Baubericht - 155 mm M 40 GMC

Build

The kit's instructions start with the gun parts; this sprue has been taken from the "Long Tom" kit. Now during the extreme gestation period of the kit, AFV Club might've heard that the gun tube of their M 59 kit was recognized as short and fat ? the rear (plastic) half plus breech is much more correct for the 8 in howitzer than for the 155 mm gun. (Grafting the howitzer tube onto the kit to build an M 43 isn't a way out, either, as this had

standing projo stowage racks, just like the T 38 and T 89 ? which, strictly speaking, also prohibits using the "Zebra mission" decals on the contents of this box.)

Kurt Laughlin thankfully has measured both tubes and published his findings:
(http://www.network54.com/Forum/47208/thread/1313718381/Accurate+drawing+of+155mm+Long+Tom%2C+particularly+the+barrel- ), so with this information, I inserted styrene shims into the different segments of the tube and lengthened the slide rails underneath correspondingly. A lathe-armed modeling friend drilled out the aluminum front part for me so that a drinking straw could be inserted as a gun bore. And yes, I know that all this didn't cure the wrong diameter ? but I'm convinced that the thing LOOKS slimmer now, ok?

Meanwhile, click2detail has issued a 3D-printed version.

For me, the breech also needed some work. So the kit gives a two-part locking screw and an obturator ? but what'll the thing screw into in the empty breech, huh? A small plastic ball pen had its screw joint cut off and segmented. Four of these segments were strongly sanded on their outsides before being cemented into the breech, while four others were sanded less and cemented next to them. The kit's screw was segmented similarly and cemented back together to fit the breech's new pattern. At 3 o'clock, a notch was filed into the breech ring to allow the raised screw part to pass.

So now the breech would look OK in the open position ? almost. After all, the whole thing works by turning the "screw" on the breech block into the "nut" in the breech ring, and this is brought about by rotation of the breech block on its carrier plate, which in its turn (no pun intended) is moved by the roller mounted to it hitting the cam on the breech rear. Thus, on an open breech this roller would have to point at about 10 o'clock, not at 12 as in the kit part. Which required a new carrier plate and roller, and while I was at it, I added a tiny pin in the plate that would engage a curved slot in the carrier to stop the rotation in the right places.

Which left the opening lever to be installed by drilling a hole through it and into the carrier for a piece of stretched sprue with a molten end; note that the lever travels way more than the kit's instructions indicate. Drilling out the support cylinder for a new cylinder rod made the breech fully operable after everything was joined with stretched sprue. (Now here's a confession: Although the breech block fits into the breech, it does not do so while on the carrier the tolerances here are too tight. Instead, the block sits loosely on a pin that doubles as an axle for the carrier plate.) The hollow at the lower breech front was filled. Three copper wire hooks for pulling the tube from the cradle and back into battery completed work on this subassembly.

Next came the cradle. It went together fine, but the variable recoil cylinder on its left (the higher the angle of fire, the shorter the recoil travel) had to be replaced on my model with an operable one from styrene tubing and square and round rod easy, just as mounting its activating rod movably.

The trunnion supports offered very nice hinges for the equilibrators, but needed the addition of the "threaded" rods on which these hinges can be raised and lowered to regulate the equilibrators' work. These were "continued" with replacement hexhead nuts at their lower ends. The difference in the diameters of the equilibrator cylinders and their rods was too big in my eyes, so I drilled out the cylinders and replaced the rods with thicker ones.

The stowage clamps for the projectile carrying/loading rack on top of the trunnion supports looked cool in photos, so I constructed them from styrene strips and slices of stretched tubing operating, of course. The rack itself received handle covers from wire insulation. On the right hand gun shield, I replaced the gunner's quadrant stowage with a contraption from thin sheet styrene and an onionskin paper strap; the top part of the cable next to it was replaced with one from stretched black vinyl sprue, which I also used for the continuation from the shield to the trunnion support front. On the front side of this shield, the tiedown eyes and two angles at the bottom were replaced with styrene items.

