The 2100 valve is comparatively much shorter than the 13xx's, but the 2100 has a much bigger swipe volume. Can someone shed some light on the output between a bigger swipe volume/smaller valve and 13xx valve with a smaller swipe volume/bigger valve.
If I put a 13xx value into a 2100, would that generate a higher output than the original smaller valve, or I will be better off using the 2100 smaller valve ? Thanks in advance
I don't know about the comparisons, but the 2100 valve just has a shorter front section, they have the same internal components just a shorter section between the valve face and check valve.
I see
I am using a 2100 pump tube for the base of my 1325XLT project and have reason (in my mind) to think I will be getting about 625 fps using H&N
20g pellets.
BUT,
I am going about it in a convoluted way...
I am notching the exhaust section of of the 2200 valve to allow it to be moved back .3"
A modded 760( shortened and air cavity extended into nose, a copy of 2200 nose but .3" longer) nose will be used for the front which will allow me to keep the pump stroke long...
you can not use the 13xx nose because of the hole in the nose for attaching the front of the grip frame...
Because I will have a 1/3 larger air chamber and the same stroke I will have to pump + 1/3 more time to reach the same pressure...
If you use a 13xx piston in a 2100 you can nocth the back and move it back a bit but the exast poppet shaft is already pretty short so that means you
would have to use an adjustable/custom piston and shorten the stroke
that and with the increased valve volume would mean more pumping...
How much...
You should do your own simple math... pi(r2)l = V
Oh I did not think it all the way thru
you are talking about in a 2100 and if so you can not move the valve back.
So honestly unless you are building a 2100/13xx hybrid, I do not think it is worth the effort...
KO,
The 2100 out of a box is shooting at say 650 fps in .177. If everything being equal, the same gun would do say 500+ in .22. What I am trying to achieve is to build a 2100 with a 13xx trigger frame but to shoot a .22 in 600+. The key to this is obviously in the valve and to make use of the long stroke.
I have seen many many write-ups on a 2100 tube on a 13xx frame going at 650 fps on .22s. The 2100 valve is about half the size of that of a 13xx's. So locking it to the 13xx frame is impossible. Using a 13xx valve will obviously defeat the long stroke purpose. Unless I tweak a hybrid valve, I have no alternative but to use the original 2100 valve. That will put back to a stock 2100 again, running around in circle. Any idea?
Quote from: Ryan on January 16, 2014, 01:07:29 AM
KO,
The 2100 out of a box is shooting at say 650 fps in .177. If everything being equal, the same gun would do say 500+ in .22. What I am trying to achieve is to build a 2100 with a 13xx trigger frame but to shoot a .22 in 600+. The key to this is obviously in the valve and to make use of the long stroke.
the stock 2200 will hit 600 fps and the first gens more it is the same power plant as the 2100 so if 600 fps is your goal the stock 2100 valve will get the job done in ten pumps.
In fact the 2100/2200 has some leaking probs and could use some fixes that will gain you 50-70 fps making a 1322/2100 will fix many of those problems and if you get it right(springs, porting etc) you just might hit 640-650 fps with a 18" barrel.
I put a flat top valve and piston in a buddies old leaky 2200 and it hit the mid 620s. you can not flat top the 2200 valve because the air chamber extends into the nose so big bore Bart on the gta made a few noses. He still might have a few? I just fit and shim the cup to the valve for no headspace.
http://www.pyramydair.com/blog/2009/02/testing-crosman-2200-part-2.html (http://www.pyramydair.com/blog/2009/02/testing-crosman-2200-part-2.html)
http://www.network54.com/Realm/CFTech/FB22002.htm (http://www.network54.com/Realm/CFTech/FB22002.htm)
I have seen many many write-ups on a 2100 tube on a 13xx frame going at 650 fps on .22s. The 2100 valve is about half the size of that of a 13xx's. So locking it to the 13xx frame is impossible. Using a 13xx valve will obviously defeat the long stroke purpose. Unless I tweak a hybrid valve, I have no alternative but to use the original 2100 valve. That will put back to a stock 2100 again, running around in circle. Any idea?
on the inside you can do a few thing to gain some volume with the 2100 valve also.
