New wadding design and piston update - Also .wav file

Show us your pneumatic spud gun! Discuss pneumatic (compressed gas) powered potato guns and related accessories. Valve types, actuation, pipe, materials, fittings, compressors, safety, gas choices, and more.
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boyntonstu
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Fri Oct 23, 2009 12:48 pm

bump: Hoping for analysis of the last .wav file.
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Technician1002
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Fri Oct 23, 2009 2:17 pm

boyntonstu wrote:bump: Hoping for analysis of the last .wav file.
Wow, 3 downloads and no comments on the file.

Before the trigger there is a low frequency sound which the trigger event (hiss) rides on. The trigger starts at 0.130. At 0.150 there is a sudden increase in the hum, indicating the original valve vibration is back, but it lasts a cycle and a half with a valve burp at0 01670 seconds followed by one at 0.1690. I call these burps as the amplitude is way too quiet. The valve is still trying to open but the o rings appear to be sticking so it re-seats as some chamber pressure drops.

We finally get a full amplitude pressure swing that oscillates into a clipped square wave beginning at 0.730. Again the record level is way too high so the impact is showing up only as a change in the frequency of the noise. This change appears at 0.230 for a possible flight time of 0.500 seconds. It is really hard to be sure on this one. Is there a way to turn down the record volume a lot? The waveform clipping is making this difficult. A square wave is difficult to detect volume peaks due to an impact.

I will give credit to those who tried. It's not an easy waveform to measure.
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Sample of a useful recording with little clipping.
Sample of a useful recording with little clipping.
Textbook example of a cannon recording with the correct levels. There is no clipping.  Amplitude is easy to compare over time.  This is the 2 inch QDV with no projectile.
Textbook example of a cannon recording with the correct levels. There is no clipping. Amplitude is easy to compare over time. This is the 2 inch QDV with no projectile.
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boyntonstu
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Fri Oct 23, 2009 4:35 pm

Technician1002 wrote:
boyntonstu wrote:bump: Hoping for analysis of the last .wav file.
Wow, 3 downloads and no comments on the file.

Before the trigger there is a low frequency sound which the trigger event (hiss) rides on. The trigger starts at 0.130. At 0.150 there is a sudden increase in the hum, indicating the original valve vibration is back, but it lasts a cycle and a half with a valve burp at0 01670 seconds followed by one at 0.1690. I call these burps as the amplitude is way too quiet. The valve is still trying to open but the o rings appear to be sticking so it re-seats as some chamber pressure drops.

We finally get a full amplitude pressure swing that oscillates into a clipped square wave beginning at 0.730. Again the record level is way too high so the impact is showing up only as a change in the frequency of the noise. This change appears at 0.230 for a possible flight time of 0.500 seconds. It is really hard to be sure on this one. Is there a way to turn down the record volume a lot? The waveform clipping is making this difficult. A square wave is difficult to detect volume peaks due to an impact.

I will give credit to those who tried. It's not an easy waveform to measure.
First, thank you.

Sorry about the clipping.

I am almost positive that the valve vibration is due to slow opening of the valve.

However, this shot was VERY powerful nevertheless.

Not only did the marble make a hole an go through the 5/8 plywood, it went about halfway into a 3/8 plywood sheet located behind the 5/8.

I will quiet down the mic some more and make an unclipped .wav.


BoyntonStu
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