How to make a mower from a grass trimmer

How to make a grass trimmer with your own hands. About Metal

Under the trimmer is assumed trimmers or electric mowers.

Practically it is one of the varieties of lawn mowers (hand mower), which are created for mowing grass. This is a modern grass trimmer.

Originally they were developed for agricultural work, but the main use of trimmers has been specifically mowing lawns.

The idea of making a weed trimmer first occurred to a South American businessman, J. D. G. Bollasu. Driving a car through an automatic car wash, he saw that the principle of spinning brushes can be used to mow crops.

Then he assembled a simple grass trimmer out of a can (as a spool) and a fishing line threaded through holes drilled in it. He mounted the obtained construction on a pole, to which a moped engine had been previously mounted. It was not only for mowing wheat, but also for cutting grass.

Realizing that the sale of the weed whacker, he will earn huge money, the businessman improved his product and gave him the title “Destroyer weeds. The feature of the invention was the ability to cut the grass around the trees. the scaffold cut the grass perfectly, but did not traumatize the bark.

The main purpose of such a tool was to mow grass in small areas in places where traditional wheeled machinery can not be applied:

• in the presence of a large number of bushes;
• in gardens with a huge number of trees;
• near fences and hedges;
• If the site has an uneven topography.

All grass trimmers have a boom in its own composition. the main structural element.

petrol or electronic engine is attached to the boom at the 1st end, and the spool of fishing line, the main working element, is attached to the other end.

With all this, the type of transmission can be at least any. limited only by the ability of the manufacturer and commercial parameters.

Grass trimmer and lawnmower: advantages and disadvantages

To objectively evaluate both tools, it is necessary to disassemble the principle of their operation and methodology of application, then determine the advantages and disadvantages of each device.

The lawnmower acts like a ratchet mower, the wheels roll on the ground and the blade is always at the same distance from the ground, so the height of the grass after mowing is the same everywhere.

Thanks to the wheels, which take the weight of the motor, the operator only needs to push the machine in the right direction, which requires much less effort than holding even a light grass trimmer by weight.

trimmer for the grass can cut the grass close to trees or other obstacles, and effectively cope with high vegetation, which, because of the design inaccessible to most lawnmowers.

In addition, this tool is effective in uneven areas, because the operator to change the height of mowing, just change the angle of the boom, which can be done directly during the mowing.

However, this is also a serious disadvantage, because if you choose the wrong height of mowing, the cutting tool can hit the ground. If the grass trimmer is equipped with a fishing line, there won’t be any trouble, but if it is with a knife or a disk, then at best you will have to sharpen them anew, and at worst you will have to change.

How to make a garden shredder for grass and twigs with their own hands from a washing machine, grass trimmer, angle grinder

Garden shredder. a mechanism designed for processing plant waste generated during mowing grass cover, sanitary or annual pruning of trees, grapes and various shrubs. The resulting small pieces of grass or twigs can be used as livestock feed or fertilizer. The use of this unit allows gardeners, dacha owners and lovers of beautiful lawns to get rid of organic debris faster and with less labor. The device is relatively simple, for this reason it can be assembled with your own hands without much financial cost from old parts and improvised materials. This allows you to save on the purchase of a prefabricated factory device.

The main units of the garden shredder

To independently assemble a grass and twigs shredder (shredder) in the home, you need to first understand the device of the mechanism, as well as the principle of its operation. This will help properly assemble the equipment and, if necessary, to make changes to its design.

Homemade unit, designed for shredding grass clippings and cut branches up to several centimeters thick, has the following main structural units:

• engine;
• blades mounted on the work shaft;
• frame (usually metal);
• protective cover;
• a box designed to receive the cut vegetation
• starting system.

The technique itself can be made in a stationary or mobile form. To create the latter version will additionally require wheels, as well as a handle. To make the frame, metal corners or prefabricated frames from workbenches are used. The boxes for the recycled material are made of plastic buckets, tin sheets, bags. protective cover around the knives must be thick and strong enough not to quickly wear out from the exposure to the milled vegetation.

When recycling plant debris from the hole through which it is fed, chopped pieces may fly out. Therefore, the neck is covered with a lid or just a cloth, such as a bag.

The chopper works by transmitting the rotation from the motor shaft directly to the blades or through a chain/ belt transmission. Chopped vegetation with blades goes to the box. The end product is immediately ready for use.

