If a ship has only dual stern guns, does it need a accumulator tank for the dual aft guns? or can one popit value be used with one 1/8 line going to each cannon from it?
You don't really need an accumulator for each, they'll do fine without them. You shouldn't try using a single MAV-2 for both though. A mav-3 (pushed by the servo) is usually used to actuate a mav-2 for each gun via an MPA. Trying to firing both from one Mav-2 will usually result in only one firing or both firing but one will fire rather wimpily. Below is a crappy diagram I drew up last year while figuring out duals. You can ignore the accumulator tank if you want and just assume you;ll be splitting your co2 supply line to feed the 2 mav-2s.
Airtronics up in Bellevue can sell em to you, Something like 5-6$ each. The MPA-3 screws on over the push stem of the MAV-2, the air pressure from the line from the mav-3 your servo pushes causes the MPA3 to push the MAV-2 valve to the open position Heres the part on Clippard's page: http://www.clippard.com/store/display_details.asp?sku=MPA-3
When I was going to put dual sterns on the Bis I was going to put one popit valve for two guns. the valve is still set up that way but with out the second gun. Next time I see you, you can take a look.
Alex, did you test two cannons with one poppet? From my understanding, when you pull the trigger, the MAV-2 starts charging both cannons fairly equally. Unless the two cannons are identically tweaked, however, one reaches firing pressure first and fires, and the MAV doesn't have enough airflow to maintain pressure to the other cannon so it either fires late or never. I have seen photos of a Queen's Own 1:72 scale warship with two Fast Gun-style cannons fired from a single high-flow MJV-2 valve, though. That sucker really moves air.
I take it the Poppet Actuator = MPA-3 stores a small charge before it activates the poppiet it is attached to and then sends the CO2 to the cannon. so, when you active the single poppit, that distributes the CO2 to both Poppit actuators, they both get a charge then, then active the poppit they are attached to and the CO2 flows to both cannons and they fire. so this small charge in each poppit actuator is enough that both cannons fire with about the same psi. does this sound close.
The mav-3 is a three way valve. It either pumps gas toward the mpa-3 or it releives the pressure so the gun won't remain in a firing state. The mpa-3 is basically a gas powered version of a servo, it pushes the button to fire the gun. If you look at Nick's drawing. You will notice all three valves are suplied with co2 and no energy/gas is stored down steam of the mav3.
MPA-3 is basically a piston that screws on to the top of a mav-2. The mav-2 is a on-off valve. When you drive a piston, there is no way for the pressure to drop off, so the pistons stay down and the mav-2's don't release. The mav-3 vents gas up around the stem when the valve is released, this lets the mpa-3's return to normal. This requires the watertight box to be vented. There is a variation on the mav-3 that dumps out a second hole and not out of the valve stem. The Mutsu runs this configuration.
You can substitute smav-3 for the mav-3 and achieve a faster firing rate. (smav-3 is a subminiature version that requires less travel to open fully, about 1/16"). The downsides of the smav-3 compared to a mav-3 are: more expensive, tiny barbs that require a clamping sleeve to hold the hose on, and only rated for 100 psi. I operated them successfully for 5 years on 150 psi though. I was able to fire at rates up to 6 shots a second with the smav-3 and a regular servo. Another substitution possible in this system is replacing the mav-2 and the mpa-3 with a single pav-2. The pav-2 is a newer valve that integrates both. Ron Hunt
Wow, those PAV-2's look neat. I just wish they were cheaper than the MAV-2 and MPA-3 combo they were replacing.
They are a little smaller but definately not as cheap. one of the guys here in North Carolina uses delta boards connected to a small clippard electronic 3 way valve at reduced pressure, which activate the pav-2 valves. A little complicated to do it that way, but he likes the small electronic valve.
