LIFT VS. LAUNCH

[MrForbes]

It can be very dangerous to make a mechanism that is capable of launching a ball that high, so you would need to go to a lot of extra trouble to make sure your design is safe. As I see it, the danger is not with actually launching the ball...the danger is that someone could have their bodily parts in the way of the mechanism when the ball is NOT in it, and it could give them a severe blow.

We figured out a way to use an air powered catapult that moves slowly if there is no ball on it, but with a ball in place, it is able to launch the ball quickly.

This is not an easy thing to design....so if you go this route, you really need to think about it carefully. We are using restrictor valves to keep the cylinders from filling quickly, and using an arm on top of the ball to hold it down, and the ball holds the catapult arm down. The system can only build up pressure when the ball is in place, and launching the ball uses up all this pressure.

[McLOVIN]

Originally Posted by squirrel

It can be very dangerous to make a mechanism that is capable of launching a ball that high, so you would need to go to a lot of extra trouble to make sure your design is safe. As I see it, the danger is not with actually launching the ball...the danger is that someone could have their bodily parts in the way of the mechanism when the ball is NOT in it, and it could give them a severe blow.

We figured out a way to use an air powered catapult that moves slowly if there is no ball on it, but with a ball in place, it is able to launch the ball quickly.

This is not an easy thing to design....so if you go this route, you really need to think about it carefully. We are using restrictor valves to keep the cylinders from filling quickly, and using an arm on top of the ball to hold it down, and the ball holds the catapult arm down. The system can only build up pressure when the ball is in place, and launching the ball uses up all this pressure.

Even though its is safe without a ball, what happens when you finish a match and the ball is on your robot and the catapult is pressurized, that scenario is what scared me away from using a catapult

[robogeek753]

First of all, kudos to all the teams who have managed to build a catapult not only capable of simply holding/controlling the ball, but launching it into the air. Our team considered this at the beginning of the season, and decided that it would essentially be too complex (something we have had problems with in the past).

So, we decided to build a relatively simple forklift mechanism with a rotating "grabber" that the ball simply rests in (A teammate has the inventor drawings ). A winch pulls a cable (winch is just a plastic attachment to a motor (window i think) that lifts the "grabber" to 6'4" (forklift is bent at start, pneumatic piston straightens). At that height are two 10" stroke, 3/4" pistons that push the ball onto the overpass (12 pts. at end of match) we then move a few inches, push again (on the ball on the overpass) and the ball comes off the overpass, scoring a hurdle.

While we have no "catcher" design, we can regain control easily, and perhaps even "pass" the ball to another robot (hard though).

In short, our team is all lift.

[MrForbes]

Originally Posted by McLOVIN

Even though its is safe without a ball, what happens when you finish a match and the ball is on your robot and the catapult is pressurized, that scenario is what scared me away from using a catapult

The catapult will be pressurized with a single acting solenoid valve that releases the "up" pressure when the robot shuts off.

[ChrisH]

Originally Posted by fireball3004

Our team is making a lifter, we were thinking about launching the ball, but after some discussion with other schools we decided it might be considered dangerous. thoughts?

Over the weekend some of us on the team began experimenting with different ways to get a track ball over the overpass. Our original ball did not last long enough to be used on our full sized practice overpass. Our new balls arrived Friday.

Since we had no robots ready to play with we were trying different things with human handlers. We found out pretty quickly that with practice and good timing the balls could be easily kicked over the bar.

I figure if a human can do it in their own strength, then the act itself is not inherently dangerous. Having been hit by a couple of these flying objects, I'm more worried about damage from the fall if they should knock me over than being hit by the ball itself.

It is still possible to store or release the necesssary energy in a manner that could result in injury, or to have the energy containment system fail in a catastrophic manner. That is the sort of thing you need to be careful of.

ChrisH

Oh and by the way, the BeachBot practice field (funded by SCRRF) is open to anybody that wants to use it from 10-4:30 on Saturdays and other times by appointment. Details are in the newsletter sent out by the Regional Committee chair, Nancy McIntyre.

[joeweber]

We started out lifting the ball up to the over pass ( our robot will just go under) and shooting it over with a 1.5 pneumatic. Using the garage compressor at 60 psi we were able to throw it 3 ft horizontal and vertical just enough to clear the rack. When we tried it with the robot compressor it would only lift the ball and not throw it. So we are just pushing it up onto the over pass. Most people don’t know this but if you push it over at the spots between the ball locations the pipes are only about 12 inches apart and the ball just rolls off with little effort. So we can push it up and over with out hardly slowing down. Some drawings are at http://www.team1322.org/team_news.htm

[Alan Anderson]

Originally Posted by dtengineering

We decided to go with an arm to do the lifting, in part because if you have a partner (or two) each capable of quickly placing the ball on the overpass and then quickly lifting the ball from the overpass then you never have to give up posession of the ball.

I don't see how this could work. The ball on the overpass hasn't crossed the finish line yet, so you can't hurdle it from the far side by grabbing it and keeping it.

[dtengineering]

I had a nice explanation of why this would all work, based on the definition of "crossing" requiring all parts of the robot to cross the line, and the assumption that you were not penalized until you "crossed" a finish or quadrant line in the wrong direction, but re-reading the rules, specifically G22 kind of makes mincemeat of that idea. You get penalized just for breaking the plane of the line once you have "crossed".

