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ASSEMBLY
PA91 03/09 Assembly Section 3-2
© 2009 Alamo Group Inc.
ASSEMBLY
TRACTOR SELECTION
Horsepower and Weight Requirements
The Power Arm 91 requires a tractor with a minimum of 30 HP in conjunction with a minimum weight of
1500Kg (1.5 tons imp. 1.6 tons U.S.). If necessary, add ballast to achieve this weight. Check in the tractor’s
handbook that it does not exceed the maximum allowed.
Bear in mind that these are minimum requirements for optimum working conditions. Tractor selection must take
into account the type of terrain upon which it is proposed to operate and the degree of stability required.
Linkage Requirements
The tractor must be equipped with either CAT I or CAT II linkage.
Linkage Isolation
Although it may be possible to operate the semi-independent version of the PA91 without linkage isolation, a
severe strain would be put upon the attachment yoke and pins. Most modern tractors are equipped with a
ready means of providing linkage isolation through a conveniently operated valve.
Linkage isolation is not required on the fully independent model of the PA91 and the tractors hydraulic controls
should be neutralized.
Check Chains/ Stabilizers
To hold the machine firmly in position, check chains or stabilizer bars must be fitted. It is dangerous to operate
the machine without these elements.
Tractor Relief Valve
The main relief valve in the hedger hydraulic control unit is set at 1800 PSI (125 Bar). Therefore, if operating
the PA91 in semi-independent form, the tractor’s relief valve setting must be at least a little above 1800 PSI for
satisfactory operation.
Tractor Hydraulic Flow Rates
Oil flow rates are not crucial when operating a semi-independent PA91. Flow rates of up to 10 GPM (45 1/min.)
should not have any adverse to the inching response that it is sometimes required from the control valve.
P.T.O. Shaft
Tractor must be equipped with live drive-independent PTO shaft to enable forward movement to be halted
while the flail head continues to operate.
Draft Control
Loads imposed through the draft sensing mechanism will not normally be sufficient to put a strain on the
tractor. However, any provision for draft control should be set to minimum response. Where a draft control
rocker is fitted with a dead pin this should be utilized.