telescoping arm

[JVN]

Originally Posted by Denman

Maybe a totally inovative method is required , we have a secret method that might stun you at its simplicity
How about the parraleelagram method?

Are you refferring to a 4-bar linkage?
This is a perfectly viable solution to a "tall arm".

For some prime examples of 4-bar linkage systems check out the robots from 1997, 1998.

4-bar linkages also made appearances last season as well
(25, 461, 233, others)

Check this one out:
http://www.firstrobotics.net/03galle...0513-1_jpg.htm

John

[KenWittlief]

I was just thinking about how to extend a telescoping arm, and it just came to me!

last year teams built arms that they wanted to extend in auton mode to hit the wall quickly

but this year, the arms would be for manipulating the 2X ball, or hooking the bar

but they dont need to extend by themselves

how do you extend the telescoping antenna on a portable radio or TV?

(you PULL it out, and it stays there)

all you need to do is design a telescoping arm that locks when extended

and to extend it, hook the end on the lip of the mobile goal, or on your alliace bot (or anywhere else you are allowed to grab something on the field)

and then backup your bot to pull the arm all the way out.

I dont think it could be any simplier than that! :c)

[Gabe Salas Jr.]

Originally Posted by TGreen

By any chance do you remember how much the 2 pieces weighed?

For Roccobot 2K, the entire arm design (minus the battery) was about 67 pounds (more or less). Towards the bottom part of the arm, is where we kept the battery. So overall, it would weigh about 75 to a maximum of 80 pounds (which includes 6 big 30" balls). These are rough estimates from what the team could remember.

[Denman]

i didn't mean like that but we have made a lego model here
basically it consists of a main section with some pulleys and you have a parralellagram which when the main internal part gets to the top extends outwards.
Without being rude , i find it incredably hard working in inches and stuff and all the stuff is confusing me as in the uk we are metric, hence our name is systemetric

[KenWittlief]

there is another way to extend a telescoping arm

power car antennas push a still wire up the center to extend it, and pull it back to retract it.

[Dick Linn]

I was in the process of suggesting a couple of alternatives or variations to implementing the arm, then thought the better of it. Not for competitive reasons, but because you will feel so much better if you come up with it yourselves.

We've seen some sophisticated arms and lifting mechanisms in the past, but I'm convinced that there are some very simple and effective (read inexpensive) ways to at least reach the bar and lift off.

If you're stuck for ideas or just want to know what I'm rambling on about about, I'd be happy to discuss it.

Dick Linn
Mentor - Team 975

[Madison]

Originally Posted by KenWittlief

how do you extend the telescoping antenna on a portable radio or TV?

(you PULL it out, and it stays there)

all you need to do is design a telescoping arm that locks when extended

and to extend it, hook the end on the lip of the mobile goal, or on your alliace bot (or anywhere else you are allowed to grab something on the field)

and then backup your bot to pull the arm all the way out.

I dont think it could be any simplier than that! :c)

Though, for it to work by latching onto a mobile goal, there'd have to be less resistance in pulling out your telescoping arm than there is making the goal roll -- otherwise your telescoping arm will be nothing more than a fancy goal latch.

[rswsmay]

Originally Posted by Dick Linn

I was in the process of suggesting a couple of alternatives or variations to implementing the arm, then thought the better of it. Not for competitive reasons, but because you will feel so much better if you come up with it yourselves.

We've seen some sophisticated arms and lifting mechanisms in the past, but I'm convinced that there are some very simple and effective (read inexpensive) ways to at least reach the bar and lift off.

If you're stuck for ideas or just want to know what I'm rambling on about about, I'd be happy to discuss it.

Dick Linn
Mentor - Team 975

I'm interested in finding out your idea. We are currently toying with 3 concepts for extending arms. Using the forklift type, the folding pneumatic type, and the telescoping arms. We have not been able to come up with the "simple" method of telescoping an arm between 10-12'.

[KenWittlief]

Though, for it to work by latching onto a mobile goal, there'd have to be less resistance in pulling out your telescoping arm than there is making the goal roll -- otherwise your telescoping arm will be nothing more than a fancy goal latch.

ok then, lift you arm so its horizontal, and do a victory spin

centripital force will extend it for you

dont demo it in the pits!

