SpudFiles

Cthulhu wrote:Quick question regarding pumps:
Has anyone found a pump that works by rotating a crank rather than the regular up-and-down piston that are so common?
A friend of mine built a little sheet metal "tank" and wanted me to build a pneumatic cannon for it, but the tight quarters inside make using a pump difficult and bringing a compressor impossible.

Only electric compressors have this system, the kind they use to pump air into the wheels of automobile tires. I imagine that you could build one with the features you need or use directly one of those that can be purchased. With a lithium polymer battery of good power, it would be quite compact.

These pumps tend to have a very small volume so if you're going to convert it to a hand crank, it would have to be geared up considerably otherwise you'll be cranking forever.

To be honest I think you're better off with a large paintball bottle or SCUBA tank + regulator.

Hi Jack Yes, these compressors have a reduced flow rate. I bought one and it takes a long time to fill a chamber of just 50 ml at 7 bar. Maybe a bigger one, depends on the application.

jackssmirkingrevenge wrote: To be honest I think you're better off with a large paintball bottle or SCUBA tank + regulator.

Yeah, a regulator for my paintball tank is on my list of things to buy (along with a real compressor).
Sadly since my income is based on selling my old Spudguns I run on very little cash

I would stretch the budget to something like this + car battery, otherwise you're going to be like the poor fellow cranking away inside the "Turtle":

jackssmirkingrevenge wrote:you're going to be like the poor fellow cranking away inside the "Turtle"

That's really funny because the tank my friends and I are building is pedal powered like a bike, so no matter what someone will be cranking away!

Good idea though, I'll look into those nice little pumps.

Viair is a reputable brand you should be looking at, avoid those cheaper Chinese made tire inflators.

If I use a 1" sprinkler valve for a 3/4" barrel, will that have better or worse performance than a 3/4" valve for a 3/4" barrel?

Cthulhu wrote:If I use a 1" sprinkler valve for a 3/4" barrel, will that have better or worse performance than a 3/4" valve for a 3/4" barrel?

It might be a little better, wouldn't be any less, there's no choke point in between valve and barrel.

Would anyone know how much pressure a 30g Co2 cartridge can hold?

I have a 88g co2 cartridge for the main tank, and want to use the 30g for the air chamber.

If it could hold between 200psi-300psi that would be great. 8)

CO2 is around 850psi at room temperature...300psi shouldn't be a problem for the co2 canisters.

Pay attention to everything ELSE that handles the pressure though...make sure it's up to the task.

Gippeto wrote:CO2 is around 850psi at room temperature...300psi shouldn't be a problem for the co2 canisters.

Pay attention to everything ELSE that handles the pressure though...make sure it's up to the task.

Will do and many thanks for the reply Gippeto.

Having a look inside some pressure rated sched 40 1.5" pvc and it isn't nice... kinda bumpy. Still smooth but like cellulite almost. Is anyone else's like that or did mine get contaminated? It's not a candidate for cast in place pistons/endplugs

Anatine Duo wrote:It's not a candidate for cast in place pistons/endplugs

This has always been my experience, which is why I typically would cast the body of a large syringe for a piston housing, for example for this one:

And suddenly it all makes sense.
Thanks JSR.
Reading the posts over the past few months, I have come to be able to follow the explanations, but with that illustration, now I understand the science.
It's so simple.
You could look at that as a lopsided coaxial as well.
The reason went with manufactured valves is because I was looking for a formula or recipe to follow. You know, plans of something that works; guaranteed success.

I suppose I had better finish my metal QEV build soon, 'cause I am think I want to try a few new ideas.