Do you know what is weight on wheels meaning? Let’s find out!
Weight on wheels (WOW) refers to the amount of static weight pressing down on each wheel of a vehicle while stationary.
It is an important measurement in vehicle design and dynamics.
The weight on wheels measurement allows engineers to understand how vehicle weight is distributed between the front and rear axles.
This weight distribution affects handling, traction, braking, and other performance characteristics.
For example, having more weight on the rear wheels compared to the front is desirable in a rear-wheel drive vehicle as it improves rear wheel traction.
Knowing the weight on each wheel also ensures that vehicle components like springs, shocks, and tires are properly specified to support the load.
Excessive or uneven weight on wheels can lead to component failure or wearing.
The weight on wheels measurement is therefore crucial in vehicle development to create a balanced and optimized design.
During regular vehicle operation, the weight on wheels changes dynamically with acceleration, braking, and cornering forces.
However understanding the static weight distribution is the critical starting point for vehicle dynamics analysis and tuning.
Weight on wheels remains a key measurement throughout the life of a vehicle.
How Weight on Wheels Works
A weight on wheels (WOW) sensor detects when an aircraft or ground vehicle becomes airborne.
It measures the weight or force exerted on the landing gear or wheels.
The sensor contains a mechanical switch or electronic transducer that generates a signal when a preset threshold is crossed, indicating when the wheels are supporting the vehicle’s weight versus when it is airborne.
The specific mechanism varies, but common implementations include:
- A compression sensor that detects when the strut or shock absorber on the landing gear is compressed by the vehicle’s weight pressing down on the wheels. When the vehicle lifts off, the pressure is released.
- A strain gauge sensor that measures stresses on the axle. The strain decreases when the upward lift force counteracts the weight.
- An optical or Hall effect sensor that detects a piston or lever position change linked to the wheel hub.
- A microswitch triggered when the oleo strut extends as the vehicle leaves the ground.
The sensor signal connects to a control unit that monitors WOW status. This helps prevent inadvertent gear or wheel deployment and enables important airborne systems.
For example, WOW tells an aircraft autopilot that the plane is no longer taxiing and can engage for takeoff.
Its key purpose is improving safety during critical takeoff and landing phases.
Applications in Vehicles
The weight on wheels concept has several important uses across various vehicle types including cars, trucks, and aircraft.
Cars
In passenger vehicles, weight on wheels sensors help monitor the vehicle’s stability and traction control systems.
They detect when weight is reduced on a wheel, indicating potential wheel lift or loss of traction.
The stability control system uses this data to apply brakes or reduce engine power as needed to keep the car stable during maneuvers.
Sensors also enable features like auto-hold, which applies the brakes when the car is stopped to prevent rollback on hills, and releases when the driver presses the accelerator. This improves comfort and control.
Trucks
For trucks and commercial vehicles, weight on wheels sensors provide critical data for monitoring cargo load and preventing rollovers.
The sensors help determine when a truck is overloaded on one side, which impacts stability.
The system can then alert the driver or actively adjust braking to counteract the imbalance.
Sensors also improve control of lift axles, which raise wheels off the ground when unloaded to reduce tire wear.
The sensors detect when weight is reapplied so the lift axles can lower and provide needed traction.
Aircraft
On airplanes, weight on wheels sensors detect when the plane has landed and its full weight is again on the wheels.
This triggers various systems like wheel brakes, reversers, and ground spoilers to activate for controlling the plane on landing.
The sensors prevent premature deployment while the plane is still airborne.
Weight sensors also provide input for calculating cargo load, fuel consumption, and performance parameters which are critical for safe operation.
They help ensure weight limits for takeoff and landing are not exceeded.
Benefits and Importance
Weight on Wheels systems provide several key benefits for vehicles.
Understanding these benefits highlights the importance of these systems for performance and safety.
Safety
The Weight on Wheels system is crucial for safety in many ways. It ensures brakes are only activated when the wheels are in contact with the ground.
Applying brakes while wheels are airborne could lead to loss of control when the wheels regain traction.
The system also disables cruise control and traction control when wheels are off the ground, as these systems require contact to function properly.
This prevents unsafe operation. In motorcycles, Weight on Wheels disables the throttle when the front wheel lifts, preventing potential accidents.
Performance
By disabling brakes and advanced systems when wheels are airborne, Weight on Wheels protects performance.
Braking while airborne would slow the wheels unevenly, damaging components.
Traction and stability control require contact patches to work, so disabling them without ground contact prevents malfunction.
Proper application of brakes, throttle, and advanced systems is ensured with Weight on Wheels awareness.
