Oh no! Today my at44 broke.

[remtom1200]

Sad day today as my at44 suffered an odd mechanical failure. Just started a string after opening the transfer port and barrel so it wasn't restricted, and the third shot the hammer didn't open the valve. Man what a disappointment as my first shot with jsb monsters crossed the chrono at 898, and the second was 915fps. After removing the stock, slowly turning the air cylinder out I could not believe what I was looking at. The valve snapped off at the middle of all the 6/32 set screws used to plug all the holes. I am not sure if it was caused by stress of tapping the holes for the set screws or the hammer strike. What I do know is I emptied all the set screws out of to the floor and very carefully put the air cylinder back in to protect the exposed valve stem holding about 180 bar. I need a new valve now, and a different way to plug those holes.

[rsterne]

Never heard of that before, congrats on finding a new problem !

I assume you depressurized the tube, and removed the stem before tapping the holes to plug them, and then cleaned out any debris and burrs and made sure the setscrews weren't too long before reassembly?....

Bob

[remtom1200]

I had the set screw mod done for some time now. Something I did do differently was the 4 holes at 20° at the back of the valve body as you done to your at project. Never would it be due to improved airflow?

[rsterne]

My guess is that the valve stem jammed somehow....

Bob

[remtom1200]

When there is a failure there is an opportunity to improve ;-). I will do a tear down and take a closer look.

[remtom1200]

20140126_105752.jpgLooks ugly

[rsterne]

I misunderstood how your valve failed, I thought the STEM broke, not the valve body.... That failed due to air pressure, I'm pretty sure....

Are you sure you used 6-32 and not 8-32 setscrews?.... there sure isn't much room left between the holes.... Or, if you didn't use a bottoming tap, perhaps there was too much taper to the thread and when you screwed in the setscrews you fractured it.... When I did my .25 cal I used 6-32 but started with a tapered tap and finished with a bottoming tap to make sure the screws went in without having to force them....

Another possibility was that if the screws were too long, when you installed them they intersected each other and that stress fractured the valve....

Bob

[remtom1200]

I'm pretty sure I used just a tapered tap. Probably a combination of weakness and increased air pressure. Now to make a different setup using the same valve. I have a few ideas.

[remtom1200]

20140129_110831.jpg20140129_113005.jpg20140129_112440.jpg20140129_115339.jpg20140129_124651.jpg20140129_132313.jpg20140129_155226.jpg

Now installed a new band to replace the section once filled with set screws. I will next disassemble the at44 and screw the valve into its place and mark the valve for a new exhaust port.

[rsterne]

I'm not sure I understand how the new rear half of the valve is fastened to the front half.... What resists the force trying to part the two pieces?....

Bob