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Noise cannon for RC planes

Post questions and info about combustion (flammable vapor) powered cannons here. This includes discussion about fuels, ratios, ignition systems, safety, and anything else relevant.
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Re: Noise cannon for RC planes

Unread postAuthor: Futterama » Fri Jul 06, 2018 2:53 pm

hectmarr, thanks.

The propane pressure is 8bar and this would blow more than a pump. I would need the pump to blow into the nozzle in reverse direction with the propane feed hose detached so the dirt gets out of the system. But during all my extensive testing, this is the first time I have had a nozzle clog.

I have made a cleaning tool with some 0.3mm piano wire so I can clean another time if needed.
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Re: Noise cannon for RC planes

Unread postAuthor: hectmarr » Fri Jul 06, 2018 4:18 pm

Yes, indeed, a mechanical system can also work properly. It happens that when the airplane model is on the ground, the turbulence generated by the propeller,Lift up dust, can dirty and cover such a tiny hole. :(
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Re: Noise cannon for RC planes

Unread postAuthor: Futterama » Mon Aug 13, 2018 1:54 pm

This project is still moving forward.

The test plane can fire in the air but with a low rate of fire and sometimes not very loud, it depends a lot on the propane/air mix.

If I add a radial fan at the air intake of the cannon, I can turn all the way up for the propane and also the rate of fire, and I get really loud bangs. So this is what I'm working on right now. See this video.



I have made a really lightweight radial fan from 3D printed PLA and a small 17mm brushless motor and 10A motor controller. Total weight only 57g. And it is really powerful :D

Now that I have forced air at the intake, I'm going to try to add a reed valve and see what that does to the combustion process - I hope that it will help direct most or all combustion pressure out through the main tube and barrel outlet, and not let some of the pressure out through the intake as it does now. Hopefully this will also add to the noise level :lol:

I'm using the thinnest of my feeler gauges (0.05mm) as a reed for the initial test. I can get thin stainless steel foil from ebay in even thinner sizes if 0.05mm is too stiff.
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Re: Noise cannon for RC planes

Unread postAuthor: hectmarr » Mon Aug 13, 2018 6:35 pm

It sounds spectacular !! I like how this project progresses. :)
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Re: Noise cannon for RC planes

Unread postAuthor: Futterama » Tue Aug 14, 2018 1:22 am

hectmarr wrote:It sounds spectacular !! I like how this project progresses. :)

Thanks! Yes, the sound is getting really close to my end goal with the radial fan at the intake. This also opens up a lot of possibilities like the intake mixer can be redesigned to be way simpler as it no longer has the job of sucking in air anymore, the fan does that.
If the reed valve has a good effect, it might also allow to shorten the main tube some more, making it more flexible with regards to mounting in the plane. Not that I need it shorter for my current plane, but others might need it for theirs.
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Re: Noise cannon for RC planes

Unread postAuthor: jrrdw » Tue Aug 14, 2018 7:00 am

Will yours be as loud as these I wonder?

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Re: Noise cannon for RC planes

Unread postAuthor: Futterama » Tue Aug 14, 2018 8:03 am

jrrdw wrote:Will yours be as loud as these I wonder?


Check out the video description:
Brrrttt sound effects added in post-production just for a bit of fun
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Re: Noise cannon for RC planes

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Re: Noise cannon for RC planes

Unread postAuthor: jackssmirkingrevenge » Tue Aug 14, 2018 12:41 pm

This just keeps getting better, kudos as usual :D

Brrrttt sound effects added in post-production just for a bit of fun


... as should have been obvious from the fact that we were hearing the noise of the shell impacts as well ;)
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hectmarr wrote:You have to make many weapons, because this field is long and short life
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Re: Noise cannon for RC planes

Unread postAuthor: jrrdw » Tue Aug 14, 2018 2:19 pm

All the added in is at the end of each sequence. Listen again.
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Re: Noise cannon for RC planes

Unread postAuthor: Futterama » Wed Aug 15, 2018 2:12 am

I tested my quick and dirty reed valve yesterday and it did not give any noticeable difference in sound performance. I guess the radial fan is powerful enough alone to overcome most or all of the back pressure from firing the cannon.
I also confirmed this by comparing fan temperature with and without the reed valve, the difference was minimal so the intake flames does not reach the fan much.

The last thing I would like to test before starting the work of adding the fan to my big plane and re-designing my controller board, is the intake mixer design. On the smaller test-plane it takes up a lot of space and weight and with the fan added to supply air, the intake mixer could be a lot simpler and smaller in design, I want to test this.
Along with this test, I am also keen on testing a bigger propane nozzle (0.4mm vs. 0.3mm) now that I have the possibility to supply the air needed.

Stay tuned :D
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Re: Noise cannon for RC planes

Unread postAuthor: farcticox1 » Wed Aug 15, 2018 4:31 am

going off on a tangent a bit it would be cool if you could turn the whole plane into a speaker with one of those amplifier magidgets and just play mp3 audio files of anything you wanted, don't know if you would get the volume though :?

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Re: Noise cannon for RC planes

Unread postAuthor: Futterama » Wed Aug 15, 2018 5:04 am

farcticox1 wrote:going off on a tangent a bit it would be cool if you could turn the whole plane into a speaker with one of those amplifier magidgets and just play mp3 audio files of anything you wanted, don't know if you would get the volume though :?

That is already possible using this: https://www.mrrcsound.com/tt-25-info

But it is mainly for electric powered RC vehicles. From what I kind find, people suggest that a gas engine will drown out any sound from such devices, so I think my system is louder. It's hard to test as my sound meter only records 4 times a second, but I was actually considering to give it a try, I just forgot yesterday.
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