Capstan/wippen heel intersection

[David Ilvedson]

Yeah, I was just telling that to my wife this evening...;-]

David I.

> Just a quick response to a line in Richard Brekne's post:
>
> > From a friction standpoint, and I believe from a leverage
> standpoint.. the
> > capstan /cushion should act as nearly like to a pivot as is possible.
>
> The intersection is less like to pivots than gear or cam action. In
> order for one to drive the other the respective vectors of velocity
> _commonly tangent to the capstan and heel at the points of contact_ are
> equal in magnitude and direction; however, their motion is angular and
> the _actual_ instantaneous velocities are perpendicular to the lines
> from these points to the respective action centers. The difference
> between the pairs of actual velocities is the instantaneous velocity of
> sliding between the profiles, and which should be smallest around the
> line between the two centers. An interesting note, though:
>
> > The energy lost in friction at the teeth [action part contact profiles]
> > and at the bearings is...less during recess [above the line between
> > centers] than during approach [below it]...During approach the
> teeth [parts],
> > while sliding on each other, are pushing into mesh, while during recess
> > they are drawing out of mesh. Gears [actions] would therefore be more
> > efficient and durable if the action were confined to recess.
>
> 	p236. Albert, C.D. & F.S. Rogers. "Kinematics of Machinery"
>
> The path of the point of contact is a function of the profiles of the
> parts, compounded a little in this case by nonlinearities of heel
> padding and compression over time (oh, and the deformation of keys under
> load); for one, involute profiles have been favored for gear teeth
> because they can tolerate changing geometry. Anyways, a more efficient
> action also is a more durable action.
>
> Regards,
>
>
> Clark
>