A final detail on the gun and cradle was the panoramic telescope; this was transported in the box on the lower left gun shield. So, I cut the kit part in half and drilled out the lower part, which then also received an imitation telescope lock. The upper part was lengthened so that it can be inserted when my gun is to be shown in firing position. On the opposite side, the quadrant mount (C 19) had its positioning pin lengthened so that it could be cemented to the trunnion and now moves with the cradle.

One thing that can already be seen in a photo in the kit's instructions is the rear travel bracing. Where the Long Tom has its "A" brace locking the tube's breech end, on the M 40/43 there are two movable eyes on the elevation quadrant to which two adjustable rods are connected that go into eyes on the sponsons. No big deal to add the eyes on the cradle, but the elevation gear box on the right trunnion support's inside had to be carved out to let this addition pass. I bent the rods and their fixing points on the sponsons from copper wire and made the hexagonal turnbuckles from a heat stretched pencil-shaped ball pen. When I tried to find the locations on the sponsons, Toadman's Tank Pictures showed that the kit had the locating circles for the heavy hull lifting eyes in the wrong places. They were sanded off and the travel brace eyes installed as per the photos of the prototype. (Today, however, I'm doubtful that the way I built these braces might only be correct for an M 43, with thinner braces visible on the M 40 shown at primeportal.)

To test fit all this, the gun base had to be placed into the hull, together with the bulkhead and the fighting compartment floor parts. And once again, the kit didn't look like the prototype photos: The front half of the floor was level with the sponsons, and the gun base was only slightly higher not good. I found it necessary to raise the gun base some 2.5 mm and to lower the front part of the floor 2 mm. (The latter also entailed reducing the separate stowage box block's height.)

Determining the correct mounting points for the travel braces showed that a strip of almost 2 mm at the sides of the upper floor part is non-folding on the prototype, so I inscribed another separation line there and removed the non-skid structure outside of it. The front "stowage compartment lids" in the lower half are reversed they should be hinged at the floor step and have their lifting handles right opposite those of the rear plates. And the center section of this floor area should be a continuous plate from step thru the rear, as this is the exhaust tube cover, fastened with slot screws. Unfortunately, the Eduard PE set faithfully repeats all these inaccuracies, so I just added "hinges" for the rearmost plates. Small square holes were cut into the vertical wall of the floor part and into the lateral braces for later addition of taillight wire conduits from thin solder.

The stowage boxes that are carried in this rear floor area should be separated from each other unless they are to be stowed here, and get tread plate pattern all around their tops, as these lids were bent from that material again, no help from the Eduard set here (but width problems for me, because of the wire conduits). Fortunately, all photos showed the tread pattern on these boxes to be finer than that of the floor plates, so Archer's tread pattern decal could be used after the depressions for the handles had been filled, so new handles from wire with stretched tube mounts could be mounted on top of the tread pattern. (For those who want to show these boxes open: there are two carrying handles on the inside, at the narrow ends.) I found it useful to give the decals a layer of Future before using them, as the raised detail tended to peel off at the tight bends.

To remain a little longer in the gun area: As for the ammunition stowage on the hull sides, I really can't imagine why AFV Club molded the sprue attachment points on the tiny hinges for the locker lids (E 6) in different spots guess which version is easier to clean up. Another detail to be added to these lockers are some parts that look like wing nuts in the kit (E 10), but must have some connection to "universal rifle racks", as that's what's stenciled next to them on the lower rear trunnion supports (where the kit doesn't provide for them). These are where the Eduard set really will help. I bent mine from aluminum strips and added molten ends of stretched sprue and small globs of white glue to represent nuts and bolts.

The crew seats were detailed with onionksin paper belts and separate handles for folding up, plus mounting plate arrester bolts on the side walls. The prototype had another two seats, to be mounted to the folding rear platform by inserting two "nailheads" and an arrester bolt; six holes for these were drilled into the platform but I managed to resist AMS's urge to build the seats. (Eduard offers the two mounting plates; but who would leave such stumbling blocks on the platform after removing the seats?)

