Snowmobile ski with increased stability
A snowmobile ski having improved turn stability. The ski includes a lower surface for sliding contact with snow, the lower surface being configured with at least one longitudinally extending, downwardly open groove having an internal cross-section dimension that diminishes rearwardly to thereby progressively constrict the groove. The groove is open forwardly to receive snow within it and is open rearwardly to enable snow to exit from the groove. Snow received within the groove becomes packed when such snow encounters the progressively constricted portions of the groove as the ski slides forwardly on a snowy surface.
The invention pertains to snowmobile skis and more particularly to skis that have enhanced turning stability.
BACKGROUND OF THE INVENTIONAs a snowmobile or other ski slides through snow, turning of the ski promotes sideways slippage in a manner that is well known to downhill skiers and snowmobilers. In downhill skiing, a certain amount of side slip is desirable to enable the skis to be orientated as turns are made. Here, side slippage is controlled by causing the edges of the skis to bite into the snow in a controlled manner.
In contrast, side slippage of snowmobile skis is to be avoided. Snowmobile skis desirably bite into the snow surface and resist sidewards slippage as much as possible. One way of promoting this function is to configure the bottom, snow-contacting surface of a ski so that it contains one or more longitudinally extending, downwardly protruding ribs, the ribs having as their purpose the reduction of side slip by biting into the snow being traversed.
In general, as a snowmobile ski is turned and begins to slip sideways, snow at the outer portion of the ski is pushed sideways and as a result the snow surface is fractured to some extent. The use of longitudinally extending bottom ribs to some extent promotes stability by digging into the snow, but better stability is to be desired. Excessive sideslip can be avoided, of course, by going slow, but as a rule, slow speeds are not appealing to snowmobilers.
SUMMARY OF THE INVENTIONThe present invention employs a unique configuration of the lower sliding surface of a snowmobile ski to promote stability, particularly during turns. Broadly speaking, snowmobile skis may be provided with a lower surface having a longitudinal groove or channel that tapers from front to rear, becoming smaller in cross-section toward the rear. Snow entering the front of the channel thus is compressed as the ski slides forwardly and the snow in the channel encounters smaller channel cross sections. This, in turn, causes snow within the channel to pack or compress and to thus “harden” the snow in the channel, providing a hardened ridge or rail of snow against which the ski presses, the packed and hardened snow ridge functioning to control side slip.
In one embodiment, the invention provides a snowmobile ski that comprises a generally ski-shaped body with a longitudinal axis and forward and rearward ends, the ski having a lower surface for sliding contact with snow. The lower surface is configured with at least one longitudinally extending, downwardly open groove having an internal cross-section dimension that diminishes rearwardly, to thereby progressively constrict the groove rearwardly. The groove is open forwardly to receive snow within it and is open rearwardly to enable snow to exit from the groove, whereby snow received within the groove becomes packed more tightly when such snow encounters progressively constricted portions of that groove as the ski slides forwardly on a snowy surface.
In another embodiment, the invention provides a snowmobile ski with a generally ski-shaped body and forward and rearward ends, the ski having the lower surface for a sliding contact with snow, the lower surface having a downwardly protruding, longitudinally extending rib positioned intermediate longitudinal edges of the ski. The lower ski surface is recessed to define longitudinally extending grooves on each side of the rib, each groove having an internal cross-section dimension that dimishes rearwardly to thereby progressively constrict the groove.
In a preferred embodiment, a snowmobile ski is provided that has a generally ski-shaped body with a longitudinal axis, forward and rearward ends, and a lower surface for sliding contact with snow, the lower surface having at least one longitudinally extending groove that opens forwardly and downwardly to receive snow as the ski slides forwardly. The groove has laterally spaced confronting sidewalls that converge rearwardly to cause snow within the groove to pack more tightly near the rearward end of the groove as the ski slides forwardly on a snowy surface.
BRIEF DESCRIPTION OF THE DRAWINGS
Referring first to
Referring to
The structure of the rib and grooves can perhaps be best understood with reference to
Referring now to
The schematic cross section of
In
The schematic cross-section of
If desired, the height of the groove 32 above the lower ski surface 28 can be varied to progressively rearwardly constrict the groove, and, of course, the rib itself can be varied in cross-section as desired to provide an internal cross-section dimension, e.g., lateral groove width, that diminishes rearwardly of the ski. However, the height of the groove 32 above the lower surface 20 of the ski desirably is kept fairly uniform for ease of manufacture. Moreover, although the groove 32 is shown in the drawing as having a generally flat upper surface, the groove can be configured as desired, e.g., the upper surface of the groove may be made arcuate to present a generally concave or convex surface downwardly.
The ski itself desirably is molded in a one-piece from a polyolefin such as polyethylene, high molecular weight polyethylene, or ultra high molecular weight polyethylene (“UHMWPE”). If desired, the upper portion of the ski may be molded from one polyolefin, and the lower portion of the ski from another polyolefin. For example, the upper portion of the ski may be of low-density polyethylene and the bottom portion of the ski of UHMWPE. If desired, the ski may be made of a variety of other materials, including other polymers, metals and the like.
