I can identify the double tree on page 5 of the January 2008 issue, as shown illustration at right. They are used on a 4-horse hitch and were factory built by John Deere, probably optional with equipment purchases at extra cost.
In the photo, the single tree dangling by the chain does not belong in that location and the chain is not even part of the hook-up. The dangling single tree, plus three others identical to it (but apparently missing), belongs on the upper side of the set-up. Each of the four single trees had a hole in the center (where the chain is hooked) that attached to one of the four clevises (hooks). In the upper portion of the photo, there should be one single tree for each clevis. (The fourth clevis is cut out of the photo.) In turn, each single tree was pulled by one horse. The harness tugs from each horse where connected to the single tree ferrels (hooks), one at each end of the single tree. The right harness tug hooked to the right ferrel of the single tree, left to the left ferrel. The set-up is now referred to as a double tree.
I grew up on a farm in northwest Missouri. We farmed with horses and mules until 1952. My dad had a John Deere 14-inch riding plow that had the same factory double trees, except ours were designed for a 3-horse hitch. My brother still has them. Dad used the 3-horse hitch on two pieces of equipment: the John Deere plow and a 7-foot Deering grain binder. His 4-horse hitch had wood double trees and was used to pull a 7-foot McCormick-Deering disc. As a kid I used to disc with two horses and two mules.
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