logo by smgunner

Crosman999's Sheridan

  << Previous Topic | Next Topic >>Return to Index  

Some old data of interest - 600+ FPE from 12 gr. CO2

June 11 2012 at 10:18 PM
  (Login rsterne)
Crosman Forum Member
from IP address 66.244.241.34

A few years ago I built a 1750 Carbine.... I used an 18" barrel in .177 cal, Crosman steel breech, and a Dual Power Hammer which featured two cocking positions plus a built in RVA.... After a bit of playing around, I found that I could achieve a large measure of self-regulation in the valve using the low power setting by adjusting the RVA.... What I mean is, that it was relatively insenstive to temperature.... Here are the results at the RVA setting with the best balance, at three different temperatures.... JSB 7.8 gr. Express pellets were used....

[IMG][linked image][/IMG]

Note that on high power, the velocity drops with temperature, as expected.... However, on low power, the velocity is pretty constant over nearly a 30*F temperature range.... In fact, the velocity is slightly lower at 75*F than at lower temperatures.... What DOES change is the shot count.... At 75*F, I achieved over 600 FPE from a single 12 gr. CO2 powerlet.... Here is the hammer....

[IMG][linked image][/IMG]

and here is a photo of the completed Carbine....

[IMG][linked image][/IMG]

This shows the adjustment range of the RVA with both power settings.... Note how the velocity curves cross over at about Low-Power 8 or 9.... That is the "self-regulating" range....

[IMG][linked image][/IMG]

and here are some shot strings at various settings.... Note how the average velocity is higher at High-Power 4 than flat out.... and 50% more shots to boot....

[IMG][linked image][/IMG]

Anyway, I just thought you might be interested.... This was pretty much my only serious CO2 gun.... It ended up having the DPH removed, the hammer spring clipped, and is tuned for about 120 shots (70*F) at just under 500 fps as my Canadian-legal indoor target gun....

Bob


    
This message has been edited by rsterne from IP address 66.244.241.34 on Jun 11, 2012 10:24 PM
This message has been edited by rsterne from IP address 66.244.241.34 on Jun 11, 2012 10:23 PM
This message has been edited by rsterne from IP address 66.244.241.34 on Jun 11, 2012 10:21 PM


 
 Respond to this message   
AuthorReply

CO222
(Login CO222)
Crosman Forum Member
118.149.96.66

Congrats, a new record? Very few have made 550,

June 11 2012, 11:42 PM 

search "horsepower second" to see the other contestants. Very well done.

 
 Respond to this message   


(Login bigbore)
Crosman Forum Member
108.132.154.44

475 fpe was the best string I could find...

June 12 2012, 12:34 AM 

although that was a 14" barrel. I think I've done better but this was all I could find right now.

Nice work![linked image]

[linked image]

 
 Respond to this message   


(Login pneuguy)
Crosman Forum Member
98.69.198.150

Very impressive, Bob - especially in .177! 552 is the best I've done, and...

June 12 2012, 8:39 AM 

...that was aided by a much bigger bore volume (.22) and probably more advantage yet from tandem cartridges.

[linked image]

http://www.network54.com/Forum/79537/message/1280101832/110+shots+from+24gms+of+CO2+---+12fpe+QB78+beats+Horsepower-second+-+12gms+efficiency+mark

Congratulations!

Steve

 
 Respond to this message   

(Login rsterne)
Crosman Forum Member
66.244.241.34

I didn't know it was a record!....

June 12 2012, 9:24 AM 

but that's pretty cool.... I've never tried the same thing in .22 cal but in theory there should be a bit more total FPE hiding in there....

And here I thought the coolest part was that it was self-regulating over a wide temperature range....

Bob

PS, I shot two shots per minute....


    
This message has been edited by rsterne from IP address 66.244.241.34 on Jun 12, 2012 9:29 AM


 
 Respond to this message   


(Login pneuguy)
Crosman Forum Member
98.69.198.150

CO2 self-regulation is indeed "cool" (no pun) but often lost....

