@ beaver.... looks pretty good, I have 2 questions.... 1) It seems like there is at least 1 more plate needed? Carl will have more insight though. 2) What are you planning on using for a rotation bushing? Accuracy will be important there to: A) keep air from blowing past. B) if there is much slop the magazine will wobble excessively. You will just want to make sure you select a bushing before you cut the holes in your plate so you can make sure you can get a bushing to fit it - nothing worse than spending time doing an awesome job of cutting and then finding out that there isn't a bushing available in a size that will fit!
1) If the the plate you think is missing is the top of the magazine, not to worry, I've not forgotten about it. These are just the four main plates, anything else will be added later. 2) Bushings have been chosen. http://www.mcmaster.com/#standard-sleeve-bearings/=pcrap2 Probably the Alloy 932 will work for this. And do you think the 1/2" long one will be long enough? Beaver
Doh! No, It wasn't the top, it's the one with the hole in the center for the bushing --- i saw it but forgot about it when looking at the other sheet!! Looks good then!!!
Yeah, it's there. LOL This is more of a question for Kotori, but anybody else that has an opinion can answer too. Would I want to use a sheet of ABS that's 1/4" thick, or something slightly thicker, say 5/16"? Beaver
So I was thinking about big gun cannons today, and thought of something that might be useful to be changed. The generally accepted way to fire a big gun cannon is to have a valve formed by a buna ball, which is opened by co2 pushing a flat cylinder on the end of an 1/8" rod that runs to the buna ball.( If you don't understand what I'm saying there, you'll get it later. ) Well, I thought that instead of the co2 pushing open the valve, I figured a servo could do the work efficiently, and precisely. Here is what I was thinking of: The servo pushes open the valve releasing the co2 which fires the gun. Any suggestions??? Beaver
There really aren't any electric devices that have the power In a small enough size to open the valve. It is seated with 25-30 lbs of force, so it would take 40 or so pounds of force to open it. The servo would be too slow also, you want the ball valve to snap open as fast as possible to get the hardest shot possible.?
Ohh, forgot about the co2 pressure pushing on the buna ball. Guess that idea went down the drain.( like most of mine) Still working on the cannon. I'm thinking that 5/16" would be better that 1/4" for the gun plates. Any suggestions there as well??? Beaver
I'm Not sure what is available in thicknesses, but if you are going with 1/4" ammo, I'm pretty sure the plates MUST be greater than 1/4" or the balls won't be able to roll around and feed properly. Even in the plates that don't provide ball separation (insert joke here) you want them thicker than 1/4" to maintain a cross section of airflow greater than the ammo size, unless the flow area is wider than 1/4".
That's what I was thinking. Looking though Mcmaster's different choices of ABS, they only have 1/4 and 1/16" no 5/16". I figured I could just cut out a 1/4" and 1/16" piece of ABS for every plate. Maybe even weld the two pieces together. Sound like I'm talking sense? Beaver
Maybe Check somewhere like online plastics... If you can find 7mm or 9/32 it would be perfect, .275 and .281" thick respectively..... might be a pipe dream of mine though!!
Ahoy Beaver, I just took a look through your drawings and you've definitely got the right idea. In fact, overall, they look great. Your CAD software is my favorite, as well. I do my best design work with fresh paper, a sharp pencil, and a good ruler. Still, there is room for improvement in your design. Here are some tips when you go do design v2.0: 1) more layers. You've got the major sections correct, but you need to plan out separation plates between them, to ensure that rounds in the ammo ramp level do not drop into the air manifold level. If you want to laser-cut this from acrylic (the most common laser-cutting material), you'll probably want to work with a bunch of 1/16" plates, rather than a few 1/4" plates. This allows you to do nifty things like sloping the ramps (think small, long stairs), and size the magazine for different rounds. Also remember that most so-called 1/4" acrylic is actually 6mm nominal, which is great for 7/32" ammo but doesn't fit 1/4" rounds. Same applies to the thinner layers: most 1/16" acrylic is actually 1.5mm. 2) more levels. You've got most of the major sections, but you're still missing a few. Specifically, the magazine cover and the rotation bearing level. The magazine cover can be a simple thing, with holes for the barrels and a loading port. Or it can be a little more advanced, with designs to mount a depression servo as well. The rotation bearing level is much more complicated because there are a lot more considerations. I can't type them all here so I'll try to address them further down. 3) dimensions! I can guess at some of the dimensions in your drawings, but a lot of very important areas have very vague dimensions. Many of the hole sizes need to be precise. Wall thicknesses should be labeled, not guessed at. And barrel spacing, that vital dimension which decides whether you'll leave three clean holes or a single massive gash, needs to be discussed. I know I didn't set the best example with the plans for my own laser-cut magazines, but those were the exact files I sent to the laser cutter, and all of the dimensions were integrated into the drawing. 4) angled magazine ramps. Angling the magazine ramps is a risky proposition, because you want to ensure that each ramp has equal access to the ammunition. angling the ramps inward like that probably won't help, and it makes the drawings much more difficult to produce. Consider going with straight magazine ramps, at least until you are approaching a final design. 5) Assembly! How do you plan to hold this together? Acrylic glue is a bad idea because it's a permanent plastic weld. I would recommend a few screws around the perimeter to hold it together. Remember when drawing these holes that the laser-cutter is not truly a precision instrument for cutting tiny holes for #2-56 or #4-40 screws. For best results, what I did was use the laser cutter to cut a smaller locator hole in each position. Once I received the parts, I chased the laser-cut locator holes with the correct sized drill in a drill press, and threaded the bottom layer. If you plan to use the thinner 1/16" layers for your cannon, you can cut small hexagons in the bottom layers to fit steel nuts with the correct threads, for greater strength. 6) Barrel spacing. Right now, it looks like your barrels have a large gap between them. Try to cut it down to a maximum of 0.7", minimum 0.5" center-to-center distance. The tighter your spacing, the more likely you are to chunk. However, tighter spacings also mean more difficult assembly, disassembly, and maintenance. A good compromise is about 0.650" center-to-center.
