It's cute, but it's not an engine. There's just air coming in through the straw that causes the piston to go up and down.
We don't call air tools (such as impact wrench) engines.

Energy is neither created nor destroyed. A V8 converts gasoline into CO2, water and heat which increases pressure within a cylinder and in turn propels a piston that moves the car. This uses air to move a piston (and could be used to move a car). Gas = air in this example.

At 1:50, they appear to be making the cylinder hole larger. They would then either 1)buy new pistons to fit the larger bore or 2) if they just took off a tiny bit to remove a scratch and it's still within tolerance they could just reuse the old pistons with new rings. In this case, those certainly looked like new pistons, which should be matched to the bore they just cut. Notice at 3:48 you can see ".030" stamped into it, which likely means .030 inches over stock.
At 2:05, I think they are 'dressing' the bore, which puts a cross hatch pattern in the cylinder wall that helps the rings seat and seal.

As to your side note...it's a style choice. Some people love the old, stock, unrefinished body paired with new running gear for a car that looks like junk but runs like a top. At least that's my guess...and that's how both of my cars are built.

So here's a question. When they redrill the holes at 1:50 and 2:05, does it not make the bore bigger and therefore allow more gas to escape the pistons?
Side note, I have to wonder why they didn't restore the truck itself while the engine was out being rebuilt.

Thanks for that, makes me feel better about getting them confused since the terminology is semi-fluid.

Seeing the disassembled Wankel engine in the video should have clued me in that that was NOT what was used in the P-47, which had lots of big cylinders for pistons radiating around a central point, hence the "radial" designation.

It (the video) was very helpful for figuring out how the chambers and path of the parts work in comparison to a piston engine, which is quite interesting even for someone like me who really only understands the rudiments of either design. Live and learn!

Whoops -- I screwed up.

P-47 had a *radial* engine (with pistons), but not a *rotary* engine.

So I guess I was reading too much into the advantages of rotary engine coinciding with the advantages of the P-47.

I'll leave my post above unedited and own my brain-fart, but I hereby own up to being all wet and wrong about it!

The main advantage, power to weight...this one is HUGE for performance vehicles. Also in it's favor; reduced vibration (over piston engines), only two moving parts, no valve train, and the fact that it's 'exotic'.

EDIT: Cons: terrible mileage, bad emissions, loud (it's can't handle much back pressure, so you can't put on much of a muffler, and the unburnt fuel 'pops' loudly as it leaves the exhaust), hard to replace Teflon seals requiring a full teardown to replace, hard to find a mechanic that can work on them (especially if you need machining done), hard to find period (they're quite 'rare' compared to piston engines)....I'm sure there's more I'm forgetting or don't know.

I can't argue with a single thing he said, but for a power to weight ratio, the rotary can't be beat by pistons.
For an insane story about how it was conceived, you can't beat the Wankel period.

That was cool!
Was anyone else surprised at the amount of wobble in the bolt/piston? I couldn't believe that, with that amount of wobble and deflection, (seen clearly when they remove the upper portion of the tube it rides in) that it could still work at all, much less at speed....but it does. Impressive.
(and yes, I do see clearly that it wobbles more with that tube removed...but it still had some wobble with it there, and more astonishing, it still worked with it gone...again, impressive!)

Hi @lucky760, I have a yt video that has 48 seconds of content followed by 100 seconds of black... so I went to put in an &end=48 tag into the iframe embed (which I'm sure I've seen work before).

siftbot didn't remove it on validate embed, but did remove it when I submitted the post... any chance of a fix?

Vid in question is Engine-Inspired Watch tells time with a Piston.

A rotary (Wankel) engine has a triangular device that acts as the piston, which rotates in a chamber close to a figure 8 shape. Each side of the triangle acts as it's own piston as it rotates, first intake through a port (no valve) then compression, detonation, expansion, and finally exhaust through another port (still no valve).
Radial engines (what I think you meant) are relatively normal piston driven engines where the pistons are arranged in a circle around the crank at a 90 deg angle from the cranks rotation. These are usually used in prop driven airplanes.
This motor arranges the pistons in the same orientation as the cranks rotation...a 90 deg difference from radial engines. This makes it far more compact, but also puts the pistons in a single, rotating, revolver like arrangement of cylinders. It's a bit of a combination of rotary and radial engine features.

I'm not sure how much credence I can give the wiki page...I note it claims things that are obviously wrong, like "the design does not have a long lifespan when compared to other engine designs due to large numbers of moving parts" while in fact this motor has far fewer moving parts than normal motors. It did make some good points, like the first one that occurred to me about friction, but also made some bad points such as claiming 'mechanical complexity' as a drawback, while in fact it seems far more simple than normal motors.
"extra complicated machined parts" also exist in normal motors, and can be made fairly cheaply and easily in bulk.
Excess use of oil is an issue, but one they should be able to solve with proper machining and materials. Low RPM is fine for many applications, like a generator, so long as it's efficient it's fine and might even be better. Since you get high torque at low RPM with this design, low RPM seems to be ideal.
They claimed it had comparable horsepower to the same displacement normal motors in the prototype...if true, that point is moot.
Actually, there seems to be less moving mass in this motor, consider the mass of the crank shaft and counterbalances, connecting rods and pistons, the camshaft, rods, lifters, rockers, and valves. This motor only had a compact 'crank' and the connecting rods and pistons, and the output shaft. That's less actually moving to my eye.
The 'potential for explosion' was claimed on Wiki to be a design flaw of the case thickness around the 'crank', which could easily be thickened if it doesn't have to fit inside a torpedo....potential removed.
I'm not saying it's perfect, or necessarily even feasible, but it does seem to have more going for it than you give it credit for and is worth following it's progress to me.

Sure, yea, right now it is, but the way things are going it's not far of that a majority of new cars are going to be electric or at least partly electric, especially since this technology is still a bit off.
I like the Free Piston Engine Linear Generator better since it's literally only one moving part (save for the myriad of pumps, valves and other assorted crap all engines have) and has a small size, but it will also be a stopgap measure on the road to pure electric.
And sure this might end up in a few specialized vehicles, but it won't revolutionize anything.

If a large percentage, or at least a majority of cars were now electric, I would agree. But they are not. Because internal combustion engines are still the norm, even in hybrids, making one that's more efficient and lighter with fewer parts is a great idea.
Don't let the great be the enemy of the good.
I wonder how they deal with centrifugal force when it runs at high speeds, it seems like the piston would ride the cylinder wall, creating major friction and heat. Maybe I missed something.

So it's basically a Gatling style engine.
It would have been great if introduced 10-15 years ago, but as cars and other vehicles are beginning to switch to electric drive a Free Piston Engine Linear Generator is more appropriate for cars as a range extender.