Sturmey archer 4 speed fm hub.

[rjb]

Can you remove the innards from a Sturmey Archer 1953 4 speed fm hub in an alloy shell and transplant into a steel aw shell? The fm is a 40 hole and i wish to put it in a 36 spoked wheel. If it is possible what else do i need to consider.

[Mick F]

Can't help specifically.

I wanted a modern 3sp that would take a 10sp cassette.
http://www.sturmey-archer.com/en/produc ... rf3-silver
They produce them in 28h but sadly not import them into Europe in anything other than 36h ............... and I wanted 28h.

I have an old 28h 3sp SA AW so removed the internals in the hope that I could fit the new internals into it before I had to buy a new 36h rim.
Sadly, the internal LH profile wouldn't fit, also the LH freewheel ratchet had too few teeth, so a new rim was required.

I suspect that 4sp internals won't fit in a 3sp shell .................... but I'm willing to be corrected.

[robc02]

Can you remove the innards from a Sturmey Archer 1953 4 speed fm hub in an alloy shell and transplant into a steel aw shell? The fm is a 40 hole and i wish to put it in a 36 spoked wheel. If it is possible what else do i need to consider.

No, unless it's an old shell with a threaded ball cup and you replace the AW one with an FM one. The difference between them can be seen here:

https://hadland.files.wordpress.com/2012/07/safm.pdf
https://hadland.files.wordpress.com/2012/07/saaw.pdf

The later type AW has a pressed in ball cup:

https://hadland.files.wordpress.com/2012/07/saaw.pdf

[Brucey]

the 40h shells build most easily onto a 32h rim, using two spoke lengths. I have also posted details of how to build a 36h rim onto a 40h hub and it is a lot more complicated. Quite possible though, if you are suitably methodical.

BTW alloy SA hubshells from the 1950s are not that strong; if you plan to give this wheel some real treatment I'd suggest a steel shell.

Another part that is 'not that strong' in an FM or FC gear is the low gear ratchet in the LH side of the hubshell. There is more than one version, and I think it is important with any of them (some more than others) to make sure that it is well supported by the hubshell, so that it doesn't crack (which is a real problem with this hub design). I think suitable adhesive bonding of parts that don't fit that well is a good idea.

cheers

[robc02]

the 40h shells build most easily onto a 32h rim, using two spoke lengths. I have also posted details of how to build a 36h rim onto a 40h hub and it is a lot more complicated. Quite possible though, if you are suitably methodical.

I've done both, but I wouldn't use a 36 hole again without a good reason! 32 on a 40 hub is quite straightforward though.

As Brucey says, the old alloy hubs are not that strong, so I would thoroughly clean and have a good look at the flanges before using it. Having said that I have had an FM in a 1951 alloy shell in regular use on my foul weather (mud, grit salt etc.) commuting bike for several years. It has had to be re-rimmed (maybe twice) due to pothole damage, but the old shell has taken the punishment so far.

Of the three types of ball cup the earlier one is often reckoned to be the least suspect, but I have managed to crack one. Some suggest that they survive better in a steel shell, but this must depend on the closeness of fit between the ball ring ratchet and hub shell. I am sure that bonding would be an improvement. (I've only been planning to do this myself for ten years or so! - One day, maybe.)

[rjb]

Thanks guy's - not as easy I first thought. Local bike recycling scheme have a refurbished 4 speed sturmey bike for sale. When did they change to a steel shell? I noticed on fleabay that the 4 speed dynohubs have steel shells but presume these are not the FM ratios.

[Brucey]

alloy shells were an option for some years

FG hubs have the same ratios as FW hubs

cheers

[jimlews]

robc02 said,

No, unless it's an old shell with a threaded ball cup and you replace the AW one with an FM one. The difference between them can be seen here:



The later type AW has a pressed in ball cup:



I don't think you can do that.
Looking at the exploded drawings that you link to it is evident that the low gear ratchet track is further inboard in the FM hub than in the AW. It is the crenelated extension of the L/H ball cup; and therein lies the weakness of the FM, for the tips of the low gear pawls rest on the the inside of the alloy shell 'and had a tendency... to burst through the alloy shell. This had alarming results for both gear and rider'. (Tony Hadland-The Sturmey Archer story)