Fuel Efficiency
In cars and trucks, Weight on Wheels improves fuel efficiency by cutting fuel during zero-load conditions, like when jumping or cresting hills.
This prevents wasting fuel when the wheels are not propelling the vehicle.
Motorcycles also benefit from throttling down during front wheel lift for efficiency.
Common Issues and Failures
The weight on wheels (WOW) sensor plays an important role in controlling a vehicle’s safety functions.
However, like any component, it is susceptible to failure over time.
Some of the most common causes of WOW sensor failure include:
- Contamination: Dirt, debris, and road grime can accumulate on the sensor over time, affecting its ability to accurately detect weight on the wheels. This is especially common for sensors mounted low on the vehicle. Regular cleaning and inspection can help prevent contamination issues.
- Corrosion: Exposure to water, salt, and chemicals can cause the sensor and electrical connections to corrode. This leads to faulty readings and intermittent problems. Using dielectric grease on connections and checking for damage during routine maintenance can prevent corrosion issues.
- Damage: The sensor can become damaged due to rocks, debris, or being struck. This can break internal components and alter calibration. Damaged sensors should be replaced.
- Wear: Over many miles and years, the moving components inside the sensor can wear down and lead to inaccurate readings. As sensors age, response times can decrease.
- Electrical issues: Problems with wiring, connectors, fuses, or computer modules can prevent proper operation of the sensor. Electrical faults can cause abnormal or missing sensor signals.
- Calibration failure: Over time, the sensor calibration settings can drift outside of the normal range. This requires recalibration or replacement to restore accurate performance.
Paying attention to sensor operation, trouble codes, and fault indicators can help identify WOW issues early.
Proper maintenance and component replacements as needed can help minimize problems with this important system.
Troubleshooting Weight on Wheels Problems
Weight on wheels (WOW) issues can arise from faulty sensors, corroded connections, loose wires, and other problems.
Here are some tips for diagnosing and fixing common WOW failures:
- Inspect the WOW sensor visually. Look for damage, dirt/debris buildup, bent/broken mounting bracket, etc. Replace sensor if it appears faulty.
- Check electrical connections at the sensor and control unit. Clean any corrosion, reseat connectors, check for broken/frayed wires.
- Use a multimeter to check for continuity between sensor and control unit. If no continuity, there is a wiring fault.
- Check sensor resistance. Consult service manual for correct values. If out of spec, replace sensor.
- Watch sensor voltage or frequency during testing. Raise/lower landing gear to see if values change as expected. If not, sensor or wiring issue.
- Listen for noises during WOW activation/deactivation. Popping or clicking could indicate loose wire or connector.
- Inspect landing gear linkage, pivots, actuators. Look for binding, stuck gears, excessive play, broken parts.
- Review fault codes if available. Codes can point to specific component failures.
- Update control unit software. Software bugs may cause intermittent WOW faults.
- Replace control unit if all else fails. Faulty control units can cause false WOW signals.
Thoroughly inspecting the system and methodically testing each component is key to resolving tricky WOW issues.
Reference troubleshooting charts and wiring diagrams to fully diagnose faults.
Maintenance
Proper maintenance of weight on wheels sensors is critical for ensuring they continue to work properly.
Here are some tips for inspecting and replacing WOW sensors:
- Inspect sensors periodically. Even if the WOW system seems to be working fine, it’s a good idea to periodically inspect the sensors to check for damage or excessive wear. The sensors can get knocked out of alignment over time which can impact accuracy.
- Check sensor mounts. Make sure the sensor mounting brackets are tight and not bent or damaged. Loose or bent mounts can allow the sensor to move out of alignment.
- Look for leaks or corrosion. Inspect sensor electrical connections for any leaks or corrosion. Any moisture getting in can lead to shorts which will cause erratic readings or failures.
- Replace damaged sensors. If a visual inspection reveals any cracks, leaks or corrosion on the sensor, go ahead and replace it. It’s not worth risking failure of the WOW system.
- Use OEM or high quality parts. Don’t skimp on cheap aftermarket sensors. Stick with OEM or high quality name brand parts to ensure proper construction and accuracy.
- Recalibrate after replacement. Any time the WOW sensor is replaced, the system will need to be recalibrated to ensure accurate readings. Consult the vehicle service manual for the proper calibration procedure.
- Follow manufacturer service intervals. Many vehicle manufacturers recommend replacing WOW sensors at certain mileage intervals as preventive maintenance. Check service schedules and follow recommendations.
Properly inspecting and replacing worn WOW sensors is key to keeping this important system functioning reliably.
