Yeah I stagger them primarily because it allows for the hull to maintain its overall rigidity until I glue it. It keeps the hill from having a natural twist to it just because of the slits. I used it initially to take care of a layer separation issue that would sometimes arise at high stress locations because of the shrink and then I found that it made the parts much less temperamental to enclosure temperature
I have a post in the 3d design area talking about my printers and the cabinet I put them in. It's temperature controlled to 110 F. I'm just saying, I have none of these issues with ABS on extremely large/dense prints. I print ABS exclusively, and I can use 25-30kg in a month depending on how furious I'm building. No slits, no weirdness that needs correcting later, no problems. Both ships in this picture are ABS printed with no after-print treatments or corrections needed. Parts fit 100% right the first time, no warpage or shrinkage. .32 layer height, .5 line width on a .4 nozzle, 2mm walls, infill density varies wildly depending on part. Supports obviously when necessary, .64mm air gap between supports and bodies. I like tree supports for hulls but try to use standard grid supports whenever possible. Calibrate your printer with a single wall thick open top cube and set your extrusion multiplier correctly to get the best accuracy. Calibrate E-steps. I also have auto leveling on both my printers with BL touch sensors. And I'll be honest, my ceramic glass beds are starting to fail (prints rip up layers of glass sometimes) and they *still* adhere and have no issues to the now moon-crater-surface print beds.
I've finished printing the test hull! Well here it is. Nowhere near the final form, but this is certainly off to a good start. I'm going with a very traditional arrangement of hardware. Starting at the stern, we have the main servo tray. This will contain the rudder and firing servos. Eventually I will add MAV-3 poppet mounts for the firing servo to push, but I just whipped something up quick for now. Next is the stern cannon. You can barely see a cutout where the MPA-7 firing actuator will go. The actual cannon mount is covered up by the magazine. It'll be four #4-40 screws sticking up from the hull, that will slot into holes in the cannon base. I wasn't entirely satisfied with the initial version that was printed back aft, so I made some revisions to the CAD model that only got printed for the forward cannon. You'll also notice that the stern cannon slots between the propshafts. It's a snug fit right now, but I'll be raising the stern cannon by a few mm. That's primarily due to clearance issues up forward, but it'll also give me a little more room back aft. Next up is turret rotation and electronics. I experimented with stepper motors for rotation, and proved that they will do the job. However, they require careful setup, special boards, and cannot easily be swapped for other options. So instead I'm going to use standard servo bodies. It's hard to find standard-sized servos capable of more than one rotation, but they do exist. Or you could use continuous-rotation servos. Or you could gut a super-cheap standard servo and just use it as a gearmotor. Lots of options if it's set up for standard-sized servos. Next to the rotation servo (not final location) will be a receiver tray. Just a small platform to stick your receiver to, whatever receiver you want. This puts it nice and close to the majority of electronics in the boat, minimizing the number of servo extensions (read: potential failure points). Lastly, opposite the receiver will be the ESC board. This is a Pololu TReX Jr, a 3-in-1 combination ESC for robots. It has two 5A (2.5A continuous) reversible ESCs and one 10A (continuous) non-reversible ESC. The plan is to use one of the reversible ESCs for drive, one ESC for turret rotation (if using gutted servos), and the non-reversible ESC for pump. The final result is a 1.75" square that is easily waterproofed and controls most of the ship's functions. This should simplify the wiring of Big Gun ships in much the same way that BC's multi-C and multi-B boards simplified the wiring of Fast Gun ships. Between the electronics is the pump. This is not the final pump, it's just a stand-in borrowed from one of my other ships. I plan to CAD something that fits better. It's very strange to have the pump aft of the motors, but there just isn't room to go the other way around. The drive motors are RS-365SH, and I've used them in a number of other Big Gun ships. I used two of them in my VU, it was easily able to get to speed and drew less than an amp each. The Mikasa is smaller and sleeker, so this is easily enough power. Gas will be provided by a 5oz CO2 bottle. I'll use a 90-degree ASA adapter to side-mount the regulator. The setup in the photo is sized for a 20-oz bottle, so the regulator is pretty far off to the side. The final version will have a shorter extension. Batteries go on either side of the CO2 bottle, embedded in the water channel. I will try to fit the larger 5000mAh hard-case batteries, if possible. Up to the bow cannon. After printing the barbette and turret, I realized I can use a larger diameter magazine. The current magazine fits 110 rounds in a single 3-inch-diameter layer. I can go up to a 3.5-inch-diameter magazine. Unfortunately when I cut out a space for the accumulator, it left the skin too thin to print. I'll have to raise the front cannon a couple mm so I can actually fill in those holes. Weight distribution looks good so far. Welp that's about it so far. I'll be adding mounts, cutouts, cross-braces, etc. next. Expect progress to slow down for a while as I CAD up all of the little changes.
