Model Selection of Gear Couplings
When choosing gear couplings, one should firstly choose models and specifications of couplings according to basic information. And then, checking whether the max bore diameter and max radial dimension (rotational space) and allowable speed of corresponding couplings meet the working conditions based on standards. In this way, one can determine the model and specification of gear coupling.
Selection of couplings should follow the following steps.
1.1 The basic information for selection and use
Name of drive machines, quantity of drive machines, input power, working speed, name of working machines, load types, working environment, nature of work, start frequency, existence of positive & negative rotation, diameters and lengths of input shaft and output shaft.
Basic information see attached table 1.
|
Coefficient of engine Kw |
Engine name |
Start coefficient Kz |
Number of starts |
Working condition coefficient |
Load type | Work machine names example |
| 1.0 |
The motor and turbine |
1.0 |
≤120 | 1 | Even load |
Blower, pump, compressor, liquid mixing equipment, textile machinery( printing machine, sizing machine), papermaking equipment, bleaching machine, leveling machine, uniform loading conveyor |
| 1.2 |
Four and more than four cylinder internal combustion engine |
1.3 |
＞120～240 | 1.5 |
Light impact load |
Textile machinery (squeezing machine, recoiling machine), papermaking equipment (recoiling machine), nonuniform loading conveyor, feeding machine, printing machine |
| 1.4 |
Two cylinder internal combustion engine |
Determined by manufacturers |
＞240 | 2 |
Medium impact load |
Lifting machinery, crane and windlass, rotary crusher, rolling equipment, oil machinery, papermaking equipment (agitator and crusher, cutter) |
| 1.6 |
Single cylinder internal combustion engine |
2.5 |
Heavy impact load |
Swinging conveyor, crusher, stone crusher, reciprocating feeding machine, rubber machinery |
||
|
3 |
Extra heavy impact load |
Reversible roller conveyer, blooming mill, plate mill, the breast roll, shearing machine, punching machine |
1.2 Selection calculation of gear coupling
The main parameter of coupling is nominal torque Tn. When choosing couplings, toques should conform to the following formula:
T＜Tc≤Tn＜[T]＜[Tmax]＜Tmax
In the formula:
T - Theory of torque, N·m;
Tc - Computed torque, N·m;
Tn - Nominal torque, N·m;
[T] - Allowable torque, N·m；
[Tmax] - Maximum allowable torque, N·m；
Tmax - Maximum torque, N·m；
1.2.1 Theories torque calculation of gear couplings
Computational formula: T=9550Pw/n
In the formula:
Pw - driving power, kW;
N - working speed, r/min.
1.2.2 The torque calculation of gear coupling
Computational formula: Tc=T·Kw·K·Kz
In the formula:
Kw - Coefficient of engine (see table 1)
K - Working condition coefficient (see table 1)
Kz - Start coefficient (see table 1)
1.2.3 When the following situation occurred, it should be calculated and selected by the following methods:
① High peak loads
② Brake (brake wheel or brake disc is parts of the coupling)
③ High frequency axial channeling move
Peak load
When the motor torque is higher than general situation, and there is shock loads, frequent starting and braking, intermittent operation and repetitive peak load of system, choose couplings with torque equal to or greater than the number calculated from the following formula.
a. No reverse peak load
selection torque (N·m)=system peak torque
or selection torque (N·m)=system peak power(Kw)×9550/rotate speed (rpm)
b. Have reverse peak load
selection torque (N·m)=1.5×system peak torque
or selection torque (N·m)=1.5×system peak power(Kw)×9550/rotate speed (rpm)
c. Occasional peak load (no reverse)
During the expectation life of the coupling, if the system peak load appeares less than 1000 times, use the following formula:
selection torque (N·m)=0.5×system peak torque
or selection torque (N·m)=0.5×system peak power(Kw)×9550/rotate speed(rpm)
For reverse situation, please use step b.
Brake
If the brake torque exceeds the motor torque, calculate the selection torque according to the following formula:
Selection torque (N·m)=brake torque×application factor
High frequency axial channeling shift
If the axial channeling moves more than 5 times per hour, then the working condition coefficient should be increased by 0.25.
Selection torque (N·m)=power(Kw)×9550×(application factor+0.25)/rotate speed(rpm)
1.3 Select model specifications of coupling preliminary.
1.4 Selection verification
1.5 Determining the model specifications of coupling.
1.6 Product marking
Examples
2.1 General information
Rated motor power: 30Kw
Output revolutions per minute: 1500rmp
Diameter of input shaft: 48mm
Diameter of output shaft: 35mm
The distance between input end and output end: 3mm
Working temperatures: -30℃ - 120℃
Nature of load: Heavy impact load
Surroundings: Dusty or others.
Nature of work: Continual work.
2.2 Calculation
According to the general information, this project should use GA gear couplings based on SD standards.
Calculation of models
Calculation of theoretical torques: T=9550Pw/n=9550*30/1500=191 (N·m).
Calculation of calculated torques: Tc=T·Kw·K·Kz.
In this case, Kw=1, K=2.5, Kz=1, then Tc=191*1*2.5*1=477.5 (N·m).
2.3 Preliminary selection of gear coupling models
GAB1 gear couplings with 1800 N·m nominal torque.
This type of gear coupling meets requirements on torques. GAB1 is the preliminary selection.
2.4 Confirmation
2.4.1 Bore diameter
The max bore diameter of GAB1 is 52mm.
Meet requirements on bore diameter.
2.4.2 Rotary Space (Compared with the conditions on site)
No limitation listed, GAB1 meets requirements on rotary space.
2.4.3 Allowable revolution per minute
The allowable revolution per minute of GAB is 6000rpm.
The actual output RPM of the universal joint is 1500rpm.
GAB1 meets the requirements.
2.5 Selected model specifications of coupling
The distance between input and output end is 3mm, therefore, the model and specifications of coupling are selected as follow:
GAB1 48*L/35*L C=3
2.6 Marking Example
GAB1 gear coupling
Input end: J1 type shaft hole, Type A keyway, d=48mm, L=43mm.
Output end: J1 type shaft hole, Type B keyway, d=35mm, L=43mm.
GAB1 coupling: J1 A 48*43/J1 A 35*43, separation distance C=3.
For more information concerning gear couplings, please refer to the following articles: