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Re: Convert Sturmey FM to 5 speed?

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  • Anwar Rahim
    Thanks for all the replies. There is a lot of excellent info, I had feared that this may have been lost to history!!! Bob, thanks for the pointer with the
    Message 1 of 11 , Jun 26, 2013
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      Thanks for all the replies. There is a lot of excellent info, I had feared that this may have been lost to history!!!

      Bob, thanks for the pointer with the reference and instructions, and Jim super work with finding a copy of the magazine! I have already ordered a copy. Seen that the VCC has a copy of Tony Hadland's The Sturmey Archer Story and I may get this too.

      Michael Wilson, many thanks for the instructions. This is really great. I had ordered the magazine before your post but as I'm the type to read instructions twice/thrice (four times!!) before doing anything I'm very glad for both accounts. I will be looking into sourcing the parts straight away. The way you describe it, it does not sound too difficult but having said that I'm a relative 'amateur' when it comes to IGH so will be taking things slow and reading the instructions meticulously! I believe I have the steel shell FM hub so hope to avoid breaking ball cups... I may take you up on the bellcrank, though will send a PM if I do. I will be overhauling this hub in about two weeks time and will hope to get the mod done at the same time.

      The next challenge will be to get this 40 hole hub into a 32 (or 36) hole rim!

      Ian, good to see you on this list too! Had spent some good time yesterday afternoon reading those posts on the Moulton forum about the FW conversion. I also have one of these hubs (from a Series 2 f-frame) and had considered doing that instead but preferred to see if an FM mod was possible. I wasn't sure if they would be the same. I understood that the FW conversion works by having a wide 3 speed and narrow 3 speed, both sharing the same direct drive (middle gear) hence giving 5 ratios. However, looking at the differences between the FM ratios and the FM 5spd conversion it didn't think it would work in the same way. From Michael's description it doesn't sound too dissimilar. And from Stanley's description (though it may be a converted FW...) it sounds like that the three middle gears are unaffected and controlled by the original shifter and the left shifter pulls the first and fifth gear...

      Thanks again to all for your informative replies. I will update the list with how progress goes and will post my own write up with details. (Fingers and toes crossed I don't hit (too) many bumps on the way!)

