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C41p50 - First Build, Strict Conditions

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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C41p50 - First Build, Strict Conditions

Unread postAuthor: thatguydionysus » Fri Aug 03, 2012 7:33 pm

Here's the current scheme >=)
    General Classification
      Pneumatic Launcher
    Barrel :
    > 18" of 4" SCH 80 PVC
    > Rifled Via sliced and diced pvc pipe secured with pvc cement
    > Bore : ~3.3" (bite of about .1 on the projectile.
    Charger :
    > ~24" of 6" SCH 80 PVC
    > Contains most of the pneumatic hardware as well as the on-board Paintball Tank for use away from a compressor ^_^
    Bolt
    > ~16" of 3" SCH 80 PVC
    > Contains Toolies Piston Valve
    > Stroke of ~13"

    Primary Valve :
      Toolies Piston Valve
        Seat: 2"
        Stroke: 1/2"
    Trigger
      1/2" Pilot Valve
        Vent Time : .004sec (4msec)
    Safeties :
      Piloted Piston valve
      and
      three way ball valve

    Loading : Bolt Action
    Ammo:
      Nerf Vortex Howler :
        Diam : 3 3/8"
        Length : 12 2/5"
        Weight : 127g
    Air Supply (expected):
      48cu 3000psi Compressed Air Tank or
      90psi shop air
    Features :
      Barrel - Floating, Interchangeable, Polygonal Gain Twist Rifling
      Pneumatically actuated safety
      "on the fly" variable pressure

    WHERE YOU AT!?!(11/14/12)
    Worked out My valve problem, gonna make a prototyp then its off to the races, ciao!
    To do:
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Attachments
C41p50 v4 Solid.png
Just an overview of C41p50
C41p50 v4 Solid.png (18.86 KiB) Viewed 1579 times
C41p50 v4 Side Trans.png
Lookin at her guts
C41p50 v4 Side Trans.png (24.6 KiB) Viewed 1579 times
C41p50 v4 Proj, Trans.png
clean side view of the internals
C41p50 v4 Proj, Trans.png (13.45 KiB) Viewed 1579 times
C41p50 v4 piping.png
oh god wtf is this!?!? oh, lol forgot it looked like hell >,<
C41p50 v4 piping.png (15.82 KiB) Viewed 1579 times
test.png
Startup procedure for the launcher
Last edited by thatguydionysus on Tue Nov 20, 2012 9:28 pm, edited 17 times in total.

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Re: First Time, Strict Conditions, Lets see how it all works

Unread postAuthor: MrCrowley » Fri Aug 03, 2012 9:42 pm

thatguydionysus wrote:Ammo:
    Nerf Vortex Howler : A Foam Football with a Tail that whistles through the air made by those crazy folks at nerf.
      Diam : 3 3/8" [85cm]
      Length : 12 2/5" [31.5cm]
      Weight : 4 1/2 oz [127g]

I think you're saying that you were going to make a cannon for this 'larp' game but decided not to. Anyhow, thought I'd say this just in case:

I'm not quite sure what your intentions are but if this is a game where you throw those large Nerf Vortex Howler's at each other or something like that, you're not going to want to fire them at someone.

A projectile like that is far too big and heavy to be fired at people even from a far distance. The trouble is that if you want to fire a howler a few hundred feet or so you'd need a modest cannon for the job. The projectile may be travelling relatively slow by the time it gets to the intended target but there's the issue of someone being hit at close range, where the projectile is going pretty fast.

If this is not for shooting people, shooting at people, or shooting in an area where someone may get hit, then I apologise and we can carry on with discussion of this launcher.

Those mini-nerf footballs would be more ideal as they fit inside 2" PVC pipe quite snugly, they're relatively light-weight, and they don't require too much pressure to fire ~300'.

If you're set on shooting the larger Nerf howler's, you will have to see if they fit inside 3" PVC. If not, you might need to look at ABS pipe, aluminium pipe (thin al. conduit would do), or some other different materials. If you still can't find anything that is a good fit, you will have to use a sabot.

What kind of performance do you expect in terms of range, velocity or power? If you want to shoot these large Nerf footballs 300', you will need a valve with at least 2" porting. Such a valve would also be practical for mini nerf footballs but I personally wouldn't bother shooting anything below 1.5" in diameter; make another cannon for smaller projectiles.

Assuming a 3" barrel fits a large Nerf football, a 2.5" barrel can be used for tennis balls or soda cans, a 2" barrel for mini nerf footballs or 250ml sized energy drink cans and a 1.5" barrel for golf balls.