June 12 2012, 9:31 AM 

...in the enthusiasm for over-springing our CO2 hammers to take max advantage of warm weather, but then have to bundle them off to storage when the weather gets cool.

There are alternatives...

http://www.network54.com/Forum/79537/message/1297468401/CO2+-+30F+to+80F+-+530fps+average+%2B--23fps+stdev

Steve

 
 Respond to this message   

(Login rsterne)
Crosman Forum Member
66.244.241.34

Yes, mild CO2 tunes have advantages....

June 12 2012, 10:29 AM 

I like the looks of your velocity vs. temperature graph in that thread.... 460ish to 560ish between 26*F and 86*F is perfectly usuable.... I didn't explore as wide a temperature range, but the part I did work on showed a similar velocity trend to your experiments.... definitely on the top of the "sweet spot"....

It's interesting that you used a heavy striker with an HDD, whereas I just used a light striker, small travel, and light preload.... and yet we achieved similar results.... Any ideas how you could achieve self-regulation and double the FPE? (other than by increasing the caliber).... It's curious that we are both in the 500 fps range even though in different calibers....

Bob

 
 Respond to this message   


(Login airgunandy)
Crosman Forum Member
206.208.93.60

Re: Yes, mild CO2 tunes have advantages....

June 12 2012, 10:58 AM 

My oldest son has tuned his Sheridan paint ball markers (single 12 gr powered, similar to Benji EB series, but .68 caliber with a repeater mech) so they still work well in cold weather. He seldom plays paintball in sub-freezing weather, but 40 degrees doesn't seem to bother his shooting or the guns'. Not sure what paintballs weigh, but it would seem to need more oomph than a .22 pellet, although to be legal he has to keep it around 300 fps. I believe he uses a lightened striker and non-stock springs.

I plink, therefore I am.

 
 Respond to this message   


(Login pneuguy)
Crosman Forum Member
98.69.198.150

Not just mild tunes - low pressure tunes. The logic behind the heavy hammer is...

June 12 2012, 11:13 AM 

...the notion it's hammer momentum that determines valve duration and gas volume release, but hammer kinetic energy that determines the pressure of maximum volume. Therefore, in order to get a velocity "bell curve" centered at relatively low pressure (a.k.a., for CO2, low temperature) you need a high ratio of momentum to energy.

And the way to get that while still retaining useful muzzle energy, since Momentum = (2 x Mass x Energy)1/2, is to increase hammer mass while decreasing hammer spring energy.

Steve


    
This message has been edited by pneuguy from IP address 98.69.198.150 on Jun 12, 2012 11:16 AM


 
 Respond to this message   
SteveV
(Login stevevines)
Crosman Forum Member
68.52.174.240

Pardon me for pointing out the obvious, but don't you mean 600 fps?

June 12 2012, 11:02 AM 

Seems that some of us are playing fast & loose with our terminology lol? 600 foot pounds of muzzle energy from a co2 pistol?








Vines

 
 Respond to this message   


(Login pneuguy)
Crosman Forum Member
98.69.198.150

Nope - FPE. Bob is referring to the sum of the energy of all the shots he got...

June 12 2012, 11:15 AM 

...from one charge of gas.

Steve

 
 Respond to this message   
SteveV
(Login stevevines)
Crosman Forum Member
68.52.174.240

Okay, now I get it....

June 12 2012, 11:50 AM 


 
 Respond to this message   

(Login curt44319)
Crosman Forum Member
69.221.167.6

Re: Nope - FPE. Bob is referring to the sum of the energy of all the shots he got...

June 13 2012, 2:07 PM 

Which is actually quite high !
Approaching 30% of the theoretical maximum in the powerlet !

http://www.network54.com/Forum/275684/message/1335737040/

 
 Respond to this message   


(Login Arkmaker)
Crosman Forum Member
74.170.102.119

Holy Cow!!

