Official Team 2526 Robot Model!!

[Dick Linn]

Have you done any rough calculations of the forces required to raise such an arm with the weight and leverage involved? Especially with the limited air pressure and volume available... Can anyone help them out here?

[RyanJK]

We wanted to perform those calculations to see if our arm was feasible, but nobody quite knew how to do them, and we couldn't find a website that explained the process, so if anyone could tell us how to caculate those things, that would be great!


I'd also like to thank everyone who's helped us out, when we made this thread, we thought we would get some help, but the amount of help we got is surprising. Thanks so much!

[Dr Theta]

Hey Maple Grove, this is Anoka, I was wondering what the dimensions of the circular pieces of the claw, and how they fit within the robot dimensions. It look's like a solid design. Good luck this year!

[Dick Linn]

Ryan, do a search on "class three lever". Just try to do the calculations on the middle elbow joint, ignoring the rest. It isn't too hard to "ball-park" it.

Better yet, borrow a bowling ball. Hold it straight down by your side, and have someone try to lift your arm and the ball by pressing up on the bottom side of your arm an inch or two below your elbow joint. That will give you an idea of the force necessary to raise that arm. You only have so much air pressure available. You can "super size" the cylinder, but you only have so much energy available in the compressed air tank and what the compressor can deliver on demand.

[=Martin=Taylor=]

I would be concerned with dropping the ball. I'm not sure that claw will be able to squeeze it tight enough. Some drawer-liner will definitely go a long way in providing "grip" to your manipulator.

I'd also be concerned with such skinny pieces of wood being broken. Our manipulator last year stuck out less than yours, and it got smashed several times . What we eventually did was wrap the wood with fiberglass; this made it very strong and it never broke again.

Just some tips to improve your design. Otherwise I think it is pretty slick! Good job CAD-ing your robot your rookie year! It took us 11 years before we did that!

[Gertlex]

Figure out a way to brace the arm from swinging side to side too much. Turning with the ball lifted might well provide a heck of a lot of air drag causing significant problems.

A couple approaches...:
-Simple vertical rails on the side of the arms might help minimize swaying of the arm.
-Line the parts of each arm joint with aluminum plate (3/16 or 1/4, is my suggestion), and run a larger bolt size through that.

If you want help with the calculations, contact a local college with any sort of engineering at it... I'm sure you'd be able to get a professor to donate a couple hours of time doing/showing how to do the calculations to determine which cylinders you'll want.

Definitely make design changes so that you can get those arms in your starting box... You might need to be creative (but smart) with a method of having the claws start folded vertically, and then drop down and lock in place.

[Adama]

Originally Posted by Daniel Bathgate

Make sure you understand how the pneumatic system works. As rookies last year, we designed an arm that bears a strong resemblance to yours, but didn't realize that the pneumatic cylinders can be either all the way out or all the way in, not stopped in the middle with the provided parts. We came up with a hack that used two solenoids per cylinder to achieve midpositions, but we had major control problems and ended up having to remove our arm. The cylinders you have also look undersized to me; I have doubts they will be able to hold the arm and trackball up.

That's a really cool design, just avoid making the mistakes we made with pneumatics.

Can you explain the hack further? We are looking at a way to get multipositions from a piston and this could be very helpfull.

thanks

[Dan Petrovic]

Are you sure those pistons will be able to pick up the ball?

Also, since you're using C-channel on the arm, be wary of any twisting that may occur during the match.

It's great that you guys realize the importance of modeling your robot with CAD software!

[Daniel Bathgate]

Originally Posted by Adama

Can you explain the hack further? We are looking at a way to get multipositions from a piston and this could be very helpfull.

thanks

Take a look at this thread. I tried to explain what we did, and there is in my opinion a much better idea there as well.

[mp.nighthawk]

hey, i like your design, like evryone is saying about size and sharpness, sharpness can be controled by just makeing that graber more "safe" lol and then the size i thought id through in that i belive that it just has to fit that rule when it is all folded up and in its starting spot but once it is on the go and time is running then you can have it going crazy large like a transformer lol and also i would personaly look at your electrical bord setup, i belive what your doing is right, it just seams "off" to me

good luck building!
-Vic, 1510

[Phil Ross]

a couple of things that I would reccomend.

1. Make sure you are with your starting Dimentions (width, and Length)
2. Make sure you have more mass on the bottom, our team had to switch to a low rider so that our center of gravity would be lower...this Trackball is MASSIVE! it will cause your robot to tip.
3. The tips of your end effector look a little dangerous to the field elements.

over all, it is a fabulous design and congratulations for coming up with it so early in the season. good luck and don't hesitate to ask more questions.

[edgar_amaro]

hey !!! whats the height and how wide is your robot because before the match starts ... it has to fit within a 38 by 28 inch rectangle ..... doesnt it ???

but nice work !!!!!

[DonRotolo]

You'll be very disappointed with multiple positions using pneumatics. Also remember that gases compress, so if the load on the piston changes, it will move.

It can be done, however, with a double-solenoid valve (3-way), which is an off-the-shelf item. We used the gray solenoid valves, not the blue Bosch ones, and special-ordered them. No need to fool with two solenoid valves and fancy plumbing to modulate the exhaust port....

Don

[esisso]

the design looks great, similar to what we are building.....i dont quite see how yours folds up to fit within the 28x38x60...also as far as cylinders go, you'll need massive amounts of power, get the biggest bore possible for the bottom part of your arm...you might consider a design like this (excuse the poor designing and off scaling but i did it quickly in paint)

[JesseK]

Stick with the halos. Halos are your friend! Hence my new sig.

I'm curious as to how you plan to reinforce the halo claws so that a falling/bouncing ball doesn't destroy them. You could make them out of honeycomb aircraft aluminum and build in a break-point at the mount, with black rubber hoses to pad the sharp corners, but even that is fairly heavy. We're still prototyping different things for ours; we love the idea but we're becoming stumped on how to make one that's quality enough to last several competitions.

Still, glad to see a great idea wasn't only ours!

edit -- just noticed something else with your actuation --
It looks great in CAD, but I wonder how you mated up the pneumatic cylinders that are mounted to your 2 halo claws. They're sitting out there, freely able to move. In practice, this has created a problem with our prototypes: when the cyllinder goes out and opens your "claw", the claw is symmetric, and your top and bottom claws are lined up with each other perfectly. However, when the cyllinders go in and your claw closes, I seriously doubt your claws will still line up. The reason is that there is minutely more friction on one side of your claw than the other, and if there are no restrictions on how far inward one side of the claw can go the side with less friction will go past its symmetric position. I hope I'm making sense of this, I'll get a picture of our prototype later if I'm not.