Login    Register
User Information
Username:
Password:
We are a free and open
community, all are welcome.
Click here to Register
Sponsored
Who is online

In total there are 69 users online :: 6 registered, 0 hidden and 63 guests


Most users ever online was 155 on Mon Aug 15, 2016 1:40 am

Registered users: Bing [Bot], Google [Bot], Google Adsense [Bot], Majestic-12 [Bot], MSNbot Media, Yahoo [Bot] based on users active over the past 5 minutes

The Team
Administrators
Global Moderators
global_moderators.png CS

Back to PCP !

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.
Sponsored 
  • Author
    Message

Back to PCP !

Unread postAuthor: LeMaudit » Sun May 03, 2009 9:07 pm

Hi guys,

Following my Kick’n’Blow concept and after computing a few values for spring forces and playing more with GGDT, I finally concluded that a spring will never be able to reach some interesting power with the short overall length I seek for my project. So I’m back to the drawing board, with my first idea as a PCP six-shooter (or five ;-) !)

I have learned a bit about the existing chamber concepts, thanks to the great Wiki.
My idea is finally a mix with an oversized Brocock cartridge, a sort of barrel seal but with direct flow and no vent hole so I guess it is more like a Chamber seal in term of efficiency. I would like to use the Schrader valve both as an intake and as a trigger.

I designed it to be easily machinable, there’s no real difficult piece there. And I guess it can be easily oversize to fire some spuds :-D so you may find it interesting enough.

Also, I have difficulties to estimate GGDT results for potential damages :-)
I intend to fill the chambers at 135psi, which is the power my workshop compressor provides. What do you thing of those results, a 3/8 steel ball bearing at 228 ft/s and with a kinetic energy of 6.4 feet-pound. Is it serious, average or weak?

Of course, the same with a 3 or 4 foot length barrel become even more powerful, and thinking about it, it would not be the first gun that can be transform to a rifle ;-)
  • 0

Attachments
big_ammo_GGDT.gif
big_ammo_GGDT.gif (22.85 KiB) Viewed 733 times
big_ammo.gif
Colors identify yellow for brass, gray for aluminum, and black is rubber (O-rings or washers)
User avatar
LeMaudit
Donating Member
Donating Member
 
Posts: 665
Joined: Thu Apr 16, 2009 2:48 pm
Reputation: 0

Unread postAuthor: spudtyrrant » Sun May 03, 2009 9:10 pm

first comment yay, nice design its kinda like a mini toolie piston you could attach a mini qev popoff and make it full auto, again nice design, when i first saw the name it sounded like something bad but its actually something good
  • 0

User avatar
spudtyrrant
Colonel
Colonel
 
Posts: 550
Joined: Fri Jan 02, 2009 6:10 pm
Reputation: 0

Unread postAuthor: jackssmirkingrevenge » Sun May 03, 2009 9:44 pm

Reminds me of an idea I once had ;)

Looks good, but you really should consider ashock pump to go to higher pressures. 6 ft/lbs is the legal limit for air pistols in the UK, not bad in terms of power but you can do better ;)
  • 0

User avatar
jackssmirkingrevenge
Donating Member
Donating Member
 
Posts: 24225
Joined: Thu Mar 15, 2007 11:28 pm
Country: Holy See (Vatican City State) (va)
Reputation: 66

Unread postAuthor: LeMaudit » Sun May 03, 2009 10:21 pm

You sure had the same idea... or is it me that had the same... :oops: I didn't look, I swear ! :-D But very close indeed...
Did you build it?

I'm not familiar with those items: Shock pump. I read a bit about them through the forum. I am guessing they are capable of high pressure, a tiny amount at a time. Right? How much time do you think would be needed to go from 135 to say, 300psi on my 1.5 in3 cartridge?

