A few years ago, I wanted to have a 3pt finish mower to use with the rear PTO on my Massey MF1650. So here is a quick walk-through on it's build.
The deck is a 52" cut from under a Yardman riding mower. You can see the drive belt tensioner from gearbox to spindle belt.
I used a double pulley off a similar MTD deck to go on the left spindle for driving deck from the gearbox. The driven pulley on the spindle is quite a bit smaller than the drive pulley on the gearbox to bring the 2,000rpm of the rear PTO up to higher speed at the deck. Can't remember the OD of the driven pulley, but I needed as close to 3,000rpm as possible.
The 3pt frame is built from 1/4 steel strap. with a 1/4" plate welded in-between the rear angle support straps as seen below.
I used a 90 degree gearbox from a MF12 mower deck. The PTO shaft I built from scrap PTO shafts from farm equipment, with the quick attach PTO shaft universal being bought off ebay. The pics show better than I can explain in how I set it up. One thing you can't see, is the fitment of the universal joint to the gearbox. The Ujoint had an ID of 1" with gearbox being 3/4". I bought one of those "weld-a-sprocket" hubs at TSC that fits 3/4" shaft. I turned it down on the lathe on one side as close as I could to the key set-screw. Turned it down to have that part press snug into the universal, then welded in place. By turning on lathe with a press fit, it ensures perfect alignment.
The swivel casters came off a Yazoo mower deck, but had to block them up for proper height.
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