|Topic Review (Newest First)|
|07-08-2019 03:30 AM|
I made one.
Mine was caved in and had a hole about the size of a dime in it.
Decided to take my own advice...
|05-27-2019 12:50 PM|
...but the safest, easiest, cheapest, quickest, most-sensible way is to just use a factory vacuum reservoir from a junkyard.
(phone app link)
|05-27-2019 12:27 PM|
You could also just use an empty one pound propane bottle.
There are adapters to adapt the filler to ordinary pipe threads.
Since you want to pull from that opening, instead of pushing into it, punch and/or drill out the center.
Or just use an adapter that pushes in and opens the fitting, like the torch head does.
You'd also have to figure out a way to plug the bleeder that is on it. That is a schraeder type valve that can be unscrewed.
Fashion a plug to go in there instead. Or just leave the schraeder in there and fill it with JBWeld.
If you could fill the bottle with water, you could weld that tiny opening, instead.
Or drill through with a small enough bit to leave plenty of 'meat' in the metal, then tap it and JBWeld a suitable screw into the threaded opening.
|05-25-2019 09:00 PM|
"The fact is that a chamber made from PVC pipe will do perfectly well as a vacuum chamber on one of our trucks. With no danger whatever. Mount it where the vacuum chamber would normally be mounted, and in the same way, and you'll be fine."
Exactly what I have been trying to say.
|05-25-2019 02:15 AM|
You have to make a chamber, to hold the pressure.
Fill that chamber with that pressure.
Then you open a valve to let the air from that chamber push the potato plug out of the barrel.
I'm not saying it is a good idea to put hundreds of pounds of pressure into a chamber made from PVC pipe. But I AM saying that people have been doing it for decades.
This, although interesting, has become a sidetrack to this thread.
The fact is that a chamber made from PVC pipe will do perfectly well as a vacuum chamber on one of our trucks. With no danger whatever. Mount it where the vacuum chamber would normally be mounted, and in the same way, and you'll be fine.
|05-24-2019 07:08 PM|
If you take that potato gun and cap the barrel with a solid cap and not a potato you will see a big explosion. Even if you drill a 1/2" hole into the barrel to allow some gases to escape. It doesn't blow with the potato in it because as the gasses expand the potato moves out of the barrel. It would be no different if you took a rifle or shotgun and plugged the end of the barrel and didn't provide a large enough hole in it for the gasses to escape and then pulled the trigger. Large boom as the barrel is destroyed by the expanding gas.
|05-24-2019 05:20 PM|
Like everything that has "flow" gas (compressed air and the like) will take the path of least resistance. In your 8oo pound example, was it 800 PSIG, or was it 800 pounds of thrust? There is a big difference. 100 PSIG can easily (in the right circumstances) produce 800 pounds of thrust. The potato in the potato gun reference is a movable object in an immovable cylinder. Pressure applied to the closed end would cause it to move rapidly. Don't stand in front of it. A closed piece of pipe (steel or plastic) will burst with enough pressure. Gasses compress making them especially dangerous, but if the pressure ratings of the pipe water or gas are not exceeded, then there is a much lower chance of a rupture. With PVC, you then get into the chemical makeup, which can seriously reduce its ability to hold pressure. Pressure is still pressure no matter what applies it, as long as the vessel is capable of withstanding the chemical makeup of the substance, there shouldn't be a problem. Provided of course you don't exceed the pressure capabilities of the vessel. For example, ASME ratings on air tanks are done with a water filled tank, then the tank is used to hold compressed air. Working pressures and burst pressures are different ratings. Working pressure (obviously) the lower of the two should NEVER be exceeded, you take your life in your hands when you do.
|05-24-2019 02:47 PM|
Makes you wonder why tons of people haven't died in the last 40 years or so, that have been making explosive potato guns. (Explosive meaning using propane or hair spray as an explosive medium, and a flame or electric spark as the detonator. And/or using very high pressures in air operated PVC spud guns...
We did the explosive kind, as kids. But they have developed some pretty sophisticated ones now. Explosive and air pressure type, both. Got whole forums dedicated to it.
And they get to some pretty high pressures. Like 800 pounds and higher. I think they choose specific kinds of pipe and fittings, but all of them can be found at Lowes...
|05-24-2019 01:13 AM|
|05-22-2019 09:32 PM|
But... PVC pipe is rated for it.
Read the pipe the next time you are in lowes or home depot.
Or just read these...
PVC Schedule 40 Pressure/DWV Pipe | Heritage Plastics | PVC Conduit | Electrical and Plumbing
|05-22-2019 06:28 PM|
|05-21-2019 04:44 PM|
|05-21-2019 01:35 PM|
Originally Posted by lexxxel View Post
|05-19-2019 02:51 PM|
In the long run I think that I would make one out of PVC, but then I like doing that kind of stuff.
Other than that it looks like it is junkyard raiding time.
|05-19-2019 02:34 PM|
How to source a new vacuum resevoir/canister?
Science Nerd Alert. 30 pounds of vacuum feels like a typical American measuring unit. Like bullet velocity per square degrees Fahrenheit. Anyway, -30 (ok -29.92) inches of mercury is an absolute vacuum which is equivalent to -14.7 psi. In metric, that would be 0 torr (mmHg)
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