"In the world of spuds today"

[jimmy101]

Due to the physics involved in a hybrid, air is too dense to provide velocities very much above the speed of sound.

Though given the temperature dependence of the SOS (and the near independence of the SOS on density), the SOS inside a hybrid is a lot higher than ~300m/s (1100ft/sec)

SOS in air at 700C is about 2x that in air at 20C.

[HACKERZLORD007]

Hey Guys ,

Im got a little doubt abt spud guns and all so just wanted a bit of help.....

How much pressure approximately does a hybrid cannon generate? and is it possible to build a pneumatic cannon which can beat a hybrid cannon in performance and muzzle velocity?

Help Would be appreciated!

CHEERS

[jackssmirkingrevenge]

How much pressure approximately does a hybrid cannon generate?

The accepted wisdom is approximately 100 psi per mix number, though this is a very general rule of thumb. HGDT is a more educated way of guessing

and is it possible to build a pneumatic cannon which can beat a hybrid cannon in performance and muzzle velocity?

How long is a piece of string?

You can always build a more powerful pneumatic, but chances are it will be bigger and more complex than the equivalent hybrid - and if you want high supersonic velocity, pneumatics are limited by physics well below 2000 feet per second.

[MrCrowley]

I was wondering if there was any way to build a pneumatic gun which could either match the performance and muzzle velocity of a hybrid gun

Due to the physics involved in a hybrid, air is too dense to provide velocities very much above the speed of sound.

With heavy dense projectiles air does fine as the heat of combustion is relatively short in duration.

With lighter projectiles, an air cannon won't match a hybrid.

It depends on what the construction of both is, and what mix the hybrid is running at as compared to the pressure the pneumatic is running at. But... if I were to have two identical builds, and run them as close to failure as I felt comfortable, the hybrid would best the pneumatic.

If you're trying to beat out a hybrid with a pneumatic, we may or may not be able to help. We'd need more information.

Though given the temperature dependence of the SOS (and the near independence of the SOS on density), the SOS inside a hybrid is a lot higher than ~300m/s (1100ft/sec)

SOS in air at 700C is about 2x that in air at 20C.

and is it possible to build a pneumatic cannon which can beat a hybrid cannon in performance and muzzle velocity?

How long is a piece of string?

You can always build a more powerful pneumatic, but chances are it will be bigger and more complex than the equivalent hybrid - and if you want high supersonic velocity, pneumatics are limited by physics well below 2000 feet per second.

is it possible to build a pneumatic cannon which can beat a hybrid cannon in performance and muzzle velocity?

_______________________________

"how do i increase the velocity of my pneumatic gun....it has a 30 cubic inch chamber.....do i increase the chamber volume or do i use higher pressure....(current pressure: 100-150 due to 12 v compressor)????

Usually with pneumatics, increasing the barrel length or pressure would increase velocity.

Download GGDT (google search for it if you don't know what it is) and plug your cannon's parameters in and see what it says. It's a program for modelling cannons and is dead simple to use. Just read the FAQs on the website.

An hour later...

just wanted to confirm how i could increase the muzzle velocity of my pneumatic rifle ????

Should i try increasing the chamber volume or should i try increasing the chamber pressure???
(Currently running 30 cubic inches at 150 psi)

Help Needed......thnx!!!!
CHEERS

What is most efficient depends on the barrel. How long barrel u have and what is the diameter at the barrel?

Yeah we need more specfications like barrel length, chamber length/diameter, valve...

Both will do it, but I'd suggest increasing pressure since that's usually easier, but not if you'd be pushing the pressure rating on components.

Increasing chamber volume is effective up to a point, after that could can double the volume and only get a 1% increase in velocity. Increasing pressure on the other hand should give a roughly linear increase in power.

Download Gas Gun Design Tool and have a play before cutting.

Then increased chambervolume wont make any noticable difference

Three days later...

I recently started spudding as a hobby and i started off by making a pneumatic spud. I made one with totally galvanized fittings and pipes. My gun has a 30 cubic inch tank and a half inch bore! Well i was wondering how i can improve the range and velocity of my air gun? Should i use a bigger chamber or should i increase the pressure? (Current Pressure - 150 psi)?? I can shoot a double a battery a good 70-100 on abt 150-160 psi but i want like about 200 mts range and abt 500+ fps...so wht shd i do to improve my gun performance to this standards???? NEED HELP!!!

Again: http://www.spudfiles.com/forums/viewtop ... tml#320623

HACKERZLORD007,

PM me. Not sure why you posted this twice (as well as PMing me and asking me the same question).

Do your own research, you have been given a wealth of information from several members, more than enough to hit the ground running. I don't want to see you asking this question again.

This guy has a habit of posting his questions multiple times in multiple threads that are not his nor relevant to his questions while managing to ignore a majority of the information supplied and answers to his questions. I've shot a PM off to him so while I find out what the deal is, you might want to save your breath rather than answer his questions.

[Labtecpower]

Shot a water bottle today.

[youtube][/youtube]

You can hear me breathing, because I just had a 3 min workout to pressurize the air chamber with a bicycle pump

I also got a nice frame:



The whole garden was covered in potato pieces after this

[Labtecpower]

sorry for double posting

I want to make a large hybrid, so I wanted to practice some with fueling and igniting.
I made a crude and ugly version of the hybrids JSR makes.

The whole thing. Don't pay attention to my crappy epoxy skillz



Fill valve close-up



Internals with spark gap



When the epoxy is fully hardened, I will put in the burst-disk holder. It's an electrical connector I got from school. It is made from plastic, but I have some stainless steel versions lying around.

[saefroch]

WOW. That still is picturesque.

I'm familiar with the workout. I recommend a two-stage pump or an electronic compressor or some sort.

[Labtecpower]

I'm pretty happy with it!

Also, a compressor isn't necessary, It's healthy to be active

[DYI]

ITWOSY: ten hours of work and five pounds of insulation later, the capacitor bank can now be charged to ~14kJ at 24kV without any hissing, arcing, or destruction of multimeters. How well the rest of the equipment in the circuit fares at these discharge energies will be determined in the very near future...

[jackssmirkingrevenge]

I want to make a large hybrid, so I wanted to practice some with fueling and igniting.
I made a crude and ugly version of the hybrids JSR makes.

Haha excellent!

Some objections:

- what's the screw for? If it's for filling, You could just do it through the burst disk holder.

- your spark gap is a little large, what mixes were you planning on going to and with what ignition source?

[ramses]

ITWOSY: ten hours of work and five pounds of insulation later, the capacitor bank can now be charged to ~14kJ at 24kV without any hissing, arcing, or destruction of multimeters. How well the rest of the equipment in the circuit fares at these discharge energies will be determined in the very near future...

So where was it arcing? Or did you just say "screw it" and pot all the terminals?

[Crna Legija]

ITWOST, I started making a hybrid, just to see if i can get the mix right. If I do I'd like to start on a 3/4 or 1'' tee piston hybrid.


bit of a crappy epoxy job, didn't have enough to get a nice glassy finish on the end lol but theirs nearly 20mm of it there.

[Gun Freak]

ITWOST... After the original on/off switch wore out on my bench grinder, I searched for a replacement, only to find out that a replacement switch costs 35 dollars, half the cost of a new grinder. So I bought a 4$ toggle switch at home depot and fashioned a mount out of plastic (using the bench grinder with the switch haning off 8) ). I'm happy with it

[mattyzip77]

Good job and good idea!!! You could have even rigged it so you could just use the plug to turn it on and off!! You probably knew that though, but maybe not.

[irisher]

ITWOST: My 1 lb bag of military surplus flechettes arrived. It is quite fun against plywood.