elad311 wrote:y did u use a soda bottle and not a pvc?
You were pretty insistent on doing the same not even a month ago. I suggest that for now, you're a little less hypocritical in your posting.
While I'm making suggestions, please drop the txt spk abbreviations like "Y" for why and "U" for you - it's only a fraction more effort to type the full words, and immediately makes you appear more intelligent. Not to mention that the forum doesn't charge by the letter.
Not everyone knows that plastic bottles are not a good material. However, they are convenient. Even I have used them before, however, at the time, my spud knowledge wouldn't have impressed even the lowest of the forum newbies, and it was some 3 years ago.
If he's only operating between 10 and 50 psi, I'm not concerned about this launcher being a safety hazard, as usually those bottles have burst pressures somewhere above 100 psi, which leaves a reasonable safety margin, and little energy (and thus little threat) in the unlikely event that it should become ground zero.
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Back to the original topic:
Next time, use of pressure rated PVC - and a better valve would do you well, but you seem to know that.
It would be lying to pretend this cannon is anything special, I've seen it's like many a time - although as far as I can tell, your construction is neat (although it is unclear if you primed the PVC joints), and neat work is always a good thing.