From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: alloy vs. brass nipples
Date: 26 Aug 1998 16:29:09 GMT

Martin Trautmann writes:

> I was told that you never should use alloy nipples within alloy rims
> directly ('Kontaktkorrosion' ->
> http://www.uni-stuttgart.de/tandem/Technik/Speichen.html#Speichennippel>
> - otherwise you may have trouble to re-tension the spokes.

Where in that URL is the item on galvanic corrosion?

That is a bunch of theoretical BS (Scheisse)!  The problem is entirely
that Aluminum is weaker than brass.  The wrench flats round off more
easily, the threads strip more easily, and they break more easily when
an object gets between the spokes when riding.  They have been known to
fail in use without abnormal incident.

> While using rims with eyelets, the weight advantage is lost again.

Let's not confuse eyelets and sockets.  Double walled sockets enable
the use of thinner walled hollow section rims.  Sockets with eyelets
have more purpose than to add weight.  A socketed rim can generally
not be used without the steel inserts.  That is to say, eyelets in
the outer wall will not bear the load for any length of time.

> Brass nipples work very well, are strong enough and easy to adjust.
> Their major fault: You don't get them in that many cool colors.

What do colors have to do with a good wheel, or bicycling, for that
matter?

Jobst Brandt      <jbrandt@hpl.hp.com>

From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: alloy vs. brass nipples
Date: 26 Aug 1998 18:41:19 GMT

Martin Trautmann writes:

>>> I was told that you never should use alloy nipples within alloy
>>> rims directly ('Kontaktkorrosion'):

http://www.uni-stuttgart.de/tandem/Technik/Speichen.html#Speichennippel>

>>> otherwise you may have trouble to re-tension the spokes.

>> Where in that URL is the item on galvanic corrosion?

> Just have a look, it reads 'Wenn Alunippel direkt auf der Alufelge
> aufliegen, so kann diese Verbindung unl=F6sbar korrodieren
> (Kontaktkorrosion)'. I suppose you did not check this when you proof
> read it the last time?

I guess my copy/paste of the URL was faulty.  After looking at it, it
strikes me that it makes some far more important points about strength
than corrosion.  Corrosion is not nearly the problem that galling
(fressen) is, when alunimum nipples are used directly on aluminum rims.

- Messing ist das geeignetste Material zur Herstellung von
- Speichennippel. Es erlaubt eine ausreichende Festigkeit, rostet
- nicht und kann in den NippellNchern leicht gedreht werden. Die
- OberflLche wird durch Cadmium- oder Nickelbeschichtung geschOtzt.

The plating mentioned is a cosmetic feature.  I have wheels where
the plating is long gone and all the nipples are dark oxide of
brass.  These work just as well as shiny cadmium or nickel plate.

- Alunippel wiegen nur ein Drittel im Vergleich zu Messingnippeln. Sie
- zeigen jedoch Probleme in der Anwendung, da sie empfindlicher,
- weicher und weniger tragfLhig sind. Wenn Alunippel direkt auf der
- Alufelge aufliegen, so kann diese Verbindung unlNsbar korrodieren
- (Kontaktkorrosion). Alunippel sollten daher nur in wiederum
- schweren, geNsten Felgen und bei geringeren Belastungen eingesetzt
- werden.

The problem is less from corrosion than from destruction of any trace
of lubricant.  The junction between aluminum nipple and rim is
essentially a weldment waiting for energy input.  It isn't seized yet
but as soon as you turn it without lubricant it is.

>> That is a bunch of theoretical BS (Scheisse)!

> Pleased to hear so - but Dave Blake just mentioned that alloy
> nipples were 'frozen in place' by 'environmental exposure'. Is
> galvanic corrosion the same as 'Kontaktkorrosion'?

No.  Having not previously read the description, I assumed that is
what they meant.  I don't know what contact-corrosion is either but I
assume it is capillary moisture intrusion.  In any case, the galling
is a mechanical not a chemical process, although the aluminum oxide in
the contact may have an effect on the oil-water emulsion when wet.

