Mycket text, men den innehåller några intressanta partier. (Moguls = engelska ordet för dom där jäkla knölarna som blir på leden hela tiden...)
General Guidelines for Snowmobile Trail Grooming Copied from the NYS Office of Parks, Recreation, & Historic Preservation Training Manual and Workbook
Mogul Formation
The primary reason that snowmobile trail grooming is necessary is the continuous formation of moguls by passing snowmobile traffic. Moguls are patterns or mounds and dips formed in the trails snow covering perpendicular to the direction of travel. Moguls are formed just as washboards are in gravel roads. Just as gravel roads have to be graded, snowmobile trails have to be groomed. Moguls are as onerous to snowmobilers as washboards are to motorists. Moguls tend to form wherever snowmobiles accelerate quickly or slow down abruptly. Before and after curves, approaching and leaving stop signs, before and after bridges, in short everywhere! Moguls tend to form in long coherent stretches or runs. Passing snowmobile traffic causes the mounds to get higher and the dips to get deeper, the same distance apart from one another in a constant unchanging rhythm which pounds machine and rider.
Trail Grooming Theory
The primary purpose of grooming is to remove moguls. This is not simply a matter of knocking the top of one mound and pushing the snow into the next dip. Drags which accomplish this may appear to leave a flat trail. However the resulting uneven density will produce a poor ride even though the trail looks smooth and the trail will quickly revert back to moguls as the soft snow gets pounded out of the low spots. Regardless of the design of the grooming drag, it must perform 4 basic operations in order to produce a well groomed trail.
Step 1. Removing moguls and side berms
To remove moguls and berms they must be completely cut away from the snow which forms the trail base! Generally it is more efficient to start from the outside edge and work towards the center.
Step 2. Processing the Snow
Snow processing is accomplished by the establishment of the rolling or churning action in front of the blades of the drag as they move forward at a correct and constant speed. In some drag designs, the blades are angled so that the snow moves from side to side further mixing and homogenizing it. The churning and tumbling action breaks up the compacted snow from which the moguls were formed, into small granules of various sizes. It also "ages" new snow by breaking away the points from the individual snow flakes so they can be compacted much more tightly. The mechanical action of the churning and tumbling has another important purpose in that it introduces moisture into the snow mix due to friction. Moisture is very important to the success of the last step, and this feature of processing is especially valuable when the snow is very dry, such as lake effect snow. Finally, all the processed snow is mixed and homogenized into an even blend of moist, loose particles ready for compacting.
Step 3. Compacting the Snow
The moist, loose snow created by the processing step must be compacted into and even covering of uniform density with a smooth surface. This step is accomplished by a flat packing pan at the rear of the drag. The front of the pan is angled up so the loose snow is captured and pulled under the flat pan where it is compressed by the weight of the moving drag.
Step 4. Set Up
The last step in the grooming process is to allow the moisture created during the processing to re-freeze. This binds the individual granules of tightly packed snow firmly together creating a hard surface which will withstand passing traffic much better. The length of time needed for a trail to set up correctly can vary from 1 to 6 or more hours, depending on the temperature and the moisture content of the snow. It is vital that the trail remain undisturbed during this period! Consequently, many clubs groom at night when traffic levels are low and the temperatures generally are cooler. It is recommended that grooming should occur at night after traffic subsides. This provides safe operation and more effective grooming, as there is more time for the trail to set up before traffic resumes.