Pump drivesPump drives:
PTO (Power Take Off):
The PTO is a driveline that attaches to the side of the transmission and takes a
portion of the transmission’s power. The driveline then extends to the gearbox that runs
the pump. PTO’s are unique in that they are simple in design, are used widely in various
applications, and they allow you to use the pump and drive all at the same time (pump-
and-roll). In the past the PTO has been used primarily for smaller pumps (300-500 gpm)
secondary to the main midship pump. Now with the advancement of technology the PTO
is being found driving larger primary pumps. Examples of this are new Type 3’s that Cal
Fire use and what 9984 uses.
Midship:
The midship is a gearbox situated midline splitting the driveline in half. When the
pump is not engaged the gearbox supplies all of the transmissions power to the rear drive
axels propelling the vehicle forward. When the pump is engaged the gearbox supplies all
of the transmissions power to the pump, this means when you are pumping you cannot
move the vehicle. Today the midship drive is the most widely used pump drive and can
power pumps in excess of 2000 gpm. Most apparatus that serve a dual role (structure and
vegetation fire suppression) will be outfitted with a smaller secondary pump for a means
to pump-and-roll.
Auxiliary:
Commonly referred to as “aux pumps” these drives have a small separate motor
that drives the pump. These motors take fuel and electricity from the vehicles main motor
to run and have separate controls (usually 2 sets 1 in the cab and 1 on the pump panel)
and are connected to the pump via a driveline. The downfall to the aux pump is that it
takes up a lot of valuable space on the apparatus. Today these type of drives are being
replaced by the PTO drive
Hydrostatic:
The hydrostatic drive is a very complicated drive. This drive was specifically
made for Cal Fire and is only found in California; because of this, there is very limited
information on this pump drive. The heart of the unit is a hydraulic pump mounted in
front of the motor that takes power from the flywheel. This hydraulic pump is constantly
running while the motor is running but is only moving fluid when engaged. When the
hydraulic pump is engaged via a slide handle found in the cab and on the pump panel
the hydraulic pump starts to move fluid. The more the handle is slid over the more fluid is
moved. The fluid is moved through 2 high-pressure hydraulic hoses (1 for supply 1 for
return) to a gearbox. This gearbox turns the hydraulic energy in to mechanical energy this
then turns the pump. This whole process can be thought of as the power units that run our
extrication tools, only on a larger scale. Hydrostatic drives are very vulnerable to damage
because if any of the high pressure hydraulic lines gets a hole in it the entire system is out
of service. In addition to this vulnerability the high pressure hydraulic lines are ran on the
bottom of the chassis exposing it to the elements. Today the hydrostatic drive is being
phased out by the PTO drive.