Modern Equipment for Reconditioning Engines
Page 58
Page 59
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ASHEFFIELD concern which has earned a good reputation in connection with the reconditioning of engines, particularly the regrinding and refitting of cylinders and the regrinding and reassembly of crankshafts, is the Lodestar Motor Co., the service department of which is at Effingham Road in that city. The company's treatment of what is a highly specialized section of servicing work has come to be recognized, and this is partly due to the fact that proper machinery is used for the various operations.
The latest machine installed at this company's works is a Churchill crankshaft grinder, an extremely accurate B44 machine of well-known type, made by the Churchill Machine Tool Co., Ltd., of Manchester. Crankcases and crankshafts are received together ; the crankshaft is reground, bearings are remetalled, or new bearings are supplied that have been machined in line, the units being returned ready for assembly. Difficulties attend the regrinding of cylinder bores, but if the operation be well carried out the cylinders are probably more accurate than they were when the engine was ne*. The alternate beatings and 000lings of the engine block, resulting from continued use, release internal stresses in the cast metal which slightly alter its shape. If the cylinder block be then reground with accuracy, a higher degree of efficiency is often obtained.
Another point is that, with quantity production, it is possible for a minimum-sized piston to be mated with a maximum-sized bore, according to the limits established by the works inspectors, whereas when a cylinder block is reground each piston is fitted to its particular cylinder, a better fit in this way being obtained. Cyrinder bores can, of course, be machined by boring, reaming, .honing or lapping, but grinding is the only method employed by this concern. In a booklet dealing with the subject the comnany points out that, when the boring process is used, the cutting tool is liable to cut less deeply where the cylinder wall is unsupported than where it is reinforced, due to the wall actually springing away slightly under the pressure of the tool, Grinding obviates this faulty effect.
The company's prices for cylinder grinding and the fitting qaf new pistons, gudgeon pins and rings, are fixed according to the bore and number of Cylinders, and for commercial-vehicle engines they vary between about £5 and £8 10s., being slightly higher when aluminium or special pistons are required. Cylinder sleming is also carried out by this concern.