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The Comet 7-cylinder radials were a family of air-cooled radial engines, designed and built by the Comet Engine Corporation at Madison, Wisconsin from around 1927.
The Comet radial was fairly standard with steel finned cylinders, cast light alloy cylinder heads and two valves per head. The valves are operated by a single rocker arms and push-rods, to the rear of the cylinder, which are in turn operated positively by inner and outer cam tracks operating rollers on the pushrod.
Oil pumps and magnetos are driven by the camshaft drives as well as the Heywood air starter and tachometer.
The two-piece crankshaft, with counter-weights, is carefully forged from heat-treated chrome-vanadium alloy steel and drilled for lightness and lubricating oil flow. Master and slave connecting rods are forged and machined from the same material as the crank-shaft. The rear of the crankshaft carries an induction rotor to ensure even mixture distribution to the cylinders from the Stromberg carburettor.
The two-piece crankcase is split in the plane of the cylinder centres, with the forward half supporting the fwd crank /prop-shaft bearing and the rear half housing the rear bearing, induction rotor, cam drives and accessories.
Design and development
Comet designed the 7-cylinder radial series to take advantage of the boom in private aviation in the late 1920s; intending to replace the large number of relatively unreliable wartime surplus engines that flooded the market in the early 1920s. First produced by the Aircraft Engine Corporation of Oakland, California, new interests acquired the California company and the Comet Engine Corporation was formed under the sponsorship of Air Investors Inc., the Crocker First Company of San Francisco and the Gisholt Machine Company. Production transferred to workshops adjacent to the Gisholt Machine Company in Madison, which acted as production supervisor.
The Comet radial was fairly standard with steel finned cylinders, cast light alloy cylinder heads and two valves per head. The valves are operated by a single rocker arms and push-rods, to the rear of the cylinder, which are in turn operated positively by inner and outer cam tracks operating rollers on the pushrod.
Oil pumps and magnetos are driven by the camshaft drives as well as the Heywood air starter and tachometer.
The two-piece crankshaft, with counter-weights, is carefully forged from heat-treated chrome-vanadium alloy steel and drilled for lightness and lubricating oil flow. Master and slave connecting rods are forged and machined from the same material as the crank-shaft. The rear of the crankshaft carries an induction rotor to ensure even mixture distribution to the cylinders from the Stromberg carburettor.
The two-piece crankcase is split in the plane of the cylinder centres, with the forward half supporting the fwd crank /prop-shaft bearing and the rear half housing the rear bearing, induction rotor, cam drives and accessories.
Variants
''Data from: ;7-RA: From 1928 with Approved Type Certificate No.9, rated initially at at 1,800 rpm. ;7-D: After improvements rated at at 1,800 rpm (maximum continuous) from . ;7-E:From 1929 with Approved Type Certificate No.47, delivering from the same .Applications
''Data from:'' Aerofiles : Aircraft of North America 1903-2003 *Adcox Student Prince
The Adcox Student Prince was a two-seat open- cockpit biplane designed by Basil Smith and built by the students of the US Adcox Aviation Trade School in 1929. It was based on the one-off Adcox Special, and the first example flew on 17 September.
...
* Alexander Eaglerock Bullet C-4 (7-E option not installed)
* Alexander Eaglerock A-12 7-RA and some re-engined with 7-E
* Bach 3-CT-5 (2x 7-RA)
* Bach 3-CT-6 (2x 7-RA)
* Bird Wing Imperial (option)
* Briggs Briggster
* Cessna AC
* Curtiss Robin J-1 (7-D)
* Fairchild KR-34B (aka KR-34B-1) 7-RA
* Fairchild KR-34C (7-E)
* General Aristocrat 102-D proposed 7-RA
* Kreider-Reisner C-4 7-RA
* Kreider-Reisner C-4B 7-D
* Marine Water Sprite Marine Aircraft Co, Sausalito CA. - 7-E
* Maximum Safety M-2 7-RA
* Maximum Safety M-3 7-D
* Neilson Golden Bear
* Parks P-2
The Parks P-2, powered by a 150 hp Axelson-Floco B engine, was a biplane designed and built at the Parks Air College in the United States circa 1929. A change in engine type to the Wright J-6
The Wright Whirlwind was a family of air-cool ...
(option)
* Schroeder-Wentworth 1929 monoplane 7-RA
* Sierra BLW-1 7-RA
* Sierra BLW-2 7-RA
* Spartan C3-166 7-E
* Stearman C3L 7-RA
* Thaden T-2
Thaden is a municipality in the district of Rendsburg-Eckernförde, in Schleswig-Holstein, Germany
Germany,, officially the Federal Republic of Germany, is a country in Central Europe. It is the second most populous country in Euro ...
7-D
* Timm C-165 Collegiate 7-E
* Timm K-100 Collegiate 7-RA
* Towle TA-1 7-D
* Towle WC Amphibion 7-D
* Travel Air 4-U conversion to 7-RA, 7-D and 7-E by O W Timm Aircraft Co.
* Triton Water Sprite, Triton Aircraft Co, Sausalito CA. 7-E
* Warren CP-1
The Warren CP-1, also called Miss Poly, Miss Polytechnic and the Warren Monoplane, was the second aircraft built by engineering students at California Polytechnic College, after their first project the Mason Greater Meteor.
Design and developme ...
7-D
Specifications (variant)
References
{{DEFAULTSORT:Comet 7 radial 1920s aircraft piston engines Aircraft air-cooled radial piston engines