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Old 08-27-12, 04:32 PM   #1
smontanaro 
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Help me understand what changed when SunTour's slant parallelogram patent expired...

I'm trying to understand how rear derailleur movement of the SunTour slant parallelogram works and was different than its contemporary competition, particular from Shimano. Consider these two Shimano 600EX versions:

Both seem to have the cage paralleolgram angled from "northwest" to "southeast", not unlike the SunTour Cyclone, and unlike the Campy NR (where the cage runs "north" to "south"). The Arabesque derailleur dates from well before the expiration of SunTour's patent. I think the later 600EX dates from after the expiration of that patent.

I'm clearly misunderstanding something about the way the cage moves between the earlier Arabesque and later 600EX derailleurs. Can someone explain this too me? Pointers to pictures or graphics demonstrating the slant parallelogram mechanism would be great. I found this YouTube video, but the description implies that the Arabesque derailleur has a slant parallelogram design.

Thx,

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Old 08-27-12, 04:42 PM   #2
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The "dogleg" of the Arabesque and certain of the later Simplex derailers doesn't use the slanted parallelogram, and so wouldn't violate any patents.
The difference with the slant parallelogram was that the parallelogram pivots were off-axis from being perpendicular to the axle, so that the shifting motion moved the cage further away from the axle as the larger sprockets were engaged.

Shimano spent years developing SIS, knowing full well when the patent expired. Thus, when the first SIS gruppos appeared around the same time that Suntour's patent expired, Shimano was able to have slanted derailers ready for sale to give SIS the best performance (and market acceptance) possible.
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Old 08-27-12, 04:53 PM   #3
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The Shimanos you linked are drop parallelogram designs, but the parallelograms are not slanted so the top pulley follows the shape of the cluster as it moves across. There was never any patent protection for drop parallelograms. It's the slant that was protected. The slant of the Suntour honor can easily be seen in that video you linked.
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Old 08-27-12, 05:00 PM   #4
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Thanks. I was considering "slant" in the wrong axis. Now that I know what axis to pay attention to, I understand completely.

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Old 08-27-12, 05:17 PM   #5
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The whole point of slant-par was to keep the top jockey wheel as close as possible to the sprockets, ensuring quick chain movement and crisp shifting. With a straight-par the gap between jockey wheel and sprocket increased as you shifted to smaller sprockets since the parallellogram more or less moved straight outwards.
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Old 08-27-12, 05:58 PM   #6
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Quote:
Originally Posted by dddd View Post
Shimano spent years developing SIS, knowing full well when the patent expired. Thus, when the first SIS gruppos appeared around the same time that Suntour's patent expired, Shimano was able to have slanted derailers ready for sale to give SIS the best performance (and market acceptance) possible.
This is THE important bit of strategy. Campagnolo instead in the early 80's was focusing on an alternative to what they had (and almost everyone had copied). A wasted effort, the most usable was the control rod seen on the Chorus, or was it Croce D' une? mechanism. Shimano also focused on a top down strategy, the top group got the new SIS first. In the past, new features would sometimes show up on downmarket groups first, like the first octolink crank attachment concept, that scheme did not serve them well.
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Old 08-27-12, 06:05 PM   #7
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I sincerely thank you all for informing me on this, and Skip for asking the question.
Killer stuff, and when I repeat it someday, people will think I actually know something.
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