- EPI's Gearbox Products -
Propeller Reduction Units (PSRU), Helicopter Transmissions,
EPI's first PSRU evolved from our original Engine Development Program (see Aircraft V8 Development). The design and development of the EPI powerplant (engine, PSRU, and aircraft accessory drives) was the subject of a technical presentation which EPI's CEO gave at the 1996 Advanced Engine Technology Conference (AETC).
The unparalleled success and reliability of that first gearbox (the Mark-9) led to the design and development of several other products, including helicopter and turbine engine gearboxes, and the current Mark-15 PSRU.
All EPI transmissions are designed with special attention paid to reliability, the minimization of gear-tooth dynamic loads, and to the isolation of the driven components from engine torsional excitation. They incorporate proprietary vibration-stopper coupling system technology between the engine and the gearbox which attenuates to near-zero the amplitude of the torsional vibration forces generated by the engine.
We do that by designing the engine-gearbox-propeller system so the PSRU gears, output shaft and propeller feel less than 1% of the engine torque pulsing. For a clear presentation on this vibration technology, follow these four links, in order: Part 1, Part 2, Part 3, Part 4.
In addition to our vibration-stopper technology, all our transmission designs are based on a severe-service load model for the intended application, which includes loads from the following sources:
- the bearing, shaft and housing loads produced by:
torque, thrust, gear separation forces, and propeller gyroscopic moments;
- the gear loads from mean engine torque ("STATIC loads");
- the gear loads from the system dynamics, which can be many times larger than the static loads;
- the cooling load imposed by the power transmitted;
- the lubrication requirements;
- the propeller control system (governor) requirements (if applicable).
A SEPARATE SECTION OF THIS SITE CONTAINS A COMPLETE PRESENTATION
OF THE FACTS ABOUT PROPELLER GEARBOX TECHNOLOGY.
Before making a PSRU selection, we HIGHLY ENCOURAGE you to
read through the PROPELLER GEARBOX TECHNOLOGY section.
The Mark-15 gearbox is our current high-power (up to 1600 lb-ft input torque) Propeller Reduction Gearbox. It is a geared reduction unit, available in either single-mesh or two-mesh versions. The Mark-15 incorporates the proven technology of the Mark-9, with several improvements which are designed to simplify the manufacture of the unit.
FEATURES: The Mark-15 has a vertical propshaft offset of 7.9 inches, an input capacity of up to 1600 lb-ft of torque, and can be configured to provide propeller rotation in either direction, regardless of the engine rotation. As the result of a new housing design, we can produce this gearbox to fit many different engine configurations and types. At present, the housing for this gearbox can be machined to fit the LS1 / LS2 / LS7 engines, the standard Chevy Small-block and Big-block engines, the Ford Windsor and the Jaguar V-12 "middle" and "late" block designs.
In September of 2012, a special version of the Mark-9 PSRU competed in the Reno Air Races Gold Sport Class in Lee Behel's GP-5, named Sweet Dreams. It qualified at 363 mph, finished third in two of the heat races and finished fourth (359.6 mph) in the Sport-Gold race. For a detailed description of this gorgeous, successful V8-powered race airplane, CLICK HERE.
The Mark-9 gearbox is a two-mesh, geared reduction unit, with a vertical offset of 6.125 inches. It was our first gearbox to use hydrodynamic bearings, thereby dramatically reducing the gearbox weight. Because of renewed interest following the 2012 Reno Air Races, we are working on a new housing design, fully CNC-machined from billet, and plan to make the Mark-9 available again for lower-powered (up to 750 lb-ft input torque) engine conversions.
The Mark-9 was used by EngineAir Power Systems on their firewall-forward, liquid-cooled 440HP turbocharged V8 engine package. The Mark-9 has been flying on several Lancair 4-P aircraft, some approaching 1000 flight hours, and is installed on several other experimental aircraft which are still under construction.
The Mark-10 gearbox was a single-mesh, geared reduction unit which was intended for the EPI certifiable engine package.
STATUS: The Mark-10 has been replaced by the more flexible, higher-capacity Mark-15.
