Re: How do we launch this thing? 2014
 

Quick Question:
Upon analyzing this, I can't seem to find how they are rotating the arm. Do you happen to know how they accomplished this?

Re: How do we launch this thing? 2014
 

Is it possible to use harvester similar to the ones used in rebound rumble. To take in the ball. Then raise up the harvester on an arm and reverse the motors shooting the ball up to make up the 2 feet into the goal. Plausible or is the fabric to big of a factor?

Re: How do we launch this thing? 2014
 

I have contemplated most of these designs, in addition to a cam design. Our team plans to test a pneumatic shooter, but does not predict great success.

Personally, I believe that Simbotics' 2008 robot has a very nice design that would work extremely well this year.

I believe that the best designs are wither something similar to Simbotics' 2008 shooter or some sort of cam with a huge boot attached to the corresponding "hammer". (Google "da Vinci cam")

Re: How do we launch this thing? 2014
 

What you want to accomplish with your launches will dictate how you launch.

Aerial shots:
-Lower angle (<45º line drive) high goal shots?
-Arching (~45º+) high goal shots?
-Over truss 45º shots?
-Over truss near vertical shots (robot keeps rolling and catches ball on other side of truss -no catch points; posession maintained)
-Over truss shots


Low to floor shots:
-Passing only?
-Low goal shots across floor?
-Robot-to-robot transfer/assist passing?
-Passing to human "shots"?

Handling all these well would require both a variable energy launcher and a variable angle launcher spanning nearly a 90º arch in the vertical plane.
A turret for targeting some amount to left-right might also be useful.

Our team is starting out building a surgical tubing powered ram launcher.
The ram will have an infinitely variable retraction tension cord winder with a trigger system that only accelerates the ram itself and the tension cord - no stored energy wasted on anything else - like a crossbow, but without the bow.

We are prototyping now to see how compact and short travel of a ram we can have while still shooting fast enough for consistent accuracy and adequate trajectory & travel.

We are not yet clear now many degrees the shooting angle of ram will need to be made adjustable. We also want to load balls as high up on the bot as possible, so shots cannot be easily blocked, and less energy needed to clear truss and hit the high goal.

-Dick Ledford

Re: How do we launch this thing? 2014
 

Try using surgical tubing and making a slingshot ;)

Re: How do we launch this thing? 2014
 

When I talked to my electronics team: "Why would we use pneumatics when we can have a crossbow!"

In all seriousness, linear punches sound really good this year. But prototyping will determine where we ultimately go.

Re: How do we launch this thing? 2014
 

One way to make a piston into a possibly better shooting using a "simple machine" would be to attach a piece of chain to a piston and wrap the chain around a curved piece of aluminum which is then attached to a kicker.
I know this is a bad description, but basically, when the piston retracts, it pulls the kicker around a pivot point, creating a "knee" joint and a mechanical leg kicker.

Re: How do we launch this thing? 2014
 

Not an FRC-er, but a teacher that is shadowing the team at her future place of employment

From what I have seen so far, a flywheel is a perfectly viable solution. We used a flywheel on both sides of the ball each powered by a DEWALT 20-Volt Li-Ion Cordless Brushless Compact Drill. We had each going at about 2,500 RPM, which we believe is possible in the competition, spaced apart the recorded diameter will little luck. However, when we brought each in 1/5 inch the ball squeezed right through flying at the wall (10-25 feet away) and hitting with decent speed.

We took the rig outside (in heavy winds) and got recorded distances of 75ft lateral and what we believe to be 24 upwards (again, heavy winds). However, the ball popped after four throws. If you are confident in not completing more then four cycles, and have a blatant disregard for the sanctity of field elements, go for it. Too bad full-field tosses are illegal, because this thing is beastly.

Until then, we will be refining our shooter (Arial Accelerator, as the kids dubbed it) and work on getting videos up.

Re: How do we launch this thing? 2014
 

I built a quick prototype pneumatic launcher today and was disappointed by how weak it shot. We did a variety of tests at different angles (~10 degrees, 45 degrees, and ~75-80 degrees) and found that the ball flew about 6-7 feet at highest. Barely enough to clear the truss.

Re: How do we launch this thing? 2014
 

Interesting....I saw video of a different pneumatic launcher that today shot the ball briskly into the 10 ft high ceiling.

My guess is that you were not using the best geometry, cylinder size, valve type, or something.

Re: How do we launch this thing? 2014
 

What were the cylinder specs?

can you link that?

Re: How do we launch this thing? 2014
 

We are planning on using a catapult with surgical tubing as our strength, a hexagon to cradle the ball, and a shift and winch system. We also are planning on having a long kitbot with a high geared six motor drive train. One thing we are also weighing through is our floor feeder needs to be able to take hits and not shear off. And since we plan on having a long base, the ball is wider than our robot so a floor feeder above the ball will be hard to keep within the frame. We thought about two wheels on the side that grab it, than lift it into catapult, this would allow it to start in bumper zone then the feeder shoots down, we drive forwards, shoot, pull feeder up and maybe have three different programs that send the bot to different zones. I think several teams won't plan for this so we might see some breakage. One difference this year is that one robot can do it all (excluding goalie), all that is needed 1st is something that can shoot the ball into the high goal and over the truss, 2nd is the ability to pick balls up off the ground, 3rd is to be able to catch. I am thinking of putting bars up around the hexagon that aid in backstopping and catching, it will also help with defense?

Re: How do we launch this thing? 2014
 

Could you (or anyone else who's trying this method) upload a video? I'd be interested in seeing your results.

Re: How do we launch this thing? 2014
 

We can upload one once we get our new ball. It is pretty easy to test yourself if you have a couple of worn out grinding wheels for your drills. We sanded the grinding wheels of spurs, then a filler primer, and then we took them to the lab. If you lock your elbows, tape the trigger down, and hold it upwards you can achieve the same result without a brace. If the ball evens come close it is going to go flying, so be as safe as you can be in this.

Re: How do we launch this thing? 2014
 

Team 701 plans to use a spring loaded linear slider system that gets pulled back by a winch to reset, and when a pass or toss is necessary, we disengage the winch pneumatically, and the energy stored in the spring tosses the ball. We proved this concept today with a slingshot type prototype that uses surgical tubing instead of a spring to store energy. We used an old custom winch and our 2013 robot to power it, and the ball was lifted more than five feet in our trials. Our next prototype will involve an actual spring, and we plan our springs to be tough enough that they can launch the ball a good height and distance, with only needing to compress the springs a mere few inches, and probably no more than six inches. We hope that this should save space and weight on our robot