Garden “barber”

Today we present a universal electric trimmer for mowing grass on lawns and shaping shrubs.

I once worked as a mechanic on garden and park machines, or simply gasoline lawn mowers. I often had to cut grass and shrubs in awkward places and on limited areas. Existing scythes and large hand shears were poorly suited for such work. So I decided to make my job easier — to design a portable hand tool for trimming shrubs, flower beds, and lawns. I studied domestic and foreign experience in building such mechanisms and sketched several trimmers with different drives, including an electric one. However, the idea was still far from realization: one unit would not suit me, then another.

Finally, after a long search, I produced an electric trimmer that, I believe, favorably differs from similar ones in the universality of its design and can be used not only for trimming lawn edges and awkward spots, but also for shrubs. I called it EKU-1: electric trimmer, universal, first. Here are some of its features.

First of all, lightness: the weight is 1.3 kg. This is very important when working on shrubs, since the tool has to be held up for hours. The pole-handle is made “folding,” which makes it possible to change the blade position depending on working conditions and the relief of the surface being trimmed.

The EKU-1 is arranged simply: a protective housing is attached to the electric motor with a cutting element on the end of the shaft, and a long pole-handle is attached to the housing. The DPM-35 motor is designed for 24 V DC, its power is 72 W, and the shaft speed is 9000 rpm. A similar motor is used in some brands of transistor portable tape recorders, as well as in automation systems. But motors from coffee grinders or vacuum cleaners can also be used. However, the insulation will have to be reinforced, since the power source will then be the AC mains directly, and the trimmer’s weight will increase to about 3 kg.

The cutting element (blade) is made of two thin duralumin plates joined with M4 screws. Safety razor blades are inserted between them so that they protrude from the plates by 0.5 mm. This prevents breakage of the cutting edge; moreover, using blades frees one from constant concern about blade sharpness.

To protect the motor from accidental impact loads, two separate blades can be made, hinged on the flange. During manufacture they must be carefully balanced; otherwise the trimmer will quickly fail.

When the motor is running, centrifugal force stabilizes the blades in the radial direction, and they easily cut grass; on impact with a hard object they deflect backward, softening the blow.

The blade is covered on top by a protective housing consisting of a dome and “spokes” made of thin sheet duralumin. The spokes, which protect the blades from breakage and help cut plant stems, are joined to the dome with bent tabs on epoxy adhesive. The ends of the spokes have protrusions that set the grass cutting height.

A pole-handle made from a duralumin ski pole is also attached to the housing. At its upper end there is a plug connector, a motor switch button, and a double reverse microswitch. A wire runs through the tube from them to the motor. (When powered from the AC mains, the handle is made from a plastic ski pole.)

At the lower end of the tube, a fork with a folding device is mounted. The fork, with longitudinal stiffening ribs, is made of thin sheet duralumin. The folding device is a tube attached to the fork with an M4 screw on epoxy adhesive. Cutouts are made in it to change the position of the trimmer’s cutting element. The pole-handle is fixed to the lugs of the protective housing with screws and wing nuts.

The drawing shows possible ways of using the trimmer with such a handle. Obviously, few other tools would provide similar reach zones. In addition, for mowing grass on plots with uneven borders, a piece of nylon cord or a metal guitar string can be used instead of a blade.

«M-K» 6’85, A. BOCHKOV