Monday, February 7, 2011

Crosman 22XX 88g AirSource Adapter--Part 2

Jumping right back in where I left off...

Spotted with a center drill.

Gradually drilled out the hole to 1/2".

Modified a 1/2" bit to drill flat-bottomed holes. Works incredibly well. I can literally shave brass foil from the bottom of the hole that's less than a hair in thickness. Deepened the hole to 0.493". If you're paying incredibly close attention, this isn't enough depth to get full thread engagement on an AirSource cartridge--it's just enough depth for the pin valve I made to refill my A/S cartridges.

With a small boring bar, I opened the hole diameter to 0.520"--roughly the nose diameter on an A/S cartridge.

I couldn't measure to the very bottom of the hole, so I used a telescopic bore gauge and referenced various depths. I had enough confidence that the bottom was at, or extremely close, to my number.

Need to cut the o-ring at the bottom of the hole for the A/S cartridge to seal on. Made a boring bar from a blank 1/4" lathe tool bit. Used the bench grinder and Dremel tool. Cut it so just as the side bottoms on the side of the hole, the tip has cut the o-ring seat to the correct depth.

Not shown: Bored the hole above the o-ring seat to 0.570--roughly 14.5mm--my tapping size.

Tapped the hole to the o-ring seat M16 x 1.5mm. Used a bottoming tap.



I need a pin to depress the A/S valve.

Spotted the bottom of the hole then drilled about 1.150" deep with a 1/8" bit. Depth not critical.

Used the 1/8" bit as I have some drill rod in that size for a pin. Not shown: Used a 1/4" endmill to make a counterbore as a gas flow passageway. You can see it three or four pics below.

Cut a piece off with some heavy side cutters then flattened one end. Started by holding it with the vise grips, but then I remembered that I have a really sweet set of pin vises.

The pin vise uses a collet to clamp the pin and gave me more dexterity.

Fit an o-ring and the pin, then test fit the A/S cartridge a few times. Tweaked the pin length until it opened the valve just as the cartridge was sealing against the o-ring. I think the pin ended up somewhere around 0.598" OAL.

Another view. You can see the 1/4" counterbore around the pin. It's just space for the CO2 gas to flow out from the A/S cartridge as its valve opens.

Did some more layout and found the centerline on the bottom of the adapter. Picked a spot.

Spotted then drilled with an 11/32" bit. Followed with yet another modified bit to drill flat bottomed holes. Drilled approx 0.260" deep.

Then tapped 3/8"-24. Why? Safety first.

This hole is for a paintball tank burst disk

The M16 A/S and 9/16 valve hole bottoms aren't even with each other . They're offset slightly. Scratched a rough angled line to connect them.

Before I make the connection, I used a homemade pointed indicator to find the center of the 9/16 hole.

Then drilled about 0.250" deep with a 5/32" bit.

Angled the piece and sighted my scratched line with a small machinst square. Then centered up on the 3/8"-24 tapped hole and connected to the opposite 9/16" valve hole with a 1/8" bit.

Test fit and checked for leaks. There's the burst disk on the bottom right of the adapter. A 3K is installed now--same as all PB tanks--though I also have a 1.8K on hand.

Just a quick ad hoc arrangement at the Crosman valve end for pressure testing.

To seal the gun end, I used the front half of the Crosman valve. Added a small bolt with an o-ring at the base of the head to make a hasty seal to prevent the CO2 from escaping at the outward facing end seal. A quick and dirty pin valve if you will.

A drop of Crosman Pellgun Oil at each connection showed only a tiny leak at the burst disk. A fraction of a turn tighter and it held fast.

So, that piece of Crosman valve will be discarded from the design. A threaded tube will replace it and screw into both the gun's main valve body and this adapter. The hard part now will be getting the thread depth and o-ring seats correct so the A/S cartridge sits directly underneath the gas tube. Still a few design decisions, but I'm leaning toward cutting down a 2240 gas tube rather than make the conncting tube 3 or 4 inches long.

More in a couple days.

1 comment:

jameslhardin said...

Dereck 38:

I happened to stumpble upon this site by accident, but am fortunate that I did. Airguns have been my hobby for quite some time, and I enjoy "tnkering" with the 2240. I was hoping someone would make a mod such as your 88 gram / 2240 conversion. However, may I respectfully and selfishly suggest (because I would like to buy one) that rather than cut a 2240 tube so and use the 2240's old, small and restrictive valve, that you incorporate the valve into the adapter, making it as large as possible and use whatever section of the 2240 as is necessary. Perhaps it can be attached via threads or set screws. I just thought that this would be an opportunity to make an Uber 2240 with a much larger valve and it would thus have the ability to shoot larger pellets or .177 and .22 caliber pellets faster.