I wanted to use a 13xx valve for my 1325 project because the .25 does need more air and it is easier to add volume than pressure.
using a 13xx valve can be done but you have to sleeve the 2100 pump tube to extend it and the make a new sear and a few other things also would need to drill out the valve retention hump in the 2100 pump tube.
but remember the reason to use a 2100 pump tube is to reduce the number of pumps needed and I do not feel that in .22 unlees going for over 700 fps using the 13xx valve is necessary. there is the advantage of getting the front pistol grip screw mount back though. that screw hole prevents the 13xx nose from being open like the 2200 , trade offs...
Big Bore Bart will be modding a 760 nose for me it is the same as the 13xx nose except no screw hole in the nose so extending the air cavity up into the nose and making it into a copy of a 2100 valve but with a .3" longer nose will give me the volume I need for the .25 bore. the bottom of the valve will be notched so I can move it back that same .3 That is how far back I can mount the breech using the 2100 tube without extending it.
Here is a thread where Bart outlines the 2100 flat top valve cap and gets 870fps from a modded 766(2100 family/predecessor ) @ 16 pumps with 7.9g pellets
http://www.gatewaytoairguns.org/GTA/index.php?topic=54854.0 (http://www.gatewaytoairguns.org/GTA/index.php?topic=54854.0)
Honestly I am on just my 3rd project but to figure things out
your best friends will be...
good search skills
a Vernier caliper
knowing how to find the volume of a cylinder
and knowing how to find the area of a circles
and Boyle law.
with those you can gain a pretty fair Idea of how to go about these mods,,
IMO...
Valve work is an art, just as much as science. Here's an old-school gun..
Crosman Model 1-2280, re-built by Jeff Wolgast with 2260 polished & crowned barrel set screwed in-place, bolt change with o-ring, sealed transfer mod, modified high capacity valve and pumping sequence changed to "cock before pumping" style.
.22 cal 14.5g CPs go 376 fps on 3 pumps, 455 fps on 6 pumps, and 629 fps on 10 pumps.
When I saw that one I had a real hard time passing it up but Christmas and a couple birthdays were coming up plus I really wanted to do a .25 pumper.
It was well worth the 200$ that was asked, heck just a replacement walnut stock is about 65$
I am glad it is with you, when you first showed it here I did not regret passing on it as much. The last time I had a 2200 was in the early 80s
Yours and the first gens are the best.
It would seem that he did not go all out when adding volume because even when offset by headspace reduction it would show at the lower pumps.
Seeing the figures on it helps me keep a bit of my confidence.
On my project what I am doing is basically taking a tuned 2200 like yours adding 1/3 more to the valve volume and porting the heck out of it in
order to get it to send 18.1g .22 pellets down range at 12-15 pumps at the same fps.
Hi BDS,
How did you install a 2260 barrel into a typical 2200/2100 clam-shell action? You pretty well have to gut the 2200 internals in order to hide a chopped-up Crosman steel or plastic breech inside the clam-shell, right?
A 1377 valve can be nodded to fit/work in a 2100 as long as its flat topped. Looks easier than what the guy on its did. I have the plans to do the mod
1377x,
You mind elaborating on your grand scheme of things? I have read somewhere that half of a 1377 valve is matted to a 2100 or 760 half to make it more potent.
Quote from: 1377x on January 16, 2014, 07:50:36 PM
A 1377 valve can be nodded to fit/work in a 2100 as long as its flat topped. Looks easier than what the guy on its did. I have the plans to do the mod
yep but you would have to shorten it or the pump stroke by about .410-.420 or so I think
Is there much meat left betwee the valve face and check poppet seat?
this is assuming the flat top is machined just behind where the bolt hole is?
Quote from: Ryan on January 16, 2014, 08:11:01 PM
1377x,
You mind elaborating on your grand scheme of things? I have read somewhere that half of a 1377 valve is matted to a 2100 or 760 half to make it more potent.
Link?
K.O.
As you have said, I have researched into different forums and gathered tits bits of techno here and there. I do not recall where did I come across the matting of a 13xx valve with a 760 valve. To tell you the truth, I am baffled with the prospect of enlarging vs reducing the valve volume. I am sure each has its merits, but I am confused. I wished I had paid a little more attention to physics classes back in high school. I was real good with maths and algebra and I have been making a living with them now. I guess I have to do a freshen up on the Boyd's law if I wanted to have a better understanding of the relationship amongst swipe volume>valve volume>psi>volume of air released, huh.
