German WW2 80cm Railway gun "Dora", with corrections

Bart Goesaert
Interested in this one, and what you will do with it... have the kit in stash, but think it will be an OOB build for me eventually.. Always thought the kit had less flaws then the Soar Art begemoth...

Treehugger
You would be wise to try the simple changes shown on Nigel's Modeling Bench channel on youtube. Shortening the barrel at least seems like a must.

Nigel has videos on both the 1:72 and 1:35 kit. 🙂

I don't agree with everything he suggests, but it really good input.
Below is one of the videos on the 1:35 kit. He also has videos on the 1:72 one.
Youtube Video

Treehugger
Re. image 7 in my album, showing a second area on the barrel having a silvery color to it. A mystery of mine solved I think:

Looking at photos, the long barrel was built in two or more pieces, that meant that the outer end of the barrel was fed through the bottom part of the barrel, and so I guess, the other silvery area on the barrel was just there for sliding through the very end of the first base part of the barrel. 🙂

I had been wondering if maybe that second silvery area on the barrel was recoiling with each firing of the cannon, but photos seem to not show that, so instead I guess that other silvery area is just meant to slide through the base part of the barrel.

Note: I guess that would mean, that this part of the barrel, the silvery part, would be cylindrical, otherwise, with a cone shape, the part obviously wouldn't be able to pass through the base part of the barrel. 🙂 The kit part with this other shiny area on the barrel looks like it is conical in shape, which I will change I think, to become cylindrical.

Dave Flitton
Watching this one too

Treehugger
Aaah. I think I figured out why the pairs of vertical beams at the center looks wider. That was a real head scratcher for a long time.

In image 31, I have sketched out how I think the T beams have been arranged, based on photos.

Treehugger
I am really really happy with the result so far, trying to draw the detailing for this railway cannon. 🙂

I am sure there are plenty of minor flaws on the kit yet to be discovered, but I will try to focus on the basic shapes and be happy with trying to fix the basic stuff.

I have great confidence that I can continue with this when I start changing the plastic. Just have to fix a few more minor details on the sides.

Treehugger
Image 42: Aha. I finally figured it out.

Wim van der Luijt
the phrase " if it looks right, it is right" will never catch on in your part of the universe, will it? 😉 I'm interested to see how you pull this off..count me in!

Treehugger
I guess the drawing don't provide much entertainment, but there are some interesting patterns there that aren't found on the kit. Occasionally I get to write some comment on the drawing.

All the drawings are work in progress, and might be changed. I try to keep in mind a few variables, so once I figure out something, I can tweak things to make everything fit together better. 🙂

I noticed today that the breechblock is imo filling the cavity of the construction behind it, the cavity is probably there for the recoil action. Photo show the breechblock clearly further ahead, and not filling the hole in the floor on top (covered by some huge tray). 🙂

I will have to re-draw stuff, after adjusting the spacing between the many hand wheels, by one pixel, however this is a minor inconvenience.

Looking at photos, they seem to show that the main shape, that is tall, is collapsable, folding back into itself. The many hand wheels are probably there as numerous pins that keep the elevated structure in place when erect.

Ingo F
Mate, thats hell lot of work you got before you. 👍

Holger Kranich
What a hell lot of work! 😄

Treehugger
It is some work but not as much as it perhaps looks like. 🙂 My evaluation of it all anyway. The good thing is that, several of the larger pieces, can be made individually, or not necessarily at the same time, so one can move from one problem onto the next without perpetual head scratching.

Treehugger
Photo 51: Well shit. So, I have come to the conclusion that all the wheels that comes with the kit is probably too big in diameter.

So, the 18mm Ø wheels should be more like 15,5 mm Ø as I see it. A different kit in 1:72 scale had its wheels in 14mm Ø btw, which alerted me to things possibly being out of scale still. A lot of work went into checking the wheel size, and I used this evening to look again at the wheels at the carriages, and I think I've made an improvement. Though, this means, all the wheels have to be scratch built, or, probably 3D printed, which is easy enough.

