SRAM A2 Automatix; introduction to the internals

[scooby214]

it certainly is not too complicated inside.

BTW it isn't a bad idea to remove the RH cone and put a load of grease in there for the planet gears themselves; I'm not sure it will migrate into this part of the hub easily otherwise.

cheers

Thanks for the tip! It's nice that you can remove the RH cone without messing up any adjustments (like what can happen on a Sturmey Archer hub).

[EnquiringMind]

Ha, I wish I'd seen this topic earlier, as it would have saved me a little bit of anxiety!

I built up an Automatix a month or two back to replace the terrible S2C but was dismayed by the early shift point, so resolved to adjust it. It's really easy, and you can see some pictures of the process along with a review on the blog:




Really rather excellent now, and knees are happy...

[scooby214]

Terrific blog post! Your description of unwinding the shift spring will prove helpful for many people, including myself. You make the spring adjustment sound much simpler than what can be found in other places.

A question... You have a picture of the shift spring alone. Does that picture show how your spring looked after unwinding it or before unwinding it?

[EnquiringMind]

It's half way through unfortunately (took me two attempts because I was being cautious, first time I took it up to 13mph). If I remember correctly, the 'arms' of the spring were parallel (180 degrees) when I first took it out, or thereabouts, and closer to an acute angle (but not parallel 0 degrees) when I finished, if that makes sense?

The only slightly fiddly bit is the circlip holding on the weight, which is quite small - I used a pair of screwdrivers to pop it off and on.

Highly recommend just going for it, the spring is not fragile at all (at least, if you just use your hands!) and is fully supported by the axle the weight pivots on, so it's hard to see how it could go wrong even if you bent it a little on the Z-axis.

It's also, out of all the sorts of parts that could go wrong inside a hub gear, probably one of the easier ones to replace from local hardware.

[Brucey]

was the hub fitted to a small wheel or a large one?

BTW years ago they used to do two different hub versions with different shift points for different sized wheels...

cheers

[EnquiringMind]

700C, this is the bike:



Originally had an S5C, terrible, then an S2C, ditto (SA had to send out a missing part for me to install, then it locked up in the frame - all detailed here). Finally the Automatix, but the shifting was silly - I'd almost given up hope.

Fingers crossed though, I think this is the solution. To be fair, it's so easy that it's not a big deal, although IMO a grub screw that allowed you to trim the spring (as with the L-R balance of a v-brake) would be a nicer touch - or just the ability to buy one out of the box that had a better shift point.

[Brucey]

incidentally I read your blog post on the S2C and mine has a serial number of JFA8 and completely different internals; no special added parts required AFAICT. Do you recall which pawl broke in your hub?

Cheers

[scooby214]

Keeping my fingers crossed, too. I think I will tweak mine slightly. I may shoot for a minor jump from 11mph to 13mph. That would allow me to really spin the pedals the way I like.

Thanks again for showing how easy it is to modify the shift point!

EDIT: I just got back from a test ride after modifying my shift point. My new shift point is right at 13mph now, just like I hoped! Now to switch out my chainring and take advantage of the new shift point!

[EnquiringMind]

Excellent, glad to hear it!

@Brucey, one of the direct drive pawls. I think the replacement internal they sent out is the same model as the one pictured - is the serial number stamped on the internal somewhere?

[Brucey]

When you say the same as the pictures, do you mean the ones in your blog?

I've put a few S2C comments in the 'duomatic friction box' thread,

http://forum.ctc.org.uk/viewtopic.php?f=5&t=62500&p=567567#p567567

rather than this thread.

cheers

[breakwellmz]

Hi.

ALL interesting stuff.

It reminded me that i have a Sachs Duomatic hub that i picked up,new, probably fifteen years ago.
It has a coaster brake,which is the reason it has not been used,after i had use of a three speed coaster hub bike which i just could not get on with.
However,after reading this post,i`m wondering whether the braking mechanism can be removed.
Am i right in saying both the Duomatic and Automatix are freewheel hubs,NOT fixed,and you change gear on the Duomatic by pedal back pressure?

[Brucey]

The Sachs Torpedo Duomatic works in a very similar way to the SA S2C Duomatic.

This is one version;



more info here;

http://hubstripping.wordpress.com/torpedo-duomatic-fs/

I don't think you can simply remove the coaster brake, not without replacing the bits with other custom made parts, anyway.

I think the whole idea of a coaster brake is something you have to get used to. It is no weirder than backpedalling to change gear, I reckon.

cheers

[scooby214]

I wish I would've taken pictures of my non-coaster hub when I took it apart yesterday. It has a plastic spacer in the space where the coaster version of the hub has the coaster brake assembly. The plastic spacer slides off the hub, and has five tangs that engage the low gear pawl assembly.

I would think that you would need a spacer of some sort if you removed the coaster assembly from your duomatic hub.

[breakwellmz]

Thanks chaps.

I did persevere with that coaster brake for some time,but it wasn`t for me.
The only way i could consider using this hub would be without the brake.
BTW,would it have the same ratios as the old Orbit 2x6 hub?

[Brucey]

Unlike the current two-speed hubs which are gear-up hubs, the sachs orbit was a two speed gear-down hub. There is a good write-up with links here;

http://sheldonbrown.com/sachs-orbit.html

cheers