Hofmann Snap-on Y2k Service Manual Download

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15.4 The drive systems

The wheel clamped to the main shaft has to be put in rotation, so that the dynamic unbalance
produces measurable alternating forces.

15.4.1 Hand drive

The operator, turning a crank, puts the main shaft with the clamped on wheel in rotation.
At reaching the minimum measurement speed of 100 RPM, an audible signal is given.
The flywheel mass of the wheel supported by low-friction ball bearings keeps the rotational
speed during the ten revolutions of unbalance measurement almost constant.
The clamp nut is fitted with two turning handles, serving as a crank.
A main shaft with an extension to the left of the vibratory assembly is available for a left-hand
crank (used with JEBEG

b9000

)

ATTENTION! For precise measurements and calibration, use the crank at the clamping nut.
Since the left-hand crank is some distance away from the vibratory assembly, turning the
crank introduces strong forces by lever action, which does not decay completely before
unbalance measurement begins.

15.4.2 Motor drive

The primary functions of the motorised drive system are, to accelerate the main shaft with the
wheel clamped to it up to measurement speed, keeping the speed constant during
measurement and subsequently slow down to a dead stop. Acceleration and deceleration
should be rapid but with controlled torque, avoiding slippage of the wheel on the adaptor.
During unbalance measurement, no vibrations should be generated by the drive system.
With some variants of the vibratory assembly, the drive motor is used for breaking as well.
The mechanical parts of the Y2k drive system differ little from the previous HOFMANN
design, the principle of operation is quite different, making the drive system suitable for high
and low speed balancers.
The drive system consists of the motor (

Snap-on

P/N 2-22066, HOFMANN Mat-Nr. 4104280)

fastened to a bracket, welded to the vibratory tubing. The small pulley at the motor, the big
pulley at the left end of main shaft and the Multirib belt (

Snap-on

P/N 8-3531, HOFMANN

Mat-Nr. 1252584) called mlti-vee belt as well. The screws fastening the motor to bracket are
used for belt tensioning also.
The big pulley is seated on the tapered left end of the main shaft and fastened wit one central
screw M8. For separating the big pulley, the central bore is furnished with a Thread M12.
After putting the big pulley back on the shaft, main shaft unbalance has to be compensated for
using code C84.
With a single-phase squirrel cage motor with a nominal voltage of 230-volts AC and a
maximum current of 4,5 A, the power requirements of the balancers can be easily met. It can
be hooked up to 50 or 60 Hz line frequency via a plug to ordinary wall outlets.
The drive system will work in a range of 170 to 264 volts AC. With 110 line voltage, a step-
up transformer (

Snap-on

P/N 7-00902A, HOFMANN Mat-Nr. 4501081) should be fitted

inside the cabinet.

Functional description of the drive system

Irrespective of line frequency, the Y2k drive system (patent applied for) accelerates to the pre-
set speed within a range of 80 to 200 RPM. With low speed operation (100-RPM) selected,
low torque is applied first. With the speed still near zero after half a second, full motor torque
will be applied. This is for preventing speed overshot with low flywheel mass as there might
be no wheel guard fitted with a low speed balancer.

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