Best Way to Launch unusual items?
 

We were talking and whats the best way to launch unusual items, such as lunacy balls, breakaway balls, frisbees, footballs and other random object you could also find around the shop?

Re: Best Way to Launch unusual items?
 

A specially designed hammer?

Re: Best Way to Launch unusual items?
 

Catapult/Slingshot, unless you know a way to make a wheeled shooter account for every shape change :rolleyes:

Re: Best Way to Launch unusual items?
 

Do you want to launch these objects more than 30 ft?

Re: Best Way to Launch unusual items?
 

Wheeled shooter with suspension to account for various ball sizes.

Re: Best Way to Launch unusual items?
 

Preferably

Re: Best Way to Launch unusual items?
 

This or use a large foam wheel, similar to 118 in 2013.

Re: Best Way to Launch unusual items?
 

This faux TED talk covers some of the parameters of odd items being launched.

Re: Best Way to Launch unusual items?
 

When you're shooting a variety of various shaped items long distances, wheeled shooters aren't going to perform as well. Wheeled shooters as we know them in FRC work best with objects that can roll / spin - balls, frisbees, etc. We are abe to design such precise and repeatable wheeled shooters because we are shooting such an incredibly narrow range of items - a single game piece, with manufacturing tolerances being the only varying factor. Wheeled shooters also shoot multiple game pieces in quick succession really well, which doesn't seem like is needed here. Wheeled shooters are solving the wrong problem.

A catapult cares much less about the geometry of what is inside it - it brings itself and its object up to speed and stops at the angle producing the desired trajectory. Obviously this will have varying results with each game piece as well, but I think it's a better solution for the constraints at hand.

Take a look at what 16 did in 2012 as a starting point.

Re: Best Way to Launch unusual items?
 

Most FRC grippers are made specifically to hold a certain size/shape/weight piece, so most of the usual tricks won't work. Some sort of speed-controlled catapult/ballista (I'm thinking motors and encoders) could be used to get everything up to an appropriate/consistent speed. To hold the pieces, I'd try a gripper that can accommodate many shapes, probably by having multiple pneumatic arms that curl in on the "game piece". You can use the thing on the other side of your wrist as a rough template.

Re: Best Way to Launch unusual items?
 

The argument was started while going over the design of our hockey puck shooter on whether we should go:

air powered(paintball gun like)
inline wheel shooter(ultimate ascent)
top wheel shooter with roller bottom(baseball shooter)
Spring loaded plate(pinball)
Slingshot

or is there something else more efficient to shoot the put accurately at really high speeds for our challenge.

Re: Best Way to Launch unusual items?
 

i've seen 3996 use a hammer to kick basketballs back in 2012

Re: Best Way to Launch unusual items?
 

This is an amazing opportunity to make plywood ghetto prototypes and do some good ol' fashioned testing. The three main things that peoples are suggesting are catapults, slingshots, hammers (all easy to prototype) and wheeled shooters (more difficult but doable).

Things like air power can probably be crossed off the list because getting a seal on a lunacy ball would be... lunacy (sorry, I had to) as well as accommodating the different shapes and sizes of the other pieces.

I think that a catapult would work best in this application but have no real experience (and neither does anyone else as far as I'm aware). Unless someone here can point to an off-season project they've done shooting multiple different gamepieces I would take everything with a large grain of salt. Implementation is an entirely new can of worms. If you do go for a catapult there are multiple options; lots of motor, stored energy and release (surgical tubing/spring), pneumatic, something else I've inevitably forgotten. Each option has advantages and disadvantages.

Re: Best Way to Launch unusual items?
 

I did a catapult a few years back for rebound, with our initial prototype we saw potential because it did give the arch but it isn't what would be needed for this project which is more speed.

and as for a slingshot i know people (my team included) made kickers that were a piece of lexan held back and then released to exert a force to kick the soccer balls.

Re: Best Way to Launch unusual items?
 

Have you tried more power? You can relatively easily get catapults to launch really far and really fast. You can flatten the exit angle for it to go faster but not farther.

33 using a catapult to full court shoot in 2014
https://www.youtube.com/watch?v=1-oWAS9_Rl4

Re: Best Way to Launch unusual items?
 

