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Unread 08-05-2011, 04:37
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Travis Covington Travis Covington is offline
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Re: off-season launcher

Quote:
Originally Posted by Tanis View Post
Yes, they are rated for water pressure. That doesn't mean that they are at a high risk for failure when using air. It simply means that they need to be tested before being used with compressed air.

As for "a plastic sprinkler valve would likely fail in the exact same way a PVC storage tank would:" Not true. PVC used as an air storage tank almost always fails at the end caps or connection points, typically due to the a failure in the cement used to join two parts. If it isn't an endpoint, then it's because there was a crack somewhere along the body. If you are operating at reasonable pressures, a PVC tank will not spontaneously explode.

I have very carefully watched every thread on CD relating to air cannons and PVC air storage. I would never use PVC to store air. However, you may notice that every single team in those threads intends to use (and many have been using) sprinkler valves. None of them have reported any problems, and no one before has ever called them out on the sprinkler valve.
I still encourage you to do further research before using a sprinkler valve. While there may not be any documented failures that you have found thus far, the associated risks should not be taken lightly. Explaining in near absolutes how something will not fail is not helping your case here, either. I do not believe you know how all PVC storage tanks fail, and also do not believe you know all of the failure modes of a sprinkler valve. Objectivity is key, and building something safe which your school, students, and team can be certain won't harm anyone is my only concern. I posted initially because it seems like many people on these forums are not taking the safety of these cannons seriously. Please do not take my posts as personal attacks, because they are far from that. Using internet forums, youtube videos, and tech blogs to determine the safety of processes, mechanisms, materials, and hardware scares me and I hate seeing corners being cut with regard to safety in an effort to save a few bucks. Please just be as cautious as you can when proceeding.
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2008-2017 - Engineering Mentor of Team 254
2001-2008 - Engineering Mentor of Team 968
1998-2001 - Mechanical Director/Driver/Member of Team 115