09/01/13- When you're waiting for parts, you might as well work on something. I see it as a blessing in disguise because I'm not as tempted to rush through stuff that I'm less interested in to get to the good stuff.
PHASE 2: WAITING FOR PARTS
Before we get started, I wanted to warn you that although Matorro and Heng Long parts and construction look nearly identical, you might assume that they wired the 8-pin connector and LEDs (for example) the same way... but you'd be wrong! Verify everything if you scavenge parts.
THE TURRET (SUPERSTRUCTURE) MECHANISMS
The Matorro Jagdtiger is pretty barebones in this regard, providing elevation control via the unidirectional rear-mounted cam, and an airsoft-style spring-powered pellet gun. I had much more ambitious plans. I copied the cannon mechanism design from the Elefant; that is, the gun would have servo-controlled recoil, with pivots to a plate for servo-controlled elevation, which would pivot atop another plate anchored to the hull, for traverse. This is simple enough in concept, but the real challenge is scrounging up parts to make it happen (since I don't have a machine that I can tell what parts to make). It's all about shapes and materials, and what you can scrounge that does the job.
The Recoil Assembly: The recoil assembly was the most challenging of the three. Firstly, the cannon assembly had to be disassembled into components so see what there was to work with... preferably, without destroying a dumaflache that might later prove to be useful. The glue on the Jagdtiger is very tenacious, and few parts separated without a fight. To remove the barrel, I had to drill/Dremel down into the inside of mantlet, basically destroying the mounting that had held those parts together. I was able to get the barrel mostly intact (but the short section that had been recessed into the mantlet was ragged), also the mantlet, and the box-like sleeve/cap that screw-coupled to the end of the BB-"receiver".
Now that I had all the parts separated, it was time to figure out how it would work. The issues to be addressed were 1) getting the barrel to slide smoothly in/out while centered in the mantlet, and 2) making it so that it could be adjusted and assembled/disassembled. Point #2 is one of those subtle things that's antithetical to the brute-force method of making stuff work. You can't just glue the mantlet to the gun as it was originally assembled, or you won't be able to remove the gun to adjust and do the inevitable maintenance. Even though you can remove the sleeve/cap from the gun, the screws to do it are difficult to access once it's assembled. Fun stuff!
I can't stress enough how important it is to design a path to disassembly. Even after you've tested it bunches of times and are satisfied with its operation, at some point in the future, you'll unexpectedly need to take everything apart to adjust or fix something. Planning for this will make it much easier for the future You.
To center the plastic barrel (a sleeve over the aluminum BB barrel) within the Saukopf mantlet, I focused on finding an inner sleeve. The barrel flares out at the mantlet, so when in recoil, there should be an equal-sized gap at the mantlet opening surrounding the thinner section of the barrel. The sleeve would act as a guide for the wider section of the barrel, like the housing for a piston. Scrounging a good-fitting part wasn't easy, but eventually I turned up an extensible fitting from a pond pump. The turned out to be a perfect solution since the inner diameter of one section matched the wider barrel end outer diameter. The other extensible section was fitted with a rubber O-ring, which gave me a way to secure the mantlet with guide tube to the gun sleeve/cap without gluing them together. It must be removeable so you can remove the entire assembly from the hull for maintenance. The final piece of the puzzle was to put a rubber O-ring on the aluminum barrel so that the plastic barrel sleeve could be wedged on and adjusted so that it was at the correct place when the recoil mechanism was at battery.
The rest of the recoil mechanism was straight-forward. The BB-gun mechanism was gutted to guide and support the aluminum barrel's deeper travel into the mechanism, and cuts were made to mount a micro servo and exit the flash tube wiring. The servo was mounted to provide as close to on-axis travel as possible. The farther away it is from the barrel travel axis, the more side-pull is exerted from the linkage. If there's play in the barrel guide, the side pull will create unwanted side-to-side motion and extra friction. A simple wire linkage is screwed to the aluminum barrel; since the servo's not mounted exactly on axis (due to my great craftsmanship), the servo pull occasionally imparts a slight rotational motion to the barrel as it retracts. A more elaborate design (or using a linkage with less slop) would restrict the barrel screw to a linear path but I'm lazy and told myself that I didn't want to introduce any more friction since it's a weenie micro servo. Truth is, it wasn't worth the effort to me.
