BELT POWER TRANSMISSION. XCIII. 
small diameter, whereas the use of a pulley of large diameter 
would enable the belt tension to be proportionately less. The 
large amount of power absorbed in line shafting, may be traced in 
a great measure to a belt tension which may be modified by the 
general use of larger pulleys. 
Jockey pulleys are found to work most satisfactorily on the 
loose side, which should always be uppermost. Such pulleys 
should preferably be hinged, rather than sliding in guides, and 
be set about one-third of the distance between centres near the 
smaller pulley. | 
In connection with high speed driving, the use of crowned 
wr 
pulleys with more than }” crown for each 12” of width is 
undesirable, any inequality of the belt resulting in chasing across 
the pulley. This chasing may be so serious as to affect the driven 
machine, and is due (1) to unequal local tension in the material 
composing the belt, (2) unequal density. In the first case the 
movement across the pulley face will be noticed at quite low 
Speeds ; in the second it will become evident as the speed rises 
towards maximum, ‘being due to centrifugal effort of the denser 
part of the belt to reach the crown. In the case of } crossed belts 
driving a vertical shaft the crown should be at least three times 
that stated. 
The life of a main leather-belt, working under proper conditions 
of stress and cleanliness, has been variously estimated from twenty 
to thirty years. But a passage through the various factories of 
N.S.W. will show that belting generally does not receive the 
attention it deserves. Its very simplicity leads to neglect. Belts 
should be cleansed from adherent dust and grease at least twice 
yearly, and, if dirty, be scoured with soda and water. They should 
receive likewise every six months, or oftener, a dressing of boiled. 
linseed oil or castor oil, or emollient preparations for the purpose. 
On no account should resin or such substances be applied. The 
pulleys should be kept clear of dust and grease. The author has 
seen many cases where the pulley face is no longer visible through 
such accumulations. When anew belt is put on, it should, before 
