# The Importance of Crane Wheel Load Calculation

Introduction

Crane wheel load calculation is a critical aspect of overhead crane design and operation. The vertical pressure exerted by the wheels on the track, known as the wheel pressure load, is a key factor in determining the strength and stability of the crane’s operating mechanism and metal structure. It also provides essential data for designing wheel devices and track support structures. Accurate calculation of the wheel pressure load is crucial for ensuring safe and efficient crane operation.

Types of Wheel Pressure Load Calculation

There are two main types of wheel pressure load calculation: calculation under moving load and calculation under super static structure. The former involves determining the wheel pressure load when the crane is in motion, while the latter focuses on calculating the load when the crane is stationary.

Calculation of Wheel Pressure Load under Super Static Structure

When the crane is not in motion, its four-point supporting structure is considered super static. The distribution of the supporting reaction force is influenced by factors such as the load, structural rigidity of the frame, foundation rigidity, manufacturing and installation accuracy of the frame structure, and the elasticity and flatness of the track. To simplify the calculation process, an approximate solution method is commonly used, as accurately accounting for all these factors can be time-consuming and challenging.

Example Analysis

Let’s consider an example to illustrate the calculation of wheel pressure load. Assume we have an overhead crane with a lifting capacity of 20 tons, a span of 22.5 meters, and four wheels. The total weight of the crane, including the trolley, is 32.5 tons. The trolley weight is 7.5 tons, and the spreader weight is 0.5 tons. The minimum distance from the hook centerline to the end beam centerline is 1.5 meters.

The maximum wheel pressure load under full load can be calculated as follows:

[P_{\text{max}} = \frac{(32,500-7,500)}{4} + \frac{(20,000+500+7,500) \times (22.5-1.5)}{2 \times 22.5} = 19,317 \text{ kg}]

[P_{\text{min}} = \frac{(32,500-7,500)}{4} + \frac{(20,000+500+7,500) \times 1.5}{2 \times 22.5} = 7,183 \text{ kg}]

[P_{\text{max}} = \frac{(32,500-7,500)}{4} + \frac{(500+7,500) \times (22.5-1.5)}{2 \times 22.5} = 9,983 \text{ kg}]

And the minimum wheel pressure load is:

[P_{\text{min}} = \frac{(32,500-7,500)}{4} + \frac{(500+7,500) \times 1.5}{2 \times 22.5} = 6,517 \text{ kg}]

Thus, the maximum wheel pressure load is 19,317 kg, and the minimum wheel pressure load is 6,517 kg.

# Conclusion

Accurate calculation of the wheel pressure load is essential for ensuring the safe and efficient operation of overhead cranes. The wheel pressure load influences the design and strength of crane operating mechanisms, metal structures, wheel devices, and track support structures. By considering factors such as the load, structural rigidity, foundation rigidity, and track conditions, engineers can determine the optimal wheel pressure load for a given crane. This calculation plays a crucial role in maintaining crane stability, preventing wheel slippage, and ensuring the overall safety of the lifting operations. Therefore, careful consideration and precise calculation of the wheel pressure load are vital for the successful and reliable operation of overhead cranes.

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