FOR ORDERING INFORMATION
A Worm Harvester is basically just a Trammel Screen,
which is a rotating cylinder with a screen mesh
for the sides. There are some Harvesters that work
with a vibrating or shaking flat screen, but the
most common types are all trammels. As the cylinder
rotates, the material inside is rolled across the
screen as it moves from the input end to the output
end. This forward motion is accomplished by the
angle that the harvester is tilted. As the
material is rolling, anything smaller than the holes
in the screen will fall through the screen, and
the rest will continue till it comes out the output
end. At the output end, a cone is installed that
can separate most of the worms from the other
material that did not go through the screen.
There are several factors that can affect the efficiency
of a Worm Harvester. We will look at each one of
If too much material is put in at one time, the
screening process will not be efficient, as some
of the material will never reach the screen where
it could fall through. The moisture level is important
in this, as wet materials tend to stick together
and "ball" up from the rolling action.
If you take castings that have been screened through
an 1/8-inch screen, and soak them in water, very
little of it will go back through the same size
screen. They will instead form large balls, and
roll out of the harvester. This demonstrates the
need to have your worm bed as dry as possible before
Worm beds are all wet to some degree. When this
moisture level becomes excessive, less slope on
the Harvester, and less material put in at one time,
can increase the efficiency of the screening process.
When the material is dryer, more slope can be used,
and more material can be added at one time. The
ability of a Worm Harvester to be easily adjusted
in slope can be an advantage.
Most worm farmers will hit their Harvester's screen
with a stick from time to time, to knock off particles
that are stuck on the screen. Finish nails can be
taped to the Jets' rotating hoop where the castors
will run over them. This causes the screen to jump,
which can dislodge stuck material, just as in hitting
it with a stick. With the Jet Harvesters though,
this vibration can be made automatic, and either
used or not.
Speed of Rotation
There is no perfect speed, in RPM's (Revolutions
per Minute) for a rotating Worm Harvester. If the
Harvester rotates too fast, it will sling worms
and material to the side from centrifugal force.
If the speed is too slow, it takes much longer for
the material to move through the Harvester. As the
diameter of the rotating screen increases, the RPM
needs to be reduced, to maintain the same speed
at the circumference of the barrel. This is the
important speed, the inches per minute that the
screen moves, not necessarily the RPM that the Harvester
moves. Jet Harvesters have the proper speed for
The slope of a Worm Harvester will determine how
fast the material will move from the input to the
output. A Jet Harvester is designed with the
most often used slope built in, when the legs are
adjusted so that the frame is in a level position.
The slope can be easily changed with the adjustable
legs, to suit any type of material.
In general you will increase the slope when the material
being screened comes through the screen easily. This
will be drier material, material with few worms, and
when using a larger size screen mesh.
The slope is decreased when most of the material is
not going through the screen, but rather going out
the end. This can happen with wet material, material
with many worms, and when using a smaller mesh screen.
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