I managed to get the size of the entire magazine to 1-5/16" or 1-3/8" basically when adding the screw heads. Need to work on a servo mount, the fill tube, and barrel braces next. Here are some pics. Quite exited with the result...nothing that a drill press and some circular cutting blades without the drill bit part cannot cut out easily enough. A laser would be handy. I'll give this all a go here once I pester the wife about my new drill-press. If it works out, I'll post 8x11 templates for anyone that wants to try this out as well, and hopefully with some pictures to go along with it as well. For now, 3D artwork will have to do... H-39 Cannons Anton and Bruno: H-39 Cannon Wafers: H-39 Cannon stacked together: The magazine will hold near 240+ BB's. H-39 Cannon: Bottom View - note the slots in teh manifold for the air to travel from the MAR-6 to the two barrels. Cheers, Thomas
I think I've mentioned this before but the MJV-2 valve does not have enough airflow for two 1/4" barrels. Not even close. Clippard's Jumbo Exhaust Valves have enough airflow for a pair of .177" bbs, but I don't think it's enough for the much more demanding 1/4" rounds. That's why cannon bases are so important: they include both accumulator and an enormous high-flow valve to fire the cannon. The action and flow rate of that gigantic valve both play significant roles in the performance of the cannon. A few other thoughts. Since you're designing this in CAD, have you given any thought to rotation mechanism? And just as important, synchronization between two turrets? Those features are just as important as the cannons themselves. A well-designed rotation mechanism is responsive, robust, and easily disassembled for after-battle and (if necessary) after-sink maintenance. I know there's not as much Big Gun information on this site as there is Fast Gun info, but take a look around and see how others have set up their rotation systems and start thinking about yours.
I'm looking at using the MJV-3 that has 25 scfm, and using BB's. Does someone have the airflow in scfm for the home-made ball valve? Well, if this setup works (using a MAR-6 roating manifold for this here design) and the components work, then I can give some throught about making a mounting base for all this, and then figure out how to drive the turrets. My first goal was to get away from lathing...I dont do that, and dont want to spend time to learn and money on a lathe. I know that everyone thinks they can design a better mousetrap, but hey, its all part of the fun. Cheers, Thomas PS: Someone ought to send their cannon to Clippart and tell them to make something similar but better...and more robust. Why has no-one asked for a ball valve to be manufactured? Clippard sais right in their catalog that they want peoples ideas and designs...get them to make something that will work and be of benefit to many future battlers..
If they are willing to produce them cheaper then it is now to get them then I agree some one with working cannons should send one in to see what they can do. As for shooting BBs what format are you building to? because if you building to big gun rules which I assume you are, then you are going to want to arm the ship with 1/4" ball bearing cannons other wise H-39 will be significantly under armed and if it ever came up against a properly armed big gun capital ship it would be dead for sure. just a thought
Good thoughts and thanks! I like the more historical and realistic flavor of Treaty, although I'm somewhat confused by their point values. I get the idea, but... From what I see, is that Big Gun uses way too many pumps, so obviously the holes and the damage they do it out of sync or something. Not quite happy with the size of the barrels either - they look cartoonish to me, sort of like Games Workshop or WoW type equipment. But I do like their armor, if nothing else - for the regidity and less chance of glanzing hits to penetrate them and all that. Read many-many posts and had lots of responses that mention that it really does not seem to matter what wall thickness balsa one uses - all brearings rip through the balsa just fine. So I'm thinking, use 90% treaty rules and some of the construction rules from Big Gun warships, like the WWCC rules, which I like, and the Washington Treaty Rules, which I like as well for their emphasis on size of rudders, props, structure and having all the parts and pieces on a ship. Since I'm a solo - it does not really matter. But I'm keeping an open mind. If I choose to, I can always install a larger barreled cannon, and I'm trying to keep that in mind - and the props and rudders are easily exchanged as well. As for the hull...I'll go with 1/8" balsa. I had no issues at all skinning the Nelson with it...soak them and heat them in the microwave (steaming them) is a good way of bending balsa, or a tea kettle works good too for long strips . Anyway - great comments. Please keep them comming. Soaking up knowledge as fast as I can find it. Cheers, Thomas
Another mile-stone - bent my first 1/4" OD steel barrel. Used the K&S Tube benders - worked like a charm. I had bought the low point metal and even read about people using sand, salt and what not - tube benders worked amzingly well. BB's roll right through and out with amazing ease...now I'll bend the other 7, and put them to the side until I get the guns built. Maybee look into a metal fab show to turn some of the steel barrels down a bit so they taper at the end. Or I stick one on a drill, find a flat stone and see what happens...lol. So exited...
