in the figures , a skate and a skateboard with various schemes are constructed in accordance with the present invention . fig1 is the single - foot manipulatable skateboard ; fig2 is the skate having the minature of skateboard . fig1 a is the cross section view taken at the line i -- i as shown in fig1 c . fig1 c is the top view of the skateboard . in fig1 d , the rider stands on the board 1 and steps on the pedals alternatively to skate forward and backward . in fig1 e , the rider stands on the pedals twisting the pedals to skate forward and backward . the rims 27 of the pedals 21 and 22 hold the shoes during steering . the skateboard comprises an elongated board 1 , a pair of pedals 21 and 22 , slipper belts 32 and 36 , a pair of rods 51 and 52 , a pair of trucks 41 and 42 , wheels 9 , pivotal joints 43 or ball joints 44 , crankshafts 8 and the protection strips 20 . the front portion of the left foot treads on the front pedal 21 . the heel of the right foot treads on the rear pedal 22 . standing on the board , the rider swings the body weight forward and backward . accordingly , the left foot treads on the front pedal 21 and the right heel treads on the rear pedal 22 alternatively . the front pedal rod 51 and rear pedal rod 52 move downward and upward alternatively . the left foot inserts in the slipper belt 31 . the front portion of right foot inserts in the rear slipper belt 32 . as the rider jumps , the skateboard is carried in the air by the feet of the rider . fig1 d also shows the minor modifications of the skateboard . the front foot steps on the front pedal 210 ; the rear heel steps on the rear pedal 220 . stepping on the front pedal 210 and rear pedal 220 alternatively , the skateboard will skate forward and backward . the bottom rigid plate 471 and the top rigid plate 472 are an integrated unit . the plates 471 and 472 clamp the resilient bushing 470 . fig1 e shows the twisting operation of the skateboard . the rider stands on the pedals and twists the pedals , the skateboard may skate forward and backward . fig2 is a skate which is a minature of the skateboard . fig2 a is the skate with the ball joint 44 . the shoe 37 has a pad 38 . the pad may fit inside the hole 48 . the universal ball joint 39 seats inside the pad 38 . fig2 b is the top view taken at the line x -- x in fig2 a . fig2 c is the skate having the front portion of the skate attached to the shoe . the rider can use the heel to drive the skate . tilting the skate , the steering bar 113 can force the trucks 41 and 42 to rotate and change the direction . fig3 a is the partially exposed section view of the wheel assembly with the ball joint ; fig3 b is the partially exposed cross section of the engaging mechanism having upper - bounded gripping force embedded in wheel assembly . fig3 c is the partially exposed cross section of the engaging mechanism having the noncontact force embedded in wheel assembly . fig4 a is the cross section view of the wheel assembly with a pivotal joint ; fig4 b is the partially exposed section view having the upper - bounded gripping force engaging mechansim embedded in wheel assembly . fig4 c is the partially exposed cross section of the noncontact force engaging mechanism embedded in the wheel assembly . fig5 a is the cross section of the pedal rod 51 , resilient bushing 489 and the ball joint 44 taken at the cross section v -- v in fig3 a . passing through the pivotal joint 43 , fig5 b is the cross section of the pedal rod 52 taken at the cross section vi -- vi in fig4 a . fig5 c is the resilient joint made of the resilient bushing as shown in fig1 d . referring to fig3 a , the ball joint 44 has the protrude 45 . the protrude 45 is enwrapped by the resilient bushing 48 . there is a metal bushing 488 between the protrude and the resilient bushing to reduce the friction . the resilient bushing 489 serves as the shock absorber in jumping and enables steering and recovering to straight forward position . the spring 6 is optional . the spring 6 expands to bias against the pedal 21 . the pedal rod 51 is pushed up by the spring 6 . in fig3 a , the link 7 pulls the crankshaft 8 up to the top dead center . the link 70 in fig1 is corresponding to the link 7 in fig3 . the tiny slot 79 is optional . in the following discussion , the link 7 having no tiny slot 79 is discussed first . the sliding rod 50 is corresponding to the pedal rod 51 ; the crank 80 is corresponding to the crankshaft 8 . the circle 71 has the link 70 to be radius . the tip of rod 50 is the center of circle 71 . the circle 81 has the crank 80 be radius . the circle 71 shifts upward and downward with the rod 50 as shown in fig1 d . the