Don’t ignore this critical maintenance task.
Advancements
The weight on wheels system has seen major advancements and innovations over the years.
This is largely driven by the need for improved safety, efficiency, and performance in modern vehicles. Some key advancements include:
Electronic Weight on Wheels Switches
Traditional mechanical weight on wheels switches have been replaced by electronic versions in many new vehicles.
These electronic switches offer faster and more precise sensing of weight changes.
They also have built-in diagnostics to detect faults.
”Smart” Weight Sensing
New weight sensing technologies go beyond just detecting weight on wheels to actually determine the weight distribution across each wheel.
This allows for features like torque vectoring to optimize traction and handling.
Tire Pressure Monitoring Integration
By combining weight on wheels data with tire pressure monitoring, vehicles can accurately determine if an apparent weight change is due to low tire pressure or actual cargo load changes. This improves diagnostics.
Wireless Connectivity
Modern weight on wheels sensors can transmit data wirelessly to other vehicle systems. This enables more seamless integration and data sharing throughout the vehicle.
Predictive Technologies
Looking to the future, weight on wheels systems could preemptively adjust vehicle systems based on predicted weight changes by analyzing route topography, braking patterns, etc.
This proactive optimization would improve performance and efficiency.
The weight on wheels system will continue to evolve in tandem with broader vehicle automation and connectivity trends.
Leveraging the latest electronics and “smart” technologies promises to unlock even greater capabilities and benefits.
Weight sensing remains an essential input for vehicle dynamics, safety and efficiency.
History of Weight on Wheels Sensors
The origins of weight on wheels (WOW) sensor technology can be traced back to the 1980s when automotive engineers were looking for ways to optimize braking systems and traction control.
Early anti-lock braking systems (ABS) relied on simple speed sensors to detect when a wheel was locking up under hard braking.
However, these systems were limited because they couldn’t determine when the vehicle was actually on the ground versus up in the air.
Engineers realized that knowing when tires were loaded versus unloaded could help improve ABS performance.
This led to the development of the first WOW sensors, which were basic electromechanical switches mounted to suspension components.
They would open or close a circuit when the suspension was compressed under the vehicle’s weight.
Over time, the sensors evolved from simple switches to more advanced semiconductor-based strain gauges.
These gauges output a variable signal proportional to how much the suspension deflects.
This allowed more precise measurements of weight transfer dynamics.
WOW technology was soon applied beyond ABS to traction control, dynamic stability control, and suspension systems.
As vehicles became more computerized in the 1990s-2000s, WOW sensors became a critical input for overall vehicle dynamics and control.
Modern WOW sensors take various forms including optical, ultrasonic, magnetic, and hydraulic designs.
But they all serve the same essential purpose – detecting when a vehicle’s weight is on its wheels versus unsupported.
This provides vital information to optimize braking, acceleration, and handling.
As autonomous and electric vehicles continue advancing, WOW sensors will likely play an increasing role in enabling next-generation active safety, traction, and self-driving systems.
The origins of this technology in early ABS systems demonstrates how automotive innovation builds over decades, with each new capability enabling advances for the future.
Future Outlook
The future role of weight on wheels sensors in vehicles is expected to expand as automotive technology continues to advance. Here are some predictions for the future of WOW:
- More widespread adoption in economy vehicles. As the costs of WOW sensors decrease, they will likely become standard even in lower-cost vehicle models. This will improve safety and performance across a wider range of cars and trucks.
- Integration with advanced driver assistance systems. WOW data will be increasingly used to improve the functionality of automated driving features like automatic emergency braking, lane-keeping assist, and adaptive cruise control. The sensor data helps these systems better understand traction and grip.
- Connected to vehicle dynamics control. Future WOW sensors will probably connect directly to systems like traction control, stability control, and torque vectoring. This could enable even faster and more refined adjustments to keep the vehicle stable during maneuvers.
- Assisting electric powertrains. The instant traction data from WOW can help optimize torque delivery from electric motors. This prevents wheel spin, improves efficiency, and enhances performance.
- Self-calibrating and self-adjusting. With built-in microprocessors, future WOW sensors may self-calibrate as tires wear and self-adjust parameters for optimal performance. This reduces maintenance needs.
- Providing input for self-driving algorithms. WOW data will likely be valuable for the deep learning systems guiding autonomous vehicles. The traction and wheel load data can help optimize speed, acceleration, braking, and handling.
As vehicle technology progresses, weight on wheels sensors will play an increasing role in stability, safety, and performance.
More widespread adoption and integration with advanced systems seem highly likely in the future.