Full image here: ibb.co/S7BMZTj (I have since fixed a small error)

Treehugger
Photo 52: After looking at this again, it seems to me that the wheels are even really smaller than I thought at first. I went from 180mm kit size, to 155mm, to 145mm. Probably still a little too big, but this looks ok to me. I will probably 3D print the wheels and some detail, and using 2mm steel rod for the wheels with casing around the steel rod to make it look 4mm in diameter.

ibb.co/pzCSJf9 (same image, but looking better in full resolution)
ibb.co/4tZ8mf5 (shows more, zoomed out a bit, also updated and corrected)

Treehugger
So, it is clear now to me, that my corrected shape for the main body (the two halves) are 15mm longer than the kit part. No problem. Unlikely to be 100% accurate, but those 15mm extra was needed.

It is also clear that the two halves ought to be 5mm taller than the kit parts, also, something I deem necessary.

I don't trust sketchy drawings, nor infomation found in a book even, so I am happily making the needed changes to make my drawing look like what I see on photos. Unfortunately, it is just too difficult to try make good evaluations to the scale of things based on photos that are obviously distorted, I can approximate, but I can't pinpoint the exact lengths without having good photos from the side and without perspective distortions with the lens on the camera (or any other scaling issues based on handling the photos afterwards).

Update: Sigh, somehow the wrong layer in GIMP was on, and my "updated and corrected" screenshot just above is ofc wrong. :| Problem is fixed, and also, solved this other problem I noticed this evening, another detail. 🙂

Treehugger
Discovery: The two big halves of the whole thing, are connected at the center with movable arms on front and end. The kit have the arms horizontal, when the arms should bend up and down. Easily fixed. 🙂 Things looking good, though it would have been nice to not also have to fix this part as well.

ibb.co/5kvChng (Photo and outlines, showing the part in question.)

It seems to me that a lot of the steel plating is about one inch thick (2,54 cm), which equal to 0.10" styrene strips. 🙂 I would also need 0.3 mm strip styrene elsewhere, but haven't found any.

Treehugger
Image 53: What a tight fit. I think I nailed it. The kit parts kan be used, but I will have to make some new stuff with styrene. As you can imagine, the kit parts aren't accurate. 😄

ibb.co/GcMRQxg (re-uploaded, cleaned up, a more clear image as image 53)

Well it is a work-in-progress. The "too short" comment in the image, also failes to point out that the beam is also supposed to be drawn diagonally. I can deal with those intermittent aweful projection drawing skills later.

Treehugger
Image 54: Ooh, more work, now with the depth of it all. Well ahead on drawing the two large connector pieces, but probably have to be re-drawn, now that I have to look at the width of the whole thing.

ibb.co/HnRZ9KB (a more clear image of initial sketch of the carrages. I have to figure out the width of the carriage, before I can evaluate the total width of the railway cannon.

I used some slightly larger metal (toy train) rails for my project, probably a good idea to select some metal rails that are true to scale. Mine rails are 3.5 mm tall, and 3 mm wide. At least things look a whole lot better with more proper scale to things.

Treehugger
I made good progess on the details for the connector parts, but the width between the two large main bodies is wrong, partly an earlier mistake of mine, but also something else that I have to figure out.

ibb.co/6RGbsvT (shows projection drawing, well, whatever I managed to draw up anyway)

I think it is really fun to do this detective work. At least, if I finish, maybe I'll end up with the only "decent" looking Dora model, lol.

Guess what, the numerious ground pieces for the rail track in the kit box, can't use them I think, too widespacing between the two tracks it looks like, might as well rebuild it all. 😠 At least I have the metal rails now ready. Edit: It looks like the kit has standard gauge when I measure, however, the king size kit rails makes this possible, so with normal rails, the gauge is maybe 1mm too wide on the model.

Treehugger
Image 55: I changed my mind, I think I can still use the kit parts for the ground, by sawing the pieces apart, and removing the excess, should be fairly easy. Also I think the metal rails look ok on the plastic.

Treehugger
Image 56: This is my first good overall look at what I think is the correct proportions re. the depth of the model. Is clearly more narrow than the kit itself.

ibb.co/kg1Hmvx (png image, same as image 56 but unscaled and not distorted)

Treehugger
I am confident I have the side view nailed down, but now the challenge is to make that work with also the depth of it all. Fun, but also a little scary now. 😄

Bryn Crandell
Pulling a seat on the couch. This will be a massive build.

