David Bradley’s Tri-Trac

Remembering the Tri-Trac, a popular three-wheel, small-acreage farm tractor.

By Jim Gay
article image
Illustration by Farm Collector Archives
Illustration from the Tri-Trac operator’s manual showing the unit’s key controls.

Three-wheel tractor with a single front wheel is not so unusual, but the Tri-Trac by David Bradley had a single drive wheel in the rear with a wide front axle. The tractor was built from 1953 to 1957 and about 4,000 were produced. Let’s start this discussion by taking a brief look at the David Bradley Mfg. Co.

David Bradley was born in Groton, New York, in 1811. After working for his brother in Syracuse, New York, he moved to the Midwest in his early 20s. He was involved with the first foundry built in Chicago, bought a plow company and, by forming a partnership with Conrad Furst in 1854, established Furst & Bradley Co. to manufacture farm implements.

During that time, Bradley also developed a chilled cast iron plow reported to scour in the heavy, sticky Midwestern soils. This prompts an interesting question (but one with no clear answer): Was this plow developed before John Deere invented his steel plow in 1837?

Bradley and his sons bought out Furst’s share of the partnership in 1884 and renamed the business David Bradley Mfg. Co. The business was moved to North Kankakee, Illinois, in 1895. City leaders later changed the community’s name to Bradley in honor of the man (who died in 1899) and the company.

Proud addition to the Sears line

In 1910, the Bradley factory was purchased by Sears, Roebuck & Co. Sears continued manufacture of implements that were sold through the company’s mail-order operation. A large number of items were added to the David Bradley product line. Some, such as farm wagons, were built by other companies, but were sold under the David Bradley name.

One of the most popular models built by David Bradley was the two-wheel walk-behind garden tractor introduced in 1946 and built into the early 60s. Four-wheel lawn tractors made their debut in the 1950s and were also a huge commercial success.

Never tested in Nebraska

The Tri-Trac three-wheel riding tractor had a styled sheet metal enclosure over the rear wheel and transmission, with a padded cushion on top for the operator to sit on. The single rear wheel, with a 7-50 x 16 tractor tire, was powered by a single-cylinder air-cooled mid-mounted Wisconsin engine that delivered 6.1 hp at the rated speed of 3,200rpm. Started by a rope pull, it had a 2-7/8-inch x 2-3/4-inch bore and stroke resulting in 17.8-cubic-inch displacement.

A single plate clutch with rotating ball wedge engagement, a variable speed V-belt drive and a sliding spur gear transmission with forward, neutral and reverse transmitted power from the engine to the rear wheel. The unit’s variable speed drive provided ground speeds of 2-1/4 to 4-1/2 mph forward and 1-3/4 to 3-1/2 mph in reverse at rated engine speed.

The unballasted tractor weighed 894 pounds, split between 420 pounds on the rear wheel and 474 pounds on the front axle. Adding 115 pounds calcium chloride to the rear tire, a 73-pound inner and an 83-pound outer rear wheel weight, a 200-pound operator and a full tank of gasoline brought the weight up to 855 pounds at the rear and 495 pounds in front for a total of 1,350 pounds. A 3-1/4-gallon fuel tank (located in front of the steering wheel) was claimed capable of providing a minimum of 4 hours’ operating time.

The Tri-Trac’s wheelbase was 68-3/4 inches with a crop clearance of 19-3/4 inches under the front axle. Tread width for the front axle (with two 4:00 x 12 tires) was adjustable in 2-inch increments from 48 to 72 inches. Turning radii were 8 feet at minimum tread width and 10 feet at maximum, which resulted in wide turns. The Tri-Trac was never tested at the Nebraska Tractor Test Lab, but four David Bradley two-wheel garden tractors and a Suburban lawn tractor were.

Implements for every need

Many implements were available for the Tri-Trac, including rear-mounted attachments such as a 9-inch one-bottom plow, a 4-foot sickle bar mower and a 7-foot dump rake. The mower was driven by the tractor’s PTO that consisted of a 4-inch diameter pulley located behind the bulge on the left side of the sheet metal enclosure. Idler pulleys were used to turn the belt drive 90 degrees at the rear of the tractor to drive the mower. Lowering the speed control lever not only increased travel speed, but also raised PTO pulley speed from 1,565 to 2,550rpm.

Mid-mounted implements included a 10-inch middle buster, a three-gang reel mower with a 57-1/2-inch swath, a two-row planter and a two-row cultivator for row widths of 24 to 42 inches. The planter came with 11 different seed discs for planting a variety of crops, and seven seed spacings could be obtained by changing drive sprockets.

A 40-inch-wide dozer blade (it could be angled 35 degrees and had extensions to increase the width to 52-1/2 inches) was available for the front of the tractor. Also available: a front mounted V-shaped snowplow that could be converted to a regular dozer blade, and rear tire chains to improve traction when moving snow. Towed implements consisted of a 4-foot-wide single disc harrow, a 6-foot-wide spike tooth harrow and a 3-foot-wide spring tooth harrow.

Since the Tri-Trac did not have a hydraulic system, implements that needed to be raised for any reason had to be lifted with a long lever and a strong arm, although some implements had counterbalance springs.

A draft-adjusting crank located just in front of the steering wheel was used to compensate for side-slip when operating on a hillside. Normally when operating on a side slope, the front wheels were turned uphill to hold the tractor in line. But with the Tri-Trac, that directed the drive wheel downhill, making the tractor very difficult to control.

Using the draft control crank caused the tractor frame to hinge up to 15 degrees in the middle so the rear wheel was not centered between the front wheels. This crank could also be used to adjust the furrow width of the plow and the cutting width of the sickle mower.

Evaluating a performance claim

Advertising claimed the Tri-Trac could handle farms up to 30 acres. At first, that seemed a rather optimistic sales claim, but further study revealed it might be possible, although it would require some patience. For example, the Amish are able to farm larger acreages using only horses, and part of the 30 acres would have been used for pasture and the farmstead. Plowing would have taken the most time, and a 9-inch furrow at the minimum ground speed of 2-1/4 mph would cover 0.205 acres per hour.

Assuming an 80 percent efficiency factor for turning at the ends, refueling, etc., reduced this to 0.164 acres per hour. Six 10-hour days would result in 9.84 acres plowed, which might have been close to the plowing required for a 30-acre farm. Another option would have been to hire the plowing done, which would also have been necessary for harvesting operations.

In 1962, Sears merged David Bradley Mfg. Co. with another Sears holding, Newark Ohio Co., retaining only the latter company’s name. Another merger occurred in 1964 when Newark Ohio Co. joined the George D. Roper Corp. and the plant in Newark, Ohio, continued to build outdoor power equipment. Thus, David Bradley became another well-known farm manufacturing name to disappear into history. FC

For more information: The David Bradley Collectors Club hosts an annual show in conjunction with Thee Olde Time Farm Show at Perry Farm Park in Bradley, Illinois. This year’s show is set for June 29-July 1, 2018. For information about the David Bradley gathering, call Ron Schubbe, (708) 258-6502. For information about Thee Olde Time Farm Show.

Jim Gay was raised on an Iowa farm and received a degree in agricultural engineering at Iowa State University. He is a lifelong collector of farm and construction equipment literature and information. Several years ago, Jim began sharing his information and experiences by writing magazine articles. Email him at jegsbg@mtco.com.

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