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TBIS 15194:2019
4.3.15.6 Seat-post – Fatigue test
4.3.15.6.1 General
In the following test, if a suspension seat-post is involved, the test shall be conducted
with the suspension system adjusted to give maximum resistance.
Conduct the test in two stages on the same assembly as per 4.3.15.6.2 and
4.3.15.6.4.
4.3.15.6.2 Requirement for stage 1
4.3.15.6.2.1 Seat-post without suspension system
When tested by the method described in 4.3.15.6.3, there shall be no visible cracks
or fractures in the seat-post, nor any bolt failure.
For composite seat-post, the peak deflection of seat-post during the test shall not
increase by more than 20 % of the initial value.
4.3.15.6.2.2 Seat-post with suspension system
When tested by the method described in 4.3.15.6.3, there shall be no visible cracks
or fractures in the seat-post, nor any bolt failure. The design shall be such that in the
event of failure of the suspension system, the two main parts do not separate nor
does the upper part (i.e. the part to which the saddle would be attached) become
free to swivel in the lower part.
4.3.15.6.3 Test method for stage 1 (fatigue test)
4.3.15.6.3.1 Test method for stage 1-1 (fatigue test)
A seat post shall be inserted to the minimum insertion depth in a suitable fixture
with a representative seat collar and clamped to the manufacturers recommended
torque. The seat post shall be fixed at an angle of 73° from horizontal, as shown in
Figure 52.
Secure an extension-bar to the saddle attachment point by the appropriate
attachment fitting such that the bar extends rearwards and downwards at an angle
of 10° below the horizontal to permit the application of a vertical test force at a
distance of 70 mm from the centre of the saddle-clamp where the centre-line of the
clamp intersects the axis of the bar, as shown in Figure 52.
Apply a repeated, vertically downward, dynamic force of F3 to the point described
above and shown in Figure 52 for 120 000 cycles. The forces are given in Table 32.
The maximum test frequency shall be maintained as specified in 4.3.1.5.
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