- Propeller Reduction Technology -
A detailed presentation covering the technical issues involved in
successful Reduction Gearbox design and implementation
In early 1993, EPI began the development of a lightweight, 500 HP, liquid-cooled V8 aircraft powerplant (see Aircraft V8 Development). Our Propeller Reduction Gearbox ("PSRU") products evolved from that development program. (For those unfamiliar with the term "PSRU", it stands for "Propeller Speed Reduction Unit". We think it's a hideous term, but it has found wide usage.)
The Mark-9 PSRU was the geared propeller reduction unit which we designed, prototyped, and developed for our Aircraft Powerplant. It was also the first of our gearbox products to use hydrodynamic bearings, which substantially reduced the weight of the package. We put the Mark-9 into production in 1997-8. In late 2000, the product was sold to EngineAir Power Systems for use on their turbocharged 440 HP V8 engine package for Lancair-4 and other experimental aircraft.
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). Since that presentation, EPI has developed a considerable base of technology which supports the design and implementation of reliable, lightweight reduction gearboxes for a variety of aircraft and industrial applications.
EPI has designed and developed several other propeller gearboxes for general use and for special applications. The MARK-15 is our current, general application high performance, high capacity PSRU.
The success of the EPI PSRU products, plus the help EPI has been able to provide to builders having severe PSRU problems, made it evident that complete, clear information about PSRU’s should be made available. This technology section presents subjects directly related to the proper design of propeller reduction gearboxes driven by piston engines, in an intuitive way, without the need for mathematics. If you are researching the purchase of a PSRU, you owe it to yourself to study these these presentation subjects.
At a bare minimum, you should begin with our "FAQ's" page, which lists the things you MUST know about PSRU's.
The COMPLETE Guide to PSRU Technology