COLD ENGINES

Rotorua Morning Post, Volume 1, Issue 210, 29 April 1932, Page 2

COLD ENGINES

WHY NOT THERMOSTATIC CONTROL OF FANS? Considering the mechanical excellenee and advanced design of most of the 1932 models, it is a strange thing that on almost all of them, from the "baby" costing £100 to the powerful car costing £3,000, there is a.n antiquated "windmill," or fan, driven by a piece of belting. Stranger still is the f act that this fan is allowed to turn at a fairly high speed whenever the engine is running, although it is actually needed to assist cooling only under certain rare conditions; for example, when pulling hard at low speeds in traffic or on a steep hill. Noisy, and a Waster of Power Were this all, one would not perhaps he very critical, but the wretched fan, apart from the few occasions when it is useful, is actually doing harm hy spinning around. Thus it is mounted on a bearing which requires constant lubrication, it is usualiy noisy at high speeds and, last but not least, it causes a wastage of power which can be quite considerable. • The quieter engines and gearboxes become the mort noticeable is the noise of the fan, and on several new American cars blades of a special shape, coated with rubber, have been tried to minimise' this drawbaek. Another plan is to arrange the blades unsymmetrically. Even if noise be overcome there is still the wear and tear on the belts and bearing to consider, which is naturally most seiious at a time when the fan is not of the slightest use, i.e., when travelling f cist Fan May Obstruct Air Flow Above a certain critical speed probably about 30 m.p.h. in many cars — the air flow through the honeycomb which is induced by tbe motion of tbe car ceases to be assisted by tbe presence of the fan. At still higher speeds the fan may actually produce a slight baffling effect* ^texiding to obstruct the flow of air instead of providing assistance! In a bad case which was recently brought to our notice the removal of the fan belt, by .obviating power loss and baffling, caused the maximum speed of a ear to iricrease from 75 m.p.h. to 78 m.p.h. . There is only one recent mstance, so far as we remember, of a car manufacturer providing a clutch in the fan drive, this having been done in a Ballot chassis produced a few years ago. In this case the fan was driven .mechanically from an overhead camshaft through the medium of a clutch which could he operated from the driver's seat. It was therefore possible to bring the fan into action as and when required, so avoiding noise, waste and wear when this adjunct to cooling was not needed. In these days, however, the thermostat has becoirie so reliable and so widely used for eontrollirig temperatures that there seems to be no vital reason why it should not be employed

for the automatic operation of a clutch interposed in the fan drive. It would, indeed, seem quite possible to employ one and the same thermostat for controlling this clutch and for operating the familiar thi'ottle-valve so often used to restrict the circulation of water. To drive a fan requires quite a considerahle amount of power, so that a satisfactory clutch would have to be of reasonable size, fitted with a fairly powerful spring. Naturally, a thermostat could not be expected to operate this clutch directly, so that it would have to be employed in eonjunction with some servo system or relay. How Could Control Be Arranged A simple way of doing this would be to connect the thermostat with a valve whereby a cylinder and piston could he coupled at will to the lubrication system of the engine. The idea would be that at normal temperatures the valve would be held o'pen so that oil pressure would exert a force which would maintain the clutch in a disengaged position. If the temperature exceeded a certain limit, however, the thermostat would close the valve and open an outlet port, so releasing the clutch spring and engaging the drive to the fari. There is no reason why a device of this kind should give trouble considering the feliability which has been achieved with other thermostatically operated meehanisms such as radiator shutters. However, until our designers come up to the scratch in this respect most owner-drivers will at this time of year adopt the time-hon-oured practice of removing their fan belts and hanging them in their garages until the winter is over. Belt-driven Pumps and Dynamos These remarks do not, of course, apply to cars in which the belt drives an additional component such as a water impeller or dynamo. In some cases it is, however, possible (as an expedient) to remove the fan itself by undoing three or four set screws, leaving the pulley and spindle undisturbed. A little trouble in these respects is amply repaid, as the engine will run at a higher and more efficient temperature, while the disadvantages associated with use of a fan ; are naturally avoided. To over-cool an engine causes a waste of fuel and militates against good performance.