On-line Gear Calculator for Internally-Geared Hubs
This article show how to determine the correct length of a Sturmey-Archer indicator spindle by measuring the axle and the position of the toggle key which shifts the hub. Read this article in connection with our main article about indicator spindles.
The effective length of an indicator spindle is from the base of the threads to the shoulder before the first link of chain (between the points of the green arrow in the image below).
Most newer hubs need a thinner indicator spindle, like the one iin the image below. These spindles have a painted mark, which may be on the rod, or on the chain. The red arrow in the image indicates the length from the base of the threads to the mark. No matter where the mark is, the length which affects compatibility is from the base of the threads to the shoulder, same as with the thicker rod, as indicated by the green arrow.
In the image below, the blue arrow shows what I call the solid-axle length and the orange arrow shows what I call the toggle-key depth (KD) -- measured to the rightmost extent of the toggle key, not to the flats. For clarity, the drawing shows the planet cage in place, but the measurement can also be taken without the planet cage. Just make sure that the clutch assembly is pushed as far onto the axle as it will go. The parts shown are from a classic AW 3-speed, but the principle is the same for other hubs.
The toggle-key depth can be measured with the hub completely assembled, by inserting a 13-gauge bicycle spoke into the end of the axle and measuring the insertion depth. A fatter rod could be used with a hub that uses a thick indicator spindle, but don't use a thinner spoke: it could pass through the threaded hole in the toggle key.
The solid-axle depth can be measured only on the bare axle.
In older 3-speed hubs which accept the AW style fat rods, the correct (shoulder to shoulder) length is 'L' where
L = 'solid-axle length' + 5.7mm and
L = 'toggle-key depth - 7.7mm
In most newer, no-intermediate gear 3-speed hubs (not CS-series and not S3X)
L = solid-axle length' + 9mm
L= 'toggle-key depth - 7mm '
'solid-axle length' = the length from the RH end of the axle
slot to the RH end of the axle (measure on a bare axle) and
'toggle-key depth' = depth of toggle key when hub is set in the top gear (slackest control cable),
measured from axle end e.g., using vernier calipers.
The correct single toggle 5-speed control rod length appears to be given by;
L= KD-14mm (for dog locking sprinters and (W) hubs) and
L= KD-15mm (for ball-locking sprinters)
KD values for ball locking hubs are also less than dog lockers by about 4mm; thus similar-looking ball locking hubs require shorter
control rods than dog-locking ones, by about 5mm. Ball-locking 5-speed internals may be identified by a chamfer on the left end of the axle.
As noted, we don't have calculations for CS-series (hybrid-gearing) and S3X (fixed-gear) hubs, though our other article does identify and give lengths for indicator spindlesfor these hubs. Some newer hubs use rotary shifting: the cable rotates a pulley concentric with the axle, next to the sprocket.. These do not use an indicator spindle.
|Three-Speed Parts from Harris Cyclery|
|English Three Speeds, Care and Feeding|
|Sturmey-Archer Hubs, General Information|
|Sturmey-Archer 1935-38 Catalogues|
|Evolution of the Raleigh Sports|
Sheldon's old Robin Hood
|Martin Hanczyc's roadster pages.|
Tony Hadland's Sturmey-Archer Pages
including the 1956 master catalogue with
rebuilding information for SWs and others.
|Sturmey-Archer documents at the Veteran Cycle Club Library.|
|Hubstripping web site|
|John Allen's spreadsheets of internal-hub gear ratios|
|SW Hubs by Brian Hayes|
Jane Thomas's site with
Sturmey-Archer service manuals.
Menotomy Vintage Bicycles
Chat forum on English bikes.
Last Updated: by John Allen