T-Shirt cannon pnuematic set ups

[skimoose]

Originally Posted by Adama

If in fact PVC is incredibly dangerous I have a few questions.

The discussion here has been only about air powered guns. Is there any greater or less danger in combustion guns? ( I'm aware that this would be disallowed on school grounds, its just a question of principle) I imagine that the lack of high pressure storage gives some what more safety though there is more of a spiking pressure affect that could counter act this.

Also on the topic of air cannons what are peoples opinions on the below link?

http://www.spudfiles.com/

I realize that it is the internet and not a well researched set of standards but one must question the danger involved if there has been a large community of people using these devices for years now. They have there share of accidents (as does any hobby such as dirt biking or snow boarding, etc) but it would seem that they only happen to people who didn't follow the well known safety practices and construction techniques established over time by the general spudding community. I guess that that if PVC were as dangerous as we are discussing then most of these people would have killed themselves by now.

This is the most reoccurring issue with air launchers and combustion "guns". PVC is extremely dangerous!!
The PSI rating printed on the pipe is for liquids NOT compressed gases of any sort. The biggest problem with PVC is that its failure, when it occurs, is catastrophic. PVC shatters into numerous sharp shards that can be propelled at dangerous levels. PVC generally will not exhibit signs of fatigue until it explodes. People have also argued that PSI is PSI, so why isn't PVC safe with compressed gas? By the very natural of solids, liquids and gases, gases will release stored energy much faster than a liquid will, even liquids can still dangerous.

As far as your logic of a lot of people using these devices and none being hurt. That is a falsehood perpetuated by the internet. I have seen posting of failures but they are few and far between because most people don't want to post their failures, only their successes, and they certainly wouldn't post if someone was injured (don't you think the lawyers would love to get their hands on that incriminating evidence). Also, in most cases these people use these devices a few times before tiring of them, or getting caught (combustion guns). They've rolled the dice a few times and lucked out. PVC failure is generally from fatigue which means each time you load and unload the pipe you stress it and each time your chances of a failure increase. Load that pipe enough times and it will certainly fail.

I personally know at least four incidents of PVC failures. Luckily, no one was seriously hurt ONLY BECAUSE OF PURE LUCK! In one case, an individual had a charges air launcher under his coat. Luckily it failed away from his body, but it completely shredded a heavy winter jacket being worn. If you saw the jacket, you'd think the person wearing it was DEAD! Pure Luck plain and simple.

Our Dewbot T-shirt air launcher is built with an all metal storage accumulator, piping, and valve system in which every component used was rated at over 150 PSI. Where we used flexible hose (after the solenoid valve) it was rated at over 180 PSI and is reinforced so that a rupture would only cause a tear in the material. The launcher tubes are made out of polycarbonate pipe which is rated at 9000 PSI and was $11/foot. That should give you some idea of how seriously we took safety when using plastic pipe, even polycarbonate.

Don't be misled by what you don't find on the internet.