The details of the transmission on the Froelich tractor are a little hazy. In John Deere: A History of the Tractor by Randy Leffingwell, he references a “sliding gear transmission” (p70). The accompanying picture is of the Froelich museum replica, which has some accuracy issues, so it is difficult to assess the accuracy of the claim.
The 1939 movie replica, now housed at the John Deere Tractor & Engine Museum, was built using parts from a John Deere D tractor. The resulting transmission clearly shows its heritage, and the fact that it is an improvised solution. Despite the multiple gears, it clearly can’t shift
The care shown in arranging the, apparently, faux shifter has me convinced there is some truth to it. Since the transmission appears incapable of shifting, I am convinced the accuracy is actually for the shifter, not the transmission. This correlates well with the use of a brake band dwarfed by a larger flywheel on a 1917 patent by John Froelich for a “Reversing Clutch and Gear.” However the all-internal gears are difficult to reconcile, accurately, with the mix of internal and external gears shown on the Waterloo and Ertl designs.
A final source worth mentioning is The John Deere Legacy by Broehl. Page 42 contains the following:
I believe that he used or copied the Rumely steam engine transmission because Rumely was the only steam engine manufacturer to use a reverse gear; everyone else reversed the engine to back up.
Just how the power was delivered to the rear wheels is not clear; however, a friction drive like that commonly used to drive thresher cylinders was utilized. This consisted of a compressed friction wheel on the powershaft of the engine that engaged a plain iron pulley on a driven shaft. The tractor mechanism differed from the thresher mechanism in that a spring held the mechanism out of engagement, and to start the machine as a tractor, the operator at the steering wheel rode with one foot on the end of a long lever that forced the friction wheels together.
Broehl should not be considered a reliable source when it comes to the Froelich tractor, however. It is the only source I have found to claim that the main beams were laminated to “bend together at the front over the front axle, while at the rear they were spread out practically…parallel to each other” (42). None of the replicas nor period sources seem to show the main beams bending. In addition, the Rumely steam traction engines of the time did not use a reversing gear train—they used the “Marsh” valve gear as documented in my other post, this forum, seen in this video, and subject to this patent (and this one).
The Waterloo Gasoline Traction Engine Company (incorporated to produce the Froelich design) advertised two forward gears and one reverse. It’s unclear if the original had three gears or just one forward and one reverse.
Submitted in 1914 and approved in 1917, John Froelich received a patent for a combined Reversing Clutch and Gear. This is over a decade after he left the Froelich company but it operates with a band brake, single control, and provided both a forward gear, reverse, and neutral/brake. That makes it a good candidate for inclusion in the Froelich’s transmission since there’s no clear braking capability on the wheels, only a single lever for controlling the transmission, and the advertised capability to travel both forward and reverse.
The basic operation of Froelich’s reversing clutch and gear was rather complex. It comprised an input shaft tied to a large flywheel. As the shaft and flywheel turned, they were tied to a bevel gear such that it had no motion relative to the shaft and flywheel. In turn the bevel gear meshed with a set of 4 pinion gears that could both rotate on their own axis or rotate around the input shaft. These 4 pinion gears meshed with another bevel gear tied to a hollow shaft that encircled the input shaft, such that the encircling shaft could turn independently of the input shaft. The encircling shaft was tied to the output gear such that the output and second bevel gear always rotated together.
Neutral: If the output gear was held in place, like by the inertia of the wheels, the 4 pinion gears would revolve around the input shaft instead.
Forward: The pinion gear were attached to a hub that nested inside the flywheel, which could be held in place by a band brake. Thus activating the brake band would force the pinion gears to stay in place, and instead revolve around their individual axles, so the input bevel would rotate, the individual pinions would rotate the opposite direction, and the output bevel would rotate in the original direction of the input.
Reverse: A shipper surrounding the encircling axle and the input shaft could be used to compress a series of clutch plates inside the flywheel and hub. This would thus link the flywheel and the hub so that the pinion gears were tied to the input bevel. The revolution of the input bevel was linked to the pinion gears at that point, so they acted as a single gear turning the output bevel in the opposite direction to the input bevel.
It’s understandable why Froelich’s design didn’t proliferate. While clever, it has lots of small parts that probably weren’t particularly durable. Manufacturing it would represent a challenge since it needed those small parts threaded together carefully.
Despite its much later patent date, the inclusion of a band brake and presumably nonfunctioning shifter on the movie replica incline me to believe that Froelich’s reversing clutch and gear were used in his tractor (or an early version at least). It could be extended to have two forward gears by increasing the length the shipper could move, which may explain why some views and replicas show a large number of gears in the drive train. Its single control lever and ability to enter neutral/brake all match the Froelich tractor’s lack of visible brakes and other controls.