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OPERATION
FN180/FN120 01/11 Operation Section 4-5
© 2011 Alamo Group Inc.
OPERATION
2.3 Tractor Horsepower
The horsepower required to operate the mower depends on several operating factors including the vegetation
to be cut, terrain condition, operator experience, condition of the mower and tractor, and others. For most
mowing conditions, the FN180/120 NITRO mower requires a tractor with a minimum of 70 HP. Operating the
mower with a tractor that does not have adequate power may damage the tractor engine. Exceeding 100 HP
for a 540 RPM drive and 140 HP for a 1000 RPM drive may cause mower damage by overpowering the unit in
heavy cutting conditions.
2.4 Drawbar
Constant Velocity and Standard Driveline.
Position the length of the drawbar from the end of the
tractor PTO shaft to the drawbar hitch hole according
to the operating speed of the mower. If the mower is
a 540 RPM unit, position the drawbar length from
shaft end to hitch hole at 14”. For 1000 RPM
mowers, set the drawbar length at 16” for 21 spline
1-3/8” mowers and at 20” for 1-3/4” 20 spline
mowers.
Pintle Hook Hitch-Optional Equipment
Drawbar length must be modified to obtain
dimension "A" (CV Driveline = 17" ± 2", Standard
Driveline = 19” ± 2").
2.5 Tractor Hydraulics
The mower center section and each wing are positioned with hydraulic cylinders that are operated by the
tractor hydraulic pump. The tractor must have a minimum of 2 hydraulic control valves devoted to the mower
unless the tractor is fitted with a 3-spool control valve (extra equipment).
A 3-spool control valve is required if the tractor is equipped with a single valve and is recommended for those
with two valves so that the center section and each wing can be controlled independent of one another. Refer
to the Assembly Section of this manual for properly equipping the tractor with a 3-spool control valve. Tractors
equipped with three hydraulic ports can position the center section and each wing independently with no extra
equipment. If the tractor is equipped with only two hydraulic ports and a 3-spool control valve is not used, the
wings cannot be operated independently and will raise and lower at different speeds.