Removing heavy loads types of chain hoist for a lift. The simplest mechanisms for lifting loads

The chain hoist is a lifting structure that was invented back in the days of the great thinker Archimedes. Now it is impossible to establish exactly who this genius was, but the already mentioned philosopher also put his hand to the development of this construction. Otherwise, it is also called the system of blocks, because of the main purpose and the counterweights available at that time, in the form of limestone blocks.

Blocks and chain hoists, the purpose and arrangement of which now for an ordinary person who is accustomed to high technology, looks rather primitive. But it is worth considering the fact that it was thanks to this mechanism that great historical buildings were built, such as the pyramids, the Pantheon, the Colosseum and the like. But the technology did not remain on the pages of textbooks, but continued its development, adapting to emerging technology and the needs of people.

Description and arrangement of chain hoists

The design itself is a device for lifting loads using special connection blocks and ropes between them. Using the lever rule and the force of friction, the structure comes into action increasing the force or speed of lifting an object. There are different types of chain hoists, which differ in the number of blocks, cable connections, load capacity and other configurations.

The system, in turn, consists of movable and fixed elements, along which ropes are drawn, creating tension and ensuring the transportation of cargo. The fixed element is the main structure that is attached to the vehicle or static bar, and the movable element is attached to the load. Therefore, the first must be able to withstand a lot of pressure, and the second to evenly distribute it.

The lower or movable block is usually equipped with a special mount, in the form of a hook, a powerful magnet, a carabiner, and so on. The upper block has special rollers along which the rope is carried and the pressure exerted on each rope individually depends on the number of rollers. And this means that the appropriate number of rollers and working branches are required to lift large heavy loads.

The video tells and demonstrates how the chain hoist works, and also reveals its advantages

Purpose

Given the fact that this invention is more than two thousand years old, it has been used to perform an unimaginable amount of work and tasks. Often this is the construction industry, where chain hoists are used in cranes, winches and the like. Also, the mechanism was used on ships, for lowering and raising lifeboats. It was used for some time in the first prototypes of the elevator, before the advent of hydraulic and electric drives.

Pulleys, purpose and device, their multiplicity changed and found application in sports, namely, in rock climbing and other extreme activities at high altitudes. Also, for a long time, rescue teams in mountainous areas were equipped with devices to pull victims out of hard-to-reach places. You can often find the use of blocks in electrical wiring, or rather, to create tension in the cable network.

Varieties of chain hoists

All pulley blocks can be divided into two categories:

• power;

• high-speed.

Based on the name, the purpose of each species is determined and based. The first is the most common and is used to lift loads, exactly as it was invented. The high-speed option is a modified design, where great efforts are directed to increase the speed of transportation. According to this principle, cable cars are created at ski resorts.

In addition, the difference lies in the number of rollers and working branches, as well as other modifications. An electric drive and a stopper can be connected to the structure. Another difference lies in the material of the rope, because it can be represented as:

• ropes;

• metal rope;

• iron chain;

• electric cable.

In construction engineering, the second option is most often used, due to the strength of the material. Rope ropes are used most often in tourism, rescue operations and so on. The use of an iron chain can be found very rarely, these are narrowly focused varieties for certain jobs.

lift with at home

Sometimes in everyday life there is a need to lift a heavy load, but not all people have the opportunity to fit a construction crane to the threshold, from which they have to get out. And here the system of blocks can just come to the rescue. Polyspasts, the purpose and arrangement of which may seem rather difficult to design, but with proper preparation, creating such a design at home will not be a problem. Everything is done in four stages:

• Calculations. They are made taking into account your goals and objectives, namely, the parameters of the working room, the presence of restrictions in it, the weight of the cargo and the distance over which you need to transport. It is necessary to fix all these data for drawing up a drawing and choosing a design.

• Creating a drawing. If there is no experience in this matter, then it is better to turn to a person with experience and engineering education, who can reduce the time to create a model on paper. If there is nowhere to get help, then it is better to turn to the Internet and see the working drawings of the basic structures. Each of the types will be effective in certain conditions, the measurements of which you will make earlier.

• Selection of materials. The selection should begin already at the first stages, namely, starting from the things you already have and those that can be purchased. It depends on your drawing and calculations what parts will be needed and what material is better to use. Buy according to your budget and with a reserve for further use. It’s not worth saving much, otherwise the design can fail at the most crucial moment.

