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

[Jim MacDonald]

That's cool, Rob. I'm glad that you don't think that you will forget the sand molds!

Mac

[Scott Rose]

I think it's interesting so I hope you continue posting. If I thought you were spamming the forum I'd tell the owner

[rtwpsom2]

lol, thanks Scott, I appreciate it.

[rtwpsom2]

HEY STUDS!!!!

[rtwpsom2]

Woohoo!!! I've finished the Crankcase assembly!







You can read a little more about it on the blog and it's available for download on GrabCAD.

[Brenden S]

Looking great mate.

[DH82EH]

rt, that is some beautiful work.
Thanks for sharing it.
Really impressive.

Andy

[rtwpsom2]

Thanks, guys, I appreciate the support.

[rtwpsom2]

I've been working on the oil pan on and off for a couple weeks now but I don't have enough to post yet, but I thought I'd take advantage of my down time to upgrade my 3D printer. And of course, what is the first thing I have to print? Take a guess:

https://i.imgur.com/UPB3fkE.jpg

That's the easy way to see it, here's the hard way, sorry I can't make it any smaller.



It's currently an hour and a half into an estimates 44 hour print. Wish me luck. Say a prayer to the kami of 3D printers.

[ChrisAldridge]

One of my projects in mind is to build/3D print functional sub-scale cutaway versions of various aircraft engine models. The R-2800 might be first when I can get drawings. Keep moving forward with your project, if the print is unsatisfactory without support material.

[rtwpsom2]

Aaaaaaand Spaghetti.   Trying again with different settings.

Chris, I have been looking for R-2800 blueprints for years, now. If you ever find a source, let me know.

[Michel Lemieux]

Amazing work! Thank you for sharing!

Now....I do have to ask a stupid question.

Original cast were done with sand molds.

Would this ever be machinable from a solid billet with modern technologies?

The original cast parts had a lot of machining done afterwards. But what about starting from scratch?

I know this may sound stupid......but I am curious.

Cheers!

[bdk]

Would this ever be machinable from a solid billet with modern technologies?

It might be impossible to machine hidden coolant or oil passages in a machined part. Some of the internal features may also not be suitable for machining due to access. Perhaps some parts could be machined from billet. They would certainly be stronger than a sand cast part which typically has lots of porosity.

I'd be interested to know how the 3D model, made from drawings, compares to an actual part. Sand casting can be very imprecise at times.

[rtwpsom2]

No, I don't think this would be machinable in it's current form. There are a lot of areas that tools would never be able to reach. It's mostly hollow to make it as light as possible, and to be honest, I don't know how they can say with 100% certainty that they got all the sand out of it. If weight isn't an issue, you could probably make a few areas solid and machine it, but even then I am still not sure you'd end up with a functional crankcase. Fortunately, if you wanted to sand cast one, there are new tools out there that can 3D print sand molds.

Edit: sorry Michel, I typed all this out last night but forgot to hit submit.

[rtwpsom2]

I'd be interested to know how the 3D model, made from drawings, compares to an actual part. Sand casting can be very imprecise at times.

Fortunately, in this case, I had a 3D scan of an original -9 crankcase given to me by a friend named Tom Kay up in Ottowa. He owns one and had 3D scanned it and various other parts and he shared those scans with me. So in this case I can say with some certainty that the two are pretty darn close. There is a tiny bit of variance that you'd expect in sand casting, but the casters did a surprisingly good job of matching the drawings. That or the drafters did a surprisingly good job of drawing up the casting.