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.
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.
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 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.
Finished 1/8 Scale John Deere Tractor
This section is sponsored by:
Makers of precision miniature machine tools and accessories. Sherline tools are made in the USA.
Sherline is proud to confirm that Jerry Kieffer uses Sherline tools in the production of his small projects.