Heavy Truck Suspension
Suspension technologies in heavy duty vehicles have come a long way since their inception; from rudimentary mechanical springs to modern air suspensions with hydraulic shocks. Today, manufacturers are taking the next steps in improving suspensions, with advancements such as air dampers, continuous damping control, air spring ride height sensors, body roll control monitors and automatically deploying auxiliary suspensions. These next-generation suspension technologies are here, or to be soon, and can help extend maintenance intervals and vehicle lifecycles, improve tire wear, increase safety and handling and even help with driver recruiting and retention. So, which of these enhancements are right for your fleet?
Suspensions 101
At its most basic, “the suspension of a vehicle is crucial in maintaining contact with the road surface. The suspension also protects the vehicle, its occupants and its cargo from irregularities on the road surface.
There are two major components used to achieve this: springs and shock absorbers. Springs allow the wheels and body of the vehicle to move independently from one another, and shock absorbers act as dampers to control the motion caused by the springs.
When the vehicle is placed under load, the suspension is forced to respond.
Improving on air ride
While air ride suspensions are a vast improvement for heavy duty vehicles over traditional mechanical suspensions, there is still room for improvement. For instance, shock absorbers in current air suspension technology are typically manually adjusted, meaning they can only be set for one particular condition.
Air damping
Air damping, in which a damper is built into the air spring, is a solution to this problem that also alleviates other concerns. Air damping is automatically proportional to the load, so when the vehicle is unloaded it is damped less, and loaded it is damped more. “It automatically adjusts to make sure that the tire stays in contact with the road and there’s less movement in the vehicle.
Removing traditional shock absorbers from the equation also correlates to weight savings, which is increasingly important in today’s vehicles, where optimal efficiency is key.
Altogether, air damping leads to a better ride under any load with no manual adjustment necessary, less wear on tires and other components, less driver fatigue and risk of cargo damage, additional weight savings and reduced suspension maintenance.
Ride height sensors
Though air suspensions have decreased ride height issues relative to traditional mechanical suspensions, fleets may still run into problems in this area.
Improper ride height can be especially detrimental when it comes to driveline angle. Therefore, it is imperative that ride height be within specification at all times, making ride height sensors an important component for vehicle longevity.
While ride height sensors aren’t exactly the latest technology, FSIP has developed a sensor that is built into the air spring, eliminating an additional mechanical component and, therefore, another potential maintenance item.
She also says this smart component has additional capabilities beyond measuring ride height. It can measure pressure and temperature, both of which are very useful from a maintenance standpoint, as well as acceleration. All of this data can be communicated to the driver if immediate action is required, and to the fleet via a telematics system for predictive maintenance purposes.
From pressure measurements, the load on each axle can be calculated, helping avoid CSA overload infractions. Pressure measurements can also be useful from a maintenance standpoint: if a large amount of pressure is being lost over time, there may be an issue with an air spring. The fleet can flag the vehicle for inspection next time it is in for service, replace faulty components and avoid a potential costly breakdown on the road.
Temperature measurements are especially useful when it comes to predictive maintenance. If the temperature of an axle or wheel hub begins to increase, it can indicate an issue with a seal or bearing that otherwise may go undetected until a catastrophic failure occurs. If the temperature is noted to rise significantly in a short period of time, it can be a signal to the driver that the vehicle needs to stop immediately in order to avoid a thermal event.
Fleets can also use the data to incentivize drivers with safe driving habits.
Body roll control
Another issue with air suspensions is the potential for body roll. If a single height control is used on the same axle or multiple axles, air is able to move from air springs that are under load to those that are not.As loads increase, body roll can become an issue.
If the time requirement was not met, no change would be made, saving air, he continues. The same process might be applied to reactive air suspensions to decrease air usage. Changes in ride height might be taken over a 14-second timeframe, for example, so that large movements can be filtered out. Changes would only be made if the average ride height had actually changed.
Automatically deploying auxiliary suspension
In order to increase load carrying capacity, some fleets choose to specify vehicles with auxiliary lift axles, such as a pusher axle (located in front of the tandem drive axle) or a tag axle (located behind the drive axle). While these are especially common on straight trucks, they can also be found on trailers.
Auxiliary axles have their own suspension, and work to support the vehicle’s main suspension and frame by distributing the load more evenly. Distributing the weight between more wheels also helps to protect road surfaces, highways and bridges, and can help fleets meet local or state axle weight laws.
Common auxiliary suspensions today are deployed by the operator operating a switch
The future of heavy duty truck suspensions
One common trend noted almost unanimously among manufacturers for the future of vehicle suspensions is lightweighting. As fuel prices continue to fluctuate and emissions standards become more stringent, OEMs will continue to look for ways to reduce the weight of commercial vehicles as a way to improve fuel economy and allow fleets to haul more cargo.
Eliminating typical maintenance components such as shock absorbers is a win-win in that it reduces both price and complexity, and therefore operating cost. Any time a manufacturer can simplify a component or system, it is typically beneficial to fleets.
Extended component life and maintenance cycles are also important when talking about another commonly discussed future trend: vehicle autonomy. While many agree that full autonomy is far in the future, manufacturers are beginning to prepare for it now.
If future autonomous vehicles don’t have drivers onboard to monitor systems, vehicles will need longer component life with less maintenance, and they will have to monitor their own systems. That’s where self-diagnosing smart technologies such as FSIP’s ride height sensors become even more important.
Even without autonomous vehicles roaming the roads, these technologies are already important to fleets looking to reduce operating costs, increase efficiencies and improve maintenance practices. From humble mechanical beginnings, suspensions have progressed to the point of implementing smart, self-monitoring technologies. Every fleet can benefit from these new advancements in heavy duty vehicle suspension technology.