Crescent single reduction gear units are
robust construction, combining high standard of strength, wear resistance
.and thermal ratings in compact design. This enables economic mass
production, comprehensive maintenance of stocks, favorable delivery period,
ease of servicing. Computer aided sizing of gear based on geometric
progression has result in optimization of gear geometry for high efficiency
and load carrying capacity.
Wherever applicable, British as
well as Indian standards are used. Worm conforms to case hardening alloy
steel, worm wheel conforms to phosphor-bronze PB2-C as per British Standard
B.S. 1400, while gear case conforms to C.I. grade FG 220 and for heavy duty
FG 250, Indian standard I.S. 210.
Gear case is of streamline design,
rugged in construction, made of close grain cast iron. It is completely
oil-tight, dust proof and capable of being installed in the open without a
separate cover. The face and bore are accurately bored and machined on
latest precision machines to ensure perfect alignment and
The worm is made of case hardening
alloy steel, carburised, ground and polished and is integral with the shaft.
Bearing journal are accurately ground. Worm wheel is made of centrifugally
cast phosphor-bronze rims, shrink fitted and brazed with C.I centers. Worms
are generated on special purpose worm milling machine machines. Gas
carburised and ground on automatic work grinders.
Worm wheel are hobbed on precision hobbing machine with high accuracy hubs.
Each and every wheel is checked to match with the master worms to ensure
The worm and worm wheel are
supported on ball or roller anti friction bearings of ample margin of safety
to allow adequate journal as well as thrust loads. Overhang loads arising
out of sprocket Or pinion drive are generally permissible because the gear
case and bearing are designed for this duty. However, complete details
should be given to us for confirmation. In case of heavy overhang loads, as
extra roller bearing can be provided.
The wheel shaft are made of high
tensile carbon steel. It is of larger diameter to carry the torsional as
well as bending loads which may be induced by overhang drives.
Lubrication to gears and bearings
is by splash of oil from the sump. No special care is required except for
the occasional topping up of oil to the required level. A large oil
filter-cum- breather and inspection cover is provided together with the
drain plug and ventilator. Neoprene lip-type oil seals are fitted on input
and output shaft.
For very low input speed below 50 rpm. And heavy loads in size larger than
14" size forced lubrication is required. In such case Crescent must be
Air-cooling is effected by means of
standard poly-propylene or metal fans which direct a continuous flow of air
over the ribbed surface of the gear unit. The fan is designed to operate in
both direction of rotation, and is so arranged in conjunction with the
ribbing on the gear unit as to allow maximum heat dissipation.
Crescent Sprag type hold back can
be fitted on all sizes of gears to prevent reverse rotation. In case where
hold-back is required, the direction of rotation of the shaft should be
The ratings indicated in the
catalogue holds good for 12 hours of continuous running under uniform load
being driven by electric motor. They give minimum gear life of 26,000 hours,
subject to limitation of maximum oil temperature of 100 C under full load,
20 C ambient.