To be nitpicky, "high normal"/"low normal" is terminology that's meaningful primarily for parallelogram derailleurs. We operate as if those are the only derailleurs that exist because parallelogram derailleurs (mostly developed as extrapolations and knockoffs of Campagnolo's 1951 Gran Sport, with important upper pivot developments by Simplex and then extensive advancement by Shimano and Suntour) have essentially eliminated the phantasmigorical range of derailleur designs that existed before 1960.
Consider the Cyclo, a 1930s design employed widely by French framebuilders for both touring and townie bikes. The derailleur mounts under the driveside chainstay, and has no spring action at all - a single looping cable caused a helical shaft to pull the derailleur's pulley cage in one direction or the other, and the cage goes however far you pull it. In the case of the Cyclo, or other derailleurs in the category Jan Heine refers to as "desmodromic" such as the Nivex Rene Herse is duplicating at (I'm sure) great expense, there is no "normal"; there is no position to which the derailleur cage returns when cable tension is released because cable tension is equal throughout the derailleur's range. There is no spring to return the cage to a point of stasis. https://www.disraeligears.co.uk/site/french_patent_582247_-_cyclo.html Our understanding that a "normal" derailleur state is conditioned by the derailleurs which which we each have personal experience is easy to forget. A couple years ago, Grant published a blahg item commenting on a 1950s French racer brought in by our mutual acquaintance Ted Trambley of Martinez, whom I know from CR primarily as a hobbyist restorer like myself. He had brought in an early 1950s Alcyon (a marque which won a fair number of Tours de France in the 1920s-30s) equipped with a Huret suicide front derailleur (a mutual interest of Grant's and mine; I got Grant's reassembled after an attempted cloner had sent it back from Australia in pieces) and a Huret Louison Bobet rear derailleur. That rear derailleur fits into a category I call "pullchain", because I haven't seen another generic name for the type; the shift cable pulls a chain which goes through the derailleur body to the pulley cage, and increasing tension on the shifter+cable+chain draws the pulley cage outwards towards the body of the derailleur projecting outward from the frame, with counteracting pressure from a sort of flat clock-type spring. https://www.rivbike.com/blogs/grant-petersens-blog/late-march-3 Grant's post gets excited about the fact that this means that relaxing cable tension means the pulley cage goes inwards towards the large cog - i.e., a "low normal"/"rapid-rise" derailleur. What he doesn't comment on is the fact that in the 40s-50s there were dozens of derailleur models from multiple companies in multiple countries (including Japan; the first Shimano and Suntour derailleurs were knockoffs of Simplex pullchain derailleurs) that did exactly the same thing, because that's just how the design works. Pullchain rears were the most common format of racing derailleur in the era, until enough teams bought Campagnolo's parallelogram derailleurs to displace them. I don't know why Grant doesn't mention this; I'm guessing it's because that style/design of derailleur is outside the range of his first-hand experience, as it is for me until recently and for almost any other rider/bike tech nerd under 85. "Absolute normal"? "Opposite movement"? Who's the Shifting Pope who gets to decide what "normal" is, from which everything else is a deviation? People have been making multigeared bikes for over 100 years, most of which have incorporated some mechanical means of changing gears while in motion. A few systems are still around largely because all the manufacturers dropped the other systems during the Eisenhower and Kennedy Administrations, but there's patents and surviving examples of other options. IMHO, rapid-rise parallelogram derailleurs are a little foolish - not because they've been tried in the marketplace several times and very few people other than Grant liked them, but because they're trying to force a dropped parallelogram mechanism to produce the opposite result of what the mechanism was designed to do, which is likely to be done with Rube Goldberg engineering. How much more of that do we really need? Peter Adler who was a devout rider of the Huret Duopar, the world's most over-engineered derailleur, for well over a decade in Berkeley, California/USA On Monday, March 18, 2024 at 8:17:37 PM UTC-7 J J wrote: High normal refers to “regular” rear derailleurs, for which the default position with no spring tension is in the highest gear. Hence, high normal. Low normal (what Shimano called Rapid Rise) is the opposite: the default derailleur position without spring tension is in the lowest (largest) gear. This is why Grant/Riv are calling their low normal derailleur in development the “OM,” for opposite movement, sort of rejecting the notion that high normal is the absolute normal. The different movements are just opposite each other. -- You received this message because you are subscribed to the Google Groups "RBW Owners Bunch" group. To unsubscribe from this group and stop receiving emails from it, send an email to rbw-owners-bunch+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/rbw-owners-bunch/81dcdcd4-fcd4-45ce-8ade-47f217d8bb3dn%40googlegroups.com.