The Mark-11 gearbox was a chain reduction unit specifically designed for a customer building a "replica-fighter-with-big-V8-engine".
STATUS: No prototype was built, and we do not intend to build any because of the inherent superiority and lighter weight of our geared reductions drives.
The Mark-12 gearbox was a planetary geared reduction unit which was intended for a new, 300-HP flat engine which EPI was developing.
STATUS: The gearbox is in the preliminary design phase. Work on that engine program has terminated, and no prototype hardware has been built.
The Mark-14 gearbox is a four-mesh special-purpose geared reduction unit which was designed to connect TWO turbocharged V8 engines to a single propeller. The two engines are mounted behind the pilot and connected to the nose-mounted gearbox by two specially-designed driveshafts. Each gearbox input has an overrunning clutch to allow either engine to be stopped while the other continues to power the aircraft. This gearbox was intended for a new Reno-Racer aircraft as well as a possible high-performance kitplane.
STATUS: The Mark-14 is in finished design form, complete with engineering drawings. Several components of the prototype gearbox have been manufactured. Work on this project stopped in mid-2003 due to the unfortunate death of the client's financial backer.
The Mark-16 gearbox is a single-mesh special-purpose gearbox, specially designed for a client who was planning a new aircraft targeted at for heavy-hauling in "bush-flying"applications.
STATUS: This product was proprietary to the client who contracted the design. The restrictions have now expired, and the design, or a derivative design, are available.
The Mark-17 gearbox was designed to bolt directly to the power section of the 49-pound, 150 HP SOLAR T-62T-32™ turbine engine and, together with the Mark-18 Main Drive Gearbox, to convert the RotorWay Exec series of helicopter from its fragile piston engine to smooth, reliable turbine power. This gearbox includes an extreme-capacity autorotation clutch anda 6-disc wet hydraulic clutch to allow the turbine to start load-free, then smoothly pick up the rotor loads.
STATUS: The design of this product is essentially complete, with 3D-CAD components and assemblies, complete analysis calculations, engineering drawings, and some components already manufactured. This product (and the Mark-18 as well) has been acquired by a client company to provide the powerplant basis for a new helicopter product currently in development.
The Mark-18 gearbox is a high-capacity 90° gearbox-with-main-rotor-brake for the main rotor drive on the RotorWay Exec series of 2-place helicopters. The Mark-18, together with the Mark-17, was intended to provide a bolt-in system to replace the notorious 4-cylinder piston engine and drive system in the with a reliable 150-shp turbine engine system.
STATUS: The design of this product is essentially complete, with 3D-CAD components and assemblies, complete analysis calculations, engineering drawings, and some components already manufactured. This product (and the Mark-17 as well) has been acquired by a client company to provide the powerplant basis for a new helicopter product currently in development.
The Mark-19 gearbox is a compact six-mesh gearbox which uses TWO very-high-powered, turbocharged piston engines to drive a single propeller. The two engines are mounted ahead of the pilot and connected to the nose-mounted gearbox by two specially-designed driveshafts. This gearbox was designed specifically for a client who was building a potentially Reno-Winning race plane.
STATUS: This product is proprietary to the client who contracted the design.
The Mark-20 gearbox is an indistrial gearbox which uses the 49-pound, 150 HP SOLAR T-62T-32™ turbine engine to drive both a 100 HP air compressor and two high-pressure hydraulic pumps. This unit forms the basis for a very lightweight mobile power unit which can be easily transported by helicopter, for the purpose of geological explorations.
STATUS: This product is proprietary to the client who contracted the design.
The Mark-21 gearbox is a special-purpose gearbox, specially designed to adapt the ALLISON B250-C20™ turbine engine into a popular helicopter. It mounts directly to the B-250, without exceeding the engine limitations. It has its own lubrication system and oil thermostat for controlling oil temperature. It includes an extreme-capacity autorotation clutch.
STATUS: This product was, for a limited time period, being held as proprietary to the client who requested but failed to fund the project. The design is now available to any interested client for completion of the design and prototype development.