Why did Ferguson use the 1 1/8″ PTO shaft, and the later 1 3/8″ shaft?
At the time the 9N was being designed most tractors had 1 1/8″ PTO shafts, though the switch had begun to 1 3/8″ which was the new ASAE (American Society of Agricultural Engineers) Standard Size. The ASAE also developed standards for drawbar height, and the position of the PTO shaft in relation to the drawbar.
The first PTO on a Ferguson tractor was on the Ferguson Brown, and it was located to the right and just below the lift arm rockshaft. Ferguson designed the triangle configuration whereby the PTO shaft was located between the lower links, and in relation to the top link bracket and lower link spacing. The top link and lower link dimensions then became what is now known as Category 1 Three Point Hitch. I believe Ferguson also had a patent on this design. Later Ferguson created the dimensions for what later became known as Category 2 Three Point Hitch. I believe the Category 2 design was developed during the design of the LTX or possibly the Large Ford Ferguson which preceded it.
At the time the ASAE standard was developed most farm equipment was pull type, and the position of the PTO shaft and drawbar heights on tractors varied considerably. Some brands like Oliver had PTO shafts that were higher than competitors. Some brands had PTO shafts not centered above the drawbar as was the case with some Farmall tractors like the A, B and C.
When the TE-20 was designed the dimensions were the same as the 9N/2N. The TO-20 and TO-30 maintained these same dimensions, and the use of a 1 1/8″ PTO shaft. Ferguson advertised that Ferguson implements would all fit his new tractors, TE-20, TE-A20, TO-20 and TO-30.
For pull type implements requiring ASAE standard PTO and drawbar dimensions, standard drawbar and PTO adapter kits were offered. Ferguson pull-type implements like the Wood Brothers combine and corn picker, were available with either 1 1/8″ or 1 3/8″ PTO connections or universal joints. When the Belle City corn picker came out, it too was available with either 1 1/8″ or 1 3/8″ PTO connections. This was done so these implements could be operated on tractors with either size PTO shaft.
Mounted Ferguson implements were originally available with only 1 1/8″ PTO connections because the only tractors with three point hitch were Fergusons. After the split from Ford, Ferguson and Ford implements generally fit both brands of tractors. When the TO-35 came out it had a 1 3/8″ PTO shaft. All Ferguson implements then became available with either 1 1/8″ or 1 3/8″ PTO connections. 1 3/8″ yokes were then offered to replace the 1 1/8″ yokes on earlier mounted Ferguson implements.
Again, Ferguson advertising continued to proclaim Ferguson implements would still fit the newer model Ferguson tractors. As patents expired and all manufacturers began to offer tractors with three point hitch, Ferguson implements as old as those made by David Brown for the Ferguson Brown Type A would fit any tractor with category 1 three point hitch.
Ferguson began selling tractors with a 1 3/8″ PTO (TO-35) before they were offered by Ford. Ford tractors were about the only make that you could attach Ferguson mounted implements to, though John Deere, Oliver and Case developed tractors with three point hitch that Ferguson implements could be mounted on. Ford tractors were one of the few brands that Ferguson provided mounting brackets to mount the side-mounted baler and forage harvester.
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