Its beginnings were humble; its future, bright. As power transmission participated in the business of Nation-building, it grew and prospered right up to the present. Here are a few highlights, with some emphasis on power transmission control
Did you know, for example, that American involvement in electric circuitry began in the mid 1700s with Ben Franklin’s study of the Leyden Jar? It clarified the capacitor effect and the function of the insulator. His work also fathered the terms plus and minus or positive and negative and probably had a more profound effect on the human condition than his more popular study of lightning. Or did you know that America’s oldest surviving industrial company, the J.E. Rhoads Co. of Newark, Del., is today a maker of industrial belts? It was founded in 1702 near Philadelphia as a tannery.
Did you know that perhaps one of the earliest attempts at lobbying a legislative body came in behalf of a power transmission system? In 1787, John Fitch gathered members of the first Constitutional Convention at Philadelphia’s Water Street pier to see his steam-driven, oar-propelled boat. He wanted government development funds. They watched it row at 6 mph, shrugged, and went back to constitutionwriting. Fitch’s ideas got better but he died broke, his dreams unwon. However, others followed because transportation was so essential to the Nation’s development.
By the 1850s, steamers were replacing Clipper ships, bringing east and west coasts closer. Steam became king for most transportation after that, and was coming on strong as an industrial prime mover, even though the first embryonic pulsations of the electric motor appeared in 1829. Joseph Henry at Albany academy in New York State devised and constructed an early version of the electric motor. That same year he built a shortcoil magnet, basically the one used in modern motors and generators. And in 1832, independently of but simultaneously with Faraday, he discovered electromagnetic self-induction.
Reciprocating steam engines were lumbering monsters and paddle wheels churned slowly. Rod-and-crank mechanisms became the means of delivering power from engine to sea. Early propeller- driven ships depended on rods and cranks too, though those of the late 19th Century needed more elaborate powertransmission mechanisms for propulsion, cargo handling, and control. Today’s steam-turbine and diesel-engine-driven ships need high-power gear drives, clutches, couplings, and other components, along with complex controls. Imagine what a 20,000-shaft-hp ship’s power plant and drive line must go through in a full-speed-forward, crashstop- reverse maneuver.
Forty-three years after Fitch’s lukewarm reception in Philadelphia, Peter Cooper raced the Tom Thumb against a horse-drawn rail car. He chose a gear and belt-driven transmission to match engine speed to practical track speed. A belt slipped from its pulley and cost him the race, but the future bankroller of the Cooper Union free educational institution showed that mechanically driven transportation was on its way.
Like reciprocating-engine ships, however, later steam locomotives used rods and cranks. Diesel electric locomotives arrived in the 1930s. In most, engine generators supply current to dc motors geared to drive axles. Dynamic braking on downgrades and stops lets the motors generate current that heats resistors — the regenerative version of which in many modern industrial drives puts power back into the supply lines. The most modern locomotives use ac motors.
Power transmission helped make the Nation mobile, but it had a more basic job feeding a surging population. From the beginning of our largely agrarian society, big native families and heavy immigration burdened agriculture. And the Industrial Revolution lured workers from the fields. Westward movement opened vast farm lands, but the horse and plow couldn’t keep up alone. McCormick and others developed machinery to produce more, and they needed gears, belt and chain drives, and bearings. Fortunately, work was underway on many of those components. In 1839, for example, Isaac Babbitt combined tin, lead, and antimony to form the first practical bearing metal.
Better stationary and draft power were essential, however. It wasn’t until 1855, 24 years after McCormick’s reaper appeared, that Obed Hussey of Baltimore invented and ran a steam plow. The federal government’s eye was on powered farming early. In 1859, President Lincoln, addressing the Wisconsin State Agricultural Society, cautioned: “...[the steam plow] must...plow better than can be done with animal power. It must do all the work as well, and cheaper, or more rapidly, so as to get through more perfectly in season, or in some way afford an advantage over plowing with animals.”