Just a thought, but you can leave the hull as-is and just glass the bottom. Which I would recommend anyway. Or at least just tiny cloth pieces to cover the holes and then paint the whole thing with epoxy. Makes it *a lot* stronger.
This is just the prototype, it's a quick-and-dirty print for testing, fitting, and ergonomics, but will not be completed for combat. Too much unfinished in the design at this point. Once I am satisfied with the design, I plan to print at least four hulls, and all four will most likely get fiberglassed.
No new photos because progress has been slow. I put the ship in the bathtub the other day and loaded it to the scale waterline. approximately 11lb, with a CG 18 inches from the tip of the ram bow. Wouldn't you know, that's EXACTLY the center of the ship? Well, now I have a target as I arrange things.
My printing issues are solved! After a number of tests, I have finally resolved the bed-separation issues I was having when printing the largest portions of Mikasa's hull. All I had to do was go over my heated enclosure and aggressively seal every possible opening, including the one on the top where the plastic goes in, and then viciously attack my PEI print bed with sandpaper in the areas that were separating. That, combined with a much coarser layer thickness (I was originally printing at 0.1mm layer thickness) and I am now pulling parts off my printer every 7 hours or so with no problems at all. Most of the improvement came from sealing my enclosure better, followed by changing my layer thickness. The sandpaper assault was that last little detail for the biggest, most troubled hull sections. Now that that's resolved, I have turned my attention back to the CAD model and finishing up the internals. By this weekend I will have the next test hull, which will hopefully be the first production hull. Expect more photos then. Once I am satisfied with the hull, it'll be on to cannons and superstructure. Oh yeah, and I know that this sandpaper assault will also make removing finished parts more difficult. I ordered a new magnetic detachable bed, and two flexible print surfaces for it. One will get the sandpaper treatment for big parts, the other will be kept pristine for parts that don't need such insane bed adhesion.
.1 layer height on a whole hull print? The QE 3dp takes 5~ days to print...I can't imagine how long it would take at .1!
Well that's another kilogram spool used up. But Prototype Hull #2 is ready. As before, this is not the final hardware. I just grabbed a handful of random standard servos from the pile, and I borrowed a regulator assembly and pump from one of my bigger battleships. So don't think about it too much. But the actual mounts are pretty much finished. Starting in the bow, we have the forward rotation servo. This can be a continuous-rotation servo or a multi-turn servo, depending on whether you want position control or velocity control for your cannons. I also have a barbette and turret printed out, so you can see how that's supposed to look like. It's a bit short right now though, without a deck to sit on. That's one of my next tasks with the CAD model. You'll also notice I have places for deck hold-downs to go. The current plan is to use #6-32 T-nuts for the forward and aft decks, and then magnets for the amidships deck. The forward cannon itself is... not done yet. While the mechanics of the cannon are designed, prototyped, and tested, I still have a few details to finish. The magazine can be expanded to at least 85mm diameter, possibly more. That will give me at least 50% more ammo without having to use multiple layers. There are a few other minor details to change as well. Moving aft, we have the CO2 bottle and battery boxes. Pretty simple, it's a 5-oz bottle and two 2S 3Ah in parallel, for a total of 6Ah at 7.4v. That's an enormous amount of power for a ship this size. The CO2 bottle will have an ASA and plumbing fittings to mount the regulator off to the side. This side-mounted arrangement is pretty common in Big Gun ships. The regulator assembly in the photo is a bit big, it is sized for the 20oz bottles I use in my bigger battleships. It's a simple matter of buying a shorter fitting from the store, though, and then it'll easily fit off to one side. The bottle itself will be angled up by resting on top of the pump. This will prevent liquid CO2 from entering the regulator, hopefully minimizing freezing issues. I can only hope that 5oz will be enough. It should be, as long as I can fill it close to the design 5oz capacity. The engine room is pretty simple. Two RS-365SH motors, more than enough power for a boat this small. I will definitely have to dial down the throttle channel to reach speed. The motor mounts are built into the hull, and the hole spacing is standard enough for a variety of motors of this size. It even fits my nice Maxon A-max motors, but if I tried those it'd probably go faster than my Fast Gun predreads. The bilge pump goes in between the propshafts. That's a pretty skinny space, so I'll most likely have to design a custom extra-narrow pump housing to fit. It shouldn't be a problem though, since I have already printed similar pumps. Adjacent to the motor mounts is a pair of electronics platforms. One will hold the receiver, one will hold the ESC. As mentioned before, I will be using a dual robot combat ESC, providing two symmetrical, reversible DC motor channels and one non-reversible DC motor channel. This all-in-one ESC will provide propulsion, pumping, and possibly turret rotation (if the operator wants velocity control). The next frame has servo mounts for turret rotation and fire control. This is not the final version, as you can see there is lots of room between the servos and the water channel. I have updated the model to lower the servos by 12mm, but my printer ran out of plastic before I could print the updated version. Like most Big Gun battleships, firing will be via MAV-3 poppet valves. I still need to whip up a plate to stick on the firing servo, something to hold the poppets. The servos will be supported on both sides, but I ran out of plastic before I could print the aft support posts. In the interest of minimizing support material, I designed those supports to get solvent-welded in afterwards. Last up is the rudder servo. I am no longer using a two-servo tray back aft. I test-fitted the original design with both rudder servo and firing servo, and there wasn't enough room for the firing poppets. That's why the firing servo got relocated further forward. You can see a cutout in the bottom of the hull for the stern cannon's actuator and air fitting. The reason this is Prototype Hull #2 and not production hull #1 is because I am not satisfied with the bow and stern shape. The bow in particular has been frustrating me to no end. In the first version, the ram bow was too fat. Now the ram bow is itself is good, but the transition between the ram and the upper and lower portions have an extremely visible crease. I may spend more time trying to tweak the model, or I may just attack those sharp knuckles with sandpaper. Hopefully the print is thick enough in that area to handle a little sanding. My next major objectives will be re-printing the bits I needed to adjust, making new larger cannon magazines, and making decks. EDIT: wait a second. Out of curiosity, I just test-fitted a 9oz bottle. It'll fit if I can make a low-profile pump. Does anybody know of some very short motors?