I asked about ball valve flow rate, and while I didn't get any actual figures, the answer seems to be "much more than 25 scfm" http://groups.yahoo.com/group/BigGunsModelWarship/message/24493 I can't see the MAR-6 in Clippard's catalog -- did you mean the MRM-6? If so, that's rated at 5.9 scfn at 50psi, so I think it will be far too restrictive, even at 100-150psi. DISCLAIMER: I have never built, owned or used any CO2 cannon! Tom
Very cool - thanks for checking. Since I'm using the MRM-6 (yea, misstyped that, thanks) is basically the "manifold" and really only an extension by itself for each tube, I was thinking that should be plenty - and each port of the 6 ports is rated for 5.9 scfm at 50 psi. If you start closing some of them, one should see higher airflows - the pressure loss through the manifold is also insignificant. Be interesting to see anyway. But given from the responses, dont seem that anyone has tried using one that I found in any forums. It struck me as being very usefull, as it combines a manifold with the rotational device (bearing) into one component, thus saving space. I think you'd want the shortest distance from the accumulator to the bearing with little to no expansion for the pressure to disipate before reaching the BB's. And I'm also thinking of using Rare Earth magnets to hold them in place. You can get Rare Earth Magnets that are washer shaped at the size where a BB would fit snugly into it like a cradle. The force of the magnet would have to be matched by the air pressure plus the weight of the BB for the air to disloge it, allowing more pressure buildup behind it, meaning, it will build up a bit more pressure than just the normal static resistance that a BB would present. Thomas
I used to talk to those folks a long time ago, when I built my Nelson/Rodney. Very helpful and generous individuals there as I find here. For some odd reason, my old password just jumped back into my mind. Thomas
So I did some more thinking on the cost and flow rates we discussed above. I went back to dig through my pile of previous ideas and looked at my clippard catalog. And lo-and-behold, I finally found a part that one can screw those pesky 15/32-32 threads onto (I have the die threader thing for that - but figured I'd look anyway). If one screws together a 15027 Bulkhead Fitting and a 15050 Female 1/8" NPT, then that can be screwed onto a 1/2" Copper or Brass elbow with a drain port. The drain port is a 1/8" NPT male, so that marries pretty well into the clippard Female 1/8" NPT. And the bonus is, that the edge of the Female Fitting will serve as the seat for a spring. Now all I need to figure out is what that hole size is in that Female 10/32'nd thread part. That will determine the push rod. The rest is easy. Solder some copper together for the accumulator, add more copper and a bearing...done. The whole assembly should only require a bit of soldering and pipe cutting. No lathing or anything required. And its all copper...I was thinking of a T arrangement for the accumulator also, to save space. Dont have the clippard parts yet, but I priced them out...dirt cheap in packs of 5 for those 2 pieces. Then add the popet valve and the fill tapping, thats it. A stick of copper, a few elbows at $2-3 each, some pipe caps, a 1/2" x Something reducer (1/2" x 1" I'm thinking) for the Buna-N-Ball, polish it till it gleams with a dremmel, and maybee even have a screwed on endcap, so one can get at the Buna Ball. This all might be heavy, but heck...its the H-39 after all. And attach all that to the H-39 Wafer Magazine. Just replace the hexagon wafer with something that fits the bearing I have here: Thoughts? Anyone done this before? Thomas
I use the 15027 bulkhead adapter to make my cannon valves, it saves time and costs a lot less than a tap and die for the 15/32 thread. I machine down one end to 3/8" and thread it 3/8-24 to fit into the end of the valve, so not the lathe free part you are looking for. I checked the hole in the 15050 part, it is 0.1065". That's better than the brass male connector which is only 0.0890". So you might be able to get a 3/32" rod through, although I would feel more comfortable using 1/8" myself.