By 1870, more than 2,000 U.S. establishments were producing farm machinery. Much of it involved steam power. In the 1870s the demand swelled for self-propelled engines to move threshers. From then into the 1890s, steam tractors had their “hayday.” A typical propulsion transmission was a train of cast iron spur gears. A friction clutch joined the engine crankshaft to a pinion that engaged an intermediate gear. The intermediate engaged a large compensating gear on a countershaft. A pinion on each end of the countershaft drove a main gear at each drive wheel.
The predominant automatic engine speed control was the fly-ball governor. If engine speed began to rise, a small takeoff mechanism from the crankshaft increased the rotary speed of two or more massive whirling balls. Increasing speed tended to swing the balls in a bigger circle, but they were connected to a linkage. It closed down on the steam throttle as the circle grew. On decreasing engine speed, the reverse happened — the decreasing circle changed the linkage to open the throttle more.
As the 19th Century closed, internal combustion engines went to work. Gasoline- engine tractor development proceeded rapidly, and by 1910 competition between steam and gasoline was intense, producing plowing and pulling contests, and claims and counterclaims. Higher engine speeds and different torque characteristics of gasoline engines created a new set of drivetrain problems. Most early drives were spur gear trains from engine to wheels, though some added a roller-chain-drive stage. One of the earliest models, the 1894 Otto, included bevel gears and a driveshaft in the first reduction. Some friction drives appeared, too, but they never became popular.
The friction drive did offer integral clutching. Gear or chain transmissions required a separate clutch. As the gasoline tractor matured, it tried many clutches for drive speed and torque control: friction disc, external band, expanding shoe, and cone, among others.
Several models included a planetary gear drive for reverse. By 1919, slidinggear transmissions with at least two forward and one reverse speed were common. Later developments brought final-drive gearing into dust-free enclosures. Better materials reduced weight and improved effective drawbar pull. Better sleeve and rolling-element bearings meant fewer in-field changes. And better drive lines, steering systems, and controls came forward, helping make today’s tractor the true workhorse of American agriculture. The same is true for farm machinery in general.
Food processing, too, called for ever more power transmission equipment as the 19th Century closed. Population growth and the shift of hands from fields to factories also burdened that industry. New plants continually sprung up, demanding more modern machinery as packers, dairies, mills, and canneries followed population and source movements.
The factory system of manufacture in the U.S. began in New England. In 1790, a former colonist with a good memory convinced two Rhode Island merchants he could make a water-powered spinning machine like one he had run in England, and they built a spinning mill. A major English manufacturing secret thus leaked to those who would use it well to make the Nation independent in textiles. By 1800, seven more mills appeared in New England; soon, hundreds of mills and factories.
Yankee ingenuity kept improving the machines that started the English Industrial Revolution. Water-powered mills, easily disabled by ice or drought, converted to steam. Leather-belt and gear drives served in great numbers.
In 1850, the factory system served only the textile industry on a large scale. The Nation had just one big steel mill. The first assembly line, at Singer Sewing Machine Co., started up late in the decade. The Civil War spawned factories for all kinds of goods. National output surged.
Increased use of steam power continued, partly because factories had to be built where hydropower was infeasible. Pressure rose for more coal and basic metals. Though coal mining in that period was limited mostly to pick and shovel, power transmission helped by lifting and pumping. The high degree of manual labor, however, coupled with unsafe mining practices that were taken for granted previously, produced injury and death along with coal. The American Labor Movement can trace its beginnings to shoemakers in 1794, but it began to roll in earnest in the 1870s because of high death rates among miners.
The handwriting was there for forward- looking industrialists: Labor could no longer be considered unlimited, cheap, and expendable. Moreover, competition here and abroad was growing. If a machine could do it faster, cheaper, or with no mortal in attendance, let it be done. Efficiency became the watchword, and a new kind of engineer came aboard. His mission: Control waste of material, manpower, and energy. That much, management demanded and would finance.
Carnegie was told that steel could be made 50 cents a ton cheaper in a new mill. He ordered it built. Two month’s experience on the new mill showed that waste could be reduced by $1 a ton more. He ordered the new mill razed and a newer one built to replace it. The Efficient Machine Age was at hand.
In the 1890s, two events thrust U.S. industry into a growth period still here:
• The successful end of the Spanish- American War sealed the fate of the U.S. as a political and military world power, while burgeoning industrial might thrust it irrevocably into world economics.
