Re: Souces of Timing/Drive Pulleys

Chris & Peter:

I looked around for some information I know I have on the Fenner taper lock
hubs but haven't found it. I did, in desperation, find their web site at:

http://www.fennerdrives.com/

They have technical specs there. They list shaft tolerances of +- .0015
for the mini series and +-.003 for the standard. It sounds like the
surface finish shouldn't be polished, they mention "meduim grade emery
paper". The run out is listed at .001" TRI. They do move sideways when
tightening though, spec is some .075". This means to me you can't depend
on the fenner hub to keep axial force/alignment on the thrust bearing. My
steppers have a 3/8" shaft and these Fenner hubs, mini series, will take
250 in-lb or some 4000 oz-in.

They do put significant force on the shaft and pulley. I think for this
reason, and for plastic creep, they aren't recommended for non-metalic pulleys.

To me, they looked like the easiest way to obtain a true zero backlash
connection which can be dis-assembled.

Just FYI. Hope it is of some interest. :-)

Hugh Currin
Klamath Falls, OR

At 03:45 PM 5/19/01 -0400, Peter wrote:

> > I'm not familiar with these hubs, but would think that they would
> > require a very precisely machined (ground?) shaft (okay, I know, we're
> > _supposed_ to do that for the bearings anyway) and even then they
> > might still slip under high cutting or acceleration loads. If your
> > encoder is upstream of the pulley system, wouldn't some sort of pin be
> > safer?
> >
> > Chris
>
> Have played with those Fenner units too. They are very high dollar and
>work really well. If they are installed per spec, they should transmit any
>load the shaft is rated to carry. Since there is no keyway, I'd think that
>fatigue cracking is easier to avoid. The shafting need not be ground but it
>must be a good finish. Also, I think the diameter could be +- .001 in less
>critical applications. Sure beats cutting keyways.