The John Deere Rotary Engine

The topic for this month consists of both literature and a “toy” of sorts. It also covers engines, which is a topic that I typically don’t address. More specifically, John Deere rotary engines. Believe it or not, there was a period of time during the 1980s when Deere was designing and building these rotary devices. The paragraphs which follow will describe more of this in detail.

Before we begin on the engines, I need to take you back in time to an earlier part of my life, namely college. My focus at UW-Madison was mechanical engineering, although I took some courses in agricultural engineering including tractors and engines and principles of farm machinery. I have always enjoyed learning about how things work and especially wanted to find a job designing agricultural machinery or tractors. Unfortunately, when I graduated in 1983, jobs were difficult at best to come by. I had an offer from the Department of the Navy to work at Headquarters, Marine Corps in Washington, DC as an engineer in the Logistics Department. In that capacity, we worked on anything and everything except aircraft. Our mission was to ensure that the equipment design, in conjunction with proper tools and training, assured that the troops in the field could properly maintain and repair the equipment to guarantee a solid state of readiness. It was a cool job and certainly taught me many things.

For just about any type of product, there is a trade show. For cars, trucks, farm equipment, computers and home appliances, there are trade shows. Military vehicles and equipment are no exception. During the fall of 1984, one such trade show was held in Washington, DC. A group of my peers from work and I went to the trade show to see what was new in the way of military “stuff.” Imagine my surprise and excitement when I saw that John Deere had a booth! Surprise quickly gave way to wonder as I considered what Deere might have to offer for the military. The company’s push was for a new type of engine called the SCORE rotary engine. At the time, Mazda offered a rotary (Wankel) engine in its RX-7 cars so this wasn’t a totally new concept for most of us. I picked up a brochure and a small plastic model of the engine and was on to the next booth.

Fast forward to today. Being the collector that I am, I keep many things that most people would have thrown away long ago. Yes, the brochure and the engine model are still in my possession after a number of years and moves. Photo 1 shows the front cover of the brochure. A large cut-away drawing of a SCORE rotary engine is featured and is surrounded by artist’s drawings of potential applications. The John Deere trademark is near the bottom along with “Government Product Operations.”

 The text explains that Deere and Company had acquired the rotary engine assets from Curtiss-Wright and hoped to improve the product and introduce it for military applications. The major advantages of the rotary over a standard diesel engine were cited as greater power density and the ability to burn a variety of different fuels including diesel, combat gasoline, jet fuel and alcohol. The name SCORE is also explained. As some of you may be aware, the government likes words that are referred to as acronyms—that is, names based off the first letters of the words that describe an item. SCORE stands for Stratified Charge Omnivorous Rotary Engine. I know that sounds like an extremely strange way to describe an engine, but if broken down, it does make sense. Stratified charge means that the fuel is introduced in layers rather than all at once. An initial charge of fuel is introduced by a pilot injector followed by a larger charge from the main injector. This produces a more even power stroke. Omnivorous literally means “eating all kinds of food.” Since this engine is designed to burn many types of fuel, the term omnivorous is quite appropriate. The words rotary and engine speak for themselves.

Rather than using reciprocating pistons, the rotary engine has one or more rotors, each with three curved faces. The rotor fits around a crank and turns at one-third of the crank speed. The result is a power stroke for each crank revolution. An air charge is drawn in on one side of the engine and is compressed as a rotor seal (tip) moves past the intake opening. The pilot injector provides an initial charge of fuel and it is ignited. The main injector adds the remaining fuel charge and the power stroke is completed. As the rotor continues to turn, another port is uncovered, allowing the exhaust to escape.

Construction and power generation products are a few of the items that Deere has manufactured for all branches of the military. Page 5 of the brochure shows a road grader, generator set, four-wheel drive loader and runway repair vehicle as examples of John Deere military products.

At the time the brochure was published, SCORE engines were planned but not yet produced. Page 8 (Photo 2) describes the two families of engines in the plan. First was the SCORE II family, which was to be introduced for production status by 1990 for military applications. These engines were of the two-rotor design with horsepower ranging from 375 to 2250. SCORE III engines were of the single rotor design for military and commercial applications, ranging from 80 to 320 horsepower.

The paragraphs of text on the back cover explain that Deere SCORE engines “will offer all branches of the military lighter, smaller, faster and more easily transported fighting vehicles, generator sets and power for air and sea craft.” The print date in the lower left corner indicates September of 1984.

The small plastic engine model is shown in another photo. It has a red plastic housing with gray rotor and white crank. A clear plastic knob on the back can be turned to spin the rotor and crank. The intake area is orange and the exhaust area is black, both of which are on the left side. Each has an arrow showing the gas direction. The injectors are printed in black on the right side. Also on the back is a silver decal with black lettering which states “SCORE ROTARY ENGINE FROM JOHN DEERE” and “LICENSED BY NSU/WANKEL.” A rotational direction arrow is also provided. As a point of interest, the shape of the decal is that of the engine rotor.

The American Society of Mechanical Engineers (ASME) produces a number of trade publications for its members. I am a member and in the February 1986 issue of ASME News, a picture of a Deere SCORE engine was included along with a short descriptive paragraph (Photo 3). It explained that Deere had recently displayed models and mock-ups of the engine at another recent trade show in Washington, DC. They had gone as high as 750 horsepower for military applications. The engine pictured was in development at the Wood Ridge, New Jersey laboratory.

When John Deere started in the rotary engine business, it established a wholly owned subsidiary called John Deere Technologies Inc. to manage the efforts. After seven years in the business, Deere and Company sold this segment to Rotary Technologies International Inc. of Lincoln, Nebraska in 1991. Photo 4 shows an article from the April 10, 1991 issue of the Chicago Tribune in which the sale of the rotary engine business by John Deere is described. Rotary Power International seems to be the current name of the business, located in Wood Ridge, New Jersey. However, an internet search indicates that they have only eight employees, down from the original 80 when Deere owned the business.

The brochure and engine model seem to be somewhat scarce in that I have only seen the model for sale at one show several years ago. I have not seen another copy of this brochure or any other that describes the SCORE rotary engines. Given that these items do not have any relationship with agriculture, they may not have much value to collectors. However, that’s difficult to tell.

Not all things produced by John Deere are green and yellow as we all know. In addition, not every business venture the company undertakes is necessarily a great one. I hope that this article has been interesting in that it points out one of those lesser-known ventures and shows yet another side of the company.