1/35 Ball tank

[Frank3k]

I started this over at Whatif: The  Miniart 1/35 Sharotank, Soviet ball tank that I'm going to build as a US between the wars "advanced tank":



The kit is well engineered, but the The Modelling News build is an essential reference. One problem noted in that review is that that the crew seats are far too small. I'll scratchbuild larger seats and reduce the crew to four or even three, if I can't fit them all in the hull.

Here's the "seat issue":

Seat from the Tamiya Quad Tractor, vs the kit seat:



Our friend Nigel from the same kit in his seat:



It looks like a child's seat. "Take your kids to war":



Here's a page on ball tanks And for some enjoyable retro reading, The Popular Mechanics issue for July 1936 had a ball tank on the cover and a short article on page 37. Read it here



Miniart seems to have put some thought into how this ball tank would be designed and operated; there are four brake pads that somehow slow down one side of the tank, allowing it to slowly turn.

 The two side rails are not easy to put together and align. I had to superglue some top and bottom posts first, just to stabilize and square the assembly, then go around and glue the remaining posts. But that was a minor annoyance and it's been an enjoyable build so far.

Here's the central ring (in progress) with the bare seats I scratch built and two of the seat supports from the kit:



The drive wheel assembly is in Atom olive drab, an acrylic paint made by Ammo. It's hand painted, but looks airbrushed. Great paint!

I used ProCreate 2 part putty to make the seat cushions. This putty works well and stays somewhat soft after curing, so it can be worked for a bit. Once it's fully dry, I'll add some texture and paint:



Next step will be adding the weapons. Two 30mm cannons (I'll upgrade them to the 37mm US standard) and two machine guns seems excessive. The spatted side wheels look flimsy and useless other than for balance, so I'll have to think of something else.

[raafif]

These are interesting - seen a few different builds in the last 2 years.  Would be nice to see a factory scene with one as a skeleton & another closed up being painted. 

[Jeffry Fontaine]

Seating for five?  YGBSM!  That would have been a severely cramped vehicle even with two seats.  The Tamiya Quad seats are also a bit on the small side when compared to other seats in same scale but definitely not as tiny as the kit seats.  I like the details provided by the internal frame to give you an idea of what it would have looked like inside with the engine and drive system but I cannot imagine anywhere near five people stuffed inside with all of that.  Oh, wait, it's Russian/Soviet so no thought or consideration is given for crew comfort or safety.  Yeah, now it all makes more sense. 

[Frank3k]

Jeff - The Quad seat is small, so I enlarged it by about 1.5 mm on all sides. It's still a bit small. The kit seats hang off the round connectors on some of the bars, which means they're dangling next to a hot engine. The ball also doesn't seem to have any suspension at all - so unless the seats are on bungie cords, it's going to be a bone jarring drive over anything but a paved road. They'll feel every pebble!

The ball needs a driver, but I'm thinking just one 37mm gun and two crew for that - similar to the "Tumbleweed" tank of the PM article.

[Frank3k]

I only had a short build period today.  I put together the 30mm, now 37mm gun. Lots of tiny, tiny parts but surprisingly easy to put together. The barrel isn't attached:



Miniart has these odd brake pads in the lower front and rear, where they would contact the main wheel. I'm not clear how well they would work to turn the tank:



Here's Nigel in the driver's location (just tacked on). The outer shell won't fit without bumping into Nigel's feet, so I'm going to move the seat back 3-5mm:



Here's all I got done today. gun assembled, fuel tanks and radiator, plus some details on the main ring. The large dark metallic gray boxes are the fuel tanks. The gun is painted in Atom Olive Drab:



I'm thinking of adding the 37mm gun to the right hemisphere, with a gunner and loader. The upper hole will either be blanked off or used as a ventilation hole. The left side will have the driver and the TC, with a .30 or .50 cal on the rear ball mount. Same with the upper hole. Maybe it can be a periscope or range finder for the TC. Another option is to swap the gun and driver sides, giving the loader a MG for the rear of the tank.

I'm also thinking of modifying the trusses and support in the middle (which are used mainly to hold the undersized seats) to allow crew members to move from one side of the tank to the other, without having to crawl over a hot engine.

[Kerick]

How about if you sculpt Nigel’s backside and carve out the seat. Perhaps that will buy some room for his legs. Just my $0.02.

[Frank3k]

I felt that the hemispheres looked too smooth, so I experimented adding a casting texture to a styrene rectangle. I mixed some putty with acetone and stippled it on with a stiff brush. In another section, I tried some unthinned primer paint. Finally, I tried it with some thinned Tamiya surfacer. Of the three, the thinned (with denatured alcohol) Tamiya surfacer worked the best. Stippling the hemispheres and the hatches was pretty easy and relaxing work - paint a sector with a layer of surfacer, stipple it, repeat.

Next, I worked on the 37mm gun. Since the gun was originally at the top of the ball, it was difficult to get the ball joint for the gun to point straight forward in it's new forward facing location. So instead, I repurposed one of the machine gun ball joints:



You can see the text strip next to the tank in these pictures.

