Ch. 18 Stabilizing the Apparatus Flashcards
Stabilizing Principles
- Apparatus has a center of gravity located somewhere along the longitudinal midline of the chassis, between the front and rear axle
- Extending straight over front will cause center of gravity to shift forward
- Aerial on lateral grade center of gravity shifts to lower side
- Place stabilizers in position to minimize stress on the suspension
- IFSTA recommends stabilizers and stabilizer pads be fully deployed every time the aerial device is raised from bed
- Gravity circle- Theoretical safety zone that surrounds the center of gravity
-Excessive loading will expand gravity circle and effect stability of apparatus - Short jacking- Setting stabilizers shorter on one side than other
-limit switches (rotational interlocks) prevent mvmt of aerial device to short-jacked side - Stabilizers- (outrigger) device that prevents apparatus from tipping
- Post-type stabilizer- (downriggers) straight jacks extend down from chassis
- Box stabilizers- (H stabilizers) extend straight away from truck and have jacks that extend straight down to the ground (Most common)
- A-frame, scissor, or X-style stabilizer- (fulcrum) extend down and away from chassis
Aerial: Transferring Power to the Hydraulic System
- Power Take-Off System- Rotating shaft that transfers power from engine to auxiliary equipment
- PTO provides power to hydraulic pump
-creates pressure on fluid in hydraulic line
-switch on dashboard between driver and passenger/officer seat or above driver seat
-activation may be pneumatic, electric, hydraulic, or combination - Pneumatic requires 50 to 140 psi air pressure for PTO to operate
- Engine Brakes or retarders may need to be shut off to engage PTO
- Hot shift PTO system- Can be engaged when transmission is in neutral
-on most newer trucks
Steps to Operate PTO
Goal is to ensure one setup without having to reposition
Steps:
- Engage:
-Set park brake
-Place transmission appropriate drive gear
-Activate PTO
-Place transmission in neutral
- Disengage:
-Return engine to idle
-Deactivated PTO
-Neutral
Setting Stabilizers:
Conducting Preliminary Checks
- Activate front brake lock to minimize longitudinal movement
- PTO engagement light is lit before leaving the cab
- Chock wheels both in front and behind tire on both sides of truck
-Approximately 1-inch of extra space - As stabilizers deploy make sure they do not strike or land on other objects
- Spotter should assist with positioning the apparatus and avoid obstructions
- Stabilizer shoe- flat metal plate attached to the bottom of aerial stabilizer
Setting Stabilizers:
Operating the Selector Valve
-operated to provide hydraulic power to the stabilizing system
-Located either on rear step or midship on driver’s side of apparatus
-Make certain control is in stabilizing position (outrigger, jack leveling)
-Apparatus is ready for stabilization when selector valve is in proper position
Stabilizing on Even Terrain
- Allows for maximum stability
- Controls found on rear step of apparatus
- Box Stabilizer most common stabilizers
-two-part device:
1) Arm extends straight out
2) stabilization jack then extends down to the ground to raise the vehicle - Stabilizer pads should be centered beneath stabilizer shoe
- Pads are usually 24x24 inch with built in handle
- Level ground makes no difference which side is lowered first
- Activate in multi-step, side-to-side or front to back (never 1 jack at a time)
- Amount vehicle is to be raised depends on manufacturer’s design
- Fulcrum type can only be deployed in the fully extended position, or not-at-all if obstructed
Stabilizing on Uneven Terrain
Laterally or longitudinally
Two ways:
- Laterally (side to side)
-Correction of lateral unevenness is possible on grades up to 5%
-5% grade is 5 feet for every run of 100 feet
-uphill side of vehicle first until solid contact is made
-Lower downhill side stabilizers until truck is even
-Operate aerial over the uphill side of apparatus
- Longitudinally (end to end)
-If turntable is not level, the rungs won’t be parallel with the ground when positioned over the side
-Will cause lateral and torsional stress
-Apparatus should be positioned to minimize stress due to grade
-Operate over the front or rear of apparatus
-Articulating aerial devices should be operated off the rear
Stabilizing on Surfaces
-Objects should be solid and capable of holding weight of apparatus
-Ice reduces the ability to make solid contact
-Frozen ground can melt and leave unreliable surface for stabilizer
-Creates air gap between stabilizer pad and ground
-Avoid using salt since this may melt snow or ice
-sand or other friction enhancing products can be utilizied to assist in a secure stabilizer
Locking the Stabilizers and Transferring Power to the Aerial Device
- Interlocks prevent the flow of hydraulic fluid into or out of the stabilization system while the aerial device is in use
- Holding Valves prevent the movement of fluid WITHIN stabilizer
-activated when selector switch is moved to aerial position - Indicator light shows when interlocks are engaged
- Aerial apparatus with box-type stabilizers commonly have a series of holes drilled through the bottom post of elevating jack
-designed for insertion of large steel pins that act as additional safeguard against inadvertent dropping of jacks
-Insert in hole immediately below jack
Retracting the Stabilizer
-Process is reversed in order to prepare the apparatus for departure (avoids stress)
-Remove safety pins
-Make sure all personnel and equipment is clear
-Raise stabilizers the reverse order from which they were deployed
-Move wheel chocks slightly away from tires
Using Manual Stabilizers
-Older midship and tractor-drawn aerials most likely have manual stabilizers
-Extension arm that has a screw jack attached to end of arm
-Operator must swing extension arm into position manually and turn screw jack
-Midship aerials extension arm is stored perpendicular to ground
-Tractor-drawn extension arm is stored in a recessed position beneath the goose neck portion of trailer
Stabilizing Tractor-Drawn Aerial Apparatus
-Maximum stability achieved when angle of tractor is 60 degrees from centerline of trailer, and the aerial is operated toward outside angle
-Parking at angle increases stability beyond what stabilizers can provide
-Angles less than 60 degrees provide less stability as do angles 61 to 90 degrees
-Angle greater than 90 degrees are poor stability and produce damage to truck
-Alarm sounds if attempt to make angle greater than 90 degrees
- best way to achieve position:
-line turntable with objective
-turn tractor away from building
-turn tiller toward building
