Advertise on Bikeforums.net



User Tag List

Results 1 to 7 of 7
  1. #1
    Senior Member
    Join Date
    May 2005
    Location
    Terre Haute, Lafayette, or Indianapolis, IN, depending on the day
    My Bikes
    n, I would like n+1
    Posts
    1,916
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    Making a better rear derailleur

    Cross-posted in Recumbents
    Background:
    I'm at Rose-Hulman making a faired recmbent for an American Society of Mechanical Engineers Human Powered Vehicle Competition. It's our third year doing this and we'd like to shrink down our deraileur this year.

    I wanted a Dahon Neos rear derraileur but after two months of promises of these at wholesale, and promises of these at retail from places that just never have them in stock I'm thinking of just making my own. Ideally it will work on 9sp spacing although I'm only going to run 5 gears. Unfortunately I'm travelling on break and don't have any bike parts/callipers/whatever with me. So:
    1:What is the center to center spacing on shimano 9sp cassettes. I know this is posted somewhere but a search didn't turn it up.
    2: What is the cable movement per gear for Shimano 9sp shifters?
    I thought it was a 1:1 ratio but that seems incorrect, perhaps 1.5:1? This should also be measurable, especially if you have a bike with any exposed cabling.

    I would greatly prefer if these measurements were in Metric since I believe that is what they were designed with.

    If anybody has any special wisdom for me in this area that would be appreciated.

    Thank you in advance.


    If all else fails: Does anybody have a Dahon Neos IN STOCK that you would be willing to sell cheaply in exchange for a sponsor sticker on our bike? Also, I remember something about these using SRAM grip shifters. What is the cable pull ratio for those?
    Last edited by jccaclimber; 02-27-08 at 03:26 PM.

  2. #2
    Senior Member
    Join Date
    May 2005
    Location
    Terre Haute, Lafayette, or Indianapolis, IN, depending on the day
    My Bikes
    n, I would like n+1
    Posts
    1,916
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Since it came up over in recumbents I should add that this is a front wheel drive/front wheel steer vehicle. I have used standard derailleurs the past two years and will not have space for one with this year's design.

  3. #3
    Senior Member Bill Kapaun's Avatar
    Join Date
    Feb 2007
    Location
    Mid Willamette Valley, Orygun
    My Bikes
    86 RockHopper,2008 Specialized Globe. Both upgraded to 9 speeds.
    Posts
    6,888
    Mentioned
    2 Post(s)
    Tagged
    0 Thread(s)
    This is what I have for cog/spacer thickness in MM.
    7- 1.85/3.2
    8- 1.80/3.0
    9- 1.78/2.56
    10- 1.60/2.35

  4. #4
    Senior Member
    Join Date
    May 2005
    Location
    Terre Haute, Lafayette, or Indianapolis, IN, depending on the day
    My Bikes
    n, I would like n+1
    Posts
    1,916
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    > 1.78*9+2.56*8;
    36.50mm
    So that leaves a cassette width of 36.5 MM? I guess that is a
    Now, does anybody know the cable movement?
    That leaves a total movement of34.72mm
    > 1.78*8+2.56*8;
    34.72mm
    I managed to find some evidence that the pull ratio is ~1.67:1 which would result in a cable movement of 58mm. Can anyone confirm that?
    > 34.72*1.67;
    57.9824

    Thank you again.

    Edit: If I did that wrong and it's 34.27/1.67 then that's ~20.52mm.

    .
    Last edited by jccaclimber; 02-27-08 at 04:37 PM.

  5. #5
    Senior Member anti.team's Avatar
    Join Date
    Dec 2007
    Location
    Ballard, WA
    My Bikes
    '98 Kona Kula, '8X Univega Sportour SS, '81 Trek 710
    Posts
    150
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    1. CtoC spacing of the 9sp is 4.34mm

    2. Cable pull is 2.5mm per gear, and the RD mech. advantage is ~1.7:1

    Values from this very useful site:
    http://www.ctc.org.uk/DesktopDefault.aspx?TabID=3946

  6. #6
    cycles per second Gonzo Bob's Avatar
    Join Date
    Oct 2003
    Location
    Minnesota
    My Bikes
    Vitus Aluminum, DiamondBack Apex, Softride Powerwing 700, "Generic" Ishiwata 022, Trek OCLV 110
    Posts
    1,790
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Shimano
    9-speed 4.34 mm 1.78 mm 2.56 mm

    I thought Shimano was 2:1. At least I've seen "compatibile with SRAM 2:1" when refering to Shimano rear shifters and derailers. But it could be that the 2:1 is nominal.

    I visited Rose-Hulman for a week when I was in high school (1978?). It was a thing called Camp Retupmoc. Do they still run that?
    Last edited by Gonzo Bob; 02-27-08 at 04:47 PM.

  7. #7
    Senior Member
    Join Date
    May 2005
    Location
    Terre Haute, Lafayette, or Indianapolis, IN, depending on the day
    My Bikes
    n, I would like n+1
    Posts
    1,916
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    They still run Catapault for the high school students between junior and senior year if that's what you mean. They also run Fast Track for incoming freshman. Fast Track is Calc 1/2/3 in 5 weeks and is apparently the worst, but most useful experience you can go through with math unless you're a math major.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •