In Reply to: Ford 501 sickle mower /breaking pittmn arms posted by Bill Redmer on July 06, 2015 at 14:38:57:
What are you mowing (grass variety)? I have some grass in the fields I mow called Ventenata or wind grass by some local farmers. Terrible stuff when it's heavy. It makes the mower hammer and lugs the tractor down. Under worst case scenarios, this has broken the pitman and/or sickle drive heads on my mower.
The pitman drive should hang low allowing the pitman arm to run nearly level with the sickle. I have welded heavier arms onto pitman drives that are stronger. I also drill 3 holes in the pitman through the wood in 90 degrees to and between the original bolts that hold the pitman wood to the pitman drive. This keeps the pitman wood from splitting as you described. They will however change the balance and create more vibration if I run the mower too fast. That being said, don't run your tractor at a higher RPM than you need to keep the mower cutting
Are you cutter knives sharp and the rock guards/ledger plates in good shape? I have found that at times I need to remove the sickle and wash it and the bar/guards a couple times a day to keep it moving freely.
I mowed about 45 acres with my 8N and 501 mower this spring without breaking anything. Didn't have to sharpen my knives or wash the sickle and bar at all.
Also when you turn, the mower will do a better job of mowing if you raise the mower and back up to get in line with your corner rather that try to turn sharp with the mower cutting. Figure 8 turns work great if you have the room. Just raise the mower each turn. Try not to drag the cutter bar through a lot of grass that you have cut. Tends to plug and drag.