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 37 users online :: 3 registered, 0 hidden and 34 guests


Most users ever online was 218 on Wed Dec 07, 2016 6:58 pm

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

The Team
Administrators
Global Moderators
global_moderators.png CS

QDV design - airflow vent shape

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

QDV design - airflow vent shape

Unread postAuthor: fluffyisepic » Sun Dec 09, 2018 10:07 pm

I'm looking to put together a T-shirt cannon for a school project this January, and have been reading around on QDV design. "Officially" the project is for T-shirts, but I have access to nitrogen and helium and anticipate firing other projectiles. However, my question is in regard to the "vents" cut into the inside. To prolong the life of the piston, and to provide less maintenance, what would be the ideal shape to cut the vent slits? Dan Thame's Big Red uses slits that run perpendicular to Technican1002's... Will it make any real difference?

I attached the CAD file of Big Red that I'm referring to. (Dan's) This comes from his old site, on the design/construction page.
http://web.archive.org/web/200304051122 ... udguns.htm
  • 0


fluffyisepic
Private
Private
 
Posts: 2
Joined: Mon Dec 19, 2016 1:51 pm
Location: Midwest
Country: United States (us)
Reputation: 0

Re: QDV design - airflow vent shape

Unread postAuthor: jackssmirkingrevenge » Tue Dec 11, 2018 5:53 am

Welcome to the forum!

Dan Thame's Big Red


Oh man that takes me back! Here's the drawing for quick reference:

Image

To be honest, I don't think the orientation of the slits really makes a difference. The important thing is that they are correctly beveled to avoid cutting the o-rings as they move past.

Depending on your construction method, you can avoid this altogether by simply having separate tubes. Have a look at this example:

Image
  • 0

hectmarr wrote:You have to make many weapons, because this field is long and short life
User avatar
jackssmirkingrevenge
Donating Member
Donating Member
 
Posts: 25153
Joined: Thu Mar 15, 2007 11:28 pm
Country: Holy See (Vatican City State) (va)
Reputation: 148

Re: QDV design - airflow vent shape

Unread postAuthor: fluffyisepic » Wed Dec 12, 2018 7:10 pm

Thanks! I think I'll stick with the coaxial design; at 2" the other example may prove to be more of a headache than I want to deal with. However, I do have one question for you... How is Big Red actuated? I still can't figure that one out...
  • 0


fluffyisepic
Private
Private
 
Posts: 2
Joined: Mon Dec 19, 2016 1:51 pm
Location: Midwest
Country: United States (us)
Reputation: 0

Re: QDV design - airflow vent shape

Unread postAuthor: jackssmirkingrevenge » Thu Dec 13, 2018 6:36 am

fluffyisepic wrote:Thanks! I think I'll stick with the coaxial design; at 2" the other example may prove to be more of a headache than I want to deal with.


It can still work as a coaxial:

Image

Instead of having a single tube with ports cut in it, you can have two tubes with a space between them. This gives you maximum airflow and less edges for the o-rings to wear against.

fluffyisepic wrote:However, I do have one question for you... How is Big Red actuated? I still can't figure that one out...


It's driven by an external air source, you can see the piston here.

This diagram explains it more clearly, air enters the central blue tube from an external source and this pulls the red piston back:

Image
  • 0

hectmarr wrote:You have to make many weapons, because this field is long and short life
User avatar
jackssmirkingrevenge
Donating Member
Donating Member
 
Posts: 25153
Joined: Thu Mar 15, 2007 11:28 pm
Country: Holy See (Vatican City State) (va)
Reputation: 148

Return to Pneumatic Cannon Discussion

Who is online

Registered users: Bing [Bot], Exabot [Bot], Google [Bot]

Reputation System ©'