mag technical questions- amount of time air flows out of the bolt? and..

[the electrician]

maybe one of you AGD certified techs no the answer to these questions.

when the bolt moves forward to a certain point, the air in the dump chamber can flow out the bolt. after a certain amount of air as expelled, the spring pushes the bolt back.
so, what is the amount of time that the air flows out of the bolt?

the other question. how far does the bolt piston effectively open? in other words, after it comes out of the power tube, how far does it keep going?


these questios are both pertaining to the standard bolt, not the lvl10.

[RRfireblade]

http://www.automags.org/forums/attachment.php?attachmentid=14644&stc=1

That should help you out.....some.

[the electrician]

help me understand these test results a bit if you would.

from what I can tell, the bolt is actually letting air flow for about 3 to 3.5 msec? but it's actually only useful for 2.5 msec?

what about this information:
bolt .110 open-40
.060 open-60
barely open-77

is that a percentage of completion for how much the bolt is open or something?

any help understanding this would be greatly appreciated.

[RRfireblade]

According to the legend, it's 10ms per 100 counts so......

I'm seeing the bolt fully open from somewhere around 3225 to 3250 = 25 counts = 2.5ms

3220 - 3260 (the full travel) = 40 counts = 4ms

The odd thing is breach pressure seems to start prior to bolt movement so there may be a little error in the test set up there.

3230 - 3260 = 30 counts = 3ms = the time the bolt is still open after the ball has started down the barrel.

It also seens that the bolt takes noticably longer to return than to extend,wonder how LX effects that.

Not sure about those 3 other figures. Not 100% sure about what I've just said. ;)

Good luck. :D

[Z-man]

I can offer some "eye ball" testing I have done. I know that I have got the valve cycling up to 34x a second. That would mean (would it not) that if the air is expelled in the 1st 1/2 of the bolt cycle it would be about 1/68th of a second (and probably less). Again that is not based off that graph, but my field tests.

[the electrician]

well that is a helpful piece of info rrfireblade.

but it still leaves me wondering how far the piston comes out of the power tube. I know that the amount of time it is out of the power tube and the distance it travels out of the power tube are directly proportional, just like any other valve.

the graph shows the peak pressure behind the ball. it shows that air is coming out of the bolt, before it peaks, and as it descends, there is a small plateau. I'm curious as to what that is.

I'm guess I'm kind of beating around the bush here.
what I'm really interested in is the flow rate. how much air is flowing out of the bolt that is used to fire the paintball. not too concerned about the waste before hand. I know it has been stated that there is a residual pressure of 50 psi in the dump chamber after firing.

I want to calculate the air used during the shot by taking an operating pressure reading(gonna make something to do that) then subtract the stated residual pressure.

then use a flow rate calculation (given size orfice at a given pressure for a given amount of time type of thing) and see what the difference is. the difference should be waste, plus or minus a fudge factor of course.

it still confuses me why the mag needs as much operating pressure as it does to do the deed. with .55 cu. in. of chamber, it shouldn't take more than say, 250-300 psi to do the job with that kind of volume.

the new shockers have a dump chamber volume of .58 cu. in., and operate at 200 psi. they are only using 8.5 cu in of air to propel the ball. that is pretty good (that is with the evolve bolt kit though, not stock) the place where it suffers is the pressure going into the solenoid is the same going into the dump chamber. so the shocker use another 3.5 cu. in. of air to cycle the bolt.

all this research got me to thinking why the mag uses so much air and where it is losing efficiency.
the three variables in valve flow I think are : open time, open distance, and size of orfice.
the first to are related, and it is not really helpful to extend the open time and distance. I think it's orfice size. (I know shape plays a role, but I"m only really concerned in circular opeings) I think the 1/4 piston has limitations to it's flow capabilities.

[Carbon]

it still confuses me why the mag needs as much operating pressure as it does to do the deed. with .55 cu. in. of chamber, it shouldn't take more than say, 250-300 psi to do the job with that kind of volume. I belive it is to overcome the force of the return spring?

[Snertz]

I belive it is to overcome the force of the return spring?

That's exactly why, since you have the force from a heavily tensioned spring and moment of inertia from decently weighted bolt to overcome.

[the electrician]

No.


put a weaker spring in your mag. don't change the reg at all. load it and go shoot over the chrono. guess what, it still needs the same pressure. that spring was designed specifically for the automag to return the bolt properly. I can see it being that simple with another gun, but not the automag. every single part of the automag serves two purposes. that doesn't happen by coincidence. it's specifically engineered.

besides, like I said more open time will not help no matter how it is acheived. the ball is gone in a few msec. any air expeled after that is wasted. a weaker spring let's the bolt move faster, open farther and stay open longer this wastes air. a weaker spring actually makes it less efficient.

[the electrician]

my interest is this:

did the engineers who designed the gun try a larger bolt piston diameter? surely they ran some numbers or something. there has to be a reason they used the size they did.