June 12 2012, 11:39 AM 

and I am looking to get just half that (60 shots) at 425/450 fps from one cart!!! Man, I have a long way to go! You the man when it comes to Co2, there is no denying that!!!
Rich

 
 Respond to this message   

Larry
(Login breakfastchef)
Crosman Forum Member
75.139.94.168

I Meant To Tell You About This Thread

June 12 2012, 4:51 PM 

The information fits in perfectly with your 22xx project. But now, with a 1701P in hand, you are likely not going to be messing much with the 22x.

 
 Respond to this message   


(Login Arkmaker)
Crosman Forum Member
74.170.102.119

Oh yes, I will!!! I have been wanting to do that experiment for the longest time!!

June 13 2012, 8:39 AM 


 
 Respond to this message   
Z731
(Login Z731)
Crosman Forum Member
108.57.24.28

RVA and DPH ?

June 12 2012, 7:38 PM 

I give up what are they short for ?

 
 Respond to this message   

(Login rsterne)
Crosman Forum Member
66.244.241.34

Rear Velocity Adjuster and Dual Power Hammer.... n.t.

June 12 2012, 7:56 PM 

Bob

 
 Respond to this message   


(Login pneuguy)
Crosman Forum Member
98.69.198.150

And let's not forget the ever-popular GOBJ.

June 12 2012, 8:47 PM 

Gratuitous Opaque Bewildering Jargon. happy.gif

Steve

 
 Respond to this message   

dan house
(Login dan_house)
Crosman Forum Member
71.210.114.92

hehe Im a computer guy

June 12 2012, 10:45 PM 

got no room to talk about TLAs and FLAs......




dr_subsonic's pneumatic research lab
[linked image]
the Lunatic Fringe of American Airgunning
Southwest Montana's headquarters for Airgunning Supremacy
Proud Sponsor of team_subsonic

 
 Respond to this message   


(Login pneuguy)
Crosman Forum Member
98.69.198.150

An old discussion of the 12gm-Horsepower-second.

June 13 2012, 9:19 AM 


 
 Respond to this message   

(Login rsterne)
Crosman Forum Member
66.244.241.34

Sometimes it pays not to know....

June 13 2012, 10:48 AM 

that something can't be done.... A while back I posted on the CAF about the theoretical 1649 fps velocity limit for expanding room temperature air.... After a LOT of discussion, one of the members took a Condor filled to 2700 psi (air, not Helium), pried the sabot from a .22 cal RWS Hyper Velocity Pellet and blasted the 1.4 gr. piece of plastic through his Chronograph at 1734 fps.... When asked for a repeat, he videotaped it and got two more shots of 1680 and 1701....http://www.youtube.com/watch?v=2jxT8y8-9j8

Bob


    
This message has been edited by rsterne from IP address 66.244.241.34 on Jun 13, 2012 10:51 AM
This message has been edited by rsterne from IP address 66.244.241.34 on Jun 13, 2012 10:50 AM
This message has been edited by rsterne from IP address 66.244.241.34 on Jun 13, 2012 10:49 AM
This message has been edited by rsterne from IP address 66.244.241.34 on Jun 13, 2012 10:48 AM


 
 Respond to this message   

CO222
(Login CO222)
Crosman Forum Member
118.149.171.112

I'm not convinced his air was room temperature

June 14 2012, 12:45 AM 

in the bore. For conservation of energy there must be some localised compression, which results
in what?

 
 Respond to this message   

(Login rsterne)
Crosman Forum Member
66.244.241.34

That was one of the arguments proposed....

June 14 2012, 8:58 AM 

and compressing the small amount of air between the valve seat and the back of the pellet would indeed raise it's temperature.... However, the expansion of the MUCH larger volume of air in the tank which takes place to propel the pellet would surely LOWER the temperature of the total amount of air passing down the bore....

Since the velocity limit is based on the average speed of air molecules at a given temperature, I would think the "limit" would be lower than 1649 fps, not higher.... This experiment remains an anomaly, but one that seriously challenges the idea, IMO....

Perhaps the Siegel (IIRC ?) limit of 5 times the speed of sound is the one that really applies?....

