Super Bolt and Low pressure upgrades

[ciaran.mooney]

This is only an idea - it is not supported by mathematics or physics only what I know - which is GCSE grade maths and physics.

Seeing as the superbolt is a lot lighter (1/3 or so) than a normal stock bolt - it shouldn't require as much force to get up to the required speed and force. I know the currect A.I.R. and RT valves are capable of being turned down to get more efficiency but they were not designed for this.

Maybe AGD you could re-engineer a valve so that it will work as efficiently as possible with a superbolt giving more shots (which i would love) and possibly a lower pressure (though not that needed it would be nicer to have a less harsh marker, and give me the chance to use higher grade paint).

Feel free to contradict, insult - congratulate or reward.

[AGD]

The weight of the bolt and the efficiency are not connected. You still need X amount of pressure to fire the ball at 300 fps. You also dont get more shots from low pressure and from what we see with the shocker and the impulse you get less.

If there was an easy way to do it we would.

AGD

[ciaran.mooney]

Thank you - see told you i knew bugger all about it

Another idea - rather than having a superbolt with a delrin (sp?) sleeve, have one with a delrin core. Because as far as i can see most of the problems that are happening with the super bolt are as a result of it catching the spring, and the fact that it eventually wears out (though i dont think any ones had one that has worked long enough to replace the sleeve ).

Though the cross-section would look like - metal - delrin - metal - so that the bit that strikes the ball doesnt soften or have problems.

Benefit - in my head no wearing out of the delrin
- the sleeve wont catch the spring and come off.

Con - a wee bit heavier than current superbolts.

Again feel free to contradict, insult - congratulate or reward.

Ps. I have way too much time on my hands at school.

[ezrunner]

lp v/s efficiency

Ok, I am slightly biased, but I have several markers.

I have a mag of which I am proud, but it needs a
super bolt and some plastic nubbins to help w/
ball breakage.

Low Pressure operation (lp) and efficiency do not
have to coexist, but it seems that each marker design
has a happy medium.

The Automag has to over come the force of the
return spring by applying force to the center rod of the
bolt. For the pressure to move the bolt to be lower, the
effective diameter of that rod need to be larger. That
could be accomplished with a larger diameter disc inside
the valve with a push rod to move the bolt.

The Autococker has several flavors, the 99 and before,
the 2000 and above, and the AKA. These all have different
valve areas and that makes them operate differently.

The 99's seem to get as low as 350 while efficiency rises.
When you get below that, your efficiency declines. The
2000's get to about 210 w/ an lp chamber, and the
AKA's get as low as 170 that I have seen. Below
these thresholds the efficiency degrades. Above these
it degrades.

The biggest advantage to lp is that the usable amount
of pressure in a tank is higher in an lp application. I can
get 1200 - 1400 shots from my mag from a 114/3000.
I can get 2000 - 2400 from the cocker on the same bottle.

Partly because below 800psi the mag starts to run lean
and the fails to operate. This could also be related to
the bottle in use. The cocker operates down to 200
psi before it becomes un-usable.

Both are great markers and I am not here to start any flame
war. I think that LP only applies to the point you have your
marker tuned to the point of maximum efficiency, then the
argument of lp breaks down.

-rob

[orangejulius]

tom you can get 2500 shots off a impulse with 68/45 what you talken about

[CRySyS]

I'll belive that statement when I see it with my own eyes. I concede though that it may be possible with a heavily modified Imp like one with an lpr driving the bolt and with a supershort dwell and operating upward of 250+psi. Then, and with some internal work the gun may be capable of that but out of the box I've never seen an Imp get anywhere near that number.

Or is your 68/4500 full of CO2?

[orangejulius]

talk to el I believe his isnt modified that much he doesnt use a valve spring

[xatle]

Originally posted by AGD
The weight of the bolt and the efficiency are not connected. You still need X amount of pressure to fire the ball at 300 fps.

I have to disagree, the weight(mass) of the bolt must have some effect on efficiency.

