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OPERATION
OPERATION
Operation Section 4-7
© 2004 Alamo Group Inc.
SR14/SR20 10/03
2.4 Drawbar
The tractor drawbar must be positioned at a certain
length based on the operating speed of the mower for
proper driveline operation. 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.
Ensure that the drawbar is rated to carry the tongue
weight of the mower.
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 SR14 and SR20 mower requires a tractor with a minimum of 75 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.
2.3 Tractor Horsepower
Tractor Drawbar Length
(Based on Mower Operating Speed)
16" (1000 RPM 1-3/8”-21)
20” (1000 RPM 1-3/4”-20)
TONGUE
DRAWBAR
14" (540 RPM 1-3/8”-6)
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.
Pintle Hook Hitch-Optional Equipment
Drawbar length must be modified to obtain dimension
"A" (CV Driveline = 17" ± 2", Standard Driveline = 19 ±
2").
Pintle
Hook
Drawbar
Pintle Hook
Mount
PTO
Shaft
Tongue
Cont. Rod
Pintle
Clevis
Tongue
A