Launching Foam Balls from Giant Flower ...

[futnuh]

How's that for a title? ;-)

We're working on a refit of another company's design for a kids' "ball room". Looking at the attached image( also viewable at

http://www.edmstudio.com/temp/discovery/08C03-redflower.jpg)

tennis-sized light foam balls get shot through the stems of giant yellow flowers by blower fans. Some of these balls land in the giant red flower, where every 5 minutes or so a cam in the base tensions and suddenly releases the bungee membrane up above launching collected balls into the air. At least that's the idea. Unfortunately the blower fans are noisy and have filters that clog up rapidly. Meanwhile, the cam system in the base of the red flower has worn out.

We have replaced the blower fans with a compressed-air system, and built bolt-on launchers for the yellow-flowers that trigger a burst of air only when a kid puts a ball into the tube. This works beautifully.

The problem is the red flower. We experimented with a pneumatic ram and two-way valve in the base to draw and release the bungee membrane. The results are iffy at best (and only partly because we're working 12ft off the ground). The red-flower top (inverted cone) is 4' wide and not very deep. There is only about 12" of stroke and, by virtue of the inherited design, the cable entry through the base is way off-center.

We have 200psi air and, if necessary, 120V AC. Given this, what other options could people suggest for launching/flinging/tossing the accrued foam balls from the red flower?

 

[TVP]

I'll leave the physics to the others, but wanted to inquire about the worn cam system. Do you mean that the cam actually sustained excessive wear (abrasive, adhesive?) or merely that it is no longer functioning. If it truly is wear, then there may be some materials/processing considerations that could improve its performance.

 

[MadMango]

I'd get rid of the flexible membrane and install a more rigid trap/flap door to replace it, then use compressed air to force the door open. That should work like a small catapult to fling the balls out of the funnel. Make the door slightly bowl-shaped to ensure no balls get trapped.

"Art without engineering is dreaming; Engineering without art is calculating."

Have you read faq731-376 to make the best use of Eng-Tips Forums?

 

[btrueblood]

I'm seeing some duct tape around the rim of the diaphragm, is that a valid reading of the photo? Is the tape there to hold the diaphragm in place on the outer rim (replacing a failed component(s) that was supposed to retain it there? Or is the tape repairing a torn diaphragm?

 

[Gymmeh]

The First thing that comes to mind is something simular to what cycles a paint ball "marker" (politically correct)... the whole system runs off compressed air, which shoots a blast of air behind the ball, and uses a small amount to cycle the bolt, this would be on a larger scale.

 

[futnuh]

@TVP, there were a few issues with the old system including: required frequent replacement of bungees 12ft in air; off-center pull causing abrasive wear on cable and pass-through hole in red flower; axle in the cam system failed (admittedly after several years of use). Watching this thing work (before it failed), a lot of energy is expended to launch a dozen or two foam balls into the air. This made us rethink whether a membrane was the best way to go.

@MadMango, could you explain a bit more about preventing balls from getting caught underneath the flap? Also wonder if 200psi (1" tube) is enough to generate the required velocity? With a test air ram (

http://tinyurl.com/32zbc9),

the velocity on the upwards push isn't enough to launch a ball very high; we'd have to leverage this at least 2 or 3 to 1.

@btrueblood, yes, I believe that duct tape is from the repeated repairs the museum undertook to keep the edge of the membrane in place. Again, a solution that didn't require them to be up on a ladder would really be appreciated by the client. In the inset photo, you can see a bunch of balls have slipped in under the webbing.

@Gymmeh, I should explain that we want to toss all of the gathered balls at once.

 

[CPosner]

What about the potato gun pneumatic canon approach. Build pressure in a buffer container/tank. Then release the pressure with a dump valve, i.e. large diameter and higher flow ..the whole system can be run from pneumatics. Very straight forward.

With your pneumatic actuator, are you trying to use a cork gun type system?

