Silent ring drive hub internals that could be the next Dura-Ace shown in a Shimano patent
27th Jan 2016 | NEWS
Rumors and hearsay have been out and one deep digging have been made by one of the world’s largest cycling tech blog site that Shimano has been working on an all-new hub designs that could offer quick engagement, more durable freehub bodies and nearly silent, drag-free coasting. And few patents have been found to back the rumor up.
The biggest update in Shimano’s current drive design is the switch to a ring drive ratchet system. DT Swiss have already proven this with their Star Ratchet, but Shimano’s filling was actually attributes Chris Kings ring drive pattent but with a major difference in the way that Shimano’s design moves the ratchet rings. And that very difference is what eliminates the buzzing bee sound during coasting, creating a silent, fast hub that might just be the soul of XTR and Dura-Ace’s next generation hubs.
It is known that Shimano’s current hub design used a ratchet and pawl system, clicking small, spring-loaded teeth on the free hub into a ratchet ring seated on the hubs shell which is an improvement from an earlier design used in a lower and mid STX model back in the 90’s, where in the ratchets and pawls were all housed in a replaceable freehub body which were prone to contamination but not rebuildable, and with the smaller overall diameter required to fit it all inside the FH body, things just weren’t as good.
The new design which were heard to be called Scylence, replace pawls by two ratcheted rings and a conically section on the freehub body.
DT’s Star Ratchet uses two toothed rings, one in the hubshell and one in the FH body. Each is spring loaded to push against each other, and the teeth are angled such that when you pedal, they mesh together and turn the wheel. When coasting, the teeth’s angles are like ramps and the teeth simply bounce over each as the springs twitch in micro compression behind them. Because the teeth are always touching, you get the clicking noise. And because there are so many teeth, especially on Chris King’s hubs, that noise can be high pitched and high volume. DT offers three different tooth counts on their rings, which make more or less noise depending. Higher tooth counts mean quicker engagement, but also more noise and more potential drag.
Shimano’s patent flick the script, slightly. And it’s brilliant. Only one of the ratchet rings (31) is spring loaded, but the spring (34) is pulling it away from the second ratchet ring (32), back towards the hub shell (16).
Inside the sprung ratchet ring (31) are slanted grooves (54/58) that catch the grooves (42/44) on the FH body (30). When you pedal, the FH body (30) spins and those grooves pull the sprung ratchet ring (31) into the floating ratchet ring (32) and the teeth connect and drive the hub shell, thus rotating the wheel and propelling you forward.
When not pedaling, those same grooves push the sprung ratchet ring (31) away from the floating ratchet ring (32), and the spring (34) assists in retracting and holding it, keeping the teeth from making any contact. That eliminates drag and clicking sound.
The floating ratchet ring (32) glides freely over the angled grooves on the FH body, but has splines (64) that fit into slots (18d). When it’s driven by the sprung ratchet ring, the wheel is turned.
So, rather than push two toothed rings together, Shimano has found a way of pulling one set of teeth into the other, then retracting it while coasting. Patent drawings are typically not 100% represents the final product, but if those tooth counts are remotely close to real, expect a very quick engagement when pedaling.
From the looks of it, the sprung ratchet ring (31) won’t be moving much to contact the floating ring (32). All those moving parts are covered by a seal (36), and bearings are in their usual places – widely set with cup-and-cone adjustment on the outer balls. The arrows simply refer to the direction that the sprung ratchet ring moves when pedaling (D1, in order to contact the floating ring) and coasting (D2).