Montana oil and mining journal. [volume] (Great Falls, Mont.) 1931-1953, 1939-10-28
DoodIebug Development
Boon TO Placer Mining

contractors accumulations of used
equipment Old rock screens, con-
veyors. pumps, gasoline engines
electric motors and whatever the
corporation junk yard offered were
assembled and made to operate.
Gold saving devices were crude at
first. but as time went on were
improved to higher efficiences. The
generally accepted idea of the
doodlebug is to mount all the ma
chinery on a floating hull. The
hull is moved about in a pond by
small hand winches and small
cables Some operators make use
of the dragline to move the washer
around in the pond.
The people who built the first
doodlebug did not investigate
whether or not they were using
good or bad dredging practice with
regard to screens. water supply, etc.
Operators would boast of handling
1000 cubic yards daily in an out
fit which any placer engineer could
see where only 500 cubic yards
could be properly handled. In
many cases the recovery made un-
der these conditions was incredible,
but that was due to pure luck, per-
haps beginners luck"
The continued success of these
rigs soon drew the attention Of
placer engineers and manufacturers
Of the materials used in them. FL
nally the manufacturers visited
many of the large and small
dredges in operation and made in
quiries. Then their placer engi-
neers were put to work on the de-
velopment of small washers. This
work has resulted in a number Of
regularly manufactured and adver-
tised rigs, and has led to a new in
dustry in manufacturing, as well
as in operation. a new industry
which fills a gap in placer mining
and is here to stay.
Many of the first rigs were built
by contractors. They tried to on
crate these doodle bugs under the
same conditions as contracting. 1t
was some time before they learned
that their object was to wash dirt.
not to move It, This was particu-
larly true of the shovel and drag
line runners who worked on these
rigs with no knowledge of the
washers operations. These shovel
runners were generally good shovel
men, but would tend in their race
to move ground to crowd the wash
err This crowding of the washer
would result in much material
passing over the screen, which
would not be disintegrated or wash
ed at all
Generally. doodlebugs now have
reached a point of quite high eff
ficiency. They have become fairly
standard in the system and prin-
ciples of screening and washing.
Lately there has been introduced
near Helena. Montana, a new type
of screening, which does away with
the trommel or rotary screen
This new screening system uses the |
principle Of large oscillating sluice |
boxes. These boxes have screens ]
in the bottom over the rifles. The |
motion of the box |
Stops the water back up through |
the screen, thereby washing from |
underneath as we'll as fresh water |
on top This washer was |
worked out and put into operation |
by two local men. The plant handles |
$3.50 cubic yards per hour and is
fed by a one cubic yard North |
west dragline The first washer was
built three years ago as a float /
ing outfit and has been in con-
Linuous operation during the work
able season. Late in August, 1898
a washer using the same system,
but of the dry-land type, was put /
nto operation in the same district.
Both dredges have been successful,
although the dryland dredge has
encountered difficulties, due prob
lbly to the type of ground being
handled. This plant is operating in
ground with little gravel the
ground being mainly decomposed
granite.
CONTINUED next weekly