• Cheap electric power allowed new applications of old materials and principles, and whole new ideas.
In 1882 in New York, Edison opened the Pearl St. Station, the first central power station. He invented the incandescent lamp 3 years earlier, bringing electric lights into buildings. Soon, motors replaced water-wheels and engines to run lineshafts.
Power companies would face idle generators in the daytime if lighting were the major draw. They pushed motor-driven devices. By 1890, motor sales boomed.
Edison’s hold would be tested, however; another giant was coming. In 1885, George Westinghouse bought the rights for an ac transformer from two Englishmen and redesigned it. In 1886, he formed the Westinghouse Electric Co., and lighted a town with ac. Westinghouse knew Edison’s grip on the electrical world. DC motors were already there, feeding upon Edison’s generators. Westinghouse needed an ac motor. In July 1888, he bought Nikola Tesla’s polyphase ac patents and hired the Serbian genius. Tesla brought along his ac motor ideas and the giants went to battle.
The future for ac was sealed in the mid 1890s as Tesla’s crew perfected long-distance transmission, while Westinghouse developed the steam turbine.
By 1892, General Electric (formed by merging Edison interests with the Thomson- Houston Co.) and Westinghouse Electric dominated the U.S. market. In 1899, they accounted for 58% of total electrical sales. In 1899, 5% of industrial prime movers were electric motors; by 1919, 81%.
Each factory machine with its own motor meant new concepts in plant location and layout.
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Electric control meant tuning production to unheard-of efficiencies. And controlling speed was essential to any system intended to be efficient and versatile. In 1904, Reuben Hitchcock and John Lincoln started the business which later became Reliance Electric. One of their first products was a dc motor that had a speed range greater than 2:1. Their Type AS adjustablespeed motor had a tapered armature, quilled onto a shaft to give lateral movement. You could shift the armature with a handwheel to get a 10:1 speed range.
Cone pulleys and change gears that gave only stepped speed adjustment gave way in many applications to infinitely adjustable speed range devices. Several mechanical types could be interposed between motor shaft and load shaft. The idea of electrical control of motor speed or some other electrical device was close to the hearts of many equipment designers, however. The eddy current drive idea popped in the minds of Anthony and Martin Winther in 1929. They founded the company that later became the Dynamatic Plant of Eaton Corp.
In the early 1930s, General Electric and Cutler-Hammer drew up cross-licensing agreements that let both make vacuum-tube equipment, but industrial adjustable speed of that type proved expensive then and tube life, a problem.
Ward Leonard motor-generator sets to adjust speed came in the 1930s.
Although Bell Labs perfected the transistor by 1949, there was limited use of transistors in industrial control until about 1957. That year, GE introduced the silicon-controlled rectifier. By 1958, some manufacturers were beginning to introduce digital controls, the first ones being tube-type; later ones, of solid-state components. By 1961, SCR drives were being custom-engineered for specific uses. Electronics began to move toward the prominent place it holds in today’s adjustable speed market.
Precision and control in high volume in this century meant better products at affordable prices. While consumer products devoured large amounts of small power transmission devices, raw-materials and capital-goods industries demanded great quantities of transmission equipment of all sorts. Two global wars and many smaller ones magnified demands. Better machinery developed to make the power transmission equipment — motor-winding machines, gearcutting systems, rolling-element bearing equipment, and thousands of others. And digital technology wrought a modern revolution in design and control with probably the most far-reaching industrial effects since the development of steam power.
The Nation’s insatiable demand for power transmission equipment continues to the present. In 1992, U.S. manufacturers’ shipments of power transmission products totaled an estimated $25.4 billion, a 15% increase over 1987 and up 35% from 1982. The largest segment of the power transmission market is now controls and sensors, accounting for 30% of 1992 U.S. manufacturers’ shipments. Motors and gearmotors follow with 22% market share.
Could we reverse the trend even if we wanted? A look at food production alone says “No.” A USDA economist estimated shortly before the 1976 Bicentennial celebration that farmers then would need 61 million horses and mules to feed the Nation without mobile agricultural equipment. It would take 180 million acres and 31 million workers to tend the animals and raise feed.