US Patent 8042629 Snow traction unit for vehicles

A snow traction unit to replace a wheel of an all wheel drive vehicle which includes a frame supporting two carrier wheels; said carrier wheels being spaced apart a distance greater than their combined radii; an endless snow contacting track mounted for rotation on said carrier wheels; a track contacting surface provided between the lower extremities of said carrier wheels; a drive engagement means for engaging the drive shaft of the vehicle and for driving at least one of said carrier wheels; the arrangement of the width of the track, the spacing between the carrier wheels and the track contacting surface resulting in the vehicle having a force imprint less than 250 Kg/square meter.