Semi-auto is something we can address later as the type of valve you will use depends on the performance you want.


edit: quick look shows that 3" pipe for PVC and ABS is too small and 4" pipe is too large. Try looking for pipe made from different metals as they have a greater (or different) range than most plastic pipes.
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Unread postAuthor: jackssmirkingrevenge » Sat Aug 04, 2012 1:26 am

If even an insane Kiwi thinks that you're using projectiles that are a little too big for comfort, you might want to rethink your choice ;)

I've been hit by a 2" nerf vortex at 100 fps, I can tell you it is not a pleasant experience, I don't want to imagine what it would be like with one of the larger ones weighing four times as much.

Also, if you're firing a finned projectile, rifling is completely unnecessary.

Take a look at the XM982 experimental artillery projectile (now the Excalibur round, which is f***ing awesome):

Image

The part labelled "slipping obturator", that's the part which engages the rifling on the artillery gun barrel. Since the projectile is fin stabilised and doesn't need to be spun, what happens is that the obturator is spun, but since it is not rigidly attached to the projectile, no spin is transfered to the latter.
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Unread postAuthor: thatguydionysus » Sun Aug 05, 2012 1:56 pm

Wow, already got a reply from you Crowley, gotta say I'm honored ^_^.

As far as shooting at people goes, I have absolutely ZERO intention of firing this launcher at and/or around people.
(I'm saving that for the rifle, and that's an entirely different build, and a different conversation)

That's pretty awesome jack...but the research I've done so far indicates that with the given scenario (large diam. Long Length, low ratio between the two, and obscured fins) a certain degree of spin can assist the accuracy of the launch.
I will say that i have come across information that detail rifling to be unrealistic when it comes to flechette rounds given that extremely high degrees of twist would be required.

So far my calculations put it at a twist of about 2 rotations/meter.
Plus, the addition is an easy one. and...I can admit that the look is an attractive feature.

For the valve I was planning on imitating Wolf's valve on the LawII seen Here

My current, very rough, calculations give 62m/s at 10psi

I just got sketch-up and am working on some prototype schematics. I might have em done by tomorrow night if not then...next weekend. ><

I do have access to a wide variety of piping, both in diam and material.
I actually found a supplier that has 3 3/8" ID tubing (OD 3 3/4") but I still need to figure out the rifling and such.

oh, speaking of which,
In order to create rifling I plan to take two pipes, one with a OD = ID of the other. In the smaller pipe I will cut a series of spirals down the length which will produce, effectively, several springs. after sanding down the inside of each spiral to a flat surface (yes I know that sounds weird, you'll just have to wait for the pics) I coat the exterior of the springs in glue, push em into the larger pipe and then brace with a pressure balloon(or other material to keep the spirals against the walls.
a cap over the end keeps the spirals from being pushed out.
yes, if the gluing isn't done well I risk wasting a barrel, but I'm confident I can do a proficient job.

well, thats about it, thanks for the feedback.

ttfn ttyl, and ciao!
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Unread postAuthor: MrCrowley » Mon Aug 06, 2012 4:02 am

thatguydionysus wrote:For the valve I was planning on imitating Wolf's valve on the LawII seen Here

My current, very rough, calculations give 62m/s at 10psi

I just got sketch-up and am working on some prototype schematics. I might have em done by tomorrow night if not then...next weekend. ><

I do have access to a wide variety of piping, both in diam and material.
I actually found a supplier that has 3 3/8" ID tubing (OD 3 3/4") but I still need to figure out the rifling and such.

well, thats about it, thanks for the feedback.

ttfn ttyl, and ciao!

Yeah that 62m/s seems quite optimistic at 10PSI.

Looks like that Wolf guy used non-pressure rated PVC fittings, you should give this a read :)

The valve looks like a Toolie's style piston valve. Be sure to check the links under "implementations" and also give the forum a quick search as there will be more topics on the subject.

A Quick Dump Valve would be another option, as would a normal coaxial piston valve or barrel sealing piston valve.

A 4"x3' chamber with a 2" porting barrel sealing piston valve and a 3' barrel will give you a little over 100m/s at 100PSI according to GGDT. If you want to use it at lower pressures, you might need to up the chamber size, up the porting of the valve and increase the barrel length. You can run your own simulations by downloading GGDT or you can even request GGDT simulations by having other members do them for you.

I'm sure you're starting to see how specialised the cannon will become depending on your performance requirements. If you want semi-auto, you'll have to have a smaller chamber or large compressor. The 3000PSI compressed air tank will be useful though I'm not sure what a suitable chamber size would be in regards to that; perhaps someone else can be bothered calculating that :D

A coaxial piston valve, quick dump valve, or a Toolie's valve will probably give you the most compact design; if that's what you're after. You'll be sacrificing chamber size (as the barrel will take up a good portion inside the chamber) so you'll have to use like a 5" diameter chamber if your barrel is nearly 3.5" I.D. and you'll need to be using the cannon at around 100PSI I would think.

This is really the tip of the iceberg discussion wise, we'll need more detail from you before we can get specific.


