SpudFiles

I've just made my first combustion cannon according to the regular design

http://www.swanstrom.net/petes/shoot/sp ... pudgun.gif

But I want to increase it's performance and accuracy and most of all precision by either building a new one and modifying the design or dismounting this and changing some details.

So I wonder what parts of the cannon are responsible for different properties (speed of the projectile, force, accuracy) And what parts of the cannon to modify for the best result (add an extra chamber, increase the length of the barrel etc.

When you just have spray and prays the mix is never usually perfect so to get the mix better try using a propane metering system and a chamber fan to mixe the fual and air.

The first thing to do? Fuel metering. That will be the biggest performance improvement (unless you are using a microscopic chamber or 1cm long barrel). A proper setup can be made (search) or a ghetto setup with a syringe (search).

You could also add a fan to aid in fuel mixing and metering.

I can't really say much more unless you post some specifications or pictures of your cannon.

Nice drawing. Most of the parts for performance are a metered air fuel mix, and the addition of a spark strip instead of a single gap and addition of a chamber fan.

Hybrid Gas Gun Design Tool, a software program can help model the chamber size and other variables on performance. Tweak by modeling then build it.

When you add the metering pipe,
(through a spot with two layers like a coupling)
you'll get more power like others mentioned.(edit:echo)
But also it will probably be faster to fuel...
I recommend breech loader on the barrel for faster speed (rate of fire),
And safety (safer).

The accuracy will mostly be dependent on the ammo fired.
Course you could add a laser sight, trajectory adjustable or pendulum sight (think archery products).

Power (Strength) will be effected by ammo weight, length, diameter,
Sabot design, wadding used etc. also.

You could try a Burst-disk in a cam-lock, union or just jammed into a coupling. (Starman made some awesome combustions in showcase with BD's)

I prefer the set up with a chamber fan and large ball-valve for venting
on combustions but I haven't owned any for a while. 8)

People have covered the power thing well. As far as accuracy goes, spudtech.com sells rifled PVC barrels. As a matter of fact, I have rifled 2" and 1.5" barrels from spud tech that I never got around to using and would consider selling them at discounted prices to you. The 1 1/2" barrel is clear PVC. Each are 4ft long.

How do I increase the performance of the regular combustion

Replace the combustion chamber with a compressed air reservoir and add a valve between it and the barrel

jackssmirkingrevenge wrote:

How do I increase the performance of the regular combustion

Replace the combustion chamber with a compressed air reservoir and add a valve between it and the barrel

Cheeky sod.

Anyway...things like increasing the length of your barrel, adding a chamber fan, fuel meter and multiple spark gaps are usually the main things you can do to improve performance.

Information on all of those is found here:
http://www.spudfiles.com/spud_wiki/

jackssmirkingrevenge wrote:

How do I increase the performance of the regular combustion

Replace the combustion chamber with a compressed air reservoir and add a valve between it and the barrel

You forgot to tell him he should put epoxy all over the place.

psycix wrote:You forgot to tell him he should put epoxy all over the place.

Indeed, style! Just grab your mixing container and go crazy!

Epoxyfetish.

Once you start doing it, and it* becomes hard you can never let it go...
*The epoxy, not the other thing.

psycix wrote:Once you start doing it, and it* becomes hard you can never let it go...
*The epoxy, not the other thing.

Too right. I was testing my latest 34mm piston beast, the retaining bolt and washer blew out of the piston and it's leaking now and now I have to grind through the 5mm or so thick steel chamber to make amends :-/

Threads ftw.

Eveything others said plus, mostly metering fuel will give the biggest increase in performance for your $$$.

1. Omit the DWV elbow if you are going to really try to boost the performance.

2. Get the spark gap out'a that elbow and back near the center of the chamber.

3. Double bevel the muzzle. Most of the bevel is on the outside with less on the inside. For a 2" barrel it should be almost impossible to ram the spud.

4. If you really want a pistol grip there are ways to do it. You don't want the grip volume to be part of the combustion volume.