Using Rhino to Model Printable Replica P-51 Mustang Engine Parts

Hi Rhino Users;

I would like to share a bit about my hobby. I have used Rhino for 10+ years, and still consider myself a “perpetual beginner” because I haven’t really mastered the software. I would say the same about using Brazil, which I use to create decent looking images of our upcoming house renovations. I wish I knew more about both softwares, but perhaps one day…

Still, I do get very good service out of Rhino. I run a 3D printer at work, a good industrial one that laser-melts nylon powder into large, strong parts. When there is unused room in a build, I add parts for my work colleagues, and for myself.

Here’s my hobby; I have most external original parts of a Rolls-Royce Merlin V-12 engine, the one that powdered the Spitfire, Hurricane, Lancaster Bomber, Mosquito and P-51 Mustang. I am also missing many of the large castings, like a complete cylinder head and cylinder block, the large heat exchanger that cools the fuel/air mixture after it’s been supercharged, carburetor, etc. Since these original parts are scorchingly expensive, and I have access to a printer, and I like 3D modeling challenges, I thought I’d try modeling these parts and printing them. So far, so good. I’ll attempt to upload a few photos of my printed parts, but as this is my first attempt on this forum, it may not work as planned. If you don’t see any images, you can see my whole album of printed parts here; rrmerlin60’s albums | Flickr

Remember, these are all modeled, quite painstakingly with Rhino (and sometimes in SpaceClaim software), corrected in a software called “Magics” by Materialise, and then printed, FULL size.

Cheers and discuss if you wish to. Tom, Ottawa.


Good job. I see you used a 3D scanner to capture the original parts. For missing parts, do you use Rhino creating nurbs surfaces based on original designs? How do you return to the meshing tolerances between mesh and nurbs? (If you can answer naturally)


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Hi Simon;

Thanks for “stopping by.” I use any dirty rotten trick that gets me CAD
Merlin parts that I can then print. The V-drive, that V-shaped lump sitting
at the front of the engine,which controls propeller pitch, was reverse
engineered using rulers and photographs only. I did take my company’s
scanner to Vintage Wings in Gatineau Quebec and capture decent scan data of
the aftercooler box, and the valve covers. I had previously scanned my one
cylinder bank and head at home.

To try and answer your questions, I cannot guarantee the accuracy of these
parts at all. If I am lucky to have some scan data, I use Rhino to create
3D models, while they exist in the same 3D space as the scan data in the
Rhino desktop. I just switch the scan data on and off when I want a visual
check of the new model’s accuracy. I personally wouldn’t know a nurb from a
fuse box, but I can easily check, visually, if the 3D model that I am
creating, is very close to the scan. I can also do that in Magics software
(by Materialise) which is a robust software for working purely in the stl
world. It Booleans items where Rhino sometimes fails, which happens when a
model becomes too complex, or perhaps full of my errors.

I hope that sheds some light on my process, but bottom line, Rhino is
critical in this process, as is Magics, and other tools.

Cheers, Tom.

I understood the workflow. Thank you for sharing.


You might want to talk to Mike Patey. Im sure he can point you in some good directions. He seems to do it all or know how to…

Relevant video…

Also i’ve encountered many 3d models of the merlin and parts of the P51…

And this was pretty detailed… There’s a lots more parts in grabcad.

There’s more on Yeggi but looks like modelism

Hope it helps.

just saw the post was 3 years old, oops… P51’s never die… :wink:

That guy is cool. Simply incredible. I remember seeing the first videos on DRACO some time ago, and just now I learned that he crashed it!

Looking forward to see the next build Scrappy out flying.

// Rolf

You’re right Xavier, P-51’s never die.

Still lurking on this site. Still adding printed Merlin parts, too.

Cheers, Tom Kay.

Passion makes you fly :slight_smile:

Hi Tom
What files are you using? Would you be interested in sharing a few of your files… maybe in STL. I’m building a Merlin for a friend in england as a gift, and the cylinder heads are what i’m after. Engine mounts would also be a great thing as well.
PS … Beautiful work… You have my full admiration

Hi Paul,

Thanks for saying hi. I really want to be careful in sharing files, because they took a very long time to model and then print. I have had some simple photos that I shared, which were then magically Copyrighted by some jerk.

