NetNews Usenet Archive 1992 #31/NN_1992_31.iso/spool/rec/bicycles/tech/2883

Internet Message Format | 1993-01-01 | 5.5 KB

From: [e-mail] (Jobst Brandt)
Date: Fri, 1 Jan 1993 00:26:31 GMT
Subject: Re: B. Rohloff on Rohloff chains
Message-ID: <[e-mail]>
Organization: Hewlett-Packard Laboratories, Palo Alto, CA
Path: sparky!uunet!cs.utexas.edu!sdd.hp.com!hpscit.sc.hp.com!hplextra!hplred!jbrandt
Newsgroups: rec.bicycles.tech
References: <[e-mail]>
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It was nice to see that Rohloff is abreast of what we argue about
here and that there is interest in giving bicyclists a better
product.  As I mentioned in my posting about the chain measurements,
there is a basic similarity between the Rohloff and the Sedis Sport
chain and that Rohloff had addressed some of the problems of this
design.

The main advance of this design is that instead of a sleeve on which
the rollers of the chain ride and inside of which the link pin
rotates, the side plates are swaged inward to form a collar that
acts as a half sleeve.  The advantage is twofold.  The side plates
are stronger because the collar is a load carrying part while the
conventional sleeve only takes strength away from the sideplate
because it requires a larger hole that is bored out to accept the
sleeve.  The other is that there are fewer parts to assemble and to
contribute to tolerances.

The major drawback with this design has been that in the wet, water
has more direct access to the pin bearing that was formerly
protected by the sleeve.  The loss of lubricant often causes welding
between pin and link so that the chain skips when entering the
driven sprockets (the tight link syndrome).  The Sedis Sport chain is
most vulnerable to this failure when new and this is where Rohloff
made an improvement.  By increasing the contact area of the pin and
its bearing surface, even with marginal lubrication, links should
not bind.  I have no experience with this chain so I can only guess
whether this measure has alleviated the condition.

Greater contact is achieved by the shape of the hole in which the
pin rides.  Instead of furnishing a round hole with clearance for
the pin, the hole has two radii.  On the pulling side, the hole
closely fits the pin while the other 2/3 of the hole has a larger
clearance radius.  From what I could measure and what Rohloff states
quantitatively, the close fit comprises 1/3 if the hole
circumference.  In fact the hole is just as large in X as in Y
except that the side walls slope in to a smaller radius on the
pulling end of the hole.

To put all this in perspective, I measured three chains and found
that they were essentially identical except for the pin hole shape.
The Regina (conventional), Sedis, and Rohloff all used essentially
the same size pins and sleeve/collar dimensions.  The Regina CS-X
was the narrowest and the Sedis was the smallest cross section
having the lowest side plates.  The Regina used sleeves and rollers
made of rolled up flat material and therefore had a split in them.
The others used formed seamless material.  This means that the
formed material could not take advantage of the same alloys used by
Regina.

Since most chains are rapidly worn out by adding oil to them in use,
the comparative wear durability is not appreciated and the less
expensive Sedis design has taken over the market.  This may not be
a disadvantage because the only complaint I had was that a new chain
ridden in alternately wet and dry conditions would get stiff link
syndrome.  If the Rohloff design removes this problem then an
improvement in price/performance has been made.  Nevertheless, the
no longer available Regina chain shifted markedly more smoothly with
its cut out sideplates that allowed easy transfer to a larger
sprocket whose teeth fit through the notches in the side plates.

All three chains had their inner links, the ones that hold the
rollers, spaced at 0.500 inches and the pins spaced at 0.500-pin
clearance.  THere is no short pitch to anticipate chain wear.  There
is only a reduced radius that fits the pin diameter as a worn chain
would have, and this is on the Rohloff.  Therefore, although the
pins are spaced closer than 0.500 inch in the outer plates, this
only accounts for the clearance of the pin in its hole.  The new
chain pitch is exactly 0.500 as closely as can be manufactured.

For the statisticians I have a list of measurements taken on a more
accurate machine than last time.  These are not the design
dimensions but only what could be measured.

                  Sedis Sport         Rohloff         Regina CS-X
                 -------------     -------------     -------------
                  mm     inch       mm     inch       mm     inch
pin length       7.35    0.289     6.90    0.272     7.20    0.283
pin diameter     3.62    0.143     3.61    0.142     3.60    0.141
bearing hole     3.71    0.146     3.73    0.147     2.68    0.106
chain height     8.17    0.322     9.10    0.358     8.48    0.334
chain width      7.30    0.287     7.20    0.283     7.20    0.283
link width       4.44    0.175     4.15    0.163     4.54    0.179
t outer plate    1.01    0.040     1.05    0.041     1.00    0.040
t inner plate    1.00    0.040     1.10    0.043     1.00    0.040
l pin centers   12.62    0.497    12.50    0.492    12.60    0.496
roller centers  12.70    0.500    12.70    0.500    12.70    0.500
roller OD        7.63    0.300     7.70    0.303     7.70    0.303
roller ID        5.35    0.211     5.35    0.211     5.20    0.205
roller width     2.20    0.087     2.09    0.082     2.22    0.087
Collar height    1.00    0.040     1.10    0.043     5.12*   0.202

* Regina sleeve length = sleeve protrudes from link