FIRE APPARATUS MAINTENANCE
THERE ARE many points on an apparatus which require inspection and lubrication and which are often overlooked. Such points include linkage on windshield wipers, tachometer, speedometer, body bolts, the fifth wheel and the clutch.
In inspection of the wipers, operate the switch (electric type) or valve (air-pressure type) as a check on both the control and the motor. Observe if the wiper blades wipe the glass clean. The feather edge cuts and wears uneven from dirt on the windshield. This causes streaks and strips of unwiped areas to interfere with driver vision. Replace the wiper blades if they do not wipe clean.
Oil the linkage that connects the wiper arms to the motor, using only a drop or two of oil (S.A.E. 10) at each hinge pin.
For the electric-type wiper, check the terminal screws at both the switch and the motor to be sure they are tight. Don’t guess, use a screw driver to be sure. For the air-operated-type windshield wiper, check the tubing fittings to be sure there is no air leak.
There are two types of tachometers and speedometers in fire service usemechanical drive and electrical drive. For the mechanical type, the recording instrument is connected by a flexible cable to the source of the speed to be recorded as indicated. The only maintenance required would be when the driving cable causes erratic action of the speed indicator. Before this condition becomes noticeable, the driving cable may produce a “clicking” sound as the instrument is recording, usually most noticeable at low speed. To correct the trouble, the drive cable assembly must be removed from the apparatus, the cable removed from the flexible tube and thoroughly inspected for broken strands. If there are broken strands, the cable should be replaced With a new one.
If no strands are found broken, or a new cable is purchased, it should be thoroughly lubricated with a special cable lubricant such as AC No. T-640. The lubricant recommended for speedometer and tachometer cables is especially compounded so that the viscosity is fairly uniform over a wide temperature range.
It must not harden or stiffen at low temperatures and must not thin out as a liquid, to puddle” at high temperatures. It must have good adhesive quality and be corrosion resistant. Ordinary grease will not suffice.
The electric-type tachometer and speedometer have the usual electric terminals that should be inspected to be sure they are clean and tight. The only part that requires replacement, if the unit malfunctions, is the switch-sending unit. Make sure it is replaced by a unit from the same manufacturer and same model or part number as the unit removed from the apparatus. You cannot make substitutions and have the instrument record properly. When removing any wires from terminals, make sure they are marked so that they can be correctly reassembled. If they are not reassembled to the proper terminal, the polarity will be changed and the instrument will not operate properly and may be damaged.
Body bolts usually give no trouble, particularly those used to attach the body to the chassis frame. It is different, however, with bolts used to attach vertical partitions and side panels. The flexing of the chassis frame as the apparatus moves on the street causes some movement between the vertical panels that will continue to loosen bolts, no matter how tight you draw them. It is better to use some of the special nylon-type locknuts which will not work loose, and yet will permit the required movement of vertical panels.
Cab-mounting bolts seldom loosen, but you should still inspect them with a wrench to be sure they are tight.
Our Inspection Report Form lists “fifth wheel mounting,” which obviously refers to a tractor-drawn aerial ladder truck or water tower. Those departments without this type of equipment would ignore the item, but where such a unit is in service a very careful inspection of the fifth wheel mounting should be made. The fifth wheel should also be lubricated in accordance with the manufacturer’s instructions.
In the fifth wheel design as used in the fire service, the upper half and the lower half depend on this lubrication to maintain separation and avoid metal-to-metal contact. Both the top and bottom halves are usually of the same material (cast steel), and when metal-to-metal contact occurs, there is a “pick-up.” That is, spots of metal from one-half will weld themselves to the other half, and thus a smooth bearing surface will cease to exist. The result is that usually, in a very few more turns, a complete welding of the two halves takes place.
When this happens—and it always does occur when the vehicle is moving on the street—the driver can no longer control the direction of the apparatus. It locks in a straight-ahead position, usually, and turning the front or tiller wheels will not appreciably change direction. An accident usually occurs, as the driver is not aware of the condition until he tries to turn a corner. Unless he can brake to an immediate stop, he is in deep trouble. Several such accidents have occurred from this cause. One manufacturer has been using a thin brass disc between the upper and lower half to avoid this “pick-up” of similar metals.
Commercial tractor-trailer operators lubricate the fifth wheel very frequently; some lubricate every day and most at least once each week. In the fire service, due to limited travel, lubrication once a month is adequate for the fifth wheel.
“When lubricating the fifth wheel, use the mechanical jacks that are attached to the trailer-chassis frame and apply sufficient pressure at the adjusting screws to take most or all of the trailer weight from the fifth wheel. This will permit the lubricant to How freely, covering all contact surfaces. Use an EP (extreme pressure) lubricant as recommended for hypoid rear axles.
The inspection of door glasses and mirrors should include more than an inspection and report for replacement for cracked or broken glass. Operate any movable windows to be sure that no binding or excessive looseness exists that will cause a broken glass.
Hood, fenders and running boards require inspection for loose mounting bolts. In particular, look for evidence of corrosion which should be reported, so that proper protective finish can be applied before the part must be replaced. With the increased use of salt on streets and highways, the corrosion problem requires constant attention and treatment in the winter months to avoid excessive repair and replacement costs.
Clutch inspection on our monthly report is basically to check the free movement of the clutch pedal from the free release position to the point where clutch release starts. This clearance should be from 1 inch to 1 1/2 inches. If the clearance is 3/4 inch or less, the condition should be reported and the clutch readjusted to provide proper release clearance. If this is not done, a bad slipping condition can develop, resulting in a burned-out clutch. Do not adjust the clutch pedal linkage to get proper release clearance.
Gear shift mechanism should be checked to be sure it is operating freely without binding. This is important on the remote shift control such as cab-overengine and cab-ahead-of-engine apparatus. Hard shifting due to binding or drag from lack of lubrication usually results in excessive gear clashing and lost shifts, with resulting difficulty in apparatus movement.