Lawn Mower Engine Disassembly

Choosing a Lawn Mower Motor Lawn mower motor, features vertical shaft asynchronous motors. How to replace a defective mower motor with a new one?

What to choose?

For large. 20-60 hectare. A lawn mower is suitable for gasoline or diesel fuel, and not electricity. If the choice still fell on a trimmer, lawn mowers with an asynchronous engine are cheaper than similar models in which a synchronous motor is built. Asynchronous lawn mowers are mainly equipped with direct drive.

The most popular trimmer of the following companies:

  • Honda;
  • Briggsstratton;
  • Lifan;
  • Dde;
  • Patriot;
  • Mitsubishi;
  • Caiman;
  • Champion.

So, Honda engines expensive. The motor itself costs from 5 to 30 thousand rubles, depending on the power. American Briggs enginesStratton, not inferior to engines from the same “Honda”, put in devices from Snapper, Ferris, Simplicity and Murray.

For example, if you are changing the motor on a lawnmower that uses a direct drive asynchronous motor, check to see if there are models compatible with yours that use a similar motor and drive. This method is good when your model is already 5 or more years old, it has been discontinued. You can try to restore your old device without purchasing a new one. Self-propelled lawn mowers require more powerful engines than non-self-propelled ones. Part of the energy is spent on the fact that the lawn mower “goes by itself” during operation.

Features of electric motors

An electric motor converts electrical energy into mechanical energy, delivering torque. Through the gearbox, this kinetic energy is transferred to the knives or a drum with line (or cord), which cuts the grass.

The electric motor itself is economical. There is no need to choose whether to burn gasoline, a liter of which in 2019 is approaching 50 rubles, or to consume 10-15 kilowatts from the outlet for the same money. And the price of an electric motor equivalent to all the same 5 “horses” is much lower. The electric motor can be operated from an outlet and from a battery. It is ideal for owners of small summer cottages with a plot of no more than a few hundred square meters.

The electric motor must be turned off every 15-20 minutes for at least 20 minutes. This will allow it to cool down. It heats up much faster under load from the mowed grass than without it. If you ignore the breaks, then such a motor will not work for a long time. Overheating motor windings will gradually burn out.

lawn mower engine disassembly

Synchronous motor

The name of this type of motor speaks for itself, and the principle of operation is as follows: the rotating structure. The rotor. Exactly falls into the oscillations of the induction field generated by the windings of the stator part. The field speed matches the rotor speed.

The power consumption of a synchronous motor is more than a kilowatt, which is explained by its complicated circuit. The rotor winding is designed for a single phase. The winding itself is powered by a direct current source, and sliding contacts. Rings and brushes. Are connected to it. Even with a significant load on the rotor axle, this motor does not reduce the rotor speed (rpm).

In lawn mowers, the motor shaft is positioned vertically. This allows it to transmit maximum torque through a gearbox or belt drive to the working drum.

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Lawn mower motor: synchronous or asynchronous

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 starts to “junk”. Accordingly, it requires attention. He can:

  • Overheat and shut down.
  • Do not pull on power.
  • Just burn out (worst case).

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 have selected tips on which electric lawn mower motor to choose, taking into account your capabilities and needs.

A bit of theory

Before you solve the problem of which lawn mower to choose for working on your lawn, you should know that the electric motor of a lawn mower is of two types:

  1. Synchronous. It is a motor in which the rotor and the 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 a stable speed. To achieve this result, sliding contacts are used. Therefore, a synchronous motor is more complex in design, and therefore more expensive in terms of cost.
  2. Asynchronous. A motor 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 manufacture as a synchronous one.

Which lawn mower motor is better, there is no definite answer. Both types of engine have their own advantages and disadvantages.

For those who do not want to delve deeply into the wisdom of electromechanics, the explanation is quite simple. Each motor has two key elements: the stator (immovable, with windings) and the rotor (movable). The current from the electrical network is supplied to the stator. A magnetic field arises in its winding, which rotates. Thanks to him, the rotor also begins to rotate. And already the revolutions of the rotor are transmitted to the shaft of the device.

In our case, on the vertical shaft on which the lawn mower cutting blade is installed. It turns out that the work of the knife directly depends on the engine speed. Stable rpm. The knife rotates just as stably and powerfully. Weak rotor speed. The knife also begins to weaken, tightens the grass. He simply “does not have the strength” to quickly and efficiently cut vegetation.
In a very short way to determine which lawn mower is better, let’s say this:

But this is all a bit exaggerated, and in no way means that the induction motor is worse. An asynchronous motor is the simplest and cheapest of all those previously invented. It does not require complicated maintenance, does not get very hot, it does not have rubbing contacts. And its reliability is within the normal range, if the manufacturer is of high quality and has installed protective systems.

Electric lawn mower with synchronous motor

A synchronous motor always runs at a constant speed. Due to this factor, it is used where stable turnovers are especially needed. In lawn mowers, this moment is key and not necessary. Synchronicity is also important at high engine power. In mowers, this is more than 1 kW. The blade in synchronous lawn mowers is located on a separate shaft. This shaft is connected to the motor shaft by a belt drive. The weak point is the knife shaft bearings.

