NB Basics of wheel balancing 16Mar2011 [Kompatibilitätsmodus]

Wheel Balancing Basics
Bernhard Hoffmann, Business Unit Manager Wheel Service
Made in Germany
Schedule
Theory of balancing
Equipment
Clamping devices
Development of wheels
Development of equipment
Theory of balancing
Problems caused by unbalance
Contact loss between tire and road
Comfort loss for driver and fatigue at
longer trips
Faster worn-out of the tires
Premature worn parts as shock absorbers,
steering parts, etc
Limited life span of the car
Increase of fuel consumption
http://www.dionys-hofmann.de/en/news/balancing_why.html
Imbalance is caused by tolerances
Tolerance is caused by the tire
where the mass is not evenly
distributed regarding to the axle
Tolerance is caused by eccentricity
Static unbalance
30 g of imbalance
corresponds to 4.000 g
centrifugal force at a
speed of 100 km / hr
Dynamic unbalance
Can only be measured when the wheel is rotating
How does a wheel balancer work
The imbalance on a wheel balancer is detected during the rotation
of the wheel. The speed of this rotation does have an impact on:
- Accuracy
- Time required for the measurement
“So called” piezo sensors detect the vibrations during the rotation
These values are transmitted to the basic balancing board and
calculated into values in gram
In order get this calculation done the software needs 3 data of the
wheel:
- Distance from the cabinet to the rim edge
- Diameter of the rim
- Width of the rim
The basic set up of a balancer looks like this
Basic setup of a wheel balancer
In principle every wheel balancer in the world is set up like shown
in the picture below
B
A
D
Piezos
Cabinet
How does a wheel balancer work
During the rotation the software of the
balancer cuts the wheel in half and calculates
the imbalance for each side of the wheel
separately
After this it combines both values in order to
get the perfect measurement for static and
dynamic imbalance
It is therefore important that the planes
where the weights are to be attached are
positioned one each for every side
Main balancing programs
STEEL
ALU 2
ALU 3
Imbalance correction
After the measuring run the imbalance values (Static and dynamic)
are displayed for both sides
Depending on the balancing program the requested weights are
attached to the wheel on the 12 o´´clock position or with the gauge
arm
- 12 o´´clock position placement is used for STEEL wheels and can be
used for alloy wheels
- Gauge arm placement is the more accurate procedure for alloy
wheels
The weights are always attached 180°° opposite of the point where
the imbalance has been detected in order to be compensated
Imbalance correction
Bold centering or center hole?
Is the rim attached tight to the
hub and does not slip when the
nuts are loosened the wheel is
hub centered
Is the rim not attached tight to
the hub and does slip when the
nuts are loosened the wheel is
bolt centered
Mounting failures
An eccentricity caused by an non
centered attachment to the hub
does cause a static imbalance
An eccentricity caused by a dirty
hub or a dirty surface on the rim
does cause a dynamic imbalance
Mounting errors
Clamping failures
Standard way of clamping the wheel
Mid centering device comes with most balancers as standard
Possible failures:
Cone is damaged
Surface of centering device not plane
Quick nut not tightened properly
Contact surface of the rim is not clean
Mounting errors on the car
Eccentricity
Matching
Before
Balancing weight
After
Balancing weight
Heavy point in the rim
Heavy point in the tyre
Heavy point in the rim
Heavy point in the tyre
Equipment for balancing
Equipment for balancing
Equipment for balancing
Equipment for balancing
Properly centered is half balanced
App. 90% of problems with a
balancer are generated by a badly
clamped wheel or wrong positioned
wheel weights
Standard centering kit
Clamping plate
Extend of delivery
Option - 1987009W24
Flange and Shaft
Centering cone
Check for damages
and wearsigns
Look for dirt
and wearpatterns
Chech inside for
wearpatterns
Check for dirt and
wearpatterns,
clean as often
as needed
Tolerances
0,02 mm
0,02 mm
0,1mm = 10 gram
0,2mm = 20 gram
0,3mm = 30 gram
etc.
