Electric lawn mower. not the simplest equipment, and if it is not purchased by a specialist (that is, not an electrician), then he is unlikely to be interested in the question of what type of engine is installed in it. The problem becomes relevant only when the engine begins to “junk”. Accordingly, it requires attention. He can:
- Overheat and shut down.
- Do not “pull” in power.
- Just burn out (worst case scenario).
In any of these cases, the user begins to repair or replace the engine, and then, finally, he finds out what kind of electric motor his equipment has.
In order to save you from such unpleasant moments, we picked up advice on which electric motor for lawn mowers to choose, taking into account their capabilities and needs.
Bit of theory
Before solving the problem of choosing a lawn mower to work on your lawn, you should know that there are two types of electric motors for a lawn mower:
- Synchronous. This is a motor in which the rotor and magnetic field rotate at the same speed. synchronously. Even if the rotor receives a heavy load during operation, its speed does not decrease. The engine continues to run at stable speeds. To achieve this result, sliding contacts are used. Therefore, a synchronous motor is more complex in design, and therefore more expensive at cost.
- Asynchronous. An engine in which the rotor speed does not match the speed of the magnetic field. The stator and rotor are separated by an air gap, there are no slip rings. It is simple in structure, which means that it is not as difficult and expensive to make it as synchronous.
Which motor of the lawnmower is better cannot be answered unequivocally. Both types of engines have their advantages and disadvantages.
For those who do not want to delve deeply into the wisdom of electromechanics, we explain very simply. Each motor has two key elements: a stator (immovable, with windings) and a rotor (movable). Current from the mains is supplied to the stator. A magnetic field appears in its winding, which rotates. Thanks to him, the rotor also begins to rotate. And already the rotor speed is transmitted to the device shaft.
In our case, on a vertical shaft on which a cutting knife of a lawn mower is mounted. It turns out that the operation of the knife directly depends on the engine speed. Stable revolutions. the knife also rotates stably and powerfully. Weak rotor speed. the knife also begins to weaken, tightens the grass. He simply has “no strength” to quickly and efficiently cut vegetation.
To determine very briefly which lawnmower is better, let’s say this:
But all this is a little exaggerated, and in no way means that the induction motor is worse. Asynchronous motor is the simplest and cheapest of all previously invented. It does not require complicated maintenance, does not heat up much, it does not have rubbing contacts. Yes, and its reliability is within normal limits, if the manufacturer is of high quality and has installed protective systems.
Synchronous Electric Lawn Mower
The synchronous motor always runs at a constant speed. Due to this factor, it is used where stable turns are especially needed. In lawn mowers, this moment is key and necessary. Also, synchronization is important with high engine power. In mowers, this is more than 1 kW. The knife in synchronized lawn mowers is placed on a separate shaft. This shaft is connected to the engine shaft by a belt drive. Weak point. knife shaft bearings.
- Low sensitivity to power surges.
- Stable rotation of the cutting knife, regardless of load.
- High efficiency and power factor.
- Sophisticated design.
- Brushes with friction are heated.
- Hard start. To facilitate this, the rotor is first started asynchronously, and then it is adjusted to the magnetic field.
Asynchronous Electric Lawn Mower
Currently, asynchronous motors in lawn mowers are used more and more often. In this case, the knife is placed directly on the motor shaft. It turns out a simple and fairly reliable design. There is no rotor winding. There are no brushes. Nothing complicated, and everything works fine.
- Simple construction. No maintenance needed. Easy repair.
- Low cost of manufacturing and operation.
- Heats less. Even if it heats up, it continues to work, losing momentum.
- Efficiency and power factor lower than that of a synchronous motor.
- It is difficult to regulate the speed of revolutions. low controllability.
- Turnovers are network dependent.
- Very sensitive to power surges in a stationary network.
Thus, when choosing synchronous or asynchronous lawn mowers, you should be guided by considerations of either low cost, or decide which is more reliable in operation.
Video: Which Electric Motor To Put On A Lawn Mower
So, spring, weed climbed, not the one that some “lovers” smoke, but the lawn.
Today, a wide selection of different lawn mowers is offered, mainly in China. But even the best Western counterparts, very often break on our lawns. Toli weed them our domestic is too tough, roofing felts are affected by the untidiness of our lawns. After all, stones and sticks are found on them. Yes, mow these lawns from case to case.
And even very western designers are fond of plastic aggregates, which of course makes the lawn mower easier in weight, but greatly reduces its reliability in our conditions. And the price of the purchased equipment bites. The question became about my own and strong. Preference is given precisely to a mower on wheels. Because the haircut is beautiful and even. Even if the terrain is uneven. I have already made several such mowers, at the request of neighbors and acquaintances, even those who have already managed to acquire an overseas miracle. For four years now, tests have been under the most severe conditions. Everyone is satisfied, with proper care of which I will write below, no damage was observed.
