The engine study in 1968
revealed that the three main bearing VW crankshaft
design was not suitable for the larger 2100cc
engine project. In order to deal with the high
stress created by the torsional and gyroscopic
forces, a four main bearing crankshaft would be
required.
The design also had to eventually
include the installation of a series of variable
and constant speed propellers with varying weights
up to 23 lbs.
The production crankshaft flanges
were to be machined from an E4340 forging. A large
area 3° locking taper was chosen as the method
to connect the flange to the crankshaft without
keyways or splines. The locking taper area had
to extend into the larger section of the crankshaft
nose so that the forces would not be concentrated
onto the smaller section near the edge of the
crankshaft. By doing so, this would eliminate
the distributor drive gear lock ring and spacer
which were no longer needed.
The outside diameter of the
shaft end of the flange provided the fourth main
bearing journal. The fourth engine bearing was
to be cast out of aluminum bearing alloy. A one-piece,
ring type design was required; two internal rotary
seals for propeller oil control and one outboard
lip seal for internal and external sealing.
The design called for the flange
to be pressed onto the crankshaft via 3/4"
left-hand threaded bolt at a torque value of 150
ft. lbs. For flange removal, a set of internal
threads were provided which allows for a puller
bolt to be threaded in to contact the nose of
the crankshaft. This would allow the removal of
the unit without deforming the O.D. of the flange.
The actual flange dimensions
for mounting the propeller hub were integrated
from the SAE standard #1 which also meets aeronautical
standard 127-A. These same standards were used
by Continental and Lycoming on their smaller engines.
Another design requirement was for the propeller
disc to be located far enough forward so it did
not compromise the exhaust and cowling installations.
The R-2100D-CDI engine manufactured today still
uses this design. Next...
