P-47D Thunderbolt in 1/18 Scale Totally 3D Printed

[Juggernut]

On 9/14/2025 at 2:35 PM, JayW said:

 

 

Oh they are Curtiss Electric prop blades for sure.  But just which type, well now I just don't know.  Per the Republic powerplant installation drawing, this type (P-47D-21RE) got the smaller 12'2" prop (designated type 714), same as all earlier models.  And starting with the -23RE, the larger type 836 blade was introduced.  

 

I found this on the WWW somewhere:

 

 

Look at the first blade (type 714) and the third one from the left (type 836).  If I had to pick one that Dove of Peace sported, I would say the 836 based on the more rounded tips.  And if so it was retrofitted.  I don't know if the 836 was considered a "paddleblade" prop (the obvious "paddleblade" types above are the SPA-1, SPA-2, and SPA-3), but I would be more than happy to model it, rather than the old smaller blade.  That said, "Dove of Peace" has taken an early lead in my selection process.

 

The C642S hub with the 836-14C2 blade is a 60 series prop and goes only on the P-47M and N (R-2800 C series engines).  The 542S hub that represents a 50 series spline prop shaft and belongs on all the other P-47 types.  The 642S and 542S hubs are not interchangeable.  The SPA-1, 3, and 5 are what's called the "assymmetrical" style of prop and you can see these on a number of bubbletop jugs but not sure on razorbacks.  The 714-1C2 is the original prop fitted to the P-47 series and were eventually replaced by the C2521200 and 836-2C2 bladed props (the latter referred to as the symmetrical prop).  The name "paddle blade" referred to almost anything other than the basic P-47 prop and was popular mid-war when these props were replacing the needle-blade prop (714-1C2).

[JayW]

6 minutes ago, Juggernut said:

The 714-1C2 is the original prop fitted to the P-47 series and were eventually replaced by the C2521200 and 836-2C2 bladed props (the latter referred to as the symmetrical prop). 

 

Good stuff!  In your opinion, which prop blades are you seeing in this picture?

 

[Juggernut]

836-2C2

[Greif8]

Wow!  Your 3D printed engine looks awesome Jay.  I have enjoyed reading the technical information in your thread as well, very educational.

 

Ernest

[tomg]

The moniker "dove of peace" on a brut like a P-47 is irony defined. 

 

Can't wait to follow your progress.

[Gazzas]

So glad you're doing a razorback.

[JayW]

14 hours ago, Gazzas said:

So glad you're doing a razorback.

 

Mate - that's not 100%.  It's about 85%.  😁

 

 

Edited September 20, 2025 by JayW

[dennismcc]

Well its all black magic to me but it is certainly fascinating, looking forward to more.

 

Cheers

 

Dennis

[Oldbaldguy]

On 9/18/2025 at 4:52 PM, JayW said:

"What's taking so long Jay?", I ask myself.   Well as a reminder this is an 18-cylinder engine.  Here is a shot of the production line as it stands today:

 

 

Nearly 40 cylinders you see there, half of which are in that white bowl - and three of which are essentially complete (in front).  Stand by - photos to come of some pretty amazing details, soon.

 

BTW - some of you may have noticed that there are parts for two engines.  My plan is to display a complete engine next to the P-47.  I could not have done that with the Corsair's engine; I would have gone mad since that engine was scratch built and with machined parts.  Still going to be alot of extra work, but more do-able.    

Might be worthwhile to mention at this point that the cylinders on radials were not always uniform in appearance.  When the engine was new, everything looked it.  But as the engine accrued time, cylinders came and went, being pulled and/or replaced with a degree of regularity and, being bare metal, they aged differently depending on where they were on the engine.  The result was different patinas under the cowl and varying chipping and wear on the painted parts that were handled more than others.  As modelers, most of us build fairly uniform radial engines and then add the usual leaks, drips and crud and call it a day.   Since you are you and are working in giganto scale, you might consider that rabbit hole.  I’ve never seen anyone take things to that level so it might be yet another first.

