One of the principal sources of vibration is the crankshaft, the "backbone of the engine," where any imbalance is felt throughout the engine and the car. General Motors Research Corporation began working in the early twenties on the problem of balancing engines, and a crankshaft-balancing machine was developed and first used in the production of the 1924 Cadillac engines. This machine, hundreds of which are now in use throughout the world, was exclusively a General Motors development and gave us a long lead in engine balancing in the industry. As in the case of many of our advances, we arranged to sell this equipment to other engine producers. Better balancing was a very important step in the reduction of wear and tear on the whole automobile structure and in permitting faster progress toward the satisfactory utilization of greater power and speed in practically all the engines we build.
As we learned more and more about knock, progress toward higher-compression engines became possible. From the four to one compression ratios of the early twenties, we have now come to ten to one and higher compression ratios. The development of fuels and engines proceeds in leap-frog fashion: an engine with higher compression demands a better fuel, and the availability of a better fuel encourages the production of more efficient engines. Under the urging of the automobile engineers, the petroleum industry has developed fuels of higher and higher octane ratings for general use. General Motors has supplied many high-compression test engines to the oil industry to help it develop higher octane fuels.
In this way the developments of tetraethyl lead and high-octane fuels have made possible the long-range improvement of the internal-combustion engine.
Transmission Development
I suppose almost everybody knows that the purpose of the transmission is to transfer power from the engine to the wheels of a car, and that this involves a change in the speed relationship between the automobile engine and wheels. The power developed by an engine depends on several things, but is closely related primarily to the rotational speed of the engine's crankshaft. With the old lower powered cars, everyone became aware of this upon climbing a hill. This usually required a vigorous speeding up of the engine and a shift to a lower gear to get the power needed. Back in the 1920s shifting gears by hand through the normal three speeds usually resulted in considerable clashing unless the driver had a high degree of skill.
From the time the General Motors Research Corporation was set up in 1920, transmissions were an important subject of study and discussion. At first we concentrated on electrical transmissions of various types, for a large percentage of the original staff of engineers were of electrical background. An electrical drive was developed, and one of this type was used for a time on General Motors buses. The electrical transmission, which was tried out very early in the history of the automobile (in the Columbia and Owen-Magnetic passenger cars) , eventually received its major commercial use in the large-vehicle field. This special form of transmission is used today in our diesel locomotives.
From 1923 on, the interest of our research organization in electrical transmissions for passenger cars declined. We began to study a wide variety of automatic transmissions, including the "infinitely variable" type—in which a large number of speeds were available in uninterrupted sequence, rather than a lesser number in fixed steps, as in the standard transmission—and the step-ratio type in which a fixed number of speeds could be selected automatically. And as early as the middle twenties a hydraulic type of transmission having bladed turbine wheels was investigated. Most of the general principles that went into the making of the fully-automatic transmissions were thus known to us, and were being carefully investigated, at least fifteen years before automatic transmissions became available in production cars.
In the late twenties General Motors developed the synchromesh gearshift, with which almost any driver could shift from one speed to another without clashing the gears.
This significant development was put into production by Cadillac in 1928. The principle was taken up by other General Motors car-division engineers and was further developed for large-volume production by our old Muncie Products Division. By 1932 we were able to extend synchromesh all the way down through the whole General Motors line to the Chevrolet passenger car.
By 1928 the Research Laboratories had reached a consensus on an automatic-transmission form that might be satisfactory. This was an infinitely-variable type using a steel-on-steel friction drive employing a mechanical principle like that of a ball bearing. The Buick Division was assigned the job of developing this transmission since we had no general engineering staff at that time. Many units were built and tests conducted, and it was finally determined to produce this type of transmission in 1932. However, despite our best efforts, we never managed to solve all the problems involved, and this transmission was never put in any General Motors car sold to the public, although many experimental units were tried out in our test cars. A good deal, of course, had been learned about the problems of infinitely-variable transmissions, but it turned out that this specific steel-on-steel type was not the answer to the problem. I was convinced that it would always cost too much and I turned it down for our cars.
Our research and engineering staffs continued to work on the various types of automatic transmissions. By 1934 a group of engineers in the Cadillac Division were finally on the road that was to lead to the first mass-production automatic transmission for passenger cars, the Hydra-Matic, a modern form of automatic transmission. This special design group was transferred to the corporation's Engineering Staff at the end of 1934 to become the Transmission Development Group. The transmission they were working on was of a step-ratio type rather than the infinitely-variable type; however, it shifted automatically under torque, as do all of today's automatic drives. (Torque is the turning effect transmitted by the engine to the drive shaft.) This group also prepared production plans for different sizes of such units to meet a range of different power and load demands for the different General Motors cars.
