SAWED-OFF RIOT GUN redone!!!

[Brian the brain]

Jugment arms...what can I say.
You didn't see what caliber I'll use, while it's metioned on the same page.
Read before you comment please.( not flaming you, don't worry)
It's going to be 2"

7 bar can NOT be compared to 40 bar.Not in the least.

I don't plan to shoot ping pong balls either.
I'll use either 2" marbles ( yes they exist, I have two ) or led bb buckshot.
Recoil has a lot to do with the projectiles weight, since action equals reaction.
Shoot a projectile with the same weight as the gun and both will achieve the same speed, in the opposite direction .The projectile will probalbly exceed the weight of a shotgun load.


I used to benchpress twice my weight ( okay it's been a year since I tried )so that might help battling recoil.
But...40 bar at 5cm bore means 785 kilograms of force on the projectile.
Or .785 TONNE!!! Launch it facing down over a pole, and you have yourself a rocket, able to lift you and yo mamma...( depending on what she weighs)
That's likely the most force of any cannon on these forums, outperforming even hybrids.( not in terms of airspeed, but pure force)

Trust me...40 bars might be a tad too much. .We'll see.
I'll take it as far as I can take.
I'm going for the most powerfull handheld possible.
I'll start construction this week

[MrCrowley]

Well just don't do what this <A HREF="http://video.google.co.uk/videoplay?doc ... 62">Guy</a> did

[CpTn_lAw]

The risk with taking you gun to even 30 bars, is that on a 2" surface, the recoil will be enormous...
i've shot twice a 2" marble...at only 7 bars. i had a bad bruise on the shoulder. I've shot 4 times D cell batery at 12 bars. i had a large bruised area over the shoulder
What you said is right, Total forces before = total forces after
But you didn't take the friction factr into account. Plus, if you gun weights say 4 kg, a 4kg projectile, even at 40 bars, would need a very very long barrel to achieve an acceptable speed, so, you would actualy loose the gun, but it would be more a big push, than a kick.

And if you manage to make a 2" piston, that resists even 30 bars...i worship thee...

[Brian the brain]

then so be it.I'll pull it off.
I've shot a 2"marble out of my brothers cannon at 7 bar.Pretty decent recoil, but it was still do-able.Feels like a kick to the leg.

The piston will consist of 8mm thick aluminium washers and a steel threaded rod.
A thick neoprene surface will seal it.
Again I emphasise I will NOT be taking this thing to it's full potential.

I can't tell you at wich point it will become too much.Only testing can prove that.All I know is, the Chappy canon ( my brothers) is one of the most powerfull cannons around, now at 3"bore.I can still take more force.
Chappy runs at about 350 kg of push, and it weighs less than a steel cannon.I want my new cannon to exceed that force by a large margin, say 500 kg of push.Testing will show if it can still be handheld by me.

[CpTn_lAw]

Woaw i always get amazed by what you do BTB...Your sawn-off riot is to me what every pneuatic shoud be. Portable, compact, powerfull, versatile. my pneumatic piston rifle has now a 8mm bore, i shoot bolts with it, and exceed 200m/s, but then again, at 15 bars, it has some recoil. A 1gram bolt gives recoil, so a 100 gram marble...i think you are prudent enough by making progressive tests, i do the same and it has never failed. Maybe pushing it to 20 bars could be possible...the future will tell. when i will be older, i'll buy myslef a metal lathe, to make great spudguns. actually, i have better interests in smaller diameters, but the principe is the same. I'm bored at using epoxy and superglue to fix leaks...

There is a system that interests me: The pre-compressed air rifle. the system is interesting and could be used to make multi shots spudguns, and high powered. That needs some investigation.
Take us aware of the advancement

[Brian the brain]

PCP airguns use a knock-open poppet valve, know as a hammer valve.
It opens a small diamter hole at high pressure.

I too have always liked smallbore.( 9-15mm)
Unfortunately, power has always interested me more.I can not find materials strong enough to make a short 15 mm gun with enough power.
It would require very high pressure.
A longer barrel would help, but I find manouvrebility ( sp?) quite important, as I have demonstrated with the sawed-off.
I think it opened up a new path for "spud" type guns.