It would be alot easier to explain useing a handful of useful formulae but i lack the math for it so I'm just gonna do my best without em.

The bolt has mass, the energy stored in the dump chamber is used to set that mass in motion, this energy is spent, the spring absorbs most of it then uses the absorbed energy to return the bolt to its origonal position where it strikes the valve disipating its remaining energy in the form of vibration or "kick", also a portion of the energy being applied to the bolt is absorbed by the paint ball causing the ball to move as well, probably matching the peak velocity of the bolt.
A bolt with less mass will achieve a greater velocity with the same amount of energy applied to it for the same distance, the paint being in contact with the lighter bolt will also achieve greater velocity.
An object traveling at 16 fps needs less energy added to it in order to achieve 300 fps than the same object traveling at 15 fps.

I know im splitting hairs but its always been my impression that thats what maximizing efficiency was all about, feel free to poke holes or maybe even supply the rest of the board with the relevent math involved with this.

-Dan, 2 of 5 mag owners in my circle

[athomas]

I have to agree somewhat with "xatle". The more speed the ball gets before using any air source would definately incease efficency. How much efficiency? I'm not sure yet. Someone will have to sit down with their pen and paper and figure out the speed of the ball once the bolt is fully forward and the final velocity of the ball at the end of the barrel. Do it with different bolt weights and check the results. The lighter bolt should have slightly better efficiency and therefore be able to use slightly lower chamber pressure to achieve the same final velocity at the end of the barrel.

The difference may be so miniscule that it is of no consequence, but it would be interesting to know.

On the other side of the coin, would the increased speed that the lighter bolt could achieve, have a negative affect on the harshness of the mag on the paintball? Maybe the superbolt goes too fast and strikes the paintball with too much initial force. Has anyone thought of this angle?

Just a few thoughts.

[Wat]

I believe Mr. Kaye on this.

"The weight of the bolt and the efficiency are not connected. You still need X amount of pressure to fire the ball at 300 fps."

The reason this is so because the pressure and volume that hits the ball is completely independant of the spring or mass of the bolt. Putting a softer spring or lighter bolt won't change that pressure at all.

The gas expands in the powertube pushing the bolt forward from say, 1ci to 2ci (no idea what the actual numbers are). Its new pressure doesn't matter if it pushed a big weight to expand or if it expanded effortlessly. Only thing that matters is the change in volume. And if you really wanted to test this. Fire a shot and chrono it. Take the bolt spring out. Fire another shot, see if the velocity jumps.

Actually...if anything, a lighter bolt/spring would drop velocity. Gas cools as it expands and cools faster the more rapidly it expands. Cooler gas = lower pressure = lower fps. But i think the change in rate of expansion is minimal for there to be any noticable change in cooling.

As for extra ball speed from a faster moving bolt, i think that is mostly negated by friction as soon as the ball enters the barrel. If the barrel was loose enough so that the ball could carry the extra velocity from the bolt movement, then you'd lose efficiency as more gas would escape around the ball.

[xatle]

i have no doubt whatsoever that removing the bolt spring would give you a noteable jump in velocity, an extra 30 or 40 fps wouldnt suprise me at all. not only would the bolt reach a much higher velocity but without the spring to return the bolt you get a complete dump from the chamber wich is in the neigborhood of an extra 50 psi(this isnt something that im willing to verify, if i hurt my mag it costs time and/or money to fix it, and that would suck).

how rapidly a gas expands doesnt change the total amount of cooling, only how steep the temperature spike is.

the ball should encounter the same barrel friction reguardless of what you use to push the ball.

im thinking that drilling out the center of the bolt plunger and filling it with epoxy or something along those lines might be a good plan to further reduce the weight of the bolt...hmmm... a titanium super bolt with an epoxy filled plunger...sounds pricey

[68microboy]

lp...

correct me if i'm wrong but as u lower the pressure it needs more air aka h.v.l.p. (high volume low pressure) if u dont use higher volume the gun would starve i think. so lp really does have its tradeoffs . if u think about it it will use more volume (the cubic inch part) if its using lower pressure(psi) i would also think if it need to use more air just at lower pressure then it would have a slower recharge rate because it need to put the higher volume of air into the gun... i think i probably made that as confusing as possible. tell me what u guys think

[kilaueakid]

I would definately think the tension of the spring has an effect on velocity/effiency and the pressure in which the gun CAN operate at. Now the weight of the bolt is a different story.

