Hydraulics

The Ferguson three-point hitch system was the first agricultural use of a technology that was predicted centuries ago and developed for other industries in the 1700s – hydraulic power. This technology made a huge difference in the power and control of agricultural implements.

The idea for hydraulic cylinders goes back to the French mathematician Blaise Pascal. He studied fluids, pressures and vacuums in the mid-1600s, four centuries ago. What Pascal discovered is that fluids don’t compress in the way that air will. In other words, if you put pressure on a fluid in one area, it will transmit pressures equally in all directions. Under this principle, imagine you have a bottle with a one-inch square opening filled with liquid. Imagine you put 10 pounds of force on the top of a cork in the neck of the bottle. Pascal’s Law says that the same 10 pounds of force would be applied on each and every square inch on the insides of the bottle.

It took another 140 years and the dawn of the Industrial Revolution for that scientific principle to be applied in a useful way. Joseph Bramah was an inventor and successful locksmith in England. In 1795, he patented his “Hydrostatic Machine” to help build another of his inventions, an unpickable lock. Bramah took two cylinders – one small and the other large – filled both with liquid and connected them by a pipe. He realized that, using Pascal’s principle, putting pressure on the top of the narrow cylinder would force the liquid to put a huge amount of pressure on the larger cylinder. When he and a colleague figured out how to build cylinders with matching pistons that were sealed with leather, self-tightening collars, they had the basis of the hydraulic press. The press has been used in thousands of industrial applications over the next 150 years.

Here’s how it works. [If you’d rather jump to what it means, click here.] Suppose you have one cylinder with a piston at the top that is two-inches in diameter and another cylinder that is six-inches in diameter. To figure out how much more force you can produce on the large cylinder you have to figure out the area of both cylinders. The formula for the area of a circle is A = Pi * r² where “r” is the radius and the radius is half the diameter.

• So, the area of the small cylinder is (1*1) * Pi = 3.14.
• The area of the large cylinder is (3*3) * Pi = 28.26.

In other words, the piston in the large cylinder is nine times larger than the piston in the small cylinder. So, if you apply 100 pounds of force to the small cylinder, you will get 900 pounds of force on the large cylinder. The trade off is that you will only raise the large cylinder one-inch for every nine-inches of travel on the small cylinder.

Later inventors realized that they could substitute pumps for the small cylinder to force liquid under pressure into the large cylinder. That opened up new applications for hydraulic power, including applications in industries like agriculture.

So, 150 years after the invention of hydraulic presses, the stage was set for Harry Ferguson and Henry Ford to adapt the hydraulic press to the Fordson Tractor. Other manufacturers had used hand-operated levers that were limited in their range of motion and tiring to operate. Others tried mechanical lifts using power from the engine, but the movements were too inflexible. Then, manufacturers tried air pressure to raise and lower implements. But because air will expand and contract, the implements would bounce instead of raising or lowering smoothly.

Liquids don’t compress, so power can be transferred smoothly and produce tremendous force.

The other innovation that Ferguson brought to the hydraulic three-point hitch was a sophisticated feedback mechanism that would adjust the hydraulic cylinder and the plow up if it started to plow deeper. The Ferguson system would automatically keep the plow at the level that was set by the control lever on the tractor.

What hydraulic power meant to the farmer. According to historian Robert C. Williams in Fordson, Farmall, and Poppin’ Johnny, within a few short years, “the Ferguson system, or a similar hydraulically controlled, three-point [hitch] system, became virtually mandatory on almost all tractors.”

Hydraulic systems could lift much more weight than any hand-powered lever. The new technology made it possible for agricultural engineers to design and build larger and larger implements to match and make possible more powerful tractors.

Hydraulic systems could also control the larger implements with more precision, making it possible for machines to perform delicate operations that used to require manipulation by hand.

Orville Hoffschneider identifies hydraulic systems as one of the biggest changes that he saw in his six decades on the farm. “That was a terrific help,” he says.

Within a few years, hydraulic cylinders were being installed not only on tractors, but also on the implements, as well. With flexible, high pressure hoses, a tractor’s hydraulic pump and levers could control cylinders on the implements mounted behind it.

Hydraulic systems produced a quiet revolution on farms around the world.

Written by Bill Ganzel, the Ganzel Group. A partial bibliography of sources is here.