Elevator/Telescopic Arms & Motors to Use

[roystur44]

For Logomotion we built a two stage timing belt elevator that was fast and had sub inch accuracy on the set points. We started with one Fisher Price motor but added a second one when we re-geared the transmission to make it scary fast. I was surprised to see how easy the elevator was to build and how reliable it was through the season. Rivet construction. External fan cooled motors, Jag speed controllers. The timing belt was the key to our elevator. We didn't need a counter spring to lower. We caught a peg in a match and the elevator lifted our 140 lbs bot no problem. FYI don't use the KOP limit switches use a industrial strength limit switches to prevent the over travel.

Here is how 971 ran their bearings on the elevator.

https://picasaweb.google.com/1177698...19391120770786

https://picasaweb.google.com/1177698...19146623548482

We used Igus cable carriers to do the cable management

https://picasaweb.google.com/1177698...19493903585554


More pictures here:

https://picasaweb.google.com/1177698...39115326022594

http://www.youtube.com/watch?v=3jm_yPl83gs

[Jon Stratis]

We've built 2 elevators in out teams history.

The first, for Overdrive, was continuous:
- A single cable ran up, down, up, and back down to pull both moving stages up. This results in the innermost stage moving first, then the second stage moving.
- We ran the cables through Igus chain to keep everything organized. This still created a loop sticking out the back of the robot while the elevator was in motion.

The second, for Logomotion, was cascade:
- There were two cables - one from the motor, up over the fixed stage and down to the bottom of the second stage, and one from the fixed stage over the second stage and down to the innermost stage. This results in the motor lifting the second stage, which also lifts the first stage - both stages move at the same time.
- With this design, we ran the wires up the fixed stage to a pulley at the top of the second stage, then down to the innermost stage. Since the two stages moved in concert, as the elevator moved up, the distance between the top of the second stage and the innermost stage decreased at the same rate the difference between the the fixed stage and the top of the second stage increased - in other words, the distance from start to finish, through the pulley, stayed the same. The wires remained straight without going overly loose or tight. It completely avoided having a loop out the back of the robot that other robots could get tangled on.

I've also seen teams utilize wire loops - they attach one end of a tape measure to the base of the robot, and the other end to their elevator, then loop the wire around the tape measure. As the elevator goes up, the tape measure extends to follow it, and the wire loops get smaller.