Been doing a CAD model of the Merlin Engine just for fun

[Michel Lemieux]

Thank you for all the answers!

Were you able to model all the internals hollow space with the oil & coolant passages? Just curious.

[rtwpsom2]

Were you able to model all the internals hollow space with the oil & coolant passages? Just curious.

In this case there are only oil passages, the crankcase doesn't have any coolant passages. But yes, the CAD model is perfectly accurate in how the internal hollows are cast. With just a little bit of work this casting model could literally be used to create new parts. However I seriously doubt it'd ever come to that in our lifetimes. If you've ever seen pictures of engine restoration shops, they've all got a hundred cores sitting on their shelves waiting for restoration. And even then, people have become very adept at repairing the broken castings, too. I don't think any of my models will ever get used for that purpose, though it would be really nice.

[hardlanding]

people have become very adept at repairing the broken castings, too.

I know this is off-topic from the CAD work, but this is the first I've heard that blown crankcases can be repaired. What is the typical mode of failure when the Merlin crankcases are broken - is there a typical location where cracks occur? Are these repair techniques bringing back to life all those racing-boat-blown crankcases?

[rtwpsom2]

What is the typical mode of failure when the Merlin crankcases are broken - is there a typical location where cracks occur? Are these repair techniques bringing back to life all those racing-boat-blown crankcases?

Usually something along the lines of a connecting rod going through the side wall. I doubt that too many of them are being repaired at this point bot I have seen at least one that had holes in the crankcase repaired and running on a display trailer. I assume if the hole was made in such a way that it didn't damage anything but the sidewall, then simply welding a patch on and grinding it smooth is fine. It's only when it messes up the structural webbing of the main bearings webs that I doubt it would get repaired. I've also seen case bosses that cracked get welded and re-drilled, but that is a common practice in almost every aluminum engine block.

[DoraNineFan]

What is the typical mode of failure when the Merlin crankcases are broken - is there a typical location where cracks occur? Are these repair techniques bringing back to life all those racing-boat-blown crankcases?

Usually something along the lines of a connecting rod going through the side wall. I doubt that too many of them are being repaired at this point bot I have seen at least one that had holes in the crankcase repaired and running on a display trailer. I assume if the hole was made in such a way that it didn't damage anything but the sidewall, then simply welding a patch on and grinding it smooth is fine. It's only when it messes up the structural webbing of the main bearings webs that I doubt it would get repaired. I've also seen case bosses that cracked get welded and re-drilled, but that is a common practice in almost every aluminum engine block.

There is an old picture of a race Merlin that was sliced in half by con rod, but I doubt that crankcase is repairable. I do think a hole in the side wall is repairable with techniques today.

[bdk]

I do think a hole in the side wall is repairable with techniques today.

Not sure it would be worth the liability to any professional overhauler. Aircraft parts tend to be a lot thinner than automotive applications due to the weight limitations of the original design. For a certificated engine this becomes more difficult to get approved. I could see the repair of a valve cover boss or other non-structural item. Damaged or cracked fins are often weld-repaired on air-cooled cylinders for instance.

[rtwpsom2]

The repair I saw was much smaller, like 2" x 3" or so. I think the hole could be larger than the one I saw but I don't think anything like the one pictured above could be repaired. Well, I say that but I also say that in engineering anything is possible but costs rise as complexity increases. Yes, technically any destruction could be repaired, I just don't think in this case it would be worth the money involved.

[rtwpsom2]

So just a small update. Thanks to a good friend named Tom Kay up in America's Hat, I have access to the 3D scan he did of his own personal Merlin. It has helped immensely in the current area of work. I am currently doing the lower crankcase assembly, a.k.a. the oil pan. The shape of the forward slope wasn't well detailed in the blueprints and a little bit conflicting. So thanks to Tom's scan I have come out with a much more accurate shape.

In the first two images below you can see I have inserted the green scan into the model assembly. This is not a CAD model it is taken from a 3D point cloud and is merely a representation of the surface of the part as it was scanned with a handheld laser scanner.





In these two you can see how I used that scan to create the shape of the forward slope of the oil pan. This is the actual CAD part, it is a 3D "solid" that can actually be used in the manufacturing process if needed. (Which it probably won't but it's nice to dream)





Another exciting thing I wanted you guys to know about is that I have been doing some tests with my 3D printer and I have decided that in order to finance this project I am going to release a small line of aftermarket 3D printed engines in some larger scales for 1/24th and 1/32nd kits (among others hopefully) for kits that don't have really accurate engines in them like the Airfix Hurricanes and Spitfires that were first molded in the 70's, but remain popular large scale kits. Being that these 3D printed parts would be derived from this CAD projects, they literally would be the most accurate model engines ever produced. Here are a couple of test shots I did in 1/24th and 1/8th scale:





I was absolutely giddy when I saw the results of the 1/8th scale test shot, so now I also want to try printing a standalone kit in something like 1/8th or 1/6th scale of just the engine by itself. I am told it would be popular at least amongst a few people. You can see a larger gallery of the 1/8th scale crankcase here, and a gallery of the 24th scale one here. Sorry for the image size, this forum doesn't have any tools to scale it. Anyway, if you are interested in supporting the project and getting a copy of the 3D printed engines once the prject is complete, you can visit my patreon page. Thanks guys.

[Scott Rose]

Another exciting thing I wanted you guys to know about is that I have been doing some tests with my 3D printer and I have decided that in order to finance this project I am going to release a small line of aftermarket 3D printed engines in some larger scales for 1/24th and 1/32nd kits (among others hopefully) for kits that don't have really accurate engines in them like the Airfix Hurricanes and Spitfires that were first molded in the 70's, but remain popular large scale kits. Being that these 3D printed parts would be derived from this CAD projects, they literally would be the most accurate model engines ever produced. Here are a couple of test shots I did in 1/24th and 1/8th scale:

I was absolutely giddy when I saw the results of the 1/8th scale test shot, so now I also want to try printing a standalone kit in something like 1/8th or 1/6th scale of just the engine by itself. I am told it would be popular at least amongst a few people. You can see a larger gallery of the 1/8th scale crankcase here, and a gallery of the 24th scale one here. Sorry for the image size, this forum doesn't have any tools to scale it. Anyway, if you are interested in supporting the project and getting a copy of the 3D printed engines once the prject is complete, you can visit my patreon page. Thanks guys.

Neat idea... go for it. At some point if I can afford it I'll get one. Next project Daimler-Benz DB601/605?

[rtwpsom2]

Absolutely, as soon as you have gotten me those blueprints, I'm in.

[Spitty]

Absolutely, as soon as you have gotten me those blueprints, I'm in.

There is a page on Facebook,Db601 projects I think where Mickael is doing that at the moment to support his Bf109F project.Think he,s chasing BMW engine parts at the moment as well.

[exhaustgases]

What an excellent job. One of the best CAD models I have seen of an engine. Is this what you do for a living?

[rtwpsom2]

What an excellent job. One of the best CAD models I have seen of an engine. Is this what you do for a living?

No, I was working on airframes for a company that restored warbirds, but got let go due to covid slowdown. Currently job hunting. I'm doing this for fun. And to keep my skills up. But mostly for fun.

[Jim MacDonald]

Great work, Rob. Looking through your blog on this project really brings home the impressive amount of detail went into it.

BTW, I sent you a PM.

Take it easy,

Mac

[Brenden S]

I am so glad that your CAD model has now been printed in 3D. Well done and keep up the great work. I know a few people who would be interested in some of the printed engines. There is certainly a market for it.