Ok, I did the math and I think its correct this time.For the chamber, The equation said I should use 14.94 inches of 4", if my barrel is 48 inches of 2.5". Does this seem correct to you?
Those numbers would give you a chamber/barrel ratio of 0.8 (roughly)

If you are creating an over/under ...

Also UTFSE and look for the answer yourself, you do own a ruler don't you?
UTFSE
Does that stand for: "Use The Fkin Search Engine"?

The 3 inch fan wouldnt fit even with extensive dremmeling, what and where is the biggest fan you can use in a 3 inch chamber ?
Well, any fan just a bit smaller ...

Go to http://rhettandlink.com/music/ for some good instrumentals that you can download for free. The ones that cost are less than a buck.
These guys are very cool anyway and I must give this warning: If you start looking at their videos, you will very soon subscribe to their youtube account and also ...

A fair question that I anticipated.
Without details, the references and numbers can be seen and derived by using both Bernoulli's equation and Pascal's principle.
Hmmm, I think I'll have to call Shenanigans on this one.

Not going to get supersonic, certainly not mach 2 outside the barrel.

Best ...

[quote="psycix']Nearly mach two with a 2 meter long barrel and only 1 bar pressure differential?!
Any reference?[/quote]
A fair question that I anticipated.
Without details, the references and numbers can be seen and derived by using both Bernoulli's equation and Pascal's principle.

This fits with chemistry, but it is more for a physics class:
Make a simple vacuum gun. It is cheap to make (if the school already has the vacuum), you can use it indoors, it is quite impressive with calculated muzzle velocities of nearly mach 2 (yes, that's right) and fires harmless pingpong balls ...

I would not suggest doing anything of the sort- someone will get hurt. Either from the weakend PVC or the recipient of a high velocity ball of ice.

The nifty pic that FishBoy found while skimming the internet for swimsuits (jk) is a great ide, if he is warring in a forested area. Surgical tubing or ...

I think this is a great idea!
You could easily make it just as you have drawn and conceptualized, patterning your action and off of a normal break-barrel 20 ga.
I will have to go see for myself how well the spent shell fits inside the 0.5" PVC before I go making one (I am fairly anal and it has to ...

I love that video as well. There are 2 things I noticed that were extra noteworthy:
1. The second camera shows the material on the pallet sitting to the side of the cannon. Notice the concussion moving nearly everything on the pallet quite a ways- what a blast!
2. The shrapnel and other material ...

Yup, he used the wrong sized dye as well as tried to cut too short of a length of pipe. Most machines that Lowes and HD use limit out at about 10 inches, then they don't chuck properly and you get that kind of action.

Funny; I learned how to thread pipe about 9 years ago at a HD... nobody was ...

Use a ball valve, that is simple enough. It would be even better with a sprinkler valve or QEV. Research it.

I am truly amazed and find myself with others in a jealous frenzy. I wish to express my condolences to all inanimate objects that stand in the way of this monstrous work of art. Great work, Larda.

I forgot to mention, Most Home depots have a couple coffee thermos's in the front near the doors (Usually near lumber). Looks like it's only for employees but it's not. I bring my own cup and get one when I walk in.
refill it on the way out too... Awesome.

It's funny because on my way there, is a ...

Thanks, not sure where there is a Tractor Supply Co around St. Louis though. Hell it's St. Louis, there should be another supplier around here someplace that carries SDR-21 in the proper size, we just have to find them.

Be careful with the SDR-21 you might find...not all SDR-21 1.5" is equal. I ...

Go with Pipeline Plastics. It is most likely that they don't have it on hand, but since you are near Philly I am sure there is a manufacturer close by that they can order it from. Tell them what it is for and make sure you ask for the specs of the pipe before they order it, to make sure they know ...