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Old 08-22-11, 03:28 PM   #1
BruceMetras
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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..



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Old 08-22-11, 05:18 PM   #2
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Wow
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Old 08-22-11, 05:20 PM   #3
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The S2C is about 1.6kg, right? So how much is the Sachs?
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Old 08-22-11, 05:54 PM   #4
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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)
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Old 08-22-11, 10:39 PM   #5
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Wow
what Jur said.....
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Old 08-22-11, 10:51 PM   #6
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I like it!
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Old 08-22-11, 11:04 PM   #7
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Very nice!

Can the belt/tensioner handle reliably force in both directions?
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Old 08-23-11, 07:15 AM   #8
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Wow is right! Where can they be found?
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Old 08-23-11, 07:29 AM   #9
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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?
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Old 08-23-11, 07:40 AM   #10
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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 ?
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Old 08-23-11, 07:58 AM   #11
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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' ..
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Old 08-23-11, 08:00 AM   #12
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Can I ask why you've opted for single-cross lacing?
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Old 08-23-11, 08:06 AM   #13
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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?
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 ..
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Old 08-23-11, 08:15 AM   #14
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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

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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 ..
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Old 08-23-11, 05:13 PM   #15
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What's not to like - sweet upgrade to an already super-sacharine ride. +1
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Old 08-23-11, 05:20 PM   #16
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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...
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Old 08-23-11, 11:43 PM   #17
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You gave up on the alex 451? I've yet to complete my 451 duomatic r20
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Old 08-24-11, 08:20 AM   #18
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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

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Old 08-24-11, 09:00 AM   #19
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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

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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??
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Old 08-24-11, 09:07 AM   #20
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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.
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Old 08-24-11, 09:07 AM   #21
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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!
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Old 08-24-11, 09:10 AM   #22
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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..
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Old 08-24-11, 05:12 PM   #23
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I thought you had sold the Mu. That bike inspired my Raleigh 2 speed build.
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Old 08-24-11, 06:43 PM   #24
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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
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Old 08-24-11, 06:58 PM   #25
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Ya the Duo has my name next to it in the will
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