Prop Balance and Murphy

On Mar 17, 6:52*pm, nrp wrote:
On Mar 15, 8:32 am, Peter wrote:

What also suprises me is how bad brand new props can be, despite
having been statically balanced *supposedly* very accurately.

In my life I've purchased two brand new McCauley fixed pitch props.
Both were substantially out-of-balance as they came out of the box,
and both were fixed by a local prop shop. *I am amazed the prop shop
(Maxwell) could do better given their comparatively crude tools. *Must
just be skill & attention to detail.

This flys in the face of the "FAA certified parts are perfect" theory.
One would think after spending several thousand dollars on a piece of
forged aluminum that might cost 200 bucks in raw materials that the
remaining costs are for the manufacturer to deliver a high quality
product. The fact that a local prop shop with crud tools can balance
it better then the manufatcturer is laughable......... JMHO..

Ben

wrote:
On Mar 17, 6:52 pm, nrp wrote:
On Mar 15, 8:32 am, Peter wrote:

What also suprises me is how bad brand new props can be, despite
having been statically balanced *supposedly* very accurately.
In my life I've purchased two brand new McCauley fixed pitch props.
Both were substantially out-of-balance as they came out of the box,
and both were fixed by a local prop shop. I am amazed the prop shop
(Maxwell) could do better given their comparatively crude tools. Must
just be skill & attention to detail.

This flys in the face of the "FAA certified parts are perfect" theory.
One would think after spending several thousand dollars on a piece of
forged aluminum that might cost 200 bucks in raw materials that the
remaining costs are for the manufacturer to deliver a high quality
product. The fact that a local prop shop with crud tools can balance
it better then the manufatcturer is laughable......... JMHO..

Ben

The same goes for the engine manufacturers. I put six new Millenium
cylinders on about a year and a half ago, all the pistons within 1 gram.
On a typical Continental they don't really care how much the pistons
weigh.

The same goes for the engine manufacturers. I put six new Millenium
cylinders on about a year and a half ago, all the pistons within 1 gram.
On a typical Continental they don't really care how much the pistons
weigh.

I don't have any love for Continental....But.....It is MUCH more important
to balance rotating parts than reciprocating.

"It is MUCH more important
to balance rotating parts than reciprocating."


I challenge that. Acceleration of a mass (or mass error) creates the
same dynamic force whether in a rotating motion or in moving in only a
translational motion. The only difference is that the force direction
is changing vs just reciprocating.

One gram may be overly accurate but it is something that is easily
achieved. I recall a Continental paper that said though that they
deliberately built up an engine with one pound (!) heavier piston & it
ran "satisfactorily".

Yeah, I'll bet......!

wrote:
On Mar 17, 6:52 pm, nrp wrote:
On Mar 15, 8:32 am, Peter wrote:

What also suprises me is how bad brand new props can be, despite
having been statically balanced *supposedly* very accurately.
In my life I've purchased two brand new McCauley fixed pitch props.
Both were substantially out-of-balance as they came out of the box,
and both were fixed by a local prop shop. I am amazed the prop shop
(Maxwell) could do better given their comparatively crude tools. Must
just be skill & attention to detail.

This flys in the face of the "FAA certified parts are perfect" theory.

That's a new theory to me. I thought FAA certified was
more about initial testing, documentation and accountability.