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40 hole sturmey archer hub into a 24 x 2.125 wheel

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40 hole sturmey archer hub into a 24 x 2.125 wheel

Old 10-21-14, 04:31 AM
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trnkami1978
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40 hole sturmey archer hub into a 24 x 2.125 wheel

I'm new here I joined this site to see if there's anyone that can help me figure out how to spoke my 40 hole sturmey archer three speed drum brake AB hub into a 24" x 2.125 rim. I tried to read the sheldon article on alternate spokeing patterns and am not really understanding what I need to do. What kind of rims do I need to find 24,28, 32 hole,or is 36 possible? I have no idea 24 and 28 doesn't seem enough. 32 all I could find is horse cart wheels. 36 I thought I read 18 different sized spokes. What would be best? And what would be the best pattern for a drum brake? And how do I calculate the spoke lengths? I'm in over my head.
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Old 10-21-14, 05:32 AM
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A "best pattern" is tricky. An OK pattern is easy. Whenever it's a hub that has to carry torque, you want a (somewhat)tangential(crossed) spoke pattern.
High flange hub, 4X is out. Even 3X might be tricky. So you're looking at 2X or even 1X. I've done mismatched builds, and they can be a right pain.
36 from 40, I'd probably try for an 1X and simply chance to use spoke lengths for a regular 36/36 build. Might need 4-8 spokes of a different length.
Or I'd make myself some adapter rings.
3 mm aluminium sheet metal, inner edge overlaps the hub flanges and attach through the spoke holes. Outer edge protrudes enough to allow for new spoke holes to be drilled with the correct spacing and hole count to match the rims.

There MIGHT be a 40-to-whatever combo that'll work out symmetrically, but I've haven't found any easy way to determine that.
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Old 10-21-14, 08:08 AM
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Originally Posted by dabac View Post
There MIGHT be a 40-to-whatever combo that'll work out symmetrically, but I've haven't found any easy way to determine that.
And the smaller the rim diameter, the trickier it becomes...
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Old 10-21-14, 08:19 AM
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The Bike friday folks figured out the Math to do the skip hole lacing patterns, I wont.

Note: You can buy a Hubshell as a spare part for Sturmey Archer regular hubs ,with 36 and 28 holes

my English Made S-A drum brake hubs are 36 hole, 3 cross . [in 26" rims]

Last edited by fietsbob; 10-21-14 at 08:23 AM.
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Old 10-21-14, 08:24 AM
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It will be very difficult to lace a 40-spoke hub onto anything other than a 40-spoke rim, unfortunately. There are ways it can be done, but you'll have mismatched spoke lengths spoke tensions, possibly with quite a lot of variation. Not exactly conducive to a durable wheel.

I'm fairly sure the standard lacing pattern for the old Raleigh Sports with its 40-spoke rear wheel and rear Sturmey-Archer dynohub (which has the same flange dimensions as an SA drum brake hub on the left-hand side) is 3X on that side of the wheel, with a rim which is some flavour of 26". As such, you'll most likely be doing 2X with the smaller rim.

As for spoke lengths, there are a number of spoke calculators online that'll do it for you given hub and rim dimensions, but as far as I know they're only any good for hubs and spokes with the same number of holes.

Or, you could get hold of a 36-spoke modern Sturmey-Archer hub shell, which the internals from your old one (including the brake) ought to fit into. Or, in the same vein, you could get an old 36-hole shell on eBay or something.

As a curveball idea, have you considered other sizes of rims? There are some sizes that are fairly close to the size you're asking about(within about 20mm diameter), and as you're using a drum brake, the exact location of the rim relative to the frame isn't a huge issue, so you can use a slightly different diameter rim. There might be 40-spoke rims more readily available in one of those sizes. There's a handy article explaining sizes here here.
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Old 10-21-14, 09:13 AM
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Trigonometry, son, trigonometry! I laced up a 40-hole SA hub to a 36 hole rim, and it took 4 sets of 9 different lengths of spoke (2x, 406 rim, no dish). They were 1 mm different in length. A 32 hole rim will be easier with 8 sets of 4 different lengths. With the drum brake you may need different lengths on each side, so take that into consideration.

The process is:
Draw it all out on a piece of paper. Make sure the missing holes on the opposite flanges are exactly divided from each other. Calculate the length of each spoke as if the wheel were flat. Adjust the length of the spoke by the offset distance of the hub flange.
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Old 10-21-14, 12:05 PM
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OP - Today, I'm from Missouri. Unlike the others, I am suspect your old AB drum brake internals will transfer into a modern Sturmey hub shell. Claims compatible hubshells are available aftermarket are also met with skepticism until a source is provided.

How important is it to you to reuse this old AB hub in a modern application? Because new 36 hole Sturmey XRD3 drum brake hub kits with beautiful alloy shells and the improved NIG mechanism are available and not that expensive.
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Old 10-21-14, 05:26 PM
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Originally Posted by tcs View Post
OP - Today, I'm from Missouri. Unlike the others, I am suspect your old AB drum brake internals will transfer into a modern Sturmey hub shell. Claims compatible hubshells are available aftermarket are also met with skepticism until a source is provided.
I've actually put the innards from an old (and I mean seriously old, it had a threaded driver, meaning it's from sometime in the '50s at the latest) SA drum brake hub into a modern XRD-3 shell. It can be done. That's the advantage with SA hubs, the forward compatibility is great!
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Old 10-21-14, 05:54 PM
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Go on ebay, sell the 40 hole hub, buy the type you want. You might lose money on the sale but lacing and truing might be easier and the wheel will look better unless you want an unusual spoke pattern.

Why replace the internals? You might be stuck with a 40 hole hub shell if no one happens to want one. I don't think those go bad. People who have bikes with old 40 hole rear wheels probably won't need a new shell.
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Old 10-21-14, 07:42 PM
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Originally Posted by Airburst View Post
I've actually put the innards from an old (and I mean seriously old, it had a threaded driver, meaning it's from sometime in the '50s at the latest) SA drum brake hub into a modern XRD-3 shell. It can be done.
You know that not all AW hubs will interchange shells, right?
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Old 10-22-14, 03:02 AM
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Originally Posted by tcs View Post
You know that not all AW hubs will interchange shells, right?
Which ones don't? I've put new-style NIG internals into an old shell from the mid '70s with no trouble, as well as the aforementioned swap going the other way.


Originally Posted by garage sale GT View Post

Why replace the internals? You might be stuck with a 40 hole hub shell if no one happens to want one. I don't think those go bad. People who have bikes with old 40 hole rear wheels probably won't need a new shell.
Weirdly, last time I went on eBay UK looking for an SA hub, I found a lot of auctions for hub shells, maybe one for every two or three complete hubs. I have no idea why people buy or sell them, but they do.

A new 36h shell for an X-RD3 or AB3 was about 15 last time I scrolled past one on SJS cycles' website, and a modern X-RD3 (or AB3 if you want a steel shell) is about 90.
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Old 10-22-14, 11:39 AM
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Here's the trigonometry, with Spoke #1 calculated in terms of ERD, HFD and HFO. There are 4 distinct spoke lengths for 40 hole to 32 hole rim if the flanges are the same diameter and offset. There are 8 if the flanges are different. It's not too hard. The other flange is the mirror image, rotated 45 degrees.
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