From the same source, I think you would have to obtain a FC shell which is probably rarer than an FM. In any event, a steel shell is likely to be more robust

[robc02]

robc02 said,

No, unless it's an old shell with a threaded ball cup and you replace the AW one with an FM one. The difference between them can be seen here:



The later type AW has a pressed in ball cup:



I don't think you can do that.
Looking at the exploded drawings that you link to it is evident that the low gear ratchet track is further inboard in the FM hub than in the AW. It is the crenelated extension of the L/H ball cup; and therein lies the weakness of the FM, for the tips of the low gear pawls rest on the the inside of the alloy shell 'and had a tendency... to burst through the alloy shell. This had alarming results for both gear and rider'. (Tony Hadland-The Sturmey Archer story)

From the same source, I think you would have to obtain a FC shell which is probably rarer than an FM. In any event, a steel shell is likely to be more robust

That's right. The FM innards will only work with an FM ball cup. So they can be used in any shell where the ball cup is screwed in and can therefore be replaced, but not in the later AW shells with a pressed in ball cup. Sorry if this wasn't clear in my earlier post.

[Brucey]

BTW it isn't just the position of the low gear ratchet that is different; in FM and FC gears the LH hub endpiece also contains a ring gear, of course.

cheers

[robc02]

BTW it isn't just the position of the low gear ratchet that is different; in FM and FC gears the LH hub endpiece also contains a ring gear, of course.

cheers

Yes, and here is one I broke earlier :
SAFMBallCup by SturmeyRob, on Flickr

Incidentally, in my previous post I should have said "FM innards will only work with an FM type ball cup", as the FM and FC share the same part:
https://hadland.files.wordpress.com/2012/07/safc.pdf

I have never had an FC hub to take apart, but as far as I am aware the FM and FC shells are the same apart from their markings. Looking at the diagrams, the difference between the two hubs is down to different primary sun and planet pinions and planet cage.

[Brucey]

BTW it isn't just the position of the low gear ratchet that is different; in FM and FC gears the LH hub endpiece also contains a ring gear, of course.

cheers

I have never had an FC hub to take apart, but as far as I am aware the FM and FC shells are the same apart from their markings. Looking at the diagrams, the difference between the two hubs is down to different primary sun and planet pinions and planet cage.

yup that is about it.

Looking at your picture it seems that if the ratchet ring had been a closely toleranced fit in the hubshell, it would have been nigh-on impossible for it to have broken in the same way. It occurs to me that if a steel shell were built up with weld metal internally, then machined, such a fit could be attained.

cheers

[robc02]

Looking at your picture it seems that if the ratchet ring had been a closely toleranced fit in the hubshell, it would have been nigh-on impossible for it to have broken in the same way. It occurs to me that if a steel shell were built up with weld metal internally, then machined, such a fit could be attained.

I should point out that the fit of the ball ring in the (alloy) shell was better than the damaged might suggest - still not as close as would be ideal (obviously, otherwise it probably wouldn't have broken!). I removed the ball ring to check for a breakage following slipping under load. All that I could see was a line I thought might be a hairline crack. To check it I gripped the suspected portion with pliers and gently levered - that is why the cracked segment is misaligned so much.

Incidentally, replacing the ball cup with a good one didn't cure the slipping, so it was obviously still supported well enough by the shell to take moderate loads. Given the scarcity of these items I have wondered about refitting it and bonding it into a steel shell - but maybe this would be tempting providence a bit much.

I did fix the slipping but can't quite remember which bits I changed.

[jimlews]

Ahh! My apologies.

I had forgot that the shells are interchangeable.

A case of post in haste and repent at leisure.

[mjc43]

I have a 1950 FM hub that was jammed with crud (off a "barn find") and after cleaning it up I'm doubtful whether its going to work because there is so much play in the three secondary planet pinion gears that they jam. Doesn't look like the pinions have worn so it must be the gears themselves. I can't find replacements anywhere (K816A x 3). Any idea where I might get replacements?

A second question, assuming I get three replacement pinion gears and the gubbins works ok, the idea of putting it into a steel AW shell sounds good. However the ball cup K817 is so tight in the shell I can't see how to get it out without damaging something in the process. Apart from soaking for ages in penetrating oil, any ideas?

Thanks, Mike