@keep_it_real (revisiting the presta valve idea) Although I am familiar with using check valves for equalization, I have never considered using a schrader valve (not sure we have presta valves in the US) for this purpose... Whether using a presta valve or a standard inline check valve it should be n...

keep_it_real, are you implying using the presta valve for both equalization and as a check valve...??? That would definitely be better than playing with bleeder sizes...

If the piston valve is actually two separate pistons I'm doubtful that you will get much pressure into the main chamber before the cannon fires without some form of equalization... My guess is that you'll have more premature launches than not... The simplest way to achieve equalization would be to u...

That's a very clean looking cannon... Nice job...

Oh, my aching head...!!! Based on the last diagram and comments by super spuder, I can see several "issues" which need to be addressed... If the "barrel" is at the top, the "chamber" is to the left, and the "pilot chamber" is to the right, then we can assume the following... Yes, it is a chamber sea...

I hate using the word "maturity" so I'll just say that there seems to be a lack of "manners" throughout the forums... I don't know if it's spring fever or piss poor parenting but I know I'm fed up with how everyone thinks they can mouth off and belittle peoples efforts... If this was to go on in my ...

Like Orpackrat said, just test fire it till it's empty... No need for physics or speculation that way... Reminds me of a guy who came to a bonfire party one night that had a compulsive question all night long... Everything he saw brought the question, "Will that burn in the fire?"... Whether it was ...

No, it won't. The force pushing the piston onto the barrel is exactly balanced by the force pushing on the barrel from the opposite side of the elbow. As a thought experiment, think of it as a vacuum in the barrel pulling on the piston. The physics are the same. Just like there's no force dragging ...

I don't know why I even bother trying to help you dumb-shits out...!!! Who the hell would simply drive a nail into concrete without having it first go through wood... Start searching the internet and find out the real facts and you'll find that I was, in fact, correct... I'm a fully grown man, not s...

Very nice gun... The only thing I see as a potential performance issue is that you only have a C:B ratio of 1.61:1 which is somewhat marginal... But, hey, if it works that's all that matters...

I think pneumatic nail guns have already been patented... A quick Google search located one at http://nailgundepot.com/shop/catalog/Grex_2564_Concrete_TNailer_5_8_to_21_2-p-26762.html which states in the details that it works on concrete, and costs less that $300... You can also get concrete nails f...

Chamber Volume divided by Barrel Volume should be in the range of 2:1 to 4:1 for optimal performance... Volumes are calculated using the following formula...

Volume = ((Inside Diameter / 2)^2 * 3.1416) * Length

Mr.Russ wrote:Is that where they got I'd 'tap' that from?

Yes, as in "screwing male part into female female part"... Not be be confused with "reaming"... But considering that this is a wholesome family oriented site - never mind...

Rather than simply using aluminum foil for the burst disc you could use disposable aluminum baking or roasting pan foil... Most discount stores sell sets of them for about a dollar... It's halfway between aluminum foil and aluminum can in weight... Milk jug plastic is way too tough to use for burst ...

Sometimes it's more about the fun of building and playing than it is about looks and ultimate performance... Nice gun... Reminds me of my youth when I would build any of a number of motorized contraptions over the course of a weekend or two... I'd build like crazy until they'd go fast but would neve...