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GRI Motorcycles


G.R.I. (1920-22) Un motor con una distribución inusual

Finalizada la Primer Guerra Mundial las inovaciones técnicas implementadas en los motores de aviación se trataron de aplicar en las motocicletas. Es así que George Richard Inshaw (1888 -1951), un ingeniero consultor del “Inshaw Rotary Engine Syndicate” que ya había patentado el aeromotor rotativo de Inshaw (construido en los talleres de Gnome and Le Rhone de Walthamstow) diseña un motor de motocicleta con válvula única para la G.R.I. Motors, Ltd., de Glasgow, Escocia. Las motocicletas G.R.I. fueron producidas entre 1920 y 1922 y eran distribuidas por la firma Macrae y Dick de Inverness, Escocia.

El motor diseñado por Inshaw tenía una tapa de cilindro desmontable y, en lugar del mecanismo de válvulas convencional, el flujo de gases era controlado por una válvula de distribución rotativa en conjunto con una única válvula de asiento que era conducida por un balancín y una leva montada sobre el mismo eje de la válvula rotativa. De ese modo la válvula rotativa no estaba sometida a la compresión generada en la cámara de combustión puesto que era la válvula de asiento la que lo soportaba. El puerto de admisión estaba ubicado debajo del puerto de escape y ambos pasajes estaban comunicados con la cámara de combustión a través de un orificio común sellado por la válvula de asiento. El conjunto de válvula rotativa y leva era impulsado desde el piñón de salida del cigüeñal por una cadena que también comandaba al magneto C.A.V. Los gases del escape eran descargados hacia atrás y conducidos hasta el silenciador a través de una caño metálico flexible.

La máquina se presentó por primera vez en 1920 con dos modelos de 349 cc y 496 cc y tenía el motor instalado en un cuadro convencional con horquillas Brampton Biflex, caja de cambios Sturmey-Archer de dos velocidades y transmisión final a correa. El carburador era Brown & Barlow.

A pesar de intervenir en varias competencias de velocidad (aunque con escaso protagonismo) las válvulas rotativas revelaron ser poco confiables por lo que las motos G.R.I. no tuvieron la aceptación del público y pronto desaparecieron del mercado. Sin embargo me pareció válido mostrar este ingenioso sistema de distribución que proclamaba ser simple y eficaz pero … en 1920 aún no era el tiempo de las válvulas rotativas.


G.R.I. (1920-22) an engine with an unusual distribution

After the First World War, the technical innovations implemented in aviation engines were often applied to motorcycles. George Richard Inshaw (1888-1951), a consulting engineer for the "Inshaw Rotary engine syndicate" which had already patented Inshaw rotary aeromotor (built in the Gnome & Rhone workshops in Walthamstow ¹) designed a motorcycle engine with a single valve for G.R.I. Motors, Ltd., Glasgow, Scotland.

The motorcycles were built between 1920 and 1922 and were distributed by the firm Macrae and Dick of Inverness, Scotland.

The engine designed by Inshaw had a detachable cylinder head and, instead of the conventional valve mechanism, the gas flow was controlled by a rotating valve in conjunction with a single poppet valve which was driven by a rocker and a cam mounted on the same axis of the rotary valve. In this way the rotary valve was not subject to compression generated in the combustion chamber since it was the seat valve that supported it.

The inlet port was located under the exhaust port and both passages were reported with the combustion chamber through a common orifice sealed by the poppet valve. The rotating valve set and cam was driven by a chain which also drove the C.A.V. magneto. The exhaust gases were routed to the silencer via a flexible metal pipe.

The machine was first presented in 1920 with two models of 349 cc and 496 cc and had the engine installed in a conventional frame with a Sturmey-Archer gearbox and belt drive. The carburetor was Brown & Barlow.

    Application filed January 27, 1921. Serial No. 440,490.

    Be it known that I, GEORGE RICHARD INSHAW, a subject of the King of Great Britain, residing at Murcia House, Pollokshields, near Glasgow, North Britain, have invented new and useful Improvements in Connection with the Valvular Arrangements of Internal Combustion Engines, of which the following is a specification.

    My invention relates to internal combustion engines working on the four-cycle principle and of the kind wherein the valvuar arrangements comprise a tappet-valve, which is opened at the proper times for induction and exhaust and closed during the compression and working strokes and controls a passage to the cylinder...

    Patent US 1374158 A

Notes


1. The Walthamstow workshops built engines for Sopwith Camel. After the war, Sopwith built the ABC, which was not a commercial success in Britain. Gnome et Rhone later built the machines in France.

Sources: archive.org, Graces Guide, espacenet et al.
Original Spanish article by Sergio Scalerandi.



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