Rycho T wrote:
In automatic heads, the line feed is slow all the time while it is running.
I don't agree with that.
In automatic heads, e.g. Husqvarna, the line is retracted only when both ends become too short or one breaks off. In the Superauto and Superauto 2 heads, you can hear a pop and the line jumps out one step of the internal hooks - about 1/4 of a turn of the spool.
However, this system works properly only when the monofilament line is of the appropriate thickness (in the manual of the head min/max thickness is given) and when the head is well twisted, no inner washer is missing and the monofilament inside is wound in the right direction

In addition, the head must be matched (and/or set -> head instruction) to the power of the machine.
Regardless, in my opinion automatic machines are only suitable for relatively 'clean' terrain, because each sudden pull of the line sometimes ends with the whole or at least a long fragment. When working with the machine, the knife on the guard must be in good condition, otherwise there are problems with unwinding the line.
Quote: If we are at Husqvarna, it has heads with manual line extension.
The only problem is that you have to turn off the engine by pressing the button on top of the head and pulling the line. It will come out similarly to a semi-automatic.
http://www.husqvarna.com/en/landowner/accesso...t-accessories/g-blades-and-blades/trimmy-sii/
TrimmyII (and its earlier versions) is in my opinion the best head, in addition to the manual button, it has one more advantage - the bottom with bearings (and replaceable :!

stopping after touching the ground, thanks to which the head is not damaged quickly, especially where something protrudes from the soil.
Unfortunately, it is expensive and quite difficult to access, with 2 months ago I drove around the area and I couldn't buy it anywhere. In a few online stores, the price is greatly exaggerated, for the same amount you can buy 5-6 cheaper heads.