Elevator/Telescopic Arms & Motors to Use

[Daniel_LaFleur]

Originally Posted by Ravage457

Hello Chief Delphi Communty

Im Back for more wisdom from the FRC and CD community
Ive been intrested in knowing what is the most simple arm to build, an elevator or telescopic arm and how to prevent it from over extending, another question is do yall use Bearings in the arms to allow it to travel free?

The best arm is the one your team has the capability of building. If you don't know how to do it, prototype first.

To prevent overextending you can:
put in hard stops (don't stall your motors !!)
Put in an encoder (use software to stop the travel)
Put in limit switches (can be used for software stops or hardware -Jags- stops)

Using bearings is, usually, preferrable.

Originally Posted by Ravage457

Also, how do yall run the pnuematics and electrionc wires in this type of arms and keep them from getting pinched or ripped apart

Create a travel conduit with a looped back wire/tube set. Use rubber bands / surgical tubing to retract the excess wire when the arm retracts.

Originally Posted by Ravage457

What motors are also good to use with this arms?
If you have any pictures it greatly appreciated. I know im probably asking alot, but i really want to improve my knowledge and better and to improve our team. Thanks again for taking your time, and giving me yall advice and recommendations

Any motor will move an arm with the proper gear reduction. What you need to ask yourself is 'how long do I want it to take to extend/retract the arm under worst case conditions' and size the motor accordingly. You may want to look at assisting the motor in a particular direction (gas shock?) if the load in 1 direction is far more than in the reverse direction.

[Peter Matteson]

My team has been around since 1995 and we have done quite a bit of refining and improving the basic design of the telescoping arm in that time. Our eveolutionary changes reflect the KOP changes that have taken place over time as well as rule changes.

1996: 177 introduces the first telescoping arm on the Hexorcist. It was a monocoque sheetmetal construction with the "inner arm" being stationary and attached to the shoulder. The outer arm glides over the inner arm on custom linear slides made from HDPE. The slides start out at the top and bottom of the arm and move closer together as the arm extends. The extension is driven by window tape, a plastic that appears like the edge of a piece of film. The shoulder was powered by a van door motor driving a 45 chain sprocket on a solid steel axle. This was a high shoulder robot using the super structure to create a reduction with chain to drive the shoulder.

1997: Same as 96.

1998: Same as 96 & 97 but we also created the roller claw that year, in parallel to 45.
http://www.chiefdelphi.com/media/photos/13367
http://www.chiefdelphi.com/media/photos/22601

1999: Same as 96-98 but we had the Gerber Grabber as an end effector.

2001: The first year we went from monocoque construction to 1/8" wall Al box for easier manufacture. We also had 2 van door motors on the shoulder, a globe powered extension (first year I know what motor we used), and a globe powered wrist. The total arm extended around 13 feet. First year we used #35 chain to drive the shoulder. This arm was also a low shoulder designed to swing either direction and go under barriers.
http://www.chiefdelphi.com/media/photos/12342
http://www.chiefdelphi.com/media/photos/12339
http://www.chiefdelphi.com/media/photos/12347
http://www.chiefdelphi.com/media/photos/12558

2003: A copy of 2001 but with a a CIM powered shoulder and a COTS gearbox, this was the first year we could purchase this type of item.
http://www.chiefdelphi.com/media/photos/15124
http://www.chiefdelphi.com/media/photos/14983

2005: Same as 2001 & 2003 but a high shoulder and with a COTS automotive winch gearbox powered by to FPs.

2007: The first year expansion rules were in place which caused us to go with a vertical extension instead of extendeing the arm. We changed the slide material to delrin for the first time. We ditched the window tape for extension because it no longer in the kit and used #25 chain. The extension was a banebots motor and so was the shoulder which was a COTS worm drive gearbox.
http://www.chiefdelphi.com/media/photos/28221
http://www.chiefdelphi.com/media/photos/28222

2008: We reversed which part of the arm was stationary and which part moved by making the outer arm stationary. We also went to a hollow, large OD tube of 4130 for the shoulder to save weight and improve strength.
http://www.chiefdelphi.com/media/photos/30533

2011: 1st year we counterbalanced the arm with a gas spring. We went to a pnuematic extension.
http://www.chiefdelphi.com/media/photos/37064

And just because I found it in my photo search some CD notables as students...
http://www.chiefdelphi.com/media/photos/12112

[Gary Dillard]

Great synopsis Peter. I always figured that team 178 would feel tremendous pressure to demonstrate a flawless telescoping arm (since they're sponsored by UTC sister division Otis Elevators); it looks like you've done pretty well yourself.

[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.

[Peter Matteson]

Originally Posted by Gary Dillard

Great synopsis Peter. I always figured that team 178 would feel tremendous pressure to demonstrate a flawless telescoping arm (since they're sponsored by UTC sister division Otis Elevators); it looks like you've done pretty well yourself.

Surprisingly, while 178 is sponsored by Otis, during the time I've known people on the team they've never had a mentor from Otis.