Treehugger
I am currently checking to see if the barrel parts at least can be used, it sort of looks like a good fit, but I haven't checked 100% of it. Seems to me, maybe, that the cannon barrel is properly sized, fitting nicely into my new top deck which is 14,8 mm more narrow now (7,4 mm narrow on each side).

As pointed out by some other guy some time ago, the rear part of the cannon is missing a thicker ring segment just before the breech area.

Treehugger
I don't know what the two types of parts are used for. Can't find them in the manual: H34 & H35 (two round thingies)

Update: The cannon barrel stuff is too wide for my idea of accurate width, so I have to make the width 2mm wider than I wanted.

Treehugger
Latest discovery: I think the kit parts for the big breech block are too large. 🙂 Fun discovery if I am right, because that solves some other fit issue, and at this point, rebuilding the breech block is eez. 😄

Treehugger
Image 61: ibb.co/wYNN4GG (high-res) I have managed to shorten some stuff on the cannon, that either should have been shortened, or can be shortened without looking weird. Current width betwen the two big halves = 39,9 mm. (Down from 53 mm, also makes carriages have a smaller gap between them as seen in photos.) Ideally the gap should have been 5mm smaller, but for all I know, this is totally ok, as making calculations off a photo with a calculator isn't the best form of measurements (meaning, measuring and comparing relative proportions between objects).

Edit: Eh, there are some drawn centerlines that aren't updated in the image, but they aren't really errors, just aren't updated. Easy to fix.

I added a 0,5 mm gap between the breechblock and the protruding edges off the two sides on the top, to avoid working with near 0,1 millimeter accuracy, which is not a good idea.That is a 3,6 cm gap in 1:1 scale.

Correction: I wrote "breechblock" with regard to gap/spacing, but it is this other circular thing that has this 0,5 mm gap to the two halves on either side, not the breechblock as I write above. :|

Treehugger
Image 62: Things looking good. Things falling into place. Trying here to recreate the shape of the connector piece from photos.

Treehugger
Image 63: Another discovery, a big one. There must be some kind of hinged, piston system, for lifting the cannon up, and it looks like the kit parts has spare room for this on the inside on each side. 🙂

Greg Baker
Wow... now this is something, ain't it? Pulling up a chair.

Jim J
Great progress. Interesting following along. Lots of discoveries along the way...

Treehugger
I think this will be a good looking model. Possibly same height or very slightly lower than kit (which was artificially too high). I added 5mm to the height, but reduced the spacing between the 8 carriages and the 4 semi-carriages over that, so on the fly I am not sure what the total height will be. However, becuase I've made the kit less wide, that should make it all look taller, and more massive, even though the breechblock is to be made smaller in size. Good thing is, all the railings will be set to proper human scale, and the barrel will be shortened. Because of the less wide model, it could be that it might be perceived as being smaller as a scale model, but I don't care.

Treehugger
Image 66: I think I finally nailed it. I found a lot of very good geometrical pointers, and with the help of symmetry, the mating surface was widened close to its apparent maximimum, which I guess makes a lot of sense. Image 66 has to be corrected even more, I'll do that tomorrow.

Treehugger
Image 67 & 68: I would think that the yellow lines on the drawing would be an accurate angle for the shapes that angle in towards the large hinge point that holds the cannon. I can imagine that the optimal line for handling shear forces is like this, connecting to the hinge area betwen the two halves at front, and the carriage hinge point aft. The yellow lines have been made symmetrical across the vertical axis. This also seem to match photos both fore and aft.

Edit: Hm, actually, I think it makes sense that the aft line also connects with the rear connector part, that connect the two halves together, so, maybe unsymmetrical angles for the "top" part on the sides. Hmmm.

Treehugger
Image 69: I guess, everything is lined up to sort of have the center point from the cannon hinge point, reach the center point down by the connectors fore and aft, and then, shape the angel for the top most parts, to reach the upper hinge point of the eh fore and aft connector boxes. Only the upper and lower rotation joints is shown on image for the connector box, the box isn't shown on the drawing here.

