Hydrostatic Drive Operation.
The hydrostatic drive consists of a variable output pump driven by the truck PTO which in turn drives the distributor
bitumen pump with a hydrostatic motor. Thus, once the correct ratio between ground speed and pump flow rate is
established for a given transmission setting, the truck ground speed may be varied without affecting the application rate.
Dry Run Establishment of Correct Ratio
Between Pump Flow Rate and Ground Speed.
Determine from the computator the correct ground speed (fpm) and pump flow rate (gpm) for the desired
spray bar length (ft) and application rate (gal/sq yd) (table 2-1 ).
Place quadrant control lever in Circulate in Tank position.
Pull hydraulic control knob to uppermost position.
Lower ground speed tachometer drive wheel (5th wheel).
Engage truck PTO
Select truck transmission and if required, auxiliary and rear axle setting, to give adequate ground speed
and power for the desired application rate. More than one attempt may be necessary before the proper
gear setting is determined which will prevent jerky forward truck motion and still supply adequate power
and speed for the terrain.
Now, while driving the distributor forward at the speed (feet per minute) previously determined from table
2-1, push the hydraulic control knob down until the asphalt pump flow rate (gpm)
to the gallonage
The control knob should be held in this position by turning the fine control tube up until it is against the
bottom of the hydraulic control knob. Then lock the tube in place with the brass lock ring
Now that a dry run has been completed, you may wish to record the truck gear setting, spray bar length,
application rate and engine tachometer rpm, so the application rate can be duplicated in the future by
merely using the truck engine tachometer to establish the proper pump flow rate
Prior to placing quadrant control in Circulate in Bar position decrease pump flow rate, if necessary, to a
maximum of 160 gpm by raising the hydraulic control knob.
Lower spray bar to spraying position
Adjust spray bar length to previously determined length
Engage truck power takeoff
Place quadrant control in Circulate in Bar position ready to spray