Converting a Sturmey FW 4 speed to an S5 5 Speed

[Mark Stonich]

I've added info about converting a Sturmey FW 4 speed to an S5 5 Speed to my "Sturmey Archer Tips" file.

http://bikesmithdesign.com/SA/SA-Tips.doc

and http://bikesmithdesign.com/SA/SA-Tips.pdf

I believe Paul McLette has done similar conversions to either the FB (4 spd. drum brake) or the FG (4 spd. DunoHub).  Maybe both.

Up in the frozen north he must have plenty of time to tinker while waiting for the spring thaw.

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Converting a Sturmey FW 4 speed to an S5 5 Speed

Why?
It's fairly easy to find an FW without it's delicate 2 piece indicator rods.  Indicator rods, when they are on Ebay bring steep prices.  The high cable tensions in bottom gear are tough on 4 speed triggers and the triggers themselves are not cheap or all that common.  S5 is IMHO a simpler, more robust unit, And the added high gear allows you to run a larger rear cog and still have a gear suitable for those rare tailwinds.

What Do You Need?
AW or FW trigger, AW axle key and indicator. Left side shifter, cable, and cable stops or guides as needed.  To be authentic, you would use a 2nd pulley and a fulcrum clip.  It's  best to use a friction shifter for the left, whether thumb, stem, downtube or bar-end.

Bellcrank;
If you are using a friction shifter for the left side you can use a common Shimano bellcrank that has been bored out and retapped to 134/32" x 26 TPI.  I am equipped to do this.  If you will be using Sturmey Archer shifters on both sides, you will need a Genuine Sturmey Bellcrank to get the correct leverage ratios.  I have a few, both NOS and used.

You will get more reliable shifting into the wide range if you put a spring on the bellcrank. Like so;  http://bikesmithdesign.com/SA/bellcrank-spring.jpg

Pushrod:
Sturmey made many versions of the S5 pushrod but I always prefer a modified nail because you can fine tune the length.  I recently scored a complete NOS S5 kit, from the last year of production, on Ebay.  The pushrod is just a very nicely made nail. 

Now the rare bits;  (Of which I have a few)
HSA 269 - S5 Primary Sun Pinion $12.00
http://bikesmithdesign.com/SA/S5andFWsuns.jpg
The FW sun is on the axle.  As one side of the dogs are ramped, it will only transmit power in one direction.

And you may need HMW 149 - Lockwasher for Dog-Ring. This washer is keyed to the axle.  You can usually reuse the original one once.  $2.00

-- 

  
Mark Stonich;  
  BikeSmith Design & Fabrication
    5349 Elliot Ave S. Minneapolis, Minnesota 55417 USA
       Ph. (612) 824-2372   http://bikesmithdesign.com

[Paul McLeete]

Nice review of this almost mythical conversion Mark. An important
point you make is that, less the iffy indicator springs, a five speed
setup is mechanically more positive. Cleaner shifts and less truama
for certain parts. I'd feel much better sending my sweetheart off to
circumnavigate Lake Pepin with a 5 speed.

I did spend time puttsing with 4 speed Dyno-Hubs last winter. Sucess
at making Five G's came out of the effort. I'm very happy with the
one installed in my bike. Finland MN is hilly and dark at night.
Extra gears and headlight are handy when being chased by moose. A
search of this group site under 'FG hub' should produce my 1/29/10
list of pro's and con's and I'm sticking to it.

Since writing that I have gone back into the hubs I converted and made
a modification that pertains to FW's. I discovered a slight bend in
the Low Gear Key. This small part has a hole drilled thru it for the
old indicator rod. Thats a weak point right where the push-rod now
forces sun gears to shift against a spring. Now I leave the original
key out and install a stainless piece w/no hole but a shallow flat for
the rod to push on. The new keys include the radius at the ends
matching axle diameter for best contact with the pinion sleave.

This winter I've more FG's to convert but just can't bring myself to
open another friends hub without a proper tool to loosen and tighten
the Ball Ring. No matter how nice I keep the cold chisel, it always
leaves a mark. A proto-type tool is almost ready.

Paul McLeete
Finland MN

On Jan 11, 8:33 am, Mark Stonich <m...@bikesmithdesign.com> wrote:
> I've added info about converting a Sturmey FW 4 speed to an S5 5
> Speed to my "Sturmey Archer Tips" file.http://bikesmithdesign.com/SA/SA-Tips.doc

> andhttp://bikesmithdesign.com/SA/SA-Tips.pdf

> HSA 269 - S5 Primary Sun Pinion $12.00http://bikesmithdesign.com/SA/S5andFWsuns.jpg

[Rob Riggins]

Paul, do you plan to offer the tool for sale? It sounds like a great idea -- probably not a money maker, but the people on this list might be interested.

Rob Riggins
Minneapolis, MN

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[Syke]

Definitely interested in one of those tools if offered for sale.  I seem to be doing more and more SA work in the shop lately.
 

Syke
Montpelier, Virginia

It's amazing what you can accomplish when you're too stupid to realize that you can't do it.

---

From: Rob Riggins <rigt...@gmail.com>
To: gentlema...@googlegroups.com
Sent: Wed, January 12, 2011 10:48:05 AM
Subject: Re: [Gentleman Cyclist] Re: Converting a Sturmey FW 4 speed to an S5 5 Speed

[Paul McLeete]

I'm encouraged that there is an interest in such an esoteric effort.
I do plan to make a small batch to lend and sell, so I'll be happy
offer them. I've yet to try the first one (might get a chance
tonight) and already have changes in mind. A proper tool is a
wonderful thing to use and I must be sure this is that. It may take
untill spring.

Paul McLeete
Finland Minnesota

On Jan 12, 10:21 am, Syke <sykeroc...@yahoo.com> wrote:
> Definitely interested in one of those tools if offered for sale.  I seem to be
> doing more and more SA work in the shop lately.
>  Syke
> Montpelier, Virginia
>
> It's amazing what you can accomplish when you're too stupid to realize that you
> can't do it.
>
> ________________________________

> From: Rob Riggins <rigten...@gmail.com>