Mechanical lawn mowers are a whole class of special tools designed for cutting grass and do not have their own engine, but operate using any external energy sources.
Among the owners of personal plots there are quite a lot of adherents of this particular type of device.
And it's not just about the affordable price. They are easy to use, environmentally friendly and have a fairly gentle effect on the grass.
There are 3 types of mechanical lawn mowers:
- manual;
- mounted;
- trailed
Manual mechanical devices are in greatest demand, because they combine the advantages of small-sized lawn mowers, but do not have the limitations that are characteristic of other types of manual lawn mowers, that is:
- battery-powered;
- gasoline;
- electric.
Next, let's talk about the operating principle of mechanical lawn mowers and their types.
Principle of operation
Each device of this type is equipped with a drum cutting tool; only mounted and trailed devices are equipped with rotary cutting tools.
The drum cutting mechanism
consists of :
- knife drum;
- counter knife;
- drive mechanism.
The knife drum consists of :
- shaft (spindle);
- disks;
- cutting knives.
Let us describe how these types of mechanisms work.
The spindle is connected to one of the wheels through a step-up gearbox, due to which its rotation speed is several times higher than the speed of rotation of the wheel. The disks are rigidly fixed to the shaft , due to which they rotate with it.
The knives are mounted almost perpendicular to the discs and almost parallel to the shaft, thanks to a slight deflection they pass the counter knife like scissors, the point of contact moving from one edge to the other as the drum rotates.
The drum knives, as well as the counter knife, are sharpened at an angle of 90 degrees, which further enhances their resemblance to scissors. Thanks to this design of the spindle mechanism, the grass is cut in a small area at any given time , which reduces the load on the shaft and therefore requires less effort to rotate it. The counter blade is rigidly fixed to the frame of the lawn mower, so it is always in the same place in relation to the drum.
By turning the mower body relative to the ground, the cutting height is changed, while the counter blade is always in the same position in relation to the drum, which means that, regardless of the cutting height, the mechanism cuts the grass with the same efficiency.
Most often, the gearbox is made of plastic, with a large gear mounted on the wheel and a small one on the spindle, due to which the spindle rotation speed is several times higher than the wheel rotation speed. The disadvantage of this drive is very low power , so the lawn mower only cuts short and sparse grass well.
How it works?
The user, having selected a flat area with growing grass, pushes the lawn mower in front of him. From the support wheels, movement (rotation) is transmitted to the working shaft, and a horizontal and stationary knife is installed in front of it. In the process, the grass rests on a horizontal knife, and its even cut is carried out using a blade on a spiral. If the lawn mower is a contact mower, then the blades also maintain sharpening when they touch.
The mower design is based on:
- housing made of plastic or metal;
- movable wheels mounted on sliding bushings;
- cutting elements under the body.
Modern manual lawn mowers are classified into:
- Household. Light weight. The average width of the cutting blade is 34 centimeters. Ideal for processing vegetation no higher than 45 millimeters.
- Professional. Processing large areas. The average width of the cutting blade is 40 centimeters. It handles vegetation up to 5 centimeters well.
Types of manual mowers
Every owner of a personal plot sooner or later thinks about purchasing a lawn mower.
And at this moment the question arises, how to choose the right model? All devices of this type can be divided into types according to the following criteria :
- select forward or backward;
- the presence or absence of a bag for collecting grass;
- the presence or absence of additional wheels;
- contact or non-contact cutting mechanism.
Grass ejection direction
Most devices eject the cut grass back, so it can be left on the site or collected in a grass receptacle container. Some models are equipped with front discharge , the convenience of which is that the mowed vegetation does not fly under the operator’s feet and does not interfere with his movement.
The downside of this design is that the lawn mower is forced not only to cut, but also to chop up vegetation, because the cut green mass ends up in the path of the machine and is crushed.
With or without grass catcher
Models without a bag throw the grass back, which not only causes it to remain in the area, but also prevents the person operating the mower from moving forward.
Devices with a grass collector can work in both modes, that is, collecting grass in a container or throwing it back, so they are more versatile.
The grass catcher slightly increases the cost of the lawn mower, but those who value this function are willing to overpay for it .
