GR-5A Experimental Turboshaft Engine

       During the construction of the GRV-1 Turbotug, modifications were made to the GR-5 Turboshaft Engine. These modifications transformed the GR-5 into the  self starting GR-5A turboshaft engine. Being completely constructed from “off the shelf” items, the 8  horsepower engine is like no other turbine. The home-built engine features an electric start, electronic control system, and an internal alternator to generate power to run the engines systems. A propane fuel source, external battery and starter switch is virtually all that is needed to run the GR-5A.

       The engine is based on an unmodified automotive turbocharger that could be replaced at any time with an off the shelf T3/T4 turbo. Repair to this turbine would cost a fraction that of a commercial engine.

       The power turbine design is centered around a low-speed single stage axial flow turbine wheel that is made from mild steel. No exotic alloys were used to create the power turbine assembly. Although the power output is very low compared to a commercial unit, it still has it’s place as a useful research tool.

       The GR-5A engine had it’s humble beginning as the GR-1 Turbojet Engine.  The GR-1 project forged the basis for the GR-1 combustor design which made cooler engine operation possible. The low temperature gas produced by the GR-1 made the implementation of the slow-speed free turbine possible.

       The 650 watt on-board alternator supplies all of the current needed to run the ECU, oil pump and sensors. The alternator also charges the external battery used to start the GR-5A.

       The remote panel used to control the GR-5A was developed with a universal purpose in mind. The panel incorporates a standardized control system that not only communicates with the GR-5A but will connect to future engine designs as well. The control wiring was truncated to twelve conductors as most of the control operations are performed by the engine’s ECU (electronic control unit).

       A majority of the engine’s parts were purchased from eBay auctions. It took a little time to find the parts needed but it kept the overall cost of the project down. Without eBay’s service, this project would not have been possible.

       Having this engine to study has been a great asset in understanding gas turbine use and operation. I hope that by posting my research on the web, others may benefit as I had also from other enthusiasts. Thanks for looking at my project!

Don Giandomenico

Be sure to see this engine run in the GR-5A Turboshaft Video. This project has been a terrific learning tool for me and I would like to share it with you now!

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