• Design. This step is the easiest of all, because here you just need to follow the plan and do it right.

With a certain skill and preparedness, a very solid working model can be obtained, which will not be inferior to building counterparts. But if the tasks are not too ambitious, then this will not require strong costs. For reliability, you can use ready-made parts from construction chain hoists in the creation.

Conclusion

Pulley blocks are simple in design, but their purpose is important, because thanks to them it is possible to carry out the most complex lifting manipulations. Construction of buildings, installation of electric cable lines, installation of a funicular or rescue operation, in any of these situations, the system of blocks can guarantee the reliability of execution.

A person is not very strong for lifting large loads, but he came up with many mechanisms that simplify this process, and in this article we will discuss chain hoists: the purpose and arrangement of such systems, and also try to make the simplest version of such a device with our own hands.

The cargo chain hoist is a system consisting of ropes and blocks, thanks to which it is possible to gain in effective strength with a loss in length. The principle is pretty simple. In length, we lose exactly as much as how many times the gain turned out to be in strength. Thanks to this golden rule of mechanics, large masses can be made without much effort. Which, in principle, is not so critical. Let's take an example. Here you have won in strength 8 times, while you have to pull out a rope 8 meters long in order to raise an object to a height of 1 meter.

The use of such devices will cost you less than renting a crane, and besides, you can control the gain in strength yourself. The chain hoist has two different sides: one of them is fixed, which is mounted on a support, and the other is movable, which clings to the load itself. The gain in strength is due to the movable blocks that are mounted on the movable side of the chain hoist. The fixed part serves only to change the trajectory of the rope itself.

Types of chain hoists are distinguished by complexity, parity and multiplicity. In terms of complexity, there are simple and complex mechanisms, and the multiplicity means the multiplication of force, that is, if the multiplicity is equal to 4, then theoretically you will win 4 times in strength. Also rarely, but still, a high-speed chain hoist is used, this type gives a gain in the speed of movement of goods at a very low speed of the drive elements.

Let's start with a simple mounting chain hoist. It can be obtained by adding blocks to the support and load. To get an odd mechanism, it is necessary to fix the end of the rope on the moving point of the load, and to get an even one, we fasten the rope to a support. When adding a block, we get +2 to strength, and a moving point gives +1, respectively. For example, to get a chain hoist for a winch with a multiplicity of 2, you need to fix the end of the rope on a support and use one block that is attached to the load. And we will have an even type of fixture.

The principle of operation of a chain hoist with a multiplicity of 3 looks different. Here the end of the rope is attached to the load, and two rollers are used, one of them we attach to the support, and the other to the load. This type of mechanism gives a gain in strength of 3 times, this is an odd option. To understand what the gain in strength will be, you can use a simple rule: how many ropes come from the load, this is our gain in strength. Chain hoists are usually used with a hook, on which, in fact, the load is attached, it is a mistake to think that this is only a block and a rope.

Now we will find out how a complex type pulley block works. This name means a mechanism where several simple variants of a given cargo device are connected into one system, they pull each other. The gain in strength of such constructions is calculated by multiplying their multiplicities. For example, we pull one mechanism with a multiplicity of 4, and the other with a multiplicity of 2, then our theoretical gain in strength will be 8. All the above calculations take place only for ideal systems that have no friction force, but in practice things are different .

In each of the blocks, there is a small loss in power due to friction, since it is still spent just to overcome the friction force. In order to reduce friction, it must be remembered: the larger the bending radius of the rope, the less the friction force will be. It is best to use large radius rollers where possible. When using carbines, you should make a block of the same options, but rollers are much more effective than carbines, since we have a loss of 5-30% on them, but up to 50% on carbines. It is also useful to know that the most efficient block must be placed closer to the load for maximum effect.

How can we calculate the real gain in strength? To do this, we need to know the efficiency of the blocks used. Efficiency is expressed in numbers from 0 to 1, and if we use a rope of large diameter or too stiff, then the efficiency of the blocks will be much lower than indicated by the manufacturer. So, it is necessary to take this into account and adjust the efficiency of the blocks. To calculate the real gain in strength of a simple type of hoist, you need to calculate the load on each branch of the rope and add them up. To calculate the gain in strength of complex types, it is necessary to multiply the real strengths of the simple ones of which it consists.

