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tilt angle

Wind Speed and Truck Dumpers

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Wind speed not only affects the truck dumper itself, but also the truck and /or trailer. Understanding how wind speed impacts truck dumpers is critical for proper design and safe operation.

Parallel Wind Direction

Wind acting parallel with the truck dumper, referred to as a ‘head’ or ‘tail’ wind, applies the greatest force directly to the deck. A head wind blowing from the front to the back of the dumper typically does not present significant issues when the dumper is loaded. Even with the deck unloaded, the dumper typically has sufficient mass to counteract wind forces; however, raising the deck while unloaded during high winds is not recommended.

A tail wind blowing from the back to the front of the dumper typically places the most stress on both the structure and hydraulic system.

This added stress occurs because the wind acts in the same direction as the gravity load of the truck or trailer. Depending on wind speed and direction, a tailwind can add several thousand pounds of additional force to the deck. If the deck is aged or the truck is heavier than the dumper’s load rating, the additional load can cause structural damage to the main frame.

Cross Wind

Cross winds are of greater concern than parallel winds, despite putting less force on the dumper itself. The reason for this is the truck and trailer, and not the dumper deck. The trailer presents a large surface like a sail for the wind to act upon. The trailer is most vulnerable to wind while it is in the raised position after the contents have been unloaded. An empty trailer is relatively light compared to its surface area. High wind speeds on an empty trailer can put a twisting force through the trailer and into the dumper frame, regardless of whether the tractor is tied down or not. In a worst-case scenario, the wind will cause the trailer to shift on the deck, creating more torsional forces on the dumper and potentially causing the truck and/or trailer to fall. Safety/retainer hoops are a last-resort feature and are not designed to restrain trailers during high-wind events.

combination winds

Wind very rarely acts completely parallel or perpendicular to specific pieces of equipment. Wind direction can change rapidly, and swirling or turbulent winds can create a combination of forces in multiple directions. Surrounding geographic features, buildings, or nearby equipment can create additional currents or wind turbulence, adding to the complexity of the wind loading.

Design Parameters

Airoflex dumpers are designed for site-specific wind loading based on ASCE hazard data. This allows the wind forces to be accounted for in the major axes of the dumper for both structural design and foundation loads. The design wind speed may be very high, and is NOT the operational wind speed for the dumper.

Operational Parameters

Airoflex recommends a maximum wind speed of 20 miles per hour, based on a 3-second gust, as the cut-off for operating any truck dumper. Larger models (65-foot deck length and up), dumpers located on flat or open terrain, or areas prone to high wind gusts, may require a lower wind speed maximum. Smaller dumpers, or dumpers that are blocked from the wind by buildings or other structures, may be able to operate safely at higher reported wind speeds due to being shielded from the full wind force.
Any increase in the dumper’s maximum operational wind speed is site-specific and depends on the user’s safety procedures. The user assumes full responsibility for operating above the Airoflex-recommended guidelines and should not do so without proper consideration and safety protocols in place. When deciding whether to operate a truck dumper under specific weather or wind conditions, a general rule of thumb is to consider crane operation. If a crane would not be operated at the current wind speed or weather conditions, then a truck dumper should not be operated.

Conclusion

Wind forces have a great effect on the design and operation of truck dumpers. Understanding how they interact with a truck dumper can not only help with better structural designs but also allow for safe and continued operations. Please contact Airoflex with any questions about design or operation regarding wind speed.

Understanding Tilt Angle

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understanding tilt angle

Tilt angle is a key factor in ensuring the safe and efficient operation of a truck dumper. It affects how smoothly and effectively a load is discharged, as well as the overall stability of the equipment during use. In this article, we’ll explore what tilt angle is, how to determine the correct angle for different applications, and the potential risks and safety hazards associated with using an improper tilt angle.

Terms

Tilt Angle: The angle of the dumper deck with respect to horizontal. See Figure 1.

Angle of Repose: The steepest angle at which a sloping surface formed of a particular loose material is stamble.  See Figure 2.

Ѳ (theta): Symbol typically used to represent angle.

Figure 1: Tilt Angle

tilt angle

Figure 2: Angle of Repose

tilt angle of repose

How Much Tilt Angle Do I Need?

As a general rule, the optimal tilt angle for a truck dumper is the minimum angle at which the material will flow freely out of the trailer. For most bulk materials, this typically falls between 30 and 60 degrees. However, certain environmental and material factors can reduce flowability and may require the angle to be increased. These factors include:

  • Freezing Weather, Ice/Snow
  • Wet/High Moisture Content Material
  • Sticky or Adhesive Materials

Many facilities receive a wide variety of materials under different conditions. In these cases, it’s often recommended to set the dumper based on the material with the highest angle of repose to ensure consistent unloading performance.

Additionally, some trailer types—such as tankers—may require much lower angles, generally in the range of 15 to 30 degrees, due to their design and how material is contained.

Setting the Tilt Angle

While some dumpers may have multiple limit switches, the one that controls tilt angle is almost always located at the main pivot point. There are two common types of limit switch mounting configurations used to adjust the tilt angle:

  • Limit Switch Adjustment. See Figure 3.
  • Tab Adjustment. See Figure 4.

In the Limit Switch Adjustment style, the trigger tab is fixed in place, and the tilt angle is adjusted by moving the limit switch forward or backward along its mount. For finer tuning, the limit switch arm can also be adjusted.

In contrast, the Tab Adjustment style features a fixed limit switch position (though the arm can still be fine-tuned), while the trigger tab is field-welded in place to achieve the desired tilt angle.

Both styles are commonly used, but newer dumpers tend to favor the Limit Switch Adjustment method due to its ease of adjustment and the fact that it does not require field welding.

Figure 3: Limit Switch Adjustment

Figure 4: Tab Adjustment

Hazards

Improper use of the tilt angle can cause serious problems with the equipment and pose safety concerns.

  • Never Exceed a 63 Degree Angle: 63 degrees is a common angle used throughout the industry. This angle will allow most materials to flow freely while keeping the center of gravity of the truck and/or trailer in front of the dumper pivot. If a higher angle is required, a specialty solution/equipment may be required.
    • Cylinder Damage: Most telescoping cylinders used on truck dumpers are designed with some extra stroke at the top and bottom range of motion. Do not set the tilt angle based on fully extending a cylinder. The cylinder may fully stroke out at an angle greater than 63 degrees. This can also put extra impact stress on the cylinder.
    • Center of Gravity: Tilting a dumper more than 63 degrees can start to affect the balance point of the truck/trailer that is being dumped. If the angle is too steep, the trailer may start to fall back off the dump deck. The dumper and trailer are also most susceptible to winds at higher angles as there is less weight on the tires and landing gear (and tractor).

Conclusion

Understanding the angle of repose of your material is key to setting your truck dumper at the ideal tilt angle for efficient and safe operation. It not only boosts performance but also plays a critical role in maintaining safety standards. If you’re unsure about the angle of repose for a specific material, need help determining the right angle, or are dealing with sticky or non-flowing material, the Airoflex team is here to help. Don’t hesitate to reach out with any questions or concerns.