A set of pilot models was built, tested, and turned over to the Oldsmobile engineers. During 1935 and 1936 thousands of test miles were run on different experimental units from one end of the United States to the other. In 1937 both Oldsmobile and Buick (1938 models) came out with these semiautomatic transmissions. (A semiautomatic transmission is one which provides a range of step-ratio shifts with one or more being hand selected, and one or more automatically selected.) These were manufactured by the Buick Division and still required the use of a main clutch pedal for starting and stopping. Our engineers now discovered that the main clutch and its pedal could be eliminated by the use of a fluid coupling built within the transmission assembly. This feature, together with the development of full-range automatic controls, resulted in the Hydra-Matic transmission, produced by the newly organized Detroit Transmission Division. It was announced in October 1939 and first appeared on the 1940 Oldsmobile. The Cadillac Division was the next to accept the new transmission, for its 1941 model.
Meanwhile a different kind of automatic transmission was under development by the GMC Truck & Coach engineering staff. This was known as a torque converter of the closed-circuit, fluid-turbine type. Such devices contain a set of bladed wheels, the blades being set at angles so that one bladed wheel, driven directly by the spinning of the engine, can pump the body of contained fluid into a second bladed wheel connected to the drive shaft, and so cause turning force on that shaft. There may be additional bladed wheels for changing the fluid-flow characteristics and in this way affecting the difference in speeds between the engine and the drive shaft—in other words, their speed ratio. This ratio, in a fluid torque converter, changes imperceptibly and gradually, rather than by a series of steps. The net drive effect is therefore very smooth.
The fluid torque-converter design with which General Motors engineers first worked had been developed in Europe. They eventually designed one which conformed better to American bus operating standards. We first used such a transmission in 1937 in our own buses and it was soon wi
dely accepted. On the eve of the war, in October 1941, our Engineering Staff Transmission Development Group was at work on the problem of adapting the fluid torque converter to passenger cars.
With America's entry into the war, our advanced work on automatic transmissions for passenger cars was suspended, but an enormous new field for automatic transmissions opened. For the passenger-car driver, the automatic transmission is of value because of its convenience and simplicity in operation—there is one less thing about driving a car he has to think about. When it comes to buses, trucks, tanks, tractors, and the huge vehicles of modem warfare, automatic transmissions are needed for smooth functioning. As early as 1938 we had been urged by the military engineers to think about the problem of designing transmissions for large vehicles such as the M-3 and M-4 tanks. At this time these were steered by levers, and in some cases the operator had to let go of one of the steering levers in order to shift gears. In doing this he temporarily abandoned steering control. Furthermore, the speed of the vehicle during the gear-change interval would fall off rapidly and perhaps cause a stall, thus presenting a stationary target.
The Engineering Staff Transmission Development Group designed heavy-duty HydraMatics for these tanks. But there were heavier tanks being planned to carry bigger guns and more armor, and for these we explored the possibility of applying the fluid torque converter. Shortly after our entry into the war, the Engineering Staff built a pilot model of a fluid torque converter which solved the problem of maintaining vehicle motion while the ratio between the speed of the engine and the speed of the vehicle was being changed. Large numbers of these transmissions were built during World War II by General Motors' divisions.
Our Transmission Development Group also designed a specialized tank transmission and steering system known as the cross drive. This made it possible for a driver to control accurately, with a relatively small effort, the steering, braking, and automatic drive of big vehicles of more than fifty tons. These cross drives went into gun carriers, amphibious and regular cargo carriers, and other vehicles of tremendous weight, and our development work in this field continued after the war.
With the war's end the Engineering Staff began an intensive research program designed to adapt the fluid torque converter to passenger cars. This program was successful, and led to the Buick Dynaflow of 1948 and the Chevrolet Powerglide of the 1950 fine. The Dynaflow was the first fluid torque converter produced in volume for passenger cars.
Thus, by 1948, after many years of research and engineering development, General Motors offered to the public two different fully-automatic transmissions—Hydra-Matic and the fluid torque converter—which could be produced economically and efficiently even for low-priced cars. From the beginning, the car-buying public showed its approval of automatic transmissions—available on all of our cars—by its willingness to pay extra for them. Other automobile manufacturers used them in their cars as soon as they could—and in some cases the automatic transmissions used in their cars were built for them by General Motors. In the model year 1962 about 74 per cent of all the passenger cars sold in the United States—including General Motors' cars—were equipped with automatic transmissions. Among General Motors' passenger cars, 67 per cent of the Che violets, 91 per cent of the Pontiacs, 95 per cent of the Buicks, 97 per cent of the Oldsmobiles, and 100 per cent of the Cadillacs had automatic transmissions. During the 1962 model year about five million automatic transmissions were marketed by the industry, of which about 2.7 million were on General Motors cars. Thus this optional device has become an established feature of the American automobile.
