GS 55 - AXIS GS Couplings

GS standard types - For size 5 to 38 hub material aluminium/for size 42 to 90 hub material steel
Size	Spider GS ¹⁾ torque T_KN [Nm]			D_max. for hub type			Dimensions [mm]										Setscrew DIN EN ISO 4029
Size	98 ShA	57 ShD	64 ShD	1.0	1.1	1.2	DN	DH	DI1	L	L1, L2	M, N	E	B1	S	A	G	T	TA [Nm]
55	685	770	825	74	–	–	110	120	60	160	65	37	30	22	4.0	4.5	M 10	20	17

The GS 55 Coupling (Size 55) is an ultra-heavy-duty, zero-backlash flexible coupling designed for the largest servo drives and high-torque industrial positioning systems. With an outer diameter of 120mm, the GS 55 represents the upper tier of the precision coupling range, capable of transmitting nominal torques up to 685 Nm (with a standard 98 ShA spider).

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Key Specifications (Model GS 55)

The GS 55 is built for heavy engineering and large-scale automation. Below are the standard technical specifications:

Parameter	Value
Coupling Size	GS 55 (Size 55)
Nominal Torque	450 Nm (92 ShA Yellow) / 685 Nm (98 ShA Red) / 900 Nm (64 ShD Green)
Max. Torque (Peak)	900 Nm to 1,800 Nm (approx. 2x Nominal)
Max. Rotational Speed	Up to 6,000 RPM (Hub material/design dependent)
Bore Range	30 mm to 74 mm (Standard)
Outer Diameter	120 mm
Hub Material	Steel or Spheroidal Cast Iron

How It Works

The GS 55 operates on a high-force, pre-tensioned principle to guarantee zero backlash:

Interference Fit: The large elastomeric spider is dimensionally wider than the gap between the steel jaws. During assembly, massive force is used to compress the spider into the jaws, creating a pre-loaded fit that eliminates all mechanical play.
Heavy-Duty Transmission: The concave jaw profile maximizes surface contact with the spider teeth. This allows the GS 55 to transmit nearly 700 Nm of torque without deformation, ensuring that the driven load moves exactly in sync with the motor.
Vibration Absorption: Despite its stiffness, the internal spider acts as a buffer. It absorbs torsional ripple and shock loads from large motors, preventing resonance that could damage heavy mechanical components.

Benefits of GS 55 Couplings

Massive Torque Capacity: Delivers up to 685 Nm (Red spider) and peak torques over 1,300 Nm, providing the strength needed for heavy press feeds and machining centers.
Precision Rigidity: The steel hubs and pre-stressed spider ensure high torsional stiffness, which is critical for maintaining accuracy in moving heavy masses.
Electrical Isolation: The polyurethane spider electrically isolates the driving and driven shafts, preventing ground loops from interfering with feedback devices.
Blind Assembly: The axial "plug-in" design allows for easy installation in difficult-to-reach areas, such as inside large motor flanges or gear housings.
Versatility: Available with different spider hardnesses (e.g., 64 Shore D for maximum stiffness) to tune the coupling for specific dynamic requirements.

Typical Applications

The GS 55 is found in the heaviest precision industries:

Large Gantry Mills: Axis drives for massive aerospace or automotive machining centers.
Metal Forming: Servo-driven mechanical presses and heavy bending brakes.
Printing Industry: Main drives for large-format offset printing towers.
Plastic Processing: Electric drives for large injection molding clamping units.
Test Rigs: Heavy-duty dynamometers and wind turbine component testing.

Summary

The GS 55 Backlash-Free Coupling is the heavy-weight champion for precision motion control. With a nominal capacity of nearly 700 Nm and zero backlash, it offers the uncompromising strength and rigidity needed for the largest industrial servo applications. Its ability to dampen vibrations while delivering massive power makes it the reliable choice for heavy engineering automation.