Working With Cable for Elevator

[DonRotolo]

Bearings are always a good idea, since friction will be a major factor.

We once made our own aluminum pulleys.

[RRLedford]

For our FTC robot this year, and with the expanded range of allowed materials, we decided to use the 80/20 liner motion slide bearing options.
Pictured below is our two stage lift using 600 lb test kevlar core, braided polyester covered cord. It is thin yet strong and can handle sharp radius pulleys.

We used shoulder screws with 8mm OD shoulder and 6mm thread to mount our pulleys both in the frame slots and on the slide plates.

We made our aluminum pulleys on the lathe and pressed them onto cheap roller skate bearings of the "mini" size having 8mm IDs by 19mm ODs (Skate bearing types: micro-16mm OD, mini-19mm OD, std. 22mm OD). You can also Locktite the pulleys onto the bearing ODs.

For an even smaller pulley, you can also forgo bearings and just use the shoulder screw as a precision ground axle and have the aluminum pulley spin right on it, with just a little lubrication, but the pulley bore must still be a nice slip fit to work well.

We really liked the infinitely variable positioning that the shoulder screw on slotted framing gave us. You have to use a washer against the slot and the end of the shoulder to have proper grip on the frame, and you can use a larger ID washer fitting on the shoulder OD to handle the spacing & location of the pulley along the shoulder length.

The cord end anchor point was also a shoulder screw without a pulley, and just a small bowline knotted loop captured by the head of the shoulder screw.



-Dick Ledford

[Kusha]

Originally Posted by RRLedford

For our FTC robot this year, and with the expanded range of allowed materials, we decided to use the 80/20 liner motion slide bearing options.
Pictured below is our two stage lift using 600 lb test kevlar core with braided polyester covered cord. It is thin yet strong and can handle sharp radius pulleys.

We used shoulder screws with 8mm OD shoulder and 6mm thread to mount our pulleys both in the frame slots and on the slide plates.

We made our aluminum pulleys on the lathe and pressed them onto cheap roller skate bearings of the "mini" size having 8mm IDs by 19mm ODs (Skate bearing types: micro-16mm ID, mini-19mm OD, std. 22mm OD). You can also Locktite the pulleys onto the bearing ODs.

For an even smaller pulleu, you can also forgo bearings and just use the shoulder screw as an precision ground axle and have the aluminum pulley spin right on it, with just a little lubrication, but the pulley bore must still be a nice slip fit to work well.

We really liked the infinitely variable positioning that the shoulder screw on slotted framing gave us. You have to use a washer against the slot and the end of the shoulder to have proper grip on the frame, and you can use a larger ID washer fitting on the shoulder OD to handle the spacing & location of the pulley along the shoulder length.

The cord end anchor pointwas also a shoulder screw without a pulley, and just a small bowline knotted loop captured by the head of the shoulder screw.



-Dick Ledford

We used the same concept for our linear lift in 2011.

[StealthMentor]

1802 used pulleys with bearings for our cable powered lift that we re-purposed from replacement sliding patio door rollers (they were cheap and worked very well). Bought them at lowes for something like 3$ a pair.