Engine configuration

"Certain types of V engine have been built as inverted engines,
most commonly for aircraft. Advantages include better visibility
in a single-engined airplane, and lower centre of gravity."

An aluminum V8 was adapted in the 1960s to power ---I want to say the
Whittman Tailwind, but I could be wrong --- it was run direct drive and
inverted. Ran fine for many years. One problem was that the oiling system
had to be redesigned. It was originally designed to pump oil up into the
valve covers, then let it drain back down. Obviously that won't work if the
whole engine is upside down. Also the carb had to be replaced (float bowls
don't work upside down either.) Neither change is trivial, both are do-able.

You can see why it would result in a lower center of gravity - the crank
(directly connected to the prop) becomes the highest point on the engine
instead of the lowest. Same for visibility - the whole engine is lower and
out of the way.

But that all assumes you are going to use it direct drive - which almost
nobody does. If you use a gearbox, belt PSRU, or HiVo chain PSRU, they will
all give you an offset of several inches, making for the same center of
gravity without the other changes, and allowing for much greater power,
because engine RPM's can be run much higher for the same prop RPM.

"Ron Webb" wrote in message
...


"Certain types of V engine have been built as inverted engines,
most commonly for aircraft. Advantages include better visibility
in a single-engined airplane, and lower centre of gravity."

An aluminum V8 was adapted in the 1960s to power ---I want to say the
Whittman Tailwind, but I could be wrong --- it was run direct drive and
inverted. Ran fine for many years. One problem was that the oiling system
had to be redesigned. It was originally designed to pump oil up into the
valve covers, then let it drain back down. Obviously that won't work if
the whole engine is upside down. Also the carb had to be replaced (float
bowls don't work upside down either.) Neither change is trivial, both are
do-able.

Steve Wittman's plans for the conversion are still available, or were a year
or so ago, from Aircraft Spruce. Several of the V6 engines which have been
produced much more recently have similar torque and displacement--so they
may also be possiblilities in the 200 to 260 CID range.

You can see why it would result in a lower center of gravity - the crank
(directly connected to the prop) becomes the highest point on the engine
instead of the lowest. Same for visibility - the whole engine is lower and
out of the way.

But that all assumes you are going to use it direct drive - which almost
nobody does. If you use a gearbox, belt PSRU, or HiVo chain PSRU, they
will all give you an offset of several inches, making for the same center
of gravity without the other changes, and allowing for much greater power,
because engine RPM's can be run much higher for the same prop RPM.

I agree in principle. It's really the builder's choice of compromises--just
as it is for the designers of certified engines and certified airframes.

Ron Webb wrote:
"Certain types of V engine have been built as inverted engines,
most commonly for aircraft. Advantages include better visibility
in a single-engined airplane, and lower centre of gravity."


An aluminum V8 was adapted in the 1960s to power ---I want to say the
Whittman Tailwind, but I could be wrong --- it was run direct drive and
inverted. Ran fine for many years. One problem was that the oiling system
had to be redesigned. It was originally designed to pump oil up into the
valve covers, then let it drain back down. Obviously that won't work if the
whole engine is upside down. Also the carb had to be replaced (float bowls
don't work upside down either.) Neither change is trivial, both are do-able.


As I recall, Wittman said big problem was that the engine ate plugs in
the inverted position. Barely get 20 hours on a set...



You can see why it would result in a lower center of gravity - the crank
(directly connected to the prop) becomes the highest point on the engine
instead of the lowest. Same for visibility - the whole engine is lower and
out of the way.

But that all assumes you are going to use it direct drive - which almost
nobody does. If you use a gearbox, belt PSRU, or HiVo chain PSRU, they will
all give you an offset of several inches, making for the same center of
gravity without the other changes, and allowing for much greater power,
because engine RPM's can be run much higher for the same prop RPM.



And what does all that do to 1) weight and 2) CG ???

On Dec 20, 12:03 am, cavelamb himself wrote:
snip
But that all assumes you are going to use it direct drive - which almost
nobody does. If you use a gearbox, belt PSRU, or HiVo chain PSRU, they will
all give you an offset of several inches, making for the same center of
gravity without the other changes, and allowing for much greater power,
because engine RPM's can be run much higher for the same prop RPM.

And what does all that do to 1) weight and 2) CG ???

1) A PSRU gives a smaller faster engine, which is usually lighter even
with the weight of the reduction gear.
2) Raising the output shaft several inches is the same as lowering the
CG, and the bulk of the engine that spoils your view, the same amount.

John halpenny

"Charlie" wrote in message
. ..
Actually, there is a real structural advantage to the flat engine over the
V. The block can be lighter in the opposed configuration, for the same
strength.

Charlie

That's both true and, now that you point it out, relatively obvious. The
through-bolts take most of the loads so the case itself can be quite thin
and light. Something not possible with other configurations.

I wonder why I didn't think of it. Thanks for pointing it out.

Bill Daniels