A Thermostat controlled Heating System
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A Full Description of the Smith-Eastern Apparatus for Motor Coaches
IN our issue dated March 3 there appeared a brief description of the new Smith-Eastern heating apparatus for coaches, and we are now able to explain the system in greater detail.
As briefly stated, a series of radiators within the coach is supplied with hot water from the cooling system of the engine. In the discharge pipe from the cylinder jackets to the cooling radiator is situated a butterfly valve, and from below it a branch pipe is led to the body-heating radiators. The volume of water flowing through each is regulated automatically by a thermostat.
Water is conveyed by the branch pipe to a two-way valve, connected by a union to the body radiators, whence it returns to the suction side of the circulating pump, and, by the other to a pipe which by-passes these radiators. In this ease the valve is controlled manually by the passengers, and the amount of water flowing through the heating apparatus depends, therefore, upon their re uirements.
The thermostat can he adjusted by the driver according to air temperature, and its function, first, is to keep the passage to the cooling radiator restricted or fully closed until the engine has warmed up to the most efficient temnerature, and then to open the valve just sufficiently to prevent the temperature from rising still further.
During the warming-up period, the water circulated by the pump flows from the engine either directly back to the' pump by the by-pass, or through the heating radiators, in some circumstances these may absorb most of the heat generated by the engine, in which case the thermostat cuts out the cooling radiator almost completely. On the other hand, as the temperature of the engine approaches the desired maximum, when the body circuit is cut off, the full discharge from the pump will pass through the cooling radiator.
Engine Temperature Always Right.
Thus under all conditions of throttle opening, speed, and air temperature, the thermostat keeps the engine at the right heat, whatever the position of the temperature-regulating valve inside the coach.
Two taps in the out-and-return pipelines enable the system to be completely isolated from the engine.
The Smith R.P. thermostat, used exclusively on the Smith-Eastern system, consists, of course, of a coiled element composed of two strips of metals having
widely different Co-efficients of expansion, the strips being welded together throughout their length ; thus, as a change of temperature occurs, the coil exerts a rotary effort which actuates the valve.
Inquiries concerning the apparatus should be addressed to S. Smith and Sons (Motor Accessories), Ltd., Cricklewood, London, N.W.2. We understand that the Eastern Counties Omnibus Co., Ltd., which concern has played a prominent part in developing the system, is installing it in all its. long-distance coaches and that it is giving entire satisfaction. The company runs regular services from London to the eastern counties.
The radiators are built into the floor of the gangway of the coach in such a way that the intervening mats are flush with their surfaces.