How do we launch this thing? 2014
 

Ah, that glorious engineering question- how do we get this thing in the air?

I understand the ball is 24 inches wide and ~2.5 lbs. If anyone has more detailed numbers or tolerances, please add them.

Pyrotechnics are right out. They would totally set fire to the fabric. I'm sure the first thoughts everyone has are catapult arms. I was thinking about this and one of my sketches caused another problem appear. If arms are used to launch the ball, their own unladen weight will slow down acceleration of the ball or require a huge force to move.

I'm thinking broadly now. What if you used some much smaller arm that hits the ball and the impulse sends it flying? What can we come up with here?

Other things worth consideration:

The springs offered as part of the voucher http://info.vulcanspring.com/first-robotics-competition
They are constant force flat coil springs, not helical coil springs as you might picture.

How quickly will it be necessary to retract/ prime whatever launcher you have?

Re: How do we launch this thing? 2014
 

Welcome to the forum!

There's always this option.....

Re: How do we launch this thing? 2014
 

flywheel is out of the question due to the fabric ball. Our team is seriously considering the low goal.

Re: How do we launch this thing? 2014
 

I have considered some sort of pneumatic launcher. Team 1114 used one in '08(Overdrive). It actually works very well.

https://www.youtube.com/watch?v=NYNEAL_dK6I

Re: How do we launch this thing? 2014
 

The flat coil springs could make for a good dampener when trying to catch the ball.

As for launching the ball, my first thought was a pneumatic impulse hit to get it going. That idea is now retracted from my head since I realized there will be a great need for power regulation when launching. There are a few more ideas I have but they still have to be realized on paper before I go shouting them out.

Re: How do we launch this thing? 2014
 

Thanks for the welcome.

Yea, that is a question, how do you vary power for a shot vs a pass? I like a variable impulse system with different points of retraction for different range.

Re: How do we launch this thing? 2014
 

Wasn't pneumatic, though. I checked earlier today.

Re: How do we launch this thing? 2014
 

Looking at something very similar to this with adjustments for catching and making sure we can score in the 1 point goal.

Something I have been trying to solve is whether a linear system of shooting or a parabolic system of shooting will be best. By this I mean the flight path of the ball if shot at the 10 point goal

Re: How do we launch this thing? 2014
 

Any shot you take than launches the ball into the air will take a parabolic path. For linear I guess you could... push/kick the ball into the front or side of the low goal?

Re: How do we launch this thing? 2014
 

We're looking at our 2008 robot design (there's not much left of the robot to look at, unfortunately). It worked....and this year's game piece is light and small, relatively speaking.

What I meant more was like the path it took in the shooter. Like a circular shooter we saw in rebound rumble or a linear one we saw in ultimate ascent. But thinking about it, a circular shooter would be massive. Probably not feasible either

Re: How do we launch this thing? 2014
 

To clarify on what Eric has said, a 3/4" aluminum rod is propelled forward by surgical tubing. The whole set is pulled back by a winch with a dog gear, when the dog gear is released the rod is launched at the ball.

here is exactly what they describe. http://simbotics.org/first/2008#robot

Re: How do we launch this thing? 2014
 

Does a pulley spin free on a shaft when dog gear is released?
If so, this lowers peak velocity of ram, since rotating winch pulley/drum stores energy as unwinding cord spins it up to peak rpm.

A better system, when triggered to shoot, will have the contracting surgical tubing be accelerating only the ram itself and whatever low mass tension element(s) are attached to the ram.

Plus, what happens to the winch cord as pulley/drum spins free when ram fires? Does it reverse wrap, such that the next wind gets done continuing in the reversed wrap direction. If the ram travel is small, not so many turns of winch will be needed, so less chance of cord getting tangled up during free spin.

If variable power shot is desired, reversing the rotation for alternating shots is useful, for when a multi-turn potentiometer is used to control cutoff point for desired amount of wind, since the pot only has a limited number of turns over its full range. Winding opposite ways for alternating shots keeps the pot from hitting its end of range.

-Dick Ledford

Re: How do we launch this thing? 2014
 

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

Re: How do we launch this thing? 2014
 

Jim has posted some really good suggestions here... this is, largely, a solved problem. Many teams found a way to launch balls in 2008 that were similar to these ones, but larger and heavier.

Dig back in the forums and videos and team websites if you weren't around FRC in '08.

And watch the BuildBlitz and Robot In Three Days (and a snowstorm) for ideas.

It isn't a question of how, so much as how to do it most efficiently!

Jason

Google: FRC 2008 launcher or maybe FRC Overdrive Launcher and check out the old videos and websites.

Re: How do we launch this thing? 2014
 

One issue with a pneumatic cylinder launcher is the peak piston velocity being restricted by the rate at which air ahead of the piston can exit the cylinder.

Ideally, the space in front of the piston disk seal would be a vacuum, and offer no resistance. This could be accomplished by sealing both ports of the cylinder with the piston extended.

Then by mechanically pulling the piston back into the cylinder so as to build up pressure on one end and partial vacuum on the other piston exit end, you can make it into a "gas spring"
Releasing the hold on the compressed piston would fire it at a higher speed than when there is air ahead of the piston.

This may not be legal though. There are many safety issues. Too much piston retraction could build up pressure in the cylinder exceeding its limits.
Also, piston can overshoot inside cylinder and impact the head at the exit end, damaging it.

-Dick Ledford

Re: How do we launch this thing? 2014
 

Can you reference a rule that says this?

Re: How do we launch this thing? 2014
 

Per the scoring section of the manual:


Emphasis mine

Re: How do we launch this thing? 2014
 

There may be a way to get pistons to work. You guys have only thought about if pistons applied force directly. What if the pistons pulled the ball instead of pushed it? Just a thought:rolleyes:

Re: How do we launch this thing? 2014
 

I am very interested in seeing this video, could you please link it for us?