Installation and Maintenance

lnfluence of speed and deflection angle

Speed
The permissible speed of the universal joint shaft is influenced by the following parameters:

size of the shaft

widening of the yokes due to centrifugal force

quality of balancing

true running of the connected flanges

deflection angle during operation

length of the shaft

Speed x deflection angle
Theoretical considerations and observations of various applications have shown that certain mass acceleration moments of the centre part of the shaft must not be exceeded if a quiet running of the shaft drives is to be achieved. This mass acceleration moment depends on the speed n, the deflection angle ß and the mass moment of inertia of the centre part of the shaft.

The mechanically possible deflection angle for each joint depends on the size of the shaft. Owing to the kinematic conditions of the universal joint described before, the practical deflection angle must be limited in relation to the rotational speed.

The following table shows the max. speeds and the max. permissible values for the product

of the various shaft sizes for a moment of inertia of the centre part according to a shaft length of approx. 1500 mm.
When approaching the critical rotational speed and in the light of the demand of maintenance of balance quality (see Balancing of Propeller shafts ) , it may be necessary to reduce the rotational speed.

Joint size

n max.

[1/min.]

(n x ß) perm.

[°/min.]

2015
2020
2025
2030
2035
2040
2045
2047
2050
2055
2060
2065

6 000
6 000
6 000
6 000
5 600
5 000
4 700
4 500
4 500
4 500
4 100
3 900

27 000
26 000
24 000
22 000
21 000
20 000
19 000
19 000
19 000
18 000
17 000
17 000

Since the quiet running of the universal shaft in practice also largely depends on the installation conditions, the n x ß values shown in the table can only be regarded as a guidance. Slightly higher values are possible. In case of favourable spring and mass conditions the values may be exceeded by up to 50 %.

Transverse whirling speed
Universal shafts are flexible elastic units, which must be calculated considering the bending vibrations and the transverse whirling speed.
For reasons of safety the max. perm. operating speed must be sufficiently below the transverse whirling speed.

The diagram on the end of this page shows the transverse whirling speeds of the varbus shaft sizes depending on the operating lengths and the tube dimensions shown in the catalogue.

The diagram values apply to normal installation conditions with a supposed distance of the centre point of the joint shaft from the adjacent bearing equal to 3 x M and a rigid suspension of the connected units.

In order to achieve a safe and quiet running behaviour the max. perm. operating speed, i.e. including a possible excess speed, must not exceed 80 % of the transverse whirling speed shown in the diagram.

If the permissible speed is exceeded, the length of the universal shaft must be reduced or an intermediate bearing must be provided.

The following diagrams only refer to universal shafts of the standard design. For special designs with greater length compensations than normal or with other alterations reducing the flexural strength a special calculation of the critical speed is required. In this case please ask our advice.

Transverse whirling speed of cardan shafts dependent on operating length