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 70 users online :: 4 registered, 0 hidden and 66 guests


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

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

The Team
Administrators
Global Moderators
global_moderators.png CS

Gas Bolt Action Airsoft Gun

This area is for the discussion of BB or airsoft sub machine guns, and or other small arms such as pellets.
Sponsored 
  • Author
    Message

Gas Bolt Action Airsoft Gun

Unread postAuthor: Binary Blue » Fri Jan 13, 2012 12:02 am

Can you guys please check if this design is sound in theory?
Image

It's based on Antonio's design located here:
http://www.spudfiles.com/forums/viewtopic,p,152862.html#152862

I'm going for a bolt action gun, so it's not going to be automatic and there's no parts that need to be moved by air pressure.

Thanks in advance.
  • 0


Binary Blue
Specialist
Specialist
 
Posts: 40
Joined: Thu Sep 01, 2011 6:37 pm
Reputation: 0

Unread postAuthor: jackssmirkingrevenge » Fri Jan 13, 2012 12:47 am

Looks good on paper, but some gripes:

- you're going to need fairly high pressure to make that "small burst of air" give a significant impulse to the projectile, I expressed a similar doubt in Ant's original thread. Still if it's for airsoft purposes and you don't need that much velocity it should not be an issue.

- pushing on the valve head with a plastic BB sounds like it will be putting significant strain on the projectile, make sure the tip of the head is well rounded.
  • 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: Binary Blue » Fri Jan 13, 2012 12:59 am

Thanks jack.

Would around 100 PSI be enough?

I can always increase the length of the stem sticking up into the barrel to increase the amount of air even though more air would be used per shot.

Also, how would you recommend rounding the head?
Would a file be good enough?
  • 0


Binary Blue
Specialist
Specialist
 
Posts: 40
Joined: Thu Sep 01, 2011 6:37 pm
Reputation: 0

Unread postAuthor: jackssmirkingrevenge » Fri Jan 13, 2012 1:09 am

Binary Blue wrote:Would around 100 PSI be enough?


For skirmishing, probably.

I can always increase the length of the stem sticking up into the barrel to increase the amount of air even though more air would be used per shot.


You can start with a long stem and shorten it to "tune" it. More power needs more air, there's no two ways about it ;)

Also, how would you recommend rounding the head?
Would a file be good enough?


I suggest clamping a power drill in a bench vice and using it as an improvised lathe, you'll get faster and more consistent results.

How do you intend to put it together in terms of materials? I see a lot of epoxy being involved...
  • 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: Binary Blue » Fri Jan 13, 2012 1:31 am

The air reservoir won't be attached to the barrel like my picture shows. I'm thinking of something more like this:

Image
  • 0


Binary Blue
Specialist
Specialist
 
Posts: 40
Joined: Thu Sep 01, 2011 6:37 pm
Reputation: 0

Unread postAuthor: jackssmirkingrevenge » Fri Jan 13, 2012 1:39 am

A note about the stem seal, if you make it like you drew it what will likely happen is the attached, the stem will move down but air pressure will keep the o-ring sealed against the port and no air will come out.
  • 0

Attachments
careful.PNG
careful.PNG (33.97 KiB) Viewed 2158 times
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: Binary Blue » Fri Jan 13, 2012 1:45 am

Yeah, there should be a hole around the grey stem in the green PVC end cap part. I just forgot to draw it in.

Fixed:
Image
  • 0


Binary Blue
Specialist
Specialist
 
Posts: 40
Joined: Thu Sep 01, 2011 6:37 pm
Reputation: 0

Sponsored

Sponsor
 


Unread postAuthor: jackssmirkingrevenge » Fri Jan 13, 2012 1:53 am

Better :)

How big is your air reservoir, and how many shots do you expect from it? 100 psi is not much for a repeater, albeit a small one.
  • 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: Binary Blue » Fri Jan 13, 2012 2:03 am

My air reservoir will be made of 3/4 in PVC pipes and fittings. I haven't determined the exact size, but I know it won't be that big. It's relatively low pressure for now, so I don't expect much. I'd be happy with 1-20 shots per fill.

I'll probably increase the pressure once I make the design work.
  • 0


Binary Blue
Specialist
Specialist
 
Posts: 40
Joined: Thu Sep 01, 2011 6:37 pm
Reputation: 0

Unread postAuthor: jackssmirkingrevenge » Fri Jan 13, 2012 2:23 am

A good track pump is not that expensive and will give you 250 psi or so with relative easy, much more power/shots and still within the range of what PVC can safely take.
  • 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: Binary Blue » Fri Jan 13, 2012 2:26 am

OK. I'll try to find one at the local store. Thanks!

All I have right now is a cheap air compressor for bicycle tires that goes a little over 100PSI and a CO2 tire inflator already in use with another project, based on this one you made:

http://www.spudfiles.com/forums/6mm-semi-added-trigger-and-mag-t10075.html

It works very well.
  • 0


Binary Blue
Specialist
Specialist
 
Posts: 40
Joined: Thu Sep 01, 2011 6:37 pm
Reputation: 0

Unread postAuthor: jackssmirkingrevenge » Fri Jan 13, 2012 2:28 am

Binary Blue wrote:It works very well.


This forum has a showcase section ;)
  • 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: Binary Blue » Fri Jan 13, 2012 2:32 am

I just have to build a case for the semi-auto before I can show it off. It's just very bare bones right now.

I'm trying to make it fit into this shape:
Image

Just some cutting left to do on my CNC mill.

Also, your post said something about high friction in that design. I found that lubricating the inside of a syringe with vaseline (I'll try silicone lube next) cuts down a lot of the friction. In fact, I was able to use the syringe's plunger instead of casting one out of epoxy.

Petroleum jelly should be safe for use in the syringe since syringes are usually made of the same plastic that petroleum jelly containers are made of and are usually designed to be chemical-safe.
  • 0


Binary Blue
Specialist
Specialist
 
Posts: 40
Joined: Thu Sep 01, 2011 6:37 pm
Reputation: 0

Unread postAuthor: jackssmirkingrevenge » Fri Jan 13, 2012 2:58 am

Binary Blue wrote:Just some cutting left to do on my CNC mill.


I underestimated your facilities - if you have that available, why not make your design fit into a block into which all the parts (barrel, chamber etc.) plug into?

Petroleum jelly should be safe for use in the syringe since syringes are usually made of the same plastic that petroleum jelly containers are made of and are usually designed to be chemical-safe.


The issue is the plunger seal, it tends to absorb lubricant and expand, creating more friction. Ah well, now that I have my own lathe and mill, my epoxy piston casting days are long behind me ;)
  • 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: Binary Blue » Sat Jan 14, 2012 2:23 am

I prefer building things using ready-made parts for now since they will likely be better than what I can machine at home right now.

Also I don't have access to anything to cut besides lots of wood and very thin particleboard right now.

But I plan on using the CNC machine to cut the hole in the PVC endcap.
  • 0


Binary Blue
Specialist
Specialist
 
Posts: 40
Joined: Thu Sep 01, 2011 6:37 pm
Reputation: 0

Return to BB/Airsoft/Pellet Gun Discussion

Who is online

Registered users: Bing [Bot], Google [Bot], MSNbot Media, Yahoo [Bot]

Reputation System ©'