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  1. #1
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    Moulton TSR-2 mods New SRAM A2 Automatic

    As a fan of 2 speed hubs in general and specifically the older Sachs Duomatic Automatic 2 speed hub from the '70s, I've been eagerly awaiting the release of the brand new SRAM A2 automatic. There are two versions available in the US, a coaster brake and non-coaster brake hub... I chose the coaster brake version as it would literally drop into my TSR-2 Moulton belt drive bike.. I like the hub .. the coaster brake is excellent, not grabby, easy to modulate, and plenty of stopping power.. the hub itself is fairly quiet (some pawl clicking) and runs pretty freely.. the shifting is predictable and quick... as stock, it shifted at about 7mph on the 406 platform.. I took the hub apart as I did with my past Sach units and modified it to shift at just under 14mph.. just right for my style of riding..

    I built a couple of new wheels for my TSR-2 using a 24h Velocity Aerohead in the rear and a Velocity 20h paired spoke in the front.. from the stock configuration with the Sturmey S2C and 1.5x406 Primos to the Velocity/SRAM/Kojacks, I shed a little over 2lbs... The new SRAM automatic is also slated to be seen on the not yet released Tern Duo.. I can see where this hub might get popular..




  2. #2
    jur
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    Wow

  3. #3
    jur
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    The S2C is about 1.6kg, right? So how much is the Sachs?

  4. #4
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    Quote Originally Posted by jur View Post
    The S2C is about 1.6kg, right? So how much is the Sachs?
    My vintage Sachs Automatic hubs are 1.1kg with brake arm ... The SRAM retail sites lists both new hubs (coaster brake and freewheel) at about 1kg .. of course that can't be .. the new coaster brake hub with rather beefy brake arm was at 1.3kg on my gram scale.. the increased weight of the new SRAM A2 that I'm running has to come from the larger high flange hub shell, redesigned brake and longer axle.. the older Sachs hubs were designed around 110mm OLN widths . the new A2, 120mm, but could easily go 130mm due to the longer axle (over 175mm)

  5. #5
    Eschew Obfuscation SesameCrunch's Avatar
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    Quote Originally Posted by jur View Post
    Wow
    what Jur said.....

  6. #6
    Senior Member ro-monster's Avatar
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    I like it!

  7. #7
    Senior Member kamtsa's Avatar
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    Very nice!

    Can the belt/tensioner handle reliably force in both directions?

  8. #8
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    Wow is right! Where can they be found?
    Dahon Jifo
    Dawes Kingpin 2speed

  9. #9
    Mister Bleak! mconlonx's Avatar
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    What consideration, if any, do you have to take, skipping every third hole in the 36h hub when calculating spoke length on a build like that? Otherwise, just a 1x build?
    Quote Originally Posted by Nicodemus regarding mconlonx View Post
    You, I don't generally think of you as clueless. You're kind of ok.
    I know next to nothing. I am frequently wrong.

  10. #10
    New usename ThorUSA brakemeister's Avatar
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    i see my spokes work out rather nicely :-)

    what a great looking bike. I bet it rides nice as well.
    was the speed change inside the hub difficult to achieve ?
    thor

  11. #11
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    Quote Originally Posted by kamtsa View Post
    Very nice!

    Can the belt/tensioner handle reliably force in both directions?
    No problems, there's no force on it .. it's not really a tensioner but a 'snubber' ... there is some clearance between belt and the roller .. it sits just below the cog to keep the belt from jumping .. much like the belt drive Strida 'snubber' ..

  12. #12
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    Can I ask why you've opted for single-cross lacing?

  13. #13
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    Quote Originally Posted by mconlonx View Post
    What consideration, if any, do you have to take, skipping every third hole in the 36h hub when calculating spoke length on a build like that? Otherwise, just a 1x build?
    I'm sure to be mathematically exact, there must be consideration .. however, I calculated 1x on 3 different online spoke calculators, got 3 different spoke lengths and took the average.. it trued up nicely and the spokes are tight .. I've done 24/36 on a few coaster brake rear wheels for myself.. they're all still rolling along ..

  14. #14
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    Quote Originally Posted by brakemeister View Post
    i see my spokes work out rather nicely :-)
    They're not your spokes any more, I paid handsomely for them ... thanks for the fast service

    Quote Originally Posted by brakemeister View Post
    what a great looking bike. I bet it rides nice as well.
    was the speed change inside the hub difficult to achieve ?
    thor
    Naw, not difficult .. if I can do it, rest assured you can do it..

    It rides awesome .. much better in the city now as it's always in the correct gear at a stop ..

  15. #15
    Raleigh20 PugFixie, Merc LittlePixel's Avatar
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    What's not to like - sweet upgrade to an already super-sacharine ride. +1

  16. #16
    Eschew Obfuscation SesameCrunch's Avatar
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    Quote Originally Posted by BruceMetras View Post

    Naw, not difficult .. if I can do it, rest assured you can do it..

    I know Bruce well enough to say that what comes easily to him may not appear the same way to the rest of us - That's why I call him Maestro Bruce...

  17. #17
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    You gave up on the alex 451? I've yet to complete my 451 duomatic r20
    R20 aka project frankentwenty

  18. #18
    New usename ThorUSA brakemeister's Avatar
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    Quote Originally Posted by SesameCrunch View Post
    I know Bruce well enough to say that what comes easily to him may not appear the same way to the rest of us - That's why I call him Maestro Bruce...
    lol I was thinkin about the same
    lol

    Maestro Bruce has a nice ring to it, doesnt it ? Is the Maestro coming to Interbike show ? I will be on the Sapim booth.... right in the middle of the show ...lol

    thor
    thor

  19. #19
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    Quote Originally Posted by brakemeister View Post
    lol I was thinkin about the same
    lol

    Maestro Bruce has a nice ring to it, doesnt it ? Is the Maestro coming to Interbike show ? I will be on the Sapim booth.... right in the middle of the show ...lol

    thor
    thor
    I do have the opportunity to get there this year, but a hip replacement surgery (not mine thankfully) has stifled that plan.. happily though, the Nor Cal folder contingent will be dutifully represented by one of our own who will be pressed into picture taking and timely reports .. right SC??

  20. #20
    tcs
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    Quote Originally Posted by Dynocoaster View Post
    Wow is right! Where can they be found?
    Google reveals some half dozen sources for the Autmatix2 hubs. If you're one of the 3% of Americans that live within a day's drive of a competent bike shop, they can get you one as well.
    "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

  21. #21
    Eschew Obfuscation SesameCrunch's Avatar
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    Quote Originally Posted by BruceMetras View Post
    I do have the opportunity to get there this year, but a hip replacement surgery (not mine thankfully) has stifled that plan.. happily though, the Nor Cal folder contingent will be dutifully represented by one of our own who will be pressed into picture taking and timely reports .. right SC??
    Yes, I'm still planning to go and will bring cameras to fully document the event. I will stop by and say hello to the Brakemeister for sure!

  22. #22
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    Quote Originally Posted by macnolias View Post
    You gave up on the alex 451?
    Heck no .. the Mu Duo Automatic lives in the trunk of my Alfa Spider .. always at the ready..

  23. #23
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    I thought you had sold the Mu. That bike inspired my Raleigh 2 speed build.
    Dahon Jifo
    Dawes Kingpin 2speed

  24. #24
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    Quote Originally Posted by Dynocoaster View Post
    I thought you had sold the Mu. That bike inspired my Raleigh 2 speed build.
    I had a box stock Uno that I sold.. but never my Duo

  25. #25
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    Ya the Duo has my name next to it in the will
    R20 aka project frankentwenty

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