"The Great Undertaking" -- GPM's Leopold Rail Gun

Discussion in 'Kit Reviews' started by sakrison, Nov 2, 2006.

  1. sakrison

    sakrison Member

    Part 6: The Loading Platform

    Building this assembly (Figs. 6.1 & 6.2) went smoothly, for the most part. The fit and coloring of the parts is excellent. I won’t describe the whole process, just things I changed or that gave me some difficulty.

    I started with the top, building up the platform and adding the side rails (parts 34b,c, & d). If I were doing it again, I’d leave the side rails off until much later. It’s very difficult to handle the assembly without bending them inward. I ended up re-gluing them late in the project. The base went together easily. I lined the inside walls of the base with black construction paper, since the platform is open at the top, and I have no clue what the inside is supposed to look like. The eight access doors on the sides are all the same size and part number, but for best results, spend a little extra time to match the camouflage patterns on the doors with those on the body. (Fig. 6.1)

    The rolling cradle that carries the shells to the breech has no coloring on the inside of its legs. It’s laminated to heavier stock and you’re expected to color that stock to blend in. I photocopied the parts (14-14d) and laminated the photocopies to the backside of the kit parts. The color match isn’t perfect but it’s very close and good enough.

    The instructions call for laminating the rolling table (part 14d) to heavier stock, then folding it. I was afraid that fold would be difficult so I cut the sides from the top, and glued the sidepieces to the underside of the top. I had to bend the legs out a little to get the wheels to ride on their tracks but it looks fine. In retrospect, I should have glued the top between the sides. That might have required trimming the top a bit to make the wheels fit the rails. Live and learn.

    The plans show railings and posts (parts s7, s8, & s9) to be made of wire(?). I made them out of 1/16” Evergreen plastic rod. For the curved corners on s7, I carefully bent the rod with a jeweler’s pliers, and then took the tension out of the bend by passing the piece carefully about an inch over a candle flame. (It took a couple of tries, and a couple of pieces of rod, to get it right.) I tapered the ends of the railings and posts with a flat file, and painted them with Testor's Model Master paints (2099-Afrika Grunbraun and 1723-Gunship Grey). I made divots in the platform with a 1/16” drill bit in a pin vise, and super-glued the railings and posts in place.

    The subassembly I worried most about was the two exhaust stacks. Built up from paper tubes with 45° bends, they looked too fragile. As it turned out, they went together well and are sturdy enough. I started by rolling all the parts. With small tubes like the exhaust pipes, I roll them tight on a piece of wire, and then use a toothpick or paintbrush handle to open up the tube. Rolling it tighter than the finished part will be, makes it easier to handle.

    Long tubes, like the long exhaust column, are always a challenge. (Maybe the ship modelers have some advice here.) I rolled this piece first around a 1/8” dowel, then around a smaller dowel, then around wire. I used a toothpick to tease it out to something like its finished shape and then I started at one end, gluing about ¼” at a time, and using a piece of the 16” rod as a backing for pressing the seam tight. The best advice I can give is: Be patient and work slowly. Rolling and gluing that one piece took somewhere between five and ten minutes, and the result was worth the time spent.

    According to the instruction drawings, the angled joints in the exhaust pipe are simply butted together. To make them stronger, I rolled a piece of newsprint around 1/32” wire and stuck one end in the bottom piece of the pipe. In Fig. 6.3, you can see the newspaper plug sticking out the top of the long piece of pipe. Then I slid the next part over the newsprint plug, aligned the two pieces, and touched the joint with brush-on superglue.

    I used Elmer's Brush-On "CrazyGlue." This stuff wicks into every crack, sets up fast, and dries flat (if you don't lay it on too thick). In about ten seconds, I had a good, strong, fairly rigid joint. (Fig. 6.4) I worked my way up the pipe, checking angles and alignment as I went. The newsprint plugs should be rolled loosely, so they can bend without flattening too much.

    The white ring around the pipe in Fig. 6.3 is a spacer/collar I made with my leather punch, to keep the shroud properly aligned with the pipe. With the largest punch, I punched halfway through a piece of 1mm cardstock. I switched to a smaller punch, centered it in the circle I'd just made, and punched all the way through. Then I went back to the large punch and punched out the "donut." (Getting a nice, even donut took several tries.)

