Sherline Tool Part 33050 DC Motor & Speed Control
The
90-volt DC motor provides far more than that of the 1/2 HP AC/DC motor
we used to offer prior to 1994. A DC motor offers its maximum torque at
low RPM where you need it most, so the full speed horsepower rating of
an AC/DC motor can be a little deceiving as far as offering practical,
useable power. The DC motor also offers smoother and quieter operation.
The motor now features externally replaceable brushes, making
replacement of worn brushes a simple task taking just a few minutes.
To
power and control the motor a more sophisticated speed control unit is
required. The control we have developed accepts any incoming AC current
from 100 VAC to 240 VAC, 50 or 60 Hz and automatically outputs 90 VDC to
the motor, so this unit can be used anywhere in the world without a
transformer. All you need is the correct wall plug or converter. In
addition, a load compensating circuit has been designed into the
controller. As load is applied, the speed control will add power to
attempt to hold a constant speed. Once the on/off switch is switched to
the "ON" position, a speed control knob is used to vary the speed over
the entire range. With the two-position pulley in the "normal" position
on a Sherline headstock, the speed range is about 70 to 2800 RPM. In the
"high torque" position the maximum speed is cut in half but torque at
any given speed is much greater. If you are using the motor in
non-Sherline applications, the maximum no-load speed of the motor shaft
itself is 6000 RPM. Complete specs on the motor can be found on the
"Standard Dimensions and Specifications" page on this web site.
Replacing an older AC/DC motor...
This unit can be purchased to replace an existing AC/DC motor on an
older Sherline machine. This very compact and well-engineered unit costs
far less than other DC units of similar power offered in major
industrial tool supply catalogs. If you are replacing an older AC/DC
motor and speed control you can re-use the same motor mounting bracket,
standoffs and drive belt, but you will need to purchase a new stepped
spindle pulley, P/N 43230 and the belt guard halves, cover mounting tab
and belt cover screws shown in the exploded view drawing below. You
could also purchase P/N 33060, which is the complete headstock with DC
motor and speed control as is shown below. A version with different
pulley ratios and offering a 10,000 RPM maximum spindle speed is
available as P/N 33070.