A Brief History of Tractors


Authors note: The purpose of this blog is to open a conversation about tractors. It is intended for the small to medium sized farmer. I believe that the best way to start this type of conversation is with a bit of history to set the stage.

In colonial times, oxen were the mainstay of colonial farmers. They were cheap. To continue producing, milk cows need to be dried off — stop producing milk and bred. If the calf is a bull, it is easy to make it into an ox. Another advantage of oxen is they can be worked hard immediately after a layoff. On the other hand, if a horse is worked too hard after a layoff, it can founder.

As farms grew in size, horses became increasingly important. The opening of the west to farming could not have occurred without the horse. Horses are faster than oxen, so they can cover more ground. In the first part of the twentieth century, the focus slowly shifted to tractors as farms continued to grow.

Early tractors were essentially steam locomotives built to run on roads instead of rails. They were known as traction engines. In their new role, a different drive system was designed. The steam produced by the boiler was used to drive a piston connect via a connecting rod to a crank shaft. The crank shaft turned a bull gear. The bull gear then turned the wheels through a clutch and a chain driven transmission system. These tractors were large and very heavy. Many of the very early ones were not even self-propelled — they would be towed to where a source of energy was needed. A sheave drove a belt that that ran a thresher or other stationary machine.    

Due to their size and slow speed, the traction engines were replaced in the early twentieth century with gas engine tractors. At first, these were nearly as large as the smallest steam tractors. Indeed, they even used iron wheels. Many had various types of spikes to provide traction in the fields. Amenities on both the steam tractors and the early gas tractors were nonexistent. A few had sheet metal roofs and — if you were lucky — a seat. Implements, for the most part, were adapted from horse-drawn equipment and towed behind the tractor.

The next revolution in tractors was the three point hitch. The three point hitch takes it’s name from the three points of attachment between the tractor and the implement. Two lower arms are attached under the rear axle of the tractor via a ball joint that allows them to pivot sideways and up and down. The lower links or arms attach to two lift links that are raised using a hydraulic piston mounted under the driver’s seat in the upper section of the axel casting. The third component is a top link that has ball joints like the lower links. It is attached to the tractor with a pin that passes through two cast ears just above the attachment point of the lifting links. A lever next to the driver raises and lowers the lifting arms. On many of the newer tractors it can be set to monitor the pressure on the lifting arms. For example, when plowing, the plow(s) can be set to rise automatically if they hit a rock.

Implements are outfitted with two lower pins and an upper receiver. The tractor driver backs up to the implement. On smaller tractors, the lift arms can be lifted by hand to line up with the pins on the implement so the ball sockets in the lower links slide over the implement’s pins. They are secured in place with clevis pins. The top link is then pinned in place. The top link and at least one of the lower links are adjustable to aid mounting.

The three point hitch combined with the rear power take off (PTO) opened the door to a whole new world for farmers. Now they can “pick up the” their implements and transport them from the field. Gone are the days when implements had to be picked up and loaded on a truck, wagon or trailer to move them from job to job. The addition of rubber tires made this more comfortable and faster. The PTO spawned a whole line of driven implements. Many were improved versions of horse draw implements, but many were brand new. To name a few: hay baler, sickle bar mowers, corn choppers, rotary and flail mowers, silage choppers, threshing machines (or combines as they are now called) and cordwood saws. Another revolution occurred with the addition of hydraulic pumps to tractors. Now front end loaders, log splitters and post drivers were added to the list. Later still, the diesel engine led to the modern tractor.

As you can see, there was a steady evolution from oxen to tractors. Without this evolution, the United States would never have become the breadbasket of the world. Today we are at a crossroads that will shape the future of both the United States and the rest of the world. Do we continue with factor farms or do we step back and move towards smaller local farms?

It is interesting to note that in the 1926 the U.S. Department of Agriculture’s Yearbook of Agriculture lists that a skilled tractor driver is the most important part of owning a tractor. It also points out that on large northwestern farms a 40hp tractor is the most popular. Gee, I wonder what the old timers would say about the John Deere 9030 that puts out 530 hp?

Disclaimer: The manufactures of the tractors mentioned in this blog own copyrights to the tractor names and equipment. The use of the names in this blog is for illustration and ease of writing only and does not construe a recommendation of one brand over another.