Thanks for the tips, I am definitely going to work on these plans based on your tips. 1) I don't know if I said this before, but I'm planning on cutting these out with my scroll saw using ABS. Are sloped ramps really necessary? I mean it not that hard to put them in there, just are the required? 2) I'm planning on having the rotation bushing on the bottom level like you did with your laser cut cannon. I believe it"s in the second PDF. 3) The main cannon part is 4" in diameter, the magazine wall is 5/16", the holes for the uptube are 1/4", but will need to be drilled bigger to fit the tube. I can't remember how far apart the barrels are, I'll have to look. 4) I'll probably end up making them straight, I angled them because I didn't know if I could get long enough ramps if they were straight. 5) I'm planning on having evenly set screws all around the cannon. Not sure how many, six or eight should be enough I would think. 6) Yes, I think they are too far apart myself, will space them closer in design 2. So thanks for the suggestion Kotori. Design two will be built from 1/16" pieces with closer together barrels, and not have angled ramps. BTW, Kotori, how did those laser cut cannons end up working? Beaver
If you cut it out on your scroll saw, then you don't have to be quite as concerned about production method. You can mix and match a couple different sizes and materials for best results. Hand-cutting all those layers from 1/16" ABS would be a lot of work. As for sloping the ammo ramps, remember that the entire mechanism is gravity-fed. If you don't slope the ramps, you are depending on the rocking motion of the ship to move rounds into the breech. Although this works, it is less reliable than a sloped ramp. My own laser-cut cannons are in the predreadnought battleship IJN Mikasa, almost ready except for superstructure. They were tested and proven functional, but have not seen combat yet. Beaver, how do you plan on producing cannon bases?
So do you think it might be better to just use a piece of 1/4" ABS with a piece of 1/16" welded on top? Is there anything special about them as long as they hold the rotation bushing and fire the cannon? I'm thinking of designs, but don't want to put anything on paper until I understand what every piece has to do. Beaver
The cannon base establishes the initial airflow conditions, based on its cross-sectional area. I have found that, or triple and quad cannons, the best results are achieved with sch40 tubing of nominal 1_1/4" pipe, and a cross-sectional area of 5/8". Also, different designs may be more or less difficult to manufacture.
What if I were to take a 1" ID piece of ABS as long as I would need for the accumulator, then weld a 3" piece of 1" OD tubing inside of that. After that has set, weld 1" piece of solid ABS rod inside the 1" OD tubing at the end that is facing the acum'. Then drill the holes for the air to get to the magazine, and another hole for the buna ball rod. The extra 2" of the 1" OD tubing would be for that piece that is pushed to fire the cannon. (what is that called BTW ) Sound good? Does it even make sense???? Beaver
Sounds like a lot of failure points. Most breeches I have seen are made from solid 2" pvc rod, drilled and threaded....
New plans have been drawn. Changed a lot of things from the other design, and I think it is better overall than the last one. The plates are 4" in diameter, the slots are 9/16" on center away from each other. The outer ring of the magazine is 1/4", and the hole for the bushing is 1/2" in dia. If there are any other dimensions you'd like, just ask. http://www.rcnavalcombat.com/Portals/0/Users/Beaver/Scan_Doc0004.pdf http://www.rcnavalcombat.com/Portals/0/Users/Beaver/Scan_Doc0005.pdf Evaluate and leave some feedback. Beaver
Depends on what the I.D. of the rotation bearing is..... You are cutting it close to too small a cross section to support airflow for 1/4" triples.
Apologies for how long it has taken to find this thread again. Beaver, your post about accumulator construction is good. Unfortunately I do not have permission to say more on a public forum. Your magazine design is coming along nicely. I think you're almost ready for a prototype. I agree with Cannonman, though. Flow-wise, you are cutting it very close for a triple 1/4" cannon. Remember what I said about a 5/8" bore for airflow? That's how big the final ID should be. That means the bearing has to be bigger, the bearing sleeve has to be bigger, and the mounts for the bearing have to be bigger. Once you fix that, though, I think it's ready for a first test. Build one and try putting it together. That first test always identifies a few more weak points to correct before you build a batch.
