What is the VOLUME of air required to go 300 FPS?

[cledford]

Re: front?

Originally posted by QUINCYMASSGUY
"Devolumizers! Up your mag's efficiency by 20%!"

And wouldn't it also aid the recharge rate?

You know, this could be a huge marketing boon for AGD if it panned out. Tom has been beating his head against the wall for a longtime over the LP "fad." Every time he talks to a group of people he mentions that most paintball markers, within a relatively small range of psi, put about the same pressure behind the ball. Since no one has stopped to listen, and since LP sells and "HP" mags are stigmatized, he's reluctant to go the other direction. Here lies the hidden opportunity. LP, unless done excruciatingly right, is inefficient. efficiency is the next big milestone to be met. We know that we've topped out on accuracy due to inherent lack of same due to the nature of the projectile we shoot, the speed wars are about over with people even out-shooting HALOs now, so the next big area would be gas mileage. If the efficiency of the mag was to skyrocket, did not require fancy upgrades and/or constant tweaking, Tom could actually advertise AGAINST the grain! Turn the misunderstanding against everyone - people might not grasp the technical aspects of the whole thing - but if they see someone getting the same number of shots from a 45/45 as another marker on a 68 they'll still take notice.

I guess my point here is that the market doesn't seem to be responding to reason and fact, so why not throw it all out the window and go long with a different tactic? They can't ignore results...

-Calvin

[hitech]

Originally posted by cledford
Instead of producing inserts to reduce the size of the valve chamber, has anyone thought of drilling a honking large hole directly into the valve chamber (from the outside) the threading it to accept a large set screw? Then you could just "dial" in the set screw to reduce the air chamber size.

-Calvin

Yes I have, however, how would you get it to seal. Also, I'd want it to still fit inside the body. It's still probably possible, I just can't think of an easy way to do it.

[cledford]

Seal it with lock-tite 242. Each time you move it you many have to reapply the 242 - but it takes like what an hour to cure? If you use a set screw, down through the top you won't have any clearance issues. Use a short enough set-screw and it'll be subsurface even when not flush with the inside (air chamber) wall. Then you can back it out to test LP as well

-Calvin

[Cristobal]

It would seem to me that even in the best case senario a marker will use somewhat more than 111 in-lb of energy to fire a paintball. Energy Transfer to a paintball can hardly be 100% efficient as I imagine that frictional forces alone are non-negligible even assuming perfect flow paths. Anybody want to take a shot at calculating how much this might alter the minimum?

[pbjosh]

Just a quicky-

At 285fps a paintball has 100.02in*lbs of energy (okay, we can round to 100)

SO-

If a marker is shooting at 285fps, and using 200in*lbs, then it is only 50% effecient.

At that rate 1800 shots off of a 45/45 is possible- but damn near unlikely.

Josh

[nicad]

Josh-
I understand the in*lb of energy concept.. but how are you arriving in those units for the minimum energy of a paintball? and what variable asumptions are you making?

thanks-
Colin

[pbjosh]

I grabbed it from Nipponout:

Assume:
3gram paintball
300fps velocity

Units:
3gram = .003kg
300ft = 91.44m
1 joule = 8.8507457 inch pound

Paintball kinetic energy:
= .5 * (.003kg) * (91.44m/s)^2
= 12.542J
= 111.005in-lb

And simply changed 300ft = 91.44m to 285ft = 86.8m

Resulting in 11.3j and hence, 100ft*lbs

Josh

[nippinout]

Originally posted by nicad
Josh-
I understand the in*lb of energy concept.. but how are you arriving in those units for the minimum energy of a paintball? and what variable asumptions are you making?

thanks-
Colin

We're assuming lots of things.

Linear constant acceleration.

Zero barrel/ball friction.

100% conversion of potential energy into the kinetic energy of a paintball.

3gram paintball.

I don't think I showed the change of units.

kg*(m^2/s^2)
=[kg*(m/s^2)]*m
=N*m
=J

[SlartyBartFast]

Originally posted by nippinout
We're assuming lots of things.

Now that's saying a lot.

One of the huge assumptions that never gets covered is the residual air in the tank.

