ViaFriction is used for measuring the friction levels on roads and runways.

General

ViaFriction is a one-wheeled friction measuring device pulled by a vehicle. It is designated a CFME (Continuous Friction Measuring Equipment). Its main task is to measure the friction of the pavement surface, in both winter and summer conditions. The friction between the measuring wheel and the surface is continuously measured, while a unique measuring technology, developed and patented by ViaTech, ensures that the data is stable and reliable, even under volatile conditions. This reduces the need for calibration significantly.

The device has very few moving parts — which makes ViaFriction almost maintenance free. Over 200 ViaFriction devices have been delivered since 2006; all of them are still in use, which is a testament to their durability. ViaFriction utilizes an electric braking system to be able to measure the friction coefficient. This system doubles as a heating device, keeping the friction measuring device free of ice and snow under winter conditions.

Through rigorous testing, it has been proved that ViaFriction has superior characteristics compared with other friction testers on the market. ViaFriction gives repeatable measurements for various conditions and retains its calibration over time. Our customers range from universities to road authorities and private companies around the world.

The device will run freely behind the vehicle under transport. It may also be delivered with an electric lifting device, which will hover ViaFriction over the pavement surface when not in use. See the images to the left for an illustration of this lifting mechanism.

ViaFriction is normally delivered as trailer solution. The device can run using batteries, but may also be connected via 12V/40A connector for battery charging. ViaFriction communicates with the computer in the car using a wireless link or an Ethernet cable. The trailer solution makes the friction meter independent of one specific vehicle and does not require vehicle-specific installation.

Technology

The measured friction and friction force depends on the normal force on the measure wheel, and the speed difference in between the measure wheel and the vehicle. In order to obtain accurate measurements, it is important to have an accurate control of the speed and a good measurement of the normal force.

Most friction testers currently on the market have a fixed speed difference in between the measure wheel and the vehicle. ViaFriction uses an electrical brake to control the speed of the measuring wheel. The brake is controlled by a computer. This solution results in a control system with extremely low response time and an accurate control of the speed of the measuring wheel. It also allows measurement modes not possible for devices on the market today (such as SCRIM, Griptester, MuMeter etc.).

ViaFriction utilizes a normal (vertical) force of 1200N independent of movements of the trailer. An advanced suspension system ensures that the vertical force is constant, even on uneven roads.

Our summer trailer design includes two separate damping systems providing a unique driving comfort.

Standards

ViaFriction conforms to the following standards:

• ASTM E2340: Continuous fixed-slip measurement
• ASTM E1551-08: Smooth test tire for fixed-slip friction testing
• CEN TS 15901-14:2016: Procedure for determining the skid resistance of a pavement surface using a device with longitudinal controlled slip
• ASTM F408-99: Standard Test Method for Tires for Wet Traction in Straight-Ahead Braking Using a Towed Trailer

Summer measurement

It is very important that the water film used to cool the tire is constant and has an even thickness (0.5mm on roads 1.0mm on airports). It is also important that the water spray does not wash the road surface for contaminants. The advanced pump system measures the vehicle speed and calculates the the correct water speed, so that no washing action is done.

Devices delivered for all-year operation will include a water tank for this purpose. The tank may be placed inside the car, or — if a bigger tank is needed — in a separate trailer. In the case of a separate trailer, the ViaFriction may be mounted directly on the trailer.

Winter measurement

Winter measurements will expose the device to low temperatures, salt, gravel, etc. ViaFriction is built from the highest-quality materials and components to ensure optimal results, even in the unforgiving winter environment. The heat that ViaFriction produces under operation will keep the device free of ice and snow.

Running during the winter does not require the watering system explained above. As such, the device can be delivered as a winter-only version, without this system. The small winter-trailer is accredited by the Norwegian Road Authorities.

Mounting

As an independent device, ViaFriction may be mounted in a number of fashions. Some of the possible configurations are listed below; though, more are possible. The slideshow to the right illustrates the mounting options. Contact our sales department for more info about custom mounting.

The device may be mounted

• On a trailer exclusively for winter measurement
• On a summer trailer including a water tank, EU CoC.
• Underneath a truck
• Directly on the back of a vehicle

A more advanced option is possible for covering split friction where 2 (or even 3) ViaFriction measuring units covers both the left and right wheel path, and the optional third, the center path.

Measuring Modes

ViaFriction supports several measurement modes such as fixed slip, variable slip and surveillance.

Fixed slip

The fixed slip mode is when the measure wheel speed is a percentage of the vehicle speed. This is identical to measurement modes used by most friction testers. In order to obtain repeatable results in fixed slip, the measurement must be performed in a fixed speed. The measured friction varies with the speed difference in between the measure wheel and the vehicle.

Surveillance

The surveillance mode is a variant of the fixed slip mode where the actual friction measurement does not take place unless the friction level is below a given value. The surveillance mode greatly reduces wear on tire and apparatus.

Variable slip

The Variable slip mode measurement is achieved by conducting wheel braking from free rolling to almost fully-locked and measuring the breaking friction force which the road surface exerts against the breaking wheel.

Interface

The driver operates the ViaFriction tester using a Windows PC program. The program can, in addition to the normal PC interface, be operated using a LCD touch screen. The measurements can be transferred via mobile broadband from the vehicle to the decision-makers using ViaLink, a memory stick or by uploading in real-time to ViaWEB. These measurements can then be analyzed using ViaPlot or Microsoft Excel. Recording of friction measurements is often combined with ViaPhoto for documentation of the road standard and executed maintenance work.

Technical specifications

Physical dimensions
Dimensions (with winter trailer)	Height: 830 mm, Length: 2030 mm, Width: 1790 mm (32.7, 79.9, 70.5 in)
Dimensions (with summer trailer)	Height: 1860 mm, Length: 4780 mm, Width: 2160 mm (73.2, 188.2, 85.0 in)
Dimensions (friction meter only)	Height: 830 mm, Length: 1150 mm, Width: 405 mm (32.7, 45.3, 15.9 in)
Weight (with winter trailer)	180 kg (397 lbs)
Weight (with summer trailer)	2050 kg, inc. 1000 kg water (4520 lbs, inc. 2200 lbs water)
Weight (friction meter only)	80 kg (132 lbs)
Measurement speeds
Measurement speed:	20 - 95 km/h (12 - 60 mph)

Fixed slip

The slip percent can be set to any percentage from 1% to 75%. Typically slip percentage during measurements is 20% under winter conditions and 18% under summer conditions.

Variable slip
µ-peak	Variable slip friction value, calculated at the peak effect of the braking measuring wheel.
F60	The friction value at 60 km/h slip speed.
F30	The friction value at 30 km/h slip speed.
Sp	The speed/friction curve slope at the F60 point, alternatively the F30 point.

Miscellaneous

Data format

ViaTech can supply the measurements to ViaPlot analyzing tool, Microsoft Excel or a format of your choice.

Maintenance

ViaFriction consists of few, but high-quality parts and is a long-lasting friction meter which requires limited maintenance. If parts have to be replaced, there is no need for special tools. In addition, the normal force on the measuring tire is low, reducing the wear. This further reduces the overall maintenance cost.

Calibration

ViaFriction will be delivered fully calibrated.

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