I have tank envy as well..... Beautiful.
Drilling and taping the cap of a sprinkler valve compromises the structural integrity of the valve. I caution other builders Not to make this common modification.
First, the electric solenoid works just as well. So why all the work and expense?
Second, you can buy a Orbit sprinkler valve that has a manual valve already on it. So, again, why all the work and expense?
That little lever next to the solenoid is the manual trigger. Flips 90 degrees. Used one in a RPG for several years.
The answer is: There is a belief that using a shop air trigger will open the valve faster than the electronic or manual valve mechanisms of the manufacturer. Thus producing more velocity with the same set up.
I have done both and short of a scientific study, can't tell any functional difference in the performance of the cannon. Same set up produced the same performance.
Now if you just have to do this, use a RAINBIRD VALVE. Cost the same.
It just so happens the solenoid thread diameter and pitch is the SAME as a pipe thread. But it is NOT NPT (pipe) thread so you have to epoxy or JB Weld Epoxy a reducer fitting into the threads. Because the epoxy blocks the port into the cap, you have to drill it out the same diameter as the original port.
Then you have to block the vent port that the solenoid works on. A simple wood screw will block it. Might want to do that before you do the epoxy fitting.
Then use standard plumbing fittings to your manual shop air picture.
Lets be SAFE out there. No need to risk injury to yourself or others when there is a safer way with minimal additional expense.
I see a LOT of cannon rules these day that prohibit any modification of the valve or pressure chamber that involves drilling, tapping, gluing in any way. There is a reason for that.
Still in a tank, the most likely victim is the occupants of the tank. Not likely to sue themselves or the field. Never seen a tanks cannon inspected for safe construction. Just chronoed.
Questions? I have pics and happy to walk you though this. Just e mail me: