The Almen A-4 Barrel Engine

The Almen A-4
Barrel Engine
by
Kimble D. McCutcheon
Almen A-4 (1924)
Almen A-4 Specifics
Type . . . . water-cooled barrel-18
Bore . . . . . . . . . . . . . . . 4.250 in
Stroke . . . . . . . . . . . . . 5.500 in
Displacement . . . . . . . 1,404 in3
Power . . . . 425 hp @ 2,000 rpm
Weight . . . . . . . . . . . . . . 749 lb
Diameter . . . . . . . . . . . . . . 20 in
A-1 Noteworthy Features (1)
A-1 Noteworty Features (2)
Nine Cylinders, Each With Two Pistons
“Wabbler” Plate Replaced Crankshaft
Gearing Prevented Wabbler Rotation
Balls & Sockets Attach Pistons to Wabbler
Rotary Disk Valves at Each End of Engine
Six Spark Plugs Served Eighteen Cylinders
“Wabbler” Kinematics
Rotary Valve Schematic
Development Challenges
Rotary Valve Improvements
Port Timing Refinement
Port Shape Refinement
Magnesium Alloy Replaced Cast Iron
Seal Refinement
Piston Joint Improvement
Wabbler Bearing Improvement
Slanted Plate
with Kingsbury
Bearings
Replaced Ball
Bearings
A-4 Noteworthy Features
A-4 Noteworthy Features (2)
Improved Piston-to-Wabbler Joint
Floating Wabbler
Kingsbury Wabbler Bearings
Dual Ignition, 36 Spark Plugs
Incorporated Improved Valve Disk
Still No Supercharger
Competition: Michell Crankless
Competition:
Bleser/Herrmann/Dyna-Cam
FAA Type Certificate E-293 (Dec 31, 1981)
Dyna-Cam Mechanism
Dyna-Cam Specifics
Type . . . liquid-cooled barrel-12
Bore . . . . . . . . . . . . . . . 3.250 in
Stroke . . . . . . . . . . . . . 3.750 in
Displacement . . . . . . . . . 373 in3
Power . . . . 200 hp @ 1,900 rpm
Weight . . . . . . . . . . . . . . 338 lb
(Weight includes starter and generator)