What is ERD...really?
John Everett
Following up on a couple of postings from a few weeks ago, I'm about
to order the spokes for my touring bike's wheel rebuild. I used Damon
Rinard's spocalc.xls to figure the lengths.
I used his hub database, but plugged in the ERD from the Alex Rims web
site for the DM18, 606.4mm.
Since I had the rear hub de-spoked I decided to check the database's
measurements and found that the figures given for a Shimano RSX
FH-A410, 7-speed, 130mm, was off by a few mms. The flange offsets were
wrong, but correcting them only resulted (as one would expect) in
fractional mm changes in spoke length.
Since I was in a measuring mood I decided to check the ERD. I referred
to: http://sheldonbrown.com/rinard/spocalc.htm#MeasureHubAndRim for
the methodology and got an ERD of 612mm. I did check rim roundness
(it's round to within a mm) but I was using a wooden yardstick with a
metric scale on one side so accuracy could be compromised. Still, a
six mm error is pretty far out there.
The method Rinard recommends measures ERD to the top of the nipples.
If I measure to the top of the spoke hole grommets I get 607mm, a lot
closer to the Alex web site figure.
So is ERD measured to the top of the nipple or the top of the spoke
grommet? If I'm using spocalc should I add the height of two nipple
heads to 606.4mm to get the correct answer?
BTW, for the hub mentioned above the left flange offset is 32mm and
the right 19mm.
--
jeverett3<AT>sbcglobal<DOT>net (John V. Everett)
datakoll
Jobst Brandt claims ERD is his idea.
The geometric construction gives a theoretic snapshot.
Actual practice requires examination of the spoke/nipple combo in
hand.
RD requires spoke's threading up to nipple top. If the combo doesn't
do that, adjust for reality. A DT 16mm nipple does not thread a DT
spoke to nipple head.
ERD is effective rim DIAMETER not effective rim RADIUS.
See Andrew Muzi's photo in the ERD posts. Muzi goes short 1.5mm from
base nipple screwdriver slot not head. I try for mileage in HD touring
and short 2.5+ accomadating wear and tear.
Best to build a dishing beam of straight grade 1 tuba4, drill a hole/
basin for the hub, shim up to dish at rim's diameter, right side for
rear and run 8 experimental LBS spokes on that platform.
MEASURE REALITY ON THE BEAM
Dan Burkhart
Funny this should come up just a couple of hours after I dealt with
something similar. I was using Rinard's to calculate for Mavic open pro
rims for which Mavic claims a "spoke support diameter" of 602mm.
Rinard's database shows an ERD of 605 with a notation that 3mm have been
added to account for spoke nipple heads. I guess what that means is
Mavic measures differently, not to mention they have a different
terminology.
Dan
--
Dan Burkhart
datakoll
consumer. Right of ask why not announce ERD may be theoretick
according to Brandt then direct an examination of in hand spoke
threading?
Granted, ERD fills the bill for one standard. Without further
direction, ERD is grossly misleading.
To assume ERD is a functional real world spoke measure ask why is
threading wasted into an unthreaded area.
Asking why didn't we see that as the direction to ERD's theoretic
nature is silly oneupmanship practiced by the engine room.
An excuse to beg for one more reorder on top of the returned spokes or
a bad joke when the LBS sez "well, we don't exchange bent used
spokes."
BAH! FUBAR.
(PeteCresswell)
>I used his hub database, but plugged in the ERD from the Alex Rims web
>site for the DM18, 606.4mm.
I just went through that exercise. Successfully - which, given
my aptitude for messing things up, seems like a minor miracle.
I wasn't doing so well until I took my measurements by the
documentation that Damon wrote specifically for SpoCalc.xls.
I can't come up with a URL, but I do have the whole thing
on my hard drive. Let me know if you want me to flip you a .zip
file.
--
PeteCresswell
carl...@comcast.net
wrote:
Dear Pete & John,
Possibly this?
http://www.sheldonbrown.com/rinard/spocalc.htm
http://www.sheldonbrown.com/rinard/spocalc.htm#MeasureHubAndRim
http://www.sheldonbrown.com/rinard/spocalc.htm#Troubleshooting
Cheers,
Carl Fogel
(PeteCresswell)
> http://www.sheldonbrown.com/rinard/spocalc.htm#MeasureHubAndRim
Bingo!