I have 2 alu 13xx valves, 1 brass 13xx valve and 1 each of a 760 and a 2100. Out of curiosity, I measured the internal length of the valve cavity and found the followings. My measurements are performed with a high end micrometer minus the overlapping thread length. It bugs me when I don't understand something. It bugs me when I don't understand something.
Aluminum 12.95"
Brass 13.30"
2100 5.82"
760 7.53"
I wonder why the 2100 would have the smallest valve volume and yet perform much better than a 13xx?
Quote from: Ryan on January 16, 2014, 07:19:36 PM
Hi BDS,
How did you install a 2260 barrel into a typical 2200/2100 clam-shell action? You pretty well have to gut the 2200 internals in order to hide a chopped-up Crosman steel or plastic breech inside the clam-shell, right?
"I" didn't... Mr. Wolgast was an old school tuner that modified the Crosman Classic and model 1-2280 guns as well as the 2200 guns. I bought the gun a few months ago from a guy who had 2 of them, it was "new in box" except for the Wolgast mods. (gun was literally never used after the mods, and 30 years old but looked like day one from the factory)
I do know that the gun has to be cocked to pump, there is a small set screw in the barrel shroud, and set screws added internally along with extended probe and an o-ring set that the original Crosman design did not have. Back around 2002 / 2005 there were a few "crazier" guys who took the Wolgast guns and did even more work on the valves to achieve about 700 fps with 15g pellets. They were kinda "fringey" for their time and it's hard to find info on them except they were mostly hunters, not target shooters or bigtime forum members.
Do you load your hybrid 2200 through the sliding gate? I guess Wolgast must have retained the original plastic connector that connects the exhaust port from the pump tube to the loading port. If he did, he must have milled the 2260 barrel to connect to the plastic loading piece. The oem 2200 did not come with a barrel, but a thin steel tubing that has rifling in it.
Quote from: Ryan on January 16, 2014, 09:48:35 PM
K.O.
As you have said, I have researched into different forums and gathered tits bits of techno here and there. I do not recall where did I come across the matting of a 13xx valve with a 760 valve. To tell you the truth, I am baffled with the prospect of enlarging vs reducing the valve volume. I am sure each has its merits, but I am confused. I wished I had paid a little more attention to physics classes back in high school. I was real good with maths and algebra and I have been making a living with them now. I guess I have to do a freshen up on the Boyd's law if I wanted to have a better understanding of the relationship amongst swipe volume>valve volume>psi>volume of air released, huh.
I have 2 alu 13xx valves, 1 brass 13xx valve and 1 each of a 760 and a 2100. Out of curiosity, I measured the internal length of the valve cavity and found the followings. My measurements are performed with a high end micrometer minus the overlapping thread length. It bugs me when I don't understand something. It bugs me when I don't understand something.
Aluminum 12.95"
Brass 13.30"
2100 5.82"
760 7.53"
I wonder why the 2100 would have the smallest valve volume and yet perform much better than a 13xx?
I have to go but will try to explain when I get back.
Quote from: K.O. on January 16, 2014, 09:02:53 PM
Link?
No link. I got the plans from rsterne. I have pm'd them to some members. I'll see if i can dig them out
Quote from: Ryan on January 16, 2014, 09:48:35 PM
K.O.
As you have said, I have researched into different forums and gathered tits bits of techno here and there. I do not recall where did I come across the matting of a 13xx valve with a 760 valve. To tell you the truth, I am baffled with the prospect of enlarging vs reducing the valve volume. I am sure each has its merits, but I am confused. I wished I had paid a little more attention to physics classes back in high school. I was real good with maths and algebra and I have been making a living with them now. I guess I have to do a freshen up on the Boyd's law if I wanted to have a better understanding of the relationship amongst swipe volume>valve volume>psi>volume of air released, huh.
I have 2 alu 13xx valves, 1 brass 13xx valve and 1 each of a 760 and a 2100. Out of curiosity, I measured the internal length of the valve cavity and found the followings. My measurements are performed with a high end micrometer minus the overlapping thread length. It bugs me when I don't understand something. It bugs me when I don't understand something.
