Valve 2100 vs 13xx

Ryan · 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?

BDS · January 16, 2014, 10:44:12 PM

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.

Ryan · January 16, 2014, 10:52:51 PM

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.

K.O. · January 16, 2014, 11:24:43 PM

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.

1377x · January 16, 2014, 11:25:40 PM

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

K.O. · January 17, 2014, 07:09:27 AM

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 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

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...

Ryan · January 17, 2014, 04:35:19 PM

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.

BDS · January 17, 2014, 06:38:38 PM

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.

Ryan · January 17, 2014, 08:44:26 PM

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

K.O. · January 18, 2014, 02:14:37 AM

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.

K.O. · January 18, 2014, 02:21:02 AM

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?

K.O. · January 18, 2014, 02:29:51 AM

just a touch more in a while I need a break...

Ryan · 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

BDS · January 18, 2014, 04:36:09 AM

You forgot...

Good with...

Tools, machinery, crafting good stuff out of junk stuff = Airgun addict

Davio · January 18, 2014, 04:37:11 AM

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...