Product Selection Guide


The basic factor to consider in selecting a gearbox are the following :

-input power KW1;HP1

-output power KW2;HP2

-output torque (daNm) M2

- input speed (rpm/min.) n1

-output speed (rpm /min.) n2

-ratio i

-gearbox’s efficiency ηd

-service factor s.f.

SPEEDS n1;n2 

These are determined by the type of motor (n1) divided by the required gearbox ratio (i) with the resultant output speed (n2). Carefully analyzing the duty conditions in order to choose the most suitable gearbox, it is possible to have input speeds higher than 1400 rpm. If possible, it is better to have input speeds of 1400 rpm or lower. For the gearboxes type RAP,RAO, RAN and RVF, input speed n1 up to 3000 rpm are admissible, unless otherwise indicated. Care should be taken to check the maximum admissible power for the gearbox. It should also be considered that for all medium and large size gearboxes where a low ratio (less than 10:1) and high input speed is required, tests have to be made according to the transmitted power therefore we suggest this should be indicated when ordering. In the table below we have indicated the coefficients to be used to find the correct transmissible power according to the input speeds (n1) with service factor(F=1)





For worm gearboxes of VF and VF/VF series we recommend that continuous and intermittent duty cycles are clearly differentiated as follows: For continuous duty we suggest that you contact our application to ensure reliability of the gear- boxes under these continuous. In the case of intermittent duty, selection can only be using the coefficients indicated in the table below

N.B. The values of HP1 and KW1 must be taken from the tables where input speed (n1) is indi- cated to be 1400 rpm.




The power ratings indicated in the catalogue referred to the input of the gearbox. The output power is calculated as follows: KW2(HP2)=KW1(HP1)×ηd



The values of M2 indicated in the catalogue are real because gearbox’s efficiency has been con- sidered in the calculation. These values must be equal to or higher the torque required to operate the machine.



Since the gearboxes are often subjected to variable loads, it is better to select the unit with an adequate coefficient(service factor). This factor allows selection of the gearboxes with the right characteristics for the kind of service required. The table below indicates the service factors to be considered when selecting the gearboxes. For the worm- gearboxes you will find the service factors table in the chapter concerning VF series.



N.B. The above values must be multiplied by 1.2 in case of: - Combustion engine drive - Reversing operation - Instantaneous overloads



Having all the necessary information you can choose the gearboxes in the table of GEARBOXES CHARACTERISTICS where the values KW 1 ; HP 1 ; M 2 ; are calculated with s.f.=1. If you know the torque M or the power KW(or HP) required, you will find the gearbox with Where η d is the efficiency of the gearbox. Generally you should avoid the installation of motors with higher power than required because it can cause shocks and stresses which can jeopardize gearbox’s and other component’s life span, since the design has been made according to the absorbed power of the machine and not accord- ing to the installed power Besides it is also more expensive both for energy consumption and for the electrical system.You can use higher power, only if it is verified that it will never be required for particular operating conditions (ex.: with an high number of connections.) The gearboxes allow momentary overloads like 100% of the nominal torque, obviously with a limited number of connections. If you have higher values, you must select the gearbox with a torque M equal to 50% of the overload’s value, multiplied by the appropriate service factor for the application.



When s.f.=1, the selection of the geared motors can be made directly from the tables of GEARED MOTORS CHARACTERISTICS considering If s.f. ≠ 1 it would be better to use the tables of GEARBOXES CHARACTERISTIC S for the selec tion Once type of gearbox, ratio I and motor has been determined , please check if the motorsize (B5 or B14) is suitable for assembly on the gearbox according to the POSSIBLE ASSEMBLING tables.

We advise to purchase geared motors complete with electric motor: in this case we test and guarantee that the motor complies with the high standard of quality required for the good functioning of the unit.