Aluminum 12.95"
Brass 13.30"
2100 5.82"
760 7.53"
I wonder why the 2100 would have the smallest valve volume and yet perform much better than a 13xx?
your measurements are way off the decimal point is in the wrong place and the 2100 makes no sense.
Ok first BOYLES law.
For a fixed amount of an ideal gas kept at a fixed temperature, pressure and volume are inversely proportionalwhich means double the volume half the pressure,
or half the volume double the pressure and so on...
so say the 13xx valve has an intierior cavity 1.42 long and .365 diameter.
the formula for volume is pi x radius
2 x length
so we have 3.14 x (.365 x .5) x 1.42 = .15ci for the volume
we use the same formula to figure out the pumps swept volume 3.5" long by .6 diameter
so 3.14 x (.6 x .5) x 3.5 = .9891 ci for the swept volume
swept vol + valve vol = total volume
so
.15ci + .9891ci = 1.13
so every pump stroke is squeezing 1.13ci of air into a space of into .15 ci ( I'm rounding again)
1.13 / .15 = 7.53... ending volume is this much smaller than beginning volume.
so by Boyles law means we can take atmospheric pressure of say 14.3 psi x 7.53 and learn we get about 107.67 psi per stroke
after 10 strokes 1076 or so psi stored in a container of .15ci
---------------------------------------------------------------------------------------
ok so now do the same math for the 2100...
say with a valve volume of .11 and a pump that is the same diameter(.6") but has a stroke of 5"
after you post what you get for psi per stroke you get, we will move on to what happens upon release of that psi into the barrel using the same sort of math...
K.O.
Thanks for clarifying the Boyd's law. This reaffirms my suspicion that given the same # of swipe volumes, the smaller the cavity the higher the pressure generated. It's nice to know the inversing attribute. The formula also helps to guide me in designing and achieving the result desired.
Ryan, KO spelled it out very well, it's the same set of "rules" that requires that tiny hose on a 4k PSI fill tank for PCP guns. High pressure and low volume, vs. a shop compressor at 150 psi and high volume.
It's simple when illustrated, but not immediately obvious. It's why so many new PCP gun owners get frustrated about pumps and bottles, they think in terms of PSI only or volume only.
I am getting there, slowly. I was busy this morning to get something out at work. I just worked out the followings for a 2100
Valve volume = .11 as you suggested
Stroke volume = 3.14 x .3 square x 5 = 1.413
Combined volume = .11+1.413 = 1.523
ending volume = 1.523 / .11 = 13.85
10 pumps give 14.3 x 13.85 x 10 = 1,981 psi
I can see that the pellet weight is blended into the resulting psi. So what does the resulting psi mean and how does it translate into the force pushing the 14.3 gr pellet? I guess the length of the barrel would also come into the equation as well. TIA
Ok first of all I am going to though my little hissy fit and tell you if you call it Boyds law one more time... (I would toss family in the nearest pond or give a swift kick)...
repeat after me...
BOYLES LAW, BOLYES LAW, BOYLES LAW,
Ok got it out of my system... ;)
Barrel Length 0.177 0.22 P.S.I.= 1981
Barrel Vol Barrel PSI Barrel Vol Barrel PSI valve size ci. 0.11
1 0.024593265 1619.026034 0.037994 1472.424558
2 0.04918653 1368.89723 0.075988 1171.634729
3 0.073779795 1185.712499 0.113982 972.8906787
4 0.09837306 1045.768584 0.151976 831.7937521
5 0.122966325 935.3712387 0.18997 726.4393106
6 0.14755959 846.0566349 0.227964 644.772816
7 0.172152855 772.3118733 0.265958 579.6126163
8 0.19674612 710.3920336 0.303952 526.4136905
9 0.221339385 657.6640444 0.341946 482.159373
10 0.24593265 612.2225651 0.37994 444.7687472
11 0.270525915 572.6548217 0.417934 412.7599283
12 0.29511918 537.8910966 0.455928 385.0489815
13 0.319712445 507.1065605 0.493922 360.8247423
14 0.34430571 479.6549883 0.531916 339.4680924
Barrel Length 0.177 0.22 P.S.I.= 1076
Barrel Vol Barrel PSI Barrel Vol Barrel PSI Valve size ci. 0.15
1 0.024593265 924.4342844 0.037994 858.5380384
2 0.04918653 810.2957564 0.075988 714.197214
3 0.073779795 721.2447397 0.113982 611.4053231
4 0.09837306 649.8289307 0.151976 534.4795613
5 0.122966325 591.2817268 0.18997 474.7477719
6 0.14755959 542.4123618 0.227964 427.024796
7 0.172152855 501.0044067 0.265958 388.0199443
8 0.19674612 465.4702409 0.303952 355.5441985
9 0.221339385 434.6428268 0.341946 328.0847898
10 0.24593265 407.6450881 0.37994 304.5627807
11 0.270525915 383.8051217 0.417934 284.1879514
12 0.29511918 362.5995177 0.455928 266.3682814
13 0.319712445 343.6144852 0.493922 250.6514764
14 0.34430571 326.518583 0.531916 236.6860434
This is just the way that the smaller valve at the higher pressure performs compared to the bigger valve at lower pressure.
