Hofmann Snap-on Y2k Service Manual Download

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The Vibratory assemblies

The vibratory assembly is the central module of a wheel balancer.
It consists of the force guidance structure for directing the alternating unbalance forces via the
transducers. The main shaft is supported on ball bearings in the vibratory tube with the wheel
adaptor at the right-hand end. The drive system is then propelling and stopping the main shaft.
The incremental encoder B8 is acquiring rotational travels, direction of rotation and absolute
angular position of the main shaft.
The vibratory assembly is fastened and supported towards the ground by the cabinet, so that
unbalance produces a minimum of vibration while the wheel is rotating.
To measure the unbalance, the wheel is clamped to the main; the shaft is accelerated to
measurement speed, with the electronic unit exploiting the signals of the incremental encoder
and the unbalance transducers.
The Y2k vibratory assemblies utilise the

irtual Plane Measurement

force guidance structure

(patent pending). With this force guidance structure, inadvertently produced forces and the
unbalance forces are directed horizontally via the transducers in an almost a one to one ratio,
thus avoiding overload. Without the lever action of conventional vibratory assemblies,
interfering vibrations and changes in transducer sensitivity caused by temperature changes,
fatigue, overload, humidity, etc. have minimum effect thus achieving good long-term and
repeatable measurement accuracy.
The unbalance transducers are located in close proximity inside the cabinet. Exposed to
almost identical temperature, temperature variations have little effect on plane separation. The
cabinet supports transducer B2, located in the rear. Transducer B3 at the front is clamped 7°
diagonal between the vibratory tube and vibratory plate. Two leaf springs provide mechanical
pre-stress to the transducers.
ATTENTION! Other machine parts must not obstruct the barely discernible movements of
the vibratory assembly.
Does the Bowden cable touch the cabinet immediately below the vibratory assembly, or the
weight tray rests on the vibratory assembly, part of the alternating forces produced by
unbalance are conveyed to the cabinet, side-stepping the transducers. That kind of force
bypass can have considerable negative effect on measurement accuracy.

Variants of vibratory assemblies within the Y2k balancing platform

The vibratory assemblies (currently 13 variants) consist of the following main parts:

Welded part

with force guidance structure and tube (6 variants):

1)  Motor drive with short tube for fixed adaptor flange
2)  Motor drive with long tube, for tapered shaft
3)  Motor drive with very short tube for power-clamping device
4)  Motor drive with very short tube for motor cycle variant
5)  Hand drive with short tube for fixed adaptor flange
6)  Hand drive with long tube, for tapered shaft.

The main shaft, two transducers with temperature sensor, the optoelectronic unit, the
motor, and the main shaft lock are attached to the welded part.

Main shafts

, supported by ball bearings in the vibratory tube (6 variants)

1)  Motor drive, hardened, fixed adaptor flange for Ø 28,5 or Ø 40 mm sub shaft
2)  Motor drive, tapered shaft for removable adaptor
3)  Motor drive, hollow shaft for power-clamping device (tapered shaft only)
4)  Motor drive, hollow shaft for non-rotating arbor (tapered shaft only)
5)  Hand drive, fixed adaptor flange for Ø 40 mm stub shaft only
6)  Hand drive, long shaft to the left for left hand crank

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