Asia Helical Gearbox, High Performance Gearboxes Producer  
  GUIDE TO SELECTION OF GEARBOXES  
  The basic factors to consider in choosing a gearbox are the following:
 
 

SPEEDS n1; n2

These are fixed by the type of motor used (n1) divided by the selected gearbox ratio (i) with the resultant output speed (n2).
Carefully analyzing the kind of service in order to choose the most suitable gearbox, it is possible to have input speeds higher than 1400 RPM.
If it is possible, it is better to have input speeds at or lower than 1400 RPM.
For the gearboxes type MAS, RAP, input speed n1 up to 3000 RPM are admissible, unless otherwise indicated.
Care should be taken to check the maximum power admissible 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, that certain tests have to be made according to the transmitted power therefore we suggest that this should be indicated when ordering.

In the table below we have indicated the coefficients used to find the correct transmissible power according to the input speed (n1) with service factor = 1

 
 
MAC - MAS - RAP
n1
RPM
Power
1400 HP1 KW1
1800 HP1 * 1.3 KW1 * 1.3
2200 HP1 * 1.4 KW1 * 1.4
2800 HP1 * 1.8 KW1 * 1.8
 
  N.B. the values of HP1 and KW1 must be taken from the tables where input speed (n1) is indicated to be 1400 RPM.  
   
  POWER KW1 ; HP1  
  The power indicated in the catalogue refers to the input of the gearbox.
The output power is calculated as follows:

 
   
  OUTPUT TORQUE M2  
  The values of M2 indicated in the catalogue are true because for their calculation we have considered the gearbox's efficiency.
These values must be equal higher than the torque necessary to operate the machine they are selected for.
 
   
  SERVICE FACTOR s.f.  
 

Since the gearboxes are often subjected to variable loads, it is better to choose the group with an adequate coefficient (service factor).
This factor allows selection of the gearboxes with characteristics necessary for the kind of service required.

The table below indicates the service factors to consider when you choose the gearboxes.

 
 
Service Factor s.f. For Gearboxes Series MAS - RAP
Service characteristic Type of load Daily work
< 0.5 h 0.5 ÷ 2h 2 ÷ 10h 10 ÷ 24h
Continuous or intermittent service with less than 10 starts/hour. Normal 0.8 0.9 1 1.25
Light loads 0.9 1 1.25 1.5
Heavy loads 1 1.25 1.5 1.75
Intermittent service with 10 or more starts/hour. Normal 0.9 1 1.25 1.5
Light loads 1 1.25 1.5 1.75
Heavy loads 1.25 1.5 1.75 2
 
  RATIO i  
  It is a characteristic of the gearbox and identifies it self in the formula:  
  In the helical gearboxes the ratios indicated as a whole number are generally rounded. To get the exact values, please revert our technical department.  
     
  GEARBOX EFFICIENCY  
  You can calculate: or  
  from  
     
  The figures specified in the catalogue.
Conditions like temperature, type of lubricant, speed, gear characteristics, etc., subject the gearbox to certain variables; therefore for the calculation of torque M2 indicated in the catalogue the efficiency of the groups after running- in has been considered.
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 gearbox it is necessary to have further information like:

  • Type of machine to operate
  • Ambient temperature
  • Environment (dusty , dump , ice , tropical , etc...)
  • Drive motor (type and characteristics)
  • Type of transmission between drive motor and the gearbox (direct, through coupling, clutch, variator)
  • Shafts disposition
  • Values of radial and/or axial loads and knowledge of their causes
 
  CHOICE OF THE GEARBOXES  
  When you have all the necessary information you can choose the gearboxes in the relative tables 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 is the efficiency of the gearbox itself. Generally you should avoid the installation of motors with power higher than that required because it can subject the gearbox (and also the connecting gears) to shocks and stresses, which can jeopardize its life span, since the dimensions have been made according to the power absorbed by the machine and not according to the power installed. Besides it is also more expensive both for energy consumption and for the electrical system.
You can use higher powers only if it is certain that they will never be required for particular operating conditions (ex.: with an high number of connections).
The gearboxes admit momentary overloads like 100% of the nominal torque, obviously with a limited number of connections.
If you have higher values, you must choose the gearbox with a torque M equal to 50 % of the overloads value, multiplied by the service coefficient concerning the kind of application.
 
