Saturday, February 10, 2018

Really Cool Model V-12 Engine

If you thought the supercharged V10 we talked about in September was cool; modeler mayhugh1 did a quarter scale V12 Merlin engine, based on some castings he was able to acquire.  The castings are gorgeous and the engine improved them.

The Merlin was the engine used in Brtain's famed WWII Spitfire fighters and then adopted into the US' P-51 Mustang.

Full build thread here. It's 84 pages, following the build from February of 2015 through November of '17, and this start up video is on page 80, dated August 28 of '17.

As for my next project, it's not that cool, but it's a step along the way.  I'm building a fire eater engine from the book The Shop Wisdom of Philip Duclos.  No castings will be involved, just pieces of metal bar stock.  There are a few videos of them in action; here's a short one.

These are known as atmospheric engines, vacuum engines, flame eaters, flame lickers, and I'm sure there are names I don't know.  I like to call them external combustion engines because of the little alcohol lamp outside the cylinder that powers them.  To start it, we flip the flywheel, and as the piston starts to move out of the cylinder, the engine sucks in the flame.  Expanding hot air helps push the piston away and a flap covers the input port keeping air from rushing in.  The air in the cylinder rapidly cools as it pushes the piston out and after the flywheel finishes that half rotation, the atmospheric pressure outside the cylinder forces the piston back toward the top of the cylinder (the reason they're called atmospheric engines), when the flap opens and allows the flame to be sucked in again.

Some of the videos feature someone trying to get the engine to run reliably for a couple of minutes, and I can imagine the inventors thinking, "if only we could get that combustion inside the engine, maybe we could get it to run more reliably.  Some kind of internal combustion..."  One of the model makers' websites says the first patent on one of these engines was granted to a Henry Wood in 1758.  That predates the Otto engine by a hundred years, which is generally called the first four stroke, internal combustion engine.


  1. Are these engines also Stirling engines, or is there a difference?

    1. The Stirling cycle is different than a flame eater engine. Stirling engines have two pistons, sometime with the pistons in different cylinders, and atmospheric pressure doesn't move them. Animated Engines probably has the best explanation of Stirling cycle engines.

  2. That Merlin was really a labor of love - gorgeous.

  3. The site is now bookmarked and I will be spending some time reading about the Merlin build.

    Jay Leno did about 20 minutes on the full size Merlin.

    Looking forward to your fire eater project.

  4. Next, I want to see a quarter-scale Merlin put into a 1/4-scale P-51.

    Bonus points if they have a manufacturer gin up some Class III .125 cal. MGs in the wing roots, even if they can only fire blanks.