On the principle of action some homemade shredders are comparable to the meat grinder (retract and then grind organics), and others with a coffee grinder.

Varieties of engines for assembling homemade models

Electric and gasoline engines, taken from unused equipment, are used as a drive for self-made machines. Each of these two options has its advantages and disadvantages. Models with a combustion engine are more convenient because their operation does not require a power grid nearby. But in general they cost more and have a more complex structure than their counterparts equipped with an electric motor. Therefore, it is easier to make an electric technique, in addition to more compact.

The maximum thickness of cut twigs, which can grind twigs shredder, depends on the capacity of the electric motor installed on it and the characteristics of the knives.

• Models with a motor up to 1.5 kW capacity are able to grind sticks up to 20 mm in diameter. They are designed for low-intensity work.
• If an electric motor from 3 to 4 kW is installed, then such units can shred branches already up to 40 mm thick.
• powerful electric motors (over 4 kW) are used to make shredders for wood with a diameter of 7-15 cm.

The last category drive is equipped with machinery if you need to constantly perform large volumes of work associated with the processing of waste of varying thickness.

To create a homemade shredder, you can use electric motors from an angle grinder, washing machine, grass trimmer. They must be adapted to work from a fixed 220 V mains supply. To shred the maximum thickness of the material at home, it is recommended to equip the shredder with an electric motor for 1500 rpm of about 3.5 kW. This parameter in internal combustion engines corresponds to 5-6 horsepower.

Types of cutting attachments used

Self-made, as well as factory units, are equipped with cutting nozzles of different types:

The first type is made of flat blades. They grind plant debris as they rotate. If you have to process branches, these blades dull quickly. Cutter knives are gear-type cutter shafts of circular saws. They are good for grinding dry waste from branches and grass, and wet ones clog the cutters. Milling-turbine cutting attachments can handle thick and not dried branches, but it is difficult to make them yourself.

At home, blades from lawnmowers or those made from wood saws are often used.

It should be borne in mind that the degree of processing of plant waste directly depends on the installed cutting nozzles. The output are either pieces of branch up to 10 cm in length or shavings, chaff.

Garden shredder from a washing machine

An old Soviet-made washing machine with a metal body is a technique that contains almost all the necessary parts for assembling a garden shredder. Only blades with fasteners will be needed, as well as a wire for an extension cord.

To make a cutting head, you can use an old wood saw.

• angle grinder;
• pliers;
• wrenches;
• screwdriver;
• power drill;
• hammer;
• tape measure with a marker.

The motor of the washing machine has a small power (different models have different power), indicated in the instructions to the household appliances or on the plate of the electric motor. Due to the fact that usually its value does not exceed 500 watts, with the help of the created unit it will be possible to grind only straw or grass.

How to make a rotary mower: step by step instructions

Homemade haymowers have recently become very popular.

If you have the desire and time, you can make a good machine yourself. Here are the instructions for constructing a rotary haymower.

The necessary material and tools

Before you begin making a lawn mower, you need to prepare the following materials and parts of the future device:

• disk from a grain planter. 2 pcs;
• chain from chain-saw reducer. 1 pc;
• knives made of hardened metal. 8 pcs;
• bar;
• coulter.

• electric screwdriver;
• pliers;
• nuts;
• carbide drill bits;
• drill.

Do you know? Because of its design the Horse-drawn Mower is popularly known as the “horse-drawn mower”.

Process Description

The first thing to do is to drill a hole in the discs with a 6 mm carbide drill bit. Then you need to attach the bar to the opener, and the knives to the bar.

Note that the distance between the bar and the knife should be a few mm more than the thickness of the knife. This moment is very important and necessary to ensure that with the help of centrifugal force blades spread from the disc, which would provide the main function. to mow the grass

360° rotation of the knives is a must. This prevents it from being damaged by stones or hard objects.

To make the axes of the blade mount, you will need carbon steel, which must be at least 8 mm in diameter. It is necessary to tighten the axle to the stop using a disc.

There will be no difficulties with the assembly of a rotary mower, if you clearly adhere to the recommendations.

Let’s make a reliable mower with their own hands

Motivation to create a tool from improvised materials

Choose how to drive the cutters. the basis for assembling the necessary assemblies. The blades can be set in motion:

• Due to manual action, pushing the mechanism forward, which requires a lot of physical strength;
• Using electric power of single-phase or three-phase current;
• battery-powered motor;
• using an internal combustion engine, two or four-stroke.