Further construction of the hull now required cementing on the engine deck / glacis plate, after replacing the braces below its PE grilles with thinner ones from styrene sheet and adding several tiedown eyes and handles to these openings. The kit's weld beads around this large part were incomplete: As even the box top shows, the bottom part of the glacis is a separate slab of steel that is thicker than the rest. This was replicated by cementing on "weld beads" from stretched sprue, softened with liquid cement and dabbed with a knife. The same was added to the engine deck's sides and rear, outside of the folding section. While I was at it, I also added such beads to the front and rear bulkheads of the fighting compartment. The engine deck sides received four tiny drain holes drilled in, 5 mm away from front and rear. Above the rear holes, styrene strips were cemented vertically to the side walls. Two more of these were cemented at the engine deck centerline, and tiedowns in the middle between them; these represent the tarpaulin bow stowage (tops to the front).

The hull, by the way, is rolled steel and depicted correctly smooth in the kit, except for the differential housing which is cast steel on the prototype and had to be roughened by scraping it adze-fashion with a knife blade to simulate the trowel strokes in its sand casting form; I'm afraid I slightly exaggerated this. Parts fit wasn't ideal here, so I had to shim a little and still had a slight gap where the glacis comes down. Holes were drilled into the front and rear brackets for towing shackles (not mentioned in the instructions, but present on sprue D), and at the front, mounting steps from sheet aluminum strips were added, as was the "comb device". More fit problems occurred on the spade: The blade has grooves for the main braces to settle into, but they're not H-shaped as the braces are, and the radius of the brace cutouts doesn't really match that of the blade. Lots of tube cement and rigorous clamping settled that. To be free as to the time of mounting the spade, I cut off the hinge pins on parts B 22 and drilled through them, so I could mount the hinges now and add the spade later with styrene rod pins.

The kit's rear platform isn't designed to be movable, which I regarded as a challenge. Pieces of stretched styrene tubing replaced the kit hinge representations on the hull, while the hinge parts on the platform were substituted by PE "rings on sticks" from the model railroad range. After the parts on the hull had been ripped apart by a falling ramp, I supported their replacements with loops drilled from very fine wire that were superglued into holes next to them (but forgot to take a photo).

A movable platform also required a slight relocation of the "rollers" on the spade, so they'd push up the platform. The platform stays (parts B 31), however, seem to have been copied after a vehicle in a museum, as I haven't seen them on any other M 40/43 and can't figure how they should be stowed on a gun in active service, so I left them and their fixing parts off and removed the fixing point on the winch. Another requirement of a movable platform were functional arresters for its travel position, so parts A 38/39 had their "locking pins" removed and the rest drilled through; the corresponding parts on the platform were replaced by styrene strip. New locking pins were bent from copper wire. To keep the sliding extension's brace from flapping around, there are two guide horns on the extension slide braces that were added from styrene strip. I also added two braces to the platform underside.

The sliding extension beneath the platform presented some more challenges. First of all, two very prominent and very ugly push-out blobs had to be removed from the fine latticework. Careful drilling, cutting, and sanding accomplished this. Which was followed by many more hours of widening the spaces in the grillwork to make it look as thin from the top as it did from below molding fine plastic gratework just can't be done without one side coming out thicker than the other. And in spite of all the time I'd spent handling this part it wasn't until I was going to cement two small rectangles with tiedown eyes to its underside that I noticed another small inaccuracy: The ribs going from left to right should be the protruding ones, with the longitudinal/vertical ones being less deep. Can't be changed, except by a completely new PE part (which I wouldn't want to have to put together!).

