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-   -   Question for the Sturmey Archer Gurus: can I convert a 4-sp to a 3-sp? (https://www.bikeforums.net/classic-vintage/702210-question-sturmey-archer-gurus-can-i-convert-4-sp-3-sp.html)

rhm 12-19-10 09:21 PM

Question for the Sturmey Archer Gurus: can I convert a 4-sp to a 3-sp?
 
Okay, I don't know how to do it, but I know you can convert a four speed hub such as an FW (wide-range four speed hub) or the FG (wide range four speed hub with dynamo) to a five speed like an S5.

I know the advantage of the four - speed hub is that it works with one shifter, but the disadvantage is that that shifter is getting hard to find and wears out prematurely. I also know the disadvantage of the five speed hub is that it requires two shifters and may require parts, such as a bell crank, that are hard to find.

So, my question, is can you take a four speed hub and convert it to an ultra-wide range three speed hub? So you'd end up with a hub that has the 1, 3 and 5 gears of the five speed hub, but needs only one shifter-- the garden variety three-speed trigger?

Don't tell me I wouldn't like that, because the gears would be too widely spaced. This may be true; but that's not what I'm asking. I only want to know if it's possible. If it is possible, I'd probably run that hub with two cogs, spaced 4 teeth apart, so I'd have an ultra-wide range six-speed system.

So, esteemed Sturmey Archer gurus... what do you think?

sailorbenjamin 12-19-10 09:47 PM

If you've got a 4 speed shifter, measure the clicks, then measure again on a 3 speed shifter, or I'll measure mine and we can compare.

balindamood 12-19-10 09:55 PM

Easy way: Block-out the shifting rod through the axle
Harder way: Get a three-speed shifter so you are only using 3 speeds (your choice, upper or lower 3)
Hardest way: pull the hub apart and monkey around...maybe take out one set of planetary gears perhaps.

Not sure it is worth the trouble.

tcs 12-20-10 06:31 AM


Originally Posted by rhm (Post 11957008)
Don't tell me I wouldn't like that, because the gears would be too widely spaced. This may be true; but that's not what I'm asking. I only want to know if it's possible. If it is possible, I'd probably run that hub with two cogs, spaced 4 teeth apart, so I'd have an ultra-wide range six-speed system.

Current production SunRace Sturmey-Archer super-colossal-wide-range 3-speed, 0.625, 1.0, 1.60; 9-spline driver for two cogs.

tcs 12-20-10 06:44 AM


Originally Posted by rhm (Post 11957008)
So, my question, is can you take a four speed hub and convert it to an ultra-wide range three speed hub?

Off the top of my head, you'd want to lock the 30T secondary sun gear and let the primary 24T sun gear spin free.

rhm 12-20-10 02:35 PM


Originally Posted by tcs (Post 11957852)
Off the top of my head, you'd want to lock the 30T secondary sun gear and let the primary 24T sun gear spin free.

Yes, that sounds exactly right. But I think I'd also have to change the part that the indicator threads into, since the 3 and 4 speed hubs take different indicators. But, at any rate, you think it can be done? Any idea where I can find instructions how to do this?

If I first do a complete teardown and rebuild of an AW, then of an FW, and maybe also of an S-5, will I learn what I need to do this conversion?

tcs 12-20-10 05:21 PM


Originally Posted by rhm (Post 11960030)
But, at any rate, you think it can be done?

I can't think of a reason it couldn't be done, which is not quite the same thing!

Here's the theory.

dedhed 12-20-10 06:13 PM

You've probably already found this.
http://www.users.globalnet.co.uk/~ha...samaintind.htm

I'm under the impression that s5/2 guts fit in an AW shell.

wahoonc 12-20-10 06:42 PM

From what I gather the conversion from 4 to 5 speed is very straight forward and you can use a Shimano 3 speed bell crank assembly on the left side. Shoot an email to Mark Stonich at BikeSmith Design, if he can't come up with an answer no one can.

Edit: I would want more gears and range not less...

Aaron :)

bikamper 12-20-10 08:19 PM

I've converted an FW to a fixed gear 3 speed and it was fairly straight forward but ended up with a narrow range hub. I've discussed what you are thinking with Mark Stonich a couple years ago but as I'm suffering from Old Timers at the moment I can't recall how it went. But as Aaron said, if mark can't come up with it, no one can.


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