.dtswiss.com/spokescalc/Calculator.aspx to plan
buying some spokes to rebuild my existing rim with a hub dynamo.
Any advice on measuring "Diameter / ERD" for a user defined rim?
Am I right in thinking it's the diameter of the circle where I want
the ends of the spokes to end up, so the inside diameter of the rim?

It's easy.

Take two nipples. Insert them into rim holes that are exactly opposite
each other (count to be sure). Now either hold them in with sellotape
or have someone else press them in, while you measure the distance
between the free ends with a rule or tape measure. Write the distance
down. Do it twice more at different locations in case the rim is
slightly eccentric. Now average the three figures and subtract the full
length of the two nipples. That is your ERD.

I hadn't thought of unlacing the existing wheel before ordering the bits,
but that will be more accurate. (I was going to use a wheel from another
bike while rebuilding anyway.)

I'm off to North Wales for half term now, thanks to everybody for the advice.

Response to Alan Braggins:

Quoted message said:

I wasn't going to bother installing Office (or OpenOffice) on this machine
until I'd got round to buying a bigger disk

I noticed not long ago that at 193 mb, my OpenOffice installation is
bigger than the hard drive was on my first Windows machine.

--
Mark, UK

"There are some things only intellectuals are crazy enough to believe."

Alan Braggins said:

I hadn't thought of unlacing the existing wheel before ordering the bits,
but that will be more accurate. (I was going to use a wheel from another
bike while rebuilding anyway.)

I'm off to North Wales for half term now, thanks to everybody for the advice.

Just add the length of the nipples, not subtract - I was having a brain
fart! I do it this way and it works.

Mark McNeill said:

Response to Alan Braggins:

Quoted message said:

I wasn't going to bother installing Office (or OpenOffice) on this machine
until I'd got round to buying a bigger disk

I noticed not long ago that at 193 mb, my OpenOffice installation is
bigger than the hard drive was on my first Windows machine.

The modern version of Parkinson's Law - "data expands to fill the
storage available"

--
Tony

"I did make a mistake once - I thought I'd made a mistake but I hadn't"
Anon

Bob Johnstone said:

Clive George said:

My copy of spocalc has two versions of the A319 - one with 604.5 ERD
and one with 602.5 ERD - the latter is marked as 'A 319 D 05' so
might be a newer version. This could be some of the difference.

Aha! That'll be the problem (sort of). I was actually using an ERD of
607mm, which the DT Swiss spoke calculator
(http://www.dtswiss.ch/spokescalc/Calculator.aspx) assured me was
correct for the Mavic A319 rim. That'll teach me to trust someone
else's measurement.

"D" stands for disc brake. To confuse the issue with a third number, the
Mavic tech site says 600mm for the standard version:

www.tech-mavic.com/uk/sources/Produits/Trekking/A319_05/Features.pdf
(Name "mavic-com", pw "dealer"😉

Too-long spokes shouldn't be a problem as long as you haven't run out of
thread and can prevent punctures to rim tape and inner tube.

One of my wheels has just a few of the spokes too long (dealer incorrectly
supplying mixed lengths!). I made grommets from sliced presta dust caps
(which happen to fit Open Pro rims perfectly). Some of the other spokes
were too short!, helped by using longer DT nipples as they have a little
more thread. What a mess, but it's done a few thousand miles so far with
no complaints.

Lesson learnt: Check length of all spokes before lacing wheel.

~PB

I scribbled:

Quoted message said:

One of my wheels has just a few of the spokes too long (dealer
incorrectly supplying mixed lengths!)

ps. I wasn't mixing up rear left & right spokes :-)

~PB

Pete Biggs said:

Bob Johnstone said:

Clive George said:

My copy of spocalc has two versions of the A319 - one with 604.5 ERD
and one with 602.5 ERD - the latter is marked as 'A 319 D 05' so
might be a newer version. This could be some of the difference.

Aha! That'll be the problem (sort of). I was actually using an ERD of
607mm, which the DT Swiss spoke calculator
(http://www.dtswiss.ch/spokescalc/Calculator.aspx) assured me was
correct for the Mavic A319 rim. That'll teach me to trust someone
else's measurement.

"D" stands for disc brake. To confuse the issue with a third number, the
Mavic tech site says 600mm for the standard version:

www.tech-mavic.com/uk/sources/Produits/Trekking/A319_05/Features.pdf
(Name "mavic-com", pw "dealer"😉

Too-long spokes shouldn't be a problem as long as you haven't run out of
thread and can prevent punctures to rim tape and inner tube.

One of my wheels has just a few of the spokes too long (dealer incorrectly
supplying mixed lengths!). I made grommets from sliced presta dust caps
(which happen to fit Open Pro rims perfectly). Some of the other spokes
were too short!, helped by using longer DT nipples as they have a little
more thread. What a mess, but it's done a few thousand miles so far with
no complaints.

Lesson learnt: Check length of all spokes before lacing wheel.

If the spokes were within a 2mm range, there was no mix up. I like to
sort spokes for each side of a wheel by length before I build a wheel,
and I use the shorter ones for the inside[1]. It probably doesn't
achieve much other than I will get to spot if any spokes really are a
long way out of spec before I spend a somewhat longer amount of time
building the wheel. It does seem to help with getting all the spokes to
appear at about the same depth in the threads when I'm using all new
components. There is a scenario where you can end up building a wheel
where half the spokes look too long and half too short, even with all
the spokes being identical lengths. Thats just a mistake, though.

[1]Cue someone who uses the short ones on the outside...
JimP

Mark McNeill said:

I noticed not long ago that at 193 mb, my OpenOffice installation is
bigger than the hard drive was on my first Windows machine.

Our first family PC was a 286. It came in a case which would be a little
on the large size for a modern server and had two (Count them) 21MB hard
drives. Over time, one of them developed an issue that meant it
sometimes couldn't start up the motor. Not a problem; these had an
external spindle. Just flick it with a screw and, hey presto, jump started!

Those were the days...

Jon