Lastly, the platform extension support brace had to be made operable. Seemed easy enough: cut down the fake hinges on the extension, cut a slot into which pieces of stretched sprue would fit that were cemented to the support's upper ends, seal the slots with strips of thin sheet styrene. It worked, too except that the folded brace didn't lie flat until I discovered that the rib that bears the hinge on the left was higher than all the others inside the outer frame I've no idea why, but everything fit nicely after I'd ground this down to the level of the others. The spade winch had its brake lever cut off the drum and a "brake band" from onionskin paper added to it. Thus, the drum became rotating. All the rope guide rollers were made functional by sanding off the "covers" where the grooves had to be completed (deeply) around the sheaves and then covering these with strips of very thin sheet styrene. This allowed strong black linen (low-fuzz !) sewing thread to be used instead of the kit-supplied string as a spade lifting rope. Which led to the next problem: the stowing hooks have to fit into their arresters (A 2/3), but they aren't movable. I came up with the idea of drilling out the kit's arresting rods and replacing them with separate pins that I can insert and remove as needed.

The winch crank presented another detailing possibility: As its handle is rather long, it would be in the way whenever not in use, so the prototype's designers made the crank removable, to be stowed on the rear wall. Two clamps for the handle are mounted right below the top, with the crank arm hanging "inside" the winch body. The clamps could be duplicated with two narrow brass strips. The crank was cut off its "axle", to which then a ring of suitable styrene tubing was cemented that had two segments excised before being topped with another ring. The corresponding kit representations were sanded off the crank, which can now be inserted or taken out to be stowed (but will NOT drive the winch!). A "locking screw" on the segmented ring completed this madness. The clear tail light bodies were painted like this: the one on the left, upper half red, lower half black, followed by an olive drab top coat. Same procedure for the right one, but without red, and taking great care when painting the face so that, contrary to the instructions, only a small slit remained in the upper oval. Unfortunately, the "glass" faces of both taillights had notable sinkmarks; on the larger left part, this could be remedied with Micro Krystal Clear. These lights weren't just bolted to the rear wall, but sat on sheet metal angles and had a round "connector" behind that. Sheet aluminum and styrene tubing to the rescue, with 0.75 mm solder wire to make the connection to the driving compartment. Part A 37 is the socket for trailer lights. It needed a blob of 5 minute epoxy to produce its domed lid, with a stretched sprue hinge and a piece of thin sheet styrene as a lid handle.

The front gun travel brace received an operating top clamp by drilling through the hinge and adding a perforated piece of sheet to the lower end of the locking screw. The slot for arresting hook A 31 was filled with a sliver of thinner styrene, while the hook itself was cut apart and rejoined to be operable. The "hinge bolts" at the brace's bottom were also drilled out for stretched sprue replacements. Prototype photos showed the space between these lower hinges A 25/26 filled, and weld beads all around, so I added these details. More attentive modelers than I would have noticed that the instructions contain a mistake here: The clamp's hinge has to be on the left in the direction of fire, the brace's "feet" have to point to the lower rear! As for the lateral brace stays A 27 and their fixings A 6/7 and A 21/28, they're rather fiddly, so do yourself a favor to assemble these lower parts before you cement A 6/7 to the glacis. Also, the fit of A 27 to A 21 is rather loose, so you might want to insert some thin tubing first. And while you're in the area, check your references for the position of the front hull lifting eyes L 13 ? some vehicles had these further out, the very early ones had none at all. The kit headlight brush guards were thinned down and received little pieces of stretched tubing to represent the stowage tubes for plugs that sealed the holes which stowed headlights would leave. These plugs were sanded from stretched sprue with molten ends and secured with "chains" of rubber filament from black panty hose. This material was also used on all securing bolts and handles. The lamps were drilled out to receive aluminum foil reflectors and thermo-formed acetate lenses. External fire extinguisher release cover L 7 had its corners rounded strongly.

