GB1356952A - Braking and stability of vehicles - Google Patents

Abstract

1356952 Aerodynamic brakes for road vehicles D E TURNER 1 March 1972 [18 Dec 1970] 60107/70 Heading F2E A motor cycle has left- and right-handed flaps of aerofoil section disposed one at either side of it, each flap being hinged at its leading edge and the hinge axes being in planes parallel to and equidistant from the symmetry plane of the motor cycle, the flaps presenting minimum aerodynamic disturbance when in passive angular positions and being rotatable to effect progressively-increasing aerodynamic resistance to the motion of the motor cycle but so as to maintain substantially equal aerodynamic moments, maximum profile area being presented at fullyopen position; the aerodynamic resistance of each flap is further increased by progressive closure of holes in it by a slidable shutter plate whose position is related to the angular position of the flap, the variations in the nett area of the flap effected by the shutter being significant at and near the flap-fully-open position. As shown at 1A, Fig. 1, the flaps may be disposed at the rear of a motor cycle. Each flap is of aerofoil section, Figs. 3, 5, and has a number of holes 8 to 12, Fig. 2. A shutter plate 14 with identical holes is retained by strips 28, 29 in a shallow recess in the rear face of the flap, Fig. 3, and is raised automatically, on outward swing- ing of the flap, by mechanism described below, from the position of Fig. 2 to a position where the holes in the flap are completely closed by the regions, between holes, of the shutter plate. The flap is hinged at 2, Fig. 1, to the motor cycle frame behind the pillion seat by bracket 32 and hinge pin 33, Fig. 3, and at 3, Fig. 1, indirectly to the pillion footrest by hinge pin 25, Fig. 5, on elbow piece 40 pivotable about the footrest axis to facilitate assembly. The two flaps on either side are pivoted into operative position (i.e., transverse to the direction of motion of the motor cycle) by a doubleacting jack 35, Fig. 3, under the control of the driver. The jack is itself movable, relative to its bracket 32, by oblique or cross-winds acting on the flaps, so that after initial pivoting of the flaps their angular settings may be rendered unequal, whereby aerodynamic equilibrium in the direction of motion is established. During rotation of a flap from its inoperative position, the shutter 14 is raised against the tension of an anchoring spring 17, Fig. 2, by movement of the flap relative to a cable 19, Figs. 2 and 5, anchored at one end 42 to a bracket 24, Fig. 5, mounted on the pillion footrest, and at the other end 20, Fig. 2, to the top of the shutter. The cable is encased in a portion of sheath 43, Fig. 5, which is universally jointed at 23 with a further portion 21, Fig. 2, located inpart in a groove 22 in the flap. The geometry of the arrangement (especially the location of universal joint 23) is such that during the first 45 degrees (approximately) of flap movement, the shutter is moved through only a small proportion of its distance, and during the remaining flap movement, shutter movement is completed (Fig. 6, not shown). The inclination to the vertical of the hinge axes of flaps 1A, Fig. 1, has the consequence that, in use, flap pressure will oppose the effect of weight-transfer (from rear to front wheels) on normal braking and increase rear-wheel braking. Alternatively the flaps may be located ad. jacent the front, 5A, 5B, Fig. 1.