     
  CHOICE OF THE GEARED MOTORS  
 

When s.f. = 1, the selection of the geared motors can be made directly from the relative tables of GEARED MOTORS CHARATERISTICS considering:

or
If s.f. 1 it would be better choose from the relative tables of GEARBOXES CHARACTERISTICS considering:

or

The geared motor can be supplied complete with the motor (in this case you must specify its characteristics) or with motor mounting flange (abbr. P.A.M.); in this case you must specify the size of the motor, which will be coupled.

 
     
  RADIAL AND AXIAL LOADS  
  It is necessary to check that the eventual radial and/or axial loads are not higher than the values indicated in the relative tables.(Expressed in daN)  
 
n2/1'
300 250 200 150 100 80 60 40 20
AS 25 118 138 149 164 187 201 222 254 320
AS 30 203 237 256 281 322 346 382 437 550
AS 35 320 338 362 394 445 474 518 585 720
AS 45 422 446 477 519 586 625 683 772 950
AS 55 667 704 754 820 926 987 1080 1220 1500
AS 60 978 1033 1106 1202 1358 1447 1583 1789 2200
AS 80 1378 1455 1558 1694 1914 2040 2230 2520 3100
AS 90 1867 1972 2110 2295 2593 2764 3022 3415 4200
 
  MOUNTING POSITION  
  It is important to indicate the mounting position so that the gearbox can be properly lubricated. in the chapters concerning the different types of gearboxes we have indicated when it is not necessary to specify the mountings position.  
     
  LUBRICATION  
  Before use, the gearboxes with oil lubrication must be filled with the right quantity of oil by the customer. For this purpose the gearboxes are supplied with level, drain and breather plugs. Please specify the proposed mounting position to facilitate correct positioning of the plugs.
 
 
Type of Lubricant Gearboxes Type
1 Liter MAS 25 - 110
1.5 Liter MAS 30- 130
1.5 Liter MAS 35 - 110
2.5 Liter MAS 45 - 155
3 Liter MAS 55 - 175
5.5 Liter MAS 60 - 210
5.5 Liter MAS 90 - 310
 
 

Mineral lubricants can be used with an ambient temperature between 0 °C and +30 °C.
If the ambient temperature is greater than + 30/35 °C, then an oil with an higher viscosity must be used.
If the ambient temperature is less than 0 °C then an oil with a lower viscosity must be used.
The synthetic lubricants can be used with ambient temperature from - 10 °C to +40 °C (grease) and from -30 °C (- 25 °C for Blasia S) to +50 °C (oil).

 
     
  INSTALLATION  
 

For the installation of the gearbox the following guidelines should be observed:

  • The gearbox to be securely bolted to a rigid base to avoid vibrations

  • If shocks, extended overloads or jamming is expected, hydraulic couplings, torque limiters, clutches etc. should be fitted.

  • If the gearbox is to be spray- painted use masking tape to shield the oil seals to prevent damage to them by the paint

  • Any gears, sprockets or pulleys being fitted to the input or output shafts must have their bores machined to ISO H7 tolerance. The shafts are provided with threaded hole to facilitate the use of tie - rods with back plate and nut to push on the gears or sprockets being fitted

  • In order to avoid the oxidation and the possible seizing of the above parts, before assembly clean both contact surfaces and apply water repellant grease or similar material

  • Bore of hollow shaft of gearbox has tolerance H7; all shafts being fitted usually are machined to h6.
    If required for the application an interference fit (H7- J6) can be used

  • Before starting the machine be sure that the lubricant level is correct for the mounting position of the gearbox and the lubricant viscosity is correct for the kind of load
 
  MAINTENANCE  
 

When the gearboxes are lubricated with synthetic grease no further maintenance is required when the gearboxes are lubricated with mineral oil the following procedure is recommended:

  • After the first 5001000 hours running, change the oil, preferably washing out
    the interior of the gearbox
  • At regular intervals check the lubricant level and change the oil after 4000
    working hours

If the gearbox is lubricated with synthetic oil you have , to change the oil after 8000 working hours. When the gearbox is standing for a long time in a very damp environment it is better to fill it completely with oil; naturally the lubricant level must be restored when the gearbox is put back into operation