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From: wagner@uw-june (Dave Wagner)
Newsgroups: net.bicycle
Subject: Touring derailleurs, specifically the Duopar
Message-ID: <157@uw-june>
Date: Mon, 12-Aug-85 15:43:20 EDT
Article-I.D.: uw-june.157
Posted: Mon Aug 12 15:43:20 1985
Date-Received: Tue, 20-Aug-85 02:58:45 EDT
Organization: U of Washington Computer Science
Lines: 77

Allow me to share with you my experience with the Huret Duopar:

I have just returned from a 3 week, 1100 mile bike tour (Washington/
British Columbia/Banff-Jasper).  Before the tour, I decided the ol'
Shimano Crane GS (anybody else remember those?) was getting a little
sloppy, so I decided to purchase the whizziest derailleur around,
the Duopar.  The Duopar is unique in that it utilizes two pantograph
mechanisms, one to move the derailleur body in and out (normal) and
the second to move the cage up and down (unusual).

Well, I was really impressed.  The thing shifted practically at the speed
of thought!  I was so used to overshifting with the old derailleur that
I was skipping around all over the freewheel until I got used to it!

So I'm out in the middle of nowhere, right, and suddenly I discover that
the Duopar's cage is getting mangled because the chain keeps slipping in 
between the jockey (upper) pulley and the inside cage plate.  You see, Huret
made a fatal design error in the Duopar:  the inside (closer to the spokes)
cage plate is NOT attached to the jockey wheel axle; it is attached to
the tension wheel axle and to a small pin just below the jockey wheel.
The result is that the cage plate gets bent and the chain keeps slipping
in there.  With bar-end shifters, as I'm sure anyone who owns
them is aware, it's pretty common to have your thigh hit the shift levers
when you dismount/mount the bike; this results in a slackening of the
cables and the rear derailleur trying to move out; which results in the
chain slipping into the aformentioned sore spot on the Duopar just about
every time you get back on the bike!!!!  The problem is exacerbated by 
the aforementioned cage pantograph mechanism:  you wouldn't believe the
way this thing can twist itself up!  The really bad stuff happens when you 
are rolling the bike backwards, as you commonly do when trying to position 
a loaded bike against a wall or signpost; the derailleur absolutely 
gets mangled if you don't watch what you're doing.  

Anyway, as the tour went on I found myself constantly bending and 
re-bending the cage every time it would mangle itself.  
Near the end of the tour I was seriously wondering if I would even
be able to finish!  I couldn't use certain granny gears because
the derailleur was no longer willing to take up the chain slack,
and in other gears the jockey pulley was grinding against the cogs!
And on the second-to-last day of the tour, I had a mangle that was so
bad that it twisted one of the chain links - and I wasn't carrying
a chain riveting tool!!!!  (I bent the link back using a couple of
vice grips!)

***************** THE IMPORTANT LESSON STARTS HERE *******************

Pretty soon I remembered what it was that I liked about the Shimano
derailleur:  it's nearly indestructible.  Shimano makes the only long
cage derailleurs that I know of that have both cage plates attached
to both pulley axles.  The result is a very strong cage.  Suntour
cages, as you probably well know, are open on one side to allow easy
chain removal from the cage.  (The derailleur I had before the Shimano
was a Suntour Cyclone, whose cage also bent.)  This is even true of
their so-called mountain bike derailleurs, which is really ludicrous
if you stop to think about it!  On a mountain bike component, strength
and reliability should be the numero uno consideration, and things like
saving a few grams of cage weight (!) or even convenience of chain
removal should not even be a close second.  I think that from now on I 
will stick to Shimano rear derailleurs.

Anyway, when I got home the first thing I did is throw away that piece
of junk and put my old Shimano Crane back on.  And you know what?  It
still shifts beautifully!

I'd be interested to hear other people's experiences with touring
derailleurs.

			Dave Wagner
			University of Washington Comp Sci Department
			wagner@washington.arpa
			{ihnp4,decvax,ucbvax}!uw-beaver!uw-wally!wagner

"The surest thing there is is we are riders,
 And though none too successful at it, guiders,
 Through everything presented, land and tide
 And now the very air, of what we ride."
	- Frost