FIRE APPARATUS MAINTENANCE

FIRE APPARATUS MAINTENANCE

DEPARTMENTS

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.

FIRE APPARATUS MAINTENANCE

FIRE APPARATUS MAINTENANCE

WHILE our inspection report does not mention ignition system distributors, let us not forget they must be included in the checkup. Remove the distributor cap and examine the interior to be sure it is clean, with no evidence of oil film to start a “carbon track” between terminals in the cap. If there is evidence of an oily film, wipe the inside of the cap with a clean cloth to remove it.

With the ignition switch in the OFF position, have an assistant touch the starting motor switch to make the engine turn two or three revolutions while you observe the opening of the points and particularly the faces of the contacts. Be sure the contact points are seating squarely and there are no “peaks” and “pits” on the face of either point. If the faces are smooth, the point gap can be checked when the cam is at maximum lift position. If the contact points show pitting, the points should be replaced. Do not attempt to check the gap when the points are pitted as the setting will be incorrect.

No lubrication of the distributor is required except on a once-a-year basis. Overlubrication can be as harmful to this unit (oil causes burning of the points) as lack of lubrication. This emphasizes again the importance of a definite maintenance schedule.

Instruments and gages should be checked to observe if they are registering correctly. Any gages that fail to register, or are reading incorrectly, should be replaced by a gage of the same model and make. Do not attempt to repair.

Gages of the two-unit type, where the resistance or “sending” unit is separate from the indicating gage, must be replaced in matched sets. Never replace only one unit—for example, a StewartWarner gage with an AC or King-Sealy gage—without changing both units. Unless both units are made by the same manufacturer, incorrect readings will result.

Lights, signaling devices and switches can be readily checked by visual observation and operation. Any lights that have less intensity or brilliancy than normal should he checked for: (1) loose mounting bolts; (2) loose terminal connections; (3) corroded ground connection.

Obviously any burned-out lights, broken lights, switches or motors should be replaced with new units. Check carefully all terminal connections. Lights that look good with the apparatus standing on the station floor may flicker and dim when traveling on the street, due to loose connections and poor ground.

The voltage and current regulators require little care or maintenance, other than to be sure terminal connections are tight and free from corrosion. The only maintenance that should be attempted with the regulator on the apparatus is cleaning and adjusting the contact points. Be sure the battery is disconnected before starting any maintenance tests or operations.

To clean the contact points use a ½-inch strip of crocus cloth or aloxite or alundum cloth of 180 grit, or finer, as it is only necessary to remove the oxide coating on the face of the contact points to expose bare metal. It is not necessary to remove any cavity that may have developed. Never use emery cloth or sandpaper. Clean thoroughly to remove dust and grit around the points with alcohol or a good nontoxic cleaner.

To smooth the contact faces, draw a strip of smooth-surface, hard bond paper across them several times with the contacts closed lightly on the paper. If no scratches show on the paper, the contact points are satisfactory.

Testing the voltage and current regulators requires proper instruments, and is a maintenance operation greater than this 30-day inspection would include.

When inspecting the regulator be careful not to close the cut-out relay contact points by hand with the battery connected to the regulator. Closing these points will cause a high current flow through the units and damage them.

To some people the job of inspection and maintenance is just a job and they are inclined to take the easy way. To the writer there is no vocation or profession that returns greater dividends in personal satisfaction and that feeling of pride than to have a machine working in top condition after such an inspection, with the small amount of maintenance usually required. Part of this satisfaction is derived from knowing what adjustments and care are required, and making them. As we progress through the selected maintenance report form (FIRE ENGINEERING, February 1965, page 42), if any points are not clear, or if additional information is desired, we will be glad to help upon request.

The starting motor seldom requires any maintenance other than annual lubrication. We should make an inspection, however, as it may prevent a starting motor failure, which means failure of the apparatus to respond in an emergency.

Remove the cover band over the commutator end of the starting motor. Examine it for evidence of solder particles which may be thrown from the armature. The drive ratio between the starter pinion and the engine flywheel ring gear is about 20 to 1. If the engine is started with the throttle partly open, the engine speed may be 1500 rpm before the starter pinion disengages. This would mean a speed of about 30,000 rpm of the starting motor armature, which is the cause of armature failure. If you find such evidence, report immediately to the chief officer of the department so that the driver may be properly instructed in the proper starting procedure of the engine.

We have courses in driver training, but I have yet to see such a course include proper engine starting technique. The throttle should be either closed, or just cracked open for starting. This throttle position permits the maximum vacuum in the intake manifold to get the mixture from the carburetor to the cylinders.

Never operate the starting motor more than 30 seconds continuously. After such a period, a cooling-off period of approximately 2 minutes is recommended.

Inspect the brushes to be sure (1) they are seating full width on the commutator, and (2) they are free in the brush holders and not binding at any point. If the brushes are worn to one-half their original length, they should be replaced. Observe the commutator to be sure it is clean and not worn so that the mica strips are higher than the copper bars. If they are not higher, the starting motor should be removed and the commutator turned on a lathe and properly conditioned. Make sure the starting motor mounting bolts are tight; also check the terminals to be sure they are clean and tight. Any fraying of the starting motor cables indicates a new cable should be installed. This cable carries a heavy electrical current and such fraying usually means some broken strands with dirt and moisture to leak off current, and thus reduce the power of the starting motor.

Any malfunction of the starling motor switch, either the foot-operated or the solenoid type, requires replacement of the unit. Do not attempt to repair it.

When making the annual lubrication, use only a few drops of a light engine oil (S.A.E. 10W) on the pinion drive. Never use a grease or heavy oil. Turn grease cups one full turn only, and for hinge cap oilers use 8 to 10 drops of medium engine oil (S.A.E. 30). Do not overlubricate and make sure no lubricant gets on the commutator.