Standard way of clamping
1 – Clamping with the cone from outside
Risk to damage rim
No machined surface on rim
2 – Clamping with cone from the inside
Most used way of clamping
Universal
Not always accurate enough
3 – Clamping with a cylindrical ring
Most precise way of clamping
Lots of different rings required
Extendable rings are expensive
Stud hole flange
Quick Plate
Universal flange for closed center holes
Truck wheels
Truck wheels
Balancing terms
Remount Error
Display of imbalance values
Suppression of minor imbalances
Remount Error
Bei einer Umschlagprüfung wird ein exakt ausgewuchtetes Rad von der
Auswuchtmaschine gelöst und, relativ zur Hauptwelle, um einen Winkel von 90° oder 180°
verdreht wieder aufgespannt.
Wenn vorausgesetzt wird, dass
ein
die
die
die
Rad mit geeigneter Mittenzentrierung mittlerer Größe verwendet wird
Mittenbohrung einwandfrei, d.h. nicht ausgeschlagen oval oder beschädigt ist
verwendete MZV sauber und einwandfrei und ohne eigene Unwucht ist
Anlagefläche des Rades sauber ist
können Umschlagfehler von 5g bis 8 g auftreten. Bei geschlossenen Felgen können diese
Werte auch größer sein.
Diese Umschlagfehler sind begründet durch zulässige geringe Maß- und
Formabweichungen, hauptsächlich in der Felge. Aufgrund dieser Abweichungen ist die
Zentrierposition auf dem Aufnahmeflansch meist von vielen Zufälligkeiten abhängig.
Die Zentriergenauigkeit kann jedoch unter Umständen allein dadurch verbessert werden,
wenn auf der Auswuchtmaschine und am Fahrzeug beachtet wird, dass sich das Ventil im
Moment des Festspannens auf der 12 Uhr Position befindet. Das Rad „hängt“ dann
jedesmal in der gleichen Richtung.
Remount Error
During the remount error check an accurately balanced wheel is loosened from the
balancing machine and mounted again in an angle of 90° or 180°, relatively to the main
shaft.
If it is presupposed that
a wheel with suitable center centring of medium size is used
the center hole is perfect, i.e. not deflected oval or damaged
is the used mid centering device clean and perfect and without own imbalance
the contact surface of the rim is clean
A remount error from 5g to 8 g can occur. With closed rims these values can be also
larger.
This remount error is caused permissible small measurement and form deviations, in the
rim. Due to these deviations the centering position on the flange depends usually on
many eventualities.
The centering accuracy can be improved however alone thereby if on the balancing
machine and at the vehicle it is mounted that the valve is located on the 12 o'clock
position. The wheel „hangs “then each time in the same direction
The remount error check is always performed in balancing mode STEEL
Display of imbalance values
The display of imbalance values is often also understood as the accuracy of the balancer,
which is not true
Imbalance values are displayed in the way that wheel weights are available on the
market.
1, 2 and 5 gram
In the US the steps are 0.1, 0.25 and 0.5 ounces
In Europe the steps are
The steps are adjustable in the software
Imbalance suppression
Due to the mechanical tolerances it does not make sense to display very small imbalance
values.
Out of that every balancer does suppress minor imbalances below minimum 3 gram
(corresponds to a mechanical tolerance of 0,03 mm). Several balancers from competitors
do suppress 5 gram or even more and show every imbalance below this value as ZERO.
Checking the suppression on competitors balancers in easy to perform:
Balance a wheel to ZERO
Set the balancer to fine reading
Attach 5 gram to the wheel and check the display. If nothing is displayed the balancer
does suppress minimum 5 grams
Attach another 5 gram to the wheel and check the display
CONCLUSION
Imbalance is caused by tolerances
90% of problems on a wheel balancer is NOT caused by the
balancer but by
-
Improper clamping of the wheel to the balancer
Wrong input of data
Wrong placement of wheel weights
Improper mounting of the wheel to the car
Use clamping accessories
- Alloy clamping hood
- Stud hole flanges
- Quick plate
Thank you very much for
your attention
Otto Nußbaum GmbH & Co. KG
Korker Strasse 24 | D-77694 Kehl-Bodersweier
Tel.: +49 (0) 78 53 899 – 0 | Fax: +49 (0) 78 53 87 87 | E-Mail: [email protected]
Irrtümer und Änderungen vorbehalten | Stand: 13. März 2011
Made in Germany
Ho