Determined with the energy component, you will need to choose the wheels, handle, platform to collect the lawnmower with their own hands. Assemble the necessary fasteners and components for connection, protection and connection diagrams.

Principles of using electric motors

The electric motor can be single-phase, operating from 220 V mains, or three-phase. When connecting the motor, all safety rules for working with electrical appliances must be observed. Must be made RCD protection for a single-phase electric motor, and a powerful three-phase have in the circuit capacitors, the appropriate capacity.

For an electric lawnmower with his own hands can use a powerful slow-speed drill with a speed of 1500-3000 rpm. It is necessary to choose the right ratio of power to the width of the swath, so as not to overload the motor. Mounted on the platform, cordless or cordless drill will create the necessary torque, and the grass will be mowed. During operation, do not forget to observe rest intervals, to cool the brush motor. This tool will help to clean the yard, easy to fold and does not require much storage space. The platform, on which the engine is installed, should be narrow, so it would be possible to process the walled area. Stability depends on the center of gravity. The lower it is, the lower the tilting moment of the platform. How to properly cost a lawnmower with their own hands, look

When building a tool yourself, remember that it is a means of increased danger. The circuit must be equipped with a locking button in case of jamming or a broken blade. Electric mowers must not be operated in damp weather, in the morning dew.

complicated models with a motor rated from 1.5 to 6 kW are installed on a specially made sole. It is better to use an asynchronous motor, it is less noisy. The running gear is represented by metal rubberized wheels with a wide tread, so that the grass is less crumpled. Bearing assemblies in sleeves on the axle are more reliable than plastic inserts.

You can make a deck and knife using an old frying pan and a plate made of tool steel. The design, when the knives are attached to the mandrel, is more effective. It is important to observe the proportions and profile of the sharpened edges, using the drawings in the photo lawnmower with their own hands.

Correct alignment is important for the performance of a fast travel unit. A slight wobble can create strong vibrations, destroy joints, and create play through worn seating.

The household is always accumulating end-of-life mechanisms and parts. Something can be found in household junk yards. Unfortunately, such cemeteries surround any residential area. Cradle wheels are great, and a handle from a baby stroller is also helpful. Voy example of a lawn mower with their own hands from a Soviet-era washing machine. They were then made of hard metal. Motors from these machines are the best in terms of parameters and power suitable for use in a lawnmower.

The high-quality steel housing serves as a protective skirt and guide when the grass is thrown sideways. In addition to the motor, two pulleys and a belt are used to transfer the rotation from the motor to the blade drive. The motor is fixed on the platform and connected to a single phase.

Such a home-made mower works in the yard, as it is tied to the mains with a power cord. You can use a special spool extension wire, selecting the cross section corresponding to the power of the motor. Such a device is available in a length of at least 40 meters and must ensure mobility.

Using a chainsaw motor in a lawn mower requires no additional protection. It is already made in a dustproof version. Air filters are clogged less often.

How to make a mobile lawnmower with their own hands? Made on the basis of a drill tool depends on the battery capacity and requires recharging in the network. In the absence of electricity, it remains to build a lawn mower based on the internal combustion engine. All small equipment that is fueled by gasoline or fuel mixture can become a donor for a homemade machine for mowing the lawn.

You have an old Druzhba or Ural chainsaw?

Here is an example of people’s ingenuity. A beautiful frame made of angle iron is discarded as scrap metal in the warehouse. Special wheel assemblies with 180 0 rotation on the pivot were found there. Without such a frame, the platform could be welded. The outriggered work unit is made with an independent drive from the chainsaw by means of a belt drive. Torque is transmitted to the discs, where the cutting tools are 25 cm long metal chains. Lawnmower from a chainsaw with their own hands is effectively used for several years. Made an improved version with a rotary cutter and a two-wheeled frame. It is more productive, but difficult to make.

Every craftsman is proud of his ingenuity and performance of the tool. However, it should be understood that the collective mind of designers, designers create no less functional, but safer tools.

The advantages of homemade tools include:

• Saving money on the purchase of the tool;
• opportunity to use parts that have lost their marketable value, but are usable;
• A thorough knowledge of your tool and the ability to improve and repair it.