position of the link 70 and the crank 80 is determined by the intersection point of the circles 71 and 81 . in fig1 a , the sliding rod is pushed down to the bottom dead center , the link 70 and the crank 80 coincide with each other . the circle 71 is tangent to the circle 81 . there is only one intersection point . in fig1 b , the sliding rod 50 is in the middle of the sliding range . the circles 71 and 81 have two intersection points . in fig1 c , the sliding rod 50 is pulled up to the top dead center . the crank 80 is in line . the circles 71 and 81 are tangent to each other . there is only one intersection point . as shown in fig1 d , overlapping the circles 71 in fig1 a , fig1 b and fig1 c together , it shows the trajectory of the crank mechanism . as shown in fig1 a , in the upper half cycle , as the sliding rod 50 is pushed downward , the crank 80 rotates counter - clockwise . as shown in fig1 b , as the sliding rod 50 is pulled upward , the crank 80 rotates clockwise . as shown in fig1 a , in the lower half cycle , as the slidling rod 50 is pushed downward , the crank 80 rotates clockwise . as shown in fig1 b , as the slidling rod 50 is pulled upward , the crank 80 rotates counter - clockwise . however , pushing the rod 50 down at the top dead center or pulling the rod 50 up at the bottom dead center , the crank 50 cannot decide which direction to rotate . as shown in fig3 a , to have the selectivity of rotational direction , there is a tiny slot 79 on the link 7 . the pin 15 slides in the slot 79 . the slot 79 provides the mechanism to have the selection of rotational direction . the direction selection mechanism is shown in fig1 . as the pedal 21 is treaded downward first , the slot 79 enables the crankshaft 8 to rotate forward . the configuration is shown in fig1 a . at the top dead center , as the sliding rod 50 is pushed downward , the link 73 rotates and the corresponding new circle 72 has the smaller radius than the original circle 71 does . the circle 72 has two intersections with circle 81 . this configuration is similar to fig1 a that the crankshaft rotates counter - clockwise . the forward counter - clockwise rotation selective region is the small angle clamped by link 73 and the extension of link 80 . as shown in fig1 b , at the bottom dead center , there is only one selection of the clockwise rotation , too . as the rod 50 is pulled upward , the circle 71 has the link 75 to be the radius . the tip of link 75 is the intersection of circles 81 and 72 . at the bottom dead center , as the sliding rod 55 is pulled upward , the crank 80 rotates clockwise . the tips 73 and 74 are the two intersections of circles 81 and 71 . this reverse clockwise rotation selective region is clamped by the link positions 73 and 75 . the slot 79 is tiny so that the forward counter - clockwise rotation region and reverse clockwise rotation region are pretty small . in the continuous cranking motion , the crank 8 rotates and the link 7 swivels . the rotational momentum overcomes the tiny regions to have the continuous cranking rotation . it is noted that as long as the slot 79 is pretty small , the momemtum will enable the crank 7 and link 8 to rotate continuously in the original direction . unless the rider holds the sliding rod 51 still and starts over again , the direction selectivity will not play its role . the momentum will mask off the direction selectivity function . the crank mechanism will function as the normal cranking mechanism . there are two ways for the direction selectivity . the first way is dependent on the driving force applied to which side of the top dead center as shown in fig1 and fig1 . the second way is , at the top dead center or the bottom dead center , with the tiny slot 79 in fig3 a , the user can determine which direction the wheels will rotate as shown in fig1 a and fig1 b . however , the tiny slot 79 is optional . in fig3 a , the ball joint 44 is an integrated unit with the truck 41 and it fits in the hole inside the seat 111 . after steering , to have the wheels automatically line up to go straight forward , the axis of the truck 41 slightly tilts backward . the surface of supporting seat 111 slightly inclines forward . under the weight of the rider , the wheels 9 point forward automatically and the skateboard skates straight forward . as shown in fig5 c , the resilient bushing 48 is in the shape of parabolic curve . the difference in potential energy predisposes the wheels to point straight forward . as shown in fig5 d and fig5 e , comparing with the section views at different sections , the wheel will recover to straight forward position after steering . as the wheels