Do not forget also about the friction of the rope, since its branches can twist among themselves, and the rollers from heavy loads can converge and pinch the rope. To prevent this from happening, you should space the blocks relative to each other, for example, you can use a circuit board between them. You should also purchase only static ropes that do not stretch, as dynamic ones give a serious loss in strength. To collect the mechanism, both a separate rope and a cargo rope attached to the load, regardless of the lifting device, can be used.

The advantage of using a separate rope is that you can quickly assemble or prepare a lifting structure in advance. You can also use its entire length, this also makes it easier to pass knots. Of the minuses, we can mention that there is no possibility of automatic fixation of the lifted load. The advantages of a load rope are that the object being lifted can be auto-fixed and there is no need for a separate rope. Of the minuses, it is important that it is difficult to pass knots during operation, and you also have to spend a cargo rope on the mechanism itself.

Let's talk about the reverse move, which is inevitable, since it can occur when grabbing the rope, or at the time of removing the load, or when stopping for a rest. To prevent reverse movement, it is necessary to use blocks that allow the rope to pass only in one direction. At the same time, we organize the structure in such a way that the blocking roller is attached first from the object being lifted. Thanks to this, we not only avoid reverse movement, but also allow us to secure the load during unloading or simply rearranging the blocks.

If you use a separate rope, then the blocking roller is attached last from the load being lifted, while the fixing roller must be highly effective.

Now a little about attaching the lifting mechanism to the cargo rope. It is rare that we have the right length of rope on hand to secure the moving part of the block. Here are several types of mounting mechanism. The first method is with the help of grasping knots, which are knitted from cords with a diameter of 7-8 mm, in 3-5 turns. This method, as practice has shown, is the most effective, since the grasping knot of 8 mm cord on a rope with a diameter of 11 mm begins to slip only at a load of 10-13 kN. At the same time, at first it does not deform the rope, but after some time, it melts the braid and sticks to it, starting to play the role of a fuse.

Another way is to use a general purpose clamp. Time has shown that it can be used on icy and wet ropes. It starts to crawl only at a load of 6-7 kN and slightly injures the rope. Another way is to use a personal clamp, but this is not recommended, as it starts to crawl at a force of 4 kN and at the same time breaks the sheath, or can even bite the rope. These are all industrial designs and their application, but we will try to create a home-made chain hoist.

Homemade chain hoist

Polyspast is known to be a very useful thing. The principle of operation was studied at school. System of movable and non-movable blocks. We lose in distance, we win in strength. I decided to buy myself a farm. I bought it for 200 kg, Chinese, with a nylon rope. It turned out not quite what I expected - the ropes get confused, 200 kg is not enough. Decided to do it myself. At first I began to look on the Internet as other people do. But as it turned out, finding a normal example is not easy - basically the search pointed to shitty sites that steal text and pictures from each other.
I decided to deal with some subtleties of the design. What they conceived is being sold in the region of 60,000 thousand rubles. Too expensive for me. I decided to make a chain hoist with my own hands.
Here are the subtleties that you need to consider when making a chain hoist yourself:
Schematic first:

Now let's move on to the design of the chain hoist.
I planned to make a chain hoist of two blocks of three rollers each, approximately 6 tons.
Let's start with the load capacity, which depends on the thickness of the cable - here it's just the load capacity that depends on the thickness of the cable. Approximately and very roughly, you can divide the load capacity by the coefficient, the multiplier of the chain hoist planned by me, you can see in the above diagram. Let's say the required chain hoist is needed for 6 tons, then 6000 kg. divide by 6 and get exactly a ton for the cable. A 10 mm cable is suitable for a ton.
In stores, all winches, blocks using a steel cable are made completely wrong. The diameter of the roller must be selected taking into account the diameter of the steel cable and must be equal to at least 16 cable diameters, and preferably 24 diameters. In store crafts, this is not respected. The diameter of the roller pulley is catastrophically small, the diameter of the cable absolutely does not correspond to the permissible loads. The roller is at best on a single-row radial bearing or without a bearing at all, which is also not very good. The groove on the pulley is often too large. The material is generally made of the cheapest steel and does not have any margin of safety. Details of cheeks made of thin sheet steel. It comes to a ridiculous sale of a manual winch with a declared load capacity of 1.5 tons and a cable with a diameter of 3 mm.
But on the Internet you can easily find a table of the load capacity of steel cables