Treehugger
Image 70: I think I figured out the shape of the breechblock. It seems it should be centered. Being a little taller than its width. Also some extra length backwards, and having an opening that is lowered, on the bottom side to allow a tray to slide in with the powder and or shell. I wonder if they had to use various trays to load the different parts (shell, powder, end casing).

Here is a high res image: ibb.co/8jN85Xz

Eh, 22,5 deg, should be 45 deg (ofc, that is obvious, forgot to update that number)

Treehugger
Image 71: I noticed that there is this gap around the outermost barrel. Who knows what it looks inside. Making the diameter smaller to match the photos should help make the barrel seem more stubby. This means.. the kit barrel is too tapered. One could instead use a simple cylinder, looks great, certainly better than the kit part imo, and should be easier to create with some piece of plastic cylinders. I don't know if I would use a cylinder for the outer part, or try create somehow a new outer barrel if I don't want to use the kit's two halves for the outer barrel parts. The general shape of the outer side of the barrel has also been corrected here, as I think it has to look based on photos. I can't quite tell if the out-of-picture barrel part to the right, towards the breechblock and all, if it has a conical shape to it, or being just a cylinder shape.

Treehugger
Btw, I think I just realized that making a new plastic barrel is easier than I first thought. If you wrap a piece of paper into a tube, one can easily see one one can make a cutting guide for thin plastic sheet, and then bend that cut out plastic into a barrel, though probably requiring some kind of internal structure to help shape the circular cross section. 🙂

Treehugger
Image 72: Well, looking at the whole thing again, I came to the conclusion that I had to shorten the front and rear by 1 px between each handwheel, to fix two issues, so heh two problems solves in one go. I have to re-draw some of the stuff, but the wheels/carriages looks better now.

Hi-res: ibb.co/QkXG5Xs

Uh, another thing. I changed my mind about the breechblock opening. The opening is probably round. Doesn't make any sense that it has any other shape than round. A tray is apparently supposed to be placed into the chamber to load both the shell, powder and the end casing, makes sense that this area is flat all the way,

Treehugger
Image 73: This photo shows fairly clearly, that the inner part of the barrel, is only a little before the very front side of the two big halves (not the carriages). In the book I have, it is stated that the barrel (found inside the whole thing that runs down towards the breechblock) is 32 m long. This number I trust, and so new barrel lenght is set to 32 x 1000 / 72 = 444,44 mm on model, or, 4444,44 pixels on the drawing. 🙂 The thickness of the kit barrel is too thick near the base, so I am changing the barrel thickness to a smaller diameter, and I am moving the point where the outermost "barrel" connects with the "barrel" closer to the whole cannon assembly. Looks like the outer "barrel" is about the same lenght as the distance backwards towards the two hingepoints on the sides of the two big structures.

So, the cannon barrel in photo 72 is wrong, too long, and a little too big.

I have started to draw the carraiges more detailed, which will help determine a more correct width between the two halves, the cross section drawings I made has to be wrong, so that has to be made more narrow, but not too narrow. :|

I also made a quick black silhouette drawing, to get an idea of the mass of the whole thing, to better compare the drawing to photos.

Treehugger
Photo 74 show a simplified silhouette drawing, not entire correct detail wise, just a quick sketch that outline the major shapes, more work required on the cannon barrel ofc. With the carriages improved and more accurate, I can probably lower the big center piece a little lower to the ground. Heh, I am tempted to now buy sigh another set of metal rails that are more realistic sized, now that I have gone ahead and wanted to change everything I can to make the size more authentic.

Btw, it is somewhat obvious that some photos are not showing the true thing, i.e having been changed, as if painted over in places. This could explain the weird, non-existent mechanic seen in a photo, that show how the cannon is elevated by some kind of piston device on the inside. The kit, as in the photo, only show a flat area. Presumably, there is some kind of oval piston like thing, and not a flat thing there.

Also, I changed my mind, and I don't believe the cannon barrel has any conical shapes, except the one obvious one.