Elevation and Traverse: The elevation and traverse mechanisms followed the pattern used in the Hooben Elefant: An elevation yoke was mounted on a small platform which pivots (for traverse) on a larger metal platform screwed to the turret housing. The placement of the articulation must be carefully selected to ensure that the mechanism operates properly with the mantlet. I used the original location of the elevation hinge pin supports (measured), then test-fitted the assembly to determine the location of the traverse pivot (eyeballed). I believe I get more traverse angle than the actual Jagdtiger's 10 degrees, but I'm okay with that.
Once the Clark board arrives, I'll test the servo elevation to see if that's really what I want to use. Then I'll be able to mount and fully test the mechanisms.
There are a zillion little details that you can focus on to improve, and the most obvious ones are a good place to start.
The stock Matorro Jagdtiger has only one articulated hatch: The commander's hatch on the top (for loading BBs). I'm sort of a sucker for that kind of thing, and this model practically screams for them. I must say that it was difficult to get started though, because doing this commits you to a repaint or touch up. No matter how careful you are, cutting out hatches invariably involves doing patch-up work. I didn't know if I could do the patch-up paint work to match the original paint job that I'd liked so much. As some joker said, you can't make an omlette without breaking some eggs.
Rear Doors: The rear hatches/doors weren't too difficult to cut off with a flexible razor-saw. This seemed like the most obvious way to do it, given the easy access: Just place the blade along the flat edge and begin sawing, trying not to damage the wall too much. The flexible blade helped minimize collateral damage to the wall surface. Still, considerable putty work was needed to rebuild the back of the hatches and the surface edges of the wall.
The missing wall sections on the hull were added to the inside of the turret to support building them up with putty so they'd be flush with the outside.
With the hatches removed (as one piece), the part was cut apart into hatches and hinge sections; the center pieces in the hinges were sacrificed to give access to grind out the hinges cleanly with a rotary tool. The center hinge pieces were reconstructed with Evergreen strips, then placed in position for drilling to make working hinges.
Since it's eyeballed work and top and bottom hinges are drilled separately, it's hard to make sure that all 4 sets of holes per side are drilled at exactly the same angle. If one set's off, the door may have a tendency to angle out, depending on which side of the hinge opens first and how free the hinges are. In other words, on first drillings the doors may not work perfectly, and tend to not stay closed perfectly flush against the wall. How do I know this? My left door had this problem. I could push it closed flush, but the top would tend to lean open slightly. The solutions were to redrill the holes, make the pins fit tighter, or put a lock on the interior of the door (or glue the door shut, which sorta defeats the purpose, huh?).
I built the locking mechanisms relatively quickly and haphazardly from a poor photo, eyeballing lengths, widths, and pivot positions. Consequently, they aren't the great works of precision that they could be. My focus was to make a working mechanism that was durable enough to be used; I didn't even think of fitting it to the doors until I got to that step. When I got there, I discovered that the side walls were too thick for one of the handles to clear, so I shaved the wall thickness down. Then I discovered that the locking bars were too flush to lock so I angled them out with the support blocks (instead of just thinning that section of the wall). In other words, I used the "brute force" method of trial and error modeling to get the damn thing to work (or "prototyping", as I like to think). A good modeler would use the dry run lessons to build the mechanism correctly. Not me: Once I got the left door to lock, I moved on to other challenges!
The Front Deck Hatches: These begged to be articulated; maybe they'd be useful for accessing switches or something. It's sort of a dreaded been-there, done that thing for me, and I knew it was going to be ugly. The main decision is whether to cut from the exterior or the interior. Cutting from the exterior means that a significant portion of the hatch edge would need to be reconstructed, and possibly the deck surface too. Cutting from the side with the flexible saw would remove quite a bit of thickness from the hatch edge which would need to be rebuilt all the way around. Access is not ideal and there's a significant likelihood of collateral scraping damage to the hull surface. This would be true if you drilled starter holes as well. An Exacto blade, while thin and less destructive, would never clear the hull surface with a handle attached, and it's probably not a good idea to test the flexibility of an Exacto blade. Besides being really tedious. I've heard that some people use thread to cut hatches. I definitely don't have the patience for that! A Jeweler's saw? Difficult to get the angle, and all those broken blades to replace...