I also added the driver's sad looking view slit (I may need to fix that) and the second rear facing MG ball joint to the driver's hemisphere:



Tomorrow, more interior mods. I added the foot pedals to the driver's side.  With the seat's intended location, the driver would be sitting with his knees up to to his chin.  I'll move the seat back by a few mm.

[Old Wombat]

Neat progress, Frank!

With the seat's intended location, the driver would be sitting with his knees up to to his chin.

Definitely Soviet/Russian!

[ChalkLine]

That's so funky, it'll be a shame to close it up

[Kerick]

I like that stipple technique. I’ll have to remember that.
This build is giving me ideas. Dangerous!

[Frank3k]

The hatches are pretty big, so much of the interior is visible.

Ken - it was surprisingly easy to do the stippling and kinda relaxing!

[apophenia]

... it was surprisingly easy to do the stippling and kinda relaxing!

I can see how that stipple work could be therapeutic ... but the effect is also highly believable 

[Frank3k]

I'm almost done with the interior. I removed some of the horizontal bracing to make a space for the crew to move from one side of the vehicle to the other. I added some vertical bracing as well, which (maybe not surprisingly) added quite a bit of stability to the assembly. I also made a wooden floor so the crew can scoot from one side to the other without having to crawl over a hot engine. The seats are just tacked on in this picture:



I realized that the ball tank - with no obvious source of ventilation - would quickly fill with a noxious atmosphere of CO2 and Carbon Monoxide from the engine and gases from the gun firing. Since I moved the gun to the front, the upper gun port was no longer needed.  I made a fume extractor/fan assembly out of one of the wheels for the door locks, a trimmed drive wheel from an anonymous tank and I believe the fume extractor from the Tamiya M41 kit. A crew member would turn the wheel to raise the extractor and turn it on. Interior view:



Exterior view with extractor raised. I painted the exterior with Olive Drab:



I still have to finish the main interior and fix nicks and scratches on the white paint and add the gun and ammo to the right hemisphere.

[Jeffry Fontaine]

Nice touch with the fume extractor.  Now what about seat belts?  Just kidding! 

[Mig Eater]

I'm loving all your little enhancements, I have one of these in the stash too so I'll be taking notes. Speaking of which, I remember seeing in another build of this kit that there is an indent below the square vent were the exhaust should go, they drilled a hole and added a pipe. The exterior lamp on the left side is also missing the bracket to hold it in place so you need to scratch built a new one.

[Kerick]

This a very fascinating project. Lots of ideas to consider.
Keep up the great work!

[Frank3k]

I'm loving all your little enhancements, I have one of these in the stash too so I'll be taking notes. Speaking of which, I remember seeing in another build of this kit that there is an indent below the square vent were the exhaust should go, they drilled a hole and added a pipe. The exterior lamp on the left side is also missing the bracket to hold it in place so you need to scratch built a new one.

The exhaust pipe almost looks like a small molding defect and I can imagine modellers putting some putty on it and sanding it smooth without realizing. Same for the tiny scratch where the headlamp goes,

[Dr. YoKai]

Coming along nicely, Frank. I knew there were a surprising number of these kits out there, but the Miniart kit was a surprise.

[finsrin]

So unusual.  Is an OOB kitbash 
Looking fine, thanks for pictures.

[Story]

More inspiration

[Kerick]

We need a model of this baby!

https://m.youtube.com/watch?v=rvA7hDh_vhY

Gotta love the Dynasphere!

[Mig Eater]

I started designing a 3D printed model of the US Tumbleweed ball tank a few years ago but didn't get that far, I might finish it some day tho...

[Frank3k]

I want to try it, since the artwork in the Popular Mechanics article is pretty good.

The page at Tank Archives on spherical tanks has the paptent, which should be good for dimensions.

This Armorama build from 2007 is fantastic, although it's more of a oblate spheroid:

[Frank3k]

I think I'm almost done pimping the interior. I made a movable periscope for the tank commander, but like all things ball tank... it will be of limited utility. Here are the two hemisphere interiors. The black wires are for the fuel lines, which will get glued to the engine... somewhere. The brass on the 37mm rounds is more gold than brass, but it's what I ended up with:



This is the driver/TC side. There's a green wire from the driver's seat to the brakes. I scratchbuilt a battery (on a shelf to the upper left) and cabled it up as well:



37mm gunner and loader side. I added the diamond plate floor just to give the loader something to stand on. His seat also blocks direct access to the exposed, unprotected radiator fan, which will be right behind him.



This vehicle would have been ridiculous in practice. Rolling down a hill uncontrolled would have been only one of the many problems with this design.

[Mig Eater]

This vehicle would have been ridiculous in practice. Rolling down a hill uncontrolled would have been only one of the many problems with this design.

I can imagine it coming down a hill to fast so the driver applies the brakes but they lock up and then the whole tank just starts rolling wit the crew spinning around inside