WO2005105572A1

WO2005105572A1 - Dual-purpose sailboard

Info

Publication number: WO2005105572A1
Application number: PCT/HR2005/000016
Authority: WO
Inventors: Radovan Marin
Original assignee: Radovan Marin
Priority date: 2004-05-04
Filing date: 2005-02-17
Publication date: 2005-11-10
Also published as: HRP20040394A2; HRP20040394B1

Abstract

For water riding with a sailboard and a standard bicycle, a multiple-part mechanical assembly has been designed which can be easily attached to the sailboard and which serves to hold a bicycle with all elements retained except its front and rear wheels, and to effect transmission. In order to have the assembly attached, some simple adjustments should be made on the sailboard (drill holes of certain size and depth, insert plastic bushings into them and seal these with expanding foam), either at works where the sailboard is manufactured or subsequently. The Dual-purpose Sailboard, in addition to its original, sailing function, is given an extra function: riding on the board by using propeller or turbine drive and by means of a bicycle and a belt transmission unit.

Description

DUAL-PURPOSE SAILBOARD DESCRIPTION OF THE INVENTION Area of application According to the International Patent Classification (IPC) the present Invention can be assigned to the following classes: ❖ B 63 H 16/00 - Effecting propulsion by muscle power B 63 B 35/79 - Surf-boards, e.g. sailboards ❖ B 63 H 21/175 - the vessel being powered by land vehicle supported by vessel Technical task The technical task addressed by the Invention Is to design a mechanism which will combine a standard bicycle with a sailboard and enable the sailboard to move along by leg muscle power. The proffered design makes the sailboard and the bicycle a dual-purpose sport and recreational craft. The technical solution proposed by this Invention requires certain interventions on the sailboard, which, however, leave the basic use of the sailboard intact. State-of-the-art Of known designs of vessels propelled by muscle power the following documents are singled out here: 1. DE 4427591 Al, claimant Pal Zoltan, DE 2. FR 2535284, claimant Noel Fanelli, FR 3. FR 2487 291, claimant Robert Bravard, FR 4. DE 30 20873 Cl, claimant Michael Schwarz, DE 5. WO 90/07449, claimant Heinz Volkart, CH An analysis of the above documents shows that all of them offer solutions designed to make a vessel move by the pedalling action of the driver sitting on the "bicycle frame", i.e., by converting that action Into the circular movement of a propulsor (a revolving hub with radiating blades, or a propeller). Below is a brief comment on these solutions: ❖ The solution presented in DE 30 20873 Cl shows a pedal-propelled vessel. On tiie vessel is mounted a bicycle frame containing a pedal reduction gear mechanism by means of which the torque is transmitted to the propulsor (propeller). Weaknesses: ■ a great distance of the propulsor from the reduction gear (high torsion stress); ■ the pedal mechanism suggests that it is an unconventional bicycle; ■ fixing the front part requires removal of the front fork and fastening item (11) in its place. ❖ The solution presented in FR 2487 291 shows a floating structure (sailboard) on which by means of a belt (6) an assembly (3) is mounted containing among other things: a support (13) carrying the bicycle frame and supports (17, 18) bearing a shaft (15) on which there is a sprocket wheel (20) and hubs with blades (19). Weaknesses: « a clumsy and expensive structure; ^■ two "sailboards" (1 and 3); ■ two hubs with blades. ❖ The solution presented in FR 2535 284 shows a floating structure (1) containing a structure similar to a bicycle frame and belt transmission for moving the hubs with blades. The weakness is the newly provided structure of the "bicycle" frame and the pedalling mechanism. ❖ The solution presented in DE 44 27 591 Al shows a vessel (more versions of it) consisting of a sailboard (2), an attached structure (3), a bicycle frame (1), a stabiliser (4) and a propulsion mechanism shown in more versions. The torque from the pedal mechanism is chain- or friction-transmitted to the hubs with blades or by tooth-belt transmission to the propeller. Weaknesses: ■ in chain transmission: two chains: excessive length of the chains; transmission ratio unfavourable ■ in belt transmission: excessive length of the belt; the belt tends to overlap when the guides (32) move, because the belt pulley (33) i.e. the propeller (34) are turned by means of cables (20) The essence of the Invention The purpose of the Invention is to make a standard sailboard move on water by means of a standard bicycle. To accomplish this, a multiple-part mechanical assembly has been designed, which can be easily attached to a sailboard to hold a bicycle with all its elements, except for the front and rear wheels, and to enable transmission. For the assembly to be attached, some simple adjustments should be made on the sailboard (drill holes of certain size and depth, insert plastic bushings into them and seal these with expanding foam), either at works where the sailboard is manufactured or subsequently. Before undertaking a ride you have to mount the assembly (press it into the plastic bushings) and fasten the bicycle frame thereon. The installation work is easy and does not take more than 15 minutes, meaning that the use of the sailboard can be changed several times a day, depending on weather, your mood, or, generally, as needed. The assembly itself may be sold as a set for do-it-yourself installation. The sailboard is not losing its original function, it can be used as such irrespective of the above intervention. The standard sailboard is used for windsurfing, so on a windless weather it is totally useless. For using it on a nice peaceful day for recreation, the said (below described and illustrated) assembly can be mounted on the sailboard to hold any standard bicycle with only the wheels removed from it. This also makes the bicycle a dual-purpose sports implement without any remake. The same transmission mechanism can be mounted on any vessel of appropriate size which can be propelled by muscle power by means of a bicycle with one or two riders. Such a vessel can be used, except for sports and recreational purposes, to guard beaches, marinas, small lakes, boat docks, etc. For such end uses the vessel may be supplied with optional, easy-to-install aerodynamic lateral buoys to ensure its complete stability on water. On the front part of the sailboard there is enough room for a tool kit, a document box, etc. Needless to point out the ecological advantages of using such a vessel instead of a motorboat. Preparations for mounting the assembly are as simple as they can be. It can be installed at works or subsequently, if bought for an already available sailboard, as a do-it-yourself kit or a set for self-installation. A required number of holes of certain size and depth are drilled in the board for insertion of plastic bushings which are glued with expanding foam. The sailboard thus prepared is ready for sailing or bicycle riding. For bicycle riding preparations are simple and do not take more than 15 minutes. This means that the use of the sailboard can be changed several times a day, depending on weather, your mood, or as needed. Into plastic bushings already installed in the board the parts of the assembly are inserted as follows: the front support of the bicycle fork with the rudder pulley, the support of the rear bicycle fork with the sprocket wheel and the belt gear, the rudder cable guides, the rudder, the rudder cable with its tighteners and adjusters and, on the lower side, the transmission unit with the propeller, the gear wheel, the tooth belt and the belt tighteners. On a board thus prepared the

