A History of Avery Tractor Development

Let's Talk Rusty Iron: Continuing the Avery Co. story with the development of the Avery tractor line.


A big Avery 40-80 tractor, showing the round, vertical tube radiator with the large exhaust pipe through the center.

Sam Moore

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Avery Co. had a successful line of steam traction engines, including the famous Avery locomotive-style under-mounted model, and promoted its threshers, plows and engines aggressively. The American Thresherman reported on the Avery demonstration at the 1906 Iowa State Fair. "These exhibition engines cut up all kinds of didos (in the slang of the era, dido was defined as behaving in a mischievous or silly way) and climbed blocks of wood 29 inches high. A little boy of 12 or 13 … operated the engine with perfect ease and made it fairly dance a jig … a plowing exhibition (was) given (by a 22 hp engine and a 10-bottom plow) in an open field where the ground was as hard as some men's conscience … 10,000 people would swarm around to see the engine tear up a strip of land several feet wide without a hitch or a bobble … "

Despite this success, Avery President J.B. Bartholomew recognized the potential of the newfangled tractors with internal combustion engines then coming on the market.

At the 1910 Winnipeg tractor trials, Avery introduced a huge, 1-cylinder model weighing more than 6 tons. The Avery tractor had a 12-by-18-inch bore and stroke, and performed so dismally it was withdrawn partway through the tests.

After the failure at Winnipeg, Bartholomew turned to Albert O. Espe, a prolific tractor inventor from Crookston, Minn., whose patents were used by the C.O.D. Tractor Co., Minneapolis Threshing Machine Co. and Advance-Rumely. Espe came up with a machine that had a horizontally opposed engine and a unique power transmission system. The new Avery was introduced in September 1911 as a 20-35 hp model that sported a huge square radiator, unlike all its successors, which had round, vertical tube radiators.

Getting a tractor engine's power to the drive wheels was a problem in the early days of gas tractors. Designers tried friction drive, gear drive forward and friction reverse, and planetary gear drives before the selective, sliding gear transmission became the norm.

Hard as it was to get the thing to go forward, backing up was something else again. A steam engine could be made to run in the opposite direction by manipulating the valve gear, causing the tractor's engine and drive gear to move in reverse. A 2-cycle gas engine, such as that on the ill-fated Hart-Parr Little Devil tractor, could be slowed enough to cause it to run in the opposite direction. (This created problems for Hart-Parr, as the Little Devil sometimes lugged down enough when pulling a heavy load to suddenly begin running in reverse, causing the tractor to back over the load.) A 4-cycle gas engine, however, turned in only one direction, making necessary some sort of reversing gear mechanism.

Espe solved the problem by mounting the engine in a cradle that slid forward and backward in the tractor's frame by means of a lever at the operator's position. The horizontally opposed engine was mounted with the cylinders to the front and rear of the crankcase, meaning the crankshaft was crosswise to the tractor's frame.

A heavy flywheel was mounted on the left end of the crankshaft. At the other end was a loosely mounted pinion gear, as well as a friction clutch controlled by a second lever on the operator's platform, to connect the pinion to the crankshaft.

When the engine slid to the rear, the pinion gear on the crankshaft meshed with a large compensating gear on a cross shaft mounted ahead of the rear axle. A small bull pinion at each end of the cross shaft was meshed with a large bull gear bolted to each rear wheel, which turned on a solid axle. In this position, when the clutch was engaged, the tractor moved forward.

In order to reversethe Avery tractor, the operator slid the engine forward, disengaging the pinion gear on the crankshaft from the compensating gear. As the engine moved forward, a small idler gear was simultaneously moved into position between the crankshaft pinion and the compensating gear, meshing with both. When the clutch was then engaged, the extra gear in the train caused the tractor to move backward.

Avery made a full range of tractors with the sliding engines. The smallest, the 2-cylinder 8-16, was a 2- to 3-plow tractor weighing 2.5 tons. The company built a 2-cylinder 12-25 as well as 4-cylinder 14-28, 18-36, 25-50 and 40-80 versions. The 40-80 weighed a whopping 11 tons and was rated to pull 8 to 10 plow bottoms. All but the 8-16 had an open-sided cab over the operator's platform and all had the distinctive round, vertical tube radiator with the exhaust stack up the center.

Later, the drive train was improved to provide two speeds forward (as well as a neutral position for belt-pulley work) in addition to reverse, although shifting was still accomplished by sliding the engine forward and back.

Avery called its "Avery Patented Sliding Frame 'Direct Drive' Transmission" the "simplest and most efficient tractor transmission built," and used the system on most of its larger tractors until the firm ended tractor production in 1924.

Avery also made two smaller tractors with in-line engines and 3-speed, selective gear transmissions (the 4-cylinder 5-10 hp Model B and the 6-cylinder Model C), as well as 1- and 2-row Motor Cultivators. In addition, the firm built trucks from about 1910 until 1923.

The Agricultural Depression of the early 1920s took its toll: Avery Co. declared bankruptcy in 1924. The firm reorganized and struggled through the Great Depression without making tractors until 1938, when it introduced the Avery "Ro-Trak." The new machine was a modern tractor with a 6-cylinder Hercules engine and a regular 3-speed transmission. The Ro-Trak had a unique front wheel system allowing the front wheels to swing together for row crop work or wide apart for plowing. Built until 1941, the Ro-Trak was a unique and interesting tractor, but that's a story for another day.

After 60 years of operation in Peoria, the Avery Co. disappeared during World War II, although many of the company's threshers, tractors and gang plows survive in collections around the country. FC 

Sam Moore grew up on a farm in western Pennsylvania. He now lives in Salem, Ohio, and collects antique tractors, implements and related items. Contact Sam by e-mail at letstalkrustyiron@copper.net