Couplings & Drive Shafts

The selection of coupling type depends on the installation and the type of misalignment. The three main types of misalignment encountered are:-

• Angular Misalignment is usually present to some extent on all applications, typical values 1° - 2°. Sometimes higher values are necessary
• Parallel (Radial) Misalignment is also nearly always present. A well aligned installation might have values below 0.25 mm
• Axial Misalignment (End Float) sometimes caused by thermal expansion or as a result of machine design

Other considerations include:

• Backlash Free Couplings are either one part couplings or have bolted joints. These are effective for precise positioning and to avoid wear on reversing drives.
• Torsional rigidity of couplings depends on the joining method. Types with rubber or plastic elements can be considered as torsionally soft and will have an amount of twist at rated torque.

Procedure:

• Decide if the coupling should be torsionally soft or rigid.
• Consider whether a small amount of backlash is acceptable.
• Calculate the required coupling torque.
• Make a provisional selection.
• Check that the coupling’s maximum speed is sufficient.
• Check that the coupling’s dimensions are acceptable.

Contact Power Jacks with your order or technical enquiry

Select Drive Shaft Diameter
Select a standard drive shaft from the drive shaft table and check its torque rating and angle of twist rating against the application requirements.

If Transmitted Torque (Nm) < Maximum Drive Shaft Torque (Nm) & If Acceptable Angle of Twist (Deg.) for shaft length < Rated Angle of Twist for Drive Shaft (Deg.) then drive shaft diameter selected is acceptable.

Check Drive Shaft Critical Speed
For the unsupported shaft length calculate the drive shaft critical speed for the support conditions required.

If Shaft Speed (rpm) < Drive Shaft Critical Speed (rpm) then drive shaft selection and configuration is acceptable.

• Maximum misalignment values are extremes and should not be combined. As operating misalignment approaches the maximum, torque and power ratings should be reduced to maintain life
• The maximum axial misalignment values apply when the coupling is aligned. If axial misalignment greater than the listed maximum is required, consult Power Jacks
• The inertia values includes shafts through the bores
• When ordering please quote the coupling size and type, specify the bore and keyway sizes, and advise if puller holes or set-screws are required
• For maximum performance the screw jacks, actuators, gearboxes, motors and shafts should be carefully aligned
• Imperial (Inch) couplings on request