Re: spindle to motor connection

Hoyt,

I guess none of us has seen it all...

I am not talking about old leather flat belt drive machinery. I am
referring to more modern spindle drive techniques(tho' still "old")
using flat belts.

I can assure you that the long pulley is NOT crowned, and also not
usually flanged, either. The shorter pulley is BOTH crowned and
flanged. The reason for the crown is the same as always, to self
center the belt. The reason for the flanges is that the z axis motion
can be too quick for the crown action to "keep up". The flanges keep
the belt on the smaller pulley, and move it down or up the cylinder
pulley. when the relative axial movement between the two stops, the
crown again does its job.

FWIW, even on the older flat belts, often only one pulley was
crowned. Look at some lathe drives, the spindle pulleys are flat, and
the drivers behind or above them are crowned. Lots of examples on
Tonys Lathe UK site.

Otherwise the crowns would "fight" as the uneveness of the belt went
over them. Double crowned pulleys were used when the distance
between them necessitatied the self-centering action at BOTH ends.

But back to CNC, and the original posters question: Look at engraving
machines from the 40's and forward, gorton for ex., and you will see
what I have described, AS I have described it...

This technique was used for fractional to a few HP.

Ballendo


--- In CAD_CAM_EDM_DRO@yahoogroups.com, Hoyt McKagen <bjammin@i...>
wrote:

> At 12:47 PM 1/23/03 -0000, you wrote:
> >There were a few machines that used flat belts (nowadays they'd be
> >urethane, or some such). One pulley of the spindle motor pair has

a

> >width which just accomodates the belt, with flanges on both ends.

It

> >will also have a heavy crown in the center,which serves to keep

the

> >belt centered on IT. The other is a straight right cylinder, of a
> >diameter to effect the desired ratio betweeen the two; and long
> >enough to accomodate the desired spindle travel.
>
> Not only have I seldom if ever seen flanged pulleys for flat belts,

I have

> never seen a flat belt pully that wasn't crowned. The crown is both
> necessary and sufficient.
>
>
> Regards, Hoyt McKagen