The ONSPOT Automatic Tire Chain System offers the traction of a single set of conventional snow chains without having to stop the vehicle. The cab-mounted electric switch provides 12 volts to an air solenoid on the vehicle’s frame rail. Compressed air to the solenoid is supplied from either the vehicle’s onboard air system or a 12-volt compressor. The solenoid opens when the dashboard switch is activated, allowing compressed air to enter the air cylinder and lower the chainwheel so it contacts the inside of the tire. The friction between the tire and the rubber-covered chainwheel causes the chainwheel to rotate, creating enough centrifugal force to flail the chains out. Six lengths of chain spaced at 60-degree intervals on the chainwheel ensure that there are two chains between the tire and road surface at all times, whether the vehicle is accelerating, braking or in a wheel lockup condition. When the dashboard switch is turned off, the solenoid exhausts the air provided to the chain units and return springs in the air cylinders, bringing the chainwheels back to their resting position.
The tire chain system is available from more than 200 OEMs and 1,400 dealers. ONSPOT, founded in 1977, manufactures its products in the company’s ISO 9001-certified factory in Indiana.