Features of mk Track Roller Assemblies
Design of the Track Rollers
The indicated static load carrying capacities can
be used as a guideline for the preliminary selection
of track rollers. These values are the maximum
allowable unit loads and include a static safety factor
s0 = 4 in relation to the plastic deformation of the
roller bearings within the steel track roller. For stainless
steel components, these values must be reduced
The load values shown for the axial load (Fy) and
radial load (Fz) are for moment-free loads. The allowable
moments are the result of opposing offset
Combined loads must be verified separately. A combined
load is a single point load which, with a 50
mm offset for example, also introduces a moment.
Careful consideration must be given to combined
loads which cause torsion.
When arranging track rollers, it is important that the
track rollers only transfer compressive loads in the
radial direction. The centric track rollers are especially
suitable for handling radial loads, especially
in the Fz direction. The centric track rollers are prevented
from twisting by using a steel bushing.
Care must be taken to ensure that the track rollers
are installed in an unloaded condition. In most
cases, readjustment of the eccentric track rollers
causes premature wear. For “normal” applications
(up to a = 3 m/s2), the track rollers should be set so
that they rotate as they travel along the track but you
can still prevent this rotation by placing your thumb
and index finger on the circumference of the roller.
For applications requiring a speed of over a =
3 m/s2, the track rollers require further pre-tensioning,
and you can then no longer manually prevent
the rollers from rotating. As an additional safety
measure, we recommend securing the eccentric
bushings with adhesive to prevent them from slipping.
To prevent corrosion and increased abrasion,
sufficient lubrication must also be used.
When confirming the suitability of particular track
rollers, a distinction must be made between static
and the dynamic loading. Static loads are loads that
are transferred at the contact point between the rod
and the track roller while the roller is not rotating.
That is to say that dynamic loads, or loads along
other axes, must also be considered.
It is helpful to first confirm the static and then the
dynamic load calculations. The allowable static
axial and radial track roller loads and the static and
dynamic safety factors of the most highly loaded
rollers must be confirmed. The maximum track roller
loads are technically considered mechanical contact
loads (supported loads).
The static safety factor and dynamic safety factor
are derived from the relationship between the allowable
load capacity Cw and the available equivalent
Up to v = 3m/s and a = 3 m/s2, full load capacity of
the track rollers with sO ≥ 4 and 2 < sD ≤ 5.
For high dynamic loads with a > 10 m/s2 and speeds
of up to v = 10m/s, the load values must be reduced.
Linear Units and Modules