THE MERITS OF THE TWO-BEARING CRANKSHAFT.
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The 2-ton chassis produced by the Associated quipment Co., Ltd., _of Welthamstow, is the first A.E.C. model to be fitted with a two-bearing crankshaft, and, naturally enough, the departure from the company's previous practice of fitting three-hearing crankshafts and ealuminium crankcases and the substitution of a two-bearing crank in a cast-iron case for the engine of this model has raised certain comments,and inquiries.
By sacrificing lightness and eaaking use of a cast-iron barrel crankcase with a two-bearing crank, the manufacturers have produced an engine which ern bodies the desirable features of efficiency, accessibility, simple construction, low maintenance cost and low construction rest. The company are able to .secure satisfactory results from this form of construction, owing to the small size of the engine of 'the 2-ton chassis, which . has a bore of 100 mm. and -a stroke of 140 mm. In engines of a larger size the weight would be excessive if this construction were followed, and the design, therefore, would be uneconomical. The big-ends of the engine of the 2-tanner are 70 mm. in diameter and 64 mm. in length, and c,ompairison with the three-bearing cranks on the com
pany's engines of larger size indicates the extreme stiffness of the construction, which avoids distortion and spring in the two-bearing crank.
The use of ball bearings on this crankshaft has been decided on after careful tests, which have convinced the company of their suitability for the work. Their adoption has resulted in an extremely simple construction for the crankcase, and, as a result of the largo and heavy-duty bearings used, it is said that their life should exceed that of plain bearings. Moreover, their ultimate renewal is a simple matter involve ing no scraping or bedding-in.