105 bicycle is mounted with all its elements except for the front and rear wheels and fastened to the assembly with the provided nuts on the front and rear fork supports. Sailboards are very stable on water and rather hard to overturn, especially in view of the fact that bicycle riding on the sailboard is practised only in fine weather on a calm water surface. However, to achieve even greater security, to avert a possibility of

110 the capsizing, a suitable buoy can be Velcro-fastened in the triangle of the bicycle frame to prevent overturning by more than 90 degrees. If the rider is not strong enough to lift the board out of the water from the lateral into the vertical position, a lever can be mounted on the board which in such an event the rider will insert into the sail bushing and thus lift the board out of the water into the vertical position.

115 In the selection of the bicycle for riding on the sailboard (unless already available) it is advisable to select one of higher quality class with aluminium frame, largely for the sake of lighter weight rather than the avoidance of corrosion, and with a front shock absorber. Riding on the sailboard with a bicycle like this will certainly be a nice and comfortable experience. Having this in mind, the sprocket wheel and gear shaft

120 is fastened to the support of the rear fork with reduction sleeves which allow the travel of the rear part of the bicycle frame during the action of the shock absorber. This bicycle-on-sailboard arrangement makes water riding much more enjoyable than ordinary recreational riding. On the support of the rear bicycle fork, along with the gear wheel of the transmission tooth belt, there is a 7-chain unit of the

125 rear bicycle wheel, to the effect that, by mounting the bicycle with its chain, front sprocket wheels and gear boxes, the propeller-pedal revolution ratio can be selected to suit one's own muscle power or fitness or desired speed. In other words, in terms of the choice of speed and physical strain on the rider, the potentials of the system are virtually limitless. Considering the fact that in quality bicycles the maximum ratio between the

130 front and rear gear is 5:1, in this mechanism 2:1 between the upper and lower belt gear, as well as the ability of a fit cyclist who turns pedals at the rate of 1% circle per second, at that moment the propeller makes 900 revolutions per minute. Furthermore, considering the fact that with that number of revolutions we are rotating a 220 mm diameter propeller with three blades and a bevel of about 35 degrees, you get a very

135 impressive speed picture indeed. But that's not ail for more ambitious riders. A number of modifications are feasible on the transmission with a view to increasing the speed: changing the existing chain assembly from seven to nine chains, increasing the ratio between the upper and lower gear from 2:1 to 2¹ - :1 or more, or installing a modified propeller with four blades and a larger blade bevel angle. With such modifications water

140 cycling has potentials of becoming a sports discipline. The tooth belt transmission of the revolutions of the rear shaft to the propeller shaft has helped to make the transmission system extremely easy. A change in the belt rotation axis by 90 degrees, i.e., from the transverse axis relative to the board to the longitudinal axis allowed to do away with the complicated, onerous, bulky and

145 expensive gear transmission system. The rear fork support, made of 5 mm steel, simple and very light, is fastened to the board with four 8 mm bolts into previously provided reinforced nuts. The support can be also manufactured from cast aluminium or similar light materials and fastened to the board with bolts for which nuts are made ready in INOX sleeves, i.e., inserted in the

150 board in the above described way. The third, most convenient design of the support is shown in one of the drawings. The support is made of a round section plastic, easily inserted into bushings prepared on the board. The right upper half of any of the three types of the supports is easy to disassemble to insert the chain. Otherwise the chain should be detachable, which is not the case with new generation bicycles. After

155 dismantling the assembly for bicycle riding on the sailboard, the opening in the middle of the board for the passage of the belt from the upper to lower side, as well as the boreholes with the built-in bushings, are closed by means of plugs provided for the purpose. The hub with the gear wheel and the shaft, fixed to the rear support, is made of plastic. The casing of the shaft and the chain assembly is made of aluminium, the

160 chain assembly itself of steel, as are the shafts and bearings. Metal is used only where absolutely necessary, which makes the mechanism so light. Fixed to the lower side of the board, under the support of the rear fork, is the transmission assembly, connected with the upper support through a round opening in the board by means of a tooth belt. This assembly is attached to the board also by

165 inserting into previously provided bushings. The mechanism consists of a plastic shaft with the belt gearwheel on it. The shaft rotates on two ball bearings protected by oil seals in the front and rear casings of the assembly. Both casings are filled with engine oil and protected by oil seals. Oil is discharged and refilled through openings topped by screws. The propeller is screwed onto the end of the shaft and secured by a counter-

170 nut. The transmission assembly can be modified by replacing the conventional bearings with ceramic or some other non-oxidising ones. In that case, the water in which the mechanism is submerged would serve as lubricant, whereby the oil seals would be eliminated together with resistance they cause to the propeller shaft. This transmission assembly is fastened to the board through two column

175 supports on which it is secured each by one central pin and two Allen screws on the sides. In their central part the column supports have a 6 mm hole for insertion of a rod of that diameter. By turning the central part of the column support, which on one side has a left-hand and on the other side a right-hand thread, the height of the transmission assembly and thereby the tightness of the tooth belt is adjusted. This mechanism, too, is

180 made of plastic and easy to disassemble, if, say, replacement of bearings or oil seals is required. Here, too, only essential parts are made of metal, viz.: two bearings, three INOX sleeves on the shaft under the oil seal, and the propeller. Inserted into the already glued bushing on the front part of the board is the support of the front fork of the bicycle. On the upper side of the support is the shaft on

185 which the front fork is tightened with the available nuts. Inserted on the lower side of the support is a cross joint which allows eccentric rotation of the front fork. Under the cross joint is the belt pulley fixed to the rudder cable. In the bushing inserted in the board for mounting the front fork support is the side pin. Provided on the lower part of the support, the one which is inserted into the bushing, is a circular duct with a 5 mm

190 wide slit. By inserting the support into the bushing and rotating it 180 degrees it becomes locked in the bushing and impossible to take out during the ride. The rudder is installed in the rear part of the board through the already glued bushings. The rudder is fastened to the board by putting the belt pulley for the cable on the upper part and the pin is secured into the rudder shaft

195 through the belt pulley. The rudder belt pulleys on the front support and the rudder are connected by a cable which passes through the guides on the central part of the board. On the front parts of the cable are inserted plastic screw tighteners of the cable, whereby also adjusted and corrected is the length of the left and right sides of the cable for co-ordination of the bicycle's handlebar and

200 the rudder. An obvious advantage of the described system is its simplicity and lightness, owing to the light plastic the bulk of it is made of. What is also important in addition to this is that all its rotary parts are rotating in bearings, which reduces the transmission resistance to a minimum. The whole assembly for mounting on the sailboard weighs 205 about 5 kg, with a possibility to further reduce the weight by about 1 kg by removing through drilling the unnecessary material in the middle of the round-shaped parts of the assembly. The made prototype of the sailboard with the mounted assembly weighs about 40 kg without a bicycle. In water the prototype loses some 3 kg. Namely, the 210 specific weight of the plastic material that the assembly is made of is less than that of water, so that the weight of the lower transmission unit is neutralised in water. Explanation of the attached drawings The master drawing of the prototype with a bicycle mounted on it and the plastic column support of the bicycle's rear fork is marked with number 1. The drawing 215 with the mounted metal support of the rear fork is marked la. Dwg. 2 shows the prototype without a bicycle with the plastic column support of the bicycle's rear fork. The drawing with the mounted metal support of the rear fork is marked 2a. The parts of the assembly in Dwg. 2a are marked with letters of the alphabet. Explications of the letter-marked details are marked with numbers. 220 The Dual-purpose Sailboard in the herein illustrated design is shown in detail on the attached drawings as follows: Dwg. A: - front support of the fork 1. Shaft with nuts on which the front support of the fork is fixed 2. Fork support column 225 3. Cross joint 4. Bolt for fixing the rudder cable belt pulley 5. Front pulley of the rudder cable 6. Front support bushing glued into the sailboard 7. Pin bolt for locking the fork support in the bushing 230 8. Pin duct for locking the fork support 9. Bushing bottom plug Dwg. B: - rear support of the fork with the gear wheel and the sprocket wheel 1. Nuts for tightening the bicycle's rear fork 2. Hub of the bicycle's rear wheel 235 3. Tooth belt gearwheel 4. Chain 5. Nuts with sleeves 6. INOX shaft 7. Ball bearings

