Return to Index  

Some gun info....

October 28 2002 at 5:21 PM
No score for this post
  (Login DTom)

Response to Swank gun, cool designs....

Thanks for the response Latke. Your site has been very helpful as well and is very nicely done! Unfortunately, I didnít find it until I was making my 2nd gun (Spudzuka), but the 1/8Ē NPT pipe die on for the propane tube helped there. For this 1st gun, I sweated on a fitting, which I have a minor leak in. Plans to redo that.

The performance is great! Man, does that potato move! I havenít measured distance yet, but Iím getting hang times of 10-11 seconds when shot straight up. The main thing Iíve learned is to ventilate the chamber between shots. Moving my flapper/ramrod in the barrel 4-5 times with the purge valve open takes care of that.

As far as specifics on this gun I have a 2Ē sch 80 barrel with a volume of 141.7 cuin. The combustion chamber is 4Ē sch 80. 1.5:1 would have put this at a volume of 213 cuin for a length of 18.5Ē. I think I shortened up a little slightly cause I ignored the elbow in the barrel volume. (I think I ended up at 15Ē but itís out in the garage and Iím here ). So anyway, the metering chamber is 3/8Ē pipe x 9.75Ē from valve-to-valve, so I have a volume there of 1.9144 cuin. The 15Ē chamber works out to 172 cuin of volume (probably a little more if I add the elbows in). so saying I need 4% of that as propane and solving for the regulator pressure (p1 * 1.9144 = 14.7 * 6.9) gives me around 53 psi. I actually have the regulator set at 60 psi right now. I dunno if all this is right, but it shoots great.

As far as the max. pressure gauge about all Iíve seen is 25-28 psi. I do not think though this conventional gauge is quite capable of reading the instantaneous pressure spike in the chamber, so I am suspicious of itís accuracy. Iíll be writing another post on how to accurately establish a chamber pressure on a combustion gun. Iím interested on your thoughts there.

BTW, another thing I did for the spud cutter on this is I found some thinwall aluminum tube in McMaster Carr with an ID of 1.91Ē. A 6Ē length of that make a great spud cutter with the walls being so thin.

Scoring disabled. You must be logged in to score posts.Respond to this message   

  1. re:some gun info... - _latke on Oct 29, 12:41 AM
  3. i need help! - kaleb on Nov 6, 9:28 PM
Create your own forum at Network54
 Copyright © 1999-2014 Network54. All rights reserved.   Terms of Use   Privacy Statement  
Disclaimer: Myself or anyone on this forum is not responsible for anybody elses actions. YOU ARE RESPONSIBLE FOR YOU!!!