Treehugger
Image 75, show rail fasteners for Peco Code 143 flat bottom rail (metal). Not realistic, as they weren't invented at the time, but it would look good I think, too bad, they aren't afaik making them for the smaller sized rail Peco code 100 flat bottom rails. :|

Greg Baker
I have to admit, I have no idea what you're doing... but it's fascinating~😉

Treehugger
As long as I can work off a drawing, I can be fairly sure things will end up well. No way of knowing exactly how many kit parts have to be scratchbuilt. At this point, scratchbuliding the cannon barrel seems easy. I asked a UK company to create a custom alu barrel, but they wouldn't do it. Maybe too hard, or maybe they thought it could be used as a real firing barrel or something, or maybe they just don't do small orders.

I've sent an email to a company that makes custom photo etch, only to get to hear the pricing. Would be nice to be able to work with select photo etch items: 4 x sheets for carriages + maybe another sheet or two, if modeling a mesh area (walkway) on the inside/center. I can't use the larger photo etch from the kit, unless.. I accept some tweaks, which won't like like the real thing because there would be this border around the mesh that aren't there on photos, basically the kit's photo etch is too short and too narrow, not by much, but too much to look like the real thing.

Treehugger
@Greg Baker, the basic problem here is that the kit is whacky wrong. 🙂 The glaring errors are a form of amusement in itself: cannon barrel, cannon part, rear winch system, wheels, rails, carriages and more obvious stuff.

Treehugger
Image 76: The photo rifling looks bigger than my drawing. I guess that is because my "fins" are perhaps too tall compared to the photo, or, the photo doesn't show the same number of grooves/fins. I think it is just the slight excess height to the drawn fins.

Update: Ooops I have drawn 192 fins and 192 grooves. Back to GIMP :|

Treehugger
Image 77: Rifling drawing fixed, for now. Should be 96 fins and 96 grooves here in the drawing.

Treehugger
Image 78: Uuh, so if using 0.01 x 0.01" strips, I could fit 69 fins and 69 grooves inside a 11,1 diameter bore. 69 being 23 fins short of 96. It would be an improvement from the very short rifled nozzle bit in the kit (about a centimeter long), having 45 fins and 45 grooves. Haha would be nice to have 40+ cm of rifled barrel, and an open breech to show it in the other end.

Unsure how far back the rifling goes on real life artillery. Anyone have a clue?

This cannon is fed a shell, and then 2 sacks of powder I think plus an end casing of sorts which has its own length to it.

Treehugger
Now that I think about it, for my fill-with-putty-and-shape-rifling-with-pattern-disk, probably best if I could make a custom rifling profile in custom PHOTO ETCH to get a really nice result, maybe won't be too expensive with a custom rifling profile disk in photo etch being that small and all. 🙂

Treehugger
Image 79: Well, I guess it is a good thing I keep revisiting old areas. The cross section didn't match the rest, so the height on my drawing was obviously too high. Should be back on track now, having followed a lot of clues from photos. The main structure below the gun thingy, was made less tall, and look a little smaller now. Handwheels lowered noticeably.

Btw, I noticed that photos show tool boxes or something like that on the lower carriages, front and rear.

Treehugger
Image 80: Btw, image 79 is outdated. I eh think I finally figured it out. Stuff. I think I did well as seen in image 80. 🙂

Update: Hrm. Seems like the shape on the very end on the left, is just a box, not a part of the main structure. As seen in book on page 81.

Treehugger
Image 81: So, will be switching to CAD software (vector graphic), from GIMP (rasterized graphic), because otherwise, things won't print out looking ok. Problem: Printouts suggest clearly, that things printed out is 0,05% large. A temporary solution, is to print things out in 99,950248756218905 % of 100%.
Problem: My printout here of the small handwheel, seem to be too large, probably drawn too large (hopefully). Doesn't matter much if the handwheel isn't drawn accurately, but the circumference should be accurate to reflect the numerous kit wheels that I will use from the box (which should be about the correct size).

Treehugger
Update: So I found out that when I print stuff out on my laser printer, the things that are of length over 10 cm on paper, are too large. So a 200 mm long shape, is printed out as being 201 mm long. I did try to scale down things, to correct, but printer seems inconsistent, in printing out stuff at proper scale.

I had hoped to be able to measure off the piece of paper, of my drawing, but seems I have to rely on using measurements in the CAD software, which could get messy.

Update: I think the kit handlwheels are just a tad too small, but ok.

