Determination of bead contact force for safe, reliable mounting of tyres

Determination of bead contact force for safe, reliable mounting of tyres

The reliable and safe mounting of a tyre to a rim is a fundamental requirement in fully automated tyre and wheel assembly lines as well as in car workshops all over the world. For safety reasons, the damage of the bead must be avoided strictly in the mounting process as well as air loss of the mounted tire. Furthermore, a proper bead seat on the wheel is important to prevent disturbing behavior like additional vibrations due to tire uniformity issues. The bead contact force is a leading parameter to influence the mounting behavior of the tyre. Therefore, this force has to be measured in order to optimise the mounting characteristics.

As a solution provider for measurement and testing technologies inmess delivers different types of testing machines for independent laboratories and production lines throughout the world. The laboratory equipment is used for qualification and certification of tyres and also for sample inspection in production lines.

The Bead Contact Pressure Testing Machine (BCM) of inmess allows the customer to determine the bead contact forces and the force behavior in accordance with global standards (ETRTO, WDK) and customer-specific procedures.

The inmess BCM is equipped with 8 segments simulating the bead seat area of a rim. According to customer demands, different bead seat angles can be delivered. The machine is designed in such a way that these segments are moving in radial direction when the tyre is placed on the segments: By doing this, the tyre is stretched from a minimum to a maximum testing diameter. During this movement with speeds up to 45mm/min, the travelling distance as well the contact force is measured. This leads to a characteristic curve of the force with increasing diameter.

In the evaluation process at least two quantities are evaluated. For this, the forces at the minimum and maximum testing diameter of the tyre are determined. The force at the minimum diameter is defined as the lower security limit and the force at the maximum diameter as the upper mountability limit.

The inmess design is based on a servo driven spindle generating the radial movement of the segments. Strain gauge bridges are applied to the segments in order to measure the forces during operation. The maximum force is limited to 20kN and can be adapted to lower ranges if required.

inmess delivers the BCM worldwide to the major tire manufacturers for more than 20 years now. The ongoing adaption to state-of-the-art technology and customer requirements in combination with low maintenance costs guarantees maximum investment reliability for the customers.

CAPTION: Bead Contact Pressure Testing Machine (BCM)

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