Additional wheels
The front (large) wheels take on the weight of the machine and transmit rotational energy to the spindle that rotates the drum, however, to ensure stability of the cutting height, the mower must be correctly oriented relative to the ground.
This task is performed by the rear part of the lawn mower, and on most models it consists of a bracket and rubber or plastic rollers placed on it.
This design has 2 significant drawbacks:
- high resistance to movement in the area;
- changing the cutting height when driving over a hummock.
Lawn mowers that do not have rollers installed at the rear, but full-fledged wheels, are free from these disadvantages.
For models with front ejection, wheels installed at the front greatly increase cross-country ability, because they overcome bumps more easily than plastic rollers.
Cutting mechanism type
Despite the fact that all cutting mechanisms are made according to the same design, they are divided into 2 types :
- contact;
- contactless.
The difference between them is that with contact drum blades and the counter blade are in contact, which increases the noise level emitted by the mower, but the cut is clearer.
For non-contact devices, the distance between the drum knife and the counter knife is 0.05 mm , this only slightly reduces the clarity of the cut, but such devices produce noticeably less noise.
How to choose the right mechanical mower
For good, convenient work, you should decide on the following parameters:
- Width and height of cutting. The wider the blades, the more effort. When choosing, take into account the characteristics of the area with a lawn and its unevenness.
- Size of support wheels. High wheels are suitable for difficult terrain with bumps and uneven surfaces. Their fastening is also important. Wheel bearings are more durable and more expensive. With periodic lubrication, jamming will not occur.
- Attachments (additional) equipment, specifically the installation of a grass catcher.
It is good for a manual lawn mower and the user to have an adjustable cutting height.
Devices for tall grass
Tall grass, unlike vegetation that is trimmed regularly, has thick stems and leaves that a hand-held grass mower will not be able to cut through.
If the height of the grass exceeds the cutting height of a manual mower by 5–10 cm, then it can be mowed in several passes and then trimmed .
For taller vegetation, use other tools instead of a mower, such as a mechanical grass trimmer or any heavy-duty attachment.
Characteristics and prices of popular models
The prices of mechanical lawn mowers are much more modest compared to the cost of most electric and gasoline counterparts. For example, this article will talk about prices for gasoline manual lawn mowers, which are quite compact and do not require frequent use, unlike mechanical ones. And if you want to get acquainted with the reliability rating of electric lawn mowers, then this is the place for you.
The leaders in this market segment have established themselves. You are invited to familiarize yourself with the features of their products further.
CMI
The company offers a fairly large selection of high quality, reliable and easy-to-use manual reel lawn mowers to suit a wide range of needs. Most models are designed to process spacious areas up to 250 m2.
CMI device
The working cutting width is up to 30-35 cm, the height is up to 4-4.5 cm, and the weight of the units traditionally does not exceed 8-10 kilograms. At the same time, devices from this manufacturer are much cheaper than their analogues.
For example, a popular model with a 20-liter soft grass catcher can be bought for only 3 thousand rubles. Otherwise, prices vary depending on the characteristics and capabilities of the unit.
Husqvarna
Mowers traditionally occupy a leading position in the market of garden machinery and equipment. Among the most popular models of manual lawn mowers from this manufacturer, we should highlight the Husqvarna 54 NovoCut (equipped with 5 knives, capable of quickly mowing grass to a height of 13-38 mm, the cutting width is 4 cm) with an average cost of 9-10 thousand rubles and 64 NovoCut – the maximum cutting height here is increased to 55 mm, the average cost is 10-12 thousand, otherwise the characteristics are identical. However, let's face it, not all land owners have such finances, then we suggest you design a mechanical lawn mower with your own hands.
Popular Husqvarna model
Bosch
Equipment from the world famous manufacturer Bosch has long earned the reputation of high-quality, reliable and durable products. Among the mechanical lawn mowers produced under this brand, the AHM 30 model should be noted.
With an average cost of 6 thousand rubles, this lightweight and maneuverable unit can effectively process an area of up to 100 m2, providing a 30-centimeter width and a 12-40 mm cutting height.
Bosch mower
Here we mention the Bosch electric lawn mower, the quality of which justifies its seemingly inflated price.
