Our team built two 4 staged telescoping arms in 2001 which could put the balls on top of the goals while the goals were on the ramp. Here are some pics
Practicing capping goals
Don't really need 4 stages
Oops ... the red one ended up on the floor
Kinda see how they work … best pic I could find
Under the bar
In the Easter spirit
Here are some of my memories of the arms that might help
-Globe motor was used to extend arms
-Surgical hose was used to "assist" the globe motor
-Window motor was used to lift arm (about 6" moment arm with 1" hub) … arm had to fit under bar
-Seat motor was used for turret
-Spectra string was used to "pull" things
-An Eagle Scout tied all of our knots … pretty frustrating when a knot lets go.
-First stage was pinned to turret
-Globe motor "pulled" second stage into place (up or down … did not depend on gravity)
-Third stage strings were attached to second stage ... not directly to motor
-Likewise, fourth stage was attached to third stage
-The cross section was a triangle with flat corners
-Delrin blocks (Teflon was cost prohibitive) were used as anti-friction blocks and "pulleys"
-The aluminum used for the arms was 0.032" sheet
-Bending the triangular sections is definitely an art but can be mastered with a good sheet metal break
Although the structure of the arm was very strong, the actuators were all fairly weak (using all of the strong ones on the base and balancing mechanism). This was okay because it was a 4 team alliance with no defense. This year, you need to have more powerful positioning actuators; thus, this year we are thinking about simply using our base to point the arm or go to a very strong turret.
All in all these arms performed very well even though our main strategy that year was to balance both of the goals. Telescoping is a good way to go and if you go this way, try to leave yourself a solid week to get out all of the kinks & binds.
Good luck,
Lucien