Bulldozer Is Hauled to Fire On Truck With Tilt-Bed Body
Many county fire protection districts, as well as a few city departments, have extensive areas of grass and brush that require the use of bulldozers when fire lines must be constructed.
However, not only are large dozers too expensive for most of these districts, but moving the large units over narrow roads or streets presents problems. What is needed is a smaller, easily moved and less expensive, yet adequate, bulldozer unit. But a unit meeting all these requirements is difficult to fabricate.
We had the same problem on the 1,250,000-acre Yakima Indian Reservation in Washington State, where 250,000 acres are fairly well populated and covered with fast-burning grass and brush. Although we had a number of large bulldozers, a smaller, fast initial response unit capable of quickly reaching fires in these populated areas was needed. Thus, it was decided several years ago to develop a unit using the tilt-bed truck body developed by the California Department of Resources, Division of Forestry.
Engine and transmission
The truck used was rated at 35,000 GVW with its frame modified to the exact dimensions of CA 110-inch and CEF 147’/2-inch. The tandem-drive rear axles are straight-line drive to provide clearance for a cylinder on each side of the propeller shaft. The transmission is five-speed with an auxiliary threespeed. The truck’s 406-cubic-inch gasoline engine and the many available gear ratios enable the truck to transport a D-4 class bulldozer up various grades at satisfactory speeds and maintain 50 to 55 mph on highways.
Because the truck operates over both heavily traveled highways and back mountain roads, where handling ease and safety are essential, it has power steering and air-over-hydraulic brakes. We consider it essential that all of our fire vehicles have power steering.
The tilt-bed body, which has a capacity of 19,000 pounds, hinges just ahead of the rear set of drivers. Two systems, one hydraulic and one air, control operation of the bed. The air system is used only to raise or lower the bed empty and is controlled by a three-way valve in the cab. The hydraulic system is merely a hydraulic cushioning cylinder which determines the speed at which the bed will tilt or lower with the tractor. The hydraulic cylinder is controlled by a globe valve requiring only an initial adjustment. The bed is locked in the running position by an automatic safety lock.
To unload the tractor, the safety lock is released and then the tractor is backed until its weight tilts the bed so that it can be backed the rest of the way down the ramp. The bed will stay in the raised position until the tractor is reloaded. If desired, the bed can be lowered with the air control. Chock blocks set in stake pockets at the front of the tread runway prevent the dozer blade from striking the back of the truck. These also enable positioning of the tractor so that its weight is propperly distributed.
Response to 400 alarms
The bulldozer first tried with the unit was equipped with a hydraulically operated fireline plow as well as a dozer blade. However, the plow was soon removed as it proved unsatisfactory on the tractor for several reasons.
Since going into service the unit has responded to well over 400 alarms. No modifications were found to be necessary. Because of its maneuverability, speed, and quick loading and unloading capability, the unit normally arrives on the fire scene as quickly as pumper units. It is felt that with a heavier truck, this type of bed would also be suitable for transporting tractors of the D-6 class.
Such a unit as this would be very practical for agencies having similar areas to protect. With a relatively low initial investment, it would fill a void now found in the equipment inventory of many fire protection agencies.