After stringing and testing our skyscraper arm, we found that the stresses on the 3D printed parts were too great. They broke, even when printed using ABS. So, we did some more internet research and brainstorming to arrive at the conclusion that we needed to use metal connectors between the slides. Here are 9.25” long connectors made from Rev Robotics 15mm structure. The increase in length of the connectors – as compared to the slides alone – allows us to use only 5 slides to achieve a height of 50” when fully extended. 

Misumi slides mounted between Rev Robotics structure.
Lift with Actobotics pulleys and string, retracted.
Lift with Actobotics pulleys and string, extended.

Important info on this install for future reference.

– The slides were fastened to the connectors using low profile nuts installed into the grooves and secured with either 5mm or 6mm long socket head button screws. Either size works fine.

– We used M3 x 16mm hex head bolts and lock nuts to attach the Actobotics pulleys into the grooves of the Rev Robotics structure. These bolts are undersized but help reduce pulley friction because the pulleys have some give.

– We used 200# braided spectra bow fishing line to string the lift. This line is thin and non-stretch. Friction is minimal. It seems to work great.

– We used cascade rigging to increase lift speed. 

We used two Andy Mark 60:1 gear motors and a Duo Gearbox to power the lift.

SEE REVISION OF 02-10-2020.