      Kind regards

      Anwar







      --- In Geared_hub_bikes@yahoogroups.com, "bikealfa" <mtwils@...> wrote:
      >
      > How to do it (as a side note, I believe Stanley converted an FW not an FM, because an FM does not need the sun pinion replacement):
      >
      > Remove the 4 speed indicator setup. Don't throw it away; it is not easy to get a new one. You want AW/S5 right side indicator, including the part into which the indicator screws (and I am not looking up the part number despite the fact that it is only a minute from here). (The 4 speed and AC are different; the indicator is not threaded into this part). You use a pushrod and bellcrank on the left. I was going to use the sheet metal bellcrank as the axle washer, rather than the cast bellcrank. Mark Stonich has a method of converting Shimano bellcranks, and there may be other bellcrank options. You will probably want to use a custom-cut nail for the pushrod, because as best as I can remember all the S5 bellcrank hubs had 6 or 6 1/4 axles, not the 5 3/4 FM/FC/ASC axle, and I believe that was always longer on the left side.
      >
      > I may have bellcranks if needed ...
      >
      > The one I saw was a Bicycle Exchange Cambridge employee's bike.
      >
      > Michael Wilson
      >
      > --- In Geared_hub_bikes@yahoogroups.com, "bikealfa" <mtwils@> wrote:
      > >
      > > I have seen an FM converted to a 5 speed. I have not done it myself.
      > >
      > > Issues:
      > > The FM axle is short, so there is not much room for the left axle nut and the bellcrank. Use the "sheet metal" bellcrank rather than the later cast one?
      > >
      > > I had problems with my FM left ball cups breaking; Mark Stonich claims that the steel hub shell mitigates this.
      > >
      > > The overall range is no different than an S5 of the same era, and that is a much easier thing to do. So I switched to the S5 that was in my parts bin (this was around 1985) and that worked for 10 or 15 years, and I think still works today. Yes the ratios are closer at the edges of the range and wider in the middle, which is not ideal, but the simplicity of build, and the fact that I had run out of FM ball cups to replace the broken ones, far outweighed that.
      > >
      > >
      > > Michael Wilson
      > >
      > > --- In Geared_hub_bikes@yahoogroups.com, jim <jimbofla1138@> wrote:
      > > >
      > > > >>makes reference to Jack Lauterwasser, “Four into Five”, Cycletouring, April/May 1970, pg. 47 for instructions.
      > > >  
      > > > Tilley's Vintage Magazines has a copy of that issue for sale (provided it's the same magazine Bob Edwards is referring to:"Cycletouring, the C.T.C. Gazette") for sale for 7 pounds. Or, perhaps your libraries might have an archive?  Fun places them archives...
      > > >  
      > > > http://www.tilleysvintagemagazines.com/source/product_data.php?prodid=22699
      > > >
      > > > If you do locate the details please share them with the group, I for one would be most interested in seeing how that upgrade is accomplished in such a tightly engineered space as an IGH.
      > > >  
      > > >  
      > > > jim / so fla.
      > > >
      > > >
      > > > ________________________________
      > > > From: "emgee73@" <emgee73@>
      > > > To: "Geared_hub_bikes@yahoogroups.com" <Geared_hub_bikes@yahoogroups.com>
      > > > Sent: Tuesday, June 25, 2013 3:32 PM
      > > > Subject: Re: [Geared_hub_bikes] Convert Sturmey FM to 5 speed?
      > > >
      > > >
      > > >  
      > > >
      > > > In Tony Hadland’s “The Sturmey Archer Story”,  Appendix B, he makes reference to Jack Lauterwasser, “Four into Five”, Cycletouring, April/May 1970, pg. 47 for instructions.
      > > >
      > > > Bob Edwards
      > > >
      > > >
      > > > Sent from Windows Mail
      > > >
      > > > From: Anwar Rahim
      > > > Sent: ‎Tuesday‎, ‎June‎ ‎25‎, ‎2013 ‎12‎:‎33‎ ‎PM
      > > > To: Geared_hub_bikes@yahoogroups.com
      > > >  
      > > > Hi,
      > > >
      > > > Is this possible?
      > > >
      > > > I was looking at Sheldon's gear calculator http://sheldonbrown.com/gears/internal.html and in the drop down menu it has an option for 'Sturmey-Archer 5-speed (FM modified)'!
      > > >
      > > > Looking at the ratios it looks like this modification adds an extra gear at the top. It's quite a jump between the top two gears (1.13 to 1.5), which I don't think is an ideal combination but I currently have a FM hub which I plan to build on to a wheel this summer and having this extra gear will increase the range enough on this medium ratio hub so that I can use it for fast day rides and with a change of the chainring (and chain) I can use it for touring (at a pinch). This would be useful as I hope to build a touring bike sometime in the future but in the meantime this mod will save me having to build another wheel until that time comes (which will be a while yet)
      > > >
      > > > I've had a good look on the internet with the help of google but I can't find anything. Nothing at all! Does anyone know anything about the conversion and how to do it?
      > > >
      > > > Many thanks
      > > >
      > > > Anwar
      > > >
      > >
      >
    • David Bean
      Isn t the theory of operation for the FM the same as the FW? (To get the 5th high gear would require a bellcrank on the left end of the axle to push the
      Message 2 of 11 , Jun 26, 2013
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        Isn't the theory of operation for the FM the same as the FW? (To get the
        5th high gear would require a bellcrank on the left end of the axle to push
        the indicator back into the hub) Therefore the new high gear would be the
        complement of the sub-low first gear. You'd still have the 3 fairly close
        ratio gears but a super-high top gear. It would make for some funny ratios.
        Tell us about it if you do it.

        David Bean
        Arlington, MA USA
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