Worm gearbox: parts, calculations, specification

Contents

1 Introduction

2 Motor selection and kinematic calculation

3 Calculation of the 1st worm gear

3.1 Design calculation

3.2 Check calculation by contact voltages

3.3 Check of gear teeth for bending

4 Calculation of the 2nd chain transmission

5 Preliminary calculation of shafts

5.1 Drive shaft

5.2 2nd shaft

6 Structural dimensions of gears and wheels

6.1 Worm wheel of the 1st gear

6.2 Leading asterisk of the 2nd chain transmission

7 Selection of coupling on drive input shaft

8 Test of key joints strength

8.1 Worm gear of the 1st worm gear

8.2 Leading asterisk of the 2nd chain transmission

9 Gearbox housing structural dimensions

10 Serviceability check of bearings

10.1 Calculation of reactions in supports of the 1st shaft

10.2 1st support of the 1st shaft

10.3 2nd support of the 1st shaft

10.4 Calculation of reactions in supports of the 2nd shaft

10.5 2nd shaft

11 Calculation of shafts

11.1 Calculation of moments of the 1st shaft

11.2 Periods of moments of the 1st shaft

11.3 Calculation of the 1st shaft

11.4 Calculation of moments of the 2nd shaft

11.5 Era of moments of the 2nd shaft

11.6 Calculation of the 2nd shaft

12 Thermal calculation of reduction gear box

13 Choice of oil grade

14 Selection of fits

15 Gearbox assembly technology

16 Conclusion

17 List of literature used

Introduction

A design engineer is the creator of a new technique, and the level of his creative work is more determined by the pace of scientific and technological progress. The activity of the designer is one of the most complex manifestations of the human mind. The decisive role of success in creating a new technique is determined by what is embedded in the design drawing. With the development of science and technology, problematic issues are solved taking into account the increasing number of factors based on the data of various sciences. The project uses mathematical models based on theoretical and experimental studies related to volume and contact strength, materials science, heat engineering, hydraulics, the theory of elasticity, and construction mechanics. Information from material resistance courses, theoretical mechanics, machine-building drawing, etc. is widely used. All this contributes to the development of independence and a creative approach to the problems posed.

When choosing the type of gearbox for driving the working element (device), it is necessary to take into account many factors, the most important of which are: the value and nature of the load change, the required durability, reliability, efficiency, weight and overall dimensions, noise level requirements, product cost, operating costs.

Of all types of gears, gears have the smallest dimensions, weight, cost and friction losses. The loss factor of a single gear pair with careful execution and proper lubrication does not usually exceed 0.01. Gear gears in comparison with other mechanical gears have great reliability in operation, constant gear ratio due to lack of slippage, and can be used in a wide range of speeds and gear ratios. These properties provided a large distribution of gears; they are used for capacities ranging from negligible (in instruments) to measured in tens of thousands of kilowatts.

The disadvantages of gears may include high manufacturing accuracy requirements and high speed noise.

Slash wheels are used for critical gears at medium and high speeds. The volume of their use is more than 30% of the volume of use of all cylindrical wheels in machines; and this percentage is continuously increasing. Slash wheels with hard tooth surfaces require increased protection against contamination to avoid uneven wear along the length of contact lines and the danger of dyeing.

One of the goals of the project is to develop engineering thinking, including the ability to use previous experience, model using analogues. For the course project, objects are preferred, which are not only well distributed and of great practical importance, but also are not subject to moral aging in the foreseeable future.

There are various types of mechanical gears: cylindrical and conical, with straight teeth and oblique, hypoid, worm, globoid, one- and multithreaded, etc. This raises the question of choosing the most rational transmission option. When choosing the type of transmission, they are guided by indicators, among which the main ones are efficiency, overall dimensions, weight, smoothness of operation and vibration loading, technological requirements, the preferred number of products.

When choosing the types of gears, type of engagement, mechanical characteristics of materials, it should be borne in mind that material costs account for a significant part of the cost of the product: in general-purpose gears - 85%, in road cars - 75%, in cars - 10%, etc.

Select Fits

Landing of gear elements on shafts - that according to ST CMEA 14475 corresponds to light press landing.

Fitting of couplings on shafts of reduction gear box -.

Journals of shafts for bearings are made with deviation of shaft k6.

We assign the remaining fits using the data of table 8.11 [1].

Gearbox Assembly Technology

Prior to assembly, inner cavity of reducer housing is thoroughly cleaned and covered with oil-resistant paint. Assembly is performed in accordance with drawing of general view of reduction gear box, starting from shaft assemblies.

Keys are laid on shafts and gearbox gear elements are pressed. The retaining rings and bearings should be fitted, pre-heated in oil up to 80100 degrees Celsius, in series with the transmission elements. The assembled shafts are laid in the base of the reduction gear case and put on the cover of the case, covering the surfaces of the joint of the cover and the case with alcohol varnish. For alignment, a cover is installed on the body using two conical pins; bolts that attach the cover to the housing are tightened. After that, lubricant is put into bearing chambers, bearing covers with set of metal gaskets are installed, heat gap is adjusted. Prior to installation of through covers felt seals impregnated with hot oil are put into grooves. By turning the shafts there is no jamming of bearings (the shafts must be rotated by hand) and the cover is fixed with screws. Then plug of oil discharge hole with gasket and iron oil indicator are screwed in. Oil is poured into the housing and the inspection hole is closed with a cover with a gasket, the cover is bolted. The assembled gearbox is rolled and tested on the bench according to the program set by the specifications.

Conclusion

During the course project on "Machine Parts," the knowledge gained over the past period of training in such disciplines as: theoretical mechanics, material resistance, materials science was fixed.

The purpose of this project is to design the chain conveyor drive, which consists of both simple standard parts and parts, the shape and dimensions of which are determined on the basis of design, technological, economic and other standards.

In the course of solving my task, the method of selecting the drive elements was mastered, design skills were obtained to ensure the necessary technical level, reliability and long service life of the mechanism.

The experience and skills gained during the course project will be required in the execution of both course projects and the diploma project.

It can be noted that the designed reduction gear has good properties in all respects.

Based on the results of calculation for contact endurance, the effective stresses in engagement are less than the permissible stresses.

Based on the results of the calculation of bending stresses, the actual bending stresses are less than the permissible stresses.

The calculation of the shaft showed that the safety margin is more than permissible.

Required dynamic lifting capacity of rolling bearings is less than passport capacity.

When calculating, an electric motor was selected that meets the specified requirements.

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