--
PeteCresswell
datakoll
YEAH YEAH YEAH
HERE WE GO AGAIN BINGO
"Most people prefer it near the end of the spoke nipple." SHELDON
BROWN
now, Sheldon knew better than to say something stupid like this so why
did he write it? is the "most people..." an allusion?
I do not know. I empathize with Beam.
if the spoke goes to the end of the spoke nipple, an impossibility
using 16mm DT nipples and DT Champ spokes, wastes male threading where
no female threading exists, doesn't account for wear and tear
then BINGO
DirtRoadie
<jevere...@sbcglobal.DEFEAT.UCE.BOTS.net> wrote:
> So is ERD measured to the top of the nipple or the top of the spoke
> grommet? If I'm using spocalc should I add the height of two nipple
> heads to 606.4mm to get the correct answer?
ERD is the diameter of the circle defined by the spoke ends and takes
into account that a spoke must extend into the rim a bit. It is
slightly larger than the inner diameter of a rim. ERD is not actually
"measured" - it is either an estimate or a calculation. On average
the extra length required is about 5 mm per spoke which increases the
ERD to be about 10 mm more than the measured inner diameter of the
rim. But, if you are so inclined, measure the length of a nipple
then insert the nipple into a spoke hole and measure the lenght of the
external nipple portion (which extends towrad the center of the
wheel). The difference between these two measurements is the lenght of
the nipple withn the rim. That value that is doubled and added the the
actual rim inner diameter to get a figure for ERD. This assumes that
spokes are to be flush with the top of the nipple head.
DR
datakoll
DR>
almost. ERD is an hypotenuse not a diameter. That's why we're
suffering thru the grinding interface of language and math here thru
god software and priests.
try using magic tape for defining threading position inside the
nipple. The threading engagment of spoke and nipple related to actual
effective spoke length (AESL) NOT ERD is the measurement we're after
here.
That's a refinment of what you wrote. right?
"This assumes that spokes are to be flush with the top of the nipple
head."
we should not assume that. NADA!
Ben C
>
> DR>
>
> almost. ERD is an hypotenuse not a diameter. That's why we're
> suffering thru the grinding interface of language and math here thru
> god software and priests.
ERD is a diameter: it's the distance across a circle. The question is
just where is that circle. It is concentric with the rim and about 1.5mm
above where the nipples sit.
datakoll
CHORD is a diameter: it's the distance across a circle.
datakoll
A Muzi
I have, at one time or another, built wheels with spokes sticking out
the end 2~3mm and also 2~3mm short (threads showing above a 12mm
nipple), neither of which proved to be an actual problem over many years
of use.
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971
Tom Sherman
Could gene be using some hubs made from an inferior aluminium alloy that
allows the spoke holes to elongate during use? A proper build will not
allow for effective spoke length increase due to the radius of the spoke
elbow changing. The spokes are certainly not elongating from yield or creep.
--
Tom Sherman - Holstein-Friesland Bovinia
The weather is here, wish you were beautiful
Michael Press
<5b3f748e-f6c8-4fb4...@p73g2000hsd.googlegroups.com>,
DirtRoadie <DirtR...@aol.com> wrote:
> On Mar 8, 11:18 am, John Everett
> <jevere...@sbcglobal.DEFEAT.UCE.BOTS.net> wrote:
>
> > So is ERD measured to the top of the nipple or the top of the spoke
> > grommet? If I'm using spocalc should I add the height of two nipple
> > heads to 606.4mm to get the correct answer?
>
> ERD is the diameter of the circle defined by the spoke ends and takes
> into account that a spoke must extend into the rim a bit. It is
> slightly larger than the inner diameter of a rim. ERD is not actually
> "measured" - it is either an estimate or a calculation.
It is best measured. A URL for a method is posted in this thread.
It really is measured. Put nipples on a some spokes, measure
some distances on the spoke, put two spokes a pair of antipodal
points, measures some more, add and subtract some measurements.
Do it for three pair of diameters on the rim. If your three
measurements do not rectify, draw a picture, think through
the method, and measure some more.
The great problem is that there are different definitions
of ERD. One needs to be absolutely certain of the definition
used in the calculator and of one's measurements.