It's really the same story cutting from the interior. The difference is that you can more readily use a rotary tool, which means that you can examine the carnage sooner. A thin metal rotary cutting blade can get relatively flush with the cut line and you don't have to worry about the blade mounting screw marring the surface of the underside. The trade off is that it's a blind, less well-controlled cut that tends to melt plastic. It can therefore do some really ugly damage if you cut badly (which is why you don't do it on the exterior). It really has to be run at a decent speed to avoid stalling and binding, especially since the thin blade is likely to be spinning while bent to accommodate the cut angle (and that mounting screw). Again, the access isn't ideal: The hatch dimensions are too small for my blade to fit inside the depression to do the job without cutting somewhere else where it's not wanted. Like I said, spin her up and examine the carnage sooner. You can then start working on repairing the damage sooner too. Once you've made peace with the fact that you're going to be doing some patch work, it's all good (or bad).
Once you're past that trauma and patched the damage, you can look forward to mounting the hatches. I use simple brass tubing because it's a durable material that comes in sizes that telescope together and stay put without messing with springs and other stuff. With a deep enough, properly-sized installation hole in the hatch, the inserted tube practically stays put by itself (but super glue is a good idea) and won't break off. My clever monkey tip: Trace the outline of the hatch on the hull before you install the brass tube in the hatch. That way, you'll know where to drill the hole to install the hull-side tubing! Otherwise, you'd be as stupid as me and have to make a wild-assed guess (wrong), then have to relocate the hole you've drilled in the hull.
The Binocular Periscope Hatch: Fortunately, there are opportunities for redemption. From a quick study of this tiny hatch, one might conclude that it would be nearly impossible to cut since it's flush mounted, with tight turns at the hinge. The only tool that seems up to the job would be an Exacto blade; you might be able to do it with a bunch of tiny drill bit holes, but you'd need a really tiny (and fragile) bit to avoid creating a huge gap. Or the thread method. The problem with using an Exacto blade is that you'd spend hours scribing through the thick plastic, and the width of the blade would become a hindrance the deeper you cut.
The solution: Make the plastic thinner. By grinding away plastic from the inside, you can thin the plastic enough so that the Exacto blade doesn't have to cut very deeply, and you won't risk damage to any surface detail. This works because it's a straight down cut along a sculpted trough. With a Dremel, you can grind plastic from the backside, monitoring thickness by holding it up to a light. When it's thin enough, light will shine through the panel cut line, and your Exacto blade will cut through it relatively easily, leaving a thin, clean line. When the part's cut out, you can backfill with putty to restore thickness. (Hopefully, you were a clever monkey and drilled the hinge hole before cutting out the hatch.)
To be honest, I have no idea why I bothered, except as a challenge and to show off. The little sucker is tough to open without prying the edge up with a tool, and once you've got it open, then what? Making a binocular periscope isn't high on my list of priorities, and then I'd have to detail the underside. Still, it was fun to do...
Barrel Traveling Support and Lock: Originally, this was an unarticulated part that was stuck to the hull by glue or paint, sculpted in the stowed position. When cut up into working detail, most of it was an easy job to articulate but there were a few problems. The barrel clamp's diameter was too big for the barrel: The top section was shortened and re-curved with heat. After that, the clamp didn't fit over the headlight quite as easily. I needed to lengthen the struts to get that to work, which was a dicey job for someone like me who works by eyeballing and guesstimating: I re-did the struts in Evergreen styrene and almost got the length and angles right the first time.
The barrel clamp's latching mechanism needed to be durable, so I made it of parts cut from fairly substantial copper sheet and piano wire. (I'd tried to use some photo-etched clamps for this, but the brass was too thin and fragile.) The weakest part is the clamp hinge, which is just a cutting and hinging of the original plastic part with a little bit of putty for reinforcement.
