Who invented the first automatic transmission: history of invention

The question of who invented the first automatic transmission often leads to the name Oscar Banker, but the real history of the creation of an automatic transmission began much earlier, with the patents of the Sturtevant brothers in 1904. It was then that the first two-stage planetary transmission was born, which was installed on a car Sturtevant, although it was characterized by extreme unreliability and sharp jerks when switching. This engineering solution became the foundation for all subsequent developments in the field gear shift automation, relieving drivers of the need to constantly operate the clutch lever and pedal.

The development of technology followed the path of improving hydraulics and planetary mechanisms, which ultimately led to the emergence of a full-fledged hydraulic transmission. The path from the first primitive attempts to mass implementation took several decades, requiring the solution of complex problems in controlling oil flows and coordinating gear rotation speeds. Today we perceive automatic transmission as a standard of comfort, but behind this lies the colossal work of engineers of the early 20th century, who were looking for a way to make driving accessible to the masses.

Prerequisites for creating an automatic transmission

Before the advent of automatic transmissions, driving a car required significant physical effort and constant attention from the driver. The manual transmission of that time did not have synchronizers, which made changing gears a complex process requiring double depressing of the clutch and precise selection of engine speed. Any driver had to have good coordination in order to coordinate the operation of the shift lever, gas pedal and clutch, especially when starting up a hill or in heavy traffic.

Engineers were looking for a way to simplify this process by turning to planetary gears that were already used in some industrial units. Planetary gear made it possible to change the gear ratio without interrupting the power flow, which was a key advantage over conventional gears. However, controlling these mechanisms required a reliable drive, and it was the introduction of hydraulics that became the breakthrough that made it possible to create a working machine.

Early attempts at automation often faced the problem of harsh shifts, which could lead to transmission failure or even an accident. It was necessary to create a system that would smoothly transmit torque and change gears depending on the speed and load on the engine. This required the development of complex hydraulic valves and regulators that could respond to changes in vehicle operating conditions in a fraction of a second.

The Startevant brothers and the first patent of 1904

The answer to the question is who invented the first automatic transmission, formally the Sturtevant brothers, who received a patent in 1904. Their device was a two-stage planetary gearbox that switched automatically when a certain speed of rotation of the output shaft was reached. The design used centrifugal weights, which, under the influence of centrifugal force, moved apart and actuated the brake bands, fixing the elements of the planetary gear set.

Car Sturtevant, equipped with this innovation, became the world's first production car with an automatic transmission, although production did not last long. The main disadvantage of the invention was its extreme unreliability: shifts occurred with a strong jerk, which often led to the destruction of gears and other transmission components. Drivers of that time complained that the car behaved unpredictably, and the resource of the unit was hundreds of kilometers.

⚠️ Warning: Despite its historical significance, the Sturtevant brothers' design was too primitive for mass adoption and did not have hydraulic control, which made its use dangerous.

Despite the commercial failure, the idea of automatic switching using centrifugal forces was correct and was subsequently developed in other designs. Engineers realized that for reliability it was necessary to eliminate mechanical friction and shock by switching to transmitting force through a liquid. This paved the way for research in the field of hydrodynamic transmissions, which became the basis of modern torque converters.

General Motors developments and the emergence of Hydra-Matic

The real breakthrough in the field of automatic transmissions occurred in the late 1930s, when the company General Motors together with Oldsmobile began work on creating a fully automatic transmission. The chief engineer of the project was Earl Thompson, who developed the design, called Hydra-Matic. Introduced in 1939, this transmission was the first in the world to combine a four-speed planetary gearbox with hydraulic shift control.

The key element of the new system was the torque converter, which replaced the dry clutch and ensured smooth transmission of torque from the engine to the wheels. The hydraulic control system used oil pressure to engage the friction elements, making shifts virtually imperceptible to the driver. This solution made it possible to significantly improve driving comfort and extend the life of the transmission compared to mechanical analogues.

In 1940 Oldsmobile began mass production of cars with gearbox Hydra-Matic, and the success was overwhelming. Buyers appreciated the ability to drive by simply pressing the gas pedal without having to think about changing gears. Soon after this, similar transmissions began to be installed on cars of other brands, including Cadillac, Pontiac and even British Bentley and Rolls-Royce.

Evolution of designs: from torque converter to robots

Many years have passed since the appearance of the first full-fledged automatic transmission, and transmission designs have undergone significant changes. While early models relied on pure hydraulics and vacuum regulators, modern systems are controlled by sophisticated electronics. Electronic control allows the box to adapt to driving style, road conditions and engine condition, providing optimal dynamics and fuel efficiency.

In parallel with classic automatic transmissions, other types of transmissions also developed, such as variators (CVT) and robotic gearboxes (DCT). CVTs use a belt or chain drive with variable pulley diameters, providing a continuously variable transmission ratio. Robotic boxes, in turn, are a mechanical transmission with automated clutch and gear shift control.

Modern 8-speed and 9-speed automatic transmissions allow engines to operate in the most efficient speed range, reducing fuel consumption and emissions. Engineers continue to improve designs, introducing new materials, improving control algorithms and increasing the efficiency of torque converters. Today, an automatic transmission is a high-tech unit that is an integral part of the overall vehicle control system.

Technical features of early automatic transmissions

Early automatic transmissions were simple in design, but had a number of serious limitations compared to modern equivalents. The lack of electronic control meant that all gear shift decisions were made based on mechanical oil pressure and centrifugal forces. This resulted in switching algorithms being hardwired into the valve design and unable to adapt to changing conditions.

An important element of early automatic transmissions was fluid coupling or a simple torque converter that did not have a locking mechanism. This meant that even when driving at a constant speed, some of the engine's energy was lost to mixing the fluid in the torque converter. The efficiency of such transmissions was lower than that of their mechanical counterparts, which led to increased fuel consumption.