referring again to the drawings , there is shown in fig1 a wind machine , generally designated as 10 , mounted at a portion of a terrain area 12 having a variable contour . the wind machine is positioned centrally on the area on which it is to be effective . the mounting is comprised of an embedded concrete block 14 on which is secured a hollow , cylindrical tower 16 . the wind machine is driven by a power source 18 which may be an electric motor or an internal combustion engine . connected to the power source is a reduction gear box 20 , and upwardly extending therefrom is a vertical driving shaft 22 which rotates at a reduced speed relative to the motor 18 . the driving shaft rotates within bearings 24 centrally positioned within the tower and supported therein . fixed to the tower is a ladder 28 to provide access to a fan drive assembly , generally designated as 30 , secured for rotation at the top of the tower . the fan drive assembly is comprised of a housing or fan drive housing 32 , a fan shaft assembly 34 and a fan assembly 36 . in fig2 the fan drive assembly is shown in detail . connected to the shaft 22 by means of a coupling 40 is a vertical shaft portion 42 extending through a fixed fan drive assembly mounting means or yoke 44 . the mounting means 44 is generally conical , tapering downwardly , and at its upper end has an annular flange 46 , secured to an annular plate 48 by means of bolts 50 . the plate 48 is secured to the top of the tower 16 and has a central opening 52 through which the mounting means 44 extends . at the lower end of the fan drive assembly is a conical support member or hub 54 , complementary in configuration to a generally inner conical surface 56 of the yoke 44 . the hub 54 is bearing mounted for rotation on annular bearings 58 and 60 . the shaft portion 42 is splined or otherwise secured to a member 64 of the coupling 40 , and extends through a central opening 68 of the hub 54 . the shaft portion 42 is also mounted in bearings 70 and 72 secured within the central opening 68 . the bearings 72 are secured in place by an annular plate 74 mounted on surface 76 at the top of the member 54 . the plate 74 has a central opening 78 through which the shaft portion 42 extends . mounted on the shaft portion 42 within an oil reservoir 82 of the fan drive housing is a bevel gear 80 supported by bearing 72 . engaged with the bevel gear 80 is a complementary bevel gear 84 mounted on an inner portion 86 of the fan shaft assembly 34 . the inner shaft portion 86 is mounted for rotation within the housing on bearings 88 and 90 , the latter being secured within oil reservoir closure plate 91 . to the left , and outwardly of the oil reservoir , the inner shaft 86 extends into a reduction gear box 92 . at the end of the shaft within the box 92 is a worm gear 94 engaged to reduction gears , not shown , and from which extend downwardly a shaft 96 on which there is secured a pinion 98 . the pinion 98 is engaged with a fixed ring gear 100 secured on the circumferential edge of the flange 46 , also shown in fig1 and 3 . rotation of the pinion 98 on the ring gear 100 causes the fan drive assembly to rotate 360 ° to direct the forced air over the terrain surrounding the tower . to the right of the housing 32 extends an intermediate portion , generally designated as 104 , of the shaft assembly 34 . the intermediate portion 104 is comprised of an extension 106 of the portion 86 , connected to one end 108 of a heavy duty universal joint 109 , the other end 110 of the universal joint being connected to an outer shaft portion 112 of the shaft assembly 34 . the universal joint permits portion 112 to be tilted upwardly and downwardly with respect to the fan drive housing . the fan assembly 36 , as shown in fig1 is secured on the outer end portion 112 . as shown in fig2 - 5 , the outer shaft portion 112 is supported within a housing 114 of a shaft tilting member , generally designated as 116 , on bearings 118 and 120 for rotation therein . the shaft is secured in the hub by locking nut 117 . extending downwardly from the housing 114 are follower arms 122 , having mounted on their lower ends a cam follower or roller 124 rotatable on a generally vertical shaft 126 . in the preferred embodiment the roller 124 is adapted to follow a generally vertical cam surface 128 on a radial , generally annular two part cam 130 , preferably secured to the outer cylindrical surface of the tower 16 by at least one clamping member 132 . as best seen in fig3 and 5 , there is illustrated two clamping members 132 and 134 which are joined at their ends by radially directed flanges 136 and 138 , and they are secured on the tower 16 by means of bolts 140 , the flanges being in abutment so there is effectively no interruption of the cam surface 128 . this arrangement permits the cam , specific to a particular terrain , to be positioned relative to the