2289 Valve

The mods herein may cause over 500 fps performance.

After I got my shiny new flat top piston and valve from Eric and installed it, I thought; well that works. What else?
Being leery of chopping up the new valve, it ocurred to me that I might have an option. I had this lying around cluttering the place up.
Attachment 386

Why not take off the point, I thought.
Attachment 387
Actually, my first go, I walked past the bandsaw and got out a hacksaw. It worked OK, but wasn't quite straight so I filed it to make it worse.:crushed:
The bandsaw is certainly better.
Attachment 388

Then, of course, more volume might be good.
Attachment 389Attachment 390

The results look pretty good.
Attachment 391Attachment 392Attachment 393
This worked well in the gun and improved performance. I thought that it would take more pumps for the same output, but would have a higher maximum. As it turned out the number of pumps weren't that much higher for a given velocity, but at the top end I got a better maximum velocity.

Well, that just begs the question, what will more volume do?
A friend with a lathe faced the flat top for me and while he was at it he bored out the ID. As it turns out, he got too close to the shoulder at the end of the male thread and...
Attachment 394

Fortunately, I still have my commercial flat top valve to use. I also have a couple of other stock valves, as I have been doing some mods for relatives (Eric could tell you I have enough spare barrels to make a wind chime).
If anyone wonders, the extra volume from boring didn't seem to make a huge difference.

Everything looked good 'till that last pic - bummer! Probably won't make you feel any better, but I have a small (but growing) collection of "NFG" parts, too!

With the extra volume from boring, you more than likely will need a stronger hammer spring (or a stock spring with RVA turned in a bit) to take advantage of the larger volume of air you are trying to dump.

Good luck! Keep us posted,
Todd

Although the extra volume of air would, in theory, take longer to dump.... at the same number of pumps the pressure inside the valve will be less.... The critical factor in how long/far the valve opens is the air pressure operating against it.... so in fact the valve will have an easier job dumping the same number of pumps with a valve of larger volume.... What you will find, in fact, is that at low pump numbers the gun will actually lose velocity because pressure is more important than volume.... As you pump more and it gets harder and harder to pack the air into the valve, then the larger volume will pay benefits....

I just rebuilt a Crosman 1400 (large swept volume on the pump, about twice that of a 2289).... There was a spacer inside the valve taking up about half the volume.... Removing that spacer lost velocity at 4 pumps or less, broke even at 5 pumps, and gained velocity at 6 pumps or more.... On my "Uber-Pumper" I found that increasing the valve volume only paid benefits at over 10 pumps.... I achieved 900 fps with 14.3 gr. pellets eventually.... but quickly grew tired of pumping it....

Bob

Quote:

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Originally Posted by rsterne

.... but quickly grew tired of pumping it....
Bob

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I didn't think I was ever going to see an admission like that from you. Things always change-up, though :cool-new:

I've melted a delrin piston, or six, trying to force the 13-XX beyond what it's designed for. It can be done. It's my opinion that the current crop of aluminum 13-XX valves are poor candidates for volume expansion via the boring and cutting method. A thread-in spacer between the valve halves would be a stronger solution- at the cost of swept volume. A longer pump tube pretty well becomes a prerequisite...

Regards,

Doc Sharptail

You mean like this?....

http://i378.photobucket.com/albums/o.../Extension.jpg

That was the valve from my .22 Uber-Pumper which used a 1400 pump tube and linkage.... I reached 902 fps with 14.3 gr. JSB Express pellets (26 FPE) at 22 pumps.... but only after I replaced the F-T-P piston with aluminum.... The Delrin one melted severly.... The gun was starting to retain air at 20 pumps, and at the time I was running a 2200 hammer spring.... Had I had a Disco spring, even more performance might have been possible.... but MAN that thing was a bear to pump at 20+ pumps....

Bob

That's exactly it. Nice work, as usual....

Regards,

Doc Sharptail

I cheated.... I made the center section from the rear half of a valve.... I didn't want to tackle the inside threads on my lathe at the time (a few years ago).... I did the outside threads with a single point tool and then cleaned them up with a die....

Bob

That sounds like a good reason for me to hang onto that spare rear section of a valve that I seem to have.