[Dick Linn]

OK. Lacking a sketch, try this. Think of 3 sections of tubing, say 3", 2", 1 inch, or whatever nests relatively nicely. Between each of the two junctions, place either a length of surgical tubing or, outside the junction between successive section of tubing, place a coiled clock spring on the outside, business end pointed down. When you collapse the tubing, it will tend to want to spring out to it's former position because of the "springs" placed in the tubing. At the far (top) end, you attach a cable, which is routed straight down through the tube to a winch at the base. The only function of the spring or surgical tubing is to allow the relatively light cable and PVC pipe to extend to the desired height. Reversing the direction of the winch will pull the beastie up. If the PVC tubing is flimsy, so much the better, as it will not interfere with the upward lifting.

A variation of this is to put a small pulley at the top of the base tube on the outside, one on the bottom of the second tube and so forth. Sort of like a Sine wave propagating itself up and down throughout each successive layer of tubing. Retracting the cable will at first extend the tubing then, when at full extent, pick the whole thing up. Having very weak, flimsy tubing might help when lifting, as you only have to lift a foot or so. You won't have to worry about how (or if) the tubing nests back in again. PVC pipe is cheap! Change it if it breaks or bends.

A sketch would be a lot better than my explanation...email me at rlinn@wrsystems.com if you want something you can see.

[rswsmay]

Originally Posted by Dick Linn

OK. Lacking a sketch, try this. Think of 3 sections of tubing, say 3", 2", 1 inch, or whatever nests relatively nicely. Between each of the two junctions, place either a length of surgical tubing or, outside the junction between successive section of tubing, place a coiled clock spring on the outside, business end pointed down. When you collapse the tubing, it will tend to want to spring out to it's former position because of the "springs" placed in the tubing. At the far (top) end, you attach a cable, which is routed straight down through the tube to a winch at the base. The only function of the spring or surgical tubing is to allow the relatively light cable and PVC pipe to extend to the desired height. Reversing the direction of the winch will pull the beastie up. If the PVC tubing is flimsy, so much the better, as it will not interfere with the upward lifting.

A variation of this is to put a small pulley at the top of the base tube on the outside, one on the bottom of the second tube and so forth. Sort of like a Sine wave propagating itself up and down throughout each successive layer of tubing. Retracting the cable will at first extend the tubing then, when at full extent, pick the whole thing up. Having very weak, flimsy tubing might help when lifting, as you only have to lift a foot or so. You won't have to worry about how (or if) the tubing nests back in again. PVC pipe is cheap! Change it if it breaks or bends.

A sketch would be a lot better than my explanation...email me at rlinn@wrsystems.com if you want something you can see.

The springs and surgical tubing could work if the design conforms to the requirements laid out by FIRST for stored energy devices, as well as being safe.

I am not following you on the variant of that with the pulleys installed on the outside of the various sections of tubing. With a pulley installed on the outside bottom of the 2nd stage tubing, how will it slide and retract into the 1st (base) stage tubing.

My variant of that is to use a combination of what was mentioned in a previous thread here, and and your coiled spring suggestion. I'll send you a simple PDF file of the concept I have in mind.

[Mike Norton]

you can make a arm very easy with extruded aluminum 30m x 30m. We put one together in 10 minutes today. it goes out 14 feet. it comes in at 7 1/2 lbs. and only takes up 7" X 3' of space in our robot. I will have pictures up in a day.

[Ben.V.293]

for our telescoping arm we just went down to our local boat shop and bought a telescoping boat hook. Its extremely light (less than a pound), strong, and very long. Plus it already has a hook on the end. it was a very easy solution to a very hard problem.

[Drew Hopman]

We just put one together today that extends out about 14 feet in about 30 minutes. I think that it works great. All of our hard problems have been solved now we just have to build the drive train.
Drew Hopman
Team 801

[Kaelia]

Our team decided against it after...incidents...from two years ago. Cable isn't fun to keep tensioned and stuff =( We did contemplate it for a while though...the thing with telescoping is, it's relatively easy for just two pieces, but once you get into three it starts getting screwy...