Bob

 
 Respond to this message   


(Login pneuguy)
Crosman Forum Member
98.69.198.150

A couple of comments, just for grins.

June 14 2012, 9:50 AM 

1. The molecular velocity stat' most likely to be relevant is, not the average velocity, but the RMS velocity, since this is the one that corresponds to average kinetic energy.

2. An air temperature of 40C = 104F produces an RMS velocity of 519m/s = 1703fps, and air reservoirs are often this warm (or even far warmer) after a recent fill.

http://hyperphysics.phy-astr.gsu.edu/hbase/kinetic/kintem.html

3. There are many ways to inadvertently perturb the calibration of the readings from a Shootin' Chrony chronograph by 6% (or more), and 1750/1650 = 1.06.

[linked image]

Steve


    
This message has been edited by pneuguy from IP address 98.69.198.150 on Jun 14, 2012 9:54 AM
This message has been edited by pneuguy from IP address 98.69.198.150 on Jun 14, 2012 9:53 AM


 
 Respond to this message   

(Login rsterne)
Crosman Forum Member
66.244.241.34

It could be a Chrony error....

June 14 2012, 10:12 AM 

and a host of other things, like the base of the plastic pellet burning from the compressed air in the transfer port.... or some sort of venturi effect somewhere (although Condors have pretty much a straight through port).... However, when you consider that the 1647 fps value would require 100% transfer of molecular velocity to the pellet, any value approaching that would tend to raise one's eyebrows.... BTW, here is the calculator I used to get the 1647 fps for the RMS value at 20*C....

http://hyperphysics.phy-astr.gsu.edu/hbase/kinetic/kintem.html#c4

I don't have a horse in this race.... although I must admit I thought the "limit" made perfect sense.... I started the thread at the CAF out of interest because the "1650 limit" was posted on yet another Forum.... and somebody at the CAF with a Condor took up the challenge.... Now I'm not so sure.... Theories are only valid until disproven (not saying that is the case with certainty).... and then it's time to find a new theory to go with the facts, if necessary....

When you consider what happens to the BC of waisted (diablo) pellets in the Transonic region (over Mach 0.8-0.85, 900-950 fps) where it drops like a stone.... I don't really care anyway.... If anything I shoot approaches 1000 fps, I look for a heavier pellet....

Bob


 
 Respond to this message   

(Login CalG)
Crosman Forum Member
24.128.138.174

I've thought about this Average velocity and Sonic horizon thing.

June 15 2012, 7:07 PM 

For full 1/2 of the molecules in the energy distribution are going faster than these average values.

Certainly they have a push of their own. Or else we are saying that 1/2 the energy of momentum is too slow to have much effect on pushing the pell down the bore.

And that would put the math all in a tumble!

Remember, half the doctors graduating from medical school are below average! wink.gif

 
 Respond to this message   

(Login rsterne)
Crosman Forum Member
66.244.241.34

You know, that could be it!....

June 15 2012, 7:49 PM 

The efficiency of the Condor shot was only about 3%, IIRC.... Maybe that was because only a small percentage of the air was moving fast enough to push the pellet over 1700 fps.... After all, the RMS velocity is just a point in the Maxwell Speed Distribution of velocities in a gas at a given temperature.... and in fact a small percentage of molecules are moving more than twice as fast as the RMS value....

Perhaps with enough data we would see not a hard and fast "limit" but just a very rapid tapering off of the possible velocity as fewer and fewer air moelcules are moving fast enough to provide additional acceleration.... Just a thought....

Bob

 
 Respond to this message   

(Login CalG)
Crosman Forum Member
24.128.138.174

The number moving 2X is not that small...perhaps approaching 25%

June 15 2012, 9:54 PM 

not insignificant in light of achieved efficiencies.

 
 Respond to this message   

(Login rsterne)
Crosman Forum Member
66.244.241.34

I was just estimating from the curve....