Lower Hull Zimmerit: The artist who finished the Jagdtiger had sculpted zimmerit on most of the tank. He'd done an interesting job of it that I liked-- it was crude and irregular in what I guess is a spackling putty, but fit the look perfectly-- it almost looked (for lack of a better word) impressionistic. The replacement Heng Long hull didn't have zimmerit, so I needed to add some to the front. Problem: I'd never done zimmerit before, and I'm not big on doing repetitive, time-consuming things. Moreover, my sculpting "style" is naturally more structured, so I would have a hard time matching his style... plus, I use epoxy putty. Rather than spend a lot of time trying to copy his style, I cheated. I made simple press molds of sections of the Matorro zimmerit and zimmeritted over a thin layer of putty. Quick and easy. Fortunately the front panel faces downward and is hard to see, which hides the stylistic mismatch.
Lifting Hooks I think all the hooks are inexplicably backwards on the stock Matorro Jagdtiger. Mechanically, it doesn't make sense for the hooks to be facing inwards (cables would unhook if there were slack), so I looked at more pics which seemed to confirm the error. A simple fix it would seem... if the glue weren't so tenacious! After breaking the first hook trying to get it out, I grinded from the interior, cut the outline with an Exacto blade and pushed/rocked the others out. The rear deck is missing hooks from around the round fan covers.
Mud Guards/Skirts In most wartime photos, Jagdtigers usually don't have mud guards or have sections of missing mud guards; that's why most modelers build them that way. I like details to be accurate, but my aesthetic preferences come first. Generally, I prefer a fairly "new" look (versus "battle worn") and I like full mud guards because they make the tank look bigger and not like it's missing teeth.
The Matorro Jagdtiger doesn't come with mud guards so I bought a sprue from the Tamiya King Tiger kit: Nearly perfect fit (some bolt detail doesn't align exactly with the hull's mounting detail). It costs a small fortune in Walther's hex 00-90 screws to do the job (Wish I'd done a better job installing them!). The upper screws were fastened with a washer and nut, but the bottom screws were glued in and snipped to avoid interfering with the upper and lower hull fit.
Mud Flaps I've learned that there are 2 things you need to watch out for with mud flaps: Losing them and breaking them. They're big so losing them isn't that much of a concern (except in tall grass in a large area). Breaking them is. It doesn't matter if you replace hinge pins with metal or replace the whole flap with metal: When momentum sends you into something immoveable, something made of plastic will break. To reduce the risk, be like the wise bamboo instead of the sturdy oak. I drill holes and attach them with elastic thread so that there's no rigid hinge to lose the battle with an approaching wall. The fit isn't as good, but it's a matter of priorities.
Foliage Hoops: (I think that's what they're for?) This was another detail I'd noticed from photos, and the Matorro Jagdtiger had four of them along the back of the turret. Most photos showed them all around all four sides of the turret and rows of them running along the side of the rear deck. I didn't do the rear deck side hoops since it would be difficult to fit them with the tools that were already there.
The large hoops were easy to do with bent wire and a couple of drilled holes. However, the smaller hoops to the sides were a puzzle. I didn't feel that I could make the whole thing as one piece, especially since there were so many of them. Initially, I was satisfied with just the main hoop, but then it began to bother me. I finally figured out an approach to doing the small hoops: I made a bunch of tiny rings by wrapping thin wire around a thicker wire and clipping them off, similar to making chainmaile links (I'm sure everyone can relate to that!). The smaller links were emedded in a tiny blob of putty to the sides of the main hoop.
Magnetic Hull Closure: This is a huge convenience so I try to add it whenever possible. During the build, the upper hull comes off so many times that screw-fastened threads would be shot by the time I was finished, in addition to all the man-hours lost unscrewing the hull. This was a super-easy install thanks to the slide-in front and the wide platforms on the side of the lower hull.
Neodymium magnets come in many different sizes and strengths, and it's certainly possible to overdo it. They also are a great way to make ant-proof "moats" for outdoor food bowls for pets.