>>> While using rims with eyelets, the weight advantage is lost again.

>> Let's not confuse eyelets and sockets.  Double walled sockets enable
>> the use of thinner walled hollow section rims.  Sockets with eyelets
>> have more purpose than to add weight.  A socketed rim can generally
>> not be used without the steel inserts.  That is to say, eyelets in
>> the outer wall will not bear the load for any length of time.

> Please explain 'socket' to me. What I know is e.g. the Mavic 'X 138
> N', 'X 138 S' or 'T 217'. The 'X 138 N' has no eyelets (440 g), the
> 'X 138 S' is the same one with single/simple eyelets (10 g extra)
> and the 'T 217' is a different type with 'double eyelets'. I suppose
> that double eyeletted hollow section rims could have thinner walls -
> which models are around with comparable strength & side wall
> thickness, one eyeletted, the other one plain?  Are there e.g. any
> comparable models on http://www.rigida.com/anglais/mtb.asp?

Rigida shows only a couple of socketed rims in that section but the
URL seems to be: http://www.rigida.com/anglais/  with the "mtb.asp"
ending on it, it gives an error.

Terminology is especially imprecise in the bicycle industry where fork
offset is often called rake, rake is called head angle, tire casings
are carcasses among a raft of other misnomers.

Rims have eyelets the same as eyelets on shoes or clothing.  Rims can
also have sockets that bridge inner and outer walls of a hollow rim
and are held in place by eyelets.  Fiamme made sockets whose narrow
ends were formed to effect eyelets, thus avoiding an additional part.
Eyelets are generally used to prevent galling of the aluminum rim when
highly loaded nipples are turned, regardless of their material.

Those who are preoccupied with weight can take lubrication measures to
avoid friction problems to a degree, but for general use, steel
eyelets for nipple bearing is preferred.  Eyelets are also not used
for cost reasons ans such low cost wheels are often not highly
tensioned.

> Oh, I thought that's all about it, especially concerning the ultra cool
> colored titanium look.

That IS what it's all about among the tifosi, but then they are they
and not responsible for their behavior.

Jobst Brandt      <jbrandt@hpl.hp.com>

From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: alloy vs. brass nipples
Date: 27 Aug 1998 21:13:33 GMT

Martin Trautmann writes:

>> No.  Having not previously read the description, I assumed that is
>> what they meant.  I don't know what contact-corrosion is either but I
>> assume it is capillary moisture intrusion.  In any case, the galling
>> is a mechanical not a chemical process, although the aluminum oxide in
>> the contact may have an effect on the oil-water emulsion when wet.

> capillary moisture intrusion within the gap of rim and nipple or within
> the material itself?

In a gap is not "in the material" but in a gap between nipple and rim
where moisture and oxygen can intrude.  Metal is not porous so it
cannot get into the metal.  It is a surface effect.

>> Rigida shows only a couple of socketed rims in that section but the
>> URL seems to be: http://www.rigida.com/anglais/  with the "mtb.asp"
>> ending on it, it gives an error.

> Worked for me, but maybe Netscape4.05 is one of the few to accept it.

I meant on the MTB page.  They have others.

> Your link is fined, too. Most of their rims are what I name 'single
> eyeletted' while some are 'double eyeletted' - and I don't know any
> 'double eyeletted' that would not be the socket style.

As I said, terminology in the bicycle industry is notoriously bad,
especially in translations where the original was already incorrect.
There are no double eyelets.  An eyelet is what is used around a canvas
tennis shoe shoelace hole or on canvass sails or bags to guide a line.
"double eyelets" can only be sockets held in by eyelets.

> I suppose that a single eyelet would help to spread some of local
> tension to a bigger area around the nipple hole - thus the center flange
> of a hollow section rim can be built slightly thinner than without an
> eyelet.

The purpose is principally to reduce galling and secondarily to
reinforce the hole.

Jobst Brandt      <jbrandt@hpl.hp.com>