Hey Grant/All,
Gleaned from my '80 catalog, the original DuraAce rder was designated DA-100; the D-A EX was DA-200. These model numbers had changed to RD-7100/RD-7200, respectively, by 1980.
The DuraAce EX rder had the hatch plate, as Grant mentioned. The hatch plate not only made it possible to extract the chain from the der cage without disassembling the cage or breaking the chain, it also allowed the guide pulley to move further inboard, closer to the spokes. Shimano recommended that only EX rders w/hatch plate be used with freehubs. Did the inner cog sits closer to the spokes on a UniBalance freehub?
In addition to the hatch plate, the D-A EX upper/guide pulley was stainless steel, and the derailleur also incorporated a "sealed mechanism." Precisely what was sealed is not specified in the catalog---might be the guide pulley, might be the upper and/or cage pivots.
The std D-A rder did not have the hatch plate, stainless steel guide pulley or sealed mechanism. Catalog weights have the original D-A at 174g, one whole gram lighter than the D-A EX (175g).
[Warning: rant/digression follows...] Shimano went public in the early '70s, just before the '74 Oil Crisis, and much of the funds raised went into R&D. Every component was examined, performance/interface problems were defined, and by '78/'79 Shimano was introducing quite a large number of innovative component designs. The first 10pgs of the '80 catalog focuses on Shimano innovation, and the list is pretty impressive. Freehubs/cassettes to strengthen rear wheels, differentiated cog/chainring tooth profiles to improve shifting, especially under load, new crankarm/spider profiles to increase crank strength and clearance, increased use of labyrinth seals to protect bearings from contamination, etc, etc. This was before all the Aero/AX hoopla.
At the same time Shimano also sought to prove the worth and durability of their equipment by sponsoring Euro pro road racing teams. You have some very focused engineering yielding innovative componentry that then challenges the dominant Euro component mfrs on their home turf. And the curtain starts to close on our classic/vintage/CR timeline....
Cheers,
Paul Brodek Hillsdale, NJ
On Thu, 22 Apr 2004 15:42:34 -0400, Grant McLean
<Grant.McLean@SportingLife.ca> wrote:
>
>There is indeed a DURA ACE labelled derailleur that is not an EX.
>
>In 1980, both versions are shown in the catalog. The difference is
>that the newer EX version has a quick release plate in the pully cage that
>allows the chain to be removed without taking out a pully. The "plain"
>and earlier dura ace derailleur has a convention cage.
>
>Grant McLean(tm)
>Toronto.Ca
Paul C. Brodek
Hillsdale, N.J. U.S.A.
E-mail: pcb@skyweb.net