Ultra high molecular weight polyethylene is preferred, at least for the snow contacting portions of the ski, and appropriate molding methods are employed to assure good results. In the molding process, UHMWPE particles, commonly in flake form, are introduced into an appropriately configured mold. The mold is closed and pressure in the range of about 1200 to about 2000 psi, preferably about 1500 psi, are applied to the mold contents as the temperature is raised. The mold is heated to molding temperatures in the range of about 300° F. to about 400° F., preferably about 375° F., the pressure being controlled carefully while the mold is at a temperature within about 25° F. of its highest molding temperature. As the temperature of the mold is increased to cause fusion of the UHMWPE particles, followed by cooling of the mold, volumetric changes in the resin require adjustment of the molding conditions in order to maintain the desired pressure. This can be accomplished through the use of commercially available hydraulic servomechanisms. After cooling, the ski is removed from the mold, and flash, if any, is removed.
In use, as a snowmobile is driven across the snowy surface, snow is received within the forward portion of the groove 32 where the groove has the greatest cross-sectional dimension, i.e., the greatest lateral width. The snow, although remaining substantially stationary with respect to the line of travel of the ski, encounters progressively constricted portions of the groove, and the snow itself will become compacted so as to form a hardened track or rail of compacted snow. Downward compaction of the snow also occurs, of course, due to the weight of the snowmobile. It is believed that the compacted track or rail in this fashion, against which the walls of the groove may push in a transverse direction as the ski is turned, provides resistance to sideways slippage of the ski during a turn. Snow compaction in the groove also occurs as the inner, sloping sidewall 36 provided by the rib pushes sideways against snow during a turn. It may also be noted that the intermediate portion 28 of the rib extends downwardly beyond the plane joining the lower ski surfaces 20, the rib here providing not only sidewalls against which snow can be compacted, but also downwardly extending portion that digs into the snow to provide added stability.
While a preferred embodiment of the invention has been described, it should be understood that various changes, adaptations and modifications may be made therein without departing from the spirit of the invention and the scope of the appended claims.
Claims
1. A snowmobile ski comprising a generally ski-shaped body with a longitudinal axis and forward and rearward ends and having a lower surface for sliding contact with snow, said lower surface being configured with at least one longitudinally extending, downwardly open groove having an internal cross-section dimension that diminishes rearwardly to thereby progressively constrict the groove, said groove being open forwardly to receive snow within it and open rearwardly to enable snow to exit from the groove, whereby snow received within said groove becomes packed when such snow encounters progressively constricted portions of that groove as the ski slides forwardly on a snowy surface.
2. A snowmobile ski comprising a generally ski-shaped body with a longitudinal axis and forward and rearward ends and having a lower surface for sliding contact with snow, said lower surface having a downwardly protruding, longitudinally extending rib positioned intermediate longitudinal edges of the ski, said lower surface being recessed to define longitudinally extending grooves on each side of at least a portion of said rib, each groove having an internal cross-section dimension that diminishes rearwardly to thereby progressively constrict the groove, each groove being open forwardly to receive snow within it, whereby snow received within a groove becomes packed more tightly when such snow encounters progressively constricted portions of that groove as the ski slides forwardly on a snowy surface.
3. A snowmobile ski comprising a generally ski-shaped body with a longitudinal axis and forward and rearward ends and having a lower surface for sliding contact with snow, said lower surface having at least one longitudinally extending groove that is open forward and downward to receive snow within it as the ski slides forwardly upon a snow surface, the groove having laterally spaced confronting side walls that converge rearwardly to cause snow within the groove to pack more tightly nearer the rearward end of the groove as the ski slides forwardly on a snowy surface.
4. The snowmobile of claim 3 wherein at least one of said side walls is undercut.
5. The snowmobile ski of claim 3 wherein said lower surface includes two of said longitudinally extending grooves, said grooves being generally parallel and laterally spaced from each other.
6. The snowmobile ski of claim 5 wherein said lower surface includes a downwardly protruding, longitudinally extending rib having walls defining inner side walls of said grooves with said grooves extending on each side of said rib.
7. The snowmobile ski of claim 6 wherein said rib is generally dove-tail shaped in cross section, the rib increasing in lateral width downwardly.
8. The snowmobile ski of claim 6 wherein one side wall of each groove is an outer side wall confronting a side wall provided by said rib.
9. The snowmobile ski of claim 8 wherein said outer side walls are convergent rearwardly toward respective confronting inner walls.
10. The snowmobile ski of claim 9 wherein said rib is substantially uniform in cross-section throughout the majority of its length.
11. The snowmobile ski of claim 10 wherein said rib is generally dove-tail shaped in cross section, the rib increasing in lateral width downwardly.
12. The snowmobile ski of claim 10 wherein said inner walls have a vertical height greater than said outer walls.
13. The snowmobile ski of claim 1 wherein said body is molded of a polyolefin.
14. The snowmobile ski of claim 13 wherein said polyolefin comprises an ultra high molecular weight polyethylene.
Type: Application
Filed: Jan 24, 2005
Publication Date: Jul 27, 2006
Inventors: Todd Huntimer (Arlington, SD), Jody Lemme (Arlington, SD), Daniel Palli (Nunda, SD)
Application Number: 11/041,668
International Classification: A63C 1/30 (20060101);