Sachs Torpedo 3-speed H3111
Some photos of the subjectively best 3-speed hub ever made.The series of hubs - also known as Sachs Torpedo Dreigang/3-gang model H31xx, Spectro 3, SRAM T3 - was produced in different (but compatible) versions from around year 1977 and well into the 2000s.
Diagram with measurements for wheel building and fitting into a frame. The long axle version is also compatible with contemporary wider frames up to around 130 mm if spacers are added.
The first revision of the hub shell have no pressed-in recesses on the outer surface (the inner ratchet teeth was formed solely by machining) and therefore has a cleaner look compared to the later revisions (see next photo).
The later revision had one set of the internal ratchet teeth partially formed by pressing in recesses, probably to reduce production time and cost. There is no mechanical difference in how the two different teeth profiles perform when riding a bike.
Later in the production the chrome surface plating was replaced by a satin finish galvanization and the outer profile of the hub shell was changed a bit (but still compatible with all former and later revisions).
The final revision of the hub saw the biggest changes to the hub shell, with a switch to a "tube" construction with pressed-on stamped sheet metal flanges to further reduce machining time and material use (less metal is wasted when the flanges are not formed/turned from a larger-diameter metal stock). Although the internal mechanics are still as good as the original revision, this hub shell is a step down.
A view of the internal ratchet teeth on a version of the hub shell with the pressed recesses:
An internal unit from a late-revision hub, ready to be installed in a hub shell:
An internal unit from a late-revision hub, disassembled. Note that the coupling plate has four tabs (and corresponding four coupling points in the planet cage). This is different than the earlier revisions' six tabs. The change to four tabs was to make space for the asymmetric coupling ramps on the planet cage, enabling a "brake booster" function that makes the hub downshift from third gear when braking, giving the effect of having higher braking effect leverage than otherwise.
Remember to install the brake cone friction spring in the correct orientation (as seen from the left side of the hub) and grease the groove it sits in. It provides a different amount of resistance to rotation when turned one or the other way, so installing it incorrectly will cause increased drag and wear.
There is also a rare version (model H3102) of the hub without a coaster brake:
Only a few parts are different:
Page last updated 2024-03-28 16:10. Some rights reserved (CC by 3.0)