Having built the Wren MW54 gas genny....I needed something to install and fly it in....I considered a large scale helicopter, but decided in the end to go for the Turbo Raven aerobatic aeroplane with TurboProp power..... clubmate Nick is building the airframe whilst I build the engine gearbox bits.... don't know who will get finished first.....!!

The unit consists of a Wren MW54 kit built, gas generator core engine that drives a carefully balanced power turbine wheel placed in the engines jet exhaust, that in turn drives the propellor via a reduction gearbox. A few performance figures make interesting reading..... the core engine running at 160,000 r.p.m. in thrust form produces around 12Lbs. of thrust (hot air).
This exhaust gas at a temperature of 600C blows the power turbine wheel around at a maximum speed of 55,000 r.p.m. (the turbine wheel is cast from inconel .... the same stuff used to make electric oven elements)
The gearbox reduces this down to a maximum 9500 r.p.m. to drive a propeller up to 26x8" diameter (8000 r.p.m.) and in the process the power output goes up to 40Lb (18Kg) of static thrust.

The original (and only) full size aeroplane flown by Wayne Handley in the USA.....  the Raven had sensational performance with the Pratt and Whitney PT6A-25C turboprop powerplant..... destroyed in a crash exactly one year after its first flight..... lets hope the model lasts a little longer!

The propshaft..... on the left is the raw material EN24 steel bar.....in the middle my first attempt at a shaft....going fine until I skimmed off a bit too much on a bearing journal diameter.....scrap now, but useful practice for my first attempt at screwcutting and the finished assembly on the right with bearings and helical gear fitted....NO I didn't cut the gears myself !

96 inch wingspan ready for final trim

The gearbox is finished now, the little fittings, spacers and lubrication system take an inordinate amount of time in relation to their size. The engine will be using the FADEC ECU from Gaspar Espiel as he also makes a secondary controller that operates the oil pump and limits the power turbine speed. I am looking forward to running the unit up in the not too distant future.....and its installation in the Raven.... for what should be 7HP of smooth and quiet power.