Quick 2289g experiment.

[DavidS]

Going to through an increased volume valve that I have into my Crosman 2289g and play with the springs a little today.    My goal is to be able to get two shots of decent power (greater than 10FPE) and still have a little air in the valve, so this is an experiment in ACP.

I will also finaly get arond to trying the poly tube transfer port (now it has a bored out stock transfer port with a top side O-Ring).

We will see the results.

[Rivers3Plinker]

Going to through an increased volume valve that I have into my Crosman 2289g and play with the springs a little today.    My goal is to be able to get two shots of decent power (greater than 10FPE) and still have a little air in the valve, so this is an experiment in ACP.

I will also finaly get arond to trying the poly tube transfer port (now it has a bored out stock transfer port with a top side O-Ring).

We will see the results.

Are you figuring maybe 30 to 35 pumps?
How long is your barrel?
What weight hammer spring?

I was able to successfully bore out my stock transfer port to .160 without destroying it this way:

• Found drill same size as stock port ID and chucked it in my drill press.
• Put the transfer port on the drill bit with the drill press quill lowered a few inches and carefully clamped the port in my drill press vice
• After running the bit up and down through the port to make sure the two were centered together, I removed the bit and installed the #21 bit
• Drill press on the lowest speed and fed it slow with some oil on the port

[rsterne]

If you want "a little air left in the valve" after the second shot you will have to have a pressure indicator to know when the gun is up to pressure.... If you can accept a dump shot for the second shot, and are therefore always starting from zero, you can simply count pumps and balance the two shots with the hammer spring....

Bob

[DavidS]

If you want "a little air left in the valve" after the second shot you will have to have a pressure indicator to know when the gun is up to pressure.... If you can accept a dump shot for the second shot, and are therefore always starting from zero, you can simply count pumps and balance the two shots with the hammer spring....

Bob

Close to what i did today for testing.   I did manage to get two consistant shots with a little air left though for now I am just dumping the Air left after the second shot to verify that there was air left.  See my next post.

[rsterne]

If you are getting a little air left, you need to either pump less (less velocity) or increase the hammer spring preload (more velocity).... You should be able to find a balance with two equal shots and no air left.... In fact, you should be able to find several such settings at different velocities and pump numbers....

Bob

[DavidS]

Good results today:

Got it to dump two consistant shots with air left in the valve three times today.   As I have not yet set up a pressure indicator I am just dumping the air left after the second shot to verify that there is some left, and to allow me to count pumps to get back up to pressure.

Charged with 28 pumps I get two shots, and three sets of the two shots are:
set  :  Shot 1  : Shot 2
1     : 583FPS:  592FPS
2     : 585FPS:  591FPS
3     : 580FPS:  594FPS

I think that is acceptable for sub 80 yards, would want it a bit tighter numbers for longer ranges.   The third burst of air used to empty the valve was done with out a pellet in each case (just at some fusy material that I have so I can see the burst of air).

Now I will have to make a pressure indicater and see if I can get the numbers even closer together.

[DavidS]

If you are getting a little air left, you need to either pump less (less velocity) or increase the hammer spring preload (more velocity).... You should be able to find a balance with two equal shots and no air left.... In fact, you should be able to find several such settings at different velocities and pump numbers....

Bob

I am intentionaly attempting to have a bit of air left as that should be more effecient than dumping out the second shot.

If I am mistaken pleas give some info to help.  I am always willing to learn.   And I will be adding a pressure indicator.

[rsterne]

Leaving some air in the gun is, indeed, more efficient.... but you will NEED a pressure indicator because the amount of air left will vary slightly, and sometimes you will need an extra pump (or one pump less) to get to the critical pressure required to make both shots the same velocity.... A slight variation in starting pressure (part of a pump) can make them unequal.... That is why I tuned my gun to dump the second shot.... Less efficient, but consistent....

Bob

[DavidS]

Leaving some air in the gun is, indeed, more efficient.... but you will NEED a pressure indicator because the amount of air left will vary slightly, and sometimes you will need an extra pump (or one pump less) to get to the critical pressure required to make both shots the same velocity.... A slight variation in starting pressure (part of a pump) can make them unequal.... That is why I tuned my gun to dump the second shot.... Less efficient, but consistent....

Bob

I can understand that.  I am primarily going for effeciency, so long as the consistency is acceptable (a half pump is not likely to be a huge veriation for two shots), I can deal with a slight difference.

So my next step with this gun is to make a pressure indicator, so I do not have to waste the left over air.

As stated above I will be making a simple pressure indicator that uses a spring loaded screw that will pop out of the stock on the cam over when the pressure reaches a certain level.   The style that some have done in ACP Benjiman 392's.

And thank you very much for your input.

[DavidS]

Well I did not have time to do any thing with my test 2289g, as I spent all day trying to get the breach screw out of my other 2289g, and doing some modifications to my Daisy 22X.

AirGunning can be exausting sometimes, I almost ran out of time to do my household chores.  I like AirGunning to much some times (I know there is no such thing as to much AirGunning) .

Though I do intend to make a pump arm pop out pressure indicator tomorrow and see just how much it takes to pump back to full pressure after just one shot, then after two shots .

[DavidS]

I did manage to get a pop out on the pump arm of the test 2289.   It takes 4 pumps to get back to full pressure after one shot, and 9 after two shots.  Not bad in my opinion.

I will make it a bit better now that I have an idea where it sits, I have already reduced effective head space to as close to zero as I can on this 2289 (while it was still full dump), though maybe increasing the valve volume would help.

[rsterne]

Let me understand this.... Your first shot is 585 fps and you can do that again with just 4 pumps on a 2289 pump, ie an input of only 4 x 18 = 72 cc = 4.4 CI of air?.... With a 14.3 gr pellet, that is 10.9 FPE from 4.4 CI = 2.5 FPE/CI.... When can we expect the DavidS Airgun Company to open?.... I'd very much like to purchase your first duplication of this wonder gun....

Bob

[DavidS]

Let me understand this.... Your first shot is 585 fps and you can do that again with just 4 pumps on a 2289 pump, ie an input of only 4 x 18 = 72 cc = 4.4 CI of air?.... With a 14.3 gr pellet, that is 10.9 FPE from 4.4 CI = 2.5 FPE/CI.... When can we expect the DavidS Airgun Company to open?.... I'd very much like to purchase your first duplication of this wonder gun....

Bob

After what we descused in the other thread I am rechecking all of my numbers, as I have obviously made some significant errors.   I will be updating much of the info over the next couple of days.   Sorry to all, for my errors.

[DavidS]

Until sucgh time as I find places localy to use 3 diferent brands of chrony to test and verify, I am labeling this experiment as a fail.

Part of any good experiment is being able to reliably measure the results.  It would seem that at this time I can not do such, as both my method of measuring the MV as well as a freinds chrony are giving erronious results.

I am sorry for the lack of any results.

[DavidS]

Let me understand this.... Your first shot is 585 fps and you can do that again with just 4 pumps on a 2289 pump, ie an input of only 4 x 18 = 72 cc = 4.4 CI of air?.... With a 14.3 gr pellet, that is 10.9 FPE from 4.4 CI = 2.5 FPE/CI.... When can we expect the DavidS Airgun Company to open?.... I'd very much like to purchase your first duplication of this wonder gun....

Bob

Thank you.

You have pointed out that at this time both my arangement and my freinds chrony are inaccurate.   As such I will be searching for the availability of other chronies to use to get accurate results.

I thank you much, I would not have relised the error if you had not done the calculations to show that the level of effeciency required to get the numbers that I was getting is not reasonable.

I am in your intelectual debt for your aid in this matter.