Lawn mower and trimmer oils

Lawn mower and trimmer oils: what oil to choose and how to change the oil

In recent years, there has been no small increase in the construction of suburban housing. Residents of megacities are actively seeking to change the asphalt paths of the cities on a smooth beautiful lawn of their suburban area. But in order to create a beautiful, even lawn, you need to do a little bit of work. Prepare the soil, level it, plant lawn grass seeds, water them. Now we just have to wait for the green lawn to sprout and sprout. But this is not the end of the process, the next step will stretch over the entire summer season, it’s lawn care. To keep the lawn in shape you need to mow it.

Even if your plot does not have such a prepared lawn, and just grows grass, you can not get rid of the periodic mowing. After all, if you do not do this site can quickly become impassable thickets. Therefore, almost every owner of a garden plot can not do without modern equipment, which greatly facilitates the maintenance and care of the site and the surrounding area.

Mowing the grass or cutting the lawn without a brushcutter or lawn mower can take an entire day, and I doubt that anyone would happily sacrifice a day off for such an activity. On the other hand, the availability of small tools significantly reduces the time spent on mowing, and in some cases brings even pleasure as from the process itself and from its result.

The devices for grass mowing with internal combustion engines are now presented in a huge quantity and in any configuration. Such machinery is equipped with 2- or 4-stroke engines, depending on the purpose. And the key to long trouble-free service, just timely maintenance and use of quality lubricants.

The role and function of the oil in the engine of lawn mowers and grass trimmers It should be noted at once that the engines installed on grass mowers, grass trimmers and lawn mowers have serious differences from automobile and motorcycle engines. Engine design, in order to reduce production cost and simplify maintenance, has no oil pump, which increases the requirements to the engine oil, especially its viscosity.

Engine oil is distributed in the lawnmower engine by means of a crankshaft. Oil is scooped out of the crankcase, roughly speaking, with “special spoons” and sprayed on parts. And now imagine the speed of such “spoons. makes a great mixer! That is why one of the most important components of lawnmower oil is the presence of quality “antifoam” additives. Cheaper varieties of oils for garden equipment, as well as oils for cars, have much less of such additives in their composition. Therefore, it is important to use only high quality oils intended for garden equipment. This lubrication system means that the oil’s viscosity must retain its ability to hold on to the parts, while at the same time not hindering the movement of the engine parts.

In addition to their maximum lubricating properties, oils used in machinery for “mowing” should perform a number of other useful functions:

Divert heat from heated engine parts

Minimize deposits, fouling, varnish

Comply with modern environmental requirements

Help reduce the toxicity of exhaust gases

To work with minimum smoke formation

Conform to your equipment manufacturer’s requirements

Even assuming that the design of the lawnmower engine is simple enough, the set of requirements and properties of engine oil is quite impressive. Therefore, the choice of lubricant should be approached responsibly.

In the winter period lawnmowers no one uses, the technique gets rid of “cold start” at subzero temperatures, which certainly would affect the life of the engine. But in the summer period need to monitor that the technique is not overheated, as have air-cooled engine, and therefore the temperature of their engines is higher than that of liquid-cooled engines. The difference between 2T oils for lawnmowers and trimmers and 4T oils Despite the fact that 2 and 4-stroke oils have the same job, the oils used differ. The difference in oil is due to the different operation of these motors. In 2-stroke engines, the lubrication is done with oil premixed with fuel, as a result the oil burns together with the fuel. There are variations of 2-stroke engines, where oil and fuel are fed into the combustion chamber from separate containers, but the result is not changed and the oil mixed with fuel burns in the chamber together with gasoline. In 4-stroke engines, in contrast, the task of the oil is not to get into the combustion chamber.

Grass trimmers and brushcutters belong to hand tools, and imply a compact design for easy handling. The design of 2-stroke trimmers and brushcutters in most cases is equipped with a single reservoir for filling the ready-to-use fuel-oil mixture. less often, when there are variants with separate tanks for oil and gasoline. The main differences in oil requirements stem from these engine operating conditions. Oils for 2-stroke engines should burn as much as possible and in the process of combustion minimize traces of soot in the form of ash and carbon black. Oils for 4-stroke engines are aimed at stable lubrication, for a long time, preserving its properties.

