# Calculation of open gear, Cylindrical gears, Bevel...

## Calculation of open gear

In open gears, it is very difficult to provide an optimum lubrication regime, so that the absence of a liquid lubricant in the contact zone of the mating surfaces of the teeth prevents the development of fatigue cracks. In this case, it is not necessary to check the endurance of tooth surfaces by contact stresses. In the presence of abrasive wear, the total length of the contact lines in helical gears is reduced, therefore helical gears are not used as open transmissions.

Open gears rely on endurance only for bending stresses.

## Cylindrical gears

The formulas for calculating endurance for flexural stresses are given in Sec. 3.2.3.2 (Table 3.7 "Verification calculation. 2. Endurance test for bending").

Since two unknown sizes enter explicitly into the formulas for determining the design stress on the transition surface (and this is a multivariant problem.) To simplify the design, use the crown width factor 1 M (table 3.7).

Then, after converting the formula to calculate the endurance for flexural stresses (Table 3.7 "Test calculation. 2. Endurance test for bending"), with some assumptions we get: All the parameters entering into the formulas (13.17), (13.18), are explained in Table. 3.7. The value of the number of teeth of gear 2 is recommended to be assigned from the interval (18-30).

The value 1 M when calculating the open cylindrical gears should be taken from Table. 13.5.

Table 13.5

The values ​​of the coefficient c/mta

The arrangement of the bearings relative to the gear ring (Figure 3.11)

Ummah with hardness of tooth working surfaces

7/ 2 <350 HB

H 2 & gt; 350 NV

Symmetrical and near the ring gear (gears 5 and 6)

0.60-0.70

0.45-0.50

Unbalanced (transfers 2 and 3)

0.50-0.60

0.30-0.40

One side of the ring gear (gear 1)

0.30-0.35

0.20-0.25

The values ​​of the module values ​​obtained by formulas (13.17), (13.18) should be rounded to the nearest larger standard value from Table. P.200.

In the subsequent calculation, the greater of these two values ​​of the linking module is used.

Using the values ​​of the module/and assigned number of teeth 2, the crown width ratio |/ m , and also the gear ratio and (Section 13.2), one of the algorithms given in Table. 3.12, 3.14, it is necessary to determine the geometric dimensions of the open cylindrical gear.

Further, according to the formulas of Table. 3.16, determine the values ​​of the force components in the meshing of a cylindrical open transmission.

## Bevel gears

Since only straight teeth are used as open transmissions, the only axial shape of the tooth is Form I (Section 3.2.4.1.1, Figure 3.34).

The formulas for calculating endurance for flexural stresses are given in Sec. 3.2.4.2 (Table 3.20 "Verification calculation." 2. Endurance test for bending ).

For the design calculation of the conical transmission for bending stresses, use the formula for calculating the endurance for flexural stresses (Table 3.7 "Test calculation. 2. Endurance test for bending"), modifying it somewhat with some improvements: All the parameters included in the formula (3.19) are explained in Table. 3.20.

The value of the number of teeth of gear 2 is recommended to be assigned from the interval (18-30).

For straight-bevel gearing, the value of the crown gear ratio K /h . should be determined by the formula: The following condition must be met: If the value of K /h , determined by formula (3.21), is greater than 0.3, then it should be assumed equal to this value.

The value of m when calculating the open cylindrical gears should be taken from Table. 13.5.

The value of the modulus value obtained by formula (3.20) should be rounded to the nearest larger standard value from Table. P.200.

Using the values ​​of the module m, the assigned number of teeth r ] , the value of the width coefficient of the ring gear K ^ defined above, and also the gear ratio and (Section 13.2) according to the algorithm given in Table. 3.21, it is necessary to determine the geometric dimensions of the open conical gear.

Further, according to the formulas of Table. 3.23, the values ​​of the force components in the meshing of the conical open gear should be determined.

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