1) How important is portability? In your terms, what would be a portable cannon (one that can fit in your car, can be carried by a person, etc)?

2) What kind of performance are you looking for in terms of muzzle velocity? Anything up to 300fps should be do-able relatively easily but as you go higher, you'll have to sacrifice other parts of the design like portability.

3) What are your expectations regarding semi-auto capability? Do you want to be able to fire a projectile right after firing the previous projectile or are you fine with manual loading the projectile and waiting a short time for the chamber to be filled with air?

4) How important is versatility? We can make this cannon great at doing the job at hand but it wont be very efficient for shooting things like golf balls. In the sense that you could build a much smaller cannon for shooting golf ball-sized projectiles and get the same performance as if you stick a golf ball barrel on this cannon.

Just a few things to think over :wink:
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Unread postAuthor: thatguydionysus » Mon Aug 06, 2012 10:50 am

wouldn't even dream of using non-rated tubing. that a nice way to blow your face off.

And yup, planning to go with a toolies valve. Just didn't know what the exact name for it was.

already have ggdt, but I haven't gotten to the point where I can fill in all the information, so until then Ill have to wait.

lol, I already had a pretty good idea this was gonna be a challenge, kinda why I put that in the title =p

1) should be able to be carried across-the-back, or over-the-shoulder. could be loaded into the of a regular vehicle, maybe even with a removable barrel.

2) not actually aiming for any fps. more is better naturally.

3) as far as the semi-auto goes, I actually plan to house the system in the front barrel, or in the rear chamber of the gun, and will be added after my first iteration is done.

4) I've planned for an interchangeable barrel system in order to make the cannon much more versatile. Another way to look at it is that I'm designing it for a expected max performance, and from there I have interchangeable options to step down with.
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Unread postAuthor: Mr.Tallahassee » Mon Aug 06, 2012 3:52 pm

thatguydionysus wrote:Ammo:

Nerf Vortex Howler : A Foam Football with a Tail that whistles through the air made by those crazy folks at nerf.
Diam : 3 3/8" [85cm]
Length : 12 2/5" [31.5cm]
Weight : 4 1/2 oz [127g]
Has anyone else noticed this? Those guys at Nerf really are crazy with measurements like that! :lol:
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Unread postAuthor: thatguydionysus » Sat Aug 18, 2012 3:09 pm

Updated.
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Unread postAuthor: MrCrowley » Sat Aug 18, 2012 6:30 pm

Sorry but it would help if you put/detail the updates in a new post so we can more easily distinguish what changes you have made.
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Unread postAuthor: mattyzip77 » Sat Aug 18, 2012 9:27 pm

Specs always sound and look good but lets see the real deal!!
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Specs/explain

Unread postAuthor: thatguydionysus » Sat Aug 18, 2012 9:39 pm

Okay, as far as revisions go, I overhauled the entire set up XD so pretty much everything is different. XD

And I'm a bit particular, I don't want to go out and buy parts that I'm not going to end up using. got a limited income, so I don't want to go burning money on trash parts.

I DO plan to make the piston next weekend though.
that will complete most of the air air systems. so if that all goes well I can continue on to the complete build
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Unread postAuthor: thatguydionysus » Fri Sep 28, 2012 10:14 pm

Just a note, I didn't add them in, but there are hoses connecting the tank to the plumbing and the plumbing to the bolt....I was just too lazy to add them in on this version >,<

there are also 3 more hoses running out of the bottom to the safety pilot, the trigger pilot, and the supply gauge. (the two tees on the bottom and the 4-way to the bottom right)
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Is there a better way?

Unread postAuthor: thatguydionysus » Mon Oct 01, 2012 11:05 am

So I'm trying to build a semi-automatic charging system that uses the supply air(reservoir or continuous supply) to actuate its more complicated workings.

The idea goes something like this:

Connect air supply

adjust supply pressure

pressure actuates safety valve

adjust firing pressure

open "on" valve.

Pressure is stopped by safety valve

Projectile is loaded

safety valve is opened via pilot valve (safety pilot)

gun charges

safety valve re-engages at firing pressure

gun is fired via pilot valve (firing pilot)

Gun is prevented from re-charging via Pilot valve.

I have a system currently (see image).

But I was wondering if anyone knew of a better way?

thanks for reading!
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Unread postAuthor: POLAND_SPUD » Mon Oct 01, 2012 9:21 pm

But I was wondering if anyone knew of a better way?
hmmm let me think...

...ohh I know piston valve/QEV + DCV combo
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sarcasm?

Unread postAuthor: thatguydionysus » Mon Oct 01, 2012 9:47 pm

you just described the current configuration...
piston Valve/toolies valve is in the bolt
qev is utilized with the tee leading to the pilot and bolt from the supply
and the directional control is the three way mounted outside

or am i misunderstanding...
if so, im sorry but could you maybe be a bit more descriptive?
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