300 psi would double the muzzle energy, and increase by 50% the velocity. Just like having a 3 foot long barrel at 135psi :-D

And 300psi + 3 foot barrel is really nasty... 30 ft*lb and 490 ft/s

I really have no clear idea about what pressure my cartridge could take. The good thing is that it I want to do more, I'll just have to pump. I'll make sure to oversize the attachments, just to be safe. How much do you think it could take, reasonably? I intend to attach the brass to the aluminium cylinder with several steel spring pins, and a 1" diameter O-ring to seal it.
  • 0

User avatar
LeMaudit
Donating Member
Donating Member
 
Posts: 665
Joined: Thu Apr 16, 2009 2:48 pm
Reputation: 0

Unread postAuthor: jackssmirkingrevenge » Sun May 03, 2009 10:30 pm

LeMaudit wrote:I'm not familiar with those items: Shock pump. I read a bit about them through the forum. I am guessing they are capable of high pressure, a tiny amount at a time. Right? How much time do you think would be needed to go from 135 to say, 300psi on my 1.5 in3 cartridge?


Have a look here (second one on the list is brilliant :D), cheap and for small chambers it doesn't take long to get to high pressure.

300 psi would double the muzzle energy, and increase by 50% the velocity. Just like having a 3 foot long barrel at 135psi :-D


For smaller calibres, higher pressures really make a difference, especially if you're limited in barrel length and chamber size.


I really have no clear idea about what pressure my cartridge could take. The good thing is that it I want to do more, I'll just have to pump. I'll make sure to oversize the attachments, just to be safe. How much do you think it could take, reasonably? I intend to attach the brass to the aluminium cylinder with several steel pins, and a 1" diameter O-ring to seal it.


If it's an all metal cartridge would say it should take 300 psi easily, even 400 if the wall thickness of the chamber is big enough. In my cartridges I was using a PVC body (with a 3.5mm wall thickness) and they take 400 psi without problems.

One word of warning which I found out with my prototypes, with pressure the cartridge tends to expand slightly, so if it's a tight fit in your breech when empty it might get stuck when under pressure.
  • 0

User avatar
jackssmirkingrevenge
Donating Member
Donating Member
 
Posts: 24225
Joined: Thu Mar 15, 2007 11:28 pm
Country: Holy See (Vatican City State) (va)
Reputation: 66

Unread postAuthor: LeMaudit » Sun May 03, 2009 10:53 pm

Thanks again for the link and advices. I do intend to make the cartridges removable, first to have at hand several cartridges on a belt maybe (hmmm... why to I think about Rambo suddenly) and also because I intend to use the gaz-ejection from the valve to turn the barrel for the next shot. So the valve will be internal. But that's another story ;-)
  • 0

User avatar
LeMaudit
Donating Member
Donating Member
 
Posts: 665
Joined: Thu Apr 16, 2009 2:48 pm
Reputation: 0

Unread postAuthor: jackssmirkingrevenge » Sun May 03, 2009 10:56 pm

LeMaudit wrote:I intend to use the gaz-ejection from the valve to turn the barrel for the next shot.


Like the Webley-Fosberry? :D
  • 0

User avatar
jackssmirkingrevenge
Donating Member
Donating Member
 
Posts: 24225
Joined: Thu Mar 15, 2007 11:28 pm
Country: Holy See (Vatican City State) (va)
Reputation: 66

Sponsored

Sponsor
 


Unread postAuthor: LeMaudit » Sun May 03, 2009 11:10 pm

Didn't know that ! I have to check for this gun, and possibly blue prints :-)
Damn... so many things to learn :-D
  • 0

User avatar
LeMaudit
Donating Member
Donating Member
 
Posts: 665
Joined: Thu Apr 16, 2009 2:48 pm
Reputation: 0

Unread postAuthor: Gippeto » Sun May 03, 2009 11:12 pm

LeMaudit, it's an interesting proposal, and definitely do-able.

I will tell you from experience though, that the o-ring on the sealing plug will depart down the barrel with the first shot. :(

Consider machining a teflon or delrin seal, and attaching it with a small counter sunk screw.
  • 0

"It could be that the purpose of your life is to serve as a warning to others" – unknown

Liberalism is a mental disorder, reality is it's cure.
User avatar
Gippeto
Donating Member
Donating Member
 
Posts: 2393
Joined: Sat Jan 19, 2008 10:14 am
Location: The Great White North...Canada eh!
Reputation: 11

Unread postAuthor: LeMaudit » Sun May 03, 2009 11:21 pm

I will tell you from experience though, that the o-ring on the sealing plug will depart down the barrel with the first shot. Sad

