Jerry's fully functional 1/8 scale John Deere tractor.

Jerry’s completed 1/8 scale 1936 John Deere tractor ready for paint. It starts up with a twist of the flywheel.

Building a Fully Functional 1/8 Scale 1936 John Deere “D” Tractor

From the start, Jerry’s original goal was to build a model to absolute scale in every respect—and to still have a functional four-stroke, spark plug ignition engine that would run on gasoline like the original. The idea was to have the tractor run at under 1,000 rpm, and start by rotating the flywheel in the same manner as the full-size version. Starting by hand and running under 1,000 rpm is generally not a problem if you can enlarge the flywheel until you achieve your goal. However, in this case the size of the scale flywheel had to be maintained.

A flywheel at the diameter needed to maintain the desired performance would have been hopelessly oversized, and would look ridiculous. The problem was solved by reducing the compression ratio to just under 4:1 (normally it would be 6 or 7:1) so a scale flywheel could be used. Several other things were also done to reduce friction, as well as making improvements in the air/fuel mixture. Ultimately, Jerry succeeded in getting the tractor to start by rotating the flywheel by hand, as on the original.

The rear end of Jerry's unfinished John Deere tractor.

Jerry submitted photos of his 1/8 scale tractor during several stages of the construction process. These images show some of the progression on the functional miniature John Deere. Sitting on top of the tractor is the scale grease gun, which also works.

The 1/8 scale tractor with flywheel lying beneath.

Everything on the model was made to 1/8 scale, down to the working grease fittings—each with a spring-loaded ball inside. In this photo, the carburetor and grease gun are sitting on the engine. The flywheel sits to the right.

Jerry submitted this video of the tractor running—operating between 600 and 800 rpm. It will rev up to 2,000 rpm, although this would not be desirable, as that’s well above the speed of the original full-size tractor. Jerry hoped that once the engine was broken in, it would idle down to 500 rpm or slower.

In the video, Jerry starts the motor and runs the tractor in both forward and reverse. He then throttles it down to idle speed. Note that all of the electrical components are fully contained within the tractor itself. No external connections are needed to fire up the engine. 

The next process was to completely disassemble the tractor and paint each individual part. Scale decals were made and applied, and then the tractor was reassembled. Jerry has taken other video of the tractor running, and demonstrated it at shows from 2005–2006.

Now that the tractor is painted, it probably won’t be run very often. That’s because, like the real tractor, this is an oily, messy process that can be hard to clean up. So enjoy the video, or see it in person if you get the chance.

The scale air cleaner, exhaust pipe, and engine breather.

The air cleaner (left) has 496 holes drilled at .012” in the same pattern as the original. The exhaust pipe sits in the center. On the right is the engine breather.

Jerry's 1/8 scale John Deere tractor radiator.

The scale brass radiator for Jerry’s tractor is fully functional. It has 20 tubes and 72 fins just like the original. The small radiator has 33 square-headed bolts and nuts (.038” diameter, 120 tpi) to keep it together. In total, there are 167 separate pieces in the radiator, with 146 solder joints. The logo was scribed and cut freehand with a .022” end mill on a Sherline mill.

Jerry also intends to make a scale tool kit if it can be determined what originally came with the tractor. A scale owners manual, and possibly a scale shop manual will also be made if possible. The final painted version of the tractor was featured as a centerfold in the Nov/Dec 2007 issue (#14) of Model Engine Builder magazine.

The building that housed the original John Deere dealership still exists. In 1936, they sold the prototype from which this model was built. One of the original tractors was purchased by Jerry’s grandfather, and had remained in the family. Jerry fully restored the tractor while taking dimensions of each part to build his replica.

Jerry's 1/8 scale John Deere tractor sits on the fender of the full-size original.

Jerry stands next to his grandfather’s original 1936 John Deere “D” tractor, which he fully restored. His 1/8 scale model sits on the fender. In this photo, it’s easy to tell the two machines apart; however, when looking at close-ups of the model, its harder to differentiate.

Jerry is thinking about eventually building a replica of the original dealership showroom as a display for the model. Although, he noted that making small greasy manuals for the shelves may be a challenge. Jerry recalled visiting that dealership as a kid, and coming home happy, but “dirty as a pig” after visits with his grandfather.

In September, 2009 Toy Farmer Magazine wrote an article on scratch-built farm toys, which featured Jerry’s tractor. Below you can view more photos of Jerry’s fully functional 1/8 scale John Deere tractor. Click on images to enlarge. 

1/8 Scale John Deere Tractor Construction

Finished 1/8 Scale John Deere Tractor

This section is sponsored by:

Sherline Products

Makers of precision miniature machine tools and accessories. Sherline tools are made in the USA.

www.sherline.com

Sherline is proud to confirm that Jerry Kieffer uses Sherline tools in the production of his small projects.

Artisan added: November 30, -0001 - Last modified: February 15, 2022

Presented by The Joe Martin Foundation for Exceptional Craftsmanship