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 45 users online :: 5 registered, 0 hidden and 40 guests


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

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

The Team
Administrators
Global Moderators
global_moderators.png CS

fuel mixing

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

fuel mixing

Unread postAuthor: ramses » Sun May 17, 2009 9:47 pm

First, the relevant specs of my cannon:
    2x12" chamber plus a lot of fittings
    manometric metering
    ignition: camera flash+ignition coil (tested to work at pressure)

(see picture for configuration of spark and fuel)

Anyway, the cannon won't fire reliably, but does fire occasionally. It does fire reliably if, after I fill the chamber up with air, I pull off the hose and vent some of the air/propane to atmosphere. I guess this mixes the gasses. My question is whether or not I can do something simple and cheap to mix the gasses better without venting any. I read in another thread about adding a venturi, but no one else has needed anything like this to make theirs work.

thanks
  • 0

Attachments
back of chamber.JPG
meh.
back of chamber.JPG (16.61 KiB) Viewed 1029 times
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

Re: fuel mixing

Unread postAuthor: Technician1002 » Sun May 17, 2009 10:21 pm

ramses wrote: I guess this mixes the gasses. My question is whether or not I can do something simple and cheap to mix the gasses better without venting any. I read in another thread about adding a venturi, but no one else has needed anything like this to make theirs work.

thanks


I have seen items left loose in the cannon to mix gasses much like a spray paint can has a marble inside. I have seen a length of PVC plastic chain, superball, or other related shake to mix items. Be sure the mixing agitator won't knock your spark gap out of whack.

Try not to use something that displaces a lot of space as this will mess up your mix. I have toyed with using a practice wiffle ball. It is the hollow ball with lots of holes. One of those shaken back and forth a few times should do a fine job mixing the contents.
  • 0

User avatar
Technician1002
Chief of Staff
Chief of Staff
 
Posts: 5190
Joined: Sat Apr 04, 2009 11:10 am
Reputation: 14

Unread postAuthor: ramses » Mon May 18, 2009 12:27 pm

Thanks, I may do that, but the future 3" steel barrel will make the shaking part rather difficult. It won't screw up my mix because I use manometric metering.

I have control over how fast my chamber is filled with air (while I am at my compressor) should I dump the air in as fast as possible, or just crack the valve and let it in slowly?

Does anyone think that making a nozzle to accelerate flow would be worth while?
  • 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: Lentamentalisk » Mon May 18, 2009 12:54 pm

Ok, two things here. Make sure you put the fuel in fist, otherwise it ends up all concentrated on one side. 2nd, the faster the air is flowing when it enters the chamber, the more venturi effect it will have, so the better it will mix. there are two ways of doing that, either dumping in the air as fast as possible, on the compressor side, or sticking a tiny nozzle on the end, to make it go really fast.

Good luck.
  • 0

Do not look back, and grieve over the past, for it is gone;
Do not be troubled about the future, for it has not yet come;
Live life in the present, and make it so beautiful that it will be worth remembering.
User avatar
Lentamentalisk
Brigadier General
Brigadier General
 
Posts: 1202
Joined: Tue Aug 07, 2007 5:27 pm
Location: Berkeley C.A.
Reputation: 0

Unread postAuthor: jimmy101 » Mon May 18, 2009 2:18 pm

Tech's suggestion are pretty good. A practice golf wiffle ball might work pretty well and is small enough. People have also used a length of chain.

Back to Ramses original question...
The easiest way to trouble shoot your problem is to simply let the gun sit a couple minutes after fueling and before firing. If the problem is that the fuel isn't well mixed then letting the gun sit for a couple of minutes (perhaps with occasional inversion) will let the gases mix fully. If the gun fires consistently after setting, then the problem is mixing. If it doesn't, then the problem is either the mixture or the ignition.
  • 0

Image

jimmy101
Lieutenant General
Lieutenant General
 
Posts: 3129
Joined: Wed Mar 28, 2007 9:48 am
Location: Greenwood, Indiana
Country: United States (us)
Reputation: 7

Unread postAuthor: ramses » Mon May 18, 2009 2:35 pm

I will attempt the nozzle, as I intend to use a bike pump for firing in the woods. I am putting the fuel in first, and like I said before, the gun will have a big heavy barrel on it, so shaking it around won't be practical. I wouldn't be able to put anything large in the chamber anyway, because I don't have a big enough vice at home.

Thanks for your help, everyone!
  • 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: daccel » Mon May 18, 2009 11:00 pm

Jimmy's suggestions for a troubleshooting process make sense, my first thought was that perhaps your mix is off and when you vented it was bringing the % back into line.
  • 0

User avatar
daccel
Donating Member
Donating Member
 
Posts: 238
Joined: Thu Oct 11, 2007 9:51 pm
Location: BC, Canada
Reputation: 0

Sponsored

Sponsor
 


Unread postAuthor: Technician1002 » Mon May 18, 2009 11:11 pm

ramses wrote:I am putting the fuel in first,
Thanks for your help, everyone!


With the 1/2 inch T, there is an excellent possibility the plug area is mostly air and too lean to fire. After filling with air, venting a tiny bit to expell the air and draw mixture to the plug may be helpful.
  • 0

User avatar
Technician1002
Chief of Staff
Chief of Staff
 
Posts: 5190
Joined: Sat Apr 04, 2009 11:10 am
Reputation: 14

Unread postAuthor: ramses » Fri Jul 17, 2009 10:00 am

I added a venturi type thing and still have problems! here are some pictures. Even after waiting 3 min, it won't fire. would the configuration shown in the first picture be a better configuration than the one in my first post?

Thanks
  • 0

Attachments
3024 cropped.JPG
the drilled out 1/4" plug
3026 cropped.JPG
the ~.054 hole
3027 cropped.JPG
the whole air assembly
revised ignition tee.JPG
revised configuration
revised ignition tee.JPG (20.41 KiB) Viewed 897 times
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: GalFisk » Tue Jul 28, 2009 4:25 am

Your spark plug is a bit "out of the way", so you may have a problem getting a good mixture at the spark (possibly in addition to general mixture issues). I have had similar problems with my hybrid. You could try placing the spark in the middle of the chamber to see if you get more reliable ignition.
  • 0


GalFisk
Staff Sergeant
Staff Sergeant
 
Posts: 103
Joined: Mon Feb 28, 2005 4:06 am
Reputation: 0

Unread postAuthor: Willdebeers » Tue Jul 28, 2009 5:57 am

You could always add a fan (brushless preferably) to aid mixing.
  • 0

Image
User avatar
Willdebeers
2nd Lieutenant
2nd Lieutenant
 
Posts: 214
Joined: Tue Feb 03, 2009 1:18 pm
Reputation: 0

Return to Hybrid Cannon Discussion

Who is online

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

Reputation System ©'