Prop Clocking Matters

"Dale Alexander" wrote in message
...
I went to Lycoming school several years ago. One of the memorable items
mentioned was that if an owner re-clocks the prop to make hand-propping
easier, cracks in aluminum brackets and filament failures in instrument
bulbs most likely would result. The instructor mentioned that this was due
to a high frequency vibration (one that the pilot may not notice) that
would
result from an out-of-balance condition. His moral to the story, if these
conditions exixt on your plane, check the index position of the flange
master dowel to the prop. Your combination was out-of-balance enough to
notice before failures began.

Dale Alexander

It really is not my specialty, and I do not know in the case of aircraft
engines, or for current production automotive engines, but it was common for
manufacturers not to "zero balance" a lot of the older automotive engines.
That means that the flywheel was heavier on one side because it acted as
either all, or more likely part, of one of the crankshaft balance weights.

Just a little "food for thought."

Peter

"Peter Dohm" wrote

It really is not my specialty, and I do not know in the case of aircraft
engines, or for current production automotive engines, but it was common
for
manufacturers not to "zero balance" a lot of the older automotive engines.
That means that the flywheel was heavier on one side because it acted as
either all, or more likely part, of one of the crankshaft balance weights.

That is now part of the function of the harmonic balancer, on today's auto
engines.
--
Jim in NC

On May 4, 5:01 pm, "Morgans" wrote:
"Peter Dohm" wrote

It really is not my specialty, and I do not know in the case of aircraft
engines, or for current production automotive engines, but it was common
for
manufacturers not to "zero balance" a lot of the older automotive engines.
That means that the flywheel was heavier on one side because it acted as
either all, or more likely part, of one of the crankshaft balance weights.

That is now part of the function of the harmonic balancer, on today's auto
engines.
--
Jim in NC

Sometimes. Many of them aren't heavy on one side. The
"harmonic" part comes from the fact that it's two pieces of metal, an
inner hub and outer ring, with rubber between them. The rubber-mounted
ring (pulley) dampens the high-frequency vibrations created along the
crankshaft, or "ringing," that can cause catastrophic crankshaft
failure if its amplitude happens to increase at some resonant RPM.
It's there to "detune" the crank. Short, stiff cranks usually don't
need them.

Dan

Dan_Thomas_ wrote

Sometimes. Many of them aren't heavy on one side.

I'm not surprised. The engines I am most familiar with are weighted, but I
don't have much exposure to a lot of engines. I should have used another
weasel word like "some of."

The "harmonic" part comes from the fact that it's two pieces of metal, an
inner hub and outer ring, with rubber between them.

Right, which is why I said "part of the function."
--
Jim in NC