What is a jack, what is it for and how to choose

A jack is a must have in the trunk of every car. Even 40 years ago, every car was equipped with jacks, these were rack-and-pinion devices with a load capacity of 500 kg or more. Today we have the opportunity to choose any jack with the necessary characteristics, which can be used both for your car and for service stations.

What is a jack?

The jack is a lifting device securing the car at a given height. Thanks to the use of the lift, it is possible to carry out tire fitting, diagnostics and suspension repairs without a pit and lift. Among other things, the jack can be used in everyday life, where you need to lift heavy objects. The market for automotive products is filled with all kinds of jacks, which differ from each other in the form of performance, characteristics and functionality.

Purpose and principle of operation of the jack

The jack is designed to lift and hold a load resting on it, for example, a car during repairs (replacing a wheel, shock absorber, etc.). The principle of operation will depend on the type of device. For example, the hydraulic model uses the movement of a rod under the action of a high pressure of the working fluid.

Regardless of the type of jack and its load capacity, they all have the same principle of operation. On one side, the jack rests on the ground, and on the other side, on the load being lifted. To move the rod (or lifting platform), a different kind of lever is used. To perform a specific task, a specific type of jacks is used (the design features of the mechanism are taken into account).

Device and characteristics

In order for each type of jack to be able to cope with the task assigned to it, it may have a special design. The classic jack device consists of:

1. Reserve tank filled with hydraulic fluid;
2. The main container (cylinder) in which the retractable rod is located;
3. The piston, which pushes the rod due to the receipt of an additional amount of hydraulic fluid;
4. Pickup - the heel, which rests on the load being lifted;
5. The bases with which the jack rests on the ground;
6. Pumping valve, which does not allow fluid to move freely between communicating vessels;
7. A safety valve that prevents the jack from being overloaded. It works on the principle of a safety valve in a hydraulic system.

Material

Different materials are used for the manufacture of jacks. Their choice is influenced by the carrying capacity of the device and its design. For example, a rolling jack for passenger cars is made of aluminum. Its stiffening ribs are enough to support the weight of a passenger car and a small SUV.

To lift a truck, hardened steel or cast iron versions are used. Even if the hydraulics are able to withstand a significant weight of the load, the total lifting capacity of the jack also depends on the material used for its manufacture and design features (additional stiffeners and their thickness).

Lifting capacity

It is extremely important to choose a jack to lift the machine with the required lifting capacity. If this parameter does not fit the weight of the car, it is better not to use a jack. If the curb weight of your vehicle is 1500 kg, then the lifting capacity of the lifting device should be from 1700 kg, preferably 2 tons. If a lifting device with a lower potential is used, this can lead to instant failure and the suspended vehicle will fall. What you need to know:

• for owners of cars whose maximum weight does not exceed 1,5 tons, and ground clearance not more than 200 mm, then choose a simple rhombic jack for 2 tons, which will be enough for tire fitting and short work;
• car services, and those who need a long hold of the car in limbo, it is better to pay attention to the jack with a lifting capacity of 3 to 5 tons, which is enough for the use of SUVs and small commercial vehicles;
• for trucks, there are their own lifting devices that hold 15-30 tons. You need to choose a jack for the truck based on its maximum weight, that is, with a vehicle weight of 7 tons, its load capacity is 8 tons, then the jack needs 15 tons.

Jacks with higher payloads are more expensive in price, but they guarantee reliable support for cars, and this is your safety!

What affects the height of pickup

The pickup height is the minimum value with which the jack begins to work. It is necessary to pay attention to this parameter, because a car with a clearance of 170 mm cannot be lifted by a jack with a pick-up height of 15 cm. It is simple to choose a suitable jack by this value: measure the distance to the threshold of the car on a level road, if it is 150 mm, then the pick-up height the lift should be 70-100 mm.

Maximum lift height

Another parameter to pay attention to. The value speaks for itself: the height of the lift is the maximum value by which the car can be lifted. For replacing wheels, dismantling and mounting work on the suspension and removing the gearbox from front-wheel drive cars. Sufficient lifting height varies from 30 to 50 centimeters. The rise of more than 50 cm is necessary if the car wheel fell into a deep hole and you need to raise this side. In other cases, bricks or boards are placed under the jack.