 

[MadMango]

futnuh Depending on the rate balls from the yellow flower, you may not have to worry about a constant flow of balls to the red one, so you may not have a jamming condition to begin with. If there is a constant stream of incoming balls, a cup shaped (concave) flap might help prevent balls being trapped between the flat and funnel wall.

You may have to install an accumulator to increase the available force of your compressed air system to operate the flap. Mount it under the red flower and paint it to look like a lady bug.

"Art without engineering is dreaming; Engineering without art is calculating."

Have you read faq731-376 to make the best use of Eng-Tips Forums?

 

[futnuh]

@CPosner, we use something like this for firing the balls through the stems of the yellow flowers (

http://tinyurl.com/2yj4xt).

This is based on the Ex-Air line-vac (

http://tinyurl.com/23kjml).

Up above in the red flower though, we have a bunch of balls to be tossed out, all at once and in random directions (somewhat forward into the room center if possible).

 

[KENAT]

Might be a bit noisy but rather then an elastic membrane, could you put tension springs around the edges, a bit like a mattress or trampoline?

You could shape the 'cup' so that balls don't get stuck in the springs.

KENAT, probably the least qualified checker you'll ever meet...

 

[btrueblood]

I was going to suggest something similar to KENAT, and agree with his suggestion of a trampoline-like mechanism, perhaps with a flexible cover (simple gravity-weighted fabric, or possibly a set of hinged plastic "roof shingles") over the springs?

 

[IRstuff]

Most of the similar venues I've seen go with a ball dump, instead of a ball launcher. The kids try to launch teir balls into a big wire hopper, which opens like a claw to dump the balls down on the kids underneath. Both the Cleveland Science Center and Universal Studios Hollywood have similar setups.

TTFN

FAQ731-376

 

[HEC]

Looks like a fun topic for a change. I like CPosners sugestion of an air cannon. GEA Niro have a pneumatic hammer for powder bins that "fires" a rubber ball on to the side of the bin.

http://www.niroinc.com/html/drying/fdpdfs/pneumatic_hammer.pdf

The barrel could be replaced with a suitable diameter shallow cup for a single ball, this would sit inside a deeper cone to gather other balls around the central one.

Mark Hutton

 

[futnuh]

@HEC, without the impact plate and with a bigger barrel to accommodate the bigger ball size, it would really just be akin to launcher system used for the yellow flowers (

http://tinyurl.com/2yj4xt).

Actually suspect that the line-vac solution gets more velocity ... which still isn't enough to eject a dozen balls from the red flower top.

I like the idea of the pneumatic hammer though. If we could leverage the 200psi to get a few inches of bolt travel at high speed, this could be attached to the middle of a "speaker cone".

 

[MintJulep]

How about a continuous membrane of rubber of some type. EPDM or neoprene perhaps.

Draw a vacuum underneath, pulling it down to form a bowl and "cock". Release the vacuum to launch.

Add whistles or other pneumatic noise makers in the vacuum release line and you'll have a cacophony accompanying the ball launch.

 

[handleman]

Don't forget - there will be children in the area. If you can get some type of large (enough to hold several balls) rigid plate/flap/cup/cone moving fast enough in a couple of inches travel to lauch said balls with any kind of velocity, the sound when it reaches the end of its travel will be deafening!

 

[IceStationZebra]

Like IRStuff we have seen the ball dump idea used at OMSI (Oregon Museum of Science and Industry, Portland).

As to a constructive idea, how about a motor in the base of the flower that spins an impeller. You could experiment with the size of the blades and motor speed to get the effect you want. You could also put vanes on the top of the flow pedals to help direct where the balls go, or add a lip to help throw the balls up. You will want to avoid any sharp points that would damage the balls.

The impeller could be a simple as a disc with 2 or 3 small blades mounted near the circumference. A flat center would help keep all of the balls from being fed at the same instant, but spreading the discharge over 0.5-2 seconds.

ISZ