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KI-44-II Otsu, 1/20th Scratch build


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Hey all,

Down here ill be posting the progres report of my KI-44-II. The idea is to build this (and other) models out of the most authentic materials.                                                   Basically; only some complicated shapes are made from castings, the rest is made from materials same as the real thing.                                                                                  Stuff like engine parts, rims and weaponry are resin castings. 

As ive learned, many of the required technics were difficult to master, additionally there was not that much info known or photographed about this topic.                          If theres anything ive learned about this project, its that you should never wander to far from the orignal, ive wated too much time designing my own workable gear, flaps, cowlflaps and tail section. Ive should have just stuck with how the orgnal design is (were possible). Indeed many of the things i easily planned and designed in the spring of '17 became a failure in the winter of '21

What whould be an aprox 14 month project became a 4 year nightmare. ( not fultime ofcourse). The main problem was that ive also invested in quite a collection of tools and parts, effectively pulling me down the "Sunk cost fallacy". This was even worse because i haven't finished any modely for many years. This time...i could not bottle out...

 

Nakajima Ki-44:

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The Nakajima KI-44 was basically there to fill in the gap left by the Ki43 Oscar and A6m Zero; (High altitude fighting). It was powered by this huge Nakajima HA109 14 cyllinder radial. Which is about 10 cm bigger then the engine on a A6m Zero. The Ki44's min speed and wing loading was quite high but with the butterfly flaps, it was still pretty maneuverable.

The was is to make everything on this model fully moveable and operational. That includes cowlflaps, flight controls landing gear, and and en engine with workable pistons. The thing is that its usually a lot easier to set high standards then to actually achieve them...

I'd guess thats an ok introdution for now... How about we dive into the sh*tstorm, diaper hurricane dumsterfire thats....

 

                                                                               The Nakajima KI44-II Otsu "Shoki"

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Part 1. Engine.

 

March 2017: 

Ive been walking around with the idea to construct a large 14 cyllinder engine, should be about a 7mm bore. Max diameter would be 65mm. The most importand part is that it should be available for mass production: for further models and retail. Additionally, it should have working piston movement and ease of assembly

 Luckily i had some expierence building these kind of things:

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All of these engines have working mechanisms, and they are a achievement of their own...also they are all mass producible. So if you ever need a Mercedes DIII in 20 th scale...Send me a message.

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Since i like the more "obscure" models, ive opted to start a Japanese engine: The Nakajima, Ha109. Sizewise, it should be close to R1830 and BMW801. 

Since the core of these engines look pretty similar from outside, and most of the time, the engines will be covered by cowlings, i would be able to change certain parts, turning it into different types easily.

Ive started the prototype phase on late march 2017:

Most of the drawings are lost...somehow...But i dont need those to rememeber ive started from the inside out, With the heart of the engine...

The crankshaft: its comes in 3 diffent pieces, that fit into eachother with tiny splines.

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Based on the crankshft and its stroke, cylinder size and way of mounting cylinders, ive started the crankcase:

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Lots of filler to be applied:

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Entire cranckcase: Note: The rear wheelcase is actually for a Nakajima Sakae 11. 

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To guarantee all would still fit after casting ive made the moulds as i went along.

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I hate this picture below because you can clearly see the poor texture on this prototype. As it turned out, it was because of the wrong type of resin. Admittedly ive never really perfected the surface, then again..in later versions its a lot cleaner. Picture just brings out the worst..in this case...

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With the crankshaft working as req'd, i went for the internal parts:

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Especially the cylinders and con rods...in total i used 4 different resins to make sure everything is stong, flexible or hard when its supposed to be...

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To guarantee the bore is consistent, the cyllinder sleeves are actually metal...Which allows me to polish them with special tooling.

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First time test fitting case and cylinder:

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Ive experimented with different nose cones:

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Slowly but surely more and more moulds,

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"Some are actually quite pretty" says the guys who makes them:

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Around August '17: Pretty much all moulds finished and major parts casted:

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Which means were up for first time build up: I cant remember but judging to this picture, i still have to clean up many parts.

 

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This is bassically the last picture of the actual engine production. In the next update ill post the ones made during a recent overhaul. They show more of the engine itself, looks more cooler i think

Also, if any of you have any suggentions, i really need the constructive critism...

Thats it for now,

Luke,

20th factory.

 

 

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I admire your drive to produce an accurate replica of an engine, down to the master rod and pistons. It’s a Zoukei-Mura type approach, technically interesting, but, in fairness, gloriously useless for a static model (although this is very much something I could see myself doing ;) )

One remark concerning the cylinders’ designs. In the drive to extract more power from them, the cooling surface increased, by adding more and more fins, densely spaced. Your cylinders are more suitable for Lindberg’s Wright J-5 than for a more modern high-output WWII radial. Using a resin-casting process entails technical limitations for an accurate representation of your cylinders, even in big scale. You’d be better off 3D-printing them, especially as recent SLA printers can offer a very high resolution and thin layers to reproduce high-density fins.

I am sure you have seen Airscale’s work on skinning 1/18 models with aluminium litho plates. He is a master at shaping these plates, even on ver6 tight compound curves.

Keep posting your work: I really like it, and I am sure others here too :popcorn:

Hubert

 

 

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that's skilled craftsmanship and amazing dedication to accuracy, you should feel very proud. Makes my sticking bits of pre-molded plastic together seem like childs play (which I guess it is given I was doing exactly the same as a 10 year old as I am now !!)

neil

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