1 kN is approximately equal to 100 kg.
The groove on the pulley or roller should match the size of the cable and be slightly larger than the diameter of the cable. Roughly speaking, the size of the groove should be such that the cable does not flatten and at the same time is freely placed in the groove.
Taking the crane hoist as a prototype, I calculated everything, drew it and got the following design. Each pulley on two bearings according to the corresponding load, the axle is made of solid steel. There is another subtlety - the studs for laying the cable do not give the cable extra freedom. The number of block parts is surprisingly large for a simple chain hoist. Well, everything else I think will be clear from the photos.

The chain hoist turned out to be heavy but very easy to use.
The weight of one block is 15 kg. Cable with a diameter of 10 mm and a length of 30 m.

The ancient Egyptians and Archimedes, without wondering about the chain hoist - what it is, already used it to move heavy loads. It is still widely used in all lifting mechanisms, in sports, in everyday life, and is also used by rescuers. Since then, the scheme of this device has undergone significant changes, but the principle of operation has not changed.

In contact with

Device

A simple chain hoist consists of two pulleys connected by a rope, cable, chain. The pulley is made in the form of a metal wheel rotating on an axle. On the outer edge there is a groove for laying the cable. The pulleys that make up the structure are called blocks. Some of them are fixed, others change position as the cargo moves. Movable blocks are placed on the side of gravity. The fixed block changes the direction of movement of the cable and the force application vector, while the movable blocks increase the force applied to the load. The movement of the load occurs due to the fact that it is pulled through a system of blocks by a rope to the fixed part of the chain hoist.

In fact, the chain hoist is a system of levers, the role of which is played by the parts of the rope located between the blocks. As you know, the law of the lever says that, winning in strength, you lose in distance, and hence in speed, and vice versa. Means, to move cargo for 1 meter with a mechanism with a double win, you will have to choose 2 meters of rope, that is, spend 2 times more time. The applied force will be 2 times less than the mass of the load, however, the amount of energy expended will not change.

In the same way, the distance gain is calculated if the attachment points of the chain hoist and load are interchanged.

multiplicity

This is the main characteristic showing how many times the chain hoist theoretically increases the force or speed. The multiplicity value is determined by the number of cable branches between which the load is distributed and can be even or odd. In the first case, the free end of the cable is fixed on the fixed part of the lifting mechanism, and in the second case it is attached to the hook holder.

It may seem that by increasing the number of blocks, you can infinitely multiply the effort.

However, no one has canceled friction, which, even in the best models of pulleys, takes at least 10% of effort to overcome. That's why if you calculate the real gain taking into account friction for a chain hoist with a multiplicity of 5: 1 (5 * 0.9 * 0.9 * 0.9 * 0.9 \u003d 3.28), the result will be more modest. And if you use carbines instead of blocks (for example, in mountaineering), in which friction losses are much greater, the gain will be even more modest.

Classification

Polyspasts, the purpose and structure of which have not changed over the past centuries, can be power and high-speed. The former are used on lifting mechanisms, and the latter are equipped with lifts. By execution, they are made:

1. Simple circuits, consisting of a linear sequence of blocks. They are connected to each other and to the load by a common rope.
2. Complex. This is a system in which not separate blocks are connected in series, but several independent mechanisms. This solution allows you to create chain hoist circuits with a large multiplicity with a small number of blocks. For example, connecting pulley blocks with a multiplicity of 2:1 and 3:1 will give a gain of 6 times when using only three blocks. Due to lower friction losses, the real result will be higher than that of a simple design with similar parameters.
3. Complex chain hoists occupy a separate place. This is a chain hoist system of simple and complex mechanisms connected in such a way that the blocks move towards the load when they are lifted.

Polysplast looks like, photo

How to make a chain hoist yourself

In the household, there is no need to lift weights daily, so for one-time work, you can make a lifting device with your own hands. Everything you need for this can be found in the workshop of a thrifty owner:

• threaded steel studs;
• bearings;
• videos;
• rope;
• hook.

