Real time continuous Prop balancing

This thread is not about how to balance a prop or shop balancing
machines.

Did anyone use BalanceMasters device bolted on their ultralight prop?

These devices apparently balance the prop continuously as you fly.
Similar devices are used on truck wheels - see www.BalanceMasters.com
and www.centramatic.com

abripl wrote:
This thread is not about how to balance a prop or shop balancing
machines.

Did anyone use BalanceMasters device bolted on their ultralight prop?

These devices apparently balance the prop continuously as you fly.
Similar devices are used on truck wheels - see www.BalanceMasters.com
and www.centramatic.com


Which raises the question if the prop is correctly balanced in the first
place why would you need dynamic balancing in an aircraft? It would seem
to me G forces would throw it off anyway.

Dan, U.S. Air Force, retired

In article Je9xf.78660$sg5.27262@dukeread12,
"Dan, U.S. Air Force, retired" wrote:

abripl wrote:
This thread is not about how to balance a prop or shop balancing
machines.

Did anyone use BalanceMasters device bolted on their ultralight prop?

These devices apparently balance the prop continuously as you fly.
Similar devices are used on truck wheels - see www.BalanceMasters.com
and www.centramatic.com


Which raises the question if the prop is correctly balanced in the first
place why would you need dynamic balancing in an aircraft? It would seem
to me G forces would throw it off anyway.

Dan, U.S. Air Force, retired

Maybe because balance changes with prop speed? I don't know anything
about the specific unit in question, but, in theory, an onboard real
time continuous balancer seems useful - at least for the fixed pitch
crowd.

I recently spent $250 for prop balance and it did not work. It was
still about .2 ips out. A factory prop is usually fairly close and all
it needs is a few grams to correct it.
Such a continuous balance device would also take care of imbalance as
the prop gets nicks and scratches. It might even help in flight with
accidental prop damage. These are some of the good reasons...

There are two things to consider in balancing a prop; mass balance and
aerodynamic balance. You can static balance a prop, but if the mass
distribution is not symmetrical, there will always be a V^2/r
unbalance. If the blades are not symmetrical in chord and pitch at each
station, there will be a force unbalance that will cause a whirl of the
engine on its mounts. This cannot be taken out with mass additions.

You are right about the pitch/cord aerodynamic balance problem. But
such a device would take care of the dynamic balance by far the more
common problem. When you take your prop for balancing to a shop they
only do the dynamic balance. You would have to return the prop to the
manufacturer for pitch/cord problems. But usually pitch/cord problems
are rare - its like having a bent wheel on a car, where most problems
are with dynamic balance.

"abripl" wrote in message
ups.com...
....
Did anyone use BalanceMasters device bolted on their ultralight prop?

These devices apparently balance the prop continuously as you fly.
Similar devices are used on truck wheels - see www.BalanceMasters.com
and www.centramatic.com

I'll give them an 8.5 on the bull**** scale.

I can rub your prop with a chicken bone to improve the strength for a lot
less money.

--
Geoff
the sea hawk at wow way d0t com
remove spaces and make the obvious substitutions to reply by mail
Spell checking is left as an excercise for the reader.

Actually, the pitch thingie is not all that uncommon. Consider: if your
prop has a 6" diameter hub, and the prop is mounted such that there is
a tilt across the long axis where one side is .01" off relative to the
other, one blade will be at 0.1 degree more pitch, and the other will
be at 0.1 degree less pitch. With CL slope being 0.1/deg, if the prop
blades are designed for a CL of 0.35, one blade will be at a CL of
0.34, and the other will be at a CL of 0.36. That's a 5.9% difference
in thrust between the two blades. You won't see this with tracking.
Let's say you have an airplane with an O-320 and are operating at 75%
power with a prop efficiency of 80% at 200 mph. Your prop is developing
180 lb thrust total; one blade is developing 87.4 lb thrust, the other
is developing 92.6 lb thrust. There is a 5.1lb differential between the
two blades, which tries to whirl the motor on its mounts. You will
never get the prop balanced, and the more thrust you develope, the more
shake you get. Been there, done that!

El.,

You are still talking about a manufacturing control problem or perhaps
worn CS gear problem. Both are solved by either returning the prop back
or replacing parts. I had similar issue with my IVO magnum prop (200hp
franklin) in which case an exchange of blades improved the situation.
Generally once you take care of that problem it does not return. But
dynamic imbalance can be a recuring problem - simple nicks or blade
wear will do it.

I'll give them an 8.5 on the bull**** scale...

Thank you for your technical help. I assume you have tried them
yourself and are giving an objective observation.