1/3 Scale 80 HP LeRhone Rotary Aero Engine---A 3 Year Project


Using full-scale parts from Murin Antique Aero and WWI Aero Magazine drawings, I drew in CAD a full-scale metric, and then reduced it to one-third metric for building.  Building the cams, intakes and rods were really challenging. The two disc cams had to be digitized, as they are unique.  Five lobes, 72 degrees each, control 720 degree of cycle.  One deg error = 10 deg of cycle error.  Also being a random cam (any cyl) each lobe had to be the same size and shape. The cam is mounted off center to fit a single drive gear. The 40T int cam and 36T crank gear (33 deg pitch) have to be very accurate regarding backlash. This is a very reliable drive but adds an extra sine curve to the motion.  Max valve lift is actually on a flank—not a crest.  A single pushrod pulls for intake and pushes for exhaust. The intake cam due to centrifuge force controls cycle until exhaust has to open.  With only one push rod adjustment, each valve stem has to be shortened to match cycle.  A dial indicator on each valve and deg wheel verifies endpoints.  Next obstacle was the famous copper intake pipes. These also were digitized (3D) and dies were CNC machined for hydro forming.    Prebends were crushed in the die and sized with 6500 psi using a portapower.  The sealing  “o” ring groove was spun.  The connecting rods are of the crutch design, which is also unique with LeRhone.  This design is better than a master rod system as all cylinders have same piston velocity and all forces are on the crank centerline.  To obtain a light flying engine, I used anodized aluminum for the crankcase and jugs—original was all steel.  Engine was from bar stock, oil pump and carburetor had to have castings made—these were wax—investments.  Castor oil is used with scale piston pump and pulser.  Block tube carburetor and ignition cut (coupe) control engine speed.  Note—this engine produces 8.5hp/8.5lb, the full-scale 260lb/80hp=3.25/1. 


¼-32 spark plugs are from Napco—Tempe, AZ

C&H ignition and hall sensor

 Fuel—low-test gasoline

 Castor oil lube

 Prop from Tennessee Propeller  32/28

Dyno-42lb. thrust at 2700 rpm—18ft/lb.  Torque=8.5 hp

Engine 8.5 lb.—prop 1.5 lb.

Bore 35mm     Stroke 46.7mm


Thanks and Acknowledgement

Fred Murin, Jim & Zona Applebee, Jim Klein, Paul Knapp,

John Tanzer, Bob Cooper  & Peter Petrushenko   

Cory Stevens and Gerry Nadon—CN Aero Museum in Ottawa


Airplane: Moraine Saulnier---Type L


During each engine build, I searched for a suitable stable aircraft. When I saw the Moraine L on the Windsock International, Nov.—Dec.  2003 cover, I fell in love with the classical elements, high wing for my fuel tanks and side access doors.  J. M. Bruce filled in the details with the Windsock Date file 16.  The Page 16 uncovered fuselage was an immense help for scratch building.  The half cowl lets the engine, the heart of the project shine through.  The aircraft is 1/3 sport scale as I used a Clark Y airfoil, ailerons and earlier landing gear and late fin.  Also it has only a single seat with radio antenna (used) post.  The original used the 80 hp LeRhone and flown by Lt RAJ Warneford was famous for downing the first Zeppelin.  In flight the rudder was so very effective (proverst jaw) that turns needed cross control with ailerons.  The flying stab worked very well.


Span is 12’3 wt-38lbs.

Wing load 25 oz/sq.ft. 

The aircraft balance perfectly with 8.5 motor and 1.5 lb. prop.

Covering is Solartex and Nelson clear water base polyurethane

Aluminum antique airfoil landing gear material from Commander in B. C.

Cowl is modified Balsa USA. Cowl and all struts were black powder coated.

Vintage 33/28prop.from Tennessee Propellers

9” wheels--Ried Hobbies


Thanks and Acknowledgement


Leo Updyke & Tom Polapink—WWI Aero Magazine

Dave Millhill & Dan Hayward—Chenango NY R.C. Club

Jim Quinn, Dick Owens, Bob Pickney—video

Sandy & Ralph Clobridge---video edit