RE: psi vs. fps [TANKS]

["Kevin" <ka1201-at-houston.rr.com>]

There is no general correlation and the math you'd go through for each
individual marker would make the task a waist of time.  Modern electric guns
specified as low pressure guns can run on very low pressures around the
100psi mark and even less.  Micro and Macro line should really only be used
in an LP setup and if some of the battlers are using those lines with CO2
that's probably why they are having problems.  The average blowback
paintball marker runs on around 800psi operating pressure.  You can do a lot
of tweaks like drilling out the valve or milling to lower the weight of the
bolt and or hammer and these things allow you to use lighter springs and
have more airflow.  Think of it like this, you can slam the ball in the
breach with a very short blast of 800psi to get it out the barrel or you can
push it gently with 100psi with the valve held open for a very long time to
get it to the same 250 feet per second you guys are using for your tanks.
Either way unless you're a master machinist engineer and air smith (of which
no on around here has claimed to be that I know of) then no homebrew one off
marker can be really judged as safe (thinking from an insurance standpoint
of the term "safe").  I'm not trying to rain on anyone's parade or anything,
I'm just giving you the facts.

-----Original Message-----
From: tanks-admin-at-rctankcombat.com [mailto:tanks-admin-at-rctankcombat.com] On
Behalf Of Douglas Shannon
Sent: Friday, June 23, 2006 8:36 AM
To: tanks-at-rctankcombat.com
Subject: RE: psi vs. fps [TANKS]

As far as I know, there is no direct corrolation between pressure and 
velocity because there are a billion other factors involved in the equation.

You have every thing from diameter of the passage, diameter of the barrel, 
paint match to the barrel (tightness of fit), length of time the valve is 
open, etc...

I have a single-action paintball marker called a Nel-Spot 007 (the original 
paintball gun!), the valve is directly in line with the barrel, a delivery 
tube from the valve puts gas directly behind the ball in the barrel. 
Velocity is affected by, the size of the openings on the delivery tube 
inside the valve chamber, the diameter of the delivery tube, how tight the 
balls are in the baller, and how long the valve is open; the time the valve 
is open is affected by the tension of the drive/main spring and the 
return/valve spring.

Every turn the air/gas makes add friction/drag and reduces it's velocity and

that affects how fast it can flow to the valve and therefore through it.




You MIGHT be able to apply some hydraulics and physics equations to get in 
the ball park, but I doubt you'd be able to nail it down to better than +/- 
30 fps.



Doug S.


>From: Christopher Clark <cjkkclark-at-comcast.net>
>
>Is there an easy way to calculate how much velocity one would get by   
>knowing the psi?  I imagine the size of the chamber where the air is  being

>stored before sent down the barrel influences the psi.  In the  case of 
>those solenoids Gary recommended for the rocket system  
>(http://www.surpluscenter.com/item.asp?UID=2006062119193174&item=20-1138&ca
tname=air) 
>will I still get 200-300 fps with the 150 psi  rating?  (Right now I am 
>thinking the air can be stored in the  accumulator at a high psi and so 
>long as all the solenoids open  simultaneously the air will be equally 
>distributed and I don't have to  worry about bursting a solenoid?)
>Thanks,
>Chris C.
>