Types of jacks and their purpose

There are corresponding jacks for each type of vehicle. They are also divided by installation method and drive type. Jacks are distinguished by the type of drive: mechanical, hydraulic and pneumatic, the latter two are actively used in car services. By type, jacks are:

• rack and pinion;
• lever-screw;
• movable;
• rhombic. 

Features of screw jacks

This is the oldest type of jack, which was equipped with all Soviet cars, and is still equipped with the domestic Lada 4 × 4 SUV. The carrying capacity of the device varies from 500 kg to 1.5 tons. Platforms with square pipes are provided for such a jack. The principle of operation is simple: the jack lever is installed in a special eye in the body, moving the handle, the force on the mechanism screw is transmitted by a gear. Turning the knob clockwise raises the car, in the opposite direction it lowers. A screw jack has more disadvantages than features: a small area of ​​​​support, due to which the jack can come off, large dimensions. If the spring is damaged by corrosion, then such a jack can no longer be used. 

Advantages: small effort to lift, high lifting height and reasonable cost.

Features of rhombic jacks

Most often found on the shelves of auto products, as well as they complete cars. The rhombic jack can be mechanical and hydraulic. The carrying capacity varies from 0.7 to 2.2 tons. The name of the lifting device comes from its design, consisting of 4 levers, which allows the use of such a “lift” in cars with low ground clearance, and high lift it. 

The mechanical jack works by rotating a lever that hooks onto the jack screw. More expensive and more convenient to use - hydraulic: a hydraulic piston is used as a lifting device, which works on the principle of pumping liquid. Such a jack is equipped with a handle, with which you pump up pressure, lifting the car. To lower the car, it is necessary to turn the valve with the handle to release the pressure in the piston.

Advantages:

• affordable price;
• wide range of manufacturers and execution;
• reliability;
• large footprint.

Disadvantages:

• small working stroke;
• muscle lifting effort is required;
• low efficiency of the device, it takes a long time to climb (for a mechanical type).

Features of rack jacks

A wide and material-intensive mechanism is used, with a lifting capacity of up to 3500 kg. A gear rack is used as the supporting element along which the ratchet moves. The design allows you to lift objects not only in the vertical but also in the horizontal plane. Depending on the load, the jack can be single-stage, two and three-stage. Such a jack is used on SUVs and ATVs.

Advantages:

• lifting height more than 100 cm;
• low pickup, which allows you to raise vehicles means, practically, from the ground.

Disadvantages:

• large dimensions and weight;
• improper use can damage the body.

Features of lever screw jacks

This type of jack has a lifting capacity of up to 1000 kg. The design consists of several levers and a power screw, which is driven from the handle. There are two types of lifting gear:

• classic lever-screw. It uses two levers, when the screw rotates, the angle between the levers changes, due to this the car rises or falls. The disadvantage is greater effort at the start of the lift and insufficiently strong structure;
• combined. It is a bunch of lever and diamond-shaped jack. The principle of operation is similar to lever-screw, has the same disadvantages, but the jack is light and small, for small cars operating in the city this is the most acceptable option.

Features of rolling jacks

The rolling jack, according to workers in the automotive service sector, is the most convenient and functional. The initial load capacity of 2000 kg. The design represents an improved version of the classic hydraulic jack, only with wheels and a large lever. Such a jack can be used for both cars and trucks, weighing up to 5t. The wide area of ​​the stop allows you to raise the vehicle, resting against a bridge or subframe.

Advantages:

• high carrying capacity;
• wide area of ​​contact with the sub-jack;
• sustainability;
• ease of movement on a flat surface;
• minimal muscular effort is required to lift.

Disadvantages:

• cost;
• high mass;
• bulkiness of wheels;
• it is possible to use only on a flat surface.

 Hydraulic jacks

These jacks include rolling and bottle jacks. The second type has small dimensions, carrying capacity from 0,5 to 30 tons! The principle of operation is simple: the work is carried out on the simplest Pascal's law, where two vessels filled with hydraulic oil communicate with each other. When you press the lever, the oil is pumped from one chamber to another, creating excess pressure - the engine piston up, raising the vehicle. Return the piston to its original position allows the bleed valve, which must be turned counterclockwise. The liquid is pumped back into the first chamber by depressurizing. 