the barrel volume equation is the same one we used before.
pi x radius2 x length
so having that and a beginning PSI
and knowing,
Starting volume = valve volume
beginning psi/(( (pi x(r2) x length)+ valve vol)/ valve vol )
gives the psi at a given barrel length.
well it looked straight in the editing...
sorry it did not post that way...
eccel starter to tab text to clipboard to editing here... ... ...
well is still understand able?
just a touch more in a while I need a break...
K.O.
I got it now. Thanks,
You know what, kids that are good in
maths and algebra become accountants
maths, algebra and physics become engineers
physics, chem and bio become doctors
BS become lawyers
Bullying become cops
I fell short of physics
You forgot...
Good with...
Tools, machinery, crafting good stuff out of junk stuff = Airgun addict :D :-*
Quote from: K.O. on January 17, 2014, 07:09:27 AM
Ok first BOYLES law.
For a fixed amount of an ideal gas kept at a fixed temperature, pressure and volume are inversely proportional
which means double the volume half the pressure,
or half the volume double the pressure and so on...
so say the 13xx valve has an intierior cavity 1.42 long and .365 diameter.
the formula for volume is pi x radius2 x length
so we have 3.14 x (.365 x .5) x 1.42 = .15ci for the volume
we use the same formula to figure out the pumps swept volume 3.5" long by .6 diameter
so 3.14 x (.6 x .5) x 3.5 = .9891 ci for the swept volume
swept vol + valve vol = total volume
so
.15ci + .9891ci = 1.13 HOW CAN THE VALVE VOLUME POSSIBLY BE RE-ADDED FOR EVERY CONSECUTIVE PUMP CYCLE (AS PART OF YOUR "TOTAL VOLUME")? PLEASE EXPLAIN.
so every pump stroke is squeezing 1.13ci of air into a space of into .15 ci ( I'm rounding again)
1.13 / .15 = 7.53... ending volume is this much smaller than beginning volume.
so by Boyles law means we can take atmospheric pressure of say 14.3 psi x 7.53 and learn we get about 107.67 psi per stroke
after 10 strokes 1076 or so psi stored in a container of .15ci
---------------------------------------------------------------------------------------
ok so now do the same math for the 2100...
say with a valve volume of .11 and a pump that is the same diameter(.6") but has a stroke of 5"
after you post what you get for psi per stroke you get, we will move on to what happens upon release of that psi into the barrel using the same sort of math...
Ok so we answered your original question,
"I wonder why the 2100 would have the smallest valve volume and yet perform much better than a 13xx?"
Now the thing is if you have the high pressure and the larger valve and enough barrel :) :) :) :)!
I have to say all this is greatly simplified to the point of not being accurate to actual results but does show the concepts and gives a pretty decent
approximation of what is going on.
I was told that in this next part Sectional density is what I should use but I have never seen it used in internal ballistics, only external and terminal.
I should also state that my brief survey of ballistics was long ago...
so this next part is my method and I winged it you will need to substitute 14.3g and convert to what you prefer I chose grams because I can
visualize grams being pushed by foot pounds easier than .00sumthin pounds being pushed.
so you take the numbers from developing the index and they are one leg of the graph and the barrel length is the other
and you will have an approximation of the acceleration curve of the pellet.
you can stop at knowing there is this much force on this much weight at a given length into the barrel...
the index thing is just a way to compare different calibers and weights of pellets...