Anything the diameter of a 550, even half the length, is too large to fit. Big Gun uses much larger outlet diameters than Fast Gun, so it doesn't take a big motor to keep your boat afloat. After a little searching, I ordered a few 300-sized pancake motors, of the ultra-cheap variety. I'll give them a try, and if that doesn't work then I'll keep trying. I think this moves up the cannons on my priority list. I need to get a final version built and working, so I can run an endurance test to see how much CO2 it actually uses. If a 5oz bottle is actually enough to empty my magazines, then I don't need to stress about fitting a 9.
The guns go BOOM! Today I tested what is likely the final prototype cannon. The cannon base was relatively easy to finish and assemble. I am confident that I can produce them on a large enough scale to outfit all of the planned hulls. The magazine fit over 160 rounds, exceeding my goal of 75 rounds per barrel. The gently-sloped magazine floor consistently fed, and I was able to do a full magazine dump without a single round getting lost. The only real fault I found was that the pistons I used to close the breech often failed to cycle, leaking gas and (rarely) allowing multiple rounds to feed. Actual hitting power was very impressive, pushing rounds downrange at around 125-130FPS at 100PSI, and about 150FPS at 120PSI. When the breech cycled correctly, the numbers were even higher. The rotation bushing was remarkably steady, despite the impressive recoil of the cannon firing. So now I'm taking advantage of rapid prototyping technology to try a different design of piston. This one will only half-close the breech, but *should* cycle more reliably. I know I'll lose some efficiency by only half-closing the breech, but right now the cannon is almost always failing to close the breech at all and it's still pulling down some impressive numbers. The one thing I don't want to do is to overlap the rounds like most Big Gun cannons do to get single-fire, because my tests have shown that overlapping the rounds enough to reliably single-feed results in significant velocity loss. Not too big of a deal if you're a Montana-class battleship with a 24-oz bottle, and you can just blow more air at the problem. But I've only got 5oz to play with if I get a perfect fill, and that's pretty rare. I'm also thinking about the cannon mount, and whether I should change it or not. Tomorrow when I test the new pistons, I will also do an endurance test. I just finished filling one of my 5oz bottles, and bled it down to exactly 5oz of CO2. The endurance test will also help me get a better feel for the recoil, and whether or not the current cannon mount is adequate. If everything is good, I will go into production mode and make seven more of them.
More cannon testing! First, I put one of the new regulators on a 20oz bottle, so I could presssure-check the cannon, measure velocity, and see if the new pistons are working better. The numbers are just as good as before, with noticeably improved reliability. No double-feeding at all, and the pistons never got stuck in the up position either. Next, it was time for the endurance test. With a 5oz CO2 bottle, precisely filled then bled to 5oz CO2, I was able to achieve 162 full-pressure shots at 150PSI. That is (barely) enough CO2 to empty the magazines of both turrets. I was initially concerned, since getting a good fill can be difficult sometimes. Then I went back and reviewed combat footage, and counted shots. I'm feeling a lot better about it now. Big Gun battles are not limited by magazines or CO2 capacity, but by time. Between the reload times and the maneuvering, most gunnery exchanges are akin to jousting, with head-on passes and exchanging a single broadside at a time. Getting two ships in range of each other and on parallel courses is very difficult to do if one skipper does not want it to happen. In order for me to come anywhere CLOSE to emptying my magazines in a 15-minute period, I would need another suicidally-aggressive skipper who is willing to stand broadside-to-broadside and slug it out for minutes at a time. We would almost certainly both sink, and require resheeting immediately afterwards. Since I counted them up to establish a cannon-fire baseline, here are few fun numbers from my visit to the WWCC last year: In the 1st sortie, Gascan's VU fired approximately 30 volleys, around 105 rounds total. He sank two transports, and caused an estimated 1/3 to 1/2 of the damage on the Alsace. In the 2nd sortie, my VU fired approximately 35 volleys, around 111 rounds total. These were mostly split between Gascan's VU and the Westfalen. Gascan's VU returned to port with 15 hits below the waterline, a new high score. In the 3rd sortie, my VU fired over 45 volleys. Westfalen was pulled from the water in sinking condition, although I didn't get a damage tally. This was with me being reckless, possibly even suicidally agressive. I would be very surprised if the Mikasas are able to use up their gas and ammo in a single round.
