Ringfeder RfN 4051 Light Shrink Disc, 125-500 mm

Light shrink disc for thin-walled hubs and medium torque

The RfN 4051 is RINGFEDER’s light series of shrink discs. It is a three-part disc, made to transfer low to moderate torque where radial space is limited: the pressure rings are narrow, so the unit needs very little room along the shaft, and RINGFEDER describes it as ideal for thin-walled hubs and shafts. A shrink disc replaces a keyed or splined joint with a friction fit. Tightening the screws draws the thrust rings together, which compresses a tapered slit inner ring onto the shaft and presses the outer ring onto the hub, while the disc itself stays out of the load path.

Torque is set by the screw tightening torque, which lets the same size serve different applications. The slit inner ring keeps forces and pressures on hub and shaft low, small tolerance errors are compensated, and the connection is suitable for static, dynamic and impact loads. With no keyway, hubs can be placed at any point or angle on the shaft.

Technical specifications

Selected sizes from the tech paper

For the 125 x 185 size the tech paper lists three shaft diameters (95, 100 and 105 mm) with torques from 10,550 to 13,800 Nm at different tightening torques, which is how one disc covers neighbouring shaft sizes.

Function values and what to check

The tech paper calculates the function values with the screws lubricated with MoS2 (total friction 0.1), the tapered cones lubricated with MoS2 (0.05), lightly oiled contact surfaces (friction 0.12) and a modulus of elasticity of 210,000 N/mm2 for hub and shaft. The shaft must be finished to Ra 3.2 um, and the table of maximum clearance S between shaft and bore applies. Hollow shafts and extra loads such as tension, thrust or bending have to be discussed with the RINGFEDER engineering team.

At a shaft of 100 mm the permitted clearance is 0.069 mm; above 180 mm shaft diameter it is 0.090 mm and at 400 to 500 mm it is 0.123 mm. Order by series, d and D, for example RfN 4051 420 630. Confirm before ordering: shaft diameter within the dw range of the chosen size, hub outside diameter and yield strength, and the torque and shock factor.

The tech paper lists each size for several shaft diameters, so state the exact shaft diameter, hub bore and required torque, including any shock factor, when requesting a quotation for this light series.

Documents and quotation

The attached PDF is the RINGFEDER tech paper for the RfN 4051 (10.2024). Drives that carry such hubs are listed under Electric Motors and Gear Units. Send shaft diameter, hub dimensions and torque for a size check.