Please tell me a bit more about the project. Is this a plastic replica, metal, a full running engine ? What scale will it be?

I also only have the left cylinder head model, since I have the actual right cylinder head, and didn’t need to create that model. The heads are almost mirror image, but not quite.

Cheers, Tom.

Hi Tom
Firstly, thank you for responding to my request. This engine is for a friend of mine in England… He has a passion for spitfires, and is presently collecting parts for his own collection. He hosted us (in Kettering England), And showed us around the American bomber base that my friend and I had been researching. Present day we are preparing to go to England on another history trip. We are going back to Kettering, and I would like to take Kevin a present. Our second host, is going to receive a 1/9 scale Pratt and Whitney 2800, the Merlin will go to our other friend. I’m thinking of doing it in the scale of approximately one to 10.
With kindest regards
Paul Boydell

Hi Paul. That would be a nice gift.

Will it be 3d printed ?

And what parts do you already have ? I could give you a 1 tenth scale model of the left cylinder block or head. At that small scale, it would be tough to notice the small differences between the 2 heads.

What’s your schedule for this ? And have you seen the printed parts on my Flickr site ?

Cheers, Tom.

Hi Tom
I have the GA 3-D printing print of the Merlin. I’ve combined what I could get out of crab cat to put pistons into the model. But when I do that you left the cylinder head off , And the cylinder head is all supports… I thought it would look much better as a true cylinder head… Possibly with valves. My timeline is September, when we go to Grafton Underwood in Kettering. I have to say thank you so much for your magnificent work. What sparked your interest in re-creating a 3-D printed Rolls-Royce merlin.
Looking forward to your response


Hi Tom
I would like to persue some parts off of your Merlin. Ive tried to convert the files off of Grabcad… but it’s been hit, and miss. Perhaps we could persue this more privately on say e-mail, or messenger.
Thanks Tom

Hi Paul;

Thanks for showing me some pics of your Merlin project. It’s coming along nicely.

I must admit I’m having a bit of trouble understanding some of your text. For example “But when I do that you left the cylinder head off” Uh, I left the cylinder head off ?? I don’t follow what you’re saying here.

Anyway, I do have some models that I could share. And having seen your work, I believe that’s what you want the models for. I am always concerned about people taking my hard work, and simply using it for their own financial gain, which has happened with simple 2D printed photos of Merlin stuff. So I try to be cautious. And believe me, these models represent years of hard work.

What part models do you need ? And making a working cylinder head, with tiny moving valves will be challenging, at your 1/10 th scale, and with a printer that needs supports on its parts. Challenging, but maybe not impossible.

So, please let me know what you need and I will consider if and how to share the models with you.

Cheers, Tom.

Ah, maybe you think that the Grab Cad model is mine. I actually didn’t upload or model that one. Someone else did. I find the Grab Cad model admirable (all Merlin efforts are admirable) but the models seem faceted and clunky. Also, it’s the single stage Merlin, and I have a 2 stage that I need parts for, so that’s what I’m focused on.


Hi Tom
I’ll have to watch the auto correct … it seems to have a mind of it’s own. That was lift off the cylinder head. … I realize that the models on Grabcad weren’t yours, and what i was trying to say was I’m not having success in file conversion from Grabcad files to STL. at minimum, the cylinder head is what i’m looking for… but in reality, the crankshaft, con rods, upper, and lower block… pretty extensive really. words are cheap, and I understand you’ve been stung… this is my hobby… I work on warbirds on the weekend…Any files you share… stay with me. What I was gently trying to say, was I would be willing to discuss, in private, compensating you for your efforts. I have the external representation of a Merlin that most people would be more than happy with…I want something special. if you decide not to share, I find that fully understandable… I can see the effort you’ve made… entirely commendable, and well done

Hi Paul;

Thanks for your understanding. Please feel free to email me at I realise that was broadcast to anyone, but that’s OK.

Cheers, Tom.