Starting a new build

[Flounder]

I have been lurking here for awhile and decided it was time to register and try to take advantage of the collective mind for a build. I am a paintballer and planning building a wheeled launcher for Nerf Pocket Vortex rockets. The game I am building this for has some requirements I need to meet:

Blow-off safety valve (125psi or less).
Pressure Gauge (0-300psi or less).
Low Pressure inline regulator
Steel or aluminum expansion chamber rated for 3x the operating pressure
Mechanical or electrical firing safety device
Absolutely NOTHING should be drilled or tapped into single wall thickness of any pressure holding component. This includes the barrel.
Chronograph limit is 225 fps or less
Operating pressure must be 100 psi or less
No NSF-DWV fittings (PVC plumbing fittings i.e.. quarter turn valves or ball valves). All valves, fittings, etc should be NPT
Launchers must weigh at least 50 pounds, have at least a 3 foot by 3 foot front gun shield, and have a minimum overall barrel length of 5 feet

I plan to build a lightweight steel frame and ro this on 26" mountain bike tires. My goal is to go as simple as possible for the construction to try to keep it from breaking down during the game.

I am looking for ideas on the best way to build this. I want this to be a breech loader to avoid being shot while trying to muzzle load this. Any input you can provide or pointing me in the right direction would be appreciated.

Thank you in advance for your help.

[jrrdw]

All you need now is to gather the parts and build it. You all ready have in mind how it's going to be. Some builders go from the mind and some draw it up on paper first, how ever it works best for you.

Welcome to Spudfiles.

[farcticox1]

The breech could be the only tricky bit, I would build it it with a plain barrel to prove it works then add the breech load. What size are those rockets ? that will determine the barrel size. Are you running it from a HPA tank or something like that then regulating down to 100psi.
Do you have a budget in mind ?

[Flounder]

The rockets will be 2 inch diameter. I plan to use HPA regulated down to less than 100 psi.

Do you have any suggestions for what I can use for the expansion chamber?

I am trying to go low budget on this but expect to spend a few hundred before it is all said and done.

[farcticox1]

An old fire extinguisher might do nicely or an air brake chamber of an old truck ?

[Flounder]

I was digging in the garage and I found an old tank from a compressor. 6" OD 18" long and I have a 3/4 NPT bung already welded on the one end. I think that will be perfect for this build.

[farcticox1]

That sounds perfect

[jackssmirkingrevenge]

I'm guessing that with these kind of restrictions, a combustion type launcher would be out of the question? If so that's a shame because it would be much simpler to build and you could have a much more realistic cartridge fed setup, a nerf rocket stuffed into an appropriately sized tube would seal off the gas easily.

[Flounder]

Yeah combustion is out of the question unfortunate. We are looking at about 1800 people with paintball markers, 14+ tanks. and about 10 guys running around with handheld launchers. The Heavy AT (wheeled unit I am building) it the cheapest way to eliminate tanks from the front or sides. I am kicking around a few ideas for a cartridge setup next year but for this year with the limited time I have and my work schedule I am trying to go simple.

[jackssmirkingrevenge]

Have a gander at this thread for some inspiration.

[Flounder]

Looking at the compressor tank I have it is about twice the volume of the barrel. Doing some bar napkin calculations I estimate about 70 shots per scuba tank running at 60 psi. Still no idea what the actual pressure I will need to achieve the desired velocity. I have found a nice QEV from Mcmaster Carr that I have seen used on a few builds here. I ordered it this morning so I expect it any time this afternoon (those of you who have ordered from them get that joke) I hope to have some pictures to share next week of the progress.

[farcticox1]

I use McMaster Carr for work, I'm sure they employ psychic's in there sales department, you look in the catalogue and it's already shipped before you order it. Maybe they they use matter transporters

[jackssmirkingrevenge]

Still no idea what the actual pressure I will need to achieve the desired velocity

Download GGDT if you want a more empirical basis for your design before committing to the actual build.

[Flounder]

Still no idea what the actual pressure I will need to achieve the desired velocity

Download GGDT if you want a more empirical basis for your design before committing to the actual build.

That looks like a very handy tool, took me a few times to install it (forgot the "run as administrator" option) I am at a loss for the required information for the valve information. I plan to use Mcmaster Carr part number 6646K23 That I have seen used for several builds on the forum all ready. Any advice you can provide would be appreciated.

[farcticox1]

looks like a good valve