Advantages:

• high carrying capacity with small dimensions;
• minimal effort is required on the lever;
• high efficiency;
• reliability in compliance with load capacity.

Disadvantages:

• small footprint;
• in case of oil leak there is a risk of a sudden drop in pressure;
• periodic oil change is required, which tends to become contaminated.

Pneumatic jacks

A feature of the pneumatic jack is that the lifting force is due to compressed air. The design implies the presence of a chamber for air, which expands filling, lifting the car. The pneumatic jack can be rolling or portable. For its operation, compressed air is needed, which is pumped by a compressor, so this option is not the best for domestic purposes.

Advantages:

• high efficiency;
• as fast as possible car lift;
• ease of use;
• reliability in serviceability of valves and cranes.

Disadvantages:

• a sharp drop in the car due to bleeding the faulty valve;
• the rubber cushion may crack and suddenly leak.

Mechanical

This is one of the most common and simple jacks. At the heart of his work is the lifting of the load by twisting into a folding stud design. Most car models are equipped with such a jack. The load capacity of this device is enough to cope with the task of supporting a car.

Электрический

In this case, this is not the type of jacks, but the type of drive. An electric motor is used as an alternative to a manual drive. Depending on the load capacity of the device, this can be a motor powered by a 220 volt network or from a car cigarette lighter. an electric drive is often used in screw jacks.

Electro-hydraulic

This is also a kind of hydraulic jack, only unlike the previous version, its rod is set in motion by pumping hydraulic fluid with an electric drive. Some electro-hydraulic jack models are equipped with an additional hand lever.

Pneumohydraulic

This is also a type of hydraulic jack. The injection of hydraulic fluid is provided by high air pressure. For the operation of such a jack, a mandatory connection to an air compressor.

Tablet

This is a type of jack design that works hydraulically. Such a device has a platform made in the form of a cylinder with a low profile. The mechanism is connected to a separate hydraulic drive.

Klinovoy

This design is designed to lift an impressive load. The supporting and lifting parts of the mechanism are made in the form of wedges. Wedges are inserted between them on both sides, which, approaching, increase / decrease the distance between the platforms. A screw or hydraulic mechanism can be used as a drive in such a jack.

Bottle

Most hydraulic jacks are made in this form. In the design of such mechanisms, the main (working) cylinder is clearly expressed. Another name for such jacks is telescopic. The reason is the rising stem, which moves by raising the piston under the action of the pumped hydraulic fluid.

There are several modifications of jacks in this category. They can be single or double stem. In the second option, it is possible to lift the load to a greater height. Much less often you can find a model with three rods.

Lever

This is a jack model, which has a fairly simple design. The peculiarity of this type of mechanisms is that they allow you to lift the load high. It looks like a similar jack in the form of a rail, retractable with a hand lever.

Pulling

In this case, not the pushing principle is used, but the tension mechanism. For the operation of such a jack, a strong support is used, to which the jack is suspended, and a load is suspended from it. Jacks with this principle of operation are used for tightening overall metal structures, heavy hull parts of ships, etc. On some modifications there are hooks for hooking the load.

Jack "Selson"

This kind of jacks is often found at tire shops. They are represented by a metal platform on which a pneumatic cushion is installed. The operation of such a jack involves connecting to an air compressor.

Specialized jacks

Some models of jacks have a special device, which is why they can be used exclusively for specific purposes. Here are some common options.

Auto tipper

As the name implies, this mechanism is not used to hang the car, but to tip it on its side. The mechanism consists of two stops. One is a vertical rail, on which a transverse bar is fixed with an emphasis for wheels on the opposite side of the car being raised.

repair stand

Another name for the mechanism is a car rack. Such a jack is used as an insurance that prevents the suspended car from falling. Another device is used to lift the vehicle. This stand has a rigid latch that allows you to securely fix the raised car at a certain height.

Transmission rack jack

This type of jack is used to lift, hold and move the gearbox. Basically, the design of such a lifting mechanism is equipped with wheels that allow you to move the removed unit.

