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Old 11-21-12, 07:00 PM   #1
Lazarus Short
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Old-School Gearing Question

I just got finished paring back my 5-speed freewheel from 14-38 (Kansas City hills gearing) to 14-28 (high plains gearing). I had even considered 14-24. BTW, I used Mike Sherman's Bicycle Gear Calculator to decide on the exact gearing - it's fast, and informative of any gaps in the gearing - goodbye semi-log paper and gear charts.

My old PX-10 is set up with Huret Duopar rear and Huret front derailleurs. The Duopar did very well on the 14-38, actuated by a Suntour indexed barend shifter - it works! I also have a Sachs-Huret ECO S rear derailleur, and there is a 24 and 28 tooth position for the tension spring, so it should be good to go on the 14-28. My question concerns the chain-wrap capacity. The front TA crankset is 30-46-50, so does the ECO S have sufficient capacity for that? Maybe someone on this forum can tell me.
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Old 11-21-12, 07:14 PM   #2
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if not a long cage RD, get one . friction shift, no specifics,

just a long distance for pulley to pull back when extra slack.
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Old 11-21-12, 07:33 PM   #3
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Is it this guy? http://www.velobase.com/ViewComponen...108&AbsPos=179 There are other Ecos and DuoPars on Velobase under the Sachs and Huret names.
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There's no such thing as too far.. just lack of time
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Old 11-21-12, 07:43 PM   #4
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Yeah, thanks! I looked up the ECO S on the www, and it wraps 31 teeth max - not enough. The Duopar is a bit bent, sooooo, since I already have Suntour barends mounted, I'm going to try a Suntour on the rear. I've got these:

7-GT

XC Sport 7000

Accushift -4050

The biggest factor against them is that Suntour rear derailleurs are not at all compatible with Simplex dropout mounts. The PX-10 came with Suntour when I bought it second-hand, and it made wheel changes a challenge. I might try some sort of quick-release skewer...
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Old 11-21-12, 07:45 PM   #5
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Is it this guy? http://www.velobase.com/ViewComponen...108&AbsPos=179 There are other Ecos and DuoPars on Velobase under the Sachs and Huret names.
No, it was this site: http://www.disraeligears.co.uk/Site/...railleurs.html
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Old 11-21-12, 07:50 PM   #6
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I can tell you that the a-4050 won't like a triple, either. I tried running mine with a 52/42/32 triple and 14-28T freewheel and it didn't have nearly enough capacity.

The 7-GT should get the job done, though! http://www.velobase.com/ViewComponen...108&AbsPos=393
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Old 11-21-12, 07:58 PM   #7
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I can tell you that the a-4050 won't like a triple, either. I tried running mine with a 52/42/32 triple and 14-28T freewheel and it didn't have nearly enough capacity.

The 7-GT should get the job done, though! http://www.velobase.com/ViewComponen...108&AbsPos=393
Yeah, I thought the a-4050's cage looked a bit short. The 7-GT would do, I'm sure, but it's fugly!

Hey, I recall that to get more chain wrap out the Simplex L.J. Super I once had on the PX-10, I replaced the short alloy cage with a long steel cage from a Simplex Maxy. I wonder if I could make another Frankenrailleur out of the two Hurets? Crazy...

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Old 11-22-12, 07:40 AM   #8
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In real life you might not need as much slack take up capacity as the calculations suggest.

Do you use all of your freewheel gears in combination with your granny chainring? I certainly don't. The only time that I use my granny is on steep hills and only in combination with my biggest couple of rear cogs. If I never shift into the 30/14 combination, I don't need enough slack take up to handle that combination.
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Old 11-22-12, 09:28 AM   #9
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In real life you might not need as much slack take up capacity as the calculations suggest.

Do you use all of your freewheel gears in combination with your granny chainring? I certainly don't. The only time that I use my granny is on steep hills and only in combination with my biggest couple of rear cogs. If I never shift into the 30/14 combination, I don't need enough slack take up to handle that combination.
+1. As long as the chain is made long enough to shift safely into big-big, you can sacrifice the ability to use small-small with no problems. All that happens if you forget is that the chain goes slack and it's a bit noisy. As RG notes, there is no need for small-small as the same gear is available elsewhere.
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Old 11-22-12, 02:39 PM   #10
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The biggest factor against them is that Suntour rear derailleurs are not at all compatible with Simplex dropout mounts. The PX-10 came with Suntour when I bought it second-hand, and it made wheel changes a challenge. I might try some sort of quick-release skewer...
I have a Velosolex with Simplex dropouts. I was able to cut a notch in the dropout with a Dremel that will catch the B screw from a Suntour V-GT just fine. The axle to pivot distance seems long, so the B screw is backed off pretty far, but it works well, much better than the Simplex derailleur that was originally spec'ed. I have used it with up to 32 tooth, seems like it would work with a bigger cog, currently running 14-28. By the way, this was done in 1976 when I bought it new.
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Old 11-23-12, 06:57 AM   #11
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I know where Retro Grouch and HillRider are coming from. I looked at the chart of my gearing, and realized that for practical purposes I had five speeds on the 46-tooth chainwheel, plus an overdrive on the 50x14 and an underdrive on the 30x28. That is how I intend to use it anyway.

MikeWMass suggests that I Dremel a place for the "B" screw of a Suntour derailleur, but I still have the problem of the Simplex mount lacking threads (and I think the hole is too big to tap anyway), and the threads of the Suntour are not long enough for a nut on the other side. I still see a quick release, perhaps a seatpost skewer as the answer if I go Suntour.
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