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Labtecpowers (soon-to-be) quick dump valve cannon

Built a pneumatic cannon? Then post it here! This section is for completed, finished cannons that you have built. Please include pictures and information.
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Unread postAuthor: Gun Freak » Tue Feb 22, 2011 5:17 pm

Labtecpower wrote:Would this be more accurate than measuring by a muzzle blast, and the projectile hitting a target?

Yes, putting the mic in the middle compensates for the time it takes for the sound to get there.
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Unread postAuthor: clemsonguy1125 » Tue Feb 22, 2011 6:09 pm

Nice cannon. How much space is there between the groove and the oring
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Unread postAuthor: Technician1002 » Tue Feb 22, 2011 9:08 pm

The cardboard chronograph will need enough space between the sheets so the sound of the first impact has diminished enough to identify the sound of the second impact.

Can you identify both impacts in this wave?
Image


Or this one?
Image
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Unread postAuthor: jackssmirkingrevenge » Thu Feb 24, 2011 5:21 am

Tech, please tell me this is short for "analyse" :roll: :D
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Unread postAuthor: Labtecpower » Thu Feb 24, 2011 6:05 am

I can't see any impacts in that one :roll:



@clemsonguy:

The distance between to O-ring and the groove is currently zero. I was about 2 mm, but it leaked too much, so I decided to fill up the groove with some rubberbands to compress to O-ring against the valve housing. Now it holds pressure very well.
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Unread postAuthor: Technician1002 » Thu Feb 24, 2011 9:35 am

That screen shot isn't mine. I'm not using Windows. Need to ask the original poster.. :D I don't have a green start button.

On another machine I use Ubuntu Studio. Here is a screen capture of one of my machines.
Image
No green start buttons for me.

Ubuntu; http://www.ubuntu.com/
Ubuntu Studio http://ubuntustudio.org/

The screen shot is from this thread;
http://www.spudfiles.com/forums/can-you-analyze-this-wav-t19369.html
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Unread postAuthor: MrCrowley » Thu Jun 16, 2011 5:32 pm

Can't believe I never saw this thread, really nice build there Labtecpower.

As for trying measure the velocity of your shots, I found audio chronographs difficult with large cannons like yours, the muzzle blast causes too much disruption unless the microphone and targets are fairly far away.

If you're really interested in measuring the velocity, a photo-transistor chronograph are much easier to use and give more consistent results. They're pretty simple and cheap to construct too.

I realise it has been some time since the last post and this post may be unnecessary but I thought I'd post in case you were still working on a chronograph.
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Unread postAuthor: Labtecpower » Fri Jun 17, 2011 2:49 am

Thank you !

I dropped the idea of an audio-chronograph, because of the trouble with searching for sound peaks, as you mentioned.

I saw that idea a year ago, when I was still in secondary school. I forgot it, because I tought it would be too difficult :D
It should be pretty easy now, as I have lessons in electrotechnics.

It shouldn't be too hard to get some phototransistors (or complete optical sensors) as I have some nice teachers at school, where I can buy them very cheap.

Thanks for waking up the chronograph project!
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