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Race Engine Technology Magazine

From our inception, EPI had done several gearbox preliminary designs, but our first physically-implemented gearbox evolved from our original Aircraft Engine Development Program (see Aircraft V8 Development). The design and development of the EPI powerplant (engine, Propeller Speed Reduction Unit ( "PSRU"..... {ugh} }, 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 (the Mark-25), gearboxes to adapt high-end engines to existing dynamometer facilities, and our most flexible PSRU, the Mark-15.

NOTE that, as of 31 March, 2018, EPI, Inc. has ceased all manufacturing activities and is concentrating on design and analysis work. Therefore, the gearbox units described here are no longer available from EPI.

HOWEVER, we are working on arrangements with a different manufacturing organization to make available an upgraded version of the Mark-9, and an upgraded version of the Mark 15, which has improved gearing and a 7.7 inch vertical offset (instead of the 7.9 inch vertical offset of the Mark-15,) named the Mark-26 (webpage coming soon).

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 and driven-load torsional excitation. They incorporate our proprietary vibration-stopper coupling system technology between the engine and the gearbox, which attenuates the amplitude of the torsional vibration forces generated by the engine to nearly-zero.

We do that by designing the engine-gearbox-propeller/rotor/dyno SYSTEM so that the gears, output shaft and driven load 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:

1. the bearing, shaft and housing loads produced by:
          torque,  thrust,  gear separation forces,  propeller gyroscopic moments,
          driven load mass moments of intetia;
2. the gear loads from mean engine torque ("STATIC loads");
3. the gear loads from the system dynamics, which can be many times larger than the static loads;
4. the cooling load imposed by the power transmitted;
5. the lubrication requirements;
6. the propeller control system (governor) requirements (if applicable).

A SEPARATE SECTION OF THIS SITE CONTAINS A COMPLETE PRESENTATION
OF THE SCIENCE INVOLVED IN PROPELLER GEARBOX TECHNOLOGY.

Before making a Propeller Gearbox selection, we HIGHLY ENCOURAGE you to
read through the PROPELLER GEARBOX TECHNOLOGY section.

As a bare minimum, we encourage you to read the PSRU  FAQ's and < a href="../propeller_reduction_technology/gearbox_summary.htm">SUMMARY pages
before deciding on ANY Propeller Gearbox.

EPI GEARBOX PRODUCTS and DESIGNS

MARK-27 VW Engine Co-Axial Gearbox

The Mark-27 gearbox is a new (2021) co-axial planetary gearbox designed specifically for high-output VW-based engines.

This gearbox provides a 1.474 reduction ratio, suitable for an engine that can produce 120 HP at 4000 RPM, and drive a propeller at 2714 RPM.

SEE more information about the Mark-27 System

MARK-25 Helicopter Transmission

The Mark-25 gearbox is a new (2019), complete turbine-helicopter power transmission system which couples a new 185-hp turbine engine to the main and tail rotors of a new, 2-place European helicopter currently in the certification phase of development.

This gearbox reduces the engine output (62,000 rpm) to the main rotor rpm (520) and the tailrotor rpm (5000), includes a robust hydraulic clutch to disconnect the rotor load from the engine during startup, and provides accessory interfaces for the main oil pump, a high capacity alternator, and the engine starter system.

SEE more information about the Mark-25

HIGH CAPACITY PSRU: MARK-15

The Mark-15 gearbox (no longer available) was our 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, this gearbox was available to fit many different engine configurations and types, including the GM LS - LT series engines, the standard Chevy Small-block and Big-block engines, the Ford Windsor, the early and middle Chrysler Hemi, the Jaguar V-12 "middle" and "late" block designs, and the BMW-M73 V-12 engines.

SEE CURRENT Mark-15 STATUS

SEE Mark-15 pictures, drawings, and specifications

FIRST PSRU: MARK-9

The Mark-9 gearbox (no longer available) was a two-mesh, geared reduction unit, with a vertical offset of 6.125 inches (from the crankshaft centerline to the propshaft centerline). It was our first gearbox to use hydrodynamic bearings, thereby dramatically reducing the gearbox weight.

The Mark-9 was used by EngineAir Power Systems on their firewall-forward, liquid-cooled 440HP turbocharged V8 engine package which was designed primarily for the Lancair-4P airframe. The Mark-9 has flown on several Lancair 4-P aircraft, some approaching 1000 flight hours, and has been installed on several other experimental aircraft which are still under construction.

In early 2012, Lee Behel (retired USAF fighter pilot and Reno Air Races Check Pilot) contacted EPI to inquire about a gearbox for his GP-5 Reno Racer. We built a special version of the Mark-9 for him, and in September of 2012, that 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.

SEE Mark-9 pictures and more information

MARK-10

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.

SEE more information about the Mark-10

MARK-11

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 reduction drives.

SEE more information about the Mark-11

MARK-12

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 currently in the preliminary design phase. Work on that engine program has terminated, and no prototype gearbox hardware has been built.

SEE more information about the Mark-12

MARK-14

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 demise of the client's financial backer.

SEE Mark-14 pictures and more information

MARK-16

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.

SEE Mark-16 pictures and more information

MARK-17

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.

SEE Mark-17 pictures and more information

MARK-18

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.

SEE Mark-18 pictures and more information

MARK-19

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. However, gearboxes similar in concept can be custom designed for a client.

MARK-20

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.

MARK-21

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 the design work, but failed to fund it. The design is now available to any interested client for completion of the design and prototype development.