PHASE 3: THE GUTS
Other options for a barrel elevation mechanism were limited: The cam-operated HL elevation unit wouldn't work because it's secured to the turret ceiling (when it should travel with the traverse mechanism). I could buy a Tamiya elevation gearbox, but they're noisy,seem to have a lot of slop in the gears and are expensive for what you get. Someone (Heng Long?) makes a similar plastic-housed version that's quieter and more robust, but they're not easy to find. (The one I have was used for the traverse mechanism.) Consequently, I decided that the servo-operated elevation was good enough. (After-the-fact: Wish I'd used a gearbox! See sidebar.)
This brought another problem to light: The "jerkiness" emphasized the "sproinginess" of the barrel. With the plastic barrel mounted on the aluminum barrel, the gun was quite barrel heavy, and each movement produced a springy, up-and-down motion of the barrel. My design had some flaws that contributed to the problem: The traverse plate was minimally supported ahead of the pivot point, and the support plate was made of plastic that extended over the rear edge of the mounting deck.
I threw a handful of fixes at it. An additional brass plate was added in front of the deck to help keep the traverse plate from lifting up at the rear/dipping down at the front (a wider single deck plate would have made this unnecessary). I glued a weight and added a spring to the back of the gun to help counterbalance the weight of the barrel and dampen the oscillations.
The traverse mechanism was an easy install, with the plastic gearbox hot-glued on top of the elevation servo, and hot-glued at the top edge to the elevation yoke. This keeps it securely positioned so that it doesn't move if/when it hits the side-to-side limits of the traverse movement. I decided not to use limit switches because it was more work and kept the installation job simple. It's easy to see when the mantlet has moved as far as it can, so the smart thing to do is to release the joystick! Much easier than fitting limit switches.
Despite what I said about the importance of a disassembly path, I used a lot of hot glue to make things work, and to do it quickly. Ideally, mechanisms like this should be made out of metal and parts screw-joined or soldered/welded. Servos should have housings for mounting. Nevertheless, servo tape is commonly used for mounting switches and servos, and hot glue is just another way of making a strong, ad-hoc, vibration-resistant join. It's amazingly versatile stuff.
Wanna Smoke? With a 2-inch speaker planned for installation, I had the room and the hull was pre-plumbed, so why not put in a smoker? I've been more receptive to the idea since acquiring my Elefant with its Super Smoker. I consider it a treat to see an occasional wisp of faux smoke in one of my Elefant video. I'd decided long ago not to bother with smokers, but maybe it was time to give 'em another chance?
Well... chance given, and the verdict is in: Uh... not for me! First problem was my entirely fault for not studying the Super Smoker instructions carefully and not paying heed to the line that says not to plug it into the MFU. Stupid me. Personally, I think a more informative warning would have been: "HEY U STUPID MF! The smoker heater draws GOBS of current and will TOAST circuits designed for the Heng Long or similar smokers!" Consider yourself warned.
Indeed it did. The Clark TK-22 has a pair of sockets devoted to smoker operation, and that's where I first decided to connect it. That's what got smoked, as in stinky and charred black on the component side.
Despite the ugly damage, everything else worked and I figured out that the heater circuit wanted to be powered directly by the 7.4 volt battery. Yep, it's a power hog and that's just common sense: Electrical heating is expensive in the real world. It draws lots of current, makes wires hot, etc. Even after the carnage, I still went through with it and installed the system on a 4-pole switch so it could be completely switched off, including proportional fan control from the motors. I tested it in the tank, and it was cool to see smoke streaming from the two tail pipes. However, I was appalled at how quickly it ate up my 4700 MaH battery so I declared it dead weight, a waste of space, and removed it. No hard feelings.
Yeah, it's a cool-looking effect, but one that I'd only find useful for showing off in a video. IMO, it's not worth the sacrifice of the tank's run time, and for the space it takes up, I'd rather install a bigger speaker. If you run it outdoors and there's any wind, you'll have a hard time telling that it's working. To top it off, it's a needy maintenance diva. Too little smoke juice and it won't run. Too much smoke juice and it won't run. Sheesh!
The Speaker This is another tale of near-failure and disaster, exacerbated by my stupidity and laziness. Hey, it's just a speaker! What could possibly go wrong with a speaker?