  • Low sensitivity to power line voltage surges.
  • Stable rotation of the cutting blade, regardless of the load.
  • High efficiency and power factor.
  • Complex construction.
  • The brushes heat up when rubbed.
  • Difficult start. To make it easier, the rotor first starts up asynchronously and then adjusts to the magnetic field.
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Electric lawnmower with asynchronous motor

Currently, asynchronous motors are used more and more in lawn mowers. In this case, the knife is placed directly on the motor shaft. The result is a simple and rather reliable design. There is no rotor winding. There are no brushes. Nothing fancy and everything works fine.

  • Simple construction. No maintenance needed. Easy repair.
  • Low manufacturing and operating costs.
  • Heats up less. Even if it heats up, it continues to work, while losing speed.
  • The efficiency and power factor are lower than that of a synchronous motor.
  • It is difficult to regulate the speed of rotation. Low controllability.
  • Turnovers depend on the network.
  • Very sensitive to voltage surges in the fixed 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.

Spring tension

After installing the spring, tighten it. To do this, perform the following actions:

  • Remove the handle from the starter cord;
  • Then the rope is inserted into the reel groove;
  • Tension the spring by rotating the coil in the opposite direction to the clockwise direction (winding);
  • Make the required number of revolutions specified in the operating instructions for the trimmer used and corresponding to the length of the cord used;
  • At the very end, the rope is threaded into the hole intended for this, located in the starter cover;
  • Put the handle in place, fixing it with a knot.

If after repair the spring continues to fly, then you can get rid of this in the following ways:

  • Squeeze a piece of the plate suitable in size into the groove at the location of the spring hook;
  • Drill holes on both sides of the groove in the spool, into which to insert the spring hook and fix it with a wire.

How to repair a trimmer starter

Petrol trimmer starter repair may be required at the most inopportune moment. In this case, the problem can be solved in two ways: replace the broken part or change the entire unit. The latter option is more expensive. To repair the device with your own hands, in most cases, you only need a screwdriver with the appropriate tip from the tools. Repair work does not take much time and does not require special knowledge. It is enough to know the device, the principle of operation, the nuances of assembling and disassembling the starter on the trimmer in order to achieve the desired positive result.

Disassembly of the starter unit

The launch mechanism is disassembled in order to install new parts instead of broken ones in the following sequence:

  • Unscrew with a screwdriver the screw fixing the pulley with the starter cover;
  • Take out the spring and antennae;
  • Carefully remove the pulley (you need to turn your head away or work, wearing glasses and gloves first);
  • Determine why the trigger has broken;
  • If the spring has collapsed almost completely, then it is replaced;
  • When the spring comes out of the hook, it is installed in its original place, bending the antennae in front of this (the photographs show the laying process);
  • After the spring plate is installed inside the groove, carefully twist it.
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To change the spring, you must work carefully and carefully: it can accidentally burst under the influence of the force caused by installing it in place. Even if you carefully remove the roller, the spring strip very quickly flies off the reel and can injure your hand with its sharp edges.

Mechanical repair for all types of lawn mowers

Regardless of the type of engine, the mechanical part of the scythe includes knives, a device for ejecting or accumulating cut grass and a transmission mechanism. Most often, knives fail or line ends.

Cleaning the mechanical part of the Bosh lawn mower

Broken or bent knives are visible to the naked eye. Depending on the material and the degree of damage, the knives are replaced or restored by simply folding them back to their original state. With heavy wear, the cutting part can be sharpened. A do-it-yourself lawn mower from a trimmer can fail for many reasons. Most often this is an excess of the maximum permissible load on the torque and engine, since a knife is used instead of a fishing line.

Restoration of the throttle handle

When inspecting, check the condition of the grass supply duct into the container and, if necessary, clean it. Complex mechanical failures require a complex tool, special equipment, professional skills and it is better to entrust the elimination of such malfunctions to professionals.

DIY electric lawn mower repair

Not only factory, but also home-made electric lawn mowers fail. The main reason for stopping the electric motor is loss of contact and lack of power at the motor terminals.

Therefore, first of all, we check the presence of voltage in the power outlet, the condition of the electrical cord and the absence of its breakage. Then, if a collector motor is used, you need to check the condition of the brushes and replace them with severe wear. The brushed hand lawnmower offers increased durability, but requires regular brush replacement.

Asynchronous motor mowers also have problems. The phase-shifting capacitor often fails, but testing it in the field is problematic. An indirect indication of a capacitor failure is:

  • Jerking of the motor at the time of power supply;
  • Strong heating of the engine even at low load;
  • Reduced speed;
  • Characteristic buzz.

Do-it-yourself electric lawn mower is made from scrap materials that can fail. If a malfunction is detected, in any case, you need to make sure that voltage is applied to the motor terminals, and in its absence. Check the operation of the switch.

If there is voltage, capacitor or brushes. Ok, the most likely cause of failure is a burnt-out winding. In this case, the unit will have to be handed over to a repair shop. Home-made electric lawn mowers most often have to be repaired on their own, since when assembling the device, all the nuances of its work are not taken into account.

Do-it-yourself electric and gasoline lawn mowers repair

Repair of both gasoline and electric lawn mowers may be necessary at the most unexpected moment. We will tell you about the main breakdowns of homemade and branded equipment, tell you what to look for, and by what signs you can recognize a malfunction.