point straight forward , the tilting angle between axis of the truck and the vertical line is the largest angle , the board is at the lowest position and it has the minimum potential energy . as the wheels point sideward and the axis of truck leans sideward , the angle between axis of the truck and the vertical line becomes smaller . the board will raise up a little and the potential energy is larger . the tilting effect of the board has a similar effect on steering and the return biasing . during the steering or tilting of the board , the axis of truck will tilt sideward . the angle between the axis of the truck and the vertical line becomes smaller . the board will raise up a little and the potential energy is larger . because of the potential energy in the gravity field , the energy is stored in the resilient bushing to return biasing . twisting the pedal 21 can steer the truck 41 and wheels 9 . the resilient bushing 48 is deformed as the truck turns . the resilient force in the resilient bushing 48 pushes the truck 41 back to the straight forward position . as shown in fig2 , it shows the mechanism of the steering . the vertical axis 56 correspondes to the axis of truck 41 . the horizontal axle 88 correspondes to the crankshaft 8 . if the truck axis 56 is vertical , the horizontal axis 88 can rotate 360 degrees as shown by the rotational disk 91 in fig2 a . if the truck axis 56 tilts backward with a small angle as shown in fig2 b , the corresponding rotational disk 92 tilts slightly backward and makes a tiny angle with the horizontal disk 91 . in fig2 c , the resilient bushing 489 is deformed and the energy is stored in the resilient bushing such as 489 in fig3 a , fig4 a and 471 , 472 in fig1 d . the resilient bushings 489 , 471 and 472 enwrap the truck tightly . there is a metal bushing 488 between the truck and the resilient bushing . the metal bushing 488 is integrated with the resilient bushing . the resilient bushing has the multiple functions of anti - shock , steering and recovering to the straight forward position . after the steering , the resilient bushing 489 will expand to push the truck axis 41 . the wheel 9 will point to the forward direction automatically and the skateboard will run straight forward again . there is a design trade - off among the inclination angle of the truck 41 , the deformation of resilient bushing 489 and the maximum steering angle . if the inclination angle of truck 41 is zero , the steering angle can be 360 degrees and the truck 41 is free to rotate ; the deformation of the resilient bushing 489 is zero . if the inclination angle of truck 41 is large , the truck 41 is difficult to rotate ; the turning angle is small . with a proper design trade - off of the inclination angle of the truck 41 and the deformations of the resilient bushing 489 , the restoring force of the resilient wheels 9 and bushing 489 will restore the truck 41 back to the straight forward position after steering . fig3 b is the partially exposed view of the wheel assembly having the exposed cross section of the engaging mechanism . to get rid of the friction in the engaging mechanism , the hub is filled with the grease . it is noted that the engaging mechanism is completely different from the conventional brake . in the conventional brake , the grease is not allowed at all . the wheel 9 has the engaging mechanism em bedded in the hub 19 . from fig1 to fig2 , the principles of the engaging mechanism are illustrated in the figures . fig1 is the basic operations of screw mechanism . in the following description , the rotational direction is described as the direction as seen from the right or looking into the paper . in fig1 , the axlewise gripping force 82 applies to hold the engaging drum 81 . in fig2 , the maximum value of the upper bounded gripping force is shown by the lines 94 and 95 . the gripping force is to grip the engaging drum 81 . seen from the right , as the right - hand screw 80 rotates counter - clockwise , the engaging drum 81 shifts left as shown in fig1 a . in fig1 b , as the screw 80 rotates clockwise , the engaging drum 81 shifts right . in fig1 c , the engaging drum 81 rotates clockwise relative to the screw 80 , the engaging drum 81 shifts left . in fig1 d , the engaging drum 81 rotates counter - clockwise relative to the screw 80 , the engaging drum 81 shifts right . from fig1 to fig2 , the basic operations of screw mechanism are further extended to be the operations of engaging drive to drive the wheel . in the following descriptions , the left - half wheel 83 is held not to move in the lateral direction . the screw is notched on the shaft 80 . as shown in the