Dual sterns on an Indianapolis.. I should use expansion tubes I would guess.. 1" or 2" each? Or just one 2"?
For twin sterns take a 1/2" copper pipe as long as the solenoid, about 2.5"-3". Put a check valve between the tank and the main supply.
I doubt that you need accumulator tanks. I equipped my Spanish heavy cruiser SNS Canarias with dual stern guns and they fired hard and fast without them, using only 1/16" tubing. The CO2 source (Palmer RTB regulator and 38oz CO2 capsule) was right under the guns and the CO2 lines were short. If you're concerned about volume of gas getting to the cannons you can also run 1/8" line. Bob
Just making sure I am reading this right. I can run one solenoid for dual sterns? The reason I ask I was thinking two.:blush: If one is the case then cost goes down which is a Good Thing (tm).
Use two solenoids for two guns. Useing one may kind of work, but will not work well. Each would have a tank and a check valve. Check out the Insides of Warships at portpolarbear.com to see this set up. I've done the twin guns without tanks on the solenoids and it has worked. It was just harder to get the guns tweaked just right.
For the dual sterns I have on the Salem, I use poppets, run off separate channels. Back fires left gun, right fires the right gun, diagonal back and right fires both. I don't use an expansion tank. I get the option for single or dual fire as I wish.
Despite popular opinion you need 1 cubic inch of chamber per gun. I would defiantly use expansion chambers if you are firing duels unless you like freezing up your lines. When rapid firing you will defiantly freeze up. Using tanks in your boat takes only a little more effort and planning and adds a peace of mind. It should be a rule of thumb.
I've used dual stern guns in SNS Canarias, HMS Courageous, HMS Hood and HMS Warspite but never had freezing or icing up, with or without expansion tanks. Maybe that happens with circuit board firing and/or solenoids, which fire faster than servo operated MAV valves. I couldn't perceive a difference in rate of fire between dual guns without (Canarias and Courageous) or with (Warspite and Hood) expansion/accumulator tanks. I used one Clippard 2 cubic inch tank per gun. I did get a noticably higher rate of fire toggling back and forth between independently firing dual guns without tanks. No matter how big a tank you use, the main factor that determines gas flow to the gun is the diameter of the hose between the tank and BB cannon. Theoretically, adding a tank between CO2 source and gun and using the same diameter lines won't have much if any effect on firing. However, a 1/8" vs 1/16" I.D. hose has 4 times the cross-sectional area and will deliver gas far more rapidly. Again, to take advantage of the increased volume available with a bigger hose the CO2 fitting on the gun must be larger too. I have seen BB cannons getting their CO2 via 1/8" I.D. hose and a 1/8" fitting fire faster than cannons with the usual 1/16" I.D. hose and fittings, without an expansion tank. Bob
Very good point Bob. Until you spoke up, I hadn't thought about the fact that the input to my expansion tank is 1/8th hose. Another approach I tried is to use 1/2" copper pipe for the expansion tank. It is about 10 inches long which allows it to also act as a section of fixed pipe in the bottom of the hull as well as acting as the tank. One of the most amusing shapes I saw is actually an M shape. This provides space between the arms for the dual rudder assemblies, is made of a lot of copper so puts some significant weight in the stern to get the guns down low and puts three output barbettes right next to the solonoids. What strikes me about this design and a couple of others is that they are one component of an overall design that was thought out as a total system by captains building a third or later ship. Another important lesson is that there are very few ships that have not been totally refitted internally. I own a couple of them and one is due, one doesn't have room and the other is probably permanatly beached. I don't know any captain who didn't totally redo the insides of their first ship. So get it built so you can get started on rebuilding sooner!
Interesting points. My own expereince depends on a combination of factors such as the length of hose being used and the size. I have 2 ships with different setups. Bismarck uses no accumulators and no solenoids just strictly poppet valves. The dual sterns fire hard and fast as well as the other cannons. I think the Volume of the tank plays a factor here where I use a singel 20 oz tank. Yamato uses a 20 oz tank and 3 accumulators. A 3 inch copper pipe stock BC, for the stern triples, and a pair of 2 inch pipe stock BC for the dual sidemounts. I run both large and small hose. I try to keep the hoses as short as possible. Roma uses a 9 oz tank and no accumulators. Rate of fire and hittingn power is the same as with Bismarck and Yamato. I do non perm thread lock the barrels after I have tweaked to the correct setting. Generally the model will fire hard and reliable for a long time till the O-ring is worn so that cannon does not fire as hard. I keep the lines free from binding or being squeezed with clamps. I think there are several factors to consider what will work for a ship and I think in most cases there are many setups that work well providing that the chosen setup is setup correctly. The whole system right from the Gas supply right to the breech of the barrel and everything in between. Time to get back to VDT
Hey Bob , you make some good points but the fact is ( like you said) if you want fast firing guns you need a dump tank. As i understand it the purpose of the expansion tanks is that the gun draws O2 from the tank when fired. As the gun cycle the dump tank refills with O2 for the next shot. Thus keeping the O2 pressure somewhat high as we all know cold bottles make co2 pressure drop. This is not a problem for Treaty but for IRC or MWC it can pose problems. My Yam has frozen its lines a few times from rapid firing.
Were you running just 1 bottle and reg, or 2 in the Yammer? My PE was freezing up here in Floridausing just 1, in October and Nov, why I decided to go with 2 bottles and regs in my ID.
I run 2 bottles in all my boats. My gun are pretty fast and that is the point. By drawing your O2 from a dump tank your bottle has time to recover between shots. If you like shooting and keeping your psi high then dump tanks are a must.
