To size universal drivelines properly, various conditions and factors must be considered. In view of the multitude of possible applications, exact, generally valid rules cannot be provided. The following information is therefore used for the first rough determination of size. In case of doubt, we will gladly compute the required joint sizes for you and, in this context, we like to refer to the technical questionnaires.

The max. permitted torques Mdmax stated for the individual drive-shaft sizes apply normally only for short-term peak loads.
Mdnom: Nominal torque for pre-selection on the basis of the operating moment.
Mdlim: Limit torque that may be transmitted temporarily from the universal-drive-joint at limited frequency without functional damage. The respective permissible torque has to be calculated individually depending on the remaining operating data, such as shock loads, angle of deflection, rotation,etc. (See item 6.2 and 6.3)

Depending on the type of power input or installation, a driveline can be subjected to shock loads considerably above the rated torque. To take those into account, shockservice factors must be implemented. Following are some shock-service factors for the most common drivesOf course, not only the drives, but, in many instances, also the driven equipment is responsible for shock loads. Because of the magnitude of different possibilities, general data valid for every use cannot be supplied.

The decisive factor with regard to life expectancy of universal drivelines are usually the joint bearing. Therefore, in order to determine the individually required joint size, the life ex-pectancy diagram shown later on should beused. This diagram allows to:
a) determine the theoretical life expectancy of a selected driveline as a function of prevailing operating conditions, or
b) to determine the required joint size for a given life expectancy.

In this case, the rated input torque is multiplied by the appropriate service (shock) factor and the Md such obtained entered in the following diagram. Other factors, such as correction - or deflection angle factor do not have to be considered since they are already incorporated in the diagram.

On machines or vehicles with changing ope-
rating conditions, at first, the individual life expectancy values (for each condition) must be determined from the diagram. Then the overall life expectancy LhR can be calculated as follows:
q1, q2 = time share in [%]
Lh1, Lh2 expressed in 103 [Hours]

In view of the multitude of applications, it is not possible to determine the suitability of a driveline by tests. Therefore, the selection and analysis of the required joint size is done by calculations. These are based on the compu-tation of the dynamic load carrying capacity of full rotation needle - and roller bearings ac-cording to ISO recommendation R 281. The life expectancy diagrams shown in the catalogue are based on this recommendation and also on an equation formula especially suited for ob-taining nominal life expectancy on universal joints. The thus obtained life expectancy lists the hours of operation that will be reached or exceeded by 90% of a larger number of equi-valent universal joint bearings.

There are also methods of obtaining the modified life expectancy. In this case varying survival probabilities, material quality and operating conditions are taken into account. The present technical know how does not allow statements to be made about variations in life expectancy-performance resulting from diffe-rences in steel quality (grain, hardness, impu-rities). For this reason, no guidelines have been set in the International Standards.

All pertinent operating conditions, such as operating temperature, lubrication intervals, the type of grease used and its viscosity in operation, must also be considered. Since these factors vary from case to case, it is not possible to determine the modified life expectancy and accordingly, a life expectancy diagram valid for universal use.

The two following life expectancy diagrams will allow you to roughly determine the nominal life expectancy.

If the deflection angle is smaller than ß = 3°, ß = 3 should be used. Otherwise, the obtained result will be less accurate.

If it is necessary to determine the life expectancy accurately, kindly consult the ELBE Engineering Department.

As shown in 2.3 by taking certain precautions, a constant output can be obtained on a universal driveline. The center part, however, still retains a non-uniform motion; it is subjected twice per revolution to an acceleration and deceleration. The resulting acceleration torque caused this way is a function of the mass moment of inertia of the driveline‘s center part as well as of rpm and deflection angle. When regarding smoothness of operation and wear, the product of rpm and deflection angle should not be too high. For use in general mechanical engineering, appropriate guide values can be taken from the diagram below, which is designed for universal drivelines having a standard tubing of up to 1500 mm length.
For vehicle drive trains, these guide values must often be exceeded. Here, at most, up to 1.5 times of the diagram value can be permitted.

As shown in 5.1, the center part of the angled driveline, when transmitting torque, is being stressed periodically in bending by additional moment MZII. This incites the center part to vibrate. If the frequency of this bending vibration approaches the natural frequency of the driveline, maximum stress in all components, buckling of the shaft and development of noise will result. To avoid this, long and fast running drivelines must be checked for critical bending vibration speeds. The critical, first order bending vibration speed of a driveline employing tubing can be roughly calculated as follows:

D = Tubing-outside diameter [mm]
d = Tubing-inside diameter [mm]
L = Center part length in [mm]



Drivelines are used in the subcritical zone only. For reasons of safety, it must be ensured that the maximum operating speed is far enough away from its system‘s resonance (critical) speed. Therefore, the following applies:

The critical bending vibration speed of a dri-veline is, as can be seen from the critical rpm formula, a function of tubing diameters and length of center part. By going to larger tubing diameters, the critical speed of a driveline can be increased. However, the diameter increase must remain within defined limits since a certain relationship between tubing dimensions and joint size must be adhered to.

The dimension sheets of the different driveline models list the possible tubing dimensions for each size. In all the cases where a single driveline is insufficient, multiple arrangements with intermediate bearings must be used.

For determining the required tubing diameter when maximum operating speed nmax and center part length L are given.