fig2 of schmitz &# 39 ; s patent , the spring clip finger portion 20 uses the radial friction force , the finger 20 is easily broken . in my invention , the gripping force uses the upper - bounded axlewise gripping force , not the friction force . the hub is filled with grease so that the friction is eliminated . the gripping spring 87 expands against the truck 86 and the engaging drum 81 to apply the upper - bounded axlewise gripping force to the engaging drum 81 . adapting to the shift of engaging drum 81 , the engaging spring 87 can adjust its length to apply the gripping force to the engaging drum 81 . the protrude 142 fits in the slot 422 that the upper - bounded gripping force is generated . furthermore , i make an innovation using a noncontact force . the noncontact force may be either electrical force or magnetic force . the poles of noncontact force generate the field to grip the engaging drum . as the engaging drum does in fig1 a , in fig1 a , as the engaging drum 81 shifts left , the engaging drum 81 squeezes the left - half wheel 83 and engages with the left - half wheel 83 . under the driving force of shaft 80 , the left - half wheel 83 rotates counter - clockwise . as shown in fig2 , during engagement , the wedge force 96 overcomes the gripping force 94 to drive the left - half wheel 83 . fig1 shows the engaging drum 81 disengaging with the left - half wheel 83 . there is a gap between the left - half wheel 83 and the engaging drum 81 . the wheel 83 is free to rotate . there are three ways to have the disengagement as shown in fig1 . in fig1 a , the left - half wheel 83 rotates counter - clockwise ; the shaft 80 is held still . at the beginning , the engaging drum 81 engages with the wheel 83 . as the left - half wheel 83 rotates counter - clockwise , the engaging drum 81 rotates together with left - half wheel 83 . according to fig1 d , the engaging drum 81 rotates and shifts right to disengage with the wheel 83 as shown in fig1 . the left - half wheel 83 is free to run . in fig1 b , the engaging drum 81 engages with the left - half wheel 83 . the left - half wheel 83 rotates counter - clockwise and the screw 80 rotates clockwise . as the left - half wheel 83 rotates counter - clockwise , according to fig1 d , the engaging drum 81 shifts right and disengages with the wheel as shown in fig1 . the left - half wheel 83 is free to run . in fig1 c , the left - half wheel 83 is still ; the engaging drum 81 is held by the gripping force 82 . at beginning , the engaging drum 81 engages with the left - half wheel 83 . as the screw 80 rotates clockwise , according to fig1 b , the engaging drum 81 shifts right and disengages with left - half wheel 83 as shown in fig1 . the left - half wheel 83 is free to run . fig2 is the conjugate case of fig1 for the right - half wheel ; fig2 is the conjugate case of fig1 ; fig2 is the conjugate case of fig1 . in fig2 , the right - half wheel 85 is held not to move in the lateral direction . as the engaging drum 81 shifts right , the engaging drum 81 squeezes the right - half wheel 85 and engages with the right - half wheel 85 to be one unit . as shown in fig2 , during engagement , the wedge force 97 overcomes the gripping force 95 to drive the wheel 83 to rotate . under the driving force of screw 80 , the right - half wheel 85 rotates together with the engaging drum 81 and the shaft 80 . fig2 shows the engaging drum 81 disengaging with the right - half wheel 85 . the right - half wheel 85 is free to rotate . there is a gap between the right - half wheel 85 and the engaging drum 81 . as shown in fig2 , there are three ways to have the disengagement . in fig2 a , the engaging drum 81 engages with the right - half wheel 85 ; the right - half wheel 85 rotates clockwise ; the screw 80 is held still . as the right - half wheel 85 rotates counterwise , according to fig1 c , the engaging drum 81 shifts right and disengages with the the right - half wheel 85 as shown in fig2 . the right - half wheel 85 is free to run . in fig2 b , the right - half wheel 85 rotates clockwise ; the engaging drum 81 engages with the right - half wheel 85 ; the screw 80 rotates counter - clockwise . as the right - half wheel 85 rotates clockwise , according to fig1 c , the engaging drum 81 shifts left and disengages with the right - half wheel 85 as shown in fig2 . the right - half wheel 85 is free to run . in fig2 c , the engaging drum 81 engages with the right - half wheel 85 ; the screw 80 rotates counter - clockwise -; the engaging drum 81 is held by the gripping force 82 . according to fig1 a , the engaging drum 81 shifts left and disengages with the right - half wheel 85 as shown