Advertise on Bikeforums.net



User Tag List

Results 1 to 17 of 17
  1. #1
    Senior Member
    Join Date
    Oct 2009
    Location
    England, currently dividing my time between university in Guildford and home just outside Reading
    My Bikes
    Too many to list here!
    Posts
    1,769
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    Sturmey-Archer dual-sprocket?

    Is there any way to retrofit the dual sprocket setup seen on Brompton bikes to a standard Sturmey-Archer 3-speed? Does it require a new driver, or is there some sort of double sprocket assembly that attaches to the standard 3-spline one?

    Also, how does the Brompton derailleur attach to the frame? Is it a standard hanger? If not, is there any reason a standard derailleur wouldn't work to shift between the two sprockets, if the limit screws were set right?

    As you might imagine, I'm trying to turn a 3-speed into a 6-speed, just to see if I can. Any help from the various Sturmey-Archer gurus on here would be appreciated

    Thanks in advance

  2. #2
    coprolite fietsbob's Avatar
    Join Date
    Jun 2010
    Location
    NW,Oregon Coast
    My Bikes
    7
    Posts
    35,762
    Mentioned
    15 Post(s)
    Tagged
    0 Thread(s)
    Is there any way to retrofit the dual sprocket setup seen on Brompton bikes to a standard Sturmey-Archer 3-speed? Does it require a new driver, or is there some sort of double sprocket assembly that attaches to the standard 3-spline one?
    the UK & TW hubs may not be able to cross breed in some ways.
    the driver sub assembly is different, you would have to tear the matching type hub apart,
    and swap that part..
    probably want the longer hub's axle if not a very narrow frame rear spacing.

    newer BWR use 1 kind of sprocket. I think the Shimano BMX cog is the new spline type.

    prior were sourced from Sachs, and use 3 lobe spline sprockets ,
    common to 3 speeds of many brands.
    AFAIK, very few cog sizes made in 3/32 type thickness, most 1/8"
    Also, how does the Brompton derailleur attach to the frame? Is it a standard hanger?
    No, they are completely unique, shifts by having a fork shove the pulley sideways.
    there is a boss for that pivot, under the chainstay tube

    You can also make a 3 into 6 speed by keeping 1 cog on the hub, a thin one,
    so a 5.6.7 speed chain fits
    and running a 2 chainring crank., and a front derailleur..

    Rear derailleur/non shifting chain-tensioner takes up the slack when on the small chainring..

    Seems a S3X will screw on a White industries Dos freewheel on,
    and thus offer a 2 speed external pair , that way..
    Last edited by fietsbob; 08-18-11 at 06:21 PM.

  3. #3
    headtube. zzyzx_xyzzy's Avatar
    Join Date
    Sep 2008
    Posts
    804
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by Airburst View Post
    Is there any way to retrofit the dual sprocket setup seen on Brompton bikes to a standard Sturmey-Archer 3-speed? Does it require a new driver, or is there some sort of double sprocket assembly that attaches to the standard 3-spline one?
    This is pretty high on the effort scale but I made one by brazing a cog taken from a multispeed freewheel to a standard gearhub cog. It works but if I were doing it again I'd be more careful about getting the cogs exactly centered (chain tension is uneven on the big cog.)


    P9070043 by Saccade, on Flickr


    P9070047 by Saccade, on Flickr

  4. #4
    coprolite fietsbob's Avatar
    Join Date
    Jun 2010
    Location
    NW,Oregon Coast
    My Bikes
    7
    Posts
    35,762
    Mentioned
    15 Post(s)
    Tagged
    0 Thread(s)
    yea a chain tensioner would make up for 2nd cog not being quite on center..

  5. #5
    Old fart JohnDThompson's Avatar
    Join Date
    Nov 2004
    Location
    Appleton WI
    My Bikes
    Several, mostly not name brands.
    Posts
    11,846
    Mentioned
    3 Post(s)
    Tagged
    0 Thread(s)
    Sturmey-Archer cogs are slightly dished. An old trick was to take two cogs with the concavities facing in opposite directions to run a two-cog set-up on a standard SA hub.

  6. #6
    coprolite fietsbob's Avatar
    Join Date
    Jun 2010
    Location
    NW,Oregon Coast
    My Bikes
    7
    Posts
    35,762
    Mentioned
    15 Post(s)
    Tagged
    0 Thread(s)
    just !/8" chain does not make the best derailleur chain,
    and most S-A cogs are for 1/8" .

    other than that ..

    Let us know how it comes out.
    Last edited by fietsbob; 08-19-11 at 10:43 AM.

  7. #7
    tcs
    tcs is offline
    Palmer tcs's Avatar
    Join Date
    Mar 2007
    Location
    Parts unknown
    Posts
    4,123
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by JohnDThompson View Post
    Sturmey-Archer cogs are slightly dished. An old trick was to take two cogs with the concavities facing in opposite directions to run a two-cog set-up on a standard SA hub.
    Yep, riders have been doing this for over 75 years. Common half step cog pairs were 19-22 and 18-21.
    "When man first set woman on two wheels with a pair of pedals, did he know, I wonder, that he had rent the veil of the harem in twain? A woman on a bicycle has all the world before her where to choose; she can go where she will, no man hindering." The Typewriter Girl, 1899.

    "Every so often a bird gets up and flies some place it's drawn to. I don't suppose it could tell you why, but it does it anyway." Ian Hibell, 1934-2008

  8. #8
    Senior Member
    Join Date
    Oct 2009
    Location
    England, currently dividing my time between university in Guildford and home just outside Reading
    My Bikes
    Too many to list here!
    Posts
    1,769
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Thanks guys! I've looked at SJS cycles' website, they have a selection of 3/32" SA sprockets, so I might go with a pair of those, as I can't seem to find the Brompton driver on it despite them selling Bromptons and spare SA parts. I'll just use an old rear mech to do the shifting, and I'll let you know how it turns out.