Pity. The "bucket brigade" scenario would have been fun to watch and would have rewarded technical proficiency and teamwork. Not that it is 100% impossible, as the "scoring robot" could pass the ball completely over the finish line to the receiving robot... or for the receiving robot to grip the part of the ball that has passed over the finish line while the ball is on the overpass... or for a robot to be built in such a way that it can pick up the ball on the counter-clockwise side of the overpass without first having to completely pass over the finish line (robot turns around, extends a bar from it's "front", backs across the line leaving the bar over the finish line, reaches up and grabs the ball, then retracts the bar and moves away from the overpass in a counter-clockwise direction) but the combination of G22 and having the finish line directly underneath the "counter clockwise" side of the overpass makes it even more difficult than it would have originally been.

Jason

[EricH]

There are some gripper designs that have the capability to render <G22> harmless in this situation. They'll need a very good driver/manipulator team to pull off the maneuver, though.

[s_forbes]

I expect that is a strategy we may see in Atlanta this year. With all of the teams going with arm designs, there is bound to be a set of three that get paired up and can pull it off.

[dlavery]

Originally Posted by dtengineering

Pity. The "bucket brigade" scenario would have been fun to watch and would have rewarded technical proficiency and teamwork. Not that it is 100% impossible, as the "scoring robot" could pass the ball completely over the finish line to the receiving robot... or for the receiving robot to grip the part of the ball that has passed over the finish line while the ball is on the overpass... or for a robot to be built in such a way that it can pick up the ball on the counter-clockwise side of the overpass without first having to completely pass over the finish line (robot turns around, extends a bar from it's "front", backs across the line leaving the bar over the finish line, reaches up and grabs the ball, then retracts the bar and moves away from the overpass in a counter-clockwise direction) but the combination of G22 and having the finish line directly underneath the "counter clockwise" side of the overpass makes it even more difficult than it would have originally been.

Jason -
No need to be despondent. Keep that mental image in mind, but just make one minor adjustment. You started toward this scenario in your first message, but stopped short of fully developing it. Think about your "bucket brigade" of robots handing off the Trackball from one to the other by temporarily storing it atop the Overpass. But make the process faster. Rather than slowing down the process when the Trackball is stored on the Overpass, make Hurdling the part of the process with the highest-velocity Trackball movement. Rather than three well-coordinated, excellent "Super Lifters" you need three well-coordinated "Launcher/Catchers." Then your original scenario becomes:

Robot A is positioned on the far side of the finish line, ready to catch a Trackball.

Robot B approaches the near side of the Overpass, and launches the Trackball in a spectacular fashion. The Trackball describes a perfect parabolic arc over the Overpass as it heads toward Robot A (if you are thinking about this correctly, you should have a nice mental image of Max the dog in "The Grinch Who Stole Christmas," waiting outside the house for the Grinch to throw the massive bag of toys down to him from the rooftop after stealing them all from Whoville).

Robot C is doing a lap with a Trackball in possession.

Robot A catches the descending Trackball before it ever touches the ground in its whizz-bang-super-combination-Trackball-basket-and-catapult-launcher (it's a dessert topping! it's a floor wax!). The crowd goes wild! The Hurdle is complete, and the robot proceeds to do a lap.

Robot B crosses the Finish Line (completing a lap), and turns around - ready to catch the next Trackball as Robot C approaches and launches it.

Repeat until you win.


That is the ultimate "dream match" that I long to see. If not during the season, maybe we will see it at IRI.

-dave




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[MrForbes]

Wow, you must be looking at our design drawings! (is that why we posted them?)

The ball catching stuff looks to be fun....we can't wait....

[dtengineering]

Originally Posted by dlavery

Jason -
..... Rather than three well-coordinated, excellent "Super Lifters" you need three well-coordinated "Launcher/Catchers."

Why, as a matter of fact we had a team meeting on Monday to discuss the problems with the arm (80" limit, mostly), the crossing the plane when you take it off from the back, and to revisit some of our earlier ideas.

Tonight we had a prototype pneumatic launcher in the works and are looking at how to launch (and catch) the ball effectively.

If even two robots can do this working together they are going to do well. They should be able to lap almost as fast as the "racers", at least as fast as the herders, and will be pulling in hurdles all over the place.

I'll keep my eyes open for a match like that.

Jason

[65_Xero_Huskie]

Originally Posted by dtengineering

If even two robots can do this working together they are going to do well. They should be able to lap almost as fast as the "racers", at least as fast as the herders, and will be pulling in hurdles all over the place.

I'll keep my eyes open for a match like that.

Jason

I would love to see 3 launchers on a team, but i don't think that it will happen, i think the most you will see is 2 on a team. (Especially with the serpentine draft)
And i want to see how well and fast these robots can launch the ball over effectively and still be as fast as a lapper. With my calculations a GOOD lapper can do a lap in 10s or less. A launcher with a GOOD launch/catcher will be 17s+ and a hurdler will be 24s+ (Just my rough estimates.) So i would like to see all of the strategies teams will come up with during the season.

[MedievalWarrior]

How would you plan on loading your catapult?