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                      MarMotion. High-precision rotary stroke bearings                                                                            +

                                                                                                                                    45 Mahr

5. Computation of the Rotary Stroke Bearing

After P10 has been calculated, a comparison with the specific rated load C10 (tables in Fig. 27 and 28) reveals whether the rotary
stroke bearing is correctly dimensioned.

Requirement: P10  C10

The deflection A is calculated as described in section 5.2.2.

Computation example:

To be determined: Load of the most heavily loaded ball zone

Given:     Radial force acting on one side
Solution:  PR = 1000 N
           l = 300 mm

           Contact length e = 200 mm

           Distance between the ball zones Ii = 100 mm

           P10 = g · M + h · PR
           M = PR · I

               = 1000 N · 0.3 m = 300 Nm
           g = 2 m-1 (from diagram Fig. 25)

           h = 0.11 (from diagram Fig 26)
           P10 = 2 m-1 · 300 Nm + 0.11 · 1000 N
           P10 = 710 N

5.3 Specific rated load C10

Definition

The specific rated load C10 is the radial loading capacity of ball operating zone 10 mm long of a MarMotion high-precision
rotary stroke bearing, taking into account the nominal diameter dw, preloading value v and cage type N 500, N 501, N 511 or N 502.
In section 5.2, the specific radial force P10 was calculated from the load of the rotary stroke bearing.
The following must always apply:

P10  C10

C10 depends on:
Nominal diameter dw, ball diameter, number of balls, preloading value v and the following criteria: The surface pressure at the contact
points between the rolling elements and the rolling faces of the shaft and the bush (Hertzian stress); and the elastic deflection of the
shaft axis from the "0" position, which is determined by the rigidity R10 of a 10 mm ball zone.
The specific rated loads C10 of Mahr ball cages N 500 and N 501 set out in the tables (Fig. 27 and 28) were defined to
justify our claim of manufacturing "high-precision rotary stroke bearings".

The elastic deviation under a load P10 = C10 should not be more than half the preloading value v.
dR,max = 0,5 v [m]
The quoted values for C10 and R10 are given as a function of the preloading value v in such a way as to ensure that this condition is met.
The rigidity R10 [m/N] is the axial deflection of a 10 mm ball zone under a radial load of 1 N.
The deflection of a 10 mm ball zone is computed from:

A10 = P10 · R10 [m]

Method I
The first step is to determine the specific radial force P10. The required nominal diameter dw and value for C10, which must be greater
than or equal to the value of P10, are then read off from one of the tables.

Method II
From the known nominal diameter dw, C10 is read off from one of the tables and then used in further computations as the
permissible specific radial force P10.

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