Well there's a barrel for $25 from a .243 rifle that i'm looking at, I can get hold of 100 .243 projectiles pretty cheap and easy or I could even try steel 6mm BB's, no? IIRC, steel BB's are about 5.9-5.95mm (ones I have anyway) and a .243" barrel is about 6.1mm, so that doesn't seem too bad. I gue...

12 gram CO2 capsules fit pretty well in a 3/4" barrel...

[youtube][/youtube]

Still can't believe I was doing this stuff in my bedroom

Careful what you point it at, you don't want to call 911 to say someone has been injured by a flying caulk

Moonbogg wrote: ↑

Fri Jan 03, 2020 3:37 am

I love the blueprint looking design on top that follows the mouse cursor.

It does! woooow!

I wonder if PCGUY has upgraded embedded media...



HE HAS!

ALL GLORY TO PCGUY!!!

NeoSpud wrote: ↑

Fri Jan 17, 2020 3:03 am

"oh my god, I'm so old now"

Aren't we all! But hopefully, wiser, and in a better place financially...

I weigh just about 185lbs...hmm. Hey D_Hall, I'd like to apologize for my smart ass comment I made 10 years ago to you about how I thought "UHMW" should be called "UHMW" without the "PE" at the end. I had a job where people used that stuff and they called it UHMW, so I thought I was Mr. UHMW or some...

PracticallySane wrote: ↑

Thu Dec 17, 2020 6:36 pm

What is the lowest mix i can achieve 3000psi post ignition?

I guessed your chamber dimensions and simulated it in HGDT with a "closed chamber":



I needed 27x before the chamber pressure exceeded 3000 psi

Since posting i believe i have figured out my issues. I noticed that if I leave the gun sit for roughly a minute before firing it goes off reliably. I increased the chamber volume aswell. I am in the process of creating a "venturi" fuel mixing system to mix the gasses as the chamber is filled. With...

as you would have probably seen in the hybrid build section that I've had this build on the cards for a few years. well I got around to making it a reality. Its a 5m long 75mm bore hybrid utilising a class 150 4 bolt flange as a burst dics holder. the chamber is a 20litre ex-oxygen bottle, and has a...

The piston hybrid was very good. The best thing is that you built it yourself, and you made it work correctly. Total achievement!

PracticallySane wrote: ↑

Sun Dec 20, 2020 1:25 pm

Its alot more fun with success.

Too right, glad you got it sorted!

Also it is a barrel sealing piston. The "face" sits inside the barrel instead of pressing up against it. The rear oring is a "floating oring" so air passes one way to fill the chamber. It cannot flow in reverse. His drawing is very clear, which is worth ten thousand words! THANKS! :) The barrel sid...

Watch out with that. I'm thinking your tube might have a weld seam since it's just a structural steel tube, right? Only seamless tubes should be used with high pressure and only then might the calculations provide some value. You often can't see the seam unless you look closely, and even then you mi...

PracticallySane wrote: ↑

Sun Dec 27, 2020 4:37 pm

This should help

https://eicac.co.uk/Pipe-Bursting-Pressure-Calculator

With your given parameters it looks like a burst pressure of roughly 4438psi.

tks, it looks it is rated at 2393 psi .......as it is welded.....

Disaster averted? Also, you need to know the yield strength to make a calculation. Without knowing the grade of steel, assume it's the weakest stainless in existence, plus the weld seam.