    Newsprint is also very handy for repairs. If you cut something you didn’t want to cut (as I did when my steel straightedge slipped), glue a scrap of newsprint to the back of the cut to splice it back together. That creates a strong joint while adding very little thickness. I keep an old copy of TV Guide at the workbench, to supply all the newsprint I might need. (Choose one with a cover you like looking at; it will last you for about a gazillion years.)

    Fig. 6.5 shows the loading platform sitting on its railcar. I'm not going to glue it down; I want to be able break the finished model into subasseblies for transporting it to shows. I’ll add the crane’s cable and grapple and the artillery shells later on.

    So far this has been a wonderful kit with excellent fit and finish, and few and minor problems or difficulties. I've put a lot of hours in the kit already but they’ve been enjoyable hours. The result isn't a contest quality model, but I’m happy with it.

    The most intimidating thing about this kit is its size and the number of parts.
    I think any intermediate modeler with a few good kits under her or his belt would have the skills to build this one. It would also help to have a long workbench. And I still don’t know how or where I’m going to display the finished model. I can hang airplanes from the ceiling but this may need its own furniture!

    Next up is the other railcar. But first, I’m going to take a break from this project for a week or two, to build something a little smaller and simpler—like a cardboard box, or maybe snowflakes.

    No worries,

    "Results? Why, man, I have gotten a lot of results.
    I know several thousand things that won't work."
    -- Thomas A. Edison

    Attached Files:

  2. sakrison

    sakrison Member

    Still building

    Some of you may be wondering if I gave up on the Leopold--it's been a while since I updated this thread. Actually, I'm close to finished with the second rail car. But I have a book going to press at the end of January and I'm juggling 17 details at once to get it wrapped up and ready. The second rail car went together without any hitches and is looking as good as the first. I'll have pix and a few notable items before too long. . . if this book project doesn't kill me first.

    No worries (okay...one or two),
  3. rickstef

    rickstef Guest

    David, is this book we modelers might be interested in?

    seeing that alot of us are amateur historians and the like

  4. sakrison

    sakrison Member

    It's nonfiction, about three ongoing conservation projects: restoring trumpeter swans to the Midwest Flyway, restoring whooping cranes to the Eastern Flyway, and trying to save Russia's desperately threatened Siberian cranes. This is my second book; the first was an early photo history of the city I live in (birthplace of the Republican Party, tum-ta-daaa).

    The book will include illustrated instructions for making origami paper cranes.
    I hope that keeps this post from tripping the dreaded OFF TOPIC! alarm.

    No worries,
  5. rickstef

    rickstef Guest

    actually, once you mentioned origami cranes, you are perfectly still on topic

    I will look this book up

  6. cbg

    cbg Member


    I'm just curious. . .are you a member of Ducks Unlimited?

  7. sakrison

    sakrison Member

    Post #7: The Second Rail Car

    I finally finished this assembly. For the most part, the process was the same as the first rail car, with a few different details. The first car has a post that the gun pivots on. This car has a receiver--a socket on the rail car accepts a post on the bottom of the gun carriage. (See Figs. 7.4 & 7.5) I'd love to know why the German engineers designed it differently at each end of the carriage. Maybe because they could.

    I reinforced the receiver with strips of heavy card and collars wrapped around the tube that forms the socket. See Figs. 7.1 and 7.2. Since I intend to haul this model around to shows, I wanted the receiver to be good and sturdy.

    As I noted earlier, I used 1.5 mm paperboard from Lighthouse Models to build the frame and body of the first rail car. For the second rail car, I decided to use picture frame mat board, which is a little thicker but had the advantage of being colored (dark grey). Big mistake.

    Mat board is very, very dense compared to the "chipboard" on the backs of legal pads and Fly Model kits. I'd already laminated most of the parts of the underbody to mat board when I figured out what a pain working with mat board was going to be. I built the underbody with mat board, adjusting for the extra thickness (about .25mm) and my wrist and hand were sore for days, from digging my way through the stuff with a hobby knife. For the deck, I went back to 1.5 mm chipboard snitched from a Fly Model kit.