I've been wondering if a higher flow rate could be acheived by a larger bolt piston, being more efficient and the pressure could be reduced.you could only go so big. with the existing power tube, probably no larger than a 5/16"(.312) bolt piston. a 3/8"(.375) would be better (like that of a matrix), but not possible with the existing power tube.

I've just notice that guns that really use the air efficiently, release the air in the same amount of time, but using an orfice with a larger flow rate. using less air.

now of course lower pressure air would have a lower velocity. I need to run some numbers to see for myself the feasibility of a large bolt piston. I would want the bolt speed to be about the same, so the pressure would have to be able to be lowered in proportion to the increase bolt piston surface area(force). the hardest part will be the orfice flow coefficient. I'll have to "reverse engineer" something.

[RRfireblade]

Personally I don't think the piston O.D. is the problem,it's quite large compared to the air passages in most other guns. I think......'think' , the issue may have to do with the orrafice that's left when the piston/bolt is at the point where the majority of the air begins to dump from the chamber.It's not possible for the piston to be completely out of the power tube for obvious reasons,so..... as soon as it get's near the mouth of the PT tip,the internal pressure will flow ASAP and almost as quickly,the bolt will lose it's fight with the spring and start back home.That apparenty small gap/space/whatever that exists for a ms or so is possibly the 'restriction' in the flow the may be having a negative effect on efficiency.The biggest problem, IMO, with the cork in the bottle design is that the 'dumping' of the chamber is not as instantanious as a typical sheridan style and the flow must pass through an orafice that 'leaks' initially and never reaches a linear sized apature until after the majority of the pressure has already done it's job,by then it's too late.

Not to mention that the bolt is still flowing air well after the ball has left and 'dumps' almost all excess air/presure (within ~50psi or so) that could be left as part of the next 'charge'. That's one of the primary reasons Matrices and SFT Shockers were so bad on air and how the new bolts for them increased thier efficiency.

Or not............

;)

[Snertz]

my interest is this:

did the engineers who designed the gun try a larger bolt piston diameter? surely they ran some numbers or something. there has to be a reason they used the size they did.

I've been wondering if a higher flow rate could be acheived by a larger bolt piston, being more efficient and the pressure could be reduced.you could only go so big. with the existing power tube, probably no larger than a 5/16"(.312) bolt piston. a 3/8"(.375) would be better (like that of a matrix), but not possible with the existing power tube.

I've just notice that guns that really use the air efficiently, release the air in the same amount of time, but using an orfice with a larger flow rate. using less air.

now of course lower pressure air would have a lower velocity. I need to run some numbers to see for myself the feasibility of a large bolt piston. I would want the bolt speed to be about the same, so the pressure would have to be able to be lowered in proportion to the increase bolt piston surface area(force). the hardest part will be the orfice flow coefficient. I'll have to "reverse engineer" something.

Ouch, given a smack down before, time to try again.. :p

I think you're right in that increasing orfice size should increase efficiency. But the question is pertaining to other markers. I wonder how the graph would look like for other guns, and what the curve of the pressure behind the ball looks like. perhaps their release is much more abrupt, instead of the somewhat gradual release that a lvl 7 powertube tip results in.

Maybe machining a tip that is not sloped, but rather a square edge would show some change in the way air is handled, and more is released when the ball is still in the barrel, and used to propel the ball instead of going to waste. At that point, we could drop the pressure to compensate for the higher fps. So with a same release time, and a lower pressure (which is less air for the same amount of space) we would get better efficiency numbers?

Also is where the square edge is in relation to the end of the powertube tip may be important, since a too early release results in a ball tha isnt fully chambered, and a bolt that isn't sealed totally in the breech.

I'm probably totally off on this..

Edit: Just reread, and this is basically pertains to the issue that RRfireblade mentioned :p

[the electrician]

thanks for the reply rrfireblade.

as far as orfice size, it's only a 1/4" . that's about the same as a cocker body, but smaller than other, such as matrix, new shockers, and other low pressure guns.

I see what you're saying about the early release, but not about the bolt piston. it is not flush with the back of the bolt, it is inset about .210" on a standard bolt. I think it is possible for it to come out of the power tube to let the air by. the inner bolt surface rides on the outside of the power tube and the bolt is guided fairly well, when combined with the body keeping the bolt centered. but my thought has always been that as soon as it comes out (if it does) it loses so much pressure, that the spring keeps it from being open very far at all, and for very long. that's what made me think about increasing the diameter of the bolt piston to increase the release of air at that point. but I can see that it would probably increase the amount that was prematurely released also.

I definitely agree with you about the lack of instantaneous air release. poppet valves work much better for this.

so I guess it's back to how to keep the bolt from leaking during the bolts forward and aft movement.


I have seriously thought about making my own spool valve design to fit in an automag. something more efficient than the mag,shocker, or matrix.

[RRfireblade]

I see what you're saying about the early release, but not about the bolt piston. it is not flush with the back of the bolt, it is inset about .210" on a standard bolt. I think it is possible for it to come out of the power tube to let the air by. the inner bolt surface rides on the outside of the power tube and the bolt is guided fairly well, when combined with the body keeping the bolt centered. but my thought has always been that as soon as it comes out (if it does) it loses so much pressure, that the spring keeps it from being open very far at all, and for very long..