Brands and ratings
Despite the fact that all manual mechanical lawn mowers are designed and operate on the same principle, the quality of grass cutting and the reliability of the device largely depend on the brand under which the model is made.
In addition, when choosing a specific mower, it is necessary to take into account not only its technical characteristics and descriptions available on the model page in the store, but also its position in the ranking of the most popular devices.
You will find a lot of useful information on these issues here: Rating of mechanical lawn mowers.
Specifications
Due to the simplicity of their design and characteristics, there are few mechanical lawn mowers. We indicate the following ranges of average characteristics of various models of lawn mowers:
Cutting width (cm) – from 30 to 40
Cutting height (mm) – from 12 to 55
Number of adjustment positions - from 3 to 7, or smooth (stepless)
Number of movable knives (pcs.) – 4; 5
Weight (kg) – from 6.4 to 9.8
Recommended lawn area (sq. m) - from 100 to 500
How to do it yourself?
On the Internet there are often recommendations for making lawn mowers with your own hands, which for some reason are called mechanical, but they are all equipped with electric or gasoline engines.
Those who decide to make a truly mechanical, rather than motorized, mower will have to make a cutting mechanism that meets three conditions:
- minimum mass required to quickly unwind the drum;
- perfect balancing, eliminating beating;
- highest manufacturing accuracy - tolerance 0.005 mm.
It is extremely difficult to fulfill these requirements in home-made conditions, and the costs of designing and assembling such a homemade product will many times exceed the costs of purchasing even an expensive model.
Safety precautions when operating mechanical lawn mowers
Mechanical lawn mowers are the safest devices among their electric and gasoline relatives.
They are not connected to the electrical network - which means there is no danger of electric shock; do not contain batteries - there is no danger of fires, chemical burns, there are no dangers in the process of charging batteries; they do not need gasoline - there are none of the dangers that are inherent in devices with gasoline engines.
Therefore, I will focus on the basic safety rules:
- Before starting work, carefully read the operating instructions (manual) for your lawn mower - all safety rules for using it are indicated there;
- Do not allow your feet or fingers to come into dangerous contact with the blade drum;
- Do not allow children or persons unfamiliar with the operating instructions to operate the lawnmower;
- There should be no strangers or animals in the immediate vicinity of the operating mower;
- Before starting work, check the lawn and remove foreign objects (toys, stones, branches, etc.);
- When working, use safety glasses, non-slip shoes, durable long trousers, and gloves.
Engine selection
The best option in this case would be an asynchronous electric motor with a power of 500 to 600 W and higher. The number of revolutions during this operation reaches 3000 per minute. The great advantage of the asynchronous motor model is its quiet operation. The higher the engine speed, the better and smoother the grass is cut.
In general, the quality of mowing will be determined not by the speed of rotation of the knives, but by the linear speed of movement of the cutting edge relative to the vegetation . At the same number of revolutions per minute, the linear speed of the cutters becomes higher, based on the grip size (the diameter of the circle along which the cutting edge rotates).
Therefore, with a large grip (more than forty centimeters), the number of revolutions of the device can be significantly reduced. But in this case, the motor power rating must be greater to overcome the increasing resistance. Practice has shown that the following configuration is workable: grip - 50 centimeters, engine power - 1 kW, number of revolutions per minute - 1500. But the grass will be mowed, although worse, by an engine with a power of 500 W and a rotation speed of 1500 rpm. With low motor power, you need to sharpen the knives regularly.
To connect a three-phase motor to a single-phase system, you need to use the principle with a running and starting capacitor. Information about such a connection can be easily found on the Internet. It will also be easy to find a formula for calculating the required capacitance for capacitors. Most often in design, about 200 uF is used for a motor with a power of 2 kW. For a power of 500-600 W, only 60-80 µF is enough.
When creating a special casing for the engine, you must remember about the holes for cooling the device.
You can create a lawn mower yourself by using a simple electric drill with a speed of up to 3000 per minute. It will be easy to come up with a method for installing the drill to the frame. But to do this, you need to understand that in terms of reliability and operating life, a drill cannot be compared with an asynchronous motor, which is why if you have to mow a large area of grass, then it is best to think about purchasing a powerful motor.
