Mechanical jack

Introduction

Jacks throughout the time since the creation of cars are considered the most necessary on-board tool. You can't do without it on a deserted country highway if the wheel punctured and you need to put a "spare." A ride on a lowered wheel to the tire assembly workshop threatens more serious breakdowns in the suspension and steering systems. Therefore, on equipment such as car jacks, you should not save, but it is better to choose the type of jack that is most suitable for your car. This work selects the design and calculates it according to the specified parameters.

Working Environment Characteristics

A jack is a stationary, portable or mobile lifting mechanism for lifting and fixing heavy objects at a given height. The jack can be used as an independent device during repair or construction work, or as part of more complex mechanisms (cranes, lifts, presses, etc.)

Almost every person knows the most common version of this useful mechanism - a car jack. A compact screw jack is usually attached to a passenger car; such a jack is driven exclusively by the muscular force of a person.

There is a legend that in ancient times the jack was used during hostilities as an instrument with which the gates of the besieged city were broken, and therefore, the design of this mechanism was classified for a long time. Today, jacks are freely sold and are used exclusively for peaceful purposes.

The jack is widely used in construction and installation work, as well as in the automotive industry and in railway work.

The jack is capable of withstanding very significant loads, which makes it indispensable for the repair of railway tracks or wagons. The scope of jacks is quite wide; this mechanism greatly facilitates many areas of human activity.

As a rule, the jack of many is associated with the change of wheels of the car. In fact, it is applied much more widely. The jack can perform both complex operations, for example, moving the spans of the bridge, and lighter ones: raise and hold the body of the car during repair work. Also, with the help of a modern jack, you can pull wires on high-voltage lines, compress a powerful spring, push a pipe through the ground, destroy the old floor in the building and much more. Without a jack, it is impossible to lift and move large blocks or individual parts of mounted structures, units or equipment parts. Unlike other similar devices (for example, winches), it is more compact, easy to maintain, reliable in operation. Another difference is that when working, the jack is always located directly under the load.

Common jack characteristics:

Jack lifting capacity - characterizes the maximum possible weight of the lifted load.

Pick-up height is the minimum distance between the support surface (ground, floor) and pick-up (jack support point) in the lower operating position, respectively - the lower edge of the load .

In the automobile section, this is a clearance.

Lifting height - the maximum distance from the support surface to the pick-up in the upper operating position.

Working stroke - the distance between the lower and upper working position of the pick-up.

Own weight - the weight of the jack in working condition.

For some types of jacks, the gear ratio characteristic is also relevant - for example, the ratio of the plunger area of ​ ​ a hydraulic pump with the lifting plunger area in hydraulic jacks. It depends on the force on the handle of the jack with manual pumping or the power of the electric pump motor.

Advanced Design Design and Description

During the study of the structures and based on the data obtained in the course project task, it was decided to select a rhombic screw jack as the object. The advantages of this design are simplicity, reliability, relatively small dimensions, low weight and low pick-up height. The disadvantages of the design include low load capacity, insufficient stability and a small area of ​ ​ the support with the body of the car, which can lead to damage to the paint coating or the body itself.

To eliminate the above drawbacks, changes were made to the design of the standard product:

- to accelerate the lifting of the car, it is necessary to use two-way threads. This solution will speed up the installation and removal of the jack.

- to increase stability of the structure, the jack support area is increased.

- to avoid damages of paint coating and body, it is necessary to increase the contact area and use a two-layer stop. The top layer must be made of dense rubber.

Selection of basic materials depending on calculated parameters

During the study of the design and purpose, the most optimal materials for the manufacture of the product were selected.

Steel 20 is the most optimal material for the case. This material is quite strong and inexpensive, by this it fits most into this design.

45X steel is used to make the screw. Since the screw has the main load and wear, it is necessary to use steel with a large amount of carbon with the addition of chromium. Chromium reduces thread wear and increases tensile moment resistance.

Handle material - St3 kp

Upper part of stop is made of high-strength rubber.

This choice is due to sufficient strength and at the same time low cost of the product.

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