- •Основы проектирования и конструирования
- •Санкт-Петербург
- •1. General guidelines
- •1.1. Objective and purposes of the coursework
- •1.2. Content and scope of the coursework
- •1.2.1. Explanatory note
- •1.2.2. Graphic portion of the course work
- •1.3. Selection of task for the course work
- •2. Guidelines of calculation portion of the course work
- •2.1. Electric-motor selection
- •2.2. Reduction unit kinematical and capacity calculations.
- •2.3. Toothed gear drive calculation
- •2.3.1. Assessment of permissible stresses
- •Permissible stresses for surface load durability
- •Permissible stresses for bending fatigue strength
- •Designedcalculationofhelicalgear
- •2.3.3.Testbendingfatiguestrengthcalculation
- •Designs of cylindrical gearings
- •2.3.4. Reduction unit wheels layout method
- •Calculation of forces acting in cylindrical toothed gears coupling
- •2.4. Design-basis calculation of the shafts
- •2.5. Selection of rolling bearings
- •Extension to reduction unit layout Slow speed (output) shaft.
- •Draw shaft diameter for the wheel of
- •(Fig.8)
- •2.6. General recommendations for the design of reduction unit housing elements
- •Inner walls of the housing mate the radius . (Fig.9)
- •2.7. Selection of tab
- •2.8 Test calculation of output shaft fatigue strength
- •Values и for the shafts with tab groove, made by end milling cutter
- •3. Guidelines to execution of graphic portion of the course work
- •4. Requirements to coursework completion
- •4.1. Requirements to explanatory note execution
- •4.2. Requirements to completion of coursework graphic section
- •5. Suggested reading
- •Example of title sheet execution for explanatory note to the coursework
- •Explanatory note to the coursework under the following topic:
- •Saint-Petersburg
Calculation of forces acting in cylindrical toothed gears coupling
Standard pressure force , directed alongside coupling line is spread into three orthogonal projections:
circumferential force , directed to pitch circle;
|
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2.4. Design-basis calculation of the shafts
A shaft is a running part of the unit on which the parts (toothed gears ets.) to transmit torque are fitted.
During design stage the diameter of output (input) section of the shaft can be defined from conventional calculation of rotation per maximum long-lasting torque acting at reduced value of permissible tangential stresses . Value is taken reduced, because this calculation does not take into account shaft bending resistance.
The shaft diameters are defined subject to strength conditions (see Figure 3):
input shaft diameter
,mm;
output shaft diameter
, mm
–torque on shaft under assessment, N m;
МPa – permissible stresses.
Minimum diameter values obtained for both input and output shafts are rounded to the closest large one from normal rows according to GOST. These diameter values should be applied as benchmark ones for further design of the shafts.
Diameters of other reduction shaft sections as well as lengths of these sections are defined in approximation during development of the design.
Then the diameter value of the shaft is defined as per rolling bearing as follows:
forinputshaft
;
foroutputshaft
,
insuchamannerthatcalculatedvalueisexpressedwithwholeintegerinmmandendingwith0or5 (seeitem2.5)
The pinion is to be integral part of the shaft, therefore the next section of the input shaft shall have the following diameter (see Figure 3 a)
.
Hence, – size of the bearing facet selected as per item 2.5. recommendation.
Then shaft diameter under the wheel is defined as follows :
.
The wheel nave diameter is defined :
.
Then diameter and length of the collar – it’s such a section of the shaft (narrow thickening) that serves as a limitation to wheel moves along shaft axle are assessed:
mm;mm.
The dimensions calculated are to be referenced with target dimensions under GOST 6636-69.
The dimensions and shape of end section of the shaft, () shall match the target values as per GOST 6636-69.
Cylindrical ends of the shaft can have two versions: 1 – long end 2 – short one.
Key dimensions of shaft cylindrical ends, mm (as per GOST 12080-66*)
Diameter d |
Length l |
r |
с | ||
Row1 |
Row 2 |
Version | |||
1 |
2 | ||||
10; 11 12; 14 16; 18 20; 22 25; 28 – |
– – 19 24 – 30 |
23 30 40 50 60 80 |
20 25 28 36 42 58 |
0,6 1,0 1,0 1,6 1,6 2,0 |
0,4 0,6 0,6 1,0 1,0 1,6 |
32; 36 40; 45; 50 |
38 42; 48 – |
80 110
|
58 82
|
2,0 2,0
|
1,6 1,6
|
55 60; 70 – |
53 63; 65; 75 |
110 140
|
82 105
|
2,5 2,5 2,5 |
2,0 2,0 2,0 |
80; 90 |
85; 95 |
170 |
130 |
3,0 |
2,5 |
Note. Row 1 diameter is preferable