Hofmann Snap-on Y2k Service Manual Download

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The inner surface of the band clamps has to be greased with "Molykote 33 medium" before
assembly. To set the braking torque, so that the test rotor accelerated to 100 RPM will stop
after one revolution, the rubber washer is compressed by tightening the self-locking nut (13-
mm width across flats).
ATTENTION! For optimum measurement precision during calibration or determining the
distance-depending phase shift using code C72, deactivate the shaft band brake temporarily
by pulling off one of the receptacles from solenoid.

15.5.1.2 Decelerating the main shaft by pressing the pedal

With the BOXER

S1100

and HOFMANN

geodyna 930,

a mechanical foot operated brake is

used for decelerating the main shaft after measurement and as the shaft lock (see chapter
15.5.2.1).

15.5.1.3 Braking by reversing the motor torque

For this economical and robust brake with well-controlled torque, just the relay K4 had to be
added to the drive system.
After reaching standstill of the main shaft, motor voltage has to be switched off immediately.
With the semiconductor AC controller, this is accomplished easily.

15.5.2 The main shaft locks

All vibratory assemblies of the Y2k balancing platform are equipped with a main shaft lock.
To place the compensation weights precisely and conveniently in the determined position, the
main shaft can be blocked.

15.5.2.1 The main shaft lock of the hand drive vibratory assembly

The outside shoe brake is pedal operated and acts via Bowden cable and single lever on a disk
fitted to the main shaft.
A coil spring inserted between Bowden cable jacked and the support plate protects the
Bowden cable from overload and restricts the braking torque, preventing the wheel to slip on
the adaptor.
The nuts (10-mm across the flats) at the end of the Bowden cable are adjusted for 0,1-mm
clearance between brake pad and the brake disc.

15.5.2.2 The shaft lock of the motor drive vibratory assembly

The mechanical brake is pedal operated and acts on the motor pulley. There is no electrical
interlock. The motion of the pedal, conveyed via Bowden cable, pulls together the two brake
levers with glued on brake pads. The front fastening screw of the motor serves as the lever
pivot.
The locknuts (10-mm across the flats) at the end of the Bowden cable are adjusted for 1-mm
travel before the levers, moved together by hand, hit the rear fastening screw of the motor.

15.5.2.3 The electromagnetic brakes

Big solenoid brake with a brake power of 30 Nm (Newton meters) acting on the main
shaft. Used with the power-clamping device only.

Small solenoid brake of three Nm braking torque, acting on the motor pulley is used as
shaft-lock and position brake e.g. for the "sticky on top" function.

Different in size but identical in design, the brakes, designated Y2, comprise of a ring shaped
stator with the winding behind the brake lining and the brake disc fastened axially movable to
the hub by an annular leaf spring. Without power, there is no friction at all, since the brake
disc is separated from the stator by an air gap. With current applied to the solenoid, the disc is

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