Commercial Motor Vehicles

Oil-Engine Commercial Vehicles.

During the '20S a new type of high-speed oil engine or Diesel engine was developed for motor vehicle use. It was first applied to motor trucks in Germany in 1926. The engine had the advantage over the gasoline engine then in general use, that it burned a cheaper fuel, gas oil, and consumed only little more than half as much (in liquid measure) per horsepower-hour. What added further to the economy of these engines was that at that time there was no tax on gas oil comparable to the gasoline tax, and as long as this condition con tinued the saving on fuel due to the use of Diesel engines in mo tor trucks in European countries was of the order of 8o per cent. In 1939 most European countries (and practically all of the States of the Union) levied the same tax per gallon on gas oil used in road transportation as on gasoline. The first cost of the Diesel engine was considerably higher than that of comparable gasoline engines; it was more difficult to start, and it was not as smooth in operation as the gasoline engine, especially when idling. However, the use of these engines on larger trucks spread very rapidly throughout Europe.

During the early '3os a new type of truck, known as the camelback or cab-over-engine type, was introduced. Up to that time practically all trucks had had the engine at the forward end under a hood, and the driver's cab back of it. Engine compart ment and cab took up nearly one-half of the total length, and the "pay load" was practically balanced over the rear axle. There were legal limits on both the total gross weight of the truck and on the load carried by one axle, and as with the conventional truck of that period fully loaded, more than 75 per cent of the gross load was usually on the rear axle, the limit on the axle weight was the deciding one. It was then realized that in order to be able to carry greater gross loads without exceeding the legal limit on axle load, it would be necessary to shift the pay load farther forward, and this led to the development of the type of truck mentioned, in which the driver's cab is directly over the engine compartment.

in some of these buses both clutch control and gear shifting were effected pneumatically. In these buses the powerplant was lo cated under the rear transverse seat and therefore occupied no space on the chassis that could be utilized for passengers. This ap plied also to another type in which a horizontal opposed 12-cylin der engine was slung underneath the chassis frame. As early as 1935 most of the buses newly placed in service in large cities were of this "transit" type.

The motor bus had become a formidable competitor of both the street car and the railway coach. At first motor buses were used by street railway companies as feeders in outlying districts. Later the bus began to replace the trolley car, as the riding public un mistakably showed its preference for the former. One of its ad vantages that was particularly appreciated was that it gave "curb service." Replacement of trolley cars began in the smaller cities, but after 1930 it extended to populous cities.

Multiple-Stop Delivery Vans.--A

special type of light com mercial van for use by dairies, bakeries, laundries, dry cleaners, etc., in house-to-house delivery work, was developed in the United States beginning about 1930, and has come to be known as a multi ple-stop van. Its distinguishing feature is a frame which has a

drop in it near the middle of its length, where the doors are lo cated, so as to make it easy for the driver to get in and out. Slid ing doors are usually fitted, and the single seat is of the pedestal type, with folding back. There is a step on each side, inside the door, which is usually only 6 to 8in. above the curb. The entire interior of the closed body is in a single compartment, so that goods can be entered and removed through the front doors. The whole design is worked out with the idea of reducing to a mini mum the effort and time required to bring the vehicle to a stop, remove goods to be delivered, re-enter the vehicle, and get started again.

Motor Omnibuses.

The early buses were similar in design, so far as the chassis was concerned, to the early motor trucks. A great step in advance was made when the safety bus was de veloped in 1922. As compared with earlier buses, the chassis was considerably lowered and the tread widened; the vehicle, more over, had an engine of increased power and was equipped with air brakes. From that time on the use of buses increased quite rapidly.

Quite a number of the early city buses were of the double-deck type, and many of these were still in use in the large cities in 1939. However, of the buses manufactured in the United States during the five-year period 1930-34, less than 1 per cent were of the double-deck type. The early double-deckers carried a conduc tor, and passengers entered and left the bus at the rear; later double-deckers were operated also as one-man vehicles, with a front entrance.

In 1927 a new design of bus, known as the street-car or transit type, made its appearance. Its object was to provide greater seat ing capacity for the same over-all dimensions and weight. In the prototype, the Twin-Coach, two separate engines were em ployed, one under the seats at each side of the bus, each engine driving one of the rear wheels. In later designs a single engine unit was used, located transversely at the extreme rear. In the first of this type of vehicles the gas-electric system of transmis sion was employed, which afforded greater liberty in respect to the location of the engine. Later mechanical drives were de veloped for engines mounted transversely at the rear. In one design the propeller shaft extended at an angle from the end of the transmission, near one side of the bus body, to the final-drive housing at the centre of the axle, while in another the power plant was mounted directly over the axle and the propeller shaft was vertical. With the powerplant so far from the driver's seat, the control connections naturally presented a problem, and The motor bus that same year played an even more important part in inter-city transportation. 3,904 companies operated 22,820 buses and did a transportation business of 11,287,000,000 passen ger-miles, as compared with 18,000,000,00o passenger-miles for all Class A railroads. The gross revenue of the inter-city buses was $171,200,000 (1.52 cents per passenger-mile), while the gross passenger revenue of Class A steam railroads was $346,220,277 (1.92 cents per passenger-mile).

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