Radiators may be mounted in two positions on the chassis frame; either in front of the car so that the air currents pass almost unobstructed through the passageways, or in back of the engine against the dashboard, while on one particular chassis it is placed in the rear of the engine under the seat. Either of the latter two positions afford a somewhat more accessible engine and also afford a better protection for the radiator. However, this construction requires a proportionately larger radiator to obtain the same results as in the forward position.
In commercial car operation the heavy vibrations accompanying high speed on rough pavements and the distortion of the frame, place heavy strains on the radiator, so that it becomes necessary to mount it on springs and also provide a certain amount of universal movement to overcome frame distortion. These springs may be of flat spiral or coiled wire or of round or square section. This support is usually of a three-point type, so that a limited amount of universal movement is obtained.
Fig. 35 shows a popular type of enclosed spring mounting combined with the front spring hanger brackets. Brackets, riveted to each side of the radiator, have extensions, which are mounted between two coiled wire springs in each spring bracket. This bracket has a small cover plate which retains the springs, and, together with the spring bracket, supports a vertical shaft, which acts as a guide for the radiator brackets. The radiator brackets are drilled out larger than the shaft, to provide for a certain amount of universal movement. The top of the radiator is further supported by a stay rod which is attached to the dashboard. A bumper extending from one spring bracket to the other protects the radiator core from being damaged by colliding with the rear end of other vehicles.
Various constructions are resorted to in practice. However, they merely present different methods of accomplishing the same results.
Fig. 37 shows a construction using a flat spiral spring attached to the radiator. One end of the flat spiral spring is bolted to the upper flange of the frame member, while the other end is rolled into an eye. A bolt is inserted through the spring and side column to form a permanent fastening.
An excellent example of flexible mounting is depicted in Fig. 38 in which a pneumatic shock absorber is used. This shock absorber consists of a pneumatic rubber sphere placed within a chamber of elliptic shape, providing a perfect cushion and acts as a pivot, while it is perfectly enclosed and protected from dirt and grit. This sphere is protected against excessive wear by fabric pads set into the cups which form the chamber. These are free to roll in any direction on the sphere, thereby relieving all warping stresses, while the spheres take up all shocks and vibrations.
Fig. 36 illustrates another type of spring mounted radiator. However, in this case a limited universal movement is obtained through a clevis joint on the frame bracket, while the bumper is set into the main frame channel.
Fig. 35. Combined Enclosed Spring with Front Hanger Brackets.
Fig. 36. Universal Enclosed Spring Mounting.
Fig. 37. Flat Spiral Spring Mounting of the Master Trucks.
Fig. 38. Onieda Radiator Mounting.
There arc four general types of water pumps: the gear, the centrifugal, the rotary or vane and the plunger types. The centrifugal is by far the most popular and the gear type is next in popularity, while the rotary or vane type is very little used on commercial car motors. The plunger type is entirely confined to marine work, where it is used to better advantage.
The centrifugal type illustrated in Fig. 39 is perhaps the simplest of all and the easiest to understand. It consists of an impeller of paddle-wheel which may either be formed integral with or keyed to the driving shaft and a case and cover which house the rotating member. In operation it is rotated at a high speed, the water entering at the center of the rotating monitor, flowing out on the arms or paddles and being thrown off by centrifugal force. This throwing off action is restricted by the case, so that the water is forced through the pump outlet.
The gear type of water pump is identical with the gear type of oil pump, with the exception of being much larger. It is illustrated in Fig. 40 and it can readily be seen that it consists of a pair of gears, a pair of shafts for thorn to rotate on and a case with cover to serve as a housing for the gears and to carry the shaft bearings. The arrows illustrate how the water enters the housing through the inlet pipe and is carried around between the spaces of the gear teeth and forced out through the pump outlet on the opposite side of the inlet. This type of pump is quite simple and was extensively used on the earlier types of commercial cars.
Both the gear and centrifugal types of pumps possess an advantage over other types, in that they provide a continuous stream of water. Between the two there is very little or no choice, unless it is that the gear pump is more likely to become noisy. They both do the work under substantially the same conditions.
The rotary or sliding vane pump shown in Fig. 41 consists of a cylindrical housing in which is located a disc of a thickness equal to the internal height of the housing, but of smaller diameter. The disc is located eccentrically with respect to the chamber and is cut with a diametrical slot dividing it into two halves, in which slots are located two sliding vanes which are pressed apart by a flat spring between them, the action of the vanes being to carry the water around to the outlet as indicated by the arrows.
Water pumps are generally driven by shafts extending from timing gear housing and are provided with flexible or universal driving couplings. The couplings serve to keep the pump free from strains due to misalignment, and they are generally so designed that when the pump freezes up, the coupling will break before any damage is done to the pump parts.
Fig. 39. Sectional View of Centrifugal Pump.
Fig. 40. Section of Gear Pump.
The motor must be cooled effectively regardless of car speed. To cool a commercial car motor under ideal conditions and most effectively would require a tremendously large radiator, if the car stood still and only natural air circulation were depended upon. To reduce the radiator to a size that can be used, the relative efficiency is increased through an artificial flow of air. This is brought about in two ways. One is that the radiator does not stand still, but is moved with the car, which induces an air circulation. However, this would not be effective with the car standing still and the engine running, so a second artificial circulation is provided through a fan. This fan is driven from the engine and rotates when the engine rotates. If the engine runs slowly and has little heat to dispose, the fan runs slowly. Again, when the engine is running at its maximum speed, the fan, too, is making its highest possible number of revolutions. The fan serves the same purpose in an air-cooling system, by forcing a draught of air over the cylinders in each revolution.
This fan is generally placed at the front of the motor and driven by belt from a pulley mounted on the crank shaft, cam shaft, or accessory drive shaft, and draws air through the radiator, while in the air-cooled system it draws air through a screened opening at the front of the hood.
Sometime ago there was a decided tendency to combine the fan with the flywheel, drawing air through the radiator and over the whole engine, thus effecting a secondary method of cooling. In some air-cooling systems the bonnets on the engine are provided with deflectors so as to direct the air currents to the rear cylinders, while one maker encloses the entire motor in a sheet steel housing, so the flywheel draws an equal amount of air over each cylinder.
Fig. 41. Section of Sliding Vane Pump.