Chief Delphi - Elevator vs. Telescope vs. Scissor

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Chief Delphi (http://www.chiefdelphi.com/forums/index.php)

- Technical Discussion (http://www.chiefdelphi.com/forums/forumdisplay.php?f=22)

- - Elevator vs. Telescope vs. Scissor (http://www.chiefdelphi.com/forums/showthread.php?t=55337)

kaszeta

08-03-2007 13:14

Re: Elevator vs. Telescope vs. Scissor

None of the above. Team 95's robot has two joints on it's arm, one for side-to-side and one for up-and-down rotation:

(well, it has a third joint at the wrist, but that's just for folding the arm on itself when the bot's in starting configuration).

Samuel H.

10-03-2007 00:23

Re: Elevator vs. Telescope vs. Scissor

Quote:

Originally Posted by Tom Line (Post 593256)

Any of you forklift styles used a motor that heavy?

We use the Big CIM for our winch. Strangely, before we added surgical tubing counterweights to or elevator stages we managed to burn up both the Victor and the CIM. Now that we have the required force decreased, we have not had any problems though.

Good luck,
Sam

MrForbes

10-03-2007 00:35

Re: Elevator vs. Telescope vs. Scissor

Quote:

Originally Posted by Tom Line (Post 593256)

An arm style lifting system requires extremely power motors / gearing because of the torque of an arm at full extension. It has more momentum that is very difficult to damp and control, and has difficultly stopping at given heights unless you have very powerful motors.

I guess that depends on how you design the arm. With help supporting it, such as a gas spring, it requires relatively little power to move it, and you can get away with a light duty motor/trans (suchs as the small banebots or globe). The control can be handled with two pots, one on the arm and one on the OI, with a bit of programming to conrol the rate of movement. Seems to work real well for 1726 so far.

ballgame21

10-03-2007 07:26

Re: Elevator vs. Telescope vs. Scissor

We had an elevator that was powered by a pully to save weight. It seemed to work really well.

It doesn't really matter what type you have when two bots are playing defense on you.

http://youtube.com/watch?v=oepTWtPj5Yk
(Think Pink):cool:

Dominicano0519

10-03-2007 11:46

Re: Elevator vs. Telescope vs. Scissor

we have a jointed arm that is also telescopic, The whole thing can pan and tilt. so can the jointed forearm

1359th Scalawag

10-03-2007 21:18

Re: Elevator vs. Telescope vs. Scissor

Our robot has a telescoping arm. We have absolutely no motors in the hand (grasping) mechanism. We just scoop up the tube. It's possibly the most simple hand you can have.

I voted telescope arm because we have one but if I had to choose the best kind of arm, i'd say the Elevator (forklift) type did the best. They just come down on top of the spider leg and let gravity put the tube where it belongs. They seemed the most reliable to me.

artdutra04

10-03-2007 22:51

Re: Elevator vs. Telescope vs. Scissor

I've never really been much of a fan of telescoping arms: for me it's either an elevator, an arm, or a combination of the two. The biggest problem I have with telescoping arms is that the longer they extend, the harder it becomes to score with them if defense is being played upon you. With a telescoping arm sticking out six feet, a 10degree spin due to defense will offset your manipulator much more than a short two or three foot arm with the same 10degree spin from defense.

This year, 228 has a two-stage elevator (powered by a single big CIM running through an AM single-speed tranny) with a short rotating arm located on the second stage. The arm is designed to pick up tubes from the floor, drive with them almost completely within our robot frame dimensions (which would drastically increase the difficulty of knocking it out of our manipulator). And if you can figure out why we designed the arm to rotate off to the side, then mad props to you. Otherwise, you'll have to wait until UTC. :p

Joe Johnson

11-03-2007 17:03

Re: Elevator vs. Telescope vs. Scissor

I would have been in the elevator camp until I saw a bit of the Great Lakes Regional competition this weekend.

Proir to this weekend, I was in the elevator camp. Easy control is a key and, while an elevator is not a requirement for easy control, it does make the job much easier.

But, I have now switched my thoughts to say that in many cases a jointed arm is an big advantage (it still has to be well behaved). Specifically, it can enable a robot to reach over an opponent. There were many matches where the HOT Team (#67) or the MechWarriors (#573)* were blocked from getting to the spider leg by another robot, only to reach OVER their opponent and score.

I am convinced. A well behaved jointed arm with the reach to score over an opponent is definitely the way to go this year.

Joe J.
*Full Disclosure. This is my daughters team and they did quite well at the GLR so I am far from unbiased. In my defense, I will say that I had very little to do with their robot design.

MrForbes

11-03-2007 17:13

Re: Elevator vs. Telescope vs. Scissor

Jointed arms dominated in Arizona, although that may be because most of the scoring robots had jointed arms.

842 had a simple lower row Swamp Thing type manipulator that worked well until the PVC broke in the finals. 1158 had a turret mounted telescoping arm that was pretty effective, although it's ability to move all around did seem to cause some problems with hanging up in the rack. The jointed arm bots seem to move tubes quickly, and that's really important this year.

Also, the more joints you have in the arm, the more challenging it is to control....and 39 definitely met that challenge!

obsesswthneesan

13-03-2007 22:28

Re: Elevator vs. Telescope vs. Scissor

1 Attachment(s)

Quote:

Originally Posted by Joe Johnson (Post 591886)

I have thought about scissor lifts a lot. They seem easy but in fact are quite difficult to implement successfully on FIRST robots. I was toying with the idea of lobbying FIRST to make a rule against them, but I think I have come up with another, better approach.

I think that FIRST should make a rule that explicitly allows scissor lifts but that requires that every scissor lift should have a clown head on top. The size of the clown head is dictated by the following formula:
Min Diameter of Clown Head = {Number of stages in the scissor Lift - (Number of Years Your teams has been involved in FIRST/4) } X 1ft.

Clown heads would be like bumpers in that they can extend beyond the normal limits of the robot, the associated weight is not counted during weigh in, and other robots can bash into it any time they like without pentalty.

While this rule is likely to be controversial, it would be extremely entertaining and I think that it help more people to see the difficulties of actually implementing scissor lift that is not laughable.

Joe J.

P.S. Heavy sarcasm alert.

[sarcasm]perhaps there could be a big spring with a plate attached to the top and bottom with a wench in between controlling the hight of the spring and retracting it. This would be far better than a scissor lift because it could move far faster and have a nice springy effect when it is impacted by another robot[/sarcasm]

hayakuneko

13-03-2007 22:39

Re: Elevator vs. Telescope vs. Scissor

at the LA regional, I really liked the cheesypoofs/rawc bot design with the hooks and the elevator design, however what I found to be quite helpful was our arm design. With our arm design, we successfully capped mid-level spider legs over a few robots. In quarter-finals, we capped over 1702 (i think) and right as we were trying to cap over them, they even had one of their alliance partners come push us to stop us from scoring, but we still scored. Also in the finals round, we went up against 330/254/4 and with our arm, we were able to squeeze our arm in the little space in between the empty spiderleg and 330's arm. hehe that was a great match.

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