I had to repair a machine today that uses a static reel to counter balance a slide
assembly that has a rotary encoder on a spring reel to measure displacement.

Looked like 1/8" cable over a 1.5" pulley that the cable wrapped 90 degrees. Just looked
wrong and the cable lasted 3 months. The cable is very lightly loaded, is there a ratio
of wire size and diameter to use in making the right sized pulley?

Thanks,

Wes

Wes wrote:

I had to repair a machine today that uses a static reel to counter balance a slide
assembly that has a rotary encoder on a spring reel to measure displacement.

Looked like 1/8" cable over a 1.5" pulley that the cable wrapped 90 degrees. Just looked
wrong and the cable lasted 3 months. The cable is very lightly loaded, is there a ratio
of wire size and diameter to use in making the right sized pulley?

Thanks,

Wes



There are minimum recommended diameters of the pulley for every size and
type of cable, aircraft cable being the most flexible and requiring the
smallest diameter pulley for a certain diameter cable. Also, the
alignment of the pulley is critical to reduce rubbing of the cable on
the side of the pulley. Worn shafts or bad bearings will decrease the
life of the cable.



http://www.dir.ca.gov/Title8/8497.html


John

john wrote:

There are minimum recommended diameters of the pulley for every size and
type of cable, aircraft cable being the most flexible and requiring the
smallest diameter pulley for a certain diameter cable. Also, the
alignment of the pulley is critical to reduce rubbing of the cable on
the side of the pulley. Worn shafts or bad bearings will decrease the
life of the cable.


Thanks John,

I was hoping you would be up on the channel when I got home since I was sure you knew the
answer given your past occupation.

Wes

On Mon, 08 Dec 2008 17:19:07 -0500, Wes wrote:

I had to repair a machine today that uses a static reel to counter balance a slide
assembly that has a rotary encoder on a spring reel to measure displacement.

Looked like 1/8" cable over a 1.5" pulley that the cable wrapped 90 degrees. Just looked
wrong and the cable lasted 3 months. The cable is very lightly loaded, is there a ratio
of wire size and diameter to use in making the right sized pulley?

Thanks,

Wes


Hey Wes,

The sheave diameter should be a minimum 20 times the cable diameter,
which would be a 2-1/2" pulley. While the load has a major effect,
the bending radius is what causes most wear if there is no other
negative influence, such as improper groove size which is very
important too, or incorrect fleet angle(s).

Brian Lawson,
Bothwell, Ontario.