SA N-driver - 2 cogs on an AW ?

[hoogerbooger]

I think I've read here that it's possible to swap the NIG driver to an N-driver on a Sturmey Archer SRF3...... which would allow me to set one up on my 6 speed Brompton ( as the gear ratios would work out better than a BWR with my Schlumpf speed drive to give a resonable touring range over 12 gears)

Would I be right in thinking that you can't fit an N-driver or fit 2 cogs on a pre-NIG AW ? ( As a pre-NIG AW sounds more robust/reliable even if I also fitted an oil port to an SRF3)

[Brucey]

if by 'N driver' you mean HSA800



as fitted to a 6s Brompton's BWR hub, then yes, this will fit a SRF3, albeit it will change the RH axle spacing of the hub slightly in some cases. This driver will also fit several different NIG type SA 5s hubs too. You will also need the HMW147 lockwasher for the RH cone. [NB I recommend this is fitted to all SA hubs that lack it anyway; however with the HSA800 fitted, it is mandatory.]

The standard driver for a pre-NIG AW hub has longer splines than the standard NIG driver as fitted to SRF3 etc. This means that a pre NIG AW can be fitted with two standard sprockets (even 1/8") with no other adaptations. I do however recommend a (longer) replacement axle of the new (solid) sort in most cases. Note that one or both sprockets need to be dished and that (depending on who made them and which way round they are fitted) 3/32" sprockets may or may not present to be 1/8" thickness on the driver relative to one another because they have a joggle in them.

cheers

[hoogerbooger]

Thank you.

Interesting.I think I'll get one of those AW's from sjs then and see if I can fettle it appropriately. Getting/making the right cogs might be fun though. The old sram Brompton 3 spline 3/32 cogs are like gold dust to find now,but I have some.

The longer axles HSA 621 is just 2mm longer. Is the main reason to change it the strength ? Can you explain.

[Brucey]

you can make (arguably better) 3/32" sprockets (which are suitable to fit to a pre-NIG AW) by simply grinding the sides of 1/8" ones. The SRAM 3/32" sprockets for Bromptons also had (to aid shifting) one or two reprofiled teeth; again you can easily replicate this with a little grinding, albeit it does prevent the sprocket from being turned and used a second time.

Do not buy HSA621 if you are planning to install it in a pre-NIG hub; it won't fit. It is meant to go in a NIG hub.

For a pre-NIG AW hub you want HSA107 or HSA370. You can tell easily if a SA axle is meant for pre NIG or NIG types; even if they look about the same the distance from the end of the slot to the sun pinion is quite different.

The reason for changing the axle in a pre-NIG hub is that the replacement parts are inherently stronger, being 'all solid' rather than having a riveted sun pinion. That said, in a Brompton the axle loads are not usually very high and even in a large wheeled bike the original AW axle type usually lasts for years before it gives any trouble; only the use of a schlumpf drive is ringing any big alarm bells here and if it is the 'speed drive' the torque loads on the rear hub axle ought to be less not more.

cheers

[Brucey]

BTW if you want to experiment without building wheels, the pre-NIG AW internal ought to fit inside an SRF3 shell.

cheers

[hoogerbooger]

Many thanks for the advice.

Sounds well worth a try. I have a built up BWR on a shelf doing nothing, so I can see if it'll swap into that shell/wheel.

If I do that I'll need to install an oil port ( could test it initially without though). I have drills, taps, nylon M5 screws that I could use( although will have to consider how best to drill it in a made up wheel . If I can't work it out I'll take it apart and rebuild after)............................but am wondering how the original AW plastic ports are attached and whether I can transfer it over from the steel shell. Are they threaded in or a push fit ?

[Brucey]

For a long time the lube ports were plastic and screwed into the hubshell. I'll see if I can find a suitable photo.

However please note that it is possible to lube these hubs very easily by unscrewing the control rod (having first selected top gear and turned the pedals to ensure that the sliding clutch has settled fully leftwards) and injecting suitable lube down the hollow axle. Not only is this very swift (using the appropriate syringe/grease gun) but arguably the lube is more likely to end up where it is really needed, right in the heart of the mechanism. I use a rather runny semi-fluid grease in my hubs but gear oil works this way too.

cheers

[Brucey]

oil port, as used on the AW hub etc from ~1960 until the mid 1980s. Do check but I think that the thread might be M6 or very close to that; close enough that the plastic part will screw into an M6 hole and be snug, anyway, IIRC.


I'm a little teapot....

This part appears to have gone NLA from most of the usual stockists but I think it still crops up on e-bay from time to time as NOS stashes etc are discovered. Do check but the part number is HSA106, I think.

cheers