Engines Exposed: What is a Flat-Plane Crankshaft?

Cheatsheet ^ | 26 Nov, 2015 | Owen Brady

[o_1_2_3__]

It looks from the animation that the flat plane forces the cylinders to fire in groups of two...essentially making the motor a V-4. Or do I misunderstand something?

[virgil283]

"Did you know, today’s super carriers are faster than the WWII PT boats?"

That's true

I once saw CVA59 in dry dock and each of the three screws were bigger than a PT boat.....

[mad_as_he$$]

I saw that also. Very nice machine.

[virgil283]

Thanks for posting this- its all new to me.

"When the connecting rod journals are spaced 180 degrees apart, it leads to a long gap (relatively speaking) between combustions in the engine. By putting the journals only 90 degrees apart, the firing happens quicker, which makes each combustion less apparent."

So are there more power strokes per cycle or is it smoother power strokes ? anybody?

[biff]

I had one of those, convertible, white over black, red bucket seat interior, 4 speed. A really fun car for a kid at college in the late 60’s.

Of course, I wish I had it back, along with the 61 Bugeye Sprite, the 66 Charger, 64 SS Impala 4 speed black bucket interior and posi.

Oh well.........

[alloysteel]

The rotary design is no longer a reciprocating engine, it is sort of a flex-chamber turbine, with the compression being created by the changing shape of the torus around the central hub, the seals moving in and out to follow the surface of that torus.

Ingenious design, just that the materials used have a sort of dicey lifetime, especially the compression seals.

Madza used a smaller version in the RX-3, a sort of sub-compact, that seemed to wind higher and higher forever, on occasion well past 120 mph, which is clearly a white-knuckle situation in that small a vehicle. Had to be turning close to eight-nine thousand RPM at that speed, and it may have been capable of turning even higher.

Stupidity and bravery are at times indistinguishable.

[Jack Black]

I find this amusing because flat-plane cranks have been the norm on inline 4 motorcycles (most sportbikes, except Ducati's) and Yamaha recently made a big splash with a cross-plane crank in their R1 sport bike.

Yamaha Video on Cross Plane Crank

[Jack Black]

A more practical view from racers: Yamaha R1 Cross-Plane discussion/propaganda

[uglybiker]

Sorry, but the car and marine engines were COMLETELY different critters.
The V12 in the cars was a flathead displacing 473 c.i.
The marine V12 was all aluminum ohv displacing just shy of 2500c.i. and ran on airplane fuel.

In fact, the marine motor had more in common with the RR Merlin engine, which Packard also built under contract.

[Jack Black]

Cadillac V-16, the pinnacle of pre-war motor production.

Cadillac V-16