Electric lawn mowers and lawn mowers are not suitable. Firstly, the cutting line wears out quickly and is not cheap, and the quality of the haircut does not hold water. They are good at mowing weeds and inconvenience.
To make a home-made lawn mower, we need four wheels from a baby stroller that has served its term. Or even better, a solid chassis from the Soviet carriage, then the manufacture will be greatly simplified. From the beginning, you need to determine the width of the grip. It depends on how much power we need an electric motor. In general, there is a special conversation about the electric motor. Experimentally tested with a working width of half a meter, an electric motor of 900 W.-1.2 kW is suitable. At 1500 vol. min or 3000 vol. 600-800 watts. Since there are no gearboxes, torque plays a role here. Use anchor engines, such as a vacuum cleaner, I would not recommend. Although the speed there is huge and light weight, and it would seem sufficient power. But chasing air and mowing grass is a big difference. It will quickly overheat and fail.
The smallest mower I collected had a working width of 28 cm and an engine of 3000 rpm. at 250 watts. I took the electric motor from the centrifuge of the washing machine. This mower is convenient for working under trees and bushes. I’ll try to describe in more detail with a working width of 50 cm.
It’s very convenient to make a chassis from a baby carriage, it has the most optimal size and width of the grip that is half a meter, and passes through all the doors.
Everything superfluous is trimmed from the stroller, we leave only the chassis. Two pieces of rectangular-shaped pipe are welded to the transverse rods, which are a kind of wheel axles, at such a distance from each other so that they coincide with the mountings of the electric motor of your choice. It’s good if the electric motor is with end-mounts, but I have come across more and more with the side. Therefore, two vertical corners with a shelf of 40 mm were welded to the profiles, for mounting an electric motor. Pipes with corners are welded so that the motor shaft is exactly in the center of the chassis and the end of the shaft is 5-7 cm from the ground. This distance determines the height of the grass after mowing.
The protective cover is made of 1.2 mm sheet steel. A circle with a diameter of 53 cm is drawn with the help of a compass. and cut out (you can angle grinder), In the center. a hole larger by 4mm. motor shaft. The side of the casing is a 5cm strip of the same steel. After manufacturing the casing, we weld it to the pipes so that the end of the motor shaft is overlapped by the casing rim by 2.5 cm.
Now the working body of the lawn mower is a knife. This is a disk with a diameter of 38 cm. It is cut from 2.5-3mm sheet steel. It must be cut as carefully as possible. In the center of the hole is equal to the diameter of the motor shaft. At the edges, two more M6 holes are strictly symmetrical at a distance of 2 cm from the edge of the disk, for attaching the actual cutting knives. We dress the disk on the motor shaft so that the end of the shaft is flush with the disk, and fasten by welding. We carry out welding accurately and efficiently, checking by rotating the disk, for the absence of any runout. It may seem to some to be a perversion of welding a disk to the shaft of an electric motor. And for the impossibility of disassembly and repair, but this is a mistake. If, for example, the engine burns out, then it simply disassembles in place, the rear flange is removed and the stator is pulled out, which is then transferred to rewind. It is impossible to break the rotor; it remains on the mower, even if the front bearing fails, which is extremely rare, the angle grinder carefully removes the weld and the rotor is completely removed.
And why the disc, and not for example two long knives? No matter how strong steel these knives were made, they would still break them from an impact on any obstacle, stone or stick, and this would not threaten the disk. Knives are made of good alloy steel. For example, from a hacksaw blade of a two-handed saw. Their configuration does not matter. Length 9cm, width 3cm. we retreat one centimeter from one edge and make an M6 hole for attaching to the disk. It is impossible to make a hole with a drill. Therefore, it is better to carefully burn by welding. We attach to the disk with M6 bolts, but the most important thing is that we do not tighten the bolts, but use additional lock nuts. So that the knife does not hang out and at the same time easily rotates. This is the whole secret. When you hit a stone, the knife turns and does not break. Then, due to centrifugal force, it immediately returns to its working position. Knives can be sharpened, but shears well and blunt knives.
After installing the knives, it is advisable to balance the disc. To do this, turn the mower on its side and rotate the disk. If the disk stubbornly stops in one position, it means that a small hole must be drilled at the lower point. So do several times until an acceptable balance. Good balancing is considered if no vibration is observed during operation. Weld the handle to the lawn mower to fit your height. Can be used from the same stroller. We install a switch and a start button on the handle if the engine is three-phase.
Maintenance consists in the fact that after about 20-30 hours of operation we remove the knives for sharpening and be sure to change their fastening bolts. Bolts made of ordinary mild steel are gradually cut by hardened knives during operation.
The mower cuts not only grass, but also young growth of trees. Therefore, be careful if there are seedlings on the site.
About safety: when cutting, keep an eye on the carrying cable and never run over the mower. This is fraught not only with cable damage, but also with electric shock.