High-Accuracy & High-Precision Launcher for Ping Pong Balls?

[WorldWiz]

TL;DR Summary

Looking for advice for constructing a high-accuracy/high-precision launching mechanism for ping pong balls. Accuracy/Precision needed = Hitting a fixed 0.5 cm radius target about 30 cm away.

I'm looking for recommendations for a relatively low-budget launching mechanism design for launching ping pong balls with high accuracy and high precision (able to consistently land within a 0.5 cm radius of a fixed point located about 30 cm away from the launcher). I've tried constructing a two-railed ramp out of chipboard with a single DC motor attached to a foam wheel (the type of part made for hobby cars) that functions as the ball accelerator, but unsurprisingly that didn't give me nearly the accuracy and precision I needed, likely due to both the fact that the motor was not stabilized adequately in my setup and the fact that my launching mechanism was just too inherently unpredictable in how the wheel would "catch" onto and accelerate the ball down the ramp. I know this is probably a long shot, but if anyone has any suggestions for a high-accuracy and high-precision launching mechanism, it would be very much appreciated. Thanks!

 

[berkeman]

Summary:: Looking for advice for constructing a high-accuracy/high-precision launching mechanism for ping pong balls. Accuracy/Precision needed = Hitting a fixed 0.5 cm radius target about 30 cm away.

I'm looking for recommendations for a relatively low-budget launching mechanism design for launching ping pong balls with high accuracy and high precision (able to consistently land within a 0.5 cm radius of a fixed point located about 30 cm away from the launcher). I've tried constructing a two-railed ramp out of chipboard with a single DC motor attached to a foam wheel (the type of part made for hobby cars) that functions as the ball accelerator, but unsurprisingly that didn't give me nearly the accuracy and precision I needed, likely due to both the fact that the motor was not stabilized adequately in my setup and the fact that my launching mechanism was just too inherently unpredictable in how the wheel would "catch" onto and accelerate the ball down the ramp. I know this is probably a long shot, but if anyone has any suggestions for a high-accuracy and high-precision launching mechanism, it would be very much appreciated. Thanks!

Fun project!

Sounds a bit like your previous thread, but that thread was from years ago:

https://www.physicsforums.com/threads/viable-railgun-setup-ping-pong-balls.789885/#post-4962369

Can you say if it's a related project?

Also, can you talk a bit about the challenges of firing a spherical projectile accurately? How was that addressed in the olden days of cannons firing spherical cannon balls?

And what is the additional challenge of firing such a light projectile versus air resistance? How can you think of minimizing that effect?

Finally, what other rules are there for this project? For example, do you know what a sabot is, and how the use of one might improve the accuracy of your ping ball launcher dramatically?

 

[Bystander]

https://www.google.com/search?q="at...ome..69i57.30506j0j8&sourceid=chrome&ie=UTF-8

 

[FactChecker]

Anything that would impart a spin would need to be accounted for. A sabot that @berkeman mentioned probably helps reduce any spin. You imply that it would have a primarily horizontal barrel. To minimize spin and friction, you might consider resting the ball on a net and making a paddle hit it from below with a precise velocity. A "lob" in a high trajectory might actually be more accurate than what you have described.

 

[berkeman]

A sabot that @berkeman mentioned probably helps reduce any spin.

Whoops, I meant for the sabot to perform a different function, but you are right, it looks like it's mostly a propellant-to-projectile force coupling enhancer.

But the image at Wikipedia about sabots helps to remind me how they increase the accuracy and efficiency of some rounds. To the OP -- this is why we need more information about the project rules -- can you attach anything to the pingpong balls to improve the accuracy?

 

[hutchphd]

Check this out

 

[WorldWiz]

Thanks for the quick reply. Yes this is regarding the same project I asked about before; at that time I was just brainstorming, and unfortunately since then, with school- and work-related responsibilities, I haven't progressed much beyond the drawing board aside from a simple prototype I cobbled together earlier this year (I may even have lost that with my recent move). I constructed it as I had last described it in that thread, though not 3D-printed as I had originally wanted due to cost if I were to scale up to my end goal.

As for the description of my project that you requested, I think that's fair enough. My original hope was to re-create this CGI concept:



I have a general idea for how I would want to structure everything (attached pic - full; the attached pic - single, basically shows how I failed to stabilize the motor/wheel above the ramp), and I think I'd be able to use an arduino microcontroller to make it work, but I feel like that one issue that will sink this project is the feasibility of the accuracy and precision that's needed.

 

[berkeman]

As for the description of my project that you requested, I think that's fair enough. My original hope was to re-create this CGI concept:

No comprendo.

That video seems to be about launched balls striking musical notes/bars, which is very cool. But pingpong balls do not have enough mass to do that.

What exacly are you wanting to do? If this is an art project, we can hopefully give you some ideas, but those ideas will have nothing to do with a "pingpong ball launcher"...

 

[WorldWiz]

@berkeman You'd be surprised, actually. I'd already tested a ping pong ball on a glockenspiel set, which has steel bars, and when I dropped a ball onto it, not only do I get a crisp sound, but the ball bounced exactly as well as you'd expect it to bounce against any hard, smooth surface. So I don't foresee any issues there if I were use steel glockenspiel bars as the "notes."

 

[berkeman]

Props to you doing that test. I never would have guessed that you would get good sound out of a pingpong ball striking that bar. Did you try any heavier balls to see if you got better sound? Marbles, steel bearings, billiard balls, etc.?

 

[WorldWiz]

@berkeman I also tested with rubber balls, which actually don't bounce AT ALL because the glockenspiel vibrates, and I tested with steel ball bearings, which bounce very poorly (and both of them also sound a lot worse), so I don't know if there's any good solid balls that I could use, as much as I know that the greater inertia would be probably help with accuracy and precision.

 

[berkeman]

Interesting. What is the normal striker composition for the glockenspeil? Is it like the strikers for keys in a piano?

 

[berkeman]

Also, how do you keep the balls from hitting other bars on their way out of the mechanism?

 

[WorldWiz]

@berkeman
1. I'm not familiar with what a"striker composition" is, and I'm not getting anything from google either, but I'm not sure a comparison between glockenspiel and piano keys is accurate, since glockenspiel keys intrinsically produce sound like xylophone or marimba keys, which do not require much force (only a good transfer of vibration) to produce sound, whereas piano keys have friction built in and simply act as the lever that plucks the piano string that actually produces the sound.
2. Even with my current design, the ball has a consistent trajectory on initial launch (as diagramed above) and won't hit the glockenspiel bar (I've made sure to give more than enough room between the bar and the trajectory in my current setup). The only problem is the tail-end of the trajectory, when the margin of error obviously has become more pronounced.

 

[anorlunda]

A bit of scientific research (https://duckduckgo.com/?q=glockenspeil&ia=images&iax=images) shows that the striker material for most glockenspeils is wood.

It may be worthwhile to consider wooden balls instead of ping pong balls. They have higher density, and their surfaces can be made slippery and less likely to pick up spin from the launcher.

 

[Baluncore]

Hitting a fixed 0.5 cm radius target about 30 cm away with a 4 cm diameter ball does not seem to require accuracy or precision. Atan(2.5/30) ≈ 4.75 degrees.

 

[WorldWiz]

@anorlunda I hadn't considered wooden balls before, but I can definitely see how that may work out in terms of bounce and sound. I'll definitely look into that. Thanks for the suggestion!

@Baluncore In that case, the problem I've been having must be largely due to the variable degree of spin that the ball is picking up on launch. Perhaps if wooden balls will work for bounce and sound, then they may also solve my trajectory problem too. Thanks!