terrain during installation of the machine . while two clamping members 132 and 134 are illustrated , it should be realized that a single clamping member and a hinge means on the cam may be used without departing from the spirit of the invention . one end 144 of a shock absorber 146 is pivotally mounted on a plate 148 secured to the follower arms 122 and the other end 150 of the shock absorber is pivotally mounted to a ring face plate 152 on the closure 91 . the shock absorber may limit the upper tilting movement of the shaft portion 112 and the fan assembly and dampens any surging movement which may occur in the fan shaft . as shown in fig3 and 4 , additional support means , generally designated as 156 , are provided to support the outer shaft portion 112 and to restrict the universal joint and the fan assembly against lateral movement . the support is comprised of two diametrically spaced trunion arms 158 mounted on ring 152 . adjacent their outer ends , the trunion arms have cylindrical openings for supporting pivot pins 162 , secured adjacent one end of arms 164 which are secured at their other ends to shaft housing 114 by means of bolts 166 . thus , when the fan assembly and shaft portion 112 are moved upwardly and downwardly , the pivot pins 162 rotate in the trunion arms 158 . in fig5 the cam surface 128 is shown in detail . for the point where the roller is in contact with the cam , the shaft portion 112 and the fan assembly are tilted upwardly a maximum amount in accordance with the lowest portion of the terrain . when other areas of the cam , such as 170 , are engaged by the cam follower , the fan assembly is tilted downwardly with respect to higher areas of the terrain for which the cam is specifically made . similarly , at point 172 the fan assembly is tilted downwardly its maximum amount to cause the air stream to be directed toward the higher part of the land at the same angle it is directed to the surface of all the other contour variations . from appropriate data based upon appropriate topographic surveys the cam surface 128 may be determined . the cam is then secured to the tower by means of the clamping members 132 , 134 and positioned so that when the fan assembly is rotated by the pinion 98 engaged with the ring gear 100 the fan will produce an air stream at an appropriate angle with respect to the varying land contour . in fig7 another embodiment of the invention is shown in which a vertical cam 180 has a generally horizontal cam surface 182 derived in the same way as the cam surface 128 . in this embodiment the cam follower roller 184 has a generally horizontal axis . as shown , at point 186 on the cam the fan assembly is tilted to its highest position and is lowered , tilting downwardly , when the cam follower is moved so that the cam follower rides on point 188 , for example . in fig6 having the same cam as shown in fig5 a different type of tilting limiting means 190 is shown . it is formed of a metal strut and has a plate at its outer end 192 which is adapted to make contact with an extension 194 on the fan shaft housing . thus , when the fan shaft housing is moved to an upper position to make contact with the strut , it is thereby limited in its upper movement . the upper limit is to prevent the fan from being moved upwardly to a position where it might be damaged . in operation , the engine or motor is started and the fan is caused to rotate at about 590 rpm . the rotation of the fan shaft causes the pinion 98 to rotate on the ring gear 100 so as to rotate the fan drive assembly on the tower at the rate of about 41 / 2 minutes per rotation . as the fan drive assembly rotates , the cam follower follows the cam surface causing the fan assembly to be tilted upwardly and downwardly in accordance with the terrain variation . as shown in fig1 the cam follower 124 is on a high point on the cam causing the fan assembly to have been tilted upwardly so that the air flow from the fan is directed downwardly to the proper angle with respect to the terrain . as the cam follower continues to rotate with respect to the cam , it moves to cam surfaces which causes the fan to be tilted to direct the air flow at the proper angle with respect to the terrain for all points through the 360 ° rotation of the fan drive assembly . the invention and its attendant advantages will be understood from the foregoing description and it will be apparent that various changes may be made in the form , construction and arrangements of the parts of the invention without departing from the spirit and scope thereof or sacrificing its material advantages , the arrangements hereinbefore described being merely by way of example . i do not wish to be restricted to the specific forms shown or uses mentioned except as defined in the accompanying claims , wherein various portions have been separated for clarity of reading and not for emphasis .