The reduction drive’s pinion gear attaches directly to the Mazda 13B
crankshaft using the standard 10 to 1 taper and Woodruff key and a custom pinion nut. The
custom pinion nut uses standard ½ inch socket extension as driver and also acts as a
removal tool, pulling the pinion off the taper when the nut is removed for easy
disassembly. The pinion gear is differentially hardened for durability at the tapers and
hardness at the teeth. The 24 tooth pinion and 55 tooth ring gears provide a 2.29 to 1
speed reduction and use a high contact ratio tooth profile keeping more then 2 teeth in
contact at all times. The pinion is also connected to the flywheel with 10 to 1 taper,
Woodruff key and locknut. The end of the Pinion is supported by a roller bearing with an
axially free outer race which allows the pinion to float axially with engine crankshaft;
no thrust or bending loads are transferred to engine crankshaft or crankshaft thrust
bearing. Only torque is transmitted between engine crankshaft and pinion.The 55 tooth
internal spur ring gear raises propeller shaft almost 2 inches for improved propeller
clearance, resulting in an identical propeller centerline as Lycoming installations and
easier engine installation and cowling clearance. Lightening holes minimize inertia and
provide windage that generates and circulates an oil mist that lubricates the angular
contact propeller shaft bearings and pinion outboard support roller bearing. High-pressure
oil jets before and after the gear mesh create a hydrodynamic oil layer between gears for
lubrication and proper cooling of the gear teeth.
Powersport’s flywheel combines 4 functions into 1 part: flywheel, rear engine
counterweight, starter gear and ignition timing ring. The assembly is dynamically balanced
to within 3 grams, while Mazda specification allows up to 50 grams of imbalance. It
replaces the stock Mazda rear counterweight and starter ring which weigh 9 pounds and are
required with most other reduction drives when using the Mazda 13B engine, saving 9 pounds
of weight compared to the other drives.
The reduction drive’s propeller shaft uses a standard SAE-2 hub and is hollow to
allow for future use of constant speed propellers. It is tuned in length and thickness to
avoid torsional resonance within the Powersport RE-215 engine’s RPM operating range.
The propeller shaft uses duplex angular contact ball bearings to carry radial and
pusher or tractor thrust loads with very high efficiency, allowing them to
run cooler with decreased parasitic power losses. Bearing pre-load remains constant at all
temperatures. The propeller shaft housing’s bearing journals are machined with .006
inch eccentric to the mount centerline, allowing gear lash adjustment by removing housing
bolts and rotating the housing. This provides an easy way for customers to adjust gear
lash in the field with no special tools or disassembly if it is ever required