Consider machining a teflon or delrin seal, and attaching it with a small counter sunk screw.
_


You think so? hmmm... I think you're right. I have very little experience with O-rings. Well, machining a washer seal is not a big deal. Thanks I'll keep that in mind.
  • 0

User avatar
LeMaudit
Donating Member
Donating Member
 
Posts: 665
Joined: Thu Apr 16, 2009 2:48 pm
Reputation: 0

Unread postAuthor: jackssmirkingrevenge » Sun May 03, 2009 11:36 pm

LeMaudit wrote:Didn't know that ! I have to check for this gun, and possibly blue prints :-)


As far as I know it works like the Mateba, the recoil moves back the upper assembly and through groves in the magazine it recocks the action. I doubt a PCP will generate enough recoil to accomplish this however, I think a simple double action like most revolvers is a better idea.
  • 0

User avatar
jackssmirkingrevenge
Donating Member
Donating Member
 
Posts: 24225
Joined: Thu Mar 15, 2007 11:28 pm
Country: Holy See (Vatican City State) (va)
Reputation: 66

Unread postAuthor: i-will » Mon May 04, 2009 12:26 am

i'm planning on building that piston for my bolt action cannon but with a hammer valve.
  • 0

WHY PAY FOR IT WHEN U CAN MAKE IT?
User avatar
i-will
2nd Lieutenant
2nd Lieutenant
 
Posts: 245
Joined: Tue Jul 22, 2008 3:04 am
Reputation: 0

Unread postAuthor: Ragnarok » Mon May 04, 2009 12:39 am

jackssmirkingrevenge wrote:As far as I know it works like the Mateba.

Not quite the same. The ramping is different between the two, but they do work in largely the same manner.
And evidently, the maker of that video has got single and double action the wrong way around.

But I quite agree - recoil based reloading mechanisms are not an area at which spudguns can excel.
  • 0

Does that thing kinda look like a big cat to you?
User avatar
Ragnarok
Chief of Staff
Chief of Staff
 
Posts: 5339
Joined: Tue Dec 19, 2006 8:23 am
Location: The UK
Reputation: 8

Unread postAuthor: jackssmirkingrevenge » Mon May 04, 2009 12:47 am

Ragnarok wrote:And evidently, the maker of that video has got single and double action the wrong way around.


Italians eh :roll: :D

But I quite agree - recoil based reloading mechanisms are not an area at which spudguns can excel


It depends, large combustions for example generate more than enough recoil to eject a cartridge;)
  • 0

User avatar
jackssmirkingrevenge
Donating Member
Donating Member
 
Posts: 24225
Joined: Thu Mar 15, 2007 11:28 pm
Country: Holy See (Vatican City State) (va)
Reputation: 66

Unread postAuthor: LeMaudit » Mon May 04, 2009 7:36 am

As far as I know it works like the Mateba,


Fascinating! Thanks for letting me learn about those. I love those mechanical concepts... :-D


Well, my idea was not to have a full cocking only with the air, I'm aware it would certainly not be enough. I was planning more to have a mechanical one like a revolver, but after the firing just use the small quantity but highly compressed air that came out when I press the trigger, to store it in an additional chamber, and use it somehow when te trigger is released to turn the barrel for the next shot. If it is mounted on a ball bearing it would not need much force.

But this is clear as mud in my mind for now and I need to think more about it. This will be the opportunity for some additional drawing :-D I'm betting I need to have the pressure in that chamber low enough to let the firing be done, so this means a chamber big enough, and maybe this will not then be enough at all to activate anything.

It sure would be nice not to have the air expulsed at the moment the firing is done, to keep some accuracy in the aiming. I'm guessing the pulse of air would deviate the gun somehow. So expulsing it to the atmosphere at the trigger release is anyway a good thing IMO.
  • 0

User avatar
LeMaudit
Donating Member
Donating Member
 
Posts: 665
Joined: Thu Apr 16, 2009 2:48 pm
Reputation: 0

Next

Return to Pneumatic Cannon Discussion

Who is online

Registered users: Bing [Bot], Google [Bot], Google Adsense [Bot], Majestic-12 [Bot], MSNbot Media, Yahoo [Bot]

Reputation System ©'