All this is vastly simplified but does help build an understanding of what is going on...
and the surface area acted on is just found by the area of a circle/caliber
http://www.gatewaytoairguns.org/GTA/index.php?topic=59377.20 (http://www.gatewaytoairguns.org/GTA/index.php?topic=59377.20)
"HOW CAN THE VALVE VOLUME POSSIBLY BE RE-ADDED FOR EVERY CONSECUTIVE PUMP CYCLE (AS PART OF YOUR "TOTAL VOLUME")? PLEASE EXPLAIN"
Hi Davio if you look it is not...
It is just used to get the pumps starting to ending ratio.
and then that is used as the multiplier of atmospheric pressure...
I see that, but the valve itself is isolated (mechanically by the spring pressure on the check valve) from the amount of air being pushed into it. I consider the valve the receiving vessel only and again isolated from pump stroke calculations. What do I know? ???
And Pi R not square! They are round. :)
Quote from: Ryan on January 18, 2014, 04:31:51 AM
K.O.
I got it now. Thanks,
You know what, kids that are good in
maths and algebra become accountants
maths, algebra and physics become engineers
physics, chem and bio become doctors
BS become lawyers
Bullying become cops
I fell short of physics
LONG a** story but just a misfit who's kids survived him and are crazy enough to still love him...
Did do a internship cobol/cics using vsam and os-jcl at Tacoma public uttil.
Most of my math was self taught and am just falling behind my math major daughter on (Ring theory)
Honestly this is the easy stuff and I can still get things wrong I have some brain probs(concentration) now (to many concussions?)
Quote from: Davio on January 18, 2014, 06:24:47 AM
I see that, but the valve itself is isolated (mechanically by the spring pressure on the check valve) from the amount of air being pushed into it. I consider the valve the receiving vessel only and again isolated from pump stroke calculations. What do I know? ???
And Pi R not square! They are round. :)
You cannot look at it that way were does the air go...
It adds that much air (at a certain efficiency which probably falls as pressure rises) every stroke but the ratio stays the same and the check valve just keeps it contained in the valve.
this is just a basic model and leaves out a lot butcan show ballpark figures.
Quote from: K.O. on January 17, 2014, 07:09:27 AM
so by Boyle law means we can take atmospheric pressure of say 14.3 psi x 7.53 and learn we get about 107.67 psi per stroke
K.O.
I always go back to refresh myself after leaning something new, just to make sure I flow through with the logics. I now understand the principles behind the Boyle's law, but where does the 14.3 psi come from? Is this the weight of a .22 pellet? Thanks,
Quote from: Ryan on January 18, 2014, 06:26:47 PM
K.O.
I always go back to refresh myself after leaning something new, just to make sure I flow through with the logics. I now understand the principles behind the Boyle's law, but where does the 14.3 psi come from? Is this the weight of a .22 pellet? Thanks,
Ryan I just pulled that figure out of the air(pun intended)...
but it is a very likely number...
http://en.wikipedia.org/wiki/Atmospheric_pressure (http://en.wikipedia.org/wiki/Atmospheric_pressure)
ok, now I can put the various attributes together. The 14.3 is the link between the volume and atmospheric pressure. It is close enough to 14.696 psi per unit of atmospheric pressure. Thanks,
that pressure varies from day to day with the weather and at differing altitudes
http://www.engineeringtoolbox.com/air-altitude-pressure-d_462.html (http://www.engineeringtoolbox.com/air-altitude-pressure-d_462.html)
Now that I know the inter-relationship between the valve and swipe volumes, I have to figure out a way to get the best of both worlds.
My ideal is to lengthen the stroke length with an adjustable piston, a hybrid valve which is a cross between a 2100 and a 13xx's and to make use of a 13xx trigger frame.
I don't think the 2100 tube would let me do it. I may have to find a new tube with the same id and to machine the slots and holes into the new tube. I will shorten the pump arm slot in order to lengthen the pump stroke with an adjustable flattop piston. In order to make use of the 13xx trigger frame, I will also need a new flattop valve head with a sold internal so that the valve cavity will remain slightly larger than that of a 2100 valve. I may have to machine a check valve with a long pin attached to it as Wyo has just suggested to reduce the head space loss.
