Patent GB-1436267-A (GB)
Title: Snowmobile conversion kit for motorcycles
IPC: B62M27/02
Filed: 1973-07-20
Abstract: 1436267 Converting motorcycles to snowmobiles ADVANCED RECREATIONAL EQUIPMENT CORP 20 July 1973 [21 July 1972] 34838/73 Headings B7B and B7H A motorcycle may be converted into a snowmobile by attaching the motorcycle frame to a mounting beam pivotally supported on a frame of an endless track assembly and mounting a ski on the forks of the motor cycle. A power train connected from the power unit of the motorcycle drives the endless track assembly. As shown in Fig. 3 twin endless tracks 41 are mounted on a track frame 22. Sprocket pairs 46 keyed for rotation with shaft 47 at the front end of the frame are journalled on a pair of bearing plates 48 pivotally mounted on a sleeve 51 adapted to slip over the extreme end 37 of the rail portions 23<SP>1</SP>, 24<SP>1</SP> of the track frame. The plates 47 are resiliently biased about a pivot pin 49-by a spring 52. Rear sprocket pairs 46 are fixed for rotation with shaft 53 journalled on stringers 23, 24 the shaft having a drive sprocket 56, Fig. 5, rotation of which is achieved via a chain linked with a sprocket 57 of an auxiliary drive shaft 58 journalled in a bearing bracket 59 on the track frame. Auxiliary drive shaft 58 is connected to a stub shaft 63 of a drive housing 64 via a constant velocity universal joint 61, 62 thus allowing pivoting of the housing 64 on the track frame. Aperture 66 in housing 64 allows passage of drive chain 67 which interengages drive sprocket 8 on the motor 7, idler sprocket 68 on the bracket 69 being fixed on a pivotally mounted bike mounting beam 71 and drive sprocket 77 being mounted on stub shaft 63. The beam 71 supporting bike frame is pivoted at its front end to the track frame by a pivot pin 82 and at its aft end a flange 83 is bolted to the housing 64 which in turn is pivotally mounted on the bearing bracket 59 by a pivot pin 87. Pivoted mounting links 92, 93, Fig. 14, allow fore and aft motion of the bike frame relative to beam 71 to accommodate drive chain adjustment. A cranked torsion bar 106, Fig. 4, interconnecting the beam 71 with an anchor plate 109 of cross beam 29 biases the bike frame into an upright position. Alternatively, as seen in Fig. 14, a flat torsion bar 116 has one end seated in a socket in a bearing sleeve 118 welded to the track frame which sleeve 118 also serves as a journal for beam 71. The opposite end of bar 116 is secured in close proximity to pivot pin 87. The effective length of bar 116 may be adjusted by a clamp device 121 which slidably receives the bar 116 and which is adjustably secured to the mounting beam 71. A lever arm 127, Fig. 7, provided on the beam 71 has apertures 128 for selective engagement by one end of a shock absorber 129 anchored to the track frame, the absorber 129 serving to damp further pivotal movement of the bike frame. A track bolt 131 engaged in cross beam 38, Fig. 6, is adjustable and engages sleeve 51 to longitudinally adjust shaft 47 carrying sprockets 46 for keeping the track belts taut. For the same purpose a track runner 136 is provided extending parallel to the lower reach of each of the tracks and mounted on the ends of the cross members 31, 32. Wheels 143 journalled on the extreme ends of runners 136 engage the inner surface of the tracks and also function as a rolling support for the apparatus if the tracks are removed. A brake disc 146, Fig. 5, is keyed to shaft 63 and is engageable by a brake caliper 147. A fibre glass fairing 151 may be supported on stringers 23, 24. For steering purposes a fork extender 161, Fig. 2, received in a clamp bracket secured to the vehicle forks, is pivotally connected at its lower end to flanges on a ski 164. The bottom surface of the ski has skeds 168 to prevent skidding.