Evening star., 1942-09-11
Precision Required
To Give Propeners
Needed Balance
Three-Tenths Of Pound
Variable Allowed in
4l0-Pound Blades
By DAVID J. WILKIE.
Wide World.

Wide World.
LANSING, Mich, Sept 9.--Take
more than 100 pieces of material
ranging in size from half-inch pin
to huge blade of secret length, put
them through two to 200 machining
operations and finally At them to-
gether into a great variable pitch
aircraft propeller assembly as deli
cately poised as the balance wheel
on your watch.
That's what Nash-Kelvinator is
doing here in one of the most COM
plex volume production jobs the
one-time automobile industry has
undertaken.
From rough aluminium forging to
finished propeller takes about four
days but the completed assemblies
move out Of the factory by carloads
each day. Between the forging
stage and the final inspection, the
most unusual machine tools In the
industry combine with scores of
hours of hand work to achieve the
eXacting standards required to pro-
duce full feathering, three way pro-
pellers.
Before the War, propeners were
manufactured only by hand. Mass
production was held to be imprac-
ticable. Nash-Kelvinator combined
both methods. The results are seen
in the way the blades balance at
the final inspection.
Precision Necessary.
The layman usually thinks OF an
airplane propeller merely as a set
of blades fastened to central drive
shaft, and variable pitch" implies
little. But In the propellers being
made by Nash -Kelvinator for the
British and United States Govern
ments, the job requires great tech
nical skill. The hydraulic mech
anism which controls the pitch of
the blades and the balance between
the blades and the entire propeller
assembly demand just about every
thing the industry has in precision
capacity.
After each operation-on blade,
spider, dome, barrel or other unit
a workman moves the part to
bench where he tests it for static
balance. You see this at every sta
tion along the several lines to the
final assembly Always the workers
are weighing and measuring for
balance.
If part doesn't balance, some
excess material is machined of or
drilled out. If 1t is blade it is
placed on fiat table and measured
minutely at points or 4 inches
apart over its entire length; then
it is placed upright on another table
shrouded with a three-sided hous-
ing to prevent undue atmospheric
variable.
On another machine the blade is
Strengthened and twisted and again
the balance is measured A proflling
machine cuts down its thickness, and
once more the balance Is measured.
The profiling machine is one OF
the most intricate of the special ma
chine tools installed for the pro-
peller production job. One of its
vital parts is huge cam that con-
trolls the operational position of the
cutting tool that moves back and
forth across the surfaces Of the pro-
peller blade. The cam looks more
like a big bloom Of metal that took
its shape accidentally rather than
one Of the important precision tools
In the factory.
Like Wood w Working Machine.
EFF. ("Ernie") Keller, 49-year -old
master mechanic who Is factory
manager, ikens the profiler to an
old-fashioned type of wood working
machine. Mr.. Keller, native Of
Lansing. is at home in this partic-
ular factory, for he once was man
ager OF the place when REQ was
making Flying Clouds" and other
vehicles in the same structure.
Like all other workmen in the
factory, Mr.. Keller, who laid out
the equipment, talks constantly
about the balancing operations. All
through the factory you hear bal
ance balance :. balance g.. j.
until you begin to wonder whether
anything else is important.
But the reason for it all becomes
apparent when the completed pro-
peller assembly is tested for poise.
1t has to balance perfectly and it
does-to the point where the blades
on the whole 4l0-pound assembly
can be moved with a normal human
breath.
The final balance test is per-
formed by two workers who, with
q small overhead crane, place the
three-blade assembly on a perfectly
levelled and balanced temporary
axle. They swing a blade around
so that it rests at a As degree right
angle. Perfectly balanced, the blade
stands absolutely STILL
Each blade gets the same test.
Then the entire operation is re-