RATIO i
It is a characteristic of the gearbox and identifies itself in the formula In the helical gearboxes the ratioes indicated as a whole number are generally rounded.
To get the exact values, please revert our technical department.
From the catalogue figures you can calculate:
Conditions like temperature, type of lubricant, speed, gear characteristics, etc., can affect efficiency; therefore efficiency after running-in has been considered for the calculation of torque M2 in the catalogue.
The graph below indicates the approx. value of the efficiency pointing out the difference between the gearboxes with 1, 2, 3 reductions and the worm-gearboxes.
For the correct selection of gearboxes it is necessary to have further information like:
- Type of machine to operate
- Ambient temperature
- Environment (dusty, damp, ice, tropical, etc...)
- Drive motor (type and characteristics)
- Type of transmission between drive motor and gearbox
- (direct, through coupling, clutch, variator)
- Shafts arrangement
- Values of radial and/or thrust loads and their causes.

SELECTION OF THE GEARBOXES
Having all the necessary informations you can choose the gearboxes in the table of GEARBOXES CHARACTERISTICS where the values kW1; HP1; M2; 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 ?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 according to the installed power.
Besides it is also more expensive both for energy consumption and for 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.