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 61 users online :: 4 registered, 0 hidden and 57 guests


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

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

The Team
Administrators
Global Moderators
global_moderators.png CS

Super Simple Mini Piston Hybrid?

Post questions and info about hybrid (compressed gas with fuel) powered cannons here. This includes discussion about fuels, ratios, ignition systems, build types, safety, and anything else relevant.
Sponsored 
  • Author
    Message

Unread postAuthor: Lockednloaded » Fri Dec 17, 2010 8:31 pm

go for it, you'll be finished far before I will. My first one failed horribly; the syringe tube was launched out of the back, so I put in an order for some more syringes. No pictures, had to clean it up before my parents could see that one of my creations failed
  • 0

I love lamp
User avatar
Lockednloaded
Major General
Major General
 
Posts: 1558
Joined: Thu Sep 03, 2009 9:38 pm
Location: Texas, USA
Reputation: 0

Unread postAuthor: jackssmirkingrevenge » Sat Dec 18, 2010 2:04 pm

Lockednloaded wrote:the syringe tube was launched out of the back


during pressurisation or combustion?

This is what I had in mind, something the size of a pocket pistol which could have a barrel extension/suppressor added on.
  • 0

Attachments
minihybridpiston.GIF
minihybridpiston.GIF (11.71 KiB) Viewed 717 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: Lockednloaded » Sat Dec 18, 2010 2:33 pm

combustion. in that design, is your piston supposed to be airtight?
  • 0

I love lamp
User avatar
Lockednloaded
Major General
Major General
 
Posts: 1558
Joined: Thu Sep 03, 2009 9:38 pm
Location: Texas, USA
Reputation: 0

Unread postAuthor: jackssmirkingrevenge » Sun Dec 19, 2010 4:19 am

Lockednloaded wrote:combustion.


Ouch. Any idea what went wrong, epoxy not sufficiently cured/thick, surfaces not cleaned/abraded properly?

in that design, is your piston supposed to be airtight?


No, I'm not sure it would work but it will certainly simplify construction. In practical terms it will probably look something like this, still looking at chamber materials.
  • 0

Attachments
minihybridpiston2.GIF
minihybridpiston2.GIF (26.23 KiB) Viewed 687 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: Lockednloaded » Sun Dec 19, 2010 3:44 pm

sorry, but I found an easier way to go about this without epoxy. I'm using a pre-made 1/2" relief valve. Its basically a pop-off valve set at 75psi with an outlet port, so I'll probably go with 5X max unless I can find a stronger spring
  • 0

I love lamp
User avatar
Lockednloaded
Major General
Major General
 
Posts: 1558
Joined: Thu Sep 03, 2009 9:38 pm
Location: Texas, USA
Reputation: 0

Unread postAuthor: ramses » Sun Dec 19, 2010 4:54 pm

That valve may close with a projectile in the barrel, as that would reduce the effective pressure differential. Look for a spec of closing pressure, that is the minimum pressure drop across the valve for it to stay open.

Unless the back of the popoff is ported to atmosphere, which it is likely not.
  • 0

POLAND_SPUD wrote:even if there was no link I'd know it's a bot because of female name :D
User avatar
ramses
Major General
Major General
 
Posts: 1679
Joined: Thu May 29, 2008 6:50 pm
Reputation: 3

Unread postAuthor: al-xg » Sun Dec 19, 2010 5:12 pm

Would an unbalanced piston be a good way to vent the pilot volume once the shot goes off ? Or is that making it too complex ?
  • 0

User avatar
al-xg
Colonel
Colonel
 
Posts: 643
Joined: Fri Jan 19, 2007 12:29 pm
Reputation: 0

Sponsored

Sponsor
 


Unread postAuthor: ramses » Sun Dec 19, 2010 5:39 pm

he's using a pre-made relief valve. There is no pilot. I'm not sure what you mean by an unbalanced piston. Both of the recent 1.5" porting hybrids vent the pilot with the main piston as it begins to move.

And I retract my previous comment; the back of the relief valve may well be ported to atmosphere. In that case, the valve will close at a whatever pressure above atmospheric.
  • 0

POLAND_SPUD wrote:even if there was no link I'd know it's a bot because of female name :D
User avatar
ramses
Major General
Major General
 
Posts: 1679
Joined: Thu May 29, 2008 6:50 pm
Reputation: 3

Unread postAuthor: al-xg » Sun Dec 19, 2010 5:52 pm

I think that is what I'm referring to. The piston has a rod through it and a second sealing face larger than the barrel diameter but smaller than the chamber diameter. The second sealing face blocks off the pilot port. Combustion pressure moves the main piston back and the smaller sealing face comes off the pilot seat releasing the pilot volume. A sort of hybrid QEV. ?
  • 0

User avatar
al-xg
Colonel
Colonel
 
Posts: 643
Joined: Fri Jan 19, 2007 12:29 pm
Reputation: 0

Unread postAuthor: jackssmirkingrevenge » Sun Dec 19, 2010 5:56 pm

You could add a spring to a QEV pilot:

Image
  • 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: ramses » Sun Dec 19, 2010 7:39 pm

I think he's using the popoff as the main valve.
  • 0

POLAND_SPUD wrote:even if there was no link I'd know it's a bot because of female name :D
User avatar
ramses
Major General
Major General
 
Posts: 1679
Joined: Thu May 29, 2008 6:50 pm
Reputation: 3

Unread postAuthor: jackssmirkingrevenge » Mon Dec 20, 2010 2:25 am

ramses wrote:I think he's using the popoff as the main valve.


I had modded a pop-off as a main valve here, the problem is that the piston isn't airtight so it would tend to vent out past the piston as well as the port.
  • 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: al-xg » Mon Dec 20, 2010 4:54 am

Here is what I meant, I'm pretty sure I've seen this set up before.

Oh and not too sure why I edited the QEV schematic, I should have just used the proposed design.

I guess I would be less silent... But at least it is closer to a burst disk in that once it has opened it doesn't require any energy to stay open.
  • 0

Attachments
QEHybrid.jpg
QEHybrid.jpg (17.83 KiB) Viewed 545 times
Last edited by al-xg on Mon Dec 20, 2010 6:53 am, edited 1 time in total.
User avatar
al-xg
Colonel
Colonel
 
Posts: 643
Joined: Fri Jan 19, 2007 12:29 pm
Reputation: 0

Unread postAuthor: Lockednloaded » Mon Dec 20, 2010 5:35 am

i get that those ways would be more efficient, and offer full flow the full time, but it doesn't bother me to sacrifice performance for simplicity in this project. I know the valve will close back before all the gasses are exhausted, but I doubt that extra ~75psi getting trapped will do anything.
  • 0

I love lamp
User avatar
Lockednloaded
Major General
Major General
 
Posts: 1558
Joined: Thu Sep 03, 2009 9:38 pm
Location: Texas, USA
Reputation: 0

Unread postAuthor: POLAND_SPUD » Mon Dec 20, 2010 5:46 am

@al-xg
interesting... but have you noticed that the forces acting on the piston even out?
  • 0

Children are the future

unless we stop them now
User avatar
POLAND_SPUD
Chief of Staff
Chief of Staff
 
Posts: 5405
Joined: Sat Oct 13, 2007 4:43 pm
Country: Israel (il)
Reputation: 10

PreviousNext

Return to Hybrid Cannon Discussion

Who is online

Registered users: Bing [Bot], Google [Bot], Google Adsense [Bot], Yahoo [Bot]

Reputation System ©'