It's always refreshing to see a great looking advanced combustion. Well done.

I like the military green look. Have you considered multiple spark gaps in your chamber? Such a large chamber would definitely from more than one.
I can't wait to see the damage video and watch that mule kick.

Once again ...

Welcome to Spudfiles!

Now on to your cannon... Well, it looks like it functions well.

Where's your barrel?
What sorts of things do you shoot out of it?
I'm guessing that unpainted bell reducer contains the chamber fan?
What sorts of challenges did you face along the way?
You see what I'm getting ...

1. Find the volume of your barrel of desired length
2. Multiply this by 1.5 to get the chamber volume
3. Divide this by the cross sectional area of your chamber
4. Bingo, chamber length has been found.

Now you're going to have to compensate for the irregularly shaped volume between the chamber pipe ...

If you were to go with a combustion, the C:B ratio can be anywhere between 0.8:1 (the chamber is 80% the volume of the barrel) and 1.5:1 (the chamber is 150% the volume of the barrel). It all depends if you've got a barrel or chamber volume that is fixed.

Let's say you've got a 5 foot length of ...

Also still lurking every now and then. I've got plans for this summer though, we'll see if the bank account holds up till then...

Oh, and SF will never die. It's too unique and contains an intelligent community unlike SOOO many other forums out there.

Always great works of engineering from you Joerg, keep it up. This episode was rather comical which was very fitting considering your ammo choice and launcher design. Well done.

We've already got two threads on fellow spudder locations I think. However I can't seem to find either of them. I'm sure other members will chime in with the links to them.

The two 90° elbows and the bell reducer on your chamber are definitely DWV. You can tell by the socket depth.

As far as your 3" chamber goes, if you thought it was DWV then why did you use it? If it does not read NSF-PW in red or black ink along the side of the pipe, it is unsafe. You may be ...

I would have to agree that the volume of the meter should be taken into account no matter what. On the other hand let's not forget about what causes inaccuracies in practice, not on paper.

1. Chamber and Meter irregularities. Sure you can do a fluid measurement but how sure are you that it's ...

That doesn't make sense. If you have a 20mL meter at 1 bar, that's the same amount of gas as a 10mL meter at 2 bar. You can use lower pressure, but to make up for the lower pressure you need a higher volume which ends up amounting to the same amount of gas, assuming a constant mix.

I'm aware of ...

ah.. yes of course :-).. but is it so that the less pressure u have, the more gas is left inside the measuring tube ? or are we talking about marginals not worth calculating ?

Not sure what you're asking here but it seems like you're worried that if the meter is too large it might throw off your ...

Aww, you should have went for the head! But impressive nonetheless. Pic of the new suppressor?

Are we talkin' Plywood or Particle board?

What bore size? Combustion or Pneumatic?

Is this your fist time building a cannon?

Do you know how to identify pressure rated PVC pipe and fittings?

How much money are you willing to spend?

Just a few questions for you to consider. Try and figure out exactly what you would like to do and how simple or complex you want your cannon to be ...