Balloon Tires and Front-Wheel Suspension
From the beginning the problem of supplying a smoother and softer ride has been one of the most complex in automotive engineering. Since a car went much faster than a horse-drawn vehicle, it communicated the irregularities in the road surface to the passengers with greater intensity. The internal-combustion engine added its own source of discomfort in the form of vibration. Consequently, improvements in the cushioning of the driver and passengers were necessary, and this need increased as cars became speedier.
One basic approach to this problem was through the tires. Early motorcars had used solid-rubber or vented solid-rubber tires. These were soon replaced by inflated tires, but in this early stage neither the rubber nor the construction was good enough, and interminable tire-changing was a sad necessity on any extended trip.
By the early twenties the rubber companies had learned a good deal about construction methods, chemistry, rubber curing, and selection of materials. Tires were much better, and engineers began to consider the possibility of low-pressure tires, which would create a softer and more resilient air cushion under the wheels. Many problems had to be met, particularly in connection with steering and ride. The engineers had to deal with front-end instability, scuffing of the treads, squeals on turns, driving under fast braking conditions, and a peculiar condition known as wheel tramp, caused by a slight imbalance of the rotating mass of tire and wheel. These phenomena did not show up as major problems until car owners began to take long road trips at high speeds.
During this development of modern, low-pressure tires, General Motors engineers made important contributions because of our many miles of test road work under varying conditions. The General Technical Committee from the first maintained close contact with the tire industry, co-operating in standardization of sizes, and in the establishment of the best types, treads, and sections. Our recommendations, based on our research, have been incorporated year after year in better and safer tires.
The second basic approach to the improvement of the ride, and one of greater engineering complexity, was by way of the suspension—the attachment of the wheels to the chassis.
In one of my early trips abroad, my attention was called to an engineering development used in the production of European cars —the independent springing of the front wheels. Up to that time, independent springing had not been used in production cars in the United States. The use of this principle, of course, would add considerably to the comfort of the ride.
In France I came in contact with an engineer named Andre Dubonnet, who had given considerable study to the matter and had taken out a patent on one form of independent springing. I brought him back to this country and put him in contact with our engineers.
Quite independently, Lawrence P. Fisher, then general manager of our Cadillac Division, had engaged a former Rolls-Royce engineer, Maurice Olley, who also was interested in working on the problem of ride. Mr. Olley recorded his recollections of the development of independent suspension in a letter he has written for me. I will continue the story in his words:
You have asked for my recollections of independent suspension on General Motors cars . . . You'll have to excuse the very personal atmosphere of the following notes, which may give the impression that independent suspension was a one man show. It was very far from that, and owes a great deal to Henry Crane, Ernest Seaholm [chief engineer of Cadillac], Charles Kettering and a number of Cadillac and Buick engineers. Also to the tolerance and constant support of L. P. Fisher, who accused the writer at that time of being the first man in GM to spend a quarter of a million dollars in building two experimental cars!
You will recall that I came from Rolls Royce to Cadillac in November of 1930. Frankly I was surprised to find Rolls Royce so popular. A Rolls Royce car had just completed a phenomenal test at the new GM Proving Grounds, and had been torn down for inspection . . .
At Rolls Royce, for the past several years, we had been engaged in a concentrated drive on riding quality. The British factory had become intrigued by this work because of the fact that cars which were considered acceptable on British roads, were far from acceptable when exported, even to the improved roads of the United States. And we were beginning to realize that this was not because . . . American roads were worse, but because the waves in them were a different shape.
A great deal of work had been done at Rolls Royce
along the lines of swinging cars from overhead pivots to measure their moments of inertia . . . measuring the stiffness of chassis frames and coachwork . . . and measuring the suspension rates of the springs as installed on the actual car. The British factory had also developed one of the first practical ride meters, which consisted simply in measuring how much water was lost from an open-topped container in a measured mile at various speeds.
Some of this practice had been carried over to Cadillac in 1930, and soon we also were swinging cars, measuring installed spring rates, etc. We also built ourselves a "bump rig", along the Rolls Royce lines (the first in Detroit) and used it to produce a synthetic ride on a stationary car.
Early in 1932 we built the "K 2 Rig" . . . consisting of a complete seven passenger limousine, on which it was possible, by moving weights, to produce any desired changes in relative deflection of front and rear springs and in the moment of inertia of the vehicle. No instrumentation was used on this to measure ride. With the assistance of Henry Crane, to check up on our efforts, we simply asked ourselves under which conditions we got the best ride.
This was the best method because we did not know then, and do not know today, what a good ride is, but we could make so many fundamental changes in ride on this vehicle in a single day's running, that our impressions remained fresh, and direct comparison was possible.
It was at this stage, early in 1932, that we began to feel the urge towards independent suspension. The K 2 Rig was telling us, in no uncertain terms, that a flat ride which was an entirely new experience, was possible if we used front springs which were softer than the rear. But you will recall that all attempts to use extremely soft front springs with the conventional front axle fell down badly, because of shimmy . . . and a general lack of stability in handling . . .
My Years With General Motors Page 28