Briefly about API and the rest The main factors, characterizing modern motor oils “on the global level”, are considered to be effective fuel economy, long drain intervals and low level of hazardous substances emission (low smoke and toxicity of exhaust gases). These are general requirements for oils, API defines more specific. The higher the grade of the engine oil, the more it meets the basic factors, i.e.е. it has a higher quality level and is naturally more expensive. API SM and API SN are considered to be state-of-the-art oils. If an oil is double-designated as API SL/CF, you are looking at a multi-purpose oil, suitable for both gasoline and diesel engines.

2-stroke motor oils (ground machinery) have their own classification system. It is customary to divide them into groups depending on the severity of work (thermal and dynamic loads are taken into account). TA, TV, TS, TD. The highest requirements are for AP TD oils. Surprisingly, but the fact: the chain saw engine is not inferior to the motorcycle engine in terms of tension, and the oils for them should correspond to the category of not less than TC.

The process of making a homemade scooter based on the engine from a brushcutter

On the hub of one wheel we will weld a plate, having previously enlarged the central hole and drilled the side ones according to the template. We will attach a big gear wheel to it later.

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Bolt the brake disc to the other side of the hub using the elongated nuts and screw them to the disc first.

In the large cogwheel, drill around the center hole 5 holes equidistant from the center.

Assemble the frame by welding from round tubes and plates, consisting of longitudinal and transverse elements.

Assemble the fork for the front wheel out of round and square tubes, with hole plates and reinforced supports welded on the ends.

We cut off the “horns” from the old bicycle fork and weld the steering tube with the fork crown in the center of the cross section of the homemade fork out of the shaped tube.

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We weld a bicycle steering column to the notches of the profile tube, cut at the calculated angle. Install swivel wheel to fork with axle and nuts. The other end of the shaped tube is welded to the frame cross members made of round tubes.

handlebar, handlebar stem and steering tube extension are welded from a tube of the appropriate diameter. Steering column of the front wheel fork is installed in the steering tube and secured with nuts. We connect the handlebar extension to the steering column.

Replace the old shaft on the brushcutter engine with the new one. Using two shaped plates with holes bolted to the motor housing, attach it to the rigid base plate by welding.

Cut off a short piece of the rigid shaft extension with splines and insert it into the splines of the motor shaft. Then put the small sprocket on it and weld it to the spline piece, observing the position of the large sprocket attached to the hub flange of the rear wheel.

Insert the other end in the bearing pressed into the ring welded to the vertical plate, which is welded to the base. But before that you need to put the drive chain on the sprockets.

Put the motor with the base in front of the rear wheel a bit to the right and weld it to the frame longitudinal members. To stiffen the frame and mount the pad, we weld two more plates transversely.

From the side of the brake disk we screw the brake mechanism to a vertical plate welded to the frame.

Paint the frame and rivet the pad to its elements.

Connect the corresponding handles on the handlebar with cables to the motor and brakes. Our scooter based on the motor from a brushcutter is ready to move.

The process of making a homemade scooter based on the motor from a brushcutter

On the hub of one wheel we will weld a plate, having previously enlarged the central hole and drilled the sides according to the stencil. We’ll mount the big cogwheel to it later on.

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We weld the brake disk to the other side of the hub using the elongated nuts, having previously screwed them on to the disk.

Drill five holes equidistant from the center hole in the large cogwheel.

Assemble frame by welding from round tubes and plates, consisting of longitudinal and transverse elements.

Also out of the profile and round pipes with welded on the ends of the plates with holes and reinforced stanchions assemble fork for the front wheel.

We cut off “horns” from the old bicycle forks and weld the steering tube with the fork crown in the center of the cross section of the fork out of the profile tube.

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Welded to the notches of the profile tube, cut at the calculated angle, a bicycle steering column. Fit the swivel wheel to the fork with the axle and nuts. The other end of the profile tube is welded to the crossbars of the round tube frame.

Rudder, handlebar stem and steering tube extension are welded from the pipe of the corresponding diameter. Install the front wheel fork steering tube in the steering tube and fasten it with nuts. Connect the handlebar extension to the steering column.

Replace the old shaft on the brushcutter engine with the new one. Using two through-hole plates bolted to the engine housing, mount it to the rigid base plate by welding.