The bearing is inserted into the roller and mounted on the stud. They twist the nut and lock it so as not to waste effort on scrolling the resulting shaft. A hook is attached to the stud or slings. One end of the rope passed through the made block is fixed on a fixed support, and the other is pulled up when lifting the load. It turned out the simplest chain hoist with a multiplicity of 2: 1.

Since it is inconvenient to work with such a mechanism, one more block should be made and, having secured, pass the rope through it. Now it can be pulled down and even connected to a winch. In addition to improving working conditions, this will provide the possibility, if necessary, of fixing the load in any intermediate position.

For a do-it-yourself chain hoist, it is better to use a rope rather than a steel cable. Its advantage is that it allows quickly assemble or disassemble construction. Choose static views that do not stretch. Dynamic types "eat up" part of the gain in strength.

Lifting heavy loads to a height, even if not very high, is a very difficult task for a person. However, quite a lot of different mechanisms and devices have been invented to facilitate this process. The chain hoist should be included among such mechanisms without fail. In our article, we will talk in more detail about this device, and also talk about the technology for creating a chain hoist at home.

How to make lifting easier

The chain hoist is a system that consists of fixed and movable blocks connected to each other by chain or cable drives. This device was invented a long time ago, because even the ancient Greeks and Romans used similar mechanisms. Over the next millennia, the components of this apparatus and its purpose have not changed much. To date, this device is used almost in its original form, with only minor changes.

Scheme of operation of the chain hoist

Polyspasts are mainly used in boom mechanisms of building cranes. For chain hoists, despite all their diversity, there are two main requirements: an increase in speed (high-speed mechanisms are responsible for this) and an increase in strength (the so-called power chain hoists). Elevators usually use the former, while the latter have found use in cranes. It should be noted that the important fact is that the circuits of power and high-speed devices are almost completely mutually inverse.

A conventional chain hoist is a device, the main components of which are:

• system of blocks with movable axes;
• blocks with fixed axes;
• wrapping drums;
• bypass blocks.

Due to the effective interaction of blocks and ropes, it becomes possible to significantly gain in strength. In strength, we win as many times as we lose in length. This is one of the fundamental rules of mechanics, thanks to which an ordinary person can easily lift heavy masses with a minimum of physical effort.

It is much more profitable to purchase this device or make it yourself, rather than renting cranes or similar mechanisms. The peculiarity of the device is that one of the sides, which is fixed on the load, is in a movable state, while the second side, attached to the support, is static. It is the movable blocks that provide such a significant gain in strength. Static blocks are required to control the trajectory of the rope and the load itself.

There are various types of chain hoists, which differ in multiplicity, parity and complexity. The multiplicity indicator determines how many times you will gain in strength using this device. So, buying a mechanism with a multiplicity of 6, you theoretically have a gain in strength of 6 times.

Simple and complex chain hoists - we understand their design

First, let's talk about simple mechanisms. You can get such a device by adding blocks to the load and support. An even chain hoist is a device in which a rope is attached to a support. If an odd number is required, then the rope is installed on the moving point of the object being lifted. Adding a block increases the instrument's magnification by two points.

So, in order to manually make a chain hoist for a conventional winch, the multiplicity of which is 2, it is enough to use only one movable block attached to the load. The rope is attached to the support. As a result, we will have an even chain hoist with a multiplicity of 2. Complex chain hoists include several simple mechanisms. Naturally, such a device gives a significantly greater gain in strength, which can be calculated by multiplying the multiplicity of each of the chain hoists used. At the same time, one should not forget about the friction force, due to which there is a small loss in the power of the device.

There are several ways to reduce the friction force of a rope. The most effective is to use rollers with as large a radius as possible. After all, the larger the radius, the less friction force has on the rope and the lifting mechanism as a whole.

How rope affects work efficiency

You can avoid pinching and twisting the rope if you use additional devices, for example, mounting plates, which allow you to spread the rollers relative to each other. We strongly do not recommend the use of stretchable ropes in chain hoists, since, in comparison with conventional static products, they lose very seriously in efficiency. When assembling a block for lifting loads, specialists use both a load and a separate rope, which are attached to the object independently of the lifting device.

The operation of individual ropes offers some advantage. The bottom line is that a separate rope provides an opportunity to pre-assemble or pre-assemble the entire structure. In addition, the passage of knots can be greatly facilitated, since the entire length of the rope is used. The only drawback is the inability to fix the load in automatic mode. Cargo ropes, on the other hand, can boast of just such a feature, so if it becomes necessary to auto-fix the load, use the cargo rope.