I have spare speakers, but enclosures are sort of a problem: I'm too lazy to make boxes for 'em, but they need something to keep the backside flapping from canceling out the frontside flapping. It makes a huge difference in the bass content/loudness. I'm not fussy about workmanship: I'll duct-tape 'em in butter tubs, or whatever's available if it improves the sound output. I have zero interest in studying ported speaker enclosure design.
This time I was going to use a small Tangband speaker that had pretty impressive output for its 2-inch diameter. I thought I'd be really clever and position the speaker right under one of the rear exhaust grills, secured to the underside of the hull. That way, the whole interior would act like a speaker enclosure! Damn clever, I thought.
While I was being clever, I decided to embed mounting bolts directly into the plastic hull underside by heating specially-ground screw heads until they melted and sank into the hull. Good solid flush mounting, stronger than using glue; the speaker could be easily mounted and removed by using a washer and nut, just like a guitar combo amp!
Problem was, I didn't notice how thin the hull was and how easily it melted/deformed the exterior. I was only generally aware of that issue; I thought I was being careful not to embed the screws too deep from the underside, but I couldn't see what was happening on the other side. No matter: Any deep was too deep, and I was facing a nasty rear deck cosmetic job after I'd tested the speaker. That is... if only I could test the speaker! When I tried to fit the upper deck onto the lower hull, the speaker was too far over and blocked the fit of the narrower lower hull. Arrrrghhh. You didn't think about this before??? All this carnage for nothing???
I put the speaker in part of a Heng Long speaker enclosure and sealed it in with some aluminum tape; basically the same as putting it in a butter tub with duct tape. (Later replaced by a bigger speaker in an official Bill Miller Barbeque tub.)
Servo-Controlled Laser Machine Gun I did this in my Elefant because it only had one machine gun, so there was no need to use a servo/channel to switch between them. Same story here.
Unlike an invisible IR beam, you can see a red laser dot, and it's gratifying to see it sweep across a wall as you twist a pot on the transmitter.
The hardest part is aligning the laser unit with the barrel so that the beam goes straight through the narrow channel and doesn't hit against the walls. When that happens, the dot isn't as bright and there's usually a halo off to the side.
The IR Battle System Realistically, I'm not going to be doing much tank battling (if I did, I'd use a tank with a rotating turret), but it seems like a waste not to make it battle capable. The Clark TK-22 board has a lot of programmable IR battle options, cool battle sounds, and if nothing else, having an IR receiver is necessary for programming the Clark board.
The problem: Where do you put the ugly IR receiver? In most tanks, you plug into a socket mounted under the cupola hatch. That way, the tank looks normal when it's not set up for IR battle, and you can usually put a half-figure in the hatch. I wanted to see how others have done it, but there aren't many pics on the Internet of 1/16 RC Jagdtigers with IR receivers. With the Jagdtiger, there's only one opening hatch on the turret top, and it's semi-circular, at an angle to the front. Although I saw pics of a 1/16 Jagdtiger with a Tamiya apple mounted in the hatch, it does appear to be mounted at a slight angle and it wasn't clear if it was done to a Matorro Jagdtiger (to fit in the hatch opening), and whether it was low enough to fit a figure on top. I did some test fitting with parts, and felt that it would be a challenging fit without some cutting and grinding. Sure, you could mod the apple to fit, but you might not want to do that if you share the receiver with other tanks.
I didn't see too many other options, so I made an external IR receiver mount from a sprocket. It's designed to be mounted on the rear deck using the engine hatch handle and lifting hooks. Wires go through the rear turret hatches to the board. It's not nearly as slick and convenient as a concealed system, but obviously, you'd only mount it for RC battling.
Similarly, there wasn't an obvious location for concealed mounting of the the IR emitter. If mounting an ugly receiver was okay, then why not the emitter? Without aesthetics and historical accuracy to worry about, the emitter could be mounted on the mantlet to be aimed with the barrel movements. For that matter, why not have fun with it? The apple looks like sci-fi technology, so why mount a simple tube for the IR diode? Howzabout a mantlet wart with an aiming laser?
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