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Sunbeam Afridi

From Alfawiki
Sunbeam
IndustryAircraft engines
FounderLouis Coatalen
ProductsAircraft engines (Afridi, Maori, Manitou, Tartar)

The Sunbeam Afridi was an aircraft engine manufactured by the Sunbeam during the period of the First World War.[1]

Design and development

Conceived by Louis Coatalen as a replacement for the Crusader/Zulu and to complement the V-12 Cossack, the Afridi was a more compact powerplant that became the basis for a series of related engines.[1]

Its principal dimensions included a bore of and a stroke of , resulting in a total displacement of and an output of at 2,000 rpm. The engine utilized twin overhead camshafts driven by gears, controlling two intake and two exhaust valves per cylinder. Fuel delivery was handled by two Claudel-Hobson carburettors, while ignition was provided by a dual system powered by four 6-cylinder magnetos.[1]

Out of an order for 300 units, 299 were completed, with 100 later converted into Sunbeam Maori engines. The Afridi primarily powered Curtiss R.2 tractor biplanes along with various Short seaplane models.[1]

Maori

The Sunbeam Maori represented a direct evolution of the Afridi and achieved considerably greater success. Coatalen increased the bore to while maintaining the original stroke of , yielding a displacement of and generating at 2,000 rpm equipped with reduction gearing.

Production commenced in April 1917, initially converting 100 Afridis to Maori Mk.I specifications (rated at ), followed by new-build Maori Mk.IIs rated at . The Maori engines were widely utilized in Short and Fairey seaplanes as well as Handley Page O/400 bombers, prompting further refinements into Maori Mk.III and Mk.IV variants. The Mk.III featured cylinder banks with exhaust ports positioned externally and carburettors internally, delivering .

Designed specifically for airship applications, the Maori Mk.IV incorporated rear-mounted controls, a flywheel, enhanced cooling systems, and water-cooled exhaust pipes. Five Mk.IV units powered each of HM Airship R33 and HM Airship R34, installed within gondolas to facilitate maintenance during flight.

Manitou

Developed from the V-12 Maori Mk.III beginning in 1917 under Coatalen’s direction, the Sunbeam Manitou employed aluminium alloy blocks cast in groups of three—a distinctive Sunbeam technique. The bore was enlarged to , while stroke remained at , arranged in a 60° V configuration with twin overhead camshafts per bank operating four valves per cylinder. Fuel was supplied through two Claudel-Hobson carburettors with ignition managed by two BTH magnetos. Featuring reduction gearing for aviation use, it produced at 2,000 rpm, later increased to .

Although orders for 840 units were placed, only 13 Manitous were completed before production ended. These engines mostly found application in motor-boat propulsion; just one example flew in a Short 184 seaplane. Four Manitous powered the Maple Leaf V powerboat, and a specialized Manitou engine was installed in the 350hp Sunbeam racing automobile.

350hp Sunbeam

The Manitou gained recognition as the power source for the 350hp Sunbeam racing car in 1920, which was later purchased by Malcolm Campbell for his land speed record ventures under his Blue Bird series.

For this purpose, Coatalen extensively modified the engine, substituting the original twin-cam four-valve cylinder head with a single-cam three-valve head—likely adapted from the Sunbeam Arab—and increasing bore size to 120 mm to accommodate three valves.

To preserve sufficient bearing area on the big ends, articulated connecting rods were employed: one rod connected directly to the crankshaft journal while its counterpart operated via an intermediate journal mounted on the first rod. This configuration resulted in slightly varied piston strokes—135 mm on one bank versus 142 mm on the other—potentially causing imbalance and vibration challenges.

Following initial use by Coatalen himself, the car was sold to Sir Malcolm Campbell for his attempts at setting world land speed records.

Tartar

The Sunbeam Tartar represented an innovative V-12 powerplant developed specifically for airship use. Unlike conventional designs that grouped cylinders into blocks, this engine employed separate cylinders to create each bank. It preserved the Manitou's bore, stroke, and dual ignition setup, while introducing a single overhead camshaft that actuated four valves per cylinder through rocker arms. With a total displacement of , the Tartar delivered an output of , yet it remained at the prototype stage and never progressed to mass production. Its architecture likely served as a foundation for the larger Sunbeam Sikh engine, which also featured individually mounted cylinders.

Applications

External links

  • Sunbeam Overhead Cam Engines, Wolverhampton Museum of Industry (archived)
  1. ↑ 1.0 1.1 1.2 1.3 1.4 Cite error: Invalid <ref> tag; no text was provided for refs named Brew
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