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Originally Posted by IceStorm
How could a T-Shirt ever Jam inside? And even if it did wouldn't the air still be able to pass through the T-Shirt.
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You should always design things for the worst case scenario.
99.997% of the time there aren't any 100-year-storm hurricanes in New York City. Does that mean that the structural engineers there should ignore designing their buildings to withstand 150+ mph winds? Absolutely not!
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Originally Posted by squirrel
I don't see how it could develop full pressure, one or both shirts will move as soon as pressure builds up to a few psi.
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"will move" is not the same as "should move", the latter of which is more correct in assuming the worst case scenario. The engineers behind the Tacoma Narrows Bridge thought that wind would never pose a problem to bridge design.
The levees around New Orleans weren't designed well enough to protect against a direct hit of a Category Five hurricane. Engineers knew about the problem, but political leaders thought the risks of a direct strike weren't high enough to divert billions to rectify the problem as quickly as possible.
How about if someone told you that all car accident rollovers will always happen at only high speeds, and that it is impossible for someone to flip over a car going only 10 mph? And yet,
it's been done.
The I-35 Bridge in Minnesota was known to be structurally deficient as far back as 1990 (along with design flaws), but again the powers-that-be deemed the risk to be low enough to carry on as is without spending money to fix the problem immediately.
PVC also has a design flaw in that it is very brittle, and several people here have posted in this thread with real life examples of what happens with PVC fails. The odds of an accident happening are low, just as the odds were low with New Orleans and the I-35 Bridge.
But ask yourself this: do you want to be the one responsible for making the decision of "don't worry, the risk of PVC exploding is low, so it's safe" if something does happen?
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Originally Posted by Fe_Will
For all of the posters concerned about safety:
Why don't you help this team find properly rated parts so this design can be safe, find a suitable alternative that serves the same function or, post a new design altogether...
Over half this thread is, " OMG PVC EXPLODES!!!!" It reminds me of the propeller threads...
Finding a solution > Whining about the problem
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If you search through this thread, and the dozens of similar threads here on ChiefDelphi over the past few years about air cannons, you'll find people suggesting plenty of alternative pipe materials, such as ABS, aluminum, steel, copper, brass, or polycarbonate. Of these, steel and copper fittings are extremely easy to get at your local Home Depot or Lowe's, and brass fittings can be found at most truck part stores in the Hydraulics section. All of these can be ordered from McMaster or similar online retailers and be at your school within a few days.
The reason people keep saying " OMG PVC EXPLODES!!!!" is because there are a lot of people don't believe the warnings, and keep insisting that there isn't any problems with PVC. Eventually I'll stop caring to convince these people (I haven't reached that point... yet), and if I see any thread that deals with PVC air cannons, I'll just avoid it like the plague. If these people are seriously convinced there is no danger with PVC, then nothing we write here will convince them otherwise until an accident happens, and all we can hope for is that no one gets injured in the process.