    I didn't have a piece of 1.5mm card long enough for the deck. I took two shorter pieces, trimmed one edge of each to be very straight and clean, and butt-glued the two together. I let them dry overnight, gave the joint a light sanding on both sides, and it worked just fine--a very strong joint. And once glued to the subframe, it's bullet-proof.

    I used basswood strips again for the decking--HO scale 6"x8" from Midwest, dyed with my alcohol-shoe dye weathering goop. It looks better and went much faster than fabricating all those deck timbers from paper parts.

    This car end has a brake pedestal and hand rail. See Fig. 7.3. (Isn't it amazing how the camera brings out all the little edges you thought you'd colored?) The hand rail looked delicate on paper. I reinforced it with some stripwood (basswood) glued inside the posts and crossbar.

    Fig. 7.4 shows the center of the car with the receiver pedestal and the associated mechanicals. I have no idea what they do but they look neat. That dark stain on the chain(?) housing happened when I was coloring the cut edge of the hole with a too-wet felt tip pen. It bled. Now I call it a grease stain from the machinery. Think, "Superdetailing."

    Fig. 7.4 also shows the modification I made to the steps, narrowing them to 5mm and staggering them, so the bottom one clears my custom-made brake hangers.

    Like the first rail car, this one took about a month of evenings. In my opinion, there's nothing here an intermediate modeler couldn't handle. Just take your time and test-fit a lot. Hurrying on a kit this size won't get you there any faster.

    The only really tiny parts in this kit (so far) are the 100 or so pinhead-sized bolt-heads (parts 1a & 1r) that supposedly go on the exposed ends of the journal bearing bolts and the brake hangers. Too small for my punch, each one would have to have been cut out by hand, edge-colored, and glued in place. I left them off; I suspect the kit designer was putting me on. If the little hole in the end of each bolt bothers you, touch it with a drop of glue, let it dry, then touch it up with paint. I didn't bother to do that, either. Did anyone notice? (Did I make you look?)

    Fig. 7.5 shows the whole rail car. It's about 15" long. The kit's artwork is superb and its ready-made weathering covers a lot of my sins. So far, the fit of the parts and the kit's assembly drawings are up to GPM's usual high standards.

    Next up is the hydraulic mechanism that elevates the gun, then the gun itself, and finally, the three-foot-long gun carriage. I'm working on a couple of sources for the large sheets of 1.5 mm chipboard I'll need for the carriage. I'll have a report on that later.

    I'm also starting another completely insane project that I'll build alongside this one, just for variety. But that's another story...

    No worries,

    "Results? Why, man, I have gotten a lot of results.
    I know several thousand things that won't work."
    -- Thomas A. Edison, Inventor

    Attached Files:

  8. Stev0

    Stev0 Active Member

    I soooooo want to build this now. The only thing is I dont have either the model or the room to put it in. :D
  9. sakrison

    sakrison Member

    I hear you. I'll have to hang a new shelf on the wall for this one. What I haven't figured out yet is where to build the gun carriage; I don't know if my alcove workbench is big enough to handle it. I might have to move to the dining room table for month or so, and that could be expensive--a dozen roses, a new dress, and dinner for two at a French restaurant.

    I love my hobbies!
  10. Fishcarver

    Fishcarver Active Member

    This is great work so far. I am enjoying following this post. Keep it up!! Good luck with the book!

    We have had some large flocks of Tundra Swans feeding down here on Vancouver Island. Some of the farmers do not like them very much, and they are reported to be a real PIA at the air base in Comox.

    Your Canadian friend,
  11. sakrison

    sakrison Member

    A Note on the Gunloading Hoist

    Back in Post #6, I described building the gunloading platform. I've added the following note to Post #6 but I'm posting it here, too, so nobody misses it.

    Take a look at Fig. 6.1 (attached here) and notice the angle of the hoist arm. With a shell hanging in the hoist, it's too low to position the table under the hoist. (I discovered this later, when I added the two cannon shells--one to the table, one to the hoist.)

    There's nothing inherently wrong with this but if I were going to do it again, I'd angle hoist about an inch higher off the deck.That would allow the table to be positioned at the gun breech, under the hoist, or anywhere in between.

