Extension Mechanism

[acer_7]

Hi all,
Hope ur all fine . .

I wanna ask about something please. I wanna make an extending pipe consisting of 2 or 3 layers and I want to make it very simple and speed is not important. I am participating in a robot contest and this mechanism is very important for me, so i really need ur help.

How can i use a motor for that type of extension? I need an extension for about 6 or 7 meters.

Thanks in advance . .

[Billfred]

Do you mean more like this:

http://www.chiefdelphi.com/forums/sh...extension+lift

or more like this:

http://www.chiefdelphi.com/forums/at...achmentid=2834

The means for doing the two are somewhat different.

[Joe_Widen]

Ahh yes. Our team had something exactly like this. It was a cascading lift. It was in Billfred's second link on the left. What we did is we took 3 pipes and they cascaded. We used a CIM motor and the kop parts gearbox. Now it looks like you dont quite know what FIRST is. So here, you could by a CIM motor from < http://www.ifirobotics.com/first-store.shtml > its part number < FR801-001 >. Now buy gearing for a reduction of about 20:1 or 30:1. I recomend 3 stages. 2 through gearing and 1 through chain and sprocket. Now what we did is we went to a local sailing shop and bought sailboat pulleys and a white rope. They were both rated for 1500+ pounds. We took off the outer coating which is just for protection. We had 3 tubes that fit snuggly inside each other. I'm guessing you would want to use 3 tubes that are each 3 meters long and the one on the bottom being 2.5 meters. We used a mill to key each tube for the ropes to run. We drilled holes in the pipe near the edge and used a 1/8" stainless steel rod. We mounted the pulleys and tied the rope. Finally we welded it to 1/4" Aluminum disc and then hooked it all up to a 2.5" od spindle. The spindle was then hooked up to the cim with the gearing. I think ours was 27.16 to 1. I dont know much about the electrical part so someone else can help you there.

[Simon Strauss]

My suggestion is that you take a look at Greg Needel's presentation on designing competitive manipulators, which can be found here if you scroll down about half way to where it says Needel. The presentation was quite good when i sat in on it at nationals and has a few ideas that should be helpful on how to pull off what was posted by Joe and Bilfred above. Also i suggest that you look through the rest of it because it has some interesting solutions for some other things that i have a feeling that you will need for whatever you are building. If you have any other questions on specifics Greg is reachable through these forums and myself and many others here either heard the presentation or know its contents and can help you if need.

also this might give you some ideas
-Simon

[acer_7]

Well, the type of extension i need is a horizontal one. I don't need to lift anything. I am using this extension mechanism as mean of blocking another robot. I have thought in the fork lifting mechanism like the one Billfred has sent in this link http://www.chiefdelphi.com/forums/a...tachmentid=2834 but I don't know how would it affect the balance of the robot; especially when u extend for about 6 meters.

If I used a light material, will it work ?

[Al Skierkiewicz]

Acer,
An extension for 6-7 meters would need some serious counter balance or a support at the end to hold up the extensions. How much stess will the device receive from the blocking action? Will the opposing robot be able to crash against your device? If the answer is yes, you might want to come up with a different strategy.
As to telescoping assemblies, Small Parts sells tubing that nests inside the next larger tube, but they are not long enough for the 6-7 meter dimension. On our robot lasst year, we used some drawer slides from McMaster Carr. They were heavy but allowed us to have and extension that went up to about 5 meters vertically with a 2 meter height when collapsed.

[RogerR]

Originally Posted by acer_7

Well, the type of extension i need is a horizontal one. I don't need to lift anything. I am using this extension mechanism as mean of blocking another robot. I have thought in the fork lifting mechanism like the one Billfred has sent in this link http://www.chiefdelphi.com/forums/a...tachmentid=2834 but I don't know how would it affect the balance of the robot; especially when u extend for about 6 meters.

