Below is the selection menu for OptiTruck Stability Module. Choose a configuration and continue onto the input screen.

OptiTruck’s crane stability module provides a means for estimating stability when a crane is mounted on a truck. When a crane – either stiff boom or articulating – is loaded and extended, it exerts an overturning moment on the truck. The overturning moment works to tip the truck, while the weight of the truck, equipped with outriggers and stabilizing devices, works to keep it upright. A comparison of the tipping moment to the righting moment forms the basis on which crane stability is calculated.

Obviously, the potential consequences of an unstable truck are important, so take your time to ensure that the data you enter is correct. OptiTruck lets you quickly evaluate different outrigger, crane and truck configurations to find one that will be stable under all combinations of hook load and crane extension.

OptiTruck uses the truck weights entered in the weight distribution module to begin the calculations on stability. It is the weight of the truck and its dimensions that keep the truck grounded when an extended crane is introduced. So, start with an accurate weight distribution calculation in the weight distribution module. OptiTruck will automatically transfer the correct empty truck weights and dimensions into the stability module.

OptiTruck calculates stability by comparing the factors working to overturn a truck with the factors working to keep it upright. In general, the things that work to overturn a truck include the load on the crane hook and the weight of the crane, both at a distance when the crane is fully extended. By combining the loads and distances working to overturn the truck, a quantity called an ‘Overturning Moment’ is calculated. The things that work to keep the truck upright include the weight of the truck itself, the weight of its permanently mounted equipment, and its stabilizing devices and outriggers. By combining the weights of the truck with the distances associated with each of those weights, a quantity called a ‘Righting Moment’ is calculated.

Comparing the overturning moment to the righting moment provides a percentage, called the ‘Stability Ratio’, which expresses how large the overturning moment is relative to the righting moment. If the overturning moment exceeds the righting moment – in other words, the tendency for the truck to tip exceeds the tendency for it to stay upright – the truck will tip under maximum crane load at maximum extension. Stability ratios greater than 100% indicate that the truck will tip under the right combination of slew angle, crane extension and hook load. Stability ratios less than 85% - e.g. the tendency to overturn is less than 85% of the tendency to stay upright – are generally considered satisfactory. Stability ratios between 85% and 100% should be regarded with extreme caution, and steps must be taken to reduce the ratio to less than 85%.

OptiTruck is equipped to handle conventional truck-mounted cranes positioned just behind the cab, and cranes mounted behind the rear axle. Those configurations are known as “behind the cab mount” and “rear-mount,” respectively. OptiTruck will calculate stability in the presence of both the crane’s own outriggers, assumed to be positioned at the crane’s centerline, and auxiliary outriggers positioned at a distance from the crane.

There are some other configurations for which OptiTruck is not suitable. Some of those configurations include, but are not limited to:

· Cranes mounted to one side or the other of the truck’s midline. Service bodies and other cranes mounted away from the middle of the truck fall into this category. OptiTruck is not suitable for these cranes.
· Cranes mounted in positions other than just behind the cab or just aft of the rear axle. Stability for mid-mounted cranes may not be calculated using OptiTruck.
· Installations where the truck is lifted from the ground by the outriggers. OptiTruck assumes that the truck’s tires remain in full contact with the ground at all times. OptiTruck does not calculate accurate stability characteristics when any of the truck tires are lifted from the ground.
· Outrigger configurations other than one set of outriggers at the crane and another set at a distance from the crane, with both sets symmetrical about the truck’s midline. OptiTruck will not consider situations where the crane’s primary set of outriggers is set at a distance from the crane, nor will it consider single-point outriggers like those mounted on a truck’s front bumper.
· Any crane and outrigger configuration that does not look like the pictures on the input form. If your application doesn’t look the same as the ones that are pictured on the input form, it probably isn’t the same. Have a qualified engineer evaluate the stability.