Treehugger
@Hans Robben
Ah, I must be mistaken. Must be 0,5 %. Which matches the printout. Sry, so many numbers going on 🙂 Got a little confused. So 200 mm on drawing prints out as 201 mm on paper, a incease in length by 0,5 %.

I guess, or I whould hope, a professional plotting machine could be a good idea to have the drawing printed out, to become accurate. Unless plotting machines as well have the same type of inaccuracy, something I don't know atm.

Treehugger
Image 82: This might look super boring to everybody, but the handwheels are really the primary source of accuracy from with other things are made to match. I initially did not trust the given distance in the book, of 30 000 millimeters between the hinge points for the main center shape, but I am working to shortening the entire thing, to hopefully make everything match and also maching the stated length of 30 000 mm. At least, the kit's numerous handwheels seems spot on (to me anyway).

I am not certain that using LibreCAD is a good idea. I guess my knowledge about it is't very good atm, having used the software for just a day, but it doesn't seem like drawn shapes have movable verticies, which could become really annoying to me if that is really the case here.

LibreCAD (2.2.0 RC1) has also crashed on me three times for no good reason and been weird (sometimes undo doesn't seem to work for me), so a little scary to use for me.

Treehugger
You must be confusing the two measurements. One is for the wheel, the other is for the plating behind it. 🙂 So they aren't the same, if that was what you were referring to.

Btw, I am working with both the GIMP drawing and the LibreCAD drawing, because if I wanted the pixel precision I wanted in GIMP, I had to double the size of the drawing, for the new file size of some 650 MB. 🙂 Also, rasterized images don't look good when printed for such drawings. I will eventually transfer the GIMP drawing over to the one in LibreCAD.

Tom ...
hmmm, how did I miss this. pulling up a chair...

Treehugger
I wonder how the two pairs of piping flows from the ends towards the center. This isn't clear from photos, which sadly don't show the center part that well. :| Presumably hydraulic fluid. Maybe doesn't make good sense having just the four pipes on each side, just go from front to end.

Treehugger
Weird, on page 82 in the book, there is a closeup photo of the handwheels at the rear end, and they are apparently numbered. The last one must be numbered 72, which doesn't match my count. I get a total of 33 + 1 + 33 = 67 in total. Oopsie?

Update: Ah, I think I know what is wrong/right. The spaces between the six pairs of ribs at the center, looks like they have four wheels in between, not just three as I had been thinking all along (so I can add five in total to make things match). Interesting!!! 🙂 Looking at photo on page 108, seems fairly clear that there are four handwheels there. I guess I relied on symmetry with trio of wheels.

Treehugger
Looking at the number of handwheels provided in the kit: 35 + 35 (inner sides) & 75 + 75 (outer side), with 72 handwheels on all four sides, that leaves 19 handwheels front and rear, on both left and right inner side.

So.. Those 19 + 19 handwheels covers the entire rear side, up to the rear box that connect the halves, however, the front side would lack 7 handwheels on each side, right in front of the front box, which sits deeper into the main structure. Hobby Boss couldn't be bothered providing one with all the wheels on the two insides. I guess I could try scratchbuild 14 handwheels, they would not be hidden away, but not easily seen. alternatively, move some of the handwheels from the rear, to the front, whatever looks better.

Treehugger
Image 87: I am really happy I figured out the handwheel stuff, the drawing looks better this way I think. If I hadn't checked this today, maybe I had never noticed it later. 😠 The drawn carriages, have to be shortened, to match the main body.

Treehugger
I just realized, that if I buy the Proxxon Precision lathe FD 150/E, I might be able to mill an aluminium barrel.. in pieces.. 🙂 That way, I could overcome the presumed limitation of not being able to mill a long 40+ cm aluminium barrel, but instead having various parts that fit into each other. 🙂 Some more investigation is required. With a mini lathe, I should also be able to mill train wheels I think. And I've wanted a mini lathe for some time now. Costs about £500 for the cheaper model. The 250 model cost double, but has more features. Could be that the 150 isn't good enough, if one can't automate the milling lengthwise like I think the 250 model allow.

Some further investgation into the suitability of the 150 model is required. Would be bad if it turns out the 150 model is missing some critical feature.

