OnSpot
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OnSpot - Automatic Tire Chains (Swedish: OnSpot - det automatiska slirskyddet), originally called InstaChain[1], is a snow chain mechanism for applying and dismounting snow chains to and from the wheels of a vehicle. The automatic tire chain system was created in 1977 by the Swedish inventor Göran Torneback, who mounted it onto a local milk delivery truck. The system consists of two chain wheels operated by the driver. When the chain wheels are connected to the tire sidewalls, the chains are thrown, by rotation, under the tires so that at least one chain is always between the tire and the road surface. The system is designed to work on ice, packed snow, and up to 6 inches of snow, and is a refined application of a 1915 patent granted to the American inventor W.H. Putnam.[2]
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[edit] Function
The automatic tire chain system is permanently mounted on both sides of vehicle driving axle. The mechanism includes a chain assembly mounted with a plurality of chains rotated by a chain assembly driving unit mounted to an axle of a vehicle via a bracket. Also included is a control unit for controlling the chain assembly driving unit, thereby allowing the chains to be positioned between the wheels and road surface when the driver commands the snow chain mechanism to operate once the vehicle has been started.
The driver activates a dashboard switch that opens an electric over air solenoid mounted on the frame rail. Air pressure from the vehicle's on board air brake system or an auxiliary air source flows to two air cylinders that lower two chain wheels down until they contact the tire sidewalls. The friction between the tire and the chain wheel causes the chain wheel to rotate. Each chain wheel has 6 to 18 lengths of chain attached to it. The centrifugal force created causes the chains to flail out and pass between the tire and road surface to enhance traction in snow and ice in forward or reverse. The additional traction also reduces stopping distance in these same slippery conditions. When the switch is turned off, the solenoid exhausts the air in the cylinder and the spring in the cylinder returns the chains to the resting position.[3]
The system was originally designed to fit large vehicles with air brakes as the system requires a compressed air source to operate it. Many smaller vehicles without air brakes have been fit with the use of a 12-volt electric air compressor and holding tank.
[edit] Technical Specification
- Area of use Vehicle speeds: 0-50 km/h
- Activation time: 2 – 3 seconds
- Electrical voltage: 12 or 24 V
- Fuse: 8 A
- Air pressure: 7 – 10 bar
- Weight approx.: 18 kg/side, excluding brackets
- Chains: 6, 12 or 18 chains and 6 chains sparkle resistant
[edit] Disadvantages
The OnSpot system is intended to be used as a precautionary measure when slippery conditions are encountered in order to give a temporary improved grip both during driving and during braking. Automatic chains may give a driver the sense of false security. The driver must realize that this system is not a fix all and the system must still be turned on. The system is designed to work on ice, packed snow, and up to 6 inches of snow. Automatic chains are ineffective in 15 inches of snow, so the driver may have to resort to installing conventional snow chains in deep snow conditions.
[edit] See also
[edit] External links
- OnSpot - Push for safety Catalogue of 2007.
[edit] Video
[edit] Notes
- OnSpot - Automatiska slirskydd VBG Group.
- ^ The name was changed to OnSpot as InstaChain was already a protected trademark. According to the American general supply agent the word "OnSpot" means "instant" in Swedish, but that claim is debatable and not at all supported by the Swedish Academy.
- ^ United States Patent No. 6830134 of August 17, 1915.
- ^ How does it work? by Patrick Freyer.
