New Flat-four Two-stroke
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ONE of the many power unit exhibits displayed at the International Boat Show, Earls Court, which closes on Saturday, is a new lightweight fourcylinder two-stroke petrol engine of novel design. Built by the North Downs Engineering Co. Ltd., 540 Purley Way, Croydon, Surrey, to the design of Mr. Laurie Bond (of three-wheeler fame), the new engine is known as the Nordec-Bond Flat Four and, although offered initially for marine applications only, is considered suitable for automotive roles.
The engine has a cast-iron cylinder block and crankcase assembly, and castiron cylinder heads are employed on the 24/30 b.h.p. model, the 40/50 b.h.p. engine having light-alloy heads. Both engines have bore and stroke dimensions of 69.85 mm. and 50.8 mm. respectively, giving a capacity of 0-777 litres, and are water cooled. The more powerful engine peaks at 5,300 r.p.m., whilst the 24/30 b.h.p. model gives its maximum power at 3,000 r.p.m. Also shown is an experimental 70 b.h.p. version, which runs at 9,000 r.p.m. and has two Weber carburetters.
This new engine design has particular advantages in respect of size and weight, with an overall width of 18-75 in., a height of 12-5 in, and a length of 22 in. The bare engine weight is 1201b. Smooth running is claimed to be a particular feature of the design, and all crankshaft bearings are of the ball or roller type.