A drill is best suited for creating a separate stand-alone trimmer . It will be very easy to install knives into the drill. A knife with a hole in the center is clamped with a special nut on the bolt, and the bolt is clamped in the drill chuck.
Is a manual lawn mower suitable for small gardens?
Thanks to all of the above advantages, mechanical lawn mowers are best suited for prudent and economical homeowners who need to regularly mow a small lawn or area (up to 2-3 acres).
To care for such a small surface, using massive motorized lawn mowers is ineffective and too expensive. All due to high operating costs. Therefore, if you have a small lawn in front of your house, pay attention to manual lawn mowers.
Creating a Mandrel
The simplest mandrel design looks like a disk or strip with a flange, in which there is a special hole equal to the diameter of the engine shaft. The process for creating a mandrel is as follows :
- The flange is put on the shaft and locked on it; legs are attached to the strip or disk. The overall diameter of the leaf will directly depend on the desired working width and the length of the knives. For the finished mandrel, you can use a pulley with a landing diameter suitable for the shaft with the motor. This will help get rid of two difficulties at once - centering the mandrel and its installation. But the pulley must be reliable and strong.
- The mandrel must be secured to the motor shaft. Most often this is done with bolts that are screwed into the flange perpendicular to the shaft axis.
- A stone holder for a sharpener can be used in the form of a mandrel. To prevent excess grass from wrapping around the shaft and damaging it, you can cover it with a tin can.
If the required pulley or other suitable parts are not available, then you will have to order the creation of the part from a turner or make it yourself from a pipe of the required diameter and circles and strips welded to it. In this case, there are three difficulties: finding a pipe of suitable length, ensuring the perpendicularity of the welded strip or circle to the pipe, and centering the mandrel after creation. With some effort, all difficulties can be easily solved.
Required components
The simplest version of a lawn mower includes the following parts:
- knives;
- engine;
- wheels;
- handles for controlling the structure;
- protective casing;
- a frame on which all mower components will be attached;
- parts for controlling the system: RCD, switch, cable and plug for connecting electricity.
The frame of the lightest model will include a metal sheet with a thickness of 2 to 3 millimeters with a hole in the middle for the passage of the motor shaft. The sheet is combined with a frame made of metal corners. The engine is attached to the sheet on top, a casing with protection is installed on the bottom, wheels are mounted on the sides of the axle, as well as handles for controlling the device.
If the product uses a flanged motor, then it can be attached to the sheet itself by drilling holes in the latter that will be identical to the holes in the flange. If the engine is of a classic type, then several perpendicular racks from the corner must be welded or screwed to the sheet so that they coincide with the engine feet.
Special holes are made in the corners for mounting the engine. If the holes are created as grooves, this will help align the engine with the frame when mounting. This assembly will be very useful for selecting the optimal grass cutting height. The easiest way would be to create holes for different engine heights.
The central place of the lawn mower will be a unit, which will consist of a mandrel with short knives attached to its surface (one long blade can also be used).
Gasoline equipment
A homemade device based on a gasoline saw is an excellent solution that allows you to save money. Assembly requires a frame, motor and fuel tank. The power ratings of such equipment make it possible to mow dense and large grass. The blades can be replaced with a petrol saw sprocket.
Do not forget that you need to use a gasoline-type lawn mower very carefully, observing all safety requirements, since gasoline is a flammable substance.
Useful tips
To obtain the most ideal mowing results with a mechanical lawn mower, you should adhere to the following recommendations:
- When mowing the lawn, do not move too slowly, otherwise the grass will get stuck in the drum, preventing the mower from working properly. Try to walk with an even and confident step, as shown in the video;
- It is best to cut the lawn with an overlap. This will allow you to smooth out any bumps that you missed the first time and it will be easier to move the device;
- Don't be afraid to change directions of the mower. Sometimes moving the lawn mower in the other direction can give you great results;
- Try to ensure that the lawn does not become overgrown. Tall grass will make it difficult to move the mower around the area. Trimming every week is considered optimal;
- Experiment with cutting height. This will allow you to understand how it will be easier to mow and determine in which case the lawn looks neater;
- The main thing is not to be afraid to make mistakes, grass tends to grow back. Don't worry if you miss a couple of plants, you can do it right next time.
