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Pneumatic cannon (Thumper)

Unread postPosted: Fri Nov 30, 2018 3:44 pm
Author: Olay
I thought my project would be interesting for you.

https://www.youtube.com/watch?v=OmfDpCNS-oQ&t=8s

I built it for a school project. It's intended to shoot tennis ball (at 100psi = 70meters), but anything that fits in the barrel is potentially a projectile. I tried with a coke can and it fits perfectly.

Enjoy!

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Re: Pneumatic cannon (Thumper)

Unread postPosted: Fri Nov 30, 2018 5:24 pm
Author: jackssmirkingrevenge
Olay wrote:I thought my project would be interesting for you.


Great stuff!

Rehosted your image as it wasn't showing up:

Image

Is that one of those cheap tire inflator compressors? Surprised it's up to the job to be honest, I bet it's because the Canadian winter keeps it cool!

Re: Pneumatic cannon (Thumper)

Unread postPosted: Fri Nov 30, 2018 10:51 pm
Author: Olay
Thank you for the rehost!

The compressor is from a small 2 gallons air compressor system. I picked it up at the local scrap yard, the motor had a blown fuse that I just replaced. It's surprisingly powerful for its size; It takes about 30seconds to pressurize everything at 100psi. The fan is really good at keeping the motor at operational temperature, even after 6-7 consecutive pressurization.

My end goal is to replace it with a DC motor, wire up 2 or 3 RC plane batteries in series and boost the voltage with a Dc boost converter. This would give me full autonomy and shorter pressurizing time.

Re: Pneumatic cannon (Thumper)

Unread postPosted: Sat Dec 01, 2018 8:02 am
Author: jackssmirkingrevenge
Olay wrote:The compressor is from a small 2 gallons air compressor system. I picked it up at the local scrap yard, the motor had a blown fuse that I just replaced


Ah that makes more sense.

My end goal is to replace it with a DC motor, wire up 2 or 3 RC plane batteries in series and boost the voltage with a Dc boost converter. This would give me full autonomy and shorter pressurizing time.


You might also want to consider a duct around the fan to make it even more efficient. Also, you can actuate the solenoid valve manually instead, eliminating the need for batteries for firing and likely increasing power since solenoid pilots tend to have lower flow by comparison. Basically flip the valve upside down and tap it for a blowgun valve as is typically done for sprinkler valves

Re: Pneumatic cannon (Thumper)

Unread postPosted: Sat Dec 01, 2018 11:37 pm
Author: Olay
Wow that's a clever modification! And the idea of putting a duct would help create a more laminar flow for better cooling indeed. I was actually considering replacing the solenoid with a sturdier valve capable of accepting higher pressures. Paired with a stronger DC motor I believe I could achieve that. I was aiming at around 200-300psi.

Re: Pneumatic cannon (Thumper)

Unread postPosted: Sun Dec 02, 2018 7:22 pm
Author: jackssmirkingrevenge
Olay wrote:Paired with a stronger DC motor I believe I could achieve that. I was aiming at around 200-300psi.


I'm not sure a stronger motor alone would be the solution, given that doubling the pressure will proportionally increase the strain on the pump components themselves, increasing the chance that something will fail. Fridge or AC compressors are a popular choice, though I haven't seen anyone try to run them off batteries. A cheap multi-stage pump takes a bit of effort but is another way to safely and reliably reach higher pressures.

You'll probably want to drastically reduce the chamber size too, for the size of the barrel it's more air than you can usefully take advantage of, all it does is increase pump time. Even if you keep the same total quantity of air, for example doubling the pressure but halving the volume, you will still see an increase in power.