At some point there isn't enough pressure to fire a ball at 300fps (or at all). That energy has to be removed from the available energy in a tank.

[QUINCYMASSGUY]

slarty

Every shot the LP gun gets off after the psi point that the HP gun would stop shooting at is extra credit, so even if it uses more air per shot, you may end up better off. For example:

A high pressure gun shoots 500 shots from 1000psi to 600psi then dies out.

A low pressure gun shoots 400 shots from 1000psi to 600psi but can keep firing.

Right there, the LP may look less efficient if all you're going on is the volume per shot each used. BUT....

The low pressure gun shoots 300 shots more from 600psi to 300psi

So the LP got 700 shots from a tank fill, the HP got 500. I'd say the LP was more efficient.

Now, these numbers are completely bogus, and LP may still be inefficient, but I'd be curious to see how it all stacks up for real. And I am rephrasing what Slarty said, he hit the nail right on the head. I'd be curious to see if Tom Kaye and anyone else making HP benefits points took this into consideration.

[SlartyBartFast]

Originally posted by QUINCYMASSGUY
Every shot the LP gun gets off after the psi point that the HP gun would stop shooting at is extra credit, so even if it uses more air per shot, you may end up better off.

I may agree with you. But that's a lot of unanswered IFs.

How useful are the remaining shots from a gun that can function at lower pressure? How consistent are the shots? Is there fps drop-off?

[QUINCYMASSGUY]

if

Tons of if's..... my Merlin's guts and pneumatics are in my room, the body parts in Easthampton HOPEFULLY (key word) being annoed so they should soon be all set. I will probably try different setups but the biggest issue is getting a consistent fill to test this out with. Even gauges can be inaccurate.

One real important measurement is the point where recharge and consistency become unbearable, but alot of that is opinion. I'd rather have a gun that fires 1000 shots at full consistency then stops entirely than one that kicks out 800 full consistency shots then 400-500 shots at low FPS with slow recharge.

[pbjosh]

You guys are re-working things already done-

There is a link at the start of this to post from years ago when I went through most of this with the AO crowd.

And I think the tink has some old links-(thanks to painthappy at vintagerex.com for the serch engine) hold on:

http://www.network54.com/Hide/Forum/message?forumid=9013&messageid=976000283

http://www.network54.com/Hide/Forum/message?forumid=9013&messageid=976002688

http://www.network54.com/Hide/Forum/message?forumid=9013&messageid=980118172

And of course here is a re-cap of the AO links *in this post*:

http://www.automags.org/forums/showthread.php?s=&threadid=18939&highlight=pressure+barrel+length+needed

Anything else?

yes, you in the back with your hand up-

Josh

[athomas]

Re: slarty

Originally posted by QUINCYMASSGUY
Every shot the LP gun gets off after the psi point that the HP gun would stop shooting at is extra credit, so even if it uses more air per shot, you may end up better off.

Yes you may, but:

Is the extra air enough to overcome any inefficiencies from shots fired from all the available air?

ie;
(1) A 3000 psi tank on a gun that can only use down to (a)800spi vs a gun that can use down to (b)300psi. Gun (a) has 2200 usable psi gun (b) has 2700 usable psi. Gun (b) has 22.7% more usable air than gun (a). As long as gun (b) doesn't waste more than 22.7% more air each shot than gun (a), then gun (b) should be able to fire more shots from the 3000psi tank.

(2) Using a 4500psi tank changes the numbers. Gun (a) has 3700 usable psi. Gun (b) has 4200psi. Now gun (b) has only 11.11% more usable air. The amount of inefficiency that gun (b) can tolerate and still get more shots off is only 11.11%.

It still comes down to air delivery though. Any gun can be efficient if you can deliver the air to the ball with no delay. Make the barrel the only ineffieciency. That's a common tool on all guns. If you find a good one, it will probably work well on all gus.

[hotrod]

I'm curious about an efficiency loss that has barely been mentioned. It seems like every shot wastes air coming back past the bolt and out the feed tube. Hence the need for the powerfeed version. If the bolt could seal behind the ball then you could have perfect efficiency of the expanding air. I don't understand the focus on the air chamber if the launching step contains uncontrolled losses. Am I misunderstanding the design?

Just thinking.