Grooming

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Grooming: The most common form of trail maintenance, done to spread new snow and to smooth over bumps, icy patches and other obstacles. To groom, tractors known as Snowcats drag giant rakes over the snow; on steeper slopes, winches are used to drag rakes up the incline.
Grooming: The most common form of trail maintenance, done to spread new snow and to smooth over bumps, icy patches and other obstacles. To groom, tractors known as Snowcats drag giant rakes over the snow; on steeper slopes, winches are used to drag rakes up the incline.

Grooming: The most common form of trail maintenance, done to spread new snow and to smooth over bumps, icy patches and other obstacles. To groom, tractors known as Snowcats drag giant rakes over the snow; on steeper slopes, winches are used to drag rakes up the incline.

A groomer will usually go out to pack the snow and improve skiing and snowboarding and snowmobile trail conditions. The resulting pattern on the snow is known as corduroy in ski and snowboard slang, and is widely regarded as a good - albeit unexciting - surface on which to ski or ride. Snow groomers can also move snow made by snow machines. Groomers are mostly sent out during the night time after the close of the ski area so as not to interfere with daily and night skiing.


Contents

[edit] Important Characteristics of Grooming Tractors

There are several characteristics that are important to understanding the capabilities and the proper operation of grooming tractors. These characteristics include:

[edit] Ground Pressure

A vehicle that is designed to work in snow must stay on or near the surface rather than sink in and plow through the snow. This is accomplished by spreading the weight of the vehicle out over the tracks, much as a snowshoer’s weight is distributed by the snowshoes.

The technical measure of the vehicle’s ability to distribute weight is called ground pressure. Ground pressure is calculated by dividing the overall weight of the vehicle by the total area of the track which remains in constant contact with the snow and is most often expressed in pounds per square inch (psi) or kilogram-force per square centimeter (ksc).

Typical ground pressures for moderate-light to heavy grooming tractors range from 0.8 psi (0.056 ksc) to 1.2 psi (0.084 ksc). It is very important that tractor ground pressure not exceed these limits. If ground pressure is too high, the vehicle will sink into snow rather than stay on top. If ground pressure is too low, the unit may not have sufficient traction to pull a drag up hills or through deep, heavy snow.

[edit] Overall Weight

Within reasonable limits, the overall weight of the tractor can be compensated for by matching it with the appropriate track area. However, overall weight is a factor in terms of existing bridge loading limits and crossing frozen bodies of water. Because grooming vehicles are typically very heavy, it is recommended that they never be operated on frozen bodies of water without special planning, testing, and training since doing so could lead to equipment damage, serious personal injury, or death.

[edit] Engine Horsepower and Torque

Regardless of whether a diesel or gasoline engine is installed in a particular tractor, the key measurements of its capability are its horsepower and torque. Always use the same measurements when comparing horsepower, since there are gross, net, and power-take-off (PTO) measurements. Gross brake horsepower is a good basic unit for comparing the relative power of engines.

Engine torque is an overlooked rating that is very important for all grooming tractors. Torque relates to the ability of the tractor to get a heavy drag moving. The high static loads of modern multi-blade drags require a high degree of engine torque to get a drag moving from a dead stop.

[edit] Center of Gravity

A vehicle’s center of gravity is a point around which its weight is evenly balanced.

A vehicles center of gravity is significant any time it must operate on a non-level surface such as when climbing or descending steep grades or when side hilling. In terms of stability, the lower to the ground the unit’s center of gravity is the more stable it will be on non-level surfaces. Operators should keep this factor in mind to avoid getting into unsafe situations.

[edit] Tractive Effort and Coefficient of Friction

Tractive effort is defined as the amount of torque that can be applied to a track before the track looses traction and spins without moving the vehicle forward.

The coefficient of friction between the track and the ground or snow is the limiting factor of when the tracks will loose traction. Coefficient of friction is determined by the overall vehicle weight, the amount of track on the ground, the cross-link design of the track, and the weight distribution along the length of track that is in contact with the surface. The ideal weight distribution on the tracks is having the balance point, from front to rear of the vehicle, at or near the center point of the length of track.

When a track breaks traction it is actually shearing the snow through the force that the cross-links are placing on it. Fresh, unpacked snow shears much more readily than hard packed snow. When a vehicle breaks traction, spins out, and gets stuck, it happens because the force required to shear the snow is less than the force required to pull the load. The load is made up of both the drag and the tractor.

[edit] Also see

[edit] Reference


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