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Asia
Helical Gearbox, High Performance Gearboxes Producer |
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GUIDE
TO SELECTION OF GEARBOXES |
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The
basic factors to consider in choosing a gearbox are the following:
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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
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MAC
- MAS - RAP |
n1
RPM |
Power
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1400 |
HP1 |
KW1 |
1800 |
HP1
* 1.3 |
KW1
* 1.3 |
2200 |
HP1
* 1.4 |
KW1
* 1.4 |
2800 |
HP1
* 1.8 |
KW1
* 1.8 |
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N.B.
the values of HP1 and KW1 must be taken from the tables
where input speed (n1) is indicated to be 1400 RPM. |
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POWER KW1 ; HP1 |
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The power indicated in the catalogue refers to
the input of the gearbox.
The output power is calculated as follows:
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OUTPUT TORQUE M2 |
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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.
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SERVICE FACTOR s.f. |
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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.
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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
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1
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1.25
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Light
loads |
0.9
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1
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1.25
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1.5
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Heavy
loads |
1
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1.25
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1.5
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1.75
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Intermittent
service with 10 or more starts/hour. |
Normal |
0.9
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1
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1.25
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1.5
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Light
loads |
1
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1.25
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1.5
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1.75
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Heavy
loads |
1.25
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1.5
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1.75
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2
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RATIO i |
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It is a characteristic of the gearbox
and identifies it self in the formula: |
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In the helical gearboxes the ratios indicated
as a whole number are generally rounded. To get the exact values, please
revert our technical department. |
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GEARBOX EFFICIENCY  |
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You can calculate: or
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from |
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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.
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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
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CHOICE OF THE GEARBOXES |
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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:
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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.
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CHOICE OF THE GEARED MOTORS |
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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.
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RADIAL AND AXIAL LOADS |
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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) |
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n2/1' |
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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 |
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MOUNTING POSITION |
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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. |
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LUBRICATION |
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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.
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Type
of Lubricant |
Gearboxes
Type |
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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 |
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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).
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INSTALLATION |
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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
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MAINTENANCE |
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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 500
1000
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
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