[JayW]

Let's start assembling a 3D printed R-2800 shall we.  We start with the engine block (you have seen this already):

 

 

It has 18 keyed holes for the cylinders, and 36 little circular depressions for the valve rod covers.

 

Now we build up the front row cylinders.  Here is one of 9 front row cylinders, fresh out of the printer, not yet freed from its many supports:

 

 

Trim away the supports (carefully), and you have a raw cylinder ready for detailing:

 

 

 

Note that I integrated the side sheet metal air deflectors (previously mentioned a few posts ago) onto the cylinder.  

 

Here is the parts kit for one cylinder:

 

 

It consists of the now painted cylinder, a 1/4 inch dia mounting tube, two rocker arm covers, and the signature inter-ear drain tube (made of .025 dia wire).  

 

How did I make that curved wire?  That was not that hard.  I designed and printed a little form block:

 

 

 

It allows the wire to be formed like this:

 

 

Note the form block has grooves in the sides to locate a proper trim.  And here is the part trimmed in the tool:

 

 

 And the finished part:

 

 

And a fully assembled front row cylinder:

 

 

It has been weathered with black wash, and will soon get a clear flat rattle can spray, and then assembled onto the engine block.

 

Here is one of 18 valve pushrod covers for the front row:

 

 

 

Note it has castellated couplings on either end - I think that is way cool.  Internal combustion engines generally have two valves per cylinder, one for intake and one for exhaust.  Almost without exception they are driven open or closed by a spring loaded rocker arm on top of the cylinder head, which is in turn driven by a long pushrod that spans the top of the cylinder head to a dedicated shaft inside the engine block (unless the engine is an overhead cam type).  The shaft is driven by the crank shaft and has machined cammed lobes that control the up/down movement of the push rod.  In a car engine these push rods are hidden inside the engine block.  In an air-cooled radial, they are mostly outside the engine block, and covered by a tube.  That is what you see above.  Look for 18 of these on the completed assembly.

 

I have mentioned side air deflectors on the R-2800 cylinders.  They also have top air deflectors.  In the picture below (from the parts catalogue), the top deflectors are items 22 and 23:

 

 

 

What is not shown in the picture is the ring they attach to.  

 

Here is my upper deflector assembly fresh out of the printer:

 

 

I chose to combine the eight (not nine, eight) deflectors and the ring into one part, and then hoped it would work out.  Here it is free of its gazillion supports, and spray painted flat black:

 

 

Yes - uber-fragile.  I was on pins and needles trimming off the supports.  That part would round out the assembly.

 

And here we are so far.  Aft side (will be largely invisible):

 

 

Fwd side (will be almost fully visible):

 

 

I mentioned eight (not 9) deflectors.  That is because that space on the bottom cylinder (number 10) is occupied by an oil sump for the cylinder heads.

 

For those of you who followed my Corsair R-2800 build a few years ago, you know it took me many months to get to this point.  That engine was not 3D printed; it was scratch built fin by fin, with a lathe and end mill machined acrylic engine block.  Here it was at the same level of completion:

 

  

 

 

I hope y'all agree my latest effort is much better (and I can tell you - much easier).  And BTW - this is engine number one.  It will be on static display on its own.  Engine number two, which will benefit from lessons learned along the way, will follow and will be installed into the P-47's cowl at some point. 

 

Next up is a little break.  Then it is on to the aft row, the intake pipes, and the exhaust extension pipes.  Take care and stay tuned!

 

 

 

    

Edited September 21, 2025 by JayW

[Gazzas]

That engine is a thing of beauty.  That ring of deflectors...    that thing has "break me" written all over it.  So glad you didn't.

[LSP_Kevin]

Amazing stuff, Jay! Making your own 3D-printed tooling is genius.

 

Kev

[Kaeone57]

Beautifully executed!!

 

Alfonso 

[Jim MacDonald]

Beautiful work, Jay. It's great to see the evolution from a 2D blueprint to a 3D solid. Kudos. 

 

Mac

[Greif8]

What a work of art!  The engine will look great on its display stand Jay.  I would buy one of these in 1/18 scale just to build and display as you plan to.  

 

Ernest