Making Tracks with Crawler Tractors

Tractor expert Bob Pripps traces the evolution of crawler tractor steering systems.

| May 2016

A lot of antique farm tractor buffs have never driven a crawler tractor and may not have considered the unique difficulties in steering these machines, or how steering systems have evolved since the first crawlers crawled. It is generally understood that crawlers are controlled by a pair of steering levers (in some cases, a “T” handle, or even a steering wheel), but most people don’t bother with what happens beyond that.

Crawler tractors were born of necessity at the turn of the 20th century in the rich, but boggy, farm lands of the Sacramento, California, River delta. Gigantic wheat farms required big, heavy, steam tractors and combines, both of which were made by the competing Holt and Best manufacturing companies. These big-wheeled monsters frequently sank in the bog, and when they did, there was nothing available to pull them out. 

As early as 1858, a successful steam-powered traction engine with crawler tracks had been demonstrated by inventor Warren Miller in nearby Marysville, California. The tracks provided the necessary flotation and traction to work on the soft land. Apparently Miller built only one machine, but others followed, including units by Minnis (1869), Parvin (1871), Stratton (1893) and Lombard (1900).

These machines all used individual steam cylinders for each track; consequently, a differential between the tracks was not required. Steering was accomplished by means of a front tiller wheel. In the case of the Minnis, the tiller was a track also powered by a separate steam cylinder. The Lombard (used exclusively in the north woods for winter log hauling) used skis reminiscent of those on today’s snowmobiles.

Solving the gas engine challenge

By the early 1900s, both the Best and Holt companies were converting their steam traction engines to crawler tracks. Both soon saw the advantage of internal combustion gasoline engines and each developed their own. Holt and Best continued that vigorous competition until 1925, when they merged to form Caterpillar.

When going to the gasoline engine, the problem of delivering power to the tracks became more complicated. The tiller wheel did not have enough authority to overcome the tendency of the tracks to continue in a straight line. Holt solved this problem on its 1907 gasoline-powered crawler by including steering clutches in the drive for each track. By disengaging drive power from the “inside” track, the tiller wheel could then negotiate the turn. Holt did not add track brakes to assist in steering until 1918. The tiller wheel was controlled by a conventional steering wheel at the operator station through a series of shafts, universal joints and a worm-sector gear.