--
Michael Press
datakoll
MP,
gnaw. you missed the point. Brandt sez ERD is his idea. ERD
establishes ONE MEASUREMENT STANDRAD for one wheel combination, not 4
standradrs for one wheel combination.
BUTBUTBUT ERD is snot AESL. AESL is the small range of engaged
threading used for ordering spokes and building the wheel. AESL=ERD-
SDR (standard deduction range)
ERD is software's spoke calc standard hypotenuse length as a math
constant. (maybe also a disease)
Its snot the length you use to order spokes. its the length you use to
DEDUCT from to order spokes
Yeah. the dishing beam is essential and a basic wheel building tool.
Insert spokes, seat, gives correct dish. A red oak or better beam
should lean in every shop's corner.
DirtRoadie
> > ERD is the diameter of the circle defined by the spoke ends and takes
> > into account that a spoke must extend into the rim a bit. It is
> > slightly larger than the inner diameter of a rim. ERD is not actually
> > "measured" - it is either an estimate or a calculation.
>
> It is best measured. A URL for a method is posted in this thread.
> It really is measured. Put nipples on a some spokes, measure
> some distances on the spoke, put two spokes a pair of antipodal
> points, measures some more, add and subtract some measurements.
> Do it for three pair of diameters on the rim. If your three
> measurements do not rectify, draw a picture, think through
> the method, and measure some more.
You must have a measuring tool that I do not have. I cannot "measure"
ERD on any rim (all being double walled) that I have worked with in
the recent past since the top surface of the nipple heads has always
been recessed below the bed of the rim. That's why I
"calculate" (from some measurements I CAN make) as I described (and
even you describe adding and subtracting some measurements) or
"estimate" it as I also described since many calcualtion have shown
actual rim inner diameter +10 mm to be a usable estimate for
ERD.
> The great problem is that there are different definitions
> of ERD. One needs to be absolutely certain of the definition
> used in the calculator and of one's measurements.
>
True. ERD is really just the innner diameter of the rim with a "fudge
factor" (tied directly to to the configuration of the nipple) factored
in to get us into the ball park. Most nipples are probably similar
enough that a single ballpark "ERD" can be stated by the manufacturer
without creating any significant problems. Years ago I wrote some
software to calculate spoke length taking into account such subtle
factors as the measured and calculated nipple depth within the rim and
hub spoke hole diameter. Such detail is probably overkill, but since
it just applies accurate measurements, it works.
DR
DirtRoadie
> DR>
>
> almost. ERD is an hypotenuse not a diameter.
circle defined by a series of points (spoke ends).
The path of the spoke is irrelevant. The ERD of the rim is the same
regardlees of whether a wheel is radailly or tangentially spoked
(although spoke length will differ).
> The threading engagment of spoke and nipple related to actual
> effective spoke length (AESL) NOT ERD is the measurement we're after
> here.
> That's a refinment of what you wrote. right?
Not reallly. I wasn't really addressing the issue of thread
engagement ( which needs to be "enough" but not "too much")
But yes. The amount of thread engagement does change where the spoke
ends and the resulting "ERD."
> "This assumes that spokes are to be flush with the top of the nipple
> head."
>
> we should not assume that. NADA!
I was merely describing the underlying assumption of what I was
describing , not "how it should be." Personally I think the ideal
threading for both functionallity and aesthetics would be to have the
spoke end flush with the bottom of the slot in the nipple head. YMMV.
DR
carl...@comcast.net
<DirtR...@aol.com> wrote:
>You must have a measuring tool that I do not have. I cannot "measure"
>ERD on any rim (all being double walled) that I have worked with in
>the recent past since the top surface of the nipple heads has always
>been recessed below the bed of the rim. That's why I
>"calculate" (from some measurements I CAN make) as I described (and
>even you describe adding and subtracting some measurements) or
>"estimate" it as I also described since many calcualtion have shown
>actual rim inner diameter +10 mm to be a usable estimate for
>ERD.
Dear DR,
I may be misunderstanding you, but have a look at this page:
http://www.sheldonbrown.com/rinard/spocalc.htm#MeasureHubAndRim
Page down once to the diagram of the double-walled rims, and it shows
how to measure the ERD from the top of one spoke nipple inside a
double-walled rim to the other.