If I used a light material, will it work ?

i'm not sure what how stiff your blocking mechanism needs to be, but maybe a nuremburg scissors mechanism would be better suited? it folds up relatively compactly, and is fairly simple to actuate. on the down side, they can be somewhat flimsy, especially when fully extended (the reason i tend to shy away from them).

[Joe_Widen]

Well, if you can give a more accurate description of what you need it to do, I'll be more then happy to cad one for you. I'm on summer break.....what else do I have to do?

[acer_7]

Umm . . I will try to explain it more guys & thx for all these replies.

Inspite of the extension being desired to be 6-7 meteres, I don't need it to be stiff at all. I just want it to reach a specific area. The robot competition - I am participating in - has a special playground. Besides, I got a specific start zone for my robots that has limited dimensions. The robot carrying this extension mechanism should have a maximum dimension of 500*1000*2000mm (2000mm is the height).

The scissors mechanism is great but for such distance I need to use large ones and I don't have the place for it as I am using my robot for other things and there are other stuff placed on it.

Can't the forklifting mechanism be modified for such purpose ? I also thought that I would use a fishing rod but I couldn't get an idea for extending them using motors or pulleys. Air was another idea to use in extending the rod but to use that I need an electromagnetic switch and other pneumatic stuff.

[Andy Baker]

Originally Posted by acer_7

Umm . . I will try to explain it more guys & thx for all these replies.

Inspite of the extension being desired to be 6-7 meteres, I don't need it to be stiff at all. I just want it to reach a specific area.

If you don't need it to be stiff, then you can unroll a thin sheet of spring steel, much like a tape measure. This can be motorized, as the steel tape can be shot out (at about 25cm/sec) and recoiled with the same motor.

Is the arm simply touching something 6-7 meters away? If so, then the above suggestion works well.

Good luck,
Andy B.

[Richard Wallace]

Can this be a one-shot mechanism; i.e., can it start within the original 500 x 1000 x 2000 limits, then deploy once to reach the 6000 - 7000 height, requiring manual intervention to get it back to the starting configuration?

And how much payload do you need to raise to the target height?

[edit: I was thinking of some shock-corded tent poles with sections of fishing rod to deploy them.]

[Billfred]

Originally Posted by acer_7

I also thought that I would use a fishing rod but I couldn't get an idea for extending them using motors or pulleys.

Well, here's an idea that might work for you. Have a mass (how much depends on fifty other things) on the end of your line, which you plant at the location. You then drive about with the reel disengaged, like you were casting the line if you were using the rod for its intended purpose. Once you're ready to unblock, engage the reel and start turning.

[Joe_Widen]

Here, coudl you string 6 of these together and using one pneumatic piston to get the first on out. Then you could hinge the rest together and use a fishing line and rell to pull on them and get them out?

http://www.chiefdelphi.com/media/photos/25088

[Al Skierkiewicz]

Originally Posted by acer_7

Umm . . I will try to explain it more guys & thx for all these replies.

Inspite of the extension being desired to be 6-7 meteres, I don't need it to be stiff at all. I just want it to reach a specific area. The robot competition - I am participating in - has a special playground.

Acer,
Are the rules published on the web so we can see them? It might help if we could get a complete picture. Several years ago, our competition had a requirement that allowed many teams to use Andy's suggestion above. There was great fun and anticipation waiting for the "magic tongue" to deploy at the end of a match.

[Andy Baker]

Originally Posted by Al Skierkiewicz

Several years ago, our competition had a requirement that allowed many teams to use Andy's suggestion above. There was great fun and anticipation waiting for the "magic tongue" to deploy at the end of a match.

Does anyone have any old videos or pictures of tape measure deployment or coils of spring steel unrolling from the 2002 FIRST Competition? If this mechanism is legal for Acer's competition, we can all pick the best of these mechanisms and give Acer some good examples.

292 had a motorized tape measure by the end of the season... it was really neat.

111 had a reliable unrolling steel coil.

535 had a bigger version of a motorized coil... it was very impressive.

Andy