View Full Version : Help with pulleys and wire rope.

05-04-2006, 05:16 PM
I want to make a lat pull down maching for my power rack. Here is the one I have...
http://cgi.ebay.com/Powerline-by-Body-Solid-PPR200-Power-Rack_W0QQitemZ7239031375QQcategoryZ62135QQssPageNa meZWDVWQQrdZ1QQcmdZViewItem
You can see behind the rack they have that pull down machine, that is what I want to make. I found a pulley that is rated for 480LBS at a local hardware store, it is $15. From MC-Master CARR they have 1/8" nylon coated to 3/16" aircraft cable rated for 2,000LBS. I also have dumbbells like these...
I am going to take the rubber off so it is threaded all the way through. Then I will put a spin nut on one end and stack the plates vertically. I have some questions though.

-Will that pulley be strong enough? I know at 0* the pulley sees twice the weight (100lbs=200lbs stress on the pulley).
-How can I attach the aircraft cable? Use wire rope clamps? I was told I will need to strip off the nylon to use those and I don't know if they will be strong enough. I was thinking about using them to make a loop in the wire and then use a 660LB carabeaner for quick connections.
-How could I attach my dumbbell handle to the end of the rope?
-Any ideas on making a platform for the dumbbell handle and plates to sit on? I would want the platform to move up and down with the weights.


06-26-2006, 05:15 AM
I took a look at what you want to build. Fastening the cable ends shouldn't be that hard. I had a similar situation using a power winch connected to a static load of 600 lbs. through a single pulley. I used a standard 1/8th inch thimble and two pieces of 1/4 inch copper tubing. I wrapped the cable around the thimble then threaded the tubing around the live cable and the dead ends through the tubing then crimped them together using a #6 nest in a burndy crimper. I crimped twice on opposite sides a total of four crimps. With the load on it, the cables did not slip. I thought about using 1/8th inch crosby clamps but couldn't get the u-bolt tight enough.