Cheers,
Carl Fogel
datakoll
Hi Carl, how was the trip to Goodyear?
measuring for double walls takes NIQ+10 where we arrive at 0
insert spoke into rim, magic tape insertion at rim inside entry hole
for nipple head reach, then for slot base reach, then for 1.5mm short
of slot base reach.
OR tape spoke shaft when spoke reachs inside rim eyelet (the grommet
reinforcement)
WRITE THE NUMBERS DOWN WITH ASSCOCIATED DIAGRAM IN YOUR LOG BOOK.
then insert spoke into nipple to threading: tape insertion on spoke.
measure the short end.
then thread spoke onto nipple until spoke arrives at slot base. tape
spoke shaft and measure short end.
WRITE THE NUMBERS DOWN IN YOUR LOG BOOK.
you now have a spoke length table. Use the table for tilting at ERD.
841
ERD is snot spoke length, spoke length is AESL. Rinard and Brandt,
obviously highly intelligent people continue chanting ERD like mary
had a little lamb is spoke length until people of normal intelligence
believe that, to their error and consternation.
Clearing the problem off the boards using magic tape and AESL is
similar to Gates' ascesnion to world's second richest man, having
soooooo much money he gave it to Africans soooo we can have more
Africans.
John Everett
wrote:
As usual Gene is the master of obfuscation. However in this case he's
also wrong on a couple of counts.
He says, "To assume ERD is a functional real world spoke measure"; yet
I don't believe anyone assumes this. ERD is a rim measurement.
Also, he writes about "threading wasted into an unthreaded area". By
this I'm guessing he means the screwdriver slot. I just threaded one
of the spokes I removed from the referenced rear wheel (see OP) and
threaded it backward into one of the nipples. At the point where I
can't pull the nipple from the spoke if I hold the assembly up to a
light I can see light passing through the slot, between the base of
the slot and the end of the spoke. Thus (at least in this case) the
slot is threaded.
But to get back to my original question, should I add twice the height
of one nipple head to Alex's 606.4mm to calculate spoke lengths?
DirtRoadie
> On Sun, 9 Mar 2008 21:32:06 -0700 (PDT), DirtRoadie
>
> >You must have a measuring tool that I do not have. I cannot "measure"
> Dear DR,
>
> I may be misunderstanding you,
Yes, I believe so. But it is largely a matter of semantics.
> but have a look at this page:
> http://www.sheldonbrown.com/rinard/spocalc.htm#MeasureHubAndRim
>
> Page down once to the diagram of the double-walled rims, and it shows
> how to measure the ERD from the top of one spoke nipple inside a
> double-walled rim to the other.
No, it shows how to *calculate* ERD by taking some other measurements
AND doing some calculations - "ERD = A + 2B."
While it would be simple enough to design a tool to simply *measure*
ERD in one single step (perhaps Fogel Labs would like to take on this
project), I have no such tool and must rely on calculating ERD based
upon the formula shown. That was my point.
DR
jobst....@stanfordalumni.org
Wheel" along with equations for calculating spoke length in the
section called "Equations". Those equations were subsequently used by
various people who have web sites that enable users to enter wheel
dimensions to arrive at spoke lengths. The definition is also given
in that section of the book. Those definitions have been distorted in
spite of the text that I believe is unambiguous.
Jobst Brandt
datakoll
divinity deleted. off course ERD is measurabbble in a rim. what is
this, CERN?
build the beam with dishing spacers, place hub into depression or axle
hole, rim on dish spoacers and measure with a stiff wire, mark with
tape.
in depth knowledge of why the MO spokes I receive are in incorrect
lengths comes from these here posts believe you me.
Michael Press
<5d92b46d-eabc-4d41...@p73g2000hsd.googlegroups.com>,
DirtRoadie <DirtR...@aol.com> wrote:
> On Mar 9, 3:27 pm, Michael Press <rub...@pacbell.net> wrote:
> > > ERD is the diameter of the circle defined by the spoke ends and takes
> > > into account that a spoke must extend into the rim a bit. It is
> > > slightly larger than the inner diameter of a rim. ERD is not actually
> > > "measured" - it is either an estimate or a calculation.