Just dreaming for now. I will get there once I have a little peace of mind and time... may be after April.
Given the weight of a pellet, is it possible to translate a barrel psi into FPE?
I realize the fpe could be determined by putting the gun through a chrony. It would be nice if it could be established by blending the barrel psi with the weight just so that the desired fpe could be pre-determined.
Am I asking for too much?
You can form an educated guess but it takes building a data base for that gun all this is just to get a theoretical psi each pump is going to be slightly to very different in how efficient it is especially once it starts building high pressure .
Quoting Big Bore Bart from a GTA thread
" The math is standard compression ratio stuff, and it works better in metric. ::) (Pump area x stroke + valve volume)/(valve volume - headspace) =CR. CR x 14.7 = pressure rise in the valve per stroke. P/R x # strokes = theoretical valve pressure. Theoretical pressure x pump efficiency = valve pressure. I personally use ~65% as a pump efficiency fudge factor. ;D Calculating the actual pump efficiency is not doable with out a gauge in the system. :D "
I like Decimal more than metric just the way my mind works. (besides the point)
but
Pre charged pneumatics have a pressure gage and you can build a good understanding but it has to be for each gun. and then with pellets well there are variations of up to .3 grains or so in weight also variations in head size.
I am giving a slightly educated guess about my projects estimated fps/fpe but it was not the math that guided my choices as much a my experiences and then the math helped bolster my opinion.
But so much rides on pump efficiency that in the end that will decide what I get.
Let me take my time to digest this. Thanks anyway.
What I was thinking is if I wanted a 9 fpe with a given pellet weight and if there was a relationship between fpe and the barrel psi, I could then reverse engineer the 9 fpe into the optimum valve and stroke volume ratio, etc. Wouldn't that be nice?
Re" Quoting Big Bore Bart from a GTA thread
" The math is standard compression ratio stuff, and it works better in metric. ::) (Pump area x stroke + valve volume)/(valve volume - headspace) =CR."
What is CR?
Quote from: Ryan on January 19, 2014, 05:32:33 AM
Re" Quoting Big Bore Bart from a GTA thread
" The math is standard compression ratio stuff, and it works better in metric. ::) (Pump area x stroke + valve volume)/(valve volume - headspace) =CR."
What is CR?
1.13 / .15 = 7.53... ending volume is this much smaller than beginning volume. (7.53 is the CR, compression ratio)
What I was thinking is if I wanted a 9 fpe with a given pellet weight and if there was a relationship between fpe and the barrel psi, I could then reverse engineer the 9 fpe into the optimum valve and stroke volume ratio, etc. Wouldn't that be nice?
The easy way is to read how others have achieved their level of performance and understand the whole system.
I get about 10 fpe out of my 1322 @17 pumps with 14.3g pellets, it is a balance of valve volume, # of pumps, hammer and valve spring balance to dump it, port size, pellet caliber/weight and barrel length.
It is the system as a whole and how you want to get there...
I can not resist here are a couple port size threads to fry our brains just a touch more...
http://www.network54.com/Forum/275684/message/1386883683/Noodling+about+transfer+ports+and+supersonic+flow. (http://www.network54.com/Forum/275684/message/1386883683/Noodling+about+transfer+ports+and+supersonic+flow.)
http://www.airgunhome.com/agforum/viewtopic.php?p=78260 (http://www.airgunhome.com/agforum/viewtopic.php?p=78260)
KO, Thanks for all the heads up. I think I have a pretty good grasp of the msp logistics by now. Work is getting pretty thick in the office. I will have to wait till early spring to do some real modding.
One last heads up...
"My ideal is to lengthen the stroke length with an adjustable piston"
Nope stroke length is determined by GEOMETRY look for the Triangle and what happens to it...
and that is joined to pump effort...
also think about leverage and pump effort and valve size/pressure
the 2100 has the leverage to make the long stroke low volume higher pressure valve comfortable to use...
the 13xx unless you are willing to have your pump longer than the barrel does not have that leverage so the higher volume lower pressure approach is used.
there are threads just on this subject of course but heck you can go there at your leisure...