Newsgroups: rec.bicycles.tech

Subject: Re: Chain Maintenance Question

Bernd Kischnick writes:

> I don't know about those pins. Anyway, we cannot argue about
> facts.  the holes are slightly egg-shaped or they are not. Put a
> side plate under your Tastschnittgeraet and check it, if you don't
> believe it. As the holes are not drilled into the plates, it is
> not to change their shape.

After Bernd sent me some more assurances, I got myself some pieces
of chain to measure and inspect.  Bernd's claims are essentially
correct about the odd shaped holes however the pitch discussion was
apparently more a matter of semantics than dimensional.  Here is
what I found.

For those not familiar with the Rohloff chain, it has the same
construction as the Sedis Sport chain with the difference that the
pins do not protrude as far as on the Sedis chain.

I measured the Rohloff and the Sedis and found that Rohloff went a
step further than Sedis but may be spinning its wheels in the sand.
First I should point out that the outer plates into which the pins
are pressed are spaced less than 1/2 inch to make up for the
clearance in the "sleeves", that on the Sedis (and I assume on other
chains) are spaced 1/2 inch apart.  The Rohloff spaces these 0.5015
inches apart for reasons that I do not understand.  In any event,
the following table shows some of the comparable dimensions.

                            Sedis             Rohloff
                        -------------      -------------
                         mm     inch        mm     inch
pin length              7.35    0.289      6.90    0.272
pin diameter            3.65    0.1437     3.625   0.1427
bearing hole            3.70    0.1456     3.775   0.1486
over outer plates       6.50    0.256      6.50    0.256
chain height            8.20    0.323      9.10    0.358
outer plate thickness   1.15    0.0453     1.00    0.0394
inner plate thickness   1.20    0.0472     1.00    0.0394
outer plate centers     0.500   0.0197     0.5015  0.0197
inner plate centers    12.624   0.497     12.497   0.492
roller OD               7.65    0.301      7.75    0.305
roller ID               5.334   0.2100     5.385   0.2120
roller width            2.184   0.0860     2.095   0.0825

As Bernd claimed, the pin bearing holes are "egg shaped" in that
they have a pin fitting radius toward the end of the plate and a
clearance hole radius on the inward side, both radii lying within
the circle of the larger radius.  That is, the hole is not elongated
but has its sides pulled in to give a smaller radius for the pin
bearing region.

Among the detail that I noticed was that Rohloff pins have a visibly
rougher surface finish than other chains but in contrast has a
smoother and more cylindrical bearing surface for the rollers
provided by the formed side plates that even have an undercut to
avoid the radius found in the Sedis chain.  The riveted ends of the
Rohloff tend to crack when pressed out making reassembly possibly
less reliable.  The Sedis chain has its inner plates flared to make
sprocket tooth engagement, a feature that would be even more
appropriate for the Rohloff, it being even narrower than the Sedis.

Wear and shifting ease are two principal concerns of a derailleur
chain and I am not ready to make any claims that one of these is
better in either department.  I have had excellent success with the
no longer available Regina CX-S that was exorbitantly expensive but
had features that gave it an advantage in both departments.

I was glad that Bernd convinced me to look and that there is still
advancement in chains and that the dimensions and configuration is
as deeply thought out as I found.  I am sure there are more aspects
that are even less obvious.  Maybe Rohloff can include cut out side
plates similar to those on the Regina asymmetric chain that shifted
so well that without indexed shifting it could silently creep over
to the next sprocket without complaining.

jobst_brandt@hplabs.hp.com
Newsgroups: rec.bicycles.tech