I look forward to creating a gun that has MORE power than I can handle.
The sawed off comes pretty close to what i would call my personal perfect gun.But still I find myself wanting more power.
That's why I want to go all out with the 2"
Maybe when the recoil becomes to much I can finally stop wanting more power and focus on other improvements.

[joannaardway]

Not to be picky, but kilograms are not force - Newtons are though.

There seems to be some misunderstanding about recoil - Recoil is dependant on momentum, rather than force.

The recoil speed can be calculated with the following equation, where V is velocity, M is mass, c is referring to the cannon, p the ammo, and g the gases.

Mc*Vc = Mp*Vp + Mg*Vg

The mass of the cannon includes immedately linked masses, like your arm, and your torso if the cannon is shouldered.

The gases are normally fairly negilible, but in a high powered CO2 (because CO2 is very dense) driven cannon, they might be worth including. At high pressures, the Velocity of the gases can be estimated at the speed of sound in that gas.

After working out the recoil speed, then you need to work out the recoil energy, using:

Kinetic Energy = (MV^2)/2

Please note that the energy of the cannon's recoil will not be the same as the projectile's energy - it will be many times less.

Knowing that, the recoil distance (in metres) is found by dividing the energy of the recoil, by the resistive force on the cannon in Newtons (Usually in the region of 100 Newtons)

Most shotguns recoil 1 to 2 inches when in the shoulder, and more when from the hip. Except in very rare situations, most cannons will not injure you with their recoil.

I suggest estimating the recoil distance by following the process through, then if your estimated recoil is much more than about 10 centimetres, then you might want to consider possible problems.

[CpTn_lAw]

you could have spoken of quantity of movement. A few people writing there have a certain knowledge of physics. the quantity of movement before the reaction, or shock, equals the quantity of movement after. There is a problem though...w are speaking of vectors, so when we consider a displacement of the projecile through the barrel, with a certain direction, and the reaction of the cannon, in the opposite direction. Before the shot, the gun is totaly motionless so M(g+p)b * V(g+p)b = O
This means that M(g)a * V(g)a + M(p)a * V(p)a = O

Where (g) means gun
" (p) " projectile
" b " before the shot
" a " after the shot.

M is the Mss and V the velocity (vectorialy speaking)

A force is expressed in Newtons, but 1 N = 9,81 kg ± 0, 12 kg depending on location.

[joannaardway]

Kilograms is mass, Newtons is force - both are seperate and are not interchangable. Inches and centimetres are interchangable, but considering mass and force to be is a serious physics "faux pas".

(I must also comment that your numbers/units are the wrong way round. There are 9.81 N of force on a 1kg mass in earth's graviational field.)

As I said before, it is important to incorporate gases into the equation, because 30 or 40 bar of CO2 will contribute notably to the cannon's recoil.

Velocity is always a vector, so it has direction anyway.

I altered the equation cutting out the basic momentum explanation and requirement for negative figures. So if someone throws their figures in, then they won't need to worry about whether it's negative or not.

What I put is a very simple way of estimating recoil, without any lengthy explanations required.

[Brian the brain]

I said kilograms to make it easier to understand what kind of power we are talking about.

It doesn't really change the fact I don't know how much recoil I can take.

[mega_swordman]

That's very nifty. It looks a lot like a shotgun. I can't tell very well from the pictures, what is the trigger system you used?

[Brian the brain]

Read the entire topic before asking question please.

[jjk92]

Read the entire topic before asking question please.

i realize i am going to get the same comment(but theres eight pages) and was wondering if anyone could link me to the original riot gun i have searched and searched i must be searching for the wrong thing thank you

[joannaardway]

http://www.spudfiles.com/forums/viewtop ... 8976&#8976

This link was earlier in the topic, but it was quite well hidden.

Good to see someone actually bothering to search.

[leeeeshad]

how did you modifi the compression to make it smaller?