SpudFiles

jackssmirkingrevenge wrote:PCPs that go supersonic like the Airforce Condor do so with 3000 psi on tap.

Indeed. Even then, you're more likely to find that a supersonic airgun uses a spring piston, which heats the air with rapid compression, and therefore vastly changes the speed of sound in the propellant gas, making it possible to go supersonic (in the atmosphere).

I was wondering if the stability of a nail dart would be improved by using one of these ...



The shape of these screw anchors look pretty promising to me.
I don't know in which sizes they are available but I think I'm going to try it at the weekend.

You still need to add a tail to the thing. If it just looks pointy, this doesnt mean its stabilized.
Wrap a string around the end or file into the widened part at the rear, making fins.

actually, that may work. The twist in the anchor will give the dart an arrow affect. It will spiral making it more accurate, and stablize it at the same time.

I saw THIS and realized it worked just like s spring piston air rifle. Do you think this would have any benefit over a regular pneumatic spud gun if the air was driven by a piston like this? I saw this being mentioned here in the thread and figured i'd show this. It might make a fun new cannon.

Moonbogg wrote:I saw THIS and realized it worked just like s spring piston air rifle.

Not in the slightest! That's propane powered!

Ragnarok wrote:

Moonbogg wrote:I saw THIS and realized it worked just like s spring piston air rifle.

Not in the slightest! That's propane powered!

Yeah but it slams a piston to compress air. The point is that its using a piston to compress air. So do you think it would work well for a cannon? Imagine a hybrid that uses the combustion to slam a piston forward. I can't figure out if there would be a benefit beyond using just the hybrid force alone or compressed air alone.

Actually it doesn't.

The hand pumped piston has a reed valve (some kind of flappy valve anyway) which merely sweeps through the chamber, and pumps out the exhaust gases and at the same time allows fresh air plus a dose of propane in from the other side.


Edit: faster but worse spelling

Moonbogg wrote:Yeah but it slams a piston to compress air.

No, the piston is for venting the combusted gases. It plays no part in the actual firing process, and only comes into play in the reloading process.

EDIT: Darn, beaten by Hotwired by a few seconds.

oh. That sucks. But anyway, do you think it would be a good idea for a cannon!?

I always thought about using a piston for venting a chamber, but thought it would be impractical, because you'd need a large piston (expensive if fireproof), a check valve, and unless all the meter input, vent valve, and electronics were on the front ( the front of the reducer) it'd be impractical because you'd need to keep the chamber ID smooth. There's probably a way around it, because I hadn't thought into it much.


Also it'd be inferior to a chamber fan for mixing.

thanks for all the imput! i dug through a old science kit and found a balence scale. the weight of a unmodded nail that i will use is slighty over 7grams. after about 10minutes of filling down the same nail on a drill press i got a nail down to 4.5 grams while increasing the preformace of it. i have a very shallow tip that takes about 3/4in to get back to normal diameter witch is very sharp. I also filed amost all of the nail head off and tapered the back end slighty so that more of the weight was in the front of it. i also gave it some groves in the back so that the glue that will hold the tail of yarn on will stick better. i also want to harden the nail so i can penetrate things harder that wood.
do any of you have ways to harden a nail? i do have access to a torch and a propane torch thing.

in ggdt i put in a 5 gram projectile (added a little weight for the tail) and it said 1415fps. should i still expect lower than mach 1? or will this insanely light projectlile shoot faster than mach 1?

six words: Piano wire wire nut super glue 8)

i was kind of hoping for a larger diameter dart....

anyway i dont understand what piano wire is or what a wire nut is. could someone explain? pics always help!

c11man wrote:i was kind of hoping for a larger diameter dart....

anyway i dont understand what piano wire is or what a wire nut is. could someone explain? pics always help!

Piano wire goes up to the diameter as a giant blow gun dart.
It's hard like spring steel (available in hobby shops), so coat-hanger metal is a joke comparitively.

A wire nut is the plastic thing used to splice electrical wires (quite common).
The red "Buchanon" brand for example are about .68 diameter.
A blast of orange ones (smaller)(or yellow, orange, whatever) should probably fly straight from whatever bore. 8)