Pratt & Whitney R-1830 Twin Wasp radial piston firing order

[airamerica1968]

Looking at the rocker arm covers on both the R-1830 and the R-2800 engines, it appears they cylinders are in line so that 9 thrust strokes would be the case. I note in the cylinders are offset (front from the rear) on the 3350 and of course, it is quite visible on the 4360. However, finding other photos of the engine blocks show they are offset too. It is only logical, that this would be the case as rwo cylinders tandem would provide a lot of asymmetry. I feel sure engineers considered all of this.

Has anyone noticed a "motorcycle" radial engine; the 9 cylinder XR600? Assuming it was made by adapting existing parts like the cylinders of the old Silver Wing engine, a 2 cylinder V-twin, my, my. Can you imagine hearing those if they were put into production? Harley's 2 cylinder would finally be largely eclipsed as to running sounds, eh? Made by a New Zealander (can anyone remember the Clisby V-6 prototype when V-6's were not yet production items?); it and this engine are "Down Under's contribution to reciprocating engines.

Sadly, turbines have replaced recips but some will still pursue this for years and I find it fascinating.

Another interesting consideration of aircraft motors is the degree arrangement of the cylinders. 90 degrees like the V-8 of the OX-5 (and also the V-10's) and 60 degrees in the Packard Merlin. Add the W and X configurations of other motors and it gets more interesting. I am sure the physics of reciprocating engines dictates these choices and while I am new to the site and have not searched for it, I would be interested in hearing from knowledgeables about engine reciprocating mass/crankshaft pulsation-physics involved.

Another interesting discussion would be about "throw spacing" as in 90 degree throws of some four cylinder engines vs. 180 degrees found in some and I see it is also mentioned for high performance engines that yield the high-pitched sound as in Formula 1 race cars.


Alas, sadly, turbines seem to rule except to motorhead aficionados.