Yamny

In another way, such a jack is called a ditch. It allows you to raise the axle of the car, propping it up at the base of the inspection hole.

How to choose a car jack 

To select the required jack, we will use the following data:

• the curb weight of your vehicle. Add 300 kg to this mass, so you will ensure reliability and your safety;
• the lifting height can be no more than 50 cm, this is quite enough for repair work on a flat surface;
• pickup height should be 30-50% less than the clearance of your car;
• according to the type of work, you can choose between mechanical and hydraulic, pneumatic is more suitable for service stations. For ease of use, it is better to use a hydraulic jack, if you want to save money, then a manual diamond-shaped jack will be the best choice;
• What reference area do you need? For service stations, this parameter should be greater; for private use, a small enough area should be suitable for a sub-jack. Bottle jacks are not recommended for use on vehicles with a bottom damaged by corrosion, otherwise the stem may pierce the metal;
• if you plan to frequently repair a car, keep it on the weight for a long time, then rolling jacks with a carrying capacity 0.5-1 tons higher than your car will help you.

Safety rules when working with jacks

The jack itself is not a dangerous mechanism. The main danger is represented by loads that are lifted with the help of such devices. Therefore, before you start working with a jack, you need to remember the key safety rules.

When hanging part of the car or the entire vehicle, you must remember:

• If one side of the machine is being lifted, all wheels in contact with the ground must be secured to prevent the machine from rolling during operation. Otherwise, the car will fall off the jack. To prevent this, you need to put the car on the handbrake or use wheel chocks.
• When the car is raised, regardless of the load capacity and design of the jack, it is necessary to put insurance under the load-bearing part of the body (spar, threshold, frame, etc.). This may be a removed wheel on a pallet, a stump, etc. The main thing is that when falling from a jack, such insurance securely holds the car. This will protect against injury during repair work.

Accessories

For most jack modifications, you can purchase an additional accessory, for example, it can be an adapter, a rubber pad for picking up or supports. The adapter is often used in conjunction with a rolling jack. This element is made in the form of an additional telescopic bar with strong stiffening ribs, along the edges of which there is one support platform.

Thanks to this design, the load on the contact part of the lifted load is reduced (it is evenly distributed into two parts). Such an accessory will prevent breakage of the supporting element of the car if the car is heavy.

Advantages and disadvantages of different jacks

To talk about the advantages and disadvantages of jacks, you need to take into account their modification and the work that needs to be done with their help. Here are the features of some types of jacks:

• The rack jack is great for lifting very low loads. For example, if the car sat down in the mud, such a jack will allow it to be lifted. But to work with such a mechanism in the car, special stops must be made in the bottom.
• The rhombic screw jack has a compact size, making it easy to always carry with tools in the car. The disadvantage of such jacks is that they do not raise the car high.
• The hydraulic jack has a high efficiency with minimal dimensions. With it, you can quickly and easily hang out part of the machine. The disadvantages of such modifications is the need for high ground clearance for the car. To raise a passenger car on such a jack, you need to drive the required wheel onto a hill (for example, on a bar or brick). Only after that it will be possible to substitute a hydraulic jack under the car. A small lifting height is another drawback of such jacks.
• The pneumatic jack will lift the car as efficiently as possible on any surface due to the large stop area. The disadvantage of such jacks is that the pillow is easily damaged on the sharp parts of the car body. Also, to use this device, it requires a car compressor.

As you can see, it is necessary to select a jack for the car, focusing on what work will need to be done with it.

Related videos

Here is a short video on how to choose the right jack for your car:

How to choose a jack. RIGHT CHOICE. Release 22

Questions and answers:

What are jacks used for? With the help of this mechanism (it can be stationary or portable), a load is lifted and held at a specific height, for example, a car, its one side or a power unit.

Why is the jack so called? It is believed that this name originated from Goll. dommekragt - "ship gate". Some believe that the ancestor of this mechanism was used to storm the city gates.

Where is the hydraulic jack used? In auto repair shops, in manufacturing, in heavy industry, on construction sites, in the field of oil, gas, etc. Wherever you need to lift an impressive load.