Close up of side dump trailer

To a layperson, the actions involved in dumping material out of a trailer seem simple. The trailer is tipped, the material is unloaded, and the empty tub is ready to be filled again. In reality, there is a lot more to know about the mechanics of side dump trailer dump cycles, with one critical example being tub slap.

The Importance of Tub Slap

Tub slap is an action that occurs when a side dump trailer reaches the end of the tub dump cycle. At the point when the hydraulic cylinders reach the end of the cycle, there is a certain amount of force that creates an impact, or jarring motion. This motion, referred to as tub slap, is important because it allows the tub to shake out any material remaining in the tub during the initial dump. It’s especially vital when hauling more sticky materials such as clay or manure.

Having a trailer that utilizes tub slap provides greater safety for the operator because it helps to remove any material remaining in the tub at the end of the dump cycle. This movement eliminates the need for the driver to leave the safety of the cab in order to manually empty the tub, which not only increases safety for your employees but also produces greater efficiencies in dump times.

Tub Slap and Trailer Stability

Tub slap plays a critical role in an effective tub clean-out, but it can also affect a trailer’s stability. SmithCo has been designing side dump trailers for nearly 30 years, and our designers and engineers have the expertise needed to properly execute a trailer design that incorporates a safe tub slap action in the dump cycle.

Unfortunately, not all trailer manufacturers account for tub slap in the design of their trailers, resulting in stability issues. The trailer’s cylinders and attached components must be properly designed, tested, and manufactured to account for the forces that are generated by this movement. The trailer must be engineered to work with the tub slap, not against it.

Tub Slap Utilizes Tub Acceleration

Some trailer manufacturers stop tub slap from happening altogether by altering the rate of tub acceleration.

Tub acceleration occurs when the tub moves faster at the end of the dump cycle than at the beginning. By reducing the acceleration, you reduce the intensity of tub slap. However, reducing or removing tub slap entirely is not actually ideal. Without the impact of tub slap, the chances of the operator having to leave the cab and manually clean out the tub are much higher.

It should be noted that some models of side dump trailers are engineered with no tub slap based on their intended use. When side dump manufacturers design trailers for a specific use, they need to balance how changes to the tub will affect the dump cycle in the areas of tub slap, clean out and stability. SmithCo’s engineering capabilities and industry experience provide an extensive knowledge base as to which trailer models should and should not have tub slap at the end of the dump cycle

Design Expertise at SmithCo

Through the years, SmithCo has always been a proponent of tub slap in many of our trailer models. SmithCo has tested, tried, and built a variety of tub designs over the years. Everything we learn goes into improving tub design to meet the needs of customers. Small changes to cylinder geometry can have a big impact on tub acceleration and tub slap, but with a quarter century of testing and listening to customer feedback, we’ve learned a balanced approach to build a stable trailer where tub slap helps material clean out effectively. If you have specific questions about tub slap, call us today at 800-779-8099 or visit our contact page.

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