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Paint sprayer vs pressure washer

Post about things you have launched or thought about launching. Also post about various materials used for building cannons. No posts about explosive projectiles!
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Paint sprayer vs pressure washer

Unread postAuthor: daccel » Thu Feb 05, 2009 1:04 am

I rediscovered this paint sprayer gun today. Long story short, it's now an extra after it stopped working last summer - and ready for spud gun use :D.

It's a titan lx-80, or some earlier version thereof. Here is a diagram.

I pulled apart a pressure washer gun for comparison. It appears to have a 1/4" seat (minus the area of the 1/8" pin), whereas the paint gun has a 1/8" seat but full flow. That works out to approximately 1/3 the area.

However, the paint gun has some advantages for modification because of the valve design. I'd have to do some more precise measurements but it looks like you could remove the spring and replace it with an air spring behind, to create a piston pneumatic or piston hybrid.

The handle also seals with some sort of plastic washer against the body, which would make a great burst disk holder.

Oh yeah, and it's rated to 3600 psi 8). 30x hybrid anyone?

Any other ways to use it you guys see?
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Unread postAuthor: Lentamentalisk » Thu Feb 05, 2009 1:10 am

I don't follow how you plan on using a paint sprayer to make a 30x hybrid...
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Unread postAuthor: daccel » Thu Feb 05, 2009 1:23 am

Like so. (Worst paint drawing ever, but you get the idea)
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Unread postAuthor: Lentamentalisk » Thu Feb 05, 2009 1:25 am

Assuming the surface area ratios are perfect, then you could be alright. Keep in mind though, that you won't get a very great result unless the "air spring" side of the piston has proximately 8-9 times the surface area of the chamber side.
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Unread postAuthor: daccel » Thu Feb 05, 2009 2:37 am

For your viewing pleasure - and because I like macro pics.

Going by the mark on the end of the piston, it appears to seat at 1/8". The o-ring is 13/32". So 10x, which is pretty close to your ratio.

Where does that ratio come from? Is it because it won't open fast enough if there isn't enough surface area? But won't that increase to the full diameter as soon as the seal cracks open? Or do you mean it will be harder to get sufficient pressure in the air spring?

By the way, HGDT predicts 2100 fps with a .177 bb :). And an airsoft bb will pull 250,000 g's accelerating :shock:.
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Unread postAuthor: Lentamentalisk » Thu Feb 05, 2009 2:55 am

well that number was assuming that the same fuel/air mix (or at least the same pressure) would be behind the piston, as on the chamber side of the piston. That means that during combustion, the valve would not crack open until the chamber side reached a pressure 8-9 times higher than the uncombusted gases. Important to note is that the peak combustion pressure of ideally mixed propane and air, is an additional 85psi or so.

Gah! I messed up the numbers! you don't want it to be over 6x the surface area, otherwise it won't open.

However, if that section is isolated, as it appears to be with the o-ring and all, then you just need to figure out the desired cracking pressure.
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