The Black Hills union and western stock review. [volume] (Rapid City, S.D.) 1904-19??, 1906-03-02
(Continued From Page d.

angle by two, and add one hundred ana
eighty degrees for large pulley, and subtract
from one hundred and eighty degrees for
small pulley.
To find width of belt required to transmit
given horse power, assuming sixty pounds
safe working stress, per inch OF width.
w - 55OH.P V.-Veldcity in feet per
minute for single belts. For double belts
take width equal to seven-tenths that OF
single.
To find weight of a belt, multiply length
in feet by width in inches, divide by thirteen
for single and by eight for double belts.
For rubber belts the best working con-
ditions are, large pulleys, high speed and
low tensions
Cotton stitched betting is now being Of
fered as substitute for rubber, but service
given bv it is far from satisfactory ], 1t. may
be Of value in few special cases, but for
general mill work it is undesirable and nh-
economical. One of the chief claims adj
vanced for this style Of beltingis it's sulta-
bility for elevator work, but the authors
experience with it for this purpose has been
directly the opposite to the claims made for
it, having found the life Of a good rubber
belt to be four times that of cotton one
under the same conditions; and the cost OF
the rubber is only twice that Of the cotton,
regardless Of time lost due to breakage OF
cotton belt.
In choosing belts for bucket elevators,
those reinforced on one side by an extra
layer of rubber are desirable, as the differ
ence in cost is more than compensated for
by the increased life Of the belt.
Ropes, both cotton and MANILA are at
present competitors of belts and gearing for
the transmission Of power; especially where
Il the power is great and the distance con-
siderable.
The chief claims advanced in favor of
ropes for main drives are quietness and
smoothness Of running, also their flexibility.
Any sudden change in the load being easily
taken up byst rope and given out again
in it's recoil, thus removing to large ex-
tent liability Of shock to engine and
pulleys.
Another advantage in favor Of this class
Of driving is the small danger Of sudden
breaking, for warning is generally given by
the rope in time to remedy it.
The chief disadvantages charged against
rope driving are loss Of power, due to fric-
tion and bending, also the unreliability of
the system in general: This latter objec-
ton however, is due more to faulty install
! lation than to any inherent defect in the
system itself, for where rope driving is in
stalled in accordance with good modern
practice, stoppage Of plant, due to faulty
driving need be no more frequent than
{ where other styles Of drive are used.
But the charge Of power loss is most SER
ious and authorities on the subject seem to
agree that this loss is from to per cent
. greater than with gear. Despite this loss,
ropes may often be used with advantage,
especially 50 where power is to be trans
mitted to 4 considerable distance, and the
8 installation Of a separate motor is not prac-
ticable. Also in cases, such as taking power
from q water wheel located where there is no
suitable site for buildings.
Ropes may be adopted to all sorts Of tor
tuous driving such as around q corner over
building or hill and for all kinds of port
able tools. Nbrous ropes are not suitable,
however, for extremely long distances; this
Is the field Of wire rope, nor do they seem
suitable for very short distances.
The four strand rope IS generally used for
nsmission purposes, both in cotton and
q manila, sizes vary from II to II inches.
Pulleys generally have Y shaped grove
With circular bottom, smaller than diam
eter Of The rope, thus giving q pinching