Cut off a short length from the stiff shaft extension and insert it in the splines of the motor shaft. Then put the small sprocket on it and weld it to the section with splines taking into account the location of the large sprocket attached to the hub flange of the rear wheel.

insert the other end of the piece into the bearing pressed into the ring welded to the vertical plate, which in turn is welded to the base. But before that you need to put the drive chain on the sprockets.

mount the engine with the base a little to the right in front of the rear wheel and weld it to the longitudinal frame members. To give stiffness to the frame and mount the plate, two more plates are welded crosswise.

Bolt the brake mechanism to the vertical plate welded to the frame on the brake disk side.

We paint the frame and rivet the plate to its elements.

Connect the appropriate handles on the handlebars with cables to the motor and brakes. Our self-made scooter based on the engine from a brushcutter is ready to move.

Workflow:

First make the base of the scooter. For this purpose from a metal plate with an angle grinder cut a square with a side of 100 mm. Mark it so that exactly in the center (at the intersection of the diagonals) was a hole. To do this, measure off a distance of 50 mm from the center of the chosen hole, perpendicular to the short side of the plate, and mark the cutting lines.

We trim off the excess and get a square of 100mm x 100mm. Now it is necessary to round the corners a little and drill a central hole for the grass trimmer shaft.

Round the corners and drill the center hole for the grass trimmer shaft

Cut blades on metal, measuring 8 cm from each end. We have 4 blanks with the prepared holes.

These blanks need to be shaped into knives. To do this, we mark the line for the trimmer cut by eye (special accuracy is not required), fasten all 4 blanks together and grind off the excess.

As a result, we get blades of equal weight and size, and it is possible to sharpen them a little on one side. All parts of the home-made grass trimmer shaft are now ready, and you can begin to assemble.

Put a small washer on the screw and put it into the hole in the corner. Put the blade on top, placing the sharpened side in the direction of rotation of the grass trimmer shaft. Then come the large washer and the nut, which is not tightened so that the blade can turn freely. Fix other 3 knives in the same way.

The end of the screw must be riveted, so that the nut doesn’t fly off.

The accessory is ready. It is mounted with nuts to the ground and fastened in the same way as the three-blade blade that comes with the trimmer. When hitting a stone the blades are folded and go inside a little.

This idea was suggested by our regular video author Tatiana (Tula region). To see in more detail the whole process of making such a nozzle for the grass trimmer and learn some of the nuances, you can watch the video, which she prepared.

When working with a trimmer, it is important not to forget about safety when using any attachments, especially homemade.

We suggest to discuss this idea in the Комментарии и мнения владельцев to the publication. Share with us your thoughts, as well as tell us about your oudachnyh solutions.

Without taking either side of this heated (literally and figuratively) discussion, let me show you one of the latest models of brushcutters from the German company Robert Bosch. There is also a swivel blade and an arc-shaped bracket, which prevents the blade from “scraping” against any objects not intended for mowing. Showing the general view of the brushcutter and the knife itself, in two positions. General view of the brushcutter

Knife in deflected state

Knife in folded state

Good evening, everyone! Exactly three years have passed since the discussion of the “acute” problem for the grass trimmer. In the past 1000 days a clear picture emerges: “Glory to the author. a craftsman, who is conducting an experiment on himself to achieve the limit of fluidity of the metal from which these knives are made. He has every right to risk his own health. Nowadays in stunt movies one can often see the phrase: “Don’t try to repeat movie stunts performed by professional stuntmen”.”The very first article should have ended with a phrase like this:” Dear gardeners. This is my personal experiment. If you are not confident in your locksmith skills, please do not repeat it. And MOST IMPORTANTLY. I am not responsible for the operation of a tool made in the footsteps of my article.”And lastly. Do I see the mistakes, judging from the photos, of the performance of this tool. Yes, I see it, and a rough one at that. Look carefully at the plate, which is bearing for four knives. Look carefully at the FAREST RIGHT HOLE in the picture.

Alas, the author of this apparatus has no idea how the shaft hole should be made.

I report. the distance from the point closest to the edge of the plate to the edge of the hole must be NO LESS than the diameter of the hole itself. This truth students of mechanics learn no later than the second year of the institute. And what do we see here?? A thin isthmus resembling a narrow Isthmus making a peninsula out of the Crimea. This is a priori the place which is weak in this construction. it experiences the same loads as the other knives, but the “perekope” is quite thin there. Where it is thin, there it is I would like to hope, quite sincerely, that during these three years this crosspiece has not undergone loads comparable to the yield strength of this metal, but rather of the alloy, from which the perforated plate is pressed.