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Race Engine Technology Magazine

The Mark-11 PSRU was designed to provide a high-reliability, modest-cost chain-drive PSRU, which had the offset and torque capacity features which make it attractive to replica-fighter builders who want to use a GM or Ford V8 engine. We decided against producing it because of the inherent superiority of our geared reductions, and because of a very limited market for this product.

The following text describes the capabilities of the design.

The Mark-11 had two different input torque capacities: 550 lb-ft. and 700 lb-ft., and was designed for the Smallblock or Bigblock Chevrolet engine as well as the 460-Ford engine configurations. Power transmission was implemented with a Hy-Vo™ chain, which provides propeller rotation in the same direction as the engine.

The Mark-11 had a vertical distance between the crankshaft and propshaft centerlines of 8.0 inches, and provided a wide selection of reduction ratios in the same package. It contained the proven reliable technology (component design, load-bearing, lubrication, cooling and vibration) as the Mark-9, and had the simplification and maintenance improvements developed in the Mark-10.

The specifications were:

1. Minimum weight was approximately 78 pounds;
2. There was a medium and high input torque version: 550 and 700 lb-ft.; both had a thrust capacity of 3000 lbs;
3. It had an integrated, gear-driven governor pad (AND-20010) with internal control plumbing, designed to accommodate a standard Woodward or Hartzell single-acting prop governor.
4. It included provision for a reversing prop and the beta-feedback mechanism for reversing control;
5. It provided reduction ratios ranging from approximately 1.85 to 2.55;
6. It was designed to withstand the very high gyroscopic loads imposed by the propeller during sudden maneuvers, gusts, or aerobatics.
7. It was designed to provide either of two high-capacity prop-flange configurations:
   --- ARP-880, the 8-bolt, 2-dowel configuration used on the PT-6 and TPE-331 turbine engines, and most GTSIO-520 engines;
   --- ARP-502, the 6-bolt, 2-dowel configuration used on some Lycoming and Continental engines, including certain GTSIO-520 models.

No prototype was built, and we do not intend to build any because of the inherent superiority of our geared reductions drives. The reasons for that superiority are discussed in specific detail HERE and HERE.