What Is Gear Coupling & How Does It Work - Full & Half Gear Coupling Size Chart

Gear couplings are essential components in many industrial applications, which sizes are available, and how to select them? This article will talk about what gear couplings are, how they work, their dimensions, and their differences from other types of couplings. Additionally, we will provide full and half gear coupling size charts to aid in selection and application.

What Is Gear Coupling?

A coupling in mechanical connection refers to a machinery device that connects two shafts together. The gear coupling is one of the types of couplings, used for the transmission of torque and rotational movement between two non-aligned shafts. It consists of two flexible joints, each attached to one shaft, connected by a central spindle, enabling power transfer even under misalignment. This design enables gear couplings to accommodate angular misalignment and parallel misalignment, they are suitable for high-torque applications where flexibility and misalignment compensation are required. Unlike rigid couplings, which do not allow any movement between shafts, gear couplings provide a flexible connection that can handle significant misalignment while maintaining high torque transmission capabilities, making them distinct from other coupling types such as rigid or flexible couplings.

Full Gear Coupling vs Half Gear Half Rigid Coupling

A full gear coupling consists of two toothed hubs fixed to both the driver and driven shafts, connected by sleeves with internal teeth that mesh with the hubs to enable torque transmission. This design accommodates both angular and parallel misalignment, full gear coupling is ideal for various industrial applications requiring high torque transmissions, such as in heavy machinery or hoisting mechanisms, where it connects the driving motor to the gearbox or smaller wire rope drums. In contrast, a half gear half rigid coupling features a combination of a rigid flanged hub and a flexible geared sleeve that meshes with the rigid hub. This design is ideal for applications where one shaft must remain fixed while the other accommodates slight misalignments, ensuring functionality in machinery where perfect alignment cannot be maintained but is still necessary to some extent.

How Does a Gear Coupling Work?

A gear coupling typically includes two hubs with external gear teeth and a flexible sleeve with internal gear teeth. The hubs are attached to the two shafts, while the sleeve meshes with the hubs. When the driving shaft rotates, it drives the hub attached to it. This rotation is transferred through the meshing gears to the flexible sleeve, which in turn drives the hub on the driven shaft. This mechanism ensures efficient torque transmission despite shaft misalignment. The gear teeth are designed to allow for angular and parallel misalignment between the shafts.

For example, a hoist mechanism where a gear coupling connects the driving motor to the gearbox. The motor shaft and gearbox shaft may not be perfectly aligned due to installation errors or operational conditions. The gear coupling’s flexible design allows it to compensate for this misalignment while efficiently transferring torque from the motor to the gearbox. This ensures smooth operation and reduces wear on other components.

How to Calculate the Gear Coupling Sizes?

To calculate the size of a gear coupling, you need to consider various factors related to the application and the specific requirements of the coupling.

1. Determine System Torque
If the torque is not given, you can calculate it using the following formula:
System Torque (T) [Nm] = Power [kW] × 9550 / Speed [r/min]

For example, if you have a motor with 30 kW power and a speed of 1440 r/min: System Torque = 30 × 9550 / 1440 = 203.13 Nm

2. Determine the Service Factor
The service factor is a multiplier that accounts for the operating conditions and load characteristics. It can be found in standard tables provided by coupling manufacturers. For example, a typical service factor for a motor-driven application might be 1.0.

3. Calculate the Required Coupling Rating
Multiply the system torque by the service factor to get the required coupling rating:
Required Coupling Rating = Service Factor × System Torque

For example, if the service factor is 1.0 and the system torque is 203.13 Nm, Required Coupling Rating = 1.0 × 203.13 = 203.13 Nm

4. Select the Appropriate Coupling Size
Refer to the product tables provided by the coupling manufacturer to select a coupling with a torque rating equal to or greater than the required coupling rating. Ensure that the selected coupling can accommodate the shaft diameters and other dimensional requirements.

5. Consider Additional Factors

Speed Capacity: Ensure that the coupling’s maximum speed rating exceeds the operating speed of the system.
Shaft Diameters: Verify that the coupling’s bore capacity can fit the shaft diameters.
Shaft Extensions: Check that the coupling’s minimum shaft length requirements are met.

Gear Coupling vs Grid Coupling, What Are the Differences?

For high-torque, heavy-duty applications where durability and high-speed performance are critical, gear couplings may be ideal. Grid couplings are better suited for applications requiring high misalignment tolerance, vibration dampening, and moderate torque transmission.

Feature	Gear Coupling	Grid Coupling
Design	Consists of two hubs with external gear teeth meshing with an internal sleeve.	Comprises two hubs connected by a flexible metallic grid.
Torque Capacity	High torque capacity, up to 12,500,000 Nm.	Moderate torque capacity, up to 70,000 Nm.
Misalignment Tolerance	Limited misalignment tolerance, suitable for low angular and axial misalignments.	High misalignment tolerance, suitable for angular and parallel misalignments.
Speed Capability	Suitable for high-speed applications.	Can operate at speeds up to 4500 RPM.
Vibration Dampening	Limited vibration dampening.	Excellent vibration dampening.
Shock Absorption	Limited shock absorption.	Good shock absorption due to flexible grid.
Maintenance	High maintenance is required, including lubrication and frequent inspection.	Moderate maintenance is required, including lubrication.
Cost	Higher initial and maintenance costs.	Moderate initial and maintenance costs.
Installation Complexity	More complex installation due to its heavy-duty nature.	Moderate installation complexity.
Applications	Heavy-duty applications such as mining, steel mills, and power generation.	General industrial applications, HVAC systems, conveyors, and pumps.

Fluid Coupling vs Gear Coupling, What Are the Differences?