    I glued the hoist together pretty well. I'm not sure I can change the angle without seriously messing it up. On the other hand...what's life without challenges?

    No worries,

    Attached Files:

  12. sakrison

    sakrison Member

    Shell Hoist

    I fixed it.

    Attached Files:

  13. eatcrow2

    eatcrow2 Member

    Beautiful work.. A pleasure following this thread.

  14. sakrison

    sakrison Member

    Post #8 Breech Assembly

    I'm back. After Three months of wrangling with a book deadline (the book is in print), I'm back to work on the GPM Leopold. Actually, I haven't been completely ignoring the Leopold; I just haven't had the time or energy to write about it.

    The breech and lower barrel assembly (see Fig.8-1) went together easily and mostly according to the instructions.
    I made one notable change in the assembly of the cradle that supports the breech and what I'm guessing are hydraulic tubes for raising the barrel. The cradle consists of 3 bulkheads (Pts 45 & 45a) and two side frames (Parts 46 P&L). The gun barrel rests on top of the cradle and three tubes pass through it. (Fig. 8-1).

    According to the assembly drawings, it appears that I was supposed to open holes in the bulkheads for the large tube but not for the two smaller tubes. I didn't open holes for any of them. I assembled the cradle. Then I assembled each section of the tubes (cutting disks for formers) and put the tubes in between (and around) the bulkheads section by section. The large tube is printed all in one piece, so I had to cut it into sections to do this. The results look much cleaner--no ragged edges of the hole around the big tube. All the tubes look welded in.

    One of the minor shortcomings I've noticed in this kit is that the holes that need to be opened up are not marked with the usual "w" for "cut out." You have to puzzle out each case based on the drawings. That's annoying and it has caused me a few problems--with wheels and axles on the rail cars, for example. One more reason to go slowly and plan each step carefully.

    The distance between the bulkheads was a bit more than advertised (or the tubes were a bit shorter than advertised) and I cut disks (spacers) just slightly larger than the tubes to fill out the needed length. (Fig. 8-2) You could just leave a little extra on the end of each tube section when you cut it out, then trim to fit and color the extra length.

    Figure 8-3 shows the breech attached to the barrel and cradle; Fig. 8-4 shows the underside of this assembly. You can see that it's big. Those are 1" squares on the cutting mat.I'll add the rest of the barrel at the end of the project, to avoid any bumps and bruises.

    Figure 8-5 shows a minor problem I've run into. The kit includes a lot of bolt heads to be cut from 1mm card. That's fine except that, with handling, the 1mm card de-laminates. leaving me with 0.5mm-thick bolt heads the color of cardboard. I say, "with handling." Sometimes they come apart even before I've glued them to the model. I haven't worked out a solution yet. Maybe the tank modelers out there--who deal with bolts and rivets more often than I do--have some ideas.

    Next, the gun-carriage side frames.

    No worries,

    Attached Files:

  15. eatcrow2

    eatcrow2 Member

    What I've done on small parts where I'm worried about de-laminating, is either soak it in Future or CA (mostly Future).. When dry I usually get good results..
  16. Clashster

    Clashster Member

    Looking great, David! I especially like the last picture... I have felt that many times! So, my sympathies are with you! Looking forward to the progress!

  17. ikarus

    ikarus New Member

    WOW, awesome.

    Do you think it is possible to scale the drawings down to 1:87 (HO scale) or even 1:160 (N scale)? I would like to build a model for my layout starting from the drawings. I assume one would have to skip some details for such an endeavor.
  18. sakrison

    sakrison Member

    I'm sure you could scale it down but you'd need a big scanner--the kit pages are huge and there are a lot of them.

    By the way, the project got put on hold last winter when I ran into a problem with the main gun carriage--my problem, not the kit's. I've been puzzling out a way to solve it and I hope to resume the build this summer. Stay tuned.
  19. milenio3

    milenio3 Active Member

    Hello, David. Are you still undergoing the Leopold build?
  20. sakrison

    sakrison Member

    I intend to. I have to disassemble and rebuild the main gun carriage, or at least one side of it. Then I would really like to finish the project--this winter, perhaps. When I do pick it up again, I'll resume this thread.

    You certainly got me thinking about it.

    Wish me luck.

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