in fig2 . the right - half wheel 85 is free to run . furthermore , as shown in fig2 , the left - half wheel 83 and right - half wheel 85 are merged to be one single wheel 84 . in fig1 , the wheel 83 is driven to rotate counter - clockwise ; in fig2 , the right - half wheel 85 is driven to rotate clockwise . in fig1 and fig2 , the left - half wheel 83 and right - half wheel 85 are free to run . so the combinatory wheel 84 is able to drive clockwise , counter - clockwise and free to run . these three basic operations can be used as the modes of forward drive , backward drive , free - run , speed - up , deceleration and brake . the gripping spring 87 in fig2 is equivalent to the gripping force 82 as shown in fig1 to fig2 . in fig2 a , the crankshaft 80 rotates counter - clockwise . the engaging drum 81 shifts left to engage with the combined wheel 84 at the left side of engaging drum 81 . the engaging drum 81 squeezes the wheel 84 and engages with the wheel 84 . as shown in fig2 , the engaging wedge force 96 overcomes the gripping force 94 applied on the engaging drum 81 . the crankshaft 80 drives the engaging drum 81 and wheel 84 to rotate counter - clockwise . in fig2 b , the wheel 84 rotates counter - clockwise . however , the crankshaft 80 is held still . as shown in fig2 , the wedge force 96 decreases with the clockwise rotation of wheel . as shown in fig1 a , the engaging drum 81 shifts left and disengages with the wheel 84 . finally , the frictional force 94 of spring 87 holds the engaging drum 81 still . the engaging drum 81 disengages with the wheel 84 . the wheel 84 is free to run . if the crankshaft 80 starts to rotate counter - clockwise , as shown in fig2 a , the wheel will be driven to rotate counter - clockwise again . this is the acceleration mode . in fig2 c , the crankshaft 80 rotates clockwise . the engaging drum 81 shifts right and engages with wheels 84 . the wheel 84 is locked with the engaging drum 81 . as shown in fig2 , the engaging wedge force 97 overcomes the gripping force 95 applied on the engaging drum 81 . the crankshaft 80 drives the engaging drum 81 and wheel 84 to rotate clockwise . to minimize the friction force , noncontact force is used . the noncontact force may be either electrical force or magnetic force . the design of the engaging mechanism of magnetic force is much simpler than the design of electrical force . in the following discussions , the word &# 34 ; noncontact &# 34 ; may be exchanged with the word of &# 34 ; magnetic &# 34 ; or &# 34 ; electrical &# 34 ;. as shown in fig2 , the noncontact poles 444 are buried in the frame of truck 411 and the noncontact poles 555 are buried in the engaging drum 800 . fig2 d shows one possible implementation of the noncontact gripping force engaging mechanism . the noncontact force is as shown in fig2 a . the &# 34 ; m &# 34 ; is the number of noncontact poles distributed on the peripheral . as shown in fig2 b , the noncontact force holds the engaging drum during the axle 80 rotating . as the engaging drum 800 engages with the hub 19 , the engaging wedge force overcomes the noncontact force to drive the wheel to rotate . the gripping force is very small . however , the mass of rider is large . the momentum of the rider will serve as the &# 34 ; fly wheel &# 34 ; to smooth the riding . this invention adopts the novel design of engaging mechanism such that it has a lot of novelties . fig2 shows the state diagram of the engaging mechanism . df is the state of driving forward as shown in fig2 a ; ff is the free - running mode as shown in fig2 b ; db is the driving backward mode as shown in fig2 c ; fb is the backward free - running mode as shown in fig2 d ; bf is the braking mode in the forward running as shown in fig2 a ; bb is the braking mode in the backward running as shown in fig2 b . at the beginning , as shown in fig2 c , the engaging drum 81 engages with the wheel 84 and is locked with the wheel 84 . as the wheel 84 rotates clockwise and the crankshaft 80 is held still as shown in fig2 d , the engaging drum 81 disengages with the wheel 84 . fig2 a is the mode of skating forward . fig2 c is the mode of skating backward . fig2 b is the free - running mode in forward skating . fig2 d is the free - running mode in backward running . with such a way of the cyclic operations of fig2 , the wheel 84 may be driven to skate forward , backward and free to run . with these three basic operations , the skateboard can have the modes of driving forward , driving backward , free running , deceleration and braking . the transition from fig2 a to fig2 a is the brake mode in forward skating . the crankshaft 80 is held still and