Iirc, the accuracy of the 150 lathe is an advertized 1/10 millimeter.

Treehugger
Image 88: Atm, the main part looks like this, much lower than the kit part, but sort of same length. The printout is 1mm too large lenghtwise, but hardly noticeable here. Presumably the lower height should make the gun look extra large eventually. I've been meaning to fully update this drawing, but I've fixed a zipper on a jacket and been sewing some curtains and I just been a little lazy in this respect.

Holger Kranich
Dammit! I wouldnt expect that there is so much work on it to do!

Treehugger
I had started to remove the detailing on the kit parts, the two big parts, but.. probably quicker and easier to make new ones with sheet styrene. The thing about the general shape is that, if not everything is made to look, plausibly correct when comparing to photos, something is going to look way off and make other things look way off. So I think it is better to try make a good drawing, then everything is so much easier and better after that.

Treehugger
Image 92: It looks to me that the leaf suspension is also supported by a secondary suspension on both sides of the wheel, the two thingies that go downwards.

Treehugger
Image 93: High res image: ibb.co/GT0GW5v (fixed)

Aah. Now I can finally get to complete the other stuff, with the carriages solved.

Edit: Ah, nope. I must fix some mirroring issue of a particular detail, and a little bit of cleanup. Done!

To clarify. So it turned out that, the measurements of 30m between the two hingepoints on the main structure seemed legit imo, and that the other stated distance between the two hinge points on the carriages, of 4250 x 2 mm, also seemed legit so to speak. I didn't trust the numbers at first, but eventually, they made good sense I think. The numbers are from a sketch in the German book on railway guns. The sketch itself looks bad, so that is why I didn't trust it.

Comparing the lower carriages in the kit box with my drawing, the kit carriages are ca 15mm longer, each (or, at least the front one is, not including the extra buffer part). 🙂

Comparing the top carriage in the kit box, with my drawing, the kit carriage is ca 9,5 mm longer.

Treehugger
Image 96: I thought I was done with the carriages, but I had to try something out to follow a new set of variables. I think I have made an improvement. Very hard for me to say if the carriages are supposed to be a little higher (they were lowered a bit) when comparing to photos. I changed a lot of things on the center main structure.

Edit: Ofc, I had forgotten to update something here in image 96.

Treehugger
Image 97: It just occurred to me, that, if I am a little lucky here, the reduced width of the top carriage, if ending up around 42 mm, would be the same width of the kit's photo etch. 🙂 Only thing then, is that, the length of the kit's PE is 5mm longer, 2,5 mm fore and aft, than my current suggestion. Very, very interesting. 🙂

Treehugger
Image 98: Oooh. It looks like I can get to use the photo etch for the top carriage (four of them). And, it isn't obvious to me that this would make the top carraige too long either when comparing to the photos in the book. 🙂

Treehugger
Image 99: I looked at some more clues, and with a good photo with little to no perspective distortion on a plane, I figured the width of the main halves to be pretty much 875 mm, or 12.15 mm in 1:72 scale. Also, it seems obvious now, with one photo, that the lower "connector arm" simply can't have the same angle as the upper connector arm, which could explain why I couldn't fit them symmetrically on my drawing previously.

Epoch 3
Please see also forum.axishistory.co..=hobby+boss#p2096972 and forum.axishistory.co..;hilit=dora#p2045491 Regards

gorby
WOW! What a remarkable project!

Treehugger
Yes. 🙂 I lost my mojo when I had to conclude that I need a lathe machine. I will have to return to this project in the future. I think I have been able to make accurate drawings, but I don't have the will to finish this knowing I have to create lots of custom parts.

I already paid for some extra tiny hand wheels to be able to fit them all on, so that is something. The kit doesn't include all the small hand wheels. 🙂 Terribly flawed kit, not recommended in any way. Most of the kit is just wrong. HobbyBoss/Trumpeter probably did not have any scale drawings at all, and failed to recreate the design properly.

gorby
Surely if your drafting is as good as it looks, then 3D printing is the way to go. Then design a part once and print a hundred in one go. The prices of 3D printers are very affordable now and I know a few people who do remarkable things on them. This would be the perfect project.