Adapting 3-spline cogs to 12-spline driver, or vice versa


bertin753
 

I've been told by someone who has done it that it's not that hard to trim the 3 splines on modern SA cogs to fit the square and shallower splines on the 12-spline drivers on TF and TC hubs.

[I think this 12-spline driver is K 657 and I think it was used for all sports hubs in from the late 1930s to 1951, per one of Hadland's SA charts? Please correct if wrong!]

At any rate, back to the main question: Can one do the opposite, that is, grind 3 of the 12 splines on a TF driver (K 657?) to accept the taller and rounded splines of modern SA cogs?

I daresay that the drivers are made from hardened steel, but then so are cogs, right?

Any answers, advice, counsel, opinions, thoughts, conjectures, instructions, photos, and warnings welcome (if well founded, of course).

Thanks.

Patrick "next question about a QR (quick-on/quick-off) shifting system for the TF and TC to follow eventually" Moore

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Patrick Moore
Alburquerque, Nuevo Mexico, Etats Unis d'Amerique, Orbis Terrarum


Michael Wilson
 

Modifying the rare expensive discontinued noLongerAvailable part and not the common commodity item seems wrong, despite the fact that it is usually better to make the system take wear replacement items with no extra work.

If you are doing the work yourself by hand, modifying the 3 spline sprockets for the 12 spline driver will be a lot better because if you make a mistake you just get another sprocket.  It is true that the 12 spline sprocket will still work on the remaining 9 splines so maybe not so bad.  Modifying the driver for 3 splines also requires the reverse thread to get dimpled.  I use cutoff wheels for all my hand grinding, and I do not know about buying a grinder bit for a dremel that has the desired OD to match the 3 spline curve.   Grinder bits also wear very fast so the OD changes.

If you have a machine shop you trust, talk to them.  noMadic Thomas had a Sturmey Archer driver modified to accept a Shimano cassette lockring, and maybe that machine shop will talk to you about what you want

Either way you have the issue of lash if the driver or sprocket modification is not good enough.

I keep thinking that changing the chainring to match the available 12 spline sprockets is an easier solution. 



Thomas
 

In principle, I agree and endorse Michael Wilson's comment (especially chainring sizing) about which side of things to modify   ...    but I have done both to great satisfaction  =)

I have modified several 12-spline shimano cogs to fit 3-spline drivers...    I used an airtool with a cylindrical carbide bit, I believe this would/could work for extending/modifying the slots on the drivers..   and does not wear-down all that fast...    I did not get them exact, but close enough to work on a free-wheeling hub...     remember to track the placements of the 12 tabs, which ones you choose to grind does make a difference as one is narrower...

I also (had) modified several 3-spline drivers...
    One was a Fitchel and Sachs dreigang that I had driver shoulder lathed back so there was room for more cogs, and also the 3 slots that the cog-tabs fit on...  The machine shop used a fancy tool for this, I could ask them the name, I forget what it was, but the description sounded like what you would do with a shovel to expand a hole in the ground...
This works fine for drivers that have enough room to support this.

   I also had modified 6 drivers from modern (12-spline) S.A. igh to accept a shimano lock-ring...  5 of them can now hold four (@ 9-speed-spaced) cogs each, and these were made from the brompton special wide driver that they used to hold 2 cogs each but with a lock-ring...    the 6th was from a standard driver that works on both the S.A.-3 AND the S.A.-5...   it now easily holds 2 cogs and might hold 3 (@ 11-speed-spacing), it is not near me at the moment top test that).

noMadic  Thomas

On 3/4/22 5:26 PM, Michael Wilson wrote:
Modifying the rare expensive discontinued No-Longer-Available part, and not the common commodity item, seems wrong, despite the fact that it is usually better to make the system take wear replacement items with no extra work.

If you are doing the work yourself by hand, modifying the 3 spline sprockets for the 12 spline driver will be a lot better because if you make a mistake you just get another sprocket.  It is true that the 12 spline sprocket will still work on the remaining 9 splines so maybe not so bad.  Modifying the driver for 3 splines also requires the reverse thread to get dimpled. I use cutoff wheels for all my hand grinding, and I do not know about buying a grinder bit for a dremel that has the desired OD to match the 3 spline curve.   Grinder bits also wear very fast so the OD changes.

If you have a machine shop you trust, talk to them. noMadic Thomas had a Sturmey Archer driver modified to accept a Shimano cassette lockring, and maybe that machine shop will talk to you about what you want

Either way you have the issue of lash if the driver or sprocket modification is not good enough.

I keep thinking that changing the chainring to match the available 12 spline sprockets is an easier solution.


Michael Wilson
 

The modern Shimano HG is 9 spline, not 12 spline.  If it were 12 spline it would be easier to adapt to the 1935-1950 Sturmey Archer driver on the TF/TC etc hubs.  If someone knows of a 12 spline sprocket please tell us.  I have not looked at Campagnolo splines.

