rulmeca RDR BL3, Technical Manual

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TECHNICAL MANUAL FOR THE RDR BL3 - V1.1 DRIVE ROLLER Rev. 21/09/2018 page 10
4.3 Choosing the Drive Roller and its correct gear reduction ratio
The Drive Roller is a roller with a built-in 24 VDC brushless electric motor.
Once it is started up, the Drive Roller can start movement of the package on the conveyor.
In order to obtain suitable movement, the following information is required for a correct gear reduction ratio of the
built-in motor:
- the maximum weight on the zone driven by each single Drive Roller (M in kg)
- the transit speed of the package on the conveyor (V in m/s)
- friction coefficient between package and rollers to calculate the required torque settings (U).
- the Speed / Tangential force / (and torque settings) table on the Drive Rollers catalog.
In order to calculate the tangential force required to transfer the package, the driven area (r Drive Roller
connected by transmission system), defining the number of rollers connected to the Drive Roller.
With the above available (indispensable) data, apply the following formula:
F
t
= P x G x U
Where:
F
t
) Required tangential force (in Newton [N]).
P) Weight of the package (in kg).
G) Force of gravity (9.81 m/s
2
).
U) Revolving friction coefficient between package and rollers.
The revolving friction coefficient between package and rollers varies according to the material, hardness and
configuration of the contact surface of the packages.
Refer to the following friction coefficient values to make the calculation:
Steel, flat surface

0.03
Smooth PVC

0.04
Polymer section

0.05
Wood

0.05
Stiff cardboard

0.06
Soft cardboard

0.08
Stiff materials (of the same weight) require less tangential force to be moved whereas soft packages (again of the
same weight) tend to sag between one roller and the next one, requiring more tangential force to be moved.
In order to prevent the packages sagging between the rollers, with resulting jams or excessive torque required to
transport them, if the type of conveyed package cannot be changed, make the pitch between the rollers as small
as possible. In the case of packages or materials with feet or protrusions or very soft parts at the bottom, use a
support base, container or tray.
Once the tangential force (Ft) has been set that is necessary to move the package, after the package conveying
speed is known, refer to the tables for the single Drive Rollers to find the most suitable gear reduction ratio.