Yes, that's pretty much what I have in mind as well,I think we're both on the same page. I'm just thinking that it never fully clears the opening of the PT. Keep in mind I haven't measured a thing, just thinking off the top of my head here.

The idea I had some time ago was to use a pump mag type set up but using a ram to control the bolt movement and no bolt spring at all. A minor redesign of the bolt piston and power tube tip for instantanious (pretty much) pressure release in .75" or less of s stroke and the whole shibang being 'timed' exteranlly thru the ram and associated hardware/electronics.

Just a thought.......

* oh yeah.....1/4" is a huge opening,far more than what you see get passed the average poppet valve,cup seal style gun. (cocker etc) ;) even with a relieved cup seal shaft. *

[Dryden]

I understand what you've posted RR, but what you're describing is an accurate description only in terms of the currently produced bolt/piston assembly. Following E's reasoning, in the very least, if the piston were a larger outer diameter, wouldn't a larger volume of air be able to escape in the same amount of time since the gap between the bolt piston and oring/power tube tip is larger, in turn reducing the amount of wasted bleed between the point where the bolt fully opens and closes again? In other words, as the outer diameter grows, couldn't more air be instantaneously released, rather than gradually bled off and wasted?

I'm wondering if the current design isn't so much a matter of engineering, but rather a result of the limitation in materials that were available in the late 80s, the safety features built into every stage of the valve assembly, and the fact that it is rated to 3000 PSI.

[the electrician]

I've thought about that too, Dryden.

the fact that it is rated for 3000 psi is actually kind of impressive. I don't know of any other guns that are. I've given it 2000 psi before, and it didn't have any leaks or problems, except for a spike in velocity every now and then. probably due to well used internal reg parts.

I'm nitpickin' at you now rrfireblade, but most cocker valves I've seen on new cockers, use a 5/16" orafice at the stem seal, and some use a reduced shaft.with a 5/16" hole, you don't really need the reduced shaft to have more flow area than a 1/4" hole. but the real gig is the flow port that goes from the valve seat to the breech. it is a 1/4". (I've though about making it a bit larger too, but just a bit. much like what AKA has done. match it to the rest of the flow ports through the valve. like porting the heads on a hot rod engine.)

a matrix has a huge port. it is actually .410", with a .177" stem in the middle. this gives it about the approx. flow area of .107 sq. in. about that of a 3/8" hole. but the flaw with the matrix is the absolutely huge expansion area the gas travels through. approx. .82 cu. in. that makes it lose alot of energy, and limits it's efficiency.

the new shaocker actually have the best gas release design. several holes all around the bolt release the air instantly. using only 8.5 cu. in. of air. it operates at 200 psi. but by design, it will never be able to be really efficient, due to the large amount of o-ring friction and high cocking force needed to operate.

with the mag, I've thought about using the ram to push the bolt back, but the more I integrate the idea into the design, the more it starts becoming a spool valve mag.
not that that's bad, just wouldn't use the existing valve at all.

I've though about changing the placement of the power tube o-ring. either putting it farther up the power tube, putting one on the end of the bolt piston. this would keep the bolt from leaking as it moves back and forth, but what would it do to the guns operation? cause bolt stick problems?

I think I'm going to have to sit down and take some measurements. bolt movement, bolt piston placement, actual operating pressure etc...



snertz- the problem with mty idea is that a larger surface area, can leak more too. how much depends on whether or not the pressure can be lowered because of the larger bolt piston, and how much it can be lowered. lower pressure would not leak as much air, but it has more area to leak so it could possibly leak the same amount.

what you describe for a power tube tip, is the old power tube tip design. the nwere ones, the "euro-tip" are rounded, the old ones are not. I don't think it helped flow at all. actualy the new euro tips seem better. but perhaps turbulence could be reduce by making cone shaped end on the bolt piston? that too, might just get in the way of flow.

[Snertz]

I see; I'm not too familiar with the newer euro tip, last time I dealt with a lvl 7 mag was quite a while ago. Do you have a picture of this newer style tip?

You mentioned an oring on the stem of the bolt stem. From what I can recall, the last time I looked at the stem from a lvl 7 bolt, there was a small oring on the stem, but I don't think it was really big enough to proide an effective seal in the powertube.

Again, not sure if this was just an old bolt I saw or soemthing, but it was of the long nose style bolts. Perhaps increasing the size of this oring slightly would acheive a better seal with negligible drag on the bolt itself? Or perhaps expirimenting with different oring materials would yeild one that can seal effectively yet have very low drag.

I think you're right in that a cone shaped end on the bolt stem, or perhaps a shape that is the same as that of the powertube tip would reduce turbulence. ie. cone shape on the end of the bolt stem with the olders style cone/slanted shaped powertube tip; This would have both surfaces parallel to each other, and less of a disruption into the air stream.