  9. #9
    Collector of Useless Info
    Join Date
    Aug 2009
    Posts
    1,173
    Mentioned
    3 Post(s)
    Tagged
    0 Thread(s)
    I did it with an old Sturmey-Archer AW hub- I don't know if the hub body is different now or not. I took a dremel grinder to the inner splines of a couple of 7-speed Shimano hyperglide cogs. I ground the 9 square splines down to 3 half-moon shaped splines, then with a 7-speed spacer, the cogs fit perfectly onto the AW hub body. Add a derailleur and voila!






  10. #10
    aka Tom Reingold noglider's Avatar
    Join Date
    Jan 2009
    Location
    West Village, New York City
    My Bikes
    too many
    Posts
    17,564
    Mentioned
    5 Post(s)
    Tagged
    0 Thread(s)
    Very clever, cycle_maven!
    Please email me rather than sending me a private message. My address is noglider@pobox.com

    Tom Reingold
    New York City and High Falls, NY
    noglider's ride blog

  11. #11
    coprolite fietsbob's Avatar
    Join Date
    Jun 2010
    Location
    NW,Oregon Coast
    My Bikes
    7
    Posts
    35,762
    Mentioned
    15 Post(s)
    Tagged
    0 Thread(s)
    AH, I see ..
    http://www.sjscycles.co.uk/sturmey-a...778-prod19337/

    andhttp://www.sjscycles.co.uk/sturmey-a...858-prod19354/
    would cover that..
    theres a 3/32 17t too, but thats It. .. 3 out of 30.

    SA has a US distributor in Cal, since they are made on the Pacific rim now.
    so might be available thru the retail food chain..
    Last edited by fietsbob; 08-19-11 at 01:46 PM.

  12. #12
    tcs
    tcs is offline
    Palmer tcs's Avatar
    Join Date
    Mar 2007
    Location
    Parts unknown
    Posts
    4,123
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by cycle_maven View Post
    I don't know if the hub body is different now or not.
    The cog interface on the driver has been the same since the early fifties, when S-A went to the three-spline format.
    "When man first set woman on two wheels with a pair of pedals, did he know, I wonder, that he had rent the veil of the harem in twain? A woman on a bicycle has all the world before her where to choose; she can go where she will, no man hindering." The Typewriter Girl, 1899.

    "Every so often a bird gets up and flies some place it's drawn to. I don't suppose it could tell you why, but it does it anyway." Ian Hibell, 1934-2008

  13. #13
    Old fart JohnDThompson's Avatar
    Join Date
    Nov 2004
    Location
    Appleton WI
    My Bikes
    Several, mostly not name brands.
    Posts
    11,846
    Mentioned
    3 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by fietsbob View Post
    AH, I see ..
    http://www.sjscycles.co.uk/sturmey-a...778-prod19337/

    andhttp://www.sjscycles.co.uk/sturmey-a...858-prod19354/
    would cover that..
    theres a 3/32 17t too, but thats It. .. 3 out of 30.

    SA has a US distributor in Cal, since they are made on the Pacific rim now.
    so might be available thru the retail food chain..
    There are 3rd party cogs for 3/32" chain that will work with SA hubs. And as noted above, a minor surgical procedure will allow common Shimano cogs to work on SA hubs as well.

  14. #14
    coprolite fietsbob's Avatar
    Join Date
    Jun 2010
    Location
    NW,Oregon Coast
    My Bikes
    7
    Posts
    35,762
    Mentioned
    15 Post(s)
    Tagged
    0 Thread(s)
    Yea, AW3 spline is a de facto standard.. common for many makers of 3 speeds..

  15. #15
    Senior Member
    Join Date
    Oct 2009
    Location
    England, currently dividing my time between university in Guildford and home just outside Reading
    My Bikes
    Too many to list here!
    Posts
    1,769
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    OK, it took me a little while, but I've done it!

    Here are a few pics
    PICT0019.jpg
    PICT0021.jpg

    The shift lever is a cheap plastic Shimano friction one, it's aleft-hand unit and it's mounted underneath my left brake lever. The derailleur is the Huret one that the bike had when it was given to me, which went in my shed when I switched to IGH.

    Sorry about the bad-quality pics, if anyone wants better ones I can borrow a better camera.

  16. #16
    bike whisperer Kimmo's Avatar
    Join Date
    Dec 2009
    Location
    Melbourne, Oz
    My Bikes
    - - - - - - - - - - - - - - http://velospace.org/node/36949 http://velospace.org/node/47746 http://velospace.org/node/47747
    Posts
    6,529
    Mentioned
    3 Post(s)
    Tagged
    0 Thread(s)
    What do you do about the circlip? Doesn't the assembly have to be as thin as a 1/8 cog?

    I had to come up with three of these for Bikezilla...


  17. #17
    Senior Member
    Join Date
    Oct 2009
    Location
    England, currently dividing my time between university in Guildford and home just outside Reading
    My Bikes
    Too many to list here!
    Posts
    1,769
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    There was a spacer underneath the sprocket, which I removed. The total sprocket thickness is 2 x 3/32", which is 3/16", or 1/16" thicker than a 1/8" cog. The spacer I removed was just under 1/16" thick, so the overall thickness is slightly greater than it was to begin with, but circlip just barely fits on.

Posting Permissions

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