SpudFiles

This is my First attempt at a Soda Cannon.
After making one or 2 pneumatics i began thinking of ways i could load it without the aid of a compressor.

After purchasing a cheap bike pump and only being able to reach about 50-60psi, I abandoned that idea.

Below are images of my Soda Cannon.
I have taken the head of a an old soda stream syphon and fitted it to the end of my 1 1/4 inch chamber.(with much thread tape as the threads arent matched)
This allows for on the fly loading with Soda Bulb cartridges.
The addition of a different sized barrel also allows me to fire the empty bulb as a bullet. its not bad, the bulbs are fairly areodynamic and travel through the air well.

This chamber size holds 375m of water and has been fitted with a psi guage so we can see how much pressure is in there.
atm one bulb gets me roughly 100psi, the only variable is the syphon head is old and sometimes the valve leaks a little.

Adjustment of chamber sizes would give diff psi, or the addition of a second bulb.

close up of chamber and trigger.

looks pretty good to me.

I would make the chamber smaller, for a given mass of gas, small chamber and high pressure gives more power than large chamber and low pressure.

The numbers don't lie

well im getting 100psi out of one bulb atm.
im thinking maybe up to 200 psi would be safe?

Welcome to spudfiles :]
Are those bulbs going to be 'sustainable' in the sense that they are cheap and easily available. Its good that you reuse them as projectiles

When you say 200psi you mean two bulbs right?

frozebyte wrote:Welcome to spudfiles :]
When you say 200psi you mean two bulbs right?

Or he could cut his chamber in half, as jack suggested..

How 'bout a springload for that ballvalve? It would pump up power a LOT. Good eefffffoooooorrrrrrttt.

ive shortened the chamber and now get 150psi from one bulb.
results have been improved.

soda bulbs are available at the supermarket near me, and there not too dear.

Cent wrote:ive shortened the chamber and now get 150psi from one bulb.
results have been improved.

soda bulbs are available at the supermarket near me, and there not too dear.

Cool.

You can probably also get nitrogen bulbs for a similar price. They will give slightly better performance at the same pressure. If they're cheaper, give them ago

Only jf they're cheaper, cause the difference isn't really that much right?
How much did you shorten your chamber? half?

The springload bv as suggested by inonickname would really up that power, considered giving it a go?

frozebyte wrote:Only jf they're cheaper, cause the difference isn't really that much right?

Pretty much. Don't bother buying them unless they are cheaper. However, when you start pushing closer to the sound barrier the differences in power between gasses becomes massive. For example, in my next gun I would get up to a 300 feet per second increase by using hydrogen instead of air.

The difference is also larger with lighter projectiles.

Wow thats a big increase. Hydrogen is a lighter gas than normal air, but what if helium was used...

Im not sure how it works, dont flame me

frozebyte wrote:Wow thats a big increase. Hydrogen is a lighter gas than normal air, but what if helium was used...

Not much tends to be lighter than hydrogen :toothy10:

Generally speaking, the lighter the gas, the faster the particle speed and the higher the speed of sound.

For example air's speed of sound at room temperature is generally lower than mach, so it's hard to go supersonic with air. The lighter the gas, the easier.

I see,
sorry just started learning periodic table in chemistry.
So lighter air gives more POWER easier, no?

Cent wrote:im thinking maybe up to 200 psi would be safe?

From what I can see the weak link in your launcher is the sprinkler valve. It should be rated to around 150 psi, this doesn't mean it will explode at 200 but if you're going to go higher you should be using a metal QEV.

The lighter the gas, the easier

One thing to note is that smaller particles tend to seep through seals more easily, a launcher that might be perfectly OK with air might leak with helium for example.