t he engaging drum is self - locked with wheel . in the decelerate mode , the crankshaft 80 is allowed to rotate under the damping force of the feet . the transition from fig2 c to fig2 b shows the braking mode in the backward skating . the crank shaft 80 is held still . the engaging drum is self - locked with wheel . in the deceleration mode , the crankshaft 80 is still allowed to rotate under the damping force of the feet . in the deceleration mode and braking mode , the wheel 84 is self - locked with the engaging drum 81 and the shaft 80 . for this self - locked mechanism , the braking force comes from the self - locking force . in fig2 a , after the wheel 84 being braked to stop in backward skating , the wheel 84 may skate forward as shown in fig2 a . in fig2 b , after the wheel 84 being braked to stop in forward skating , the wheel 84 may skate backward as shown in fig2 c . in fig3 the above novel designs are applied to the wheel design . the axle of crankshaft 8 has shift screws 80 . the bevel bearing 18 and the locking nut 16 hold the wheels 9 to the crankshaft 8 . the shift screw 80 shifts the engaging drum 810 to engage or disengage with the hub 19 . the axle 8 is supported by bevel bearings 18 in the hub 19 . in the engaging position , the engaging drum 810 squeezes the hub 19 with the wedging force and is self - locked . as shown in fig7 the gripping spring expands to apply the gripping force . the gripper 14 has the protrude 142 and the frame 421 of the truck has the gripping slot 422 . fig8 shows the detailed design of the gripper 14 . the gripping spring 87 is hooked in the notch 141 . as the protrude 142 fits in the slot 422 , the engaging drum 811 is held by the gripping force of the gripping spring 87 . the gripping spring 87 holds the engaging drum 810 that the drum 810 can be shifted left and right as shown in fig2 and fig2 . from fig1 to fig2 , the working principles of the skateboard have been shown in the figures . referring to fig1 a , fig1 a and fig1 b , steping on the pedal may drive the crank 8 to rotate counter - clockwise to skate forward . referring to fig1 a , fig1 , fig2 a and fig2 , as the crankshaft 8 rotates counter - clockwise to drive the wheel 9 to rotate forward , the shift screw 80 shifts the engaging drum 810 until it engages with the hub 19 . in the engagement , the crankshaft 8 drives the wheel 9 to rotate . referring to fig1 a , fig1 , fig2 b and fig2 , the pedal 21 holds the crankshaft 8 still . the forward rotation of the wheel 9 releases the lock between the hub 19 and the engaging drum 810 . the wheel 9 rotates in the disengagement position . the skateboard is free to run without making any noise . there are two ways to initiate the clockwise rotation in the counter - clockwise rotation of forward driving . the first way is , as shown in fig1 a , in the half - way of stepping pedal 21 downward , raise up the pedal or release the pedal 21 . the pedal rod 51 is pulled up and the crank shaft 8 rotates clockwise as shown in fig1 b . the second way is : as the pedal moves up as shown in fig1 b , tread the pedal 21 downward as shown in fig1 a . the crankshaft 8 rotates clockwise . after the reversal clockwise rotation is initiated , due to the momentum of link 7 and crankshaft 8 , continuing stepping on the pedal 21 , the crankshaft 8 rotates in the direction of reverse clockwise rotation . as the crankshaft 8 rotates in the clockwise direction , as shown in fig2 c , the shift screw 80 shifts the engaging drum 81 to engage with the hub 19 . the wheel rotates to drive the skateboard backward . there are two ways to initiate the counter - clockwise rotation in the clockwise rotation of backward driving . the first way is , as shown in fig1 a , in the half - way of stepping downward motion , raise up the pedal or release the stepping pedal 21 . the pedal 21 is pulled upward and the crank shaft 8 rotates counter - clockwise as shown in fig1 b . the second way is : during the pedal moving upward as shown in fig1 b , tread the pedal downward as shown in fig1 a . the crankshaft 8 rotates counter - clockwise . after the counter - clockwise rotation is initiated , due to the momentum of link 7 and crankshaft 8 , continuing stepping on the pedal 21 , the crankshaft 8 rotates in the counter - clockwise rotation . as the crankshaft 8 rotates in the counter - clockwise direction , as shown in fig2 a , the shift screw 80 shifts the engaging drum 810 to engage with the hub 19 . the wheel rotates to drive the skateboard forward . as shown in fig2 and fig2 , the reverse rotation of crankshaft 80 may be used to brake the skateboard in the forward driving and vice versa . as