The Wallace miner. [volume] (Wallace, Idaho) 1907-current, 1923-02-22
BUNKER HILL HOIST
is A MODEL MACHINE
CONTINUED from Page u

Continued from Page -
ance on a 42-degree incline nom hori-
zontal, with ultimate depth 600 feet.
Normal load 5000 pounds and a rope
speed Of 500 feet per second. Size OF
rope to be Is Inch diameter Weight
Of empty truck 5000 pounds.
The normal duty consists OF the
lowering of loaded trucks of mine
timbers, supplies and men, operating
sometimes in balance, but often out Of
balance, therefore, the load would
sometimes require a positive torQue on
the motor and often a negative torque
THE hoist to be particularly adapt
ed to the safe handling of 20 men per
skip either lowering or hosting at a
speed of 600 feet per minute or less.
ITO meet this duty the engineers
OF the Bunker Hill company passed
in review the various types of hoists
and controls and finally decided upon
the hoist, as manufactured by the To-
cal company as the one best adapted
to their needs.
Mechanical Features.
"One striking mechanical feature of
this hoist, which differs from those of
other manufacturers is the adoption
OF the automobile type of clutch in
pi,.ce of the ordinary types of external
contracting bands or internal expand
ing bands The clutch used consists
of a number of dry plates operating
almost exactly like the automobile
clutch except of much larger capac-
ity This clutch is soft and flexible
and at the same time powerful and
positive in action and is easily applied
or adjusted.
THE bearings on the main drums
as the pinion shaft are of the ball
bearing type. which reduces friction to |
a minimum. The hoist being a single /
reduction clearinghouse geared type /
with induction motor drive. On ac-
count of the unusual duty, which re-
quires that nearly 80 per cent of the
time the hoist is lowering heavily
loaded skips and raising empty ones
(the only time when this condition is
reversed being when the men are /,
hoisted off shift or out of the mine), h
special attention was given the me-
chanical and electrical braking power. /;
Each drum is provided with two
mechanical brakes, one operated by
hand only and the other by compress
ed air. The mechanical brake drums /
have Eastwood blocks fastened to the
drum or moving part instead of to the ]
bands as is ordinarily done. The
idea of thus applying the wood blocks s
was to give greater radiating capac- !
ity for the heat generated by long ap- Z
plication of brakes h
Safety Features First.
LAS nearly all the men working be-
low the Kellogg tunnel level of the
Bunker Hill mine are handled by this
hoist special attention was given to
safety features, for possible over
winding and er-speeding, and the
latest type of WEIGH protective appar-
atus was installed on the hoist to pre-
vent such accidents h
ION account of the excessive long t
rope for which the hoist was design q
ed it was considered necessary to il
DlONlQc SOIlc lOIn VI DIdNlilS Otiltl &
han the application of fractional c
brakes. AS the hoist handles both il
men and mine supplies and often has 1
70 move the skip at less than full Ii
speed. sorre form of dynamic braking p
rad to be designed especially for the t
slow speeds. d
1.-THE Ilgner-Ward- Leonard type of s
control, consisting of a direct current t
motor geared to the hosting machine, Il
operated from a separate motor gen. T
,rator set with fly wheel was consid $
red Also the use of a two-speed "
motor or possibly two motors of diff n
erent speeds, the lower speed motor n
o be used for regenerative braking C
when the speed of the total equip p
mt had exceeded the synchronous p
peed of the other higher speed mo- tt