The reverse is important. This effect is inevitable, since at the moment of removal, as well as when intercepting the rope or stopping for a rest, the load will certainly move in the opposite direction. The quality of the blocks used, as well as the entire device as a whole, determines how much the load will go back. You can prevent this phenomenon from occurring if you purchase special rollers that allow the rope to pass in only one direction.

Let's talk a little about how to properly attach the cargo rope to the lifting mechanism. Far from always, even the most prudent master has a rope of the required length, which is required to fasten the dynamic part of the block. Therefore, several methods of fastening the mechanism have been developed:

• With gripping knots. These knots are tied in five turns from cords, the cross section of which does not exceed 8 mm. The use of such nodes is the most effective and, accordingly, common. According to experts, the knots are very strong and reliable. Only a load of more than 13 kN can lead to slipping of such a node. The important thing is that even when slipping, the knot does not deform the rope in any way, leaving it safe and sound.
• The use of general purpose clamps. These devices can be used even in difficult climatic conditions, for example, on wet or icy ropes. A load of 7 kN can cause the clamp to slip, resulting in damage to the rope, although not very severe.
• Personal clips. They are used only for small jobs, since a load of more than 4 kN causes the clamp to slip and subsequently break the rope.

Reservation - we study the most popular schemes

This technological operation is intended to change the distance between the blocks, as well as to change the position of these blocks. The need for reeving is due to a change in the height or speed of lifting objects by setting a specific scheme for the passage of the rope through the blocks and rollers of the mechanism.

The scheme used depends largely on the type of lifting device. Reserving for winches is carried out only for the purpose of changing the length of the boom. It is performed by changing the relative position of the guide blocks. Very often, such an operation is carried out in cargo cranes, where it is required to prevent such an effect as the curvilinearity of the movement of weights.

Stocks, depending on the schemes used, are divided into the following categories:

• Single. This type has found application in shooting type cranes, where the hook must be brought on one rope rope. After that, it is required to sequentially carry out static blocks. In the final stage, the hook is wound on the drum. As practice shows, this type of reeving is the most inefficient.
• Double. This type is used in cranes that are equipped with a beam and a lifting boom. In this case, it is required to install fixed blocks on the boom head, while the other end of the rope is attached to the cargo winch.
• Quadruple. It is in demand among chain hoists, which are used to lift objects of huge mass. Usually, one of the reeving schemes that were described earlier is used, with the only difference being that they are used separately for each hook block.

We make a chain hoist from paper cups and gears

The devices used in construction are very complex, which is logical, because here you need to lift large loads to a sufficiently high height. Understanding their design features can be very problematic. What can not be said about home chain hoists, which are used in everyday life. They are so simple and understandable that anyone can build a chain hoist with their own hands. To do this, we need the following devices:

1. 1. several glasses of paper;
2. 2. scissors;
3. 3. lace or strong thread acting as a rope;
4. 4. plasticine;
5. 5. plastic hangers.

First of all, you need to make a basket in which the cargo will move. For these purposes, we will use paper cups through which we thread the rope. We collect the pulley block from hangers. We fix the rope or thread on the top of the hanger, after which we wind it around the crossbar several times. The basket obtained from the glasses should be hung on the bottom hanger by the hook. In principle, this collection of pulley blocks can be considered completed. To lift loads, you just need to use the mechanism correctly. To do this, you need to pull on the free end of the thread, which will lead to the connection of the hangers. Now you can try to lift heavy objects to a height.

There is another way to make a chain hoist with your own hands, which is somewhat more complicated, but differs in greater efficiency and reliability of the design. Here we need bearings, a gear, a hook, cables with blocks, and a threaded stud. First, we fix the bearings on the stud, after which we install the gear on the end of the stud, so that it is more convenient and easier to use a home-made chain hoist. It remains only to throw the cable over the gears and fix it, while the free end will be equipped with a hook, which is necessary for lifting objects.

Finally, we recall that when working with any chain hoists bought in a store or made at home, be sure to remember safety precautions. It is necessary to carefully check the design for strength and integrity. The loads themselves should be lifted smoothly and carefully, without being located under a suspended object at this time.