I know there is a very similar thread already out there, I just wanted to get some input specifically related to the arm design. What kind of design would work better, fork lift or a bending arm? Ideas? Post away.
I’m not sure how well a forklift would work given that the maximum height of the robot is 60" and the goals with a couple tetras on them would be too high.
If you’ve ever watched forklifts before, you notice that on some, they dont extend upwards to just the top of the vertical segment. It’s like a telescoping pole. the segments in front of the first vertical piece start extending from the top of that point (for our purposes 5’) and allow you to reach a much higher height
One thing about being a 14 year team is you get to see alot of previous design that could work with this year’s game and I think we found a good one today.
I’m a fork truck driver (narrow aisle) and the front end of the truck is heavy and needs to be counter balanced or it’ll tip over. I would assume the same would apply to the robot if something similar was made (I think the robot would end up way overweight and also easy to tip over).
But our forklift doesn’t need to be on the front of the robot. It could be right in the middle: simply drive underneath the large tetra and deposit your small tetra. That’s the advantage of just having tetra frames. You can be inside the big tetra while you cap the little one.
This however, only removes the need for a counterweight, and if I hit you with your center of gravity really high you’re going to go a-tumbling.
Forklifting can be worked nicely as can an articulating or telescoping arm. But why would some one on 177 mention that? 
The history section of our website should inspire some of you.
http://www.swindsor.k12.ct.us/Highschool/activities/clubs/first/
Pete
Because I’m a rookie and don’t remember last year
I think using the arm is better since you can grab the tetras anywhere around the robot; whereas, the forklift requires you to be in a specific position to grab them. However, with an arm, it’s harder to control your robots balance n might tip over, but you may be able to use your arm to pick yourself up.
What specific arm designs would probibly work best for manipulating the Tetras?
The teams ive been on have done both an elevator system and a stereotypical arm design. Both have worked to some extent. The standard arm design is easier to design and build, but i feel the elevator design is the easiest for the drivers to handle. The most important factor in the design is ultamately how much thought and detail goes into it.
You’re right, an elevator design probably would be easier for the drivers to handle. but depending on which way you make the lift mechanism, you might be limited to coming at the tetra in a specific way. Either design you use is goign to require a lot of practice though. Manipulating those tetras will be no piece of cake.
Something to consider though about going into a goal structure and then pushing the tetra up is that you risk dislodging the already stacked teras (incuring point penalties and losing posession permanently for the goal to the oposing alliance), there could be tetras inside the goal that impede your movement, and you have to be able to get over into the goal structure without tipping (topheaviness could become an issue). Hope that helps you guys fine tune something to meet your objectives. 
we’ve had considerable success with a few kinds of arms but all ‘bending arms’? i think you might call them? our best one was this year’s occra one. which wouldnt be too useful in this year’s first game but it was a nice 4bar crossing linkage thing.
My first impression is that (sorry Pete) a forklift would work better. Besides being a lot easier for drivers to use, it’s easier to get multiple points of contact on the tetra with a forklift than an arm. If you try to grip a tetra with an arm that only makes contact at one point, you need to make sure you have it gripped hard enough to keep it from rotating. But if you make contact at multiple points it’s harder for the tetra to move.
i would go for a cross design. The vertical would press on one edge of the triangle. The horizontal would go through two holes somehow. Then sort of pick up using the pivot points, then that would lift the triangle up at an angle, making it easier to put the tetra on the goal
Has anyone considered a three pronged hand at the end of an arm? Any point of contact would result in the tetra being grasped in some way. What do you think?
When I was on team 535 (2001 rookie year) we had a robot with a forklift mechanism. With our arm we could lift the large ball 11’ into the air every time :ahh: And we were able to keep it within the 60" spec.
Wayne Doenges
CAD Mentor
wiat… are you referring to your forklift as the arm? and if you have any pictures please, dont refrain from posting them.
My fear is that when you are trying to place the tetras and when your arm or forklift or whatever is at its highest point, a little bot will come over and knock you over. Due to your arm being high up, you would be very vulnerable. Besides, when you stack those tetra’s you have to remember that the height of the stack will be increasing and you have to make you sure your bot can go higher than the height of one tetra stacked.
GO 1403!!!