On Fri, 12 Dec 2008 12:41:33 -0800 (PST), "
wrote:


blades. The 'truth' of the jig is determined by placing a straight-
edge across the pair of knife edges and using a precision protractor
or level to ensure the blades are level. Nowadays, if you have the
money, you would probably use a digital protractor, most of which are
accurate to a tenth of a degree. Or you can use the old fashion
method which consists of a carpenter's framing square, a bit of thread
and a plumb-bob.

The point that needs to be made here is that your propeller balancing
tools are something you will use periodically, not just when you carve
a propeller. Just as you keep a set of tools specific to your landing
gear tires and wheels, so too must you keep a kit of tools specific to
balancing your prop.

-R.S.Hoover


what I'm about to tell you is illegal in the country of origin but I
do it once or twice a year because to not do it is stupidly dangerous.

honestly you dont need planer blades.
I use two 6 or 8 inch wide hardwood plank sections that have been
dressed all round in a commercial planer.
the pivot of my balancer is a polished half inch diameter rod that was
originally a part of a photocopier.

I have machined from half inch 6061 aloooominum two tapered conical
sections that achieve a jamb fit in each side of the propeller boss
hole and are a slop free slide fit on the shaft.

The principal requirement in machining these conical sections is that
all machining is done at once without taking the workpiece out of the
lathe, that way the entire component cant help but be precisely
concentric.

in use I sit the two boards on the kitchen table after giving them a
dust off. I use a torpedo bubble level to check that the tops are
level. The rod is fed through the middle of the prop and the two
conical sections are fed over the rod and jambed into the prop's
central hole.

I sit the assembly on top of the boards, close all doors and windows
to prevent any slight breezes, and wait for the heavy blade to
descend. it is sensitive enough that a quarter of a typical 'post it'
note gummed on the end of one prop blade will make that blade descend.

I add paint or varnish from a rattle can to achieve balance. allow it
to dry a few hours then recheck.

using this technique I achieve a vibration free engine installation
for months on end.

btw there is no point in using different length screws on the spinner
and expecting the thing to remain balanced.

if you have a wooden prop and you maintain it you will have something
that can outlast the airframe.

Stealth Pilot