Several power tools come with electrical motors, including hedge clippers, chainsaws, rotary mowers, nylon string trimmers, and edgers.
The amperage (amps) the motor needs to run is a measure of the strength of current needed to make the tool do its intended job. Therefore, the more amps that are needed, the more powerful the motor will be. Amps also can be converted into horsepower, the more familiar measure of current or machine strength. Thus, 10 amps are equal to 1/2 horsepower, 16 amps to 1 horsepower, and 24 amps to 2 horsepower. Most electrical garden equipment falls within the 10- to 24-amp range. Read the label on the motor to find out the strength of your equipment.
A metal housing—the protective covering around the motor—requires a three-prong plug. If a short should ever occur in the wiring, this third wire will prevent the current from traveling through the metal housing and shocking the user. Motors with plastic housing require only a two-prong plug.
Better-quality motors have roller bearings at either end of the rotating shaft (called the armature); lesser-quality motors have bushings.
To prevent the trigger switch from burning out, don’t stop the motor while you’re in the midst of heavy work. The current that flows across the contact points when you activate the motor (via the trigger switch) may not stop immediately; it could arc across the contacts and damage them. Therefore, let the motor idle a moment before releasing the trigger switch.
Start the motor and let it reach full speed before actually using the equipment. In fact, it’s better for the motor to operate at close to full speed than at a slow speed.
Keep electrical motors free of water and dust or dirt. With a light oil, lubricate the motor only as often as the instructions suggest—too much oil could cause damage. In addition, make sure that there is absolutely no water in the area where you are operating the equipment—the combination of water and electricity is dangerous. Never drag electrical cords through puddles or plug them in with wet hands.
Choosing cords for electrical garden equipment requires some attention. Select the gauge of wire according to the amps required by the motor. This chart is accurate with up to 100 feet of cord. If you require greater length than that, get advice from an electrical supply store.
|Amperage drawn||Gauge of Wire|
Replacing a Plug
The insulation on an electrical appliance cord can become worn or broken, exposing the wires. This situation is both a shock hazard and a fire hazard; it should be corrected immediately. If the insulation is worn in the middle of the cord, wrap that section with several layers of plastic electrician’s tape. If it’s worn near the plug, cut the cord to eliminate the worn area, and then reinstall the plug.
To reinstall the plug, first remove the old wiring from the plug. Pry up the protective plate around the two prongs to expose the terminal screws. Loosen them and remove the old wire.
Push the good section of wire through the plug hole, and split the cord back about 3 inches. Strip about 1 inch of insulation from the ends. Tie the cord, then pull the knot firmly against the plug.
Twist the strands of each wire into a rope. Then wrap each one, clockwise, under a terminal screw. Make the wrap two-thirds to three-quarters around. Tighten the screws and replace the cover plate.
Changing Brushes on Electrical Motors
Worn brushes may cause an electrical power tool to run poorly or even fail to run. Brushes are actually carbon blocks that press against the armature (often called a rotor) in the motor. They conduct electricity and are instrumental in setting up the electromagnetic field that makes the motor turn.
Brushes are usually good for years of service, but they eventually wear down. If the engine is running poorly or not at all, check the brushes. They normally are located under a slotted cap that unscrews from the motor housing. When removing the cap, be careful that the brushes don’t fly out—they are spring loaded.
If the brushes are worn thinner than they are wide, replace them. Make sure the spring is firm enough to provide good pressure.
If the brushes are in good shape and the motor still runs poorly, the problem may be a dirty armature. Remove the motor housing and spray the armature with electrical contact cleaner (often sold as a TV-tuner cleaner).