Belt Pulleys Turned Tractors into Portable Power Units

When you think about antique tractors or read about them in the pages of Antique Power magazine, you probably picture them working, on the move across a field. In traditional farming, the tractor is pulling a plow, mowing, or doing some other job involving an implement usually powered by a pto driveshaft, located on the back or side. International Harvester led the way with a pto on its Model 8-16 tractor in 1918. However, long before this technology, farmers regularly used tractors, like portable powerplants, in addition to what we think of as normal agricultural uses.

Tractors powered equipment through a wide, flat, continuous belt made of some flexible material like leather, layers of canvas, or rubber. This belt was under a certain amount of tension. With one end looped around the tractor’s flywheel or belt pulley and the other around the same on a separate piece of equipment, the tractor transferred power. In this situation, both the tractor and the equipment that it powered were stationary. It would not be practical to try to be mobile with a belt that is up to 50 feet, which is a belt size that might be used with a threshing machine or baler.

Belts required good maintenance. Just as a chain is only as strong as its weakest link, a belt is only as strong as the point where the ends are joined. Here’s a look at a North Dakota Agricultural College Cooperative Extension document from 1937, showing belt lacing pattern diagrams.

Some other examples of the types of equipment powered through a tractor’s flywheel or belt pulley, in addition to threshers and balers, are buzzsaws, hammer mills, burr mills, and pumps. Jobs included grinding feed for livestock, making shingles, cutting firewood, and much more. Keep in mind that life on a farm in the late 19th and early 20th centuries called for great self-sufficiency and plenty of hard work. Tractor power made it easier.

While doing some research, I found on Google Books, an old book published in Jan. 1, 1922, with information about the use of belt-powered equipment operated by tractors. Titled Manual in Agriculture and written by Frank Luverne Bennett, the book has the longest subtitle I’ve ever seen: Material and Suggestions for Use in the Schools of South Dakota in Connection With the State Course of Study.

It stated: “The increase of the use of belts in America has been due to the many uses to which the small tractor may be put, especially to belt driven machinery. This is shown by the report of a threshing machine company in which it stated that in 1916 less than one per cent of their machines were of small size; in 1917 their sales rose to sixteen per cent; and in 1920 to sixty-five per cent. These small threshers may be run successfully by a belt attached to a small tractor. The same conditions prevail among manufacturer of belt driven machinery. The small tractor makes the farmer the owner of all the necessary belt driven machines.”

Farmers could not afford to waste power any more than they could afford to waste water, seed, or anything else. The use of belts became almost a science. The size, weight, amount of friction, positioning, tension, speed, and the distances between the tractor and whatever equipment it was powering affected efficiency. The proper speed depended on the type of equipment being powered and the job that it was intended to do.

For example, the book also pointed out that, “The cylinder of a threshing machine should revolve at a proper and constant speed: too fast and a great many kernels of the grain will be cracked; too slow and not all the grain will be threshed from the straw.”

Belt pulleys also played a part in the testing done at the University of Nebraska Tractor Testing Laboratory. These Nebraska Tractor Tests provided valuable information to consumers, so they could be sure of what they were buying. Previously, manufacturers regularly engaged in gross exaggerations of their products’ attributes. In the tests, horsepower measurements were taken at the drawbar and the belt to check for power output. 

The pto, which had been around since the early 20th century, would eventually dominate over the belt pulley. In 1920, International Harvester’s Model 15-30 was the first tractor with a pto to undergo the official testing. The last belt horsepower test was conducted in 1959.

Just as so many of us love to just look at antique tractors, the practical use of a tractor to power other equipment, or even another tractor, continues today! In the video below, one old tractor is used to start another through the power of a belt drive.

Enjoy watching these good old tractors still reliably doing a job.

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