On Sep 23, 11:57 am, Tater wrote:
after looking at all the planes in the oshkosh museum, I saw a few
radials where the crank was stationary, and the rest of the engine
moved with the prop.

An engine with all the clyinders spinning around a stationary crank
(and the prop bolted onto the engine) is called a Rotary engine.
World-war-one vintage stuff.

The main reasons for thier usage in those early times was that the
engines of the time were big, inefficient, and rotated slowly, this
meant a couple of things, first is that they needed good cooling (esp
when the aircraft was on the ground) and second is that a plain radial
of the time (rotating crank) would introduce lots of nasty power-pulse
vibration due to the slow running and large combustion strokes. With
a rotary, the engine itself becomes an *enormous* flywheel which both
provides cooling for the cylinders even if the aircraft is stationary,
and also smooths out the power.

The big disadvantage is you effectively have built a massive gyroscope
onto the front of your plane, which radically affects the handling, if
you move with the gyro then the effect can be used to your advantage
(if it doesn't take you by surprise first!), but that big engine only
spins in one direction so moving against the gyro causes some issues.
And of course when you open the throttle and the engine starts
spinning faster, your whole plane is going to have a very distinct
notion to roll over with the engine.

As engine technology improved (fairly rapidly), the advantage of a
rotary (spinning engine) over a radial (spinning crank) waned and
radials took over.

Radials are not common in modern aircraft having been surplanted by
inline engines, however they do still find favour in certain
applications (bush flying for example) due to thier relative
simplicity and therefore reliability (if treated right).