Calculation and sizing of pneumatic ball launchers

Hello
My personal project is to make a pneumatic ball launcher controlled via radio remote control.
The tank would be based on a 904 or 907 gas camping style gas bottle.
On this tank I would add at the bottom a valve to inflate the tank, and at the outlet an electro-pneumatic valve (3/4" or 1"?) controlled via a 12v wireless relay (radio remote control) and finally a part with cone + launcher tube in 3D printing.
The ball would be a tennis ball.
A little idea to know the speed of air ejection, see the ball or even better an estimate of the projection distance of the ball at 30-40° / ground?
Far from being a specialist in this field, I would like to estimate before I go ahead to order equipment for nothing if the calculation is not satisfactory.
Looking at some video of a pneumatic patator, I think it's playable but I would like to make sure before doing anything.
The schematic diagram:
image

Thank you in advance for any help that allows me to move forward in this project.

2 Likes

With greenhouse gases you should be able to reach the ozone layer :saluting_face:

2 Likes

bjr, see the parable of the shot in the air, what pressure in the bottle?

1 Like

'Tis the season to plant potatoes!!

Between 6 and 10 bars depending on the inflator, the pressure will be chosen according to the desired length of propulsion (15-20m approximately).

Hello, here is the beginning of the bot's answer, this can help: how much pneumatic power does it take to send a tennis ball 20m?

ChatGPT said:

To send a tennis ball 20 meters with a pneumatic system, several parameters must be taken into account such as the mass of the ball, the pressure, the volume of air, and the friction of the air. Here's a simplified estimate of how much power is needed, looking at the situation from a physical perspective.

1. Estimation of the necessary muzzle velocity

To start, let's calculate the speed a tennis ball needs to reach to travel 20 meters. The basic formula for the distance traveled under a parabolic path is:

d=v2sin(2θ)gd = \frac{v^2 \sin(2\theta)}{g}d=gv2sin(2θ)

Where:

  • ddd is the distance traveled (20 m),
  • vvv is the initial velocity,
  • θ\thetaθ is the launch angle (we will take an optimal angle of 45° to maximize the range),
  • GGG is the acceleration due to gravity (about 9.81 m/s²).

At an angle of 45°, sin(2θ)\sin(2\theta)sin(2θ) becomes 1, so the simplified formula for the velocity vvv is:

v=d⋅gv = \sqrt{d \cdot g}v=d⋅g

Let's substitute the values:

v=20⋅9.81≈14 m/sv = \sqrt{20 \cdot 9.81} \approx 14 , \text{m/s}v=20⋅9.81≈14m/s

The ball must be launched with a muzzle velocity of about 14 m/s to travel 20 meters under ideal conditions (without air resistance and without effects other than gravity).

2. Estimating the energy required

The kinetic energy EEE of a tennis ball is given by the formula:

E=12mv2E = \frac{1}{2} m v^2E=21mv2

Where:

  • mmm is the mass of the tennis ball (about 57 g or 0.057 kg),
  • vvv is the muzzle velocity (14 m/s).

Let's substitute the values:

E=12×0.057×(14)2≈11.1 JE = \frac{1}{2} \times 0.057 \times (14)^2 \approx 11.1 , \text{J}E=21×0.057×(14)2≈11.1J

So the kinetic energy required to throw the ball at this speed is about 11.1 joules.

3. Pneumatic power required

To propel this ball with a pneumatic system, you need to know how much air is needed to provide that energy. Suppose we use a compressed air tank and a mechanism that quickly releases pressure to send the ball.

The power depends on the time it takes to release this energy. If we assume that the energy is released in a fraction of a second (say 0.1 seconds), the power can be calculated by the formula:

P=EtP = \frac{E}{t}P=tE

Let's substitute the values:

P=11.10.1=111 WP = \frac{11.1}{0.1} = 111 , \text{W}P=0.111.1=111W

This means that it would take about 111 watts of power to send the ball 20 yards out in 0.1 seconds.

Conclusion

In summary, to send a tennis ball 20 meters with a pneumatic system, you would need a system that can deliver about 111 watts of power by releasing the energy over a short period of time. Of course, this doesn't take into account losses due to air friction and other factors like the efficiency of the mechanism, but it does give you a general idea of how much power is needed.

2 Likes

Hello
I don't really see what your gas bottle is for if you have a compressor with air reserve. On the other hand, you will need a mini game between the ball and the launcher (not easy with tennis balls because of the hair and baldness problems due to intensive use...)

2 Likes

The gas cylinder will be emptied and serves as a tank for compressed air. (Cheap tank since recovery)
For the ball it will be more of a hairless ball (dog ball but the Ø and weight are quite close for the estimate)

Thank you for bringing me this solution via chat GPT, I hadn't thought of it at all!
On the other hand, on the calculations, I still have a doubt with this AI! (or another)

It would be the last straw if a cat brought me the solution for the ball launcher for my dog!! :rofl: :rofl: :rofl:

3 Likes

Is it you or the dog who will be chasing the ball? Just a little training to your doggie for the trigger... :rofl:

2 Likes

To plant the potatoes, I'm a taker!!

2 Likes

In view of ChatGPT's calculation, you risk planting them at the neighbor's house!
1st calculation at 8 bars without taking into account the air resistance 8603m...
image

With a few adjustments (air drag) it seems more realistic but still seems very high, even very unlikely:
image
Lanceur.xlsx (9.7 KB)
There must be a wolf somewhere, or neglected parameters.

It's the dog but given the cat's calculation (GPT - below), I'm going to exhaust it!
For the triggering no worries, he understands very quickly! (Like master, like dog!:stuck_out_tongue_winking_eye:)

1 Like

Having downloaded your excel file, I see that the diameter of the valve passage does not intervene anywhere... :thinking:

1 Like

No, there was another calculation (more complicated with it) but the result was the same (except for a few things)
Chat GPT neglects it because if the passage is not too restrictive it apparently doesn't change much.
If someone with a non-artificial intelligence can tell me more, I'm all for it! :rofl: :rofl: :rofl:
Otherwise it will end with tests (Beware of planes with 8km range!!)

Skeptical about the calculations :thinking: , that's what I gleaned from the web.
image

1 Like

Plan to take into account the wind on Mistral days, otherwise the dog will have to jump a few hedges.

2 Likes

In the spreadsheet, I don't see any sin/cos of the angle of shooting/throwing?

1 Like

No mistral in Brittany (nor wind or rain for that matter :crazy_face:), otherwise I'm very worried about global warming! :rofl:

2 Likes

Look in projection distance, it is well taken into account with SIN(2*B6)