Don't know if that works for a hockey puck trying to reach 100+ mph

Re: Best Way to Launch unusual items?
 

Building a generic shooter that can accept objects of basically any size or shape and propel them to 100 mph is a really, really, really tall order. A catapult launching generic objects at even as fast as 40-50 feet per second is a lot more possible.

Re: Best Way to Launch unusual items?
 

I'd suggest a linear punch shooter with an adjustable holder (like 1986, pink team, 948, etc in 2014). Really easy especially if the accuracy doesnt have to be that great

Re: Best Way to Launch unusual items?
 

If you want 100+ mph, I would suggest air cannon. Just use a sebot to account for the various object shapes/sized. :cool:

Re: Best Way to Launch unusual items?
 

what is a sebot? and one of the small scale prototypes we will test tomorrow is an air cannon.

Re: Best Way to Launch unusual items?
 

A sabot is a device used in a firearm or cannon to fire a projectile, such as a bullet, that is smaller than the bore diameter, or which must be held in a precise position.

Please remember to consider the safety of whatever mechanism you choose. You will be dealing with a lot of energy with whatever device you use.
In the case of air cannons, do not use PVC pipe to store gases under pressure.

Re: Best Way to Launch unusual items?
 

Yea we knew not to use PVC since we were looking into making a T-Shirt launcher.
And with whatever design we do were making a two stage safety where two buttons will constantly have to be pressed otherwise it wont shoot or shoot very slowly.

Footballs can be launched with just two spinning wheels for very large distances. Look up "football launcher" on youtube for a demonstration.

Re: Best Way to Launch unusual items?
 

For hockey pucks, I would constrain the puck to be flat with some sort of chute and use a dual-wheel (left/right) shooter. If you want them to fly rather than slide along the ground, you could make one of the wheels rotate a bit faster than the other to give some gyroscopic stabilization.

Also, I recall a linear accelerator that I rough-designed for Aerial Assist that used a motor and gearbox, two linkage arms, and an angled glide with a basket that the ball sat in. The point of the two-armed linkage was to match impedance between a motor/gearbox running at a constant speed and a load which was accelerating. If you aren't interested in picking up strange pieces (or will do this separately), this would be a useful design. We didn't build it (used a hammer for AA), but I am pretty sure we could have gotten the yoga ball high enough and far enough to make clear truss and high goal within the required frame perimeter. By making the travel longer and gearing the motor lower, any reasonable speed should be feasible. I'll look for the drawings and spreadsheet this evening.

Re: Best Way to Launch unusual items?
 

You can do the same with pneumatics, using the piston as the sabot. Remember that for this project you can use larger diameter solenoid valves and fittings than the FRC standards!

Re: Best Way to Launch unusual items?
 

I was unable to locate the original drawings and spreadsheet, but I have re-generated them in the attached document.

The linkage arm connected to the motor/gearbox is 7 units long, the shaft of the motor/gearbox is 11 units perpendicularly away from the glide rail, and the secondary linkage arm is 20 units long. The "layout diagram" shows what the linkage arms will look like for each 20 degrees of rotation of the gearbox. The position-speed-accel-power shows these curves as a function of angle through the cycle, assuming that the motor/gearbox is rotating at constant speed, the mass of the load is constant, and motion is horizontal. The goal in designing the offset and linkage lengths was to produce a flat "power" curve that covered as many degrees as possible without requiring too much acceleration (and likelihood of jamming) on the return stroke. This one gives a nearly flat power curve from 40 degrees to 160 degrees. Note that the "power" for the braking and return stroke are shown as being about six times as high as the main forward stroke; however, I am assuming that the load being thrown will be several times heavier than the carriage, and that the rail will be angled (presumably at somewhere near 45 degrees), so the actual power output is much closer to a constant. If you use encoders, you can select the throwing range simply by setting a constant rotation speed for a PID loop, so it should easily scale down to lighter loads than its peak.

If you provide a desired maximum load and launch speed/throw range, I'd be happy to figure out the appropriate motor requirement, gear ratios, and arm lengths to achieve it.

And to repeat - I have not built this yet.