> >
> > It is best measured. A URL for a method is posted in this thread.
> > It really is measured. Put nipples on a some spokes, measure
> > some distances on the spoke, put two spokes a pair of antipodal
> > points, measures some more, add and subtract some measurements.
> > Do it for three pair of diameters on the rim. If your three
> > measurements do not rectify, draw a picture, think through
> > the method, and measure some more.
>
> You must have a measuring tool that I do not have. I cannot "measure"
> ERD on any rim (all being double walled) that I have worked with in
> the recent past since the top surface of the nipple heads has always
> been recessed below the bed of the rim. That's why I
> "calculate" (from some measurements I CAN make) as I described (and
> even you describe adding and subtracting some measurements) or
> "estimate" it as I also described since many calcualtion have shown
> actual rim inner diameter +10 mm to be a usable estimate for
> ERD.
We seem to agree. Measure, then calculate.
The calculation is rather less of a factor
than a measurement and calculation based on theory
such as the yield strength of a quick release skewer
from its dimensions and composition.
--
Michael Press
DirtRoadie
Jobst -
I won't dispute your introduction of the term "ERD" although I have
never liked the concept since it relies on assumptions regarding
nipple measurements that may or may not be true. But as to the easily
derived equations, gim'me a break. I suppose that (along with the
wheel itself) you invented the underlying trigonometry too?
DR
datakoll
DR,
Discussion or ERD crossed the threshold of cycle mechanics into the
realm of Glabl Warming. Given a simple concept meant to simplify a
simple measure and build operation, participants wandered off into a
quagmire of illusion, ill defined concepts, misunderstandings, sheer
mind numbing blockheadedness and stupidity.
Your comment is no different: "relies on assumptions regarding
nipple measurements that may or may not be true."
Unbelievable. You cannot read a soup can label ?
Tom Sherman
wheel. Before Jobst, all wheels were hand carved from granite. ;)
datakoll
A carefully crafted and crafty paragraph this, a revision exonerating
Brandt's egotistical criminal act of misdefinition.
"Subsequently used" - various demons wrenched poor Brandt's concept
from it's bed. raping it on the altar of self serving websites.
Yet while permanently defiled by the unworthy, the Brandt ERD concept
carried on in pristine mathematicall glory and insight "enabling
users." to follow the path lit by Brandt's brilliant trigonometry
"to arrive at" the holy city: UPSville, Returnlabel.
Having shed his guilt to others, Brandt then restates his guilt.
Incroyable !
The witless "users" arrived at "spoke lengths."
EAT BEFORE JULY 2014. USE AS DIRECTED. ASSEMBLE IN REVERSE ORDER.
SPOKE LENGTHS? Jobst, what kind of SPOKE LENGTHS?
ERD spoke lengths or spoke lengths that build the wheel AESL spoke
lengths?
Sacre Blue.
jim beam
> On Mar 10, 5:54�pm, jobst.bra...@stanfordalumni.org wrote:
>> The term "Effective Rim Diameter" ERD was introduced in "the Bicycle
>> Wheel" along with equations for calculating spoke length in the
>> section called "Equations". �Those equations were subsequently used by
>> various people who have web sites that enable users to enter wheel
>> dimensions to arrive at spoke lengths. �The definition is also given
>> in that section of the book. �Those definitions have been distorted in
>> spite of the text that I believe is unambiguous.
>>
>> Jobst Brandt
>
> A carefully crafted and crafty paragraph this,
no shit. to spell it out, "introduction" carefully /implies/ invention
while walking the fine line of truthfulness by not quite /actually/
doing so.
> a revision exonerating
> Brandt's egotistical criminal act of misdefinition.
> "Subsequently used" - various demons wrenched poor Brandt's concept
> from it's bed. raping it on the altar of self serving websites.
> Yet while permanently defiled by the unworthy, the Brandt ERD concept
> carried on in pristine mathematicall glory and insight "enabling
> users." to follow the path lit by Brandt's brilliant trigonometry
> "to arrive at" the holy city: UPSville, Returnlabel.
>
> Having shed his guilt to others, Brandt then restates his guilt.
> Incroyable !
indeed. but baron münchhausen is never short on ability to entertain -
you have to give him that.