The S3X driver takes a reverse thread lockring but accepts the Shimano HG spline sprockets with the caveat that some other brands of BMX HG splined sprockets need a bit of grinding to enlarge either the minimum ID of the splines or the ID that goes over the main body, I forget which. 


bertin753
 

After a lot of thought about this, probably unnecessary, I have decided on 2 of the 3 following actions:

1. Have TF built for my 2020 Chauncey Matthews which usually sports one of the AM hubs. This had the advantage that the OL of this bike is 118 mm and that it has relatively thin plate dropouts (Chauncey cut these himself), and that I have three (3) 17 t 12-spline SA cogs to fit, which match the ring and wheels to give the requisite 72" gear. I only have 1 15t for the other bike.

2. Have the TF built for the other bike (Riv custom fixed gofast) and use the 15 t with a 1/8" chain, the do 4 below;

3. Have th TF built for the gofast and grind the 15 t cog down to 3/32 width (someone who has done this says it's relatively easy), while also doing 4 below:

4. Have a machine shop adjust a couple Shimano 12-spline ss 3/32 15 to cogs to fit the TF's 12-spline driver.

OTOH, someone who has also done it assures me it's not hard to trip the 3 splines of a modern 3/32 SA cog to fit the grooves on the TF driver; he's done it several times using a Dremel cutting wheel -- he advised against a Dremel grinding tip.

Fortunately, while I stew about this, the TC has been altered with a 3-spline driver.

Back to the Matthews with AM hub. I had that built for a primary fixed gear wheel, with the AM as an occasional wheel, since I'm no longer young, and hills that I once climbed in 70" or 7" fixed gears are now much too forbidding. But I fell in love with the AM and it's now the main wheel for this bike; the gaps are just right for me, my type of riding, and the terrain I ride in: 3-2-1 = 72-65-56. So much so that I guess that the TF would be wasted on this bike. I do have a wonderful old British steel fixed/fixed hub to be built up for this bike if I ever get nostalgic for fixed gear riding; must date from the 1950s at latest. Was 114 mm OL, but had it respaced to 118 mm. Heavy, but bearings are old Campy smooth.

On Fri, Mar 4, 2022 at 9:26 AM Michael Wilson <mtwils@...> wrote:
Modifying the rare expensive discontinued noLongerAvailable part and not the common commodity item seems wrong, despite the fact that it is usually better to make the system take wear replacement items with no extra work.

If you are doing the work yourself by hand, modifying the 3 spline sprockets for the 12 spline driver will be a lot better because if you make a mistake you just get another sprocket.  It is true that the 12 spline sprocket will still work on the remaining 9 splines so maybe not so bad.  Modifying the driver for 3 splines also requires the reverse thread to get dimpled.  I use cutoff wheels for all my hand grinding, and I do not know about buying a grinder bit for a dremel that has the desired OD to match the 3 spline curve.   Grinder bits also wear very fast so the OD changes.

If you have a machine shop you trust, talk to them.  noMadic Thomas had a Sturmey Archer driver modified to accept a Shimano cassette lockring, and maybe that machine shop will talk to you about what you want

Either way you have the issue of lash if the driver or sprocket modification is not good enough.

I keep thinking that changing the chainring to match the available 12 spline sprockets is an easier solution. 




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Patrick Moore
Alburquerque, Nuevo Mexico, Etats Unis d'Amerique, Orbis Terrarum


Thomas
 

uh, yes, my apologies, I was not near to thinking straight...

you are correct that the sprockets I ground tabs off of were 9-tab and are now 3-tab  ...

noMadic  Thomas, who is now about 3,300 miles from my bicycles and bicycle pieces and that is no excuse.
    if only I had stopped to remember or think ...     =|

On 3/5/22 6:06 PM, Michael Wilson wrote:
The modern Shimano HG is 9 spline, not 12 spline. If it were 12 spline it would be easier to adapt to the 1935-1950 Sturmey Archer driver on the TF/TC etc hubs.  If someone knows of a 12 spline sprocket please tell us.  I have not looked at Campagnolo splines.

The S3X driver takes a reverse thread lockring but accepts the Shimano HG spline sprockets with the caveat that some other brands of BMX HG splined sprockets need a bit of grinding to enlarge either the minimum ID of the splines or the ID that goes over the main body, I forget which.


Michael Wilson
 

I bought a Park chain gauge about 10 years ago.  Since then, with a minimum of 5k miles/year and 12k miles last year, I have worn out about 2 rear cogsets on my derailleur bikes total.  Before then I had to change rear cogsets almost every chain change.  

While it has been decades since I rode fixed daily, you may be able to do the same thing with the 12 spline Sturmey sprockets.  Change the chain when it gets to 0.5 wear.  Do not go beyond that.  Then keep riding.  Yes fixed gears have a lot more chain load if you ride them the way I did, with 200+rpm descents with the chain trying to ride off the tops of the sprocket teeth, pushing all the lubricant out of the bushings.  Which may mean a new chain every week, which might be excessive.

For the Chauncy Matthews I suggest that the TF would be better than a single speed fixed.  With 1 or 2 teeth smaller than the AM hub on it now, you could get a very similar gear range, but without the middle gear.

And for 2-4 years from now when 56 is no longer low enough to get up the hills, I like the S5.2.  Yes the ratios are wider, but not dramatically so between the top two gears.  If you make the top gear 72 inches then the feel between the top two gears will be similar to the AM.  And I do not find it feeling draggy and I like the brifter shifting.  Not that I ride it much.