In summary, choosing fluid couplings for applications requiring smooth starts, overload protection, vibration dampening, and gear couplings can ensure high precision and efficiency when high torques are needed.

Feature	Fluid Coupling	Gear Coupling
Working Principle	Transmits torque using hydraulic principles with no direct mechanical contact.	Transmits torque through meshing gear teeth between two hubs.
Torque Capacity	Lower torque capacity compared to gear couplings.	High torque capacity, suitable for heavy-duty applications.
Misalignment Tolerance	Moderate misalignment tolerance.	Limited misalignment tolerance, better for low angular and axial misalignments.
Speed Capability	Suitable for a wide range of speeds.	High-speed applications are possible.
Vibration Dampening	Excellent vibration dampening.	Limited vibration dampening.
Shock Absorption	Good shock absorption.	Limited shock absorption.
Maintenance	Low maintenance is required.	High maintenance is required, including lubrication.
Efficiency	Lower efficiency due to hydraulic losses.	High efficiency due to direct mechanical transmission.
Soft Start Capability	Provides smooth, soft starts, reducing wear on machinery.	No soft start capability.
Overload Protection	Provides overload protection by slipping under heavy loads.	No inherent overload protection.
Cost	Higher initial and maintenance costs.	Moderate initial and maintenance costs.
Applications	Ideal for conveyors, pumps, fans, and applications requiring soft starts.	Suitable for heavy-duty applications like mining, steel mills, and power generation.

Gear Coupling Sizes (Dimensions)

Full Gear Coupling Size Chart (MM)

Sizes	Max. Bore (mm)	Pilot Bore (mm)	Load Torque (kg.M)	Capacity (h.p. per 100 RPM)	Max. RPM	Wt. with Solid Hubs (kg)	GD²	Dimensions (mm)
Sizes	Max. Bore (mm)	Pilot Bore (mm)	Load Torque (kg.M)	Capacity (h.p. per 100 RPM)	Max. RPM	Wt. with Solid Hubs (kg)	GD²	A	B	C	D	E	F	G	H	M
100	35	10	50	7	8000	4.2	0.03	120	75	50	39.5	93	15	45	1.5	45
101	50	20	100	14	6300	10	0.14	170	110	65	49	115	17	55	2.5	65
102	60	30	250	35	5000	15	0.2	185	125	85	62	145	17	70	2.5	80
103	75	40	450	63	4000	26	0.48	220	150	105	78	175	20	85	2.5	105
104	90	50	850	119	3350	40	0.95	250	175	130	96	215	20	105	2.5	125
105	110	60	1300	182	2800	62	1.9	290	200	155	106	230	25	110	5.0	140
106	125	75	2000	280	2500	85	3	320	230	175	117	260	25	125	5.0	155
107	140	90	3500	490	2100	120	5.25	350	260	205	134	290	25	140	5.0	175
108	160	105	4500	630	1900	180	8.5	380	290	230	147	320	25	155	5.0	190
109	180	125	5600	784	1700	210	15	430	330	250	156	340	25	165	5.0	205
110	220	140	8200	1148	1400	290	30.5	490	390	310	171	370	25	180	5.0	220
111	260	160	11000	1536	1250	550	58	545	445	350	192	410	30	200	5.0	240
112	300	180	14700	2053	1120	710	88	590	490	400	231	490	30	240	5.0	280
113	330	200	20000	2793	1000	980	138	680	555	440	242	535	35	260	7.5	310
114	370	220	28600	3994	900	1320	291	730	610	500	266	575	35	280	7.5	330
115	410	250	34750	4852	800	1700	353	780	660	540	305	655	35	320	7.5	370
116	455	300	60000	8378	710	2550	680	900	755	625	335	720	45	350	10.0	425
117	520	375	83350	11917	630	3620	1235	1000	855	720	386	820	45	400	10.0	460
118	610	450	113000	15778	560	4860	1965	1100	950	810	430	920	55	450	10.0	510
119	710	520	149000	20805	500	3680	3012	1250	1050	910	446	1000	55	485	15.0	560

Half Gear Half Rigid Coupling Size Chart (MM)

Sizes	Max. Bore (mm)		Pilot Bore (mm)	Load Capacity		Max. RPM	Wt. with Solid Hubs (kg)	GD²	Dimensions (mm)
	Max. Bore (mm)			Load Capacity					A	B	C	D	E	F	G	H	M
	Gear	Rigid		Torque	H.P. per 100 RPM				A	B	C	D	E	F	G	H	M
100	35	50	10	50	7	8000	4.2	0.03	120	75	50	39.5	93	15	45	1.5	45
101	50	60	20	100	14	6300	10	0.14	170	110	65	49	115	17	55	2.5	65
102	60	75	30	250	35	5000	15	0.2	185	125	85	62	145	17	70	2.5	80
103	75	90	40	450	63	4000	26	0.48	220	150	105	78	175	20	85	2.5	105
104	90	110	50	850	119	3350	40	0.95	250	175	130	96	215	20	105	2.5	125
105	110	130	60	1300	182	2800	62	1.9	290	200	155	106	230	25	110	5.0	140
106	125	150	75	2000	280	2500	85	3	320	230	175	117	260	25	125	5.0	155
107	140	170	90	3500	490	2100	120	5.25	350	260	205	134	290	25	140	5.0	175
108	160	200	105	4500	630	1900	180	8.5	380	290	230	147	320	25	155	5.0	190
109	180	220	125	5600	784	1700	210	15	430	330	250	156	340	25	165	5.0	205
110	220	260	140	8200	1148	1400	290	30.5	490	390	310	170	370	25	180	5.0	220