Not your usual Mikasa fare this time. Today I'm bending barrels. Not something most Fast Gunners do, but in Big Gun it's very important. Big Gun cannons launch their projectiles straight up, so a barrel bent at least 90 degrees is required to send your shots towards the other ship. This bend also adds backspin to the rounds, which has some interesting and beneficial effects. First thing's first. This is my tubing bender assembly: It's a common automotive tubing bender securely bolted to a wooden plate, with a number of drilled holes for stop points. I tried a number of different tubing benders before I got something I was satisfied with. This one snugly fits three most common tubing sizes for barrels: 1/4", 5/16", and 3/8". The other important feature is that this bender has a very small-diameter mandrill, allowing me to make very tight bends. My first tubing bender had a larger diameter, and barrels with the larger bend would not fit inside the barbette for some ships. A setup like this is absolutely vital if you want consistent, repeatable bends. Trying to bend barrels by hand and eye is a crude and imprecise business, not the sort of thing you want if you want the job done right. Today's barrels are 5/16" OD steel brake line, suitable for 7/32" rounds. This material can actually pass 1/4" rounds, right up until it gets bent/dented/deformed in any way. 7/32" rounds, however, can get around the bend and past dents. A brake line barrel will generally last 2-3 years before needing replacement. Stainless steel barrels are tighter tolerance and last longer, but require cerrobend (wood's metal alloy) in order to avoid collapsing the tube too much in the bend. I'll do a separate post on that next time I make stainless barrels. Here we can see the end-stop in action. I bend the barrel until the working arm touches the end-stop, then release. The barrel springs back a bit when you release due to elastic deformation. Different barrel materials spring back different amounts, which is why my end-stop holes are not labeled. The only way to get a particular angle is to bend a barrel, measure it, and then make adjustments. I start off shallow, and bend more as needed. Once I have the right angle set, I can just knock the rest out very easily. This set of six barrels too me about 30 minutes to make, most of which was cutting the tubing to size. I have just a little more trimming to do, and then these barrels are ready to install. They're destined for the stern gun of one of my VUs. I'll be putting stainless barrels in the Mikasas, so I'll do a whole separate post on the use of cerrobend for tight-tolerance barrels, so please look forward to it. The new barrels, temporarily installed in the cannon for test-fitting. This fixed six-barrel cannon fills the C and D turrets of the VU. It has a new 3d-printed magazine that's almost a pound lighter than the original while maintaining the same size and shape. I will need to shorten the upper barrels some. They should be only 1/4" above the lower barrels to improve the odds of chunking, or at least getting a nice, tight pattern. I also plan to put some heat-shrink tubing over the outsides to provide a little protection against dents. The previous barrels got absolutely battered. They kept firing fine, but oh boy were they lumpy by the end.
Yes. This cannon has a valve and endcap machined from solid PVC, then solvent-welded in place with PVC glue. It is quite strong.
Making cannon accumulators! Coyote, Gascan, and I spent a good part of Saturday soldering these beauties together. These are 1" copper tees, with brass endcaps soldered in. Half of these will be oriented "flat" style, with the valve body in the branch, and half will be oriented "vertical" style with the valve body in the street and the branch sticking up. There's a bit of variation among the fittings, but they hold, on average, a little over 3 cubic inches of air. Not sufficient for a triple cannon, but good enough for a twin 7/32". I have magazines printing right now, the first couple sets should be done in a day or two. Then comes laser-cutting decks, printing superstructure, and then printing as many hulls as I can before the battle on April 10. I have also finished printing my first complete hull in PETG. I'd post a picture but... it looks almost exactly like all the other hull pictures. I'll start posting more ship pictures when I actually have new things to show. I also realized that my cannon mounts are inaccessible when the cannon is assembled and installed, which makes disassembling it rather impossible. An embarrassing mistake really, but something that anybody might make. I'll have to modify the CAD model before I print any more hulls, and make a quick-fix for the hull I've already made.