Nice - thanks a ton for sharing and showing the annotated image! A stainless steel rod at 3/32 might work, but I hear agree that 1/8" be nicer. Is there enough material in the 15050 to drill it out a bit to the 0.128 size? Maybe if one solders the 15027 and the 15050 together. Should work - worth playing with I think. There should be 3/32 threaded rod in the aircraft push-rod selection. I was thinking of using 2 small screws with a washer (for the spring) sandwiched between and keep adjusting it until I get the proper length, then solder them together and grind off the end for the popet valve. Thanks again for sharing - I'll put together a purchase order with clippard soon. Still walking through the diagrams and learning all I can about the pneumatic system overall (for big-gun application, although I'll probably stick with BB sized barrels..I like the look of the 1/4" barrels better). Thomas
There is plenty of material on the 1/8 NPT side, it's the male 10-32 side you have to worry about. The problem is the 10-32 thread, which has a minor diameter of 0.15". So if you drill it out for 1/8" rod with just a slightly free fit, say 0.13", then you would only have side walls of 1/100". To use a 1/8" rod you would need to drill and tap the bulkhead adapter for a bigger thread, say 1/16 NPT or 1/4-20. Then you need to find an adapter for that thread to your female 1/8" NPT. An alternative would be to use the 3/32 rod through the fitting, but then solder a 3/32 ID, 1/8" OD brass tube over the rod where there is more space. That should stiffen it up enough.
Good thinking - I was debating about dropping the female adaptor and drilling out and tapping the bulkhead fitting to 1/8" NPT...that should be easy enough to do. And then come back and drill out the other end for the base of the spring. That might work I'm thinking. The drain port of the 1/2" brass elbow is plenty large for the 1/8" rod - steel or brass rod? Here is a quick mock-up of what it might look like - there is a wooping 12" of 1" copper tubing there for the accumulator - way too much I'm sure, but I'll figure out what will be enough by asking the people who know about these things and go from there. I'll probably raise this on a platform or something. Gota think about various other components too. Thomas
That's going to be a long pushrod. You might need some guides for it. You also have a lot of dead space between the valve and the magazines - that's going to drop pressure quite a bit before it gets to the breech. I use brass for my pushrods. I'm not sure if stainless would be better, I can get the brass locally and it is easy to work with.
Be wary of tandem cannons (two magazines, one valve). They usually have one strong magazine that sucks all the air, and one weak magazine that gets none of it. They are also, as RCENGR pointed out, prone to rod droop because of how long your buna-ball rod has to be. If possible, you would be better off using two complete separate cannons instead of a single tandem. It will be more reliable. Your bronze fittings look very interesting. Lots of potential there. Can't wait to hear how they work out. Looks good so far, though.
Getting the flow even in a tandem cannon is fiddly but do-able you need to direct gasflow away from the closer cannon and to the far one. Setting the riser tube to the close cannon so it protrudes slightly into the gas flow robs it of efficiency and transfers that loss to the farthest cannon. How much is trial and error A guide tube for the pushrod will be necessary, but only needs to support the shaft, so it can be as simple as a brass tube. I use three long grubscrews to locate the ones I've made, they are about 1" back from the ball. By adjusting them, you can centre the ball exactly.
Thank you all for the great advice! I'm looking at using a single accumulator (3" long x 1" dia copper) for each gun after reading your comments. Footprint is still small enough and that will bypass all the aforementioned issues. I think I can also get by with just the Clippard Bulkhead if I drill and tap that 1/8" NPT and then sink in the hole for the spring according to the plans. Its a bit of back and forth - work on the ribs (notching them for stringers and then the armor belt) work on the cannon a bit, figure out the barbette and the gun turrets, start looking at servos to buy and where to mount stuff - sometimes it seems a bit overwhelming, thats for sure Thomas