June 15 2012, 10:25 PM 

shown on this calculator....http://hyperphysics.phy-astr.gsu.edu/hbase/kinetic/kintem.html#c4

Assuming it's to scale, there is a small but finite area to the right of the point double the distance from the "Y" axis (zero speed) to the RMS value.... Of course the diagram may not be to scale....

Bob

 
 Respond to this message   

(Login CalG)
Crosman Forum Member
24.128.138.174

On the CED Chronometers, the sensor is sunk far into the housing

June 14 2012, 1:29 PM 

That this angle sensitivity example is not likely to be relevant.

 
 Respond to this message   


(Login pneuguy)
Crosman Forum Member
98.69.198.150

Since the chrono in the video is a "Shooting Chrony," I'm afraid...

June 14 2012, 4:43 PM 

...I'm missing the relevance of your comment.

[linked image]

As the owner of one, I can personally testify to the (embarassing) sensitivity of that brand to lighting angle errors!

Steve


    
This message has been edited by pneuguy from IP address 98.69.198.150 on Jun 14, 2012 4:45 PM


 
 Respond to this message   

(Login rsterne)
Crosman Forum Member
66.244.241.34

From the horse's mouth, as it were....

June 15 2012, 9:01 AM 

I contacted the chap who tested the 1.4 gr. sabot in his Condor with the concerns over temperature and lighting.... Here is his response....

"1) the gun had not been filled "recently" it had been sitting for at least an hour in a air conditioned basement which was at most 18-20*C
2) The Chrony was setup with the lighting system and diffusers sold/made by Chrony, not that that means there is no chance of error, but the light is quite close to the sensors maybe 10-12"??"

As I said, I have no horse in this race.... so don't shoot the messenger....

Bob

 
 Respond to this message   

(Login CalG)
Crosman Forum Member
24.128.138.174

Only a comment on options A side bar.... distraction from the thread

June 15 2012, 5:47 PM 


 
 Respond to this message   

CO222
(Login CO222)
Crosman Forum Member
118.149.48.9

Exactly, expansion of the "MUCH larger" tank is negligible.

June 15 2012, 10:10 PM 

The larger the tank the more it resists pressure drop & cooling. The tank pressure might only
drop 2-3%. Even a lowly pulse jet compresses the air column more than this.


 
 Respond to this message   

(Login rsterne)
Crosman Forum Member
66.244.241.34

I meant to say....

June 15 2012, 10:42 PM 

the much larger volume of air (maybe 5 cc at 186 bar = nearly a litre when expanded) released by the valve FROM the tank (which air then cools as it expands).... compared to the very small amount of air (maybe 1.0 cc at 1 bar) in the transfer port area (which heats as it is compressed).... Surely the net temperature change is a decrease, not an increase....

I was not implying that the air in the tank (500 cc @ 186 bar = 93 litres) changed temperature drastically, it wouldn't.... That wouldn't affect the temperature of the air in the barrel anyway (until the next shot)....

Bob

 
 Respond to this message   

CO222
(Login CO222)
Crosman Forum Member
118.148.247.116

That's why I say localised not nett effect.

June 16 2012, 3:25 AM 

Yes if there was enough time for temperature to equalise there would be a nett drop.
I only reached 1558fps with 6gr the traditional way, I need to purpose build an extremely over-powered
rig to test the heating theory conclusively.


 
 Respond to this message   
Anonymous
(Login jgoodz)
Crosman Forum Member
24.57.38.169

I have done a few times with the same setup

June 17 2012, 12:43 AM 

I am the creator of this video in question...


There are no tricks at play and my Chrony/lighting is working just fine. I only recorded this as I have seen velocities over 1650FPS and figured others may be interested to see it is quite possible...


I am not going to get into a heated debate over it as it really doesn't matter to me, but sometime when I get a chance I will create a video testing this with the same gun/sabots using three different brands of chronographs, just to remove all claims of inferior equipment...


Cheers,

 
 Respond to this message   
Current Topic - Some old data of interest - 600+ FPE from 12 gr. CO2
  << Previous Topic | Next Topic >>Return to Index  

Crosman Corporation 1-800-724-7486