the wheel 84 is in the forward rotation , the reverse rotation of the crankshaft 80 disengages the engaging drum 81 first as shown in fig2 b . as shown in fig3 the gripping force holds the engaging drum 810 . similar to fig2 a , in fig3 the rotation of the shift screw 80 shifts the engaging drum 810 to engage the hub 19 . the engaging drum 810 engages and locks the hub 19 . referring to fig2 , the wedging force 97 overcomes the gripping force 95 and drives the wheel 9 to rotate in the clockwise rotational direction . the clockwise rotation serves as the brake and the decelerating means for the skateboard . as the wheel 9 is in a backward clockwise rotation , the forward counter - clockwise rotation of the crankshaft 80 disengages the engaging drum 81 first as shown in fig2 d . as shown in fig3 the gripping force holds the engaging drum 810 . similar to fig2 b , in fig3 the counter - clockwise rotation of the shift screw 80 shifts the engaging drum 810 to engage with the hub 19 on the outer side of the engaging drum 810 . the engaging drum 810 engages and locks the hub 19 . referring to fig2 , the wedging force 96 overcomes the gripping force 94 and drives the wheel 9 to rotate in the counter - clockwise direction . as shown in fig3 a and fig5 the wheel assembly having the ball joint 44 can drive and turn direction simultaneously . twisting the sliding pedal rod 51 , the truck 41 swivels to turn direction . as the sliding pedal rod 51 slides upward and downward , the crankshaft 80 rotates to drive the wheels . as shown in fig4 a and fig6 the wheel assembly having the pivotal joint 43 can drive and turn direction simultaneously . turning the sliding rod 52 , the frame 42 swivels to turn right and left . as the sliding rod 52 slides upward and downward , the crankshaft 80 rotates clockwise and counter - clockwise . furthermore , the engaging mechanism enables the two wheels to be driven with different rotation speeds . it is the continuous undivided axle having the differential drive . during the turning direction , the inner wheel rotates slower than the outer wheel . the inner wheel still engages with the crankshaft 80 in the driving mode . the outer wheel runs faster than the rotational speed of inner wheel and the crankshaft 80 . the crankshaft 80 disengages the outer wheel . the outer wheel is in the free - running mode . so this wheel assembly is referred as the simultaneously steering and synchronous differential driving mechanism . fig4 shows the alternative design of the simultaneously steering and synchronous differential driving mechanism . in fig4 a , the truck 42 slightly inclines forward and the surface of supporting seat 112 slightly incline backward . under the weight of the rider , the wheel points backward to keep running straight forward . the pivotal joint 43 is a unit with the truck 42 . the flange 10 holds the resilient bushing 49 inside the seat 112 . on the link 7 , there is a pin hole . as the rear pedal 22 is treaded downward , the crankshaft 8 may rotate either backward or forward . in the forward running mode , the reversal rotation may serve as the brake mechanism ; in the backward running mode , the forward rotation may serve as the brake mechanism . to convert the axlewise engaging force to be the radially engaging force , the engaging drum 810 and the hub 19 adopt the wedges structure . furthermore , as shown in fig6 to make the assemble easier , the wedge blocks 812 are inserted to seal the engaging drum 811 inside the hub 19 . the hub is filled with grease ; the wedge block is not brake . the wedge block is to make the assembly work easier . as the crankshaft 8 rotates backward , the engaging drum 810 squeezes the wedge blocks 812 with the wedge force . the wedges 812 expand outward and engage with the hub 19 . the wheel will rotate backward . in fig4 c , the noncontact poles 444 use the noncontact gripping force to grip the engaging drum . the noncontact poles 444 are embedded in the frame 421 ; the noncontact poles 555 are embedded in the engaging drum 800 . the noncontact force grips the engaging drum 800 during the axle 810 rotating to drive the wheels . this skateboard is adaptable to operate in the field having rough road conditions . in this novel skateboard design , all the complex driving and steering mechanism is enveloped in the seats 111 and 112 ; all the complex engaging mechanism is enveloped in the hub 19 . looking from the outside , the mechanism is pretty simple . furthermore , the rider does not need to use the foot to push against the ground . the skateboard may ride in the snowy , icy or muddy road conditions . to ride in a rough road condition , the wheel of the skateboard adopts the groovy sprocket wheel 61 having the teeth 611 as shown in fig1 e , fig9 a and fig1 a . to ride the skateboard on the snow , the skateboard adopts the flexible belt 62 as shown in fig1 e , fig9 b , fig1 b and fig3 . referring to fig2 , the flexible belt 62 is composed of the flexible steel string 623 , polyurethane tube 622 , fingers 621 and the supporting shoes 624 and 625 . to enable the belt 62 to have the lateral flexibility , the tension supporting material is just a flexible string 623 which has the flexibility in all direction . the enveloping tube 622 for the string is divided into several small segments as shown in fig2 a . between the successive shoes , the fingers arc kept clear from each other . the supporting shoes 624 and 625 can slide over each other . so the flexible belt still keeps the lateral flexibility . the turning angle in steering is kept small . in steering , the variance of distance between the front and the rear wheels is small . the directional change of the belt is tiny . the changes of length and direction of belt are adjusted with the dangling sprocket gear 25 as shown in fig1 . the dangling sprocket gear 25 is mounted beneath the board 1 with the universal joint 249 . as shown in fig1 e , the bias spring 248 applies the pressure to the dangling sprocket gear to have the constant contact with the belt 62 . as shown in fig1 , the biasing spring 251 introduces the biasing force to the dangling sprocket gear 25 . as shown in fig8 as the skateboard moves left and the belt moves counter - clockwise . the upper belt moves left and pulls the right dangling sprocket 25 . the biasing force introduced by the biasing spring 251 enables the dangling level rotating downward . the dangling sprocket gear 25 squeezes the upper belt . the belt 62 is kept in tension . if the skateboard moves right and the belt moves clockwise , the upper belt moves right and pulls the left dangling sprocket 25 to squeeze with the upper belt . in such a way , the belt 62 is kept in tension , too . so the belts will enwrap the wheels in either forward or backward skating . while turning direction , the outer wheels pull the belt in both directions . the right and left dangling sprocket gears 25 are raised up to adjust for the larger pitch between two wheels . however , as the belt moves , one of the dangling sprocket gears will force the belt to be in tension . the belt 62 is in tension that the belt 62 enwraps on the wheels 61 . the flexibility of belt enables the belt 62 to adjust the small change of direction in steering . the universal joint 24 adjusts the change of the belt length and always keep the belt in tension . with the above design , the belts are kept to enwrap on the wheel 61 during steering . the fingers 621 , the shoes 624 and 625 support the weight of rider and increase the grasping force to the ground . to increase the smoothness in riding , as shown in fig1 a , the sprocket wheel adopts the alternating teeth pattern . as shown in fig1 b , the fingers of flexible belt have the alternating finger structure . although the description above contains many specificities , these should not be construed as limiting the scope of the invention but as merely providing illustrations of some of the presently preferred embodiments of this invention . thus the scope of the invention should be determined by the appended claims and their legal equivalent , rather than by the examples given .
the single - foot drivable skate and skateboard is constituted of the simultaneously steering - driving mechanism , synchronous differential driving mechanism , wheel and board . the simultaneously steering - driving mechanism comprises a universal pedal , the driving - steering rod and the single pole truck . the single pole truck pivotally supports the board with a pivot joint or ball joint . the driving - steering rod slides in the slot passing through the pivotal joint and the truck . the synchronous differential driving mechanism made of the noncontact gripping force or the upper - bounded gripping force includes the engaging drums shifted by the shift screws . the shift screws are knotched at the ends of the crankshaft axis . with the manipulation of a sole or heel , the skate or skateboard can twist the pedal to skate , tread the pedals to skate forward and backward , accelerate , decelerate , free - run , brake , turn right and left . to run on muddy and snowy roads , the non - stretchable length - adjustable belts are wrapped on the groovy sprocket wheels . the universal length - adjusting gears adjust the length of the belts and keep the tension in the belts .