In bump feed systems, varied lengths of line are wound around the spool of the trimmer with two equal lengths fed through openings in the trimmer head. These systems work by lightly tapping or “bumping” the bottom of the trimmer on the ground while you are trimming.
The line advances when the spring system releases the line through the line outlets. Bump feeds are easy-to-use, dependable, and tend to be the most popular feed system.
Pros: You have more control over how much line you are using. The bump feed is a more simplified method of string advancement. If it stops working, you can make repairs quickly and easily.
Cons: If your bump ever turns into a slam, you may damage the spool or spring. With continuous use, the spring in the head will wear and will need to be replaced.
Many trimmer models are designed with automatic feed systems. Similar to Bump Feed Systems, Auto feed systems use a line spooling motor, with no effort required while the trimmer is in use.
Pros: You can take the attention away from your line, and put it right where your property line and your neighborʼs award-winning azaleas meet. Since you don't have to tap the head on the ground, you can finish trimming faster.
Cons: As with any machine with an excess of moving parts, the motor may malfunction at some point. If the motor still works but it doesn't feed line properly, you may spend your trimming time fixing a line nightmare. Repairing or replacing the line spool motor on the automatic feed may be more of a headache than replacing the trimmer.
Fixed head systems use individual lengths of line that are loaded or threaded into the trimmer one at a time, as needed. This avoids some of the hassle of winding line onto trimmer heads, and makes the overall process of dealing with trimmer line less cumbersome.
Pros: Fixed head systems tend to be more popular with larger, more commercial trimmers that use, thick, tougher string. The increased diameter line decreases wear and breaks, making pauses between work fewer and further between.
Cons: The trimmer must be stopped each time line needs to be replaced.
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