First of all, we all know that a mag has a dump chamber pressure of about 400psi. We also know that there is roughly 60-80psi of air launching the ball out the barrel. Now tell me where the other 320-340psi goes....most of it must be used to push the bolt forward against the spring.

These are just thoughts here and have no fact behind them. It would seem that a weaker bolt spring would take less pressure to push the bolt forward. Let's say you went with a spring about 5x weaker, you could run the gun between 120-200psi. The way I would do this would be to remove all of the internals of the valve except for the on/off assembly. Replace the back reg with a hollow air chamber to store more available air. On the retro valve, you would have to plug the little hole on the side that goes into the piston assembly, so air doesn't leak out. Some of the air passageways would maybe need to be enlarged. A good lp reg with great flow capabiltity's would also be needed. Now your velocity is controled by your input pressure. 120psi may give you 200 fps. 190psi may give you 280's.

I cool test to do is to remove the brass reg seat thingy that is held in place by the back reg. Next have an accurate way to measure input pressure. Start out around 300 psi and chrono the gun. Now put 350 or 400psi into the gun and re-chrono. See what kind of input pressure it takes to get to a desired velocity and that pressure will be the working pressure of your valve(at a specific velocity of course). If you try to rapid fire without this piece you will have major shootdown.

Sure if you go with a lighter bolt spring your bolt won't return as fast, but if it came down to getting a couple hundred extra shots per tank and less barrel breaks(assuming this would slow down bolt speed making it easier on the next ball in the stack), vs being able to shoot 18sps, I know what I would favor, do you?

This would be interesting to test out. I may have to go remove my bolt spring and the brass reg seat thing, put 120psi into the gun and see what it chrono's in at. If anyone else tries this, let us know back here.

[Bad Dave]

Where does the other 320-340 psi go?

you need to look at the pressure and volume together. now p1v1 in the chamber might have p1=400 psi

now p2 behind the ball=60psi

so v2 must have increased in volume from v1.

does that sound right?

I think the problem with the mag is high bolt speed, allowing it to cycle so fast. Need to reduce cyclic rate to 16bps tops and see how it affects chops etc.etc.

new bolt spring combos might be the way to do this.

[bjjb99]

Missing Pressure

The peak behind-ball pressure during a firing cycle is around 60 psi. The peak pressure occurs early in the firing cycle, when the ball is darn close to the bolt. To drop the chamber pressure from 400 psi to 60 psi simply on a p1*v1=p2*v2 basis would require the total volume to increase by at least a factor of six. This simply does not happen between the chamber, power tube, bolt, and space behind the ball until the ball is quite a distance down the barrel. Thus, pressure drop is not purely a pressure-volume effect.

I believe the bolt, return spring, and power tube act as a sort of regulator, limiting the flow of gas from the chamber to behind the ball. This in turn limits the peak pressure that can be generated during firing, and increases the time required to achieve this pressure as compared to a knock-open type of valve system. I believe somewhere in the following thread Tom stated that the Matrix and the Automag take slightly longer than most other markers to reach their peak behind-ball pressure.

http://www.automags.org/forums/showthread.php?threadid=18939

An interesting experiment would be to test a Mag's behind-ball pressure for different bolt return spring strengths. Stronger springs should take longer to reach peak pressure, and that peak pressure should be lower. Without having a barrel with a pressure sensor in it, one might be able to perform the test by observing the average exit velocity of paintballs fired from the Mag as one uses bolt return springs of different strengths.

BJJB