Scratch-built tow cable retainers (each from three strips of styrene, plus aluminum clamps and ABER wing nuts, all joined operably with stretched sprue hinge pins) were added to the glacis and the transmission cover. Note that a second rope could be stowed behind the drivers' cupolas, with a sheet metal retainer behind the vent cover. The rope itself was made from an annealed steel wire cable (from a bike brake cable) added to the kit rope ends. The latter brought me to sprue "D", and I went to install the tools next. When the locating pins on some of them didn't fit into the provided holes, I took another look and found that my kit had a "D" sprue from AFV Club's M 10 kit they only differ in the position and contents of the lower appendix. As cutting off locating pins was no big deal, the only extra work would be bending my own starter crank from wire. Adding separate stowage points from sheet styrene and aluminum was in part necessary after I'd lost the small shovel to tweezer launch (and else due to AMS). I used the kit's PE parts for the spare track stowage, but cut off the lateral "ears" of the hold-down bars, replacing them with a "u" from an aluminum strip plus wire locking handle, as well as adding the upper mounting eye from stretched sprue.

Tiedown eyes all around the hull were replaced with stretched sprue ones, and the tarpaulin bow brackets on the fighting compartment corners with ones from sheet aluminum. This material was also used to bend the two "hooks" that would hold a foul weather hood on the driver's cupola. Another detail to be added to both cupolas would be the means to arrest their hatches in the open position and there were two systems: One used a springloaded pin going up into a hole on the right-hand hinge, the other used a hook on the left-hand hinge that went into a hollow protrusion on the cupola base rear. As the latter offered more visual interest, AMS forced me to install this variant. To correctly close the hatches, it was necessary to remove a ridge between the two hinges on the transparent lower part.

Now it was time to tackle the suspension. I had read that the small return roller mounts collided with the bogie mounting plates below them, and found this to be true. The remedy was easy: I just cut the locating pins on the hull into a shape like the mounts themselves, i.e. with a flat bottom. That allowed correct placement above the installed bogie mounts.

To put my model into the Korean War time frame, I used AFV Club's T 80 SLT set, which contains 768 parts on eight sprues impressive, to put it mildly, daunting being another word that came to mind. Every link comes with its guide "bulb" and two end connectors, the latter being molded to the outsides of the sprue so that a number of them can be installed at the same time. The danger of shipping damages is minimized by pins and holes in the four corners of the sprues so that you get two neat stacks of four in separate bags. The pushout marks on the insides of these links are inevitable in molding plastic, but thankfully, they are standing proud. I ground them off with a sanding disc in my motor tool while everything was still on the sprues. Separating the links from the sprues proved difficult because of their delicacy cutting one connection with a sprue cutter led to a twist in the link that broke one or both track pins in the center. This led me to razor-saw through one connection on all links and then using the cutter on the other. Two short file strokes per link finished preparatory work.

The hollow guide bulbs are incredibly well molded with all their details, which results in rather complicated connections to the sprue that require some elaborate work to get them off. (By the way: all track work is best done over an empty kit box to minimize losses by tweezer launch and other hazards looming when working with parts this size.) The guide bulbs have to be inserted into the links, with their "C"-shaped cutouts around the center section of the track pins. As this has to be done without cement, fit between these parts is rather well, let's say "exact": getting the things between the halves of the links seems easy, but it's just as easy to leave them sticking out just a fraction of a millimeter too much, which will later prevent the end connectors from fitting. And it is even easier to break the thin track pins while trying to insert the bulbs correctly. (In hindsight, I think a lateral file stroke or two would've made the bulbs slide in more easily.)

After the first few casualties, I resorted to placing the links on the bottom of my box and backing them with a strip of wood while I pushed in the bulb. The next problem arose when it came to installing the end connectors, as the links tended to rear up when pushed together to obtain the required distances. With my brass calipers on top of them, they could be held down so that, with some exercise (and you get plenty of that!), I was able to install as many as eight connectors at a time. To keep the results movable, I touched thin liquid cement to the end connectors on one end only, trapping the next link between them without cement. (A word of warning here: I strongly recommend to use a somewhat thicker styrene cement -or super glue- that doesn't attack the track pins as strongly.) Cutting the sprues off these assemblies wasn't quite as easy as the drawings on the box suggest, once again because of the track pins' fragility. To sum it up, the tracks were tedious work, but I find the results worth it.