Re: Best Way to Launch unusual items?
 

I must say I am confused by the spreadsheet, then again I am not to sure what I was looking at.

Re: Best Way to Launch unusual items?
 

This is a two-linkage-plus-glide configuration to launch projectiles using a motor. Launching with a motor is usually inefficient, as the load begins at rest and ends at maximum speed. A motor produces no power at rest or its maximum speed, but produces maximum power at approximately half speed. This setup allows a motor spinning at a constant speed to apply essentially constant power to the load as it accelerates from zero to top speed.

First, set up some sort of glide with a carriage to support the load. I was thinking of bearings on a rail topped by a light basket, but other configurations can be used. For purposes of the calculations on the spreadsheet, I set this rail along the y=0 axis. (which is the top of the frame in the layout diagram). In practice, you would probably rotate the entire assembly about forty-five degrees counter-clockwise.
I then placed the output shaft of the motor/gearbox at y=-11 units and x=7 units; these numbers are the first row in the spreadsheet and can be seen as the "hub" towards the lower right in the layout.
Attached to the motor/gearbox shaft is a linkage 7 units long; this is given in the second row, and is seen as the "star" around the hub in the layout.
Finally, connecting the motor linkage to the glide carriage is another linkage 20 units long. Ths length is specified in the third row. This is constrained to start at the end of the motor linkage and end along the y=0 axis. I calculate the left end point using the end of the motor linkage and the pythagorean theorem.

Spreadsheet, main data table:
Column A is the motor linkage rotation angle in degrees. I started at -10 so I could calculate acceleration at zero, and proceeded in five degree steps through 360. As I plotted this in the layout diagram, zero is when the motor linkage is horizontal to the left, positive angles rotate the motor linkage clockwise.
Column B is rotation angle in radians, used for sine and cosine calculations.
Columns C and D are the x and y coordinates of the motor/gearbox hub, repeated from row 1.
Columns E and F are the x and y coordinates of the end of the motor linkage. These are calculated from columns C and D plus the sin and cosine of the rotation angle times the motor arm length.
Columns G and H are the x and y coordinates of the glide end of the carriage linkage, calculated from the coordinates of the motor end, the constraint that y=0, and the pythagorean theorem.
Column I is the speed. Since I'm assuming constant rotation speed, this is simply the change in Xpos. I've taken the liberty of scaling up by 10 so that the graph looks nice.
Column J is the acceleration. Since I'm assuming constant rotation speed, this is simply the change in speed from the previous angle. Again, I scaled by 10.
Column K is the power, assuming a constant inertial load. Since power is force times speed, and force is mass times acceleration, this is simply speed times acceleration. Negative power implies that the load is being decelerated. Again, I scaled, this time by 1/5 to make a pretty graph.

The Position-Speed-Accel-Power plot simply plots columns G, I, J, and K vs column A.

The main power stroke is between about 37 degrees, where the load is stationary, and 170 degrees, where the load is at maximum speed. The carriage then stops by 250 degrees (resulting in the load flying off the end), and the portion from 250 degrees back to 37 degrees is the return stroke.

Note that the y location of the motor hub and the linkage lengths were selected by a manual tuning process to produce a flat power curve during the main stroke. x=7 was selected simply so hat the x output position starts at zero at the beginning of the power stroke after I had put in the other three numbers. You can change these numbers in rows 1, 2, and 3 to try different configurations, though you will need to turn off some of the axes limits on the graphs for them to be visible.
If you find graphs with sharp kinks in them, this is a sign that you are asking for something that is not going to fit, or require excessive forces. For example, set the carriage arm length to 18 units - you will get a large spike in acceleration and power at the very low angles. If you look at the layout diagram, you can see that this is because the carriage arm becomes vertical and must reverse direction very quickly. If you were to actually build this device, the carriage would probably overshoot this point or jam.

If you get lost, the original values were: -7, 11; 7; 20.

The secondary data table (columns M through AV) are tabulations of the x and y coordinates in a format more convenient to produce the layout diagram.

Re: Best Way to Launch unusual items?
 

