Differences Between a 501 & a 515 Ford Sickle Mower

Pitman Arm

• The Ford 501 is equipped with a wooden Pittman arm, which acts as a connecting rod that converts the rotary motion of the mower’s pulley into the back-and-forth motion that drives the cutting bar. The sickle bar on the 501 can cut only when it is in a horizontal position. It cannot cut at an angle, such as 10 degrees above or below horizontal. Therefore, the unit cannot be used on ditches or hillsides. Because the arm is made of wood, it will degrade if the mower is stored outdoors. You can prevent this by storing the unit inside, or removing the arm from the mower and storing it inside.

Wobble Box

• The Ford 515 uses a wobble shaft drive instead of a Pitman arm. It is made of steel, making it durable and longer lasting than the Pitman arm. The wobbling action of the box allows the sickle to cut grass horizontally or at various angles above or below horizontal. Adjust the bar up to move over rocky terrain, or down to cut crops that have been beaten down by heavy wind.

Damage Prevention

• Rocks and stumps can hide in tall grasses, causing damage to your mower. To prevent this, the 501 is equipped with a safety that releases the sickle bar, so it swings backward when you hit a large object. If the cutting knives become jammed, the wooden Pitman arm breaks to prevent damage to the sickle. It’s much cheaper to replace the arm than to repair the cutting bar. The 515 has a spring-operated breakback that swings back to prevent damage to the cutting bar and simultaneously lifts the bar. The breakback is reset by backing up the tractor.

PTO

• The power take off (PTO) is what sends power from the running tractor engine to make the sickle bar cut. The 515 mower is rated to be operated at higher PTO speeds than the 501. For instance, when a 9-inch drive sheath is installed on the 515, the recommended PTO speed is 740. The same size sheath on the 501 has a recommended PTO speed of 670. Both PTO ratings recommend a 4-speed transmission tractor to be run in third gear.