Pneumatic Starch Accelerator

[mexthatcan]

I made this one a few years ago, just never got around to posting it. (my first pneumatic)

Over and Under design
Chamber - 2 2"x36" inch chambers
Valve - modified solenoid Valve
Trigger - blowgun with ball valve safety
Fill valve - shrader valve
Barrel - 1.5"x51"
C:B ~ 1.8:1

bit overkill but that was kind of the point, more fun that way. I don't really plan to paint it. Its meant to be a beast, not a pretty beast. Ill paint one of my better ones.

Anyway here it is, kinda bad quality, but oh well.
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As a spud gunning enthusiast, i do enjoy things that launch/destroy all items in their path, therefore i enjoyed building this, perhaps you will too.
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[Eddbot]

that catapult is genus, it's like a trebuchet(sp?), but modified to make the action vertical, i love it!

[mexthatcan]

oh ya its fun. Its actually called a Floating Arm Trebuchet. Much more powerful than a traditional fixed axle treb. I actually made a bigger one out of 4x4's and 2x4's to hold 70lbs of counterweight. it will throw a croquet ball about 500 feet.

[bigbob12345]

Nice job
Looks like all your parts are pressure rated
But you could use a valve with a little more flow. The single sprinkler is constricting flow a little, duel sprinklers will get the job done but I would reccomend looking into piston valves or burst disks.
Nice trebuchet BTW

[mark.f]

Very nice cannon. That sprinkler valve would allow a good amount of performance from a 1-1/2" barrel, but it sounds as though the diaphragm is bouncing, signaling that something is wrong with the valve or the method in which you modified it.

Usually that sound (honking) occurs when there is too little pilot flow. Being that others have used the same type of blowgun you are using, I would say the problem would be air leaking into the pilot at a rate too fast to allow efficient actuation. Was there a guide rod in the valve originally?

[mexthatcan]

oh ya the guide rod is all still there. and you are also correct on the cause of the honking noise, i just hold down the blowgun till all the air blows out. If i just tapped the trigger, it re-seals.

[jon_89]

Do you know how far it shoots?

[Carlman]

oh ya the guide rod is all still there. and you are also correct on the cause of the honking noise, i just hold down the blowgun till all the air blows out. If i just tapped the trigger, it re-seals.

Maybe fill the eq hole and make another one but smaller, or pilot off a bigger valve.

Or even mod your blowgun for more flow (look in How-To section)

[starman]

That treb has some pretty wicked snap to it...well done!

Your pneumatic is a clean, well designed unit as well. I like the no non-sense blowgun and gage setup on the sprinkler valve. Have you found the honk problem yet...sort of took away from the shot.

Next time, get yourself some clear primer or use the Oatey cleaner in the yellow can instead of the dyed stuff.

Nice cannon!

[mexthatcan]

@jon_89- I've never actually been able to find the potato after it goes over the tree line. For reference the tree line is about 50 yards from where I'm firing and the trees are probably 1.5x as high as my two story house.

The honking issue is just simply that i choose to hold down the blowgun till the chamber is empty. If I just pressed and released the blowgun, it would re-pressurize the pilot volume and there would be no honking.

Thanks for all the comments and suggestions

[Carlman]

The honking issue is just simply that i choose to hold down the blowgun till the chamber is empty. If I just pressed and released the blowgun, it would re-pressurize the pilot volume and there would be no honking.

Thanks for all the comments and suggestions

yes but the honking means that you are not getting the full power out of the valve. tap in a 1/4" ball valve and i bet it will go away and give you more power.

[radnac]

thats awsome!!!

[metalmeltr]

Welcome to the forums radnac, I hope you enjoy the wealth of information there is here that everyone has to offer. However it would be in your best interest to read the rules before posting. It is generally frowned upon to post comments that provide no true value to a an old thread. I do not mean this as an insult it is simply forum etiquette.