Typically, the best way is to find how humans thrown them most effectively and mimic that motion. There is freedom with throwing spherical objects such as catapults, "punches", or wheels. Frisbees offered a fairly simple solution where nearly everyone agreed that wheels would be the best for giving a spinning motion to allow the disk to fly. However an object such as a(n American) football, would (theoretically) need the spiral motion applied then a human throws in addition to a forward thrust as well. Personally, I don't see the spiral being enough without additional thrust being applied.

It would also be important to explore other aspects unlike the human process. Humans don't throw T-shirts with pneumatics--robots do.

Re: Best Way to Launch unusual items?
 

We used a hammer last year for throwing the big exercise balls. It was pretty powerful and worked pretty well, but you have to be really careful your holder arm doesn't get hit by it like ours always did.

Re: Best Way to Launch unusual items?
 

We used a hammer for Aerial Assist as well. This only worked because the game piece had enough give to keep pieces from breaking in the collision. If you tried using a hammer to project a tote, you'd need to put a big cushion on the hammer head or as part of the holder, or replace something every few firing cycles.

Re: Best Way to Launch unusual items?
 

We're mostly looking at hockey pucks right now, which are the same weight as the frisbee but different parameters.

Re: Best Way to Launch unusual items?
 

I think I'll just leave this here.
http://youtu.be/JQ8jGqdE2iw

(Note, I do not condone the launching of these kinds of objects)

Re: Best Way to Launch unusual items?
 

My team has usually used a wheeled shooter. The wheels we have used, however, are magical! We call them marshmallow wheels, but they are actually wheels for conveyor belts. What makes these wheels special is that they are made of a toughish rubber that when you spin with even a direct driven mini-CIM or CIM, they expand. So they sell these in 4-in diameters, but when they are spinning, i think you can get them up to 6 inches. These wheels were ideal for 2013 and 2014 because you wouldn't need suspension on the shooter to account for the give that the balls had and the Frisbee had a more consistent flight with these. I'm sure if we had gone with a tote shooter idea we would have used these wheels to shoot them onto stacks :D .

Link

Re: Best Way to Launch unusual items?
 

Which one of those did you use?

Re: Best Way to Launch unusual items?
 

I was about to ask the same thing

Re: Best Way to Launch unusual items?
 

Sorry, I must have linked the wrong thing, We used the Sure Grip Rollers, We tried the Neoprene (Black), but that doesn't expand as much as the Nitrile (white) which is what we used for the past two years.

By the way, we discovered these wheels from 2590 in Hatboro Horsham 2013, kudos to them!

Re: Best Way to Launch unusual items?
 

You could try a slingshot like a aircraft launcher

Re: Best Way to Launch unusual items?
 

Use a strong person.
It'll work until you start throwing tables, for example! :eek:

Re: Best Way to Launch unusual items?
 

Nitrile sure-grip wheels are simply awesome. Except for the price.

Hot tip! They are cheaper, and there are more bore options available from the manufacturer: http://www.fixtureworks.net/Home/Ord...path=9|0|4|2|3

Re: Best Way to Launch unusual items?
 

If you don't care about precision landing sites and have a PR team who are pros at getting landowners to let you recover your device, a High Altitude Balloon can launch any lightweight items you can dream of. A few of my colleagues are getting into this at work, and I've suggested that launch windows be every 6-1/2 weeks so we have a nice consistent set of deadlines to aim for.

It may also take longer than a single match to come back down, but depending on how good (or intentionally bad) your engineering is, you can easily fix that.

Re: Best Way to Launch unusual items?
 

Right now we're working on hockey pucks, but seeing as one years game could have a multitude of shapes the question arose.
For multiple unusual shapes what works well?
Then the argument was what's a different way to launch the pucks.

Re: Best Way to Launch unusual items?
 

If you want an unusual challenge, try to build something to throw pool noodles. Maybe you could enter it as a "robot player" in one of the human vs robot exhibition matches this off-season. :rolleyes:

Re: Best Way to Launch unusual items?
 

You should try using a pneumatic cannon, but make foam casings for what you're shooting that come off when you fire it, sort of like a shotgun shell.

Re: Best Way to Launch unusual items?
 

In my honest opinion the best way to launch unusual items it by a piston that hits it