One of the challenges in researching the Froelich tractor is that there is a scarcity of primary sources (especially graphical ones) and a proliferation of information that seems to be based on some of the much later replicas. Below, I try to sort out some of the differences between the most important examples of the Froelich design.
I’ve chosen five exemplars of the Froelich design based on how I perceive their significance in propagating information about the original. A group of examples can be ignored fairly easily: most running “replicas” are not replicas in the strong museum sense (that is they are accurate to the point of serving as resources) but more like “mock-ups.” If it features a roller chain or doesn’t have multiple exposed gears, it’s not especially accurate.
In the group above, there are three pictures labeled “Froelich” which almost certainly show the original tractor. The pictures labeled “Waterloo” probably show a Waterloo Gasoline Traction Engine. The group labeled “Ertl” show a 1/16th scale model which could be based on either the “Waterloo” or the replica shown in the group labeled “Movie,” used in John Deere’s 1939 film Making Tractor History and on display at the John Deere Tractor and Engine Museum. “Replica” shows a 1/2 scale production that resides at the Froelich Tractor Museum.
There aren’t many details in the “Froelich” pictures, but in Froelich 3, there are several distinctive items. The pump handle for the fuel tank is unique. None of the other pictures or models show a handle quite like it. One important detail is the piece behind the pump handle—it looks like the back from a canvas chair but with all the apparatus in front of it I think it is something else. Looking at advertisements for Van Duzen engines (here) and this restoration of a Van Duzen engine (here), it’s probably that the crankshaft was exposed and this canvas was supposed to shield it from dust and chaff. (It was a Van Duzen engine that powered the Froelich tractor) If so, this is a hint that the “Ertl” design is incorrect in totally enclosing the engine. Both “Froelich 1” and “Froelich 2” seem to confirm that the engine is not enclosed or does not but up against the fuel tank. In these two pictures you can see a triangle of light behind the engine flywheel. The “Froelich” pictures are also the only ones to include a box over the valve and timing assembly on the right side of the engine cylinder. Curiously the fuel tank is covered or extremely tall in “Froelich 1” and “Froelich 2.”
The “Waterloo” pictures show an advertisement, the picture the advertisement is literally drawn from (you can see the artist’s manipulation already), and a rear 3/4 view. The “Waterloo” is distinguished from the “Froelich” by the engine belt: in “Waterloo 3” you can clearly see the driven pulley is quite large (which is confirmed by the design of the “Ertl”) while in “Froelich 1” and “Froelich 2” you can see the driving pulley is the large one. Another possible distinguishing feature is the pump handle: it may be different than the one seen in Froelich 3. You can see a lubricator between the rear of the fuel tank and the belt pulley—it’s the spool-shaped object in the triangular light patch. Examples of these can be seen in the Van Duzen restoration thread linked above. It’s more evidence that the engine housing is not solid like what is seen on some of the other examples. Between the differences from the “Froelich” pictures and the inclusion in Waterloo advertising, I’m convinced this example is a Waterloo Gasoline Traction Engine.
With its similarities (pump handle, large driven pulley), I suspect the “Ertl” design is based on the “Waterloo” Gasoline Traction Engine, not the original “Froelich.” However, I have to emphasize the phrase based on. “Waterloo 3” makes it clear that the metal bracing next to the water tank should connect to a pile of wooden planks rather than end abruptly. In the same area, the “Ertl” design lacks the stacked wooden planks that should hold the axles used in the transmission. In “Waterloo 2,” you can see the stacked planks and an axle hole behind the flywheel. The gears visible in both “Waterloo 2” and “Waterloo 3” also lead me to believe that the transmission of the “Waterloo” (and probably the “Froelich”) is primarily located between the two large side beams and not on the side. The “Ertl” design is also incapable of two forward gears or the reversing gear the Froelich tractor is partly remembered for. Finally, the water tank on the “Ertl” is considerably shorter than seen in “Waterloo 3.”
The “Movie” design was supposedly built to original plans for the “Froelich,” although considering that Froelich built his tractor without plans, it’s more likely it was built to plans for the “Waterloo” since that one was “mass-produced.” Thus, it has a pump handle similar to the “Waterloo” and “Ertl.” The “Movie” design was made from John Deere D parts and could be driven, so its engine is from the D but fit to the replica chasis. The elevated “reserve” fuel tank is larger than the “Froelich,” “Waterloo,” and “Ertl” designs, the actuating mechanism along the right-hand side is different, the driving pulleys are shielded, and the transmission is borrowed but not clearly functional. The wheels on the “Movie” design use a unique square-braced rim with a gear engaging sprockets in the wheel situated above the main beams rather than below. However, changes were made sometime between 1939 and when “Movie 4” was taken: the wheels lose their teeth and the front beam receives a large metal cap rather than the single strip visible in “Movie 2.”
“Replica” also seems to have been built to run, although the museum uses a different “mock-up” for actual use. Accordingly, its engine structure is very different than the others. It also has a transmission located between its main beams, lending credence to the idea that the “Froelich” transmission was of this “internal” type. The water tank (green) is supported oddly, and uses an open channel to return water from the engine’s cooling jacket. There are mentions of this method of releasing heat from the used cooling water in a few sources but I don’t know which came first: these references or the “Replica.” The water tank is also supported in an unusual fashion compared to the “Waterloo,” “Ertl,” and “Movie” designs. The “Replica” design could be an outlier or it could be true to the “Froelich” design, as I have no clear sources for what the rear of that one looks like. However, there is no mark corresponding to the large channel on the source images for the “Froelich.” The timing gear on the engine shows some differences, which were probably necessary for a working engine (compare “Replica 5,” “Waterloo 2,” and the Van Duzen restoration thread). “Replica 1” also makes it quite clear there’s no pump handle on the gasoline tank, the right hand lever is some sort of pedal, and there is an additional lever between the main beams (perhaps a shifter).
In all, none of the later sources are entirely true to what the “Froelich” would have looked like. The most accurate is the “Movie” design, but The transmission is incorrect: it would not be able to shift, and should have a set of spur gears on the outside of the beams and a lower final drive axle.