Page 45 - TBIS_79010-2019_(EN)_1nd

TBIS 79010:2019

Annex B
(informative)
Dummy fork characteristics

The test forks shall be designed to mount in a manner similar to the original fork, or
in a manner using typical procedures (see Annex B).

The test forks when mounted shall be the same length (axle to race), L, as the
longest fork designed for use with the frame.

The deflection of the test fork shall be measured in the direction of the force
application at the front axle centre, from the resulting application of a vertical force
of 1 200 N. The fork shall be secured in a horizontal position by constraining the
steerer tube by means of a false head tube (with bearings) equal to 150 mm in
length. The steerer tube shall be secured as in a bicycle with the crown race seat

adjacent to the false head tube lower bearing assembly. (See Figure G.1 in Annex G).

a) The deflection ratio, Dr, for the Test fork for the Horizontal Loading Fatigue test
and the Vertical Loading Fatigue test shall not exceed the value of 1,0 when
computed as follows:

where
Dr is the deflection ratio;
K 1 is 1 417, a constant;

L is the fork length, expressed in millimetres;
δ is the deflection, expressed in millimetres.

EXAMPLE

Fork length L = 460 mm
Deflection δ = 6,85 mm, from which
Deflection ratio Dr

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