[CR]DuoPar variations

(Example: Framebuilders:Chris Pauley)

Date: Mon, 01 Sep 2008 16:21:28 -0500
To: <classicrendezvous@bikelist.org>
From: "Mark Stonich" <mark@bikesmithdesign.com>
In-Reply-To: <000301c90c2d$6bf80dd0$0201a8c0@Office1>
References: <000301c90c2d$6bf80dd0$0201a8c0@Office1>
Subject: [CR]DuoPar variations

Len Diamond wrote,
>Also the rear derailleur is Huret and appears to be steel. The names
>Ecopar and Duopar keep popping into what is left of my mind. Which one
>is the steel model?

The original DuoPar was almost all sheet steel with aluminum links for the primary parallelogram.

The DuoPar Titane continued the aluminum links but most of the sheet metal was titanium.

After The Titane was introduced the steel model was called the DuoPar Eco. There never was an aluminum version.

The Eco was available in two versions One was rated for a max rear cog of 28t. I've never even seen a picture of one of these.

The regular Eco and the Titane were conservatively rated at 36t max cog. But an early Bikesmith specialty was building custom 7 speed SunTour ProCompe Tandem (not Winner) freewheels using 38t Suntour AG cogs, and the DuoPars shifted those just fine.

http://homepage3.nifty.com/passhunter/hunter/huret/huret.htm shows 4 variations of DuoPars, I have 3 that aren't shown including an NOS Sach/Huret Titane.

I could continue to bore everyone with DuoPar trivia but there are a few important things to remember.

They will only shift well with the primary parallelogram at 45 degrees from horizontal.

Be careful about back pedalling, especially with modern chains. The inner plate wasn't tall enough so if the shifter had been bumped the chain could come off and jam between the jockey and the inner plate. On a tandem it wasn't hard to destroy the deralleur this way. I sold extended inner plates for a few of years. Lon & Susan Haldeman used them on their tandems.

The pulleys have ball bearings. To service the jockey pulley you need a 13mm cone wrench that has been thinned by pressing the wrench against a grinding wheel. http://bikesmithdesign.com/SA/cone-wrench-mod.jpg Shows a 16mm wrench modified thusly for use on Stuemey Archer hubs.

If you do try to service the jockey wheel, take notes so you can get it back together. Easy IF you know what you are doing but counterintuitive if you don't

Mark Stonich;
     BikeSmith Design & Fabrication
       5349 Elliot Ave S. - Minneapolis. MN 55417
            Ph. (612) 824-2372 http://bikesmithdesign.com
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