216 G. J. Wennagel 
while the gear’s axial component is of maximum value. The hand of the spiral angle is such 
that the gear’s axial reaction is out of mesh, or to the rear, in direct opposition to the pro- 
peller thrust. This allowed for the use of relatively small propeller shaft thrust bearings, 
since the net bearing thrust load is the difference of these forces. Two thrust bearings are 
employed just forward of the propeller shaft seals. Two roller bearings straddle-mount the 
gear to provide radial reactions. 
Shafting in the upper gear box and the quill shaft are of 4340 stock with induction- 
hardened splines. The pod pinion drive shaft is of 4350 stock while the propeller shaft is 
of forged and age-hardened K-monel. The areas of seal contact on the transmission input 
shaft and propeller shaft are built up with a copper flash followed by a nickel flash and a 
hard chrome plate. 
Seals are of the double lip type and made of Sirvene 7080, a material chosen for its 
sea-water resistance. A single seal is used at the drive input with system lube oil 
depended upon for lubrication. Tandem seals packed with a sea-water-resistant grease are 
used on the propeller shaft. An interesting feature is that the pod structure is split horizon- 
tally along its longitudinal axis and bolted together on assembly. The pod machinery area 
is sealed by filling a machined groove, which runs along the periphery of each half, with a 
room-temperature self-curing, silicone rubber compound. 
Damage due to galvanic action has been controlled by careful selection of materials 
exposed to sea water. Like the propeller shaft, the pod seal carrier is of K-monel. A lock- 
ing ring, used to retain the seals, is cadmium plated. All lube and scavenge fittings and 
lube oil supply lines and grease fittings are of aluminum. To date, there is no evidence of 
erosion due to galvanic action. 
The lubricant used conforms to specification MIL-0-6086 (light). This is a petroleum- 
base aircraft gear oil containing extreme pressure additives. An electric pump in the lube 
supply system delivers two quarts of oil per minute at 20 psig. A pressure sensing switch 
has been incorporated in the supply line. If the pressure falls below 15 psig, this switch 
opens a return line from the engine fuel control to the fuel tank and engine shutdown is 
thereby automatic. A panel light then goes on to inform the pilot of the reason for engine 
shutdown. Total oil flow is divided by a tee located at the boat transom so that one quart 
per minute is supplied both to the upper gear set and to the pod gearset. Gear mesh and 
input shaft thrust bearings are pressure-lubricated in the upper gear box. Oil mist and oil 
flow by gravity lubricate the remaining gear box bearings, the spline couplings of the quill 
shaft, and the thrust bearing of the pod pinion drive shaft. A single lip seal directly 
beneath the pod pinion thrust bearing prevents leakage of oil to the pod. An oil scavenge 
port is located at the level of this seal to allow the return of the lubricant to the lube sys- 
tem. Needle bearings for radial load reaction on the pod pinion drive shaft are grease 
packed on assembly, and a grease fitting is provided to the uppermost of these bearings. 
A spray nozzle, to pressure lubricate the pod gearset, is located at the aft end of the pod- 
strut juncture. Oil mist is depended upon to lubricate the propeller shaft roller bearings. 
The pod is bored to give the effect of a shroud about the driven bevel gear. Dual channels 
run axially from below the gear to a sump just forward of the foremost roller bearing. This 
sump is shrouded to break up windage effects from a roller bearing locknut. The lubricant 
is then scavenged through drilled passageways up through the strut where connection to the 
lube scavenge system is made. Propeller shaft thrust bearings are grease packed and are 
provided with ring seals. Wash out of the grease packing by lube oil is prevented by slinger 
rings on the propeller shaft. Scavenge lines are joined at the transom into one line which 
continues forward. An electric scavenge pump returns the lubricant to a reservoir. An oil 
cooler has been found unnecessary and is not used. 