When mounting them, I found the track-tensioning idlers' axles (A 42) to fit very loosely in their mounting holes, so I inserted "pipes" from rolled very thin styrene to shrink the diameters. AMS also forced me to cut off the small hexheads from these axles, replacing them

Update

After I had finally noticed that, following AFV Club's instructions, I had mounted the front gun brace the wrong way around, I of course wanted to correct that. In the meantime, Tamiya had released their M40 kit and a turned aluminum replacement gun tube; this should offer an opportunity for another correction.

Right away, I could congratulate myself to having drilled through the brace's hinges and used stretched sprue hinge pins secured only by a coat of paint. These could now be pushed out to reverse the brace. For a correct look, this required the relocation of the recess for the brace arrester hook, easily done by carving out the existing one on the former back side and replacing it it with a piece of thin styrene on the other side.

That might've been it, hadn't I seen all those pictures showing vehicles with somewhat different fixings of the lateral braces. These seemed easy enough to construct and would set my model apart a little more. First, the uppermost part of the brace's top plate was built up to the thickness of the frame using styrene strips on front and rear, with holes in the corners and three "nuts" in the middle. The kit-supplied lateral support hinges were replaced with sheet ones mounted higher up. Next, each side received two perforated pieces of strip styrene with rounded upper ends and two perforated sheet squares inserted between their lower ends. The lateral brace rods were shortened correspondingly (fortunately, I had broken the kit's plastic ones during the original build and replaced them with wire, so this was rather easy to do). Finally, the moving part of the clamp had to have its outside radius cut down and two crescents from thin sheet cemented on. And that was it: stretched sprue hinge pins all over brought everything together.

Now to the gun tube. As already mentioned in the original article, click2detail offers a 3D-printed example; it has integrated slide rails and breech. That it's way too long wouldn't be a big problem, but the "steps" from the printing process are very "high", and because of the slide rails appear impossible to be sufficiently sanded away. The Tamiya replacement part from turned aluminum comes with ten very nice turned brass shells and a BIG problem for use on the AFV kit: the metal tube has recesses for the "bands" that join the slide rails to it, so these bands plus connection to the slide rails would have to be scratchbuilt. The relatively easy way out is a castoff of the corresponding Tamiya parts, provided you or a friend have that kit. As I had got mine for a very good price, I took these plastic parts, including the tube halves, and saved the cast copy for the turned tube on the Tamiya model.

This, however, only solved the problem with the tube's diameter, leaving the breech still too fat. Having put so much work into it, I didn't want to replace it with a scratchbuilt closed version and found this way to recycle it:

Anticipating that some fine day I would find a way to correct or replace the tube, I had mounted the breech with white glue and so could easily remove it. The hinge points for the breechblock carrier were removed, as was the anchor point for the small hydraulic cylinder on top. The bottom part with the nuts for the recoil cylinder rods and the wire hook I had added were carefully cut off. With a razor saw, I then cut through the outer tube of the breech ring, about 1mm away from its rear, thus creating a "mushroom" consisting of the inner breech tube and the rear "ring plate". Taking the measurements from the corresponding Tamiya part, I found a plastic tube (from a cosmetic instrument of my wife, I think) that just needed a wrap of styrene sheet added with superglue to give it the correct outer diameter of 14 mm. The ring plate was thinned down and then cemented to the new outer tube. It could then be trimmed down to the correct diameter and the whole thing was cut to a length of, again, 14 mm.

The breechblock carrier was used to find out the mounting places for its new hinges, and the "bottom part" was installed again. For the breech block hydraulic cylinder, the new anchor point was scratchbuilt and cemented to the rearmost of the bands around the tube. Glueing the drawback-hook back into place finished this surgery. The tube had a drinking straw inserted as "bore" plus some leftover PE rifling at the muzzle end. And when I mounted it, I found that, of course, now the diameter of the clamp was too wide, so a "liner" from an Evergreen strip of 0,5 x 2mm was cemented in and painted black with a little Dark Earth added. – On the AFV kit cradle, the distance between the guide rails had to be increased about 0.5mm to let the Tamiya slide pass.

And now at long last I have an M40 with even a correct gun tube and breech.