From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Hugi Hub Design
Date: 16 Dec 1997 17:59:33 GMT

David Lozeau writes:

> What are the failings of the Hugi hub.  I missed the earlier discussion.

The hub addresses a perceived problem with an inappropriate mechanism.
The perceived problem is that the ratchet is the weakest part and
needs a stronger mechanism, something that is not true.  The mechanism
is a face ratchet composed of two radially saw-toothed plates, that
look something like two cutting tools face to face.  This is an
expensive and heavy ratchet.  As it skips over its engagements, the
whole plate snaps over to the next tooth, all 16 teeth at once.  The
moving steel plate slides on a peripheral teeth in the aluminum
housing.

The engagement of the face ratchet locks the two halves firmly
together under torque so that the axle flex makes the steel on
aluminum spline fret and wear.  Thus the perceived weak spot is
enormously reinforced while the real weak spot is the fretting
connection between the moving ratchet plate an the aluminum housing.
The movement from axle-flex at this interface is greater than it might
be, because the hub and freewheel are mounted separately on their own
bearings on the axle leaving a bending load in the center between hub
and freewheel.  This location is also not well protected from water
and dirt intrusion.

All that said, the noise of the face ratchet is annoyingly loud
although when new, the grease with which it is supplied masks that.
With a little use the ratchet cleans up and makes an audible clatter.

Jobst Brandt      <jbrandt@hpl.hp.com>