240 8. Metal support of the bicycle's rear fork 9. Tooth belt 10. Detachable assembly for chain insertion Dwg. C: - the rudder's cable transmission unit 1. Front cable pulley 245 2. Rudder cable and tighteners 3. Cable guide 4. Rear cable pulley Dwg. D: - rudder 1. Pin bolt for fixing the rudder cable belt pulley

250 2. Rudder cable belt pulley 3. Upper bushing of the rudder fixed in the board 4. Rudder shaft 5. Lower bushing of the rudder fixed in the board 6. Rudder

255 Dwg. E:- F and G drawings combined Dwg. F: - lower transmission gear, front view 1. Frame for the cover key 2. Front bearing housing 3. Oil compartment

260 4. Hole for the column support pin 5. Ball bearing 6. Oil seal 7. Tooth belt guides 8. Tooth belt 265 9. Jacket 10. Propeller shaft 11. Front cover, threaded 12. Keyway for the cover key 13. Thread

270 14. Opening and bolt for oil discharge and refill 15, Shaft fastener 16. Retaining ring 17. INOX sleeve 18. Belt cogwheel

275 19. Opening for water discharge after using the board Dwg. G: - lower transmission gear, rear view 1. INOX sleeve 2. Oil compartment 3. Hole for the column support pin 280 4. Ball bearing 5. Distance between the bearings and the oil seal 6. INOX sleeve 7. Thread 8. Washer 285 9. Washer 10. Counter-nut 11. Propeller shaft 12. Jacket 13. Oil seal 290 14. Opening and bolt for oil discharge and refill 15. Oil seal 16. Rear bearing housing 17. Bearing and oil seal fastener, threaded 18. Shaft and bearing jacket 295 19. Propeller Dwg. H: - transmission gear column support (2 identical pieces) 1. Transmission gear 2. Upper part of the support with right-hand thread 3. Allen screws for fastening the gear 300 4. Support fixing pin 5. Belt tightener with right-hand and left-hand threads 6. Hole for inserting the belt tightening rod 7. Thread 8. Lower part of the support with left-hand thread 305 9. Support bushing glued into the board 10. Bushing bottom Dwg. HI: - version No. 2 of the belt tightener on the column support 1. Transmission gear 2. Transmission gear support 310 3. Nut 4. Hole for inserting the belt tightening rod 5. Lower part of the support, threaded 6. Support bushing glued into the board 7. Bushing bottom

315 Dwg. J: - alternative to the upper support of the bicycle's rear fork 1. Shaft with gear wheel and sprocket wheel 2. INOX sleeves with inside thread 3. Column supports 4. Gear lever travel opening 320 5. Bushings glued into the board Dwg. Jl: - detachable part, for inserting the bicycle chain, of the right-hand support of the bicycle's rear fork 1. Upper part of the column support 2. Nut 325 3. Thread 4. Lower part of the column support As shown in the attached drawings, the mechanical assembly, which requires protection, consists of more subassemblies, viz.: - front support of the bicycle fork with the rudder pulley ("A")

330 - support of the bicycle's rear fork with sprocket wheel and tooth belt pulley ("B") - rudder cable pulley and rudder ("D") - rudder cable with tighteners and rudder cable adjusters ("C") - transmission unit with the propeller, tooth belt pulley, tooth belt ("E") - column support of the transmission gear with belt tighteners ("H", "HI"), and 335 - column support of the bicycle's rear fork ("J" and Jl") Dwg. 3 shows subassembly "A", i.e., the front fork support mounted on the board. The front fork support contains a two-part column (2) which by means of the cross joint (3) makes a whole. On top of the column is a radially placed shaft with nuts (1) for fastening the bicycle's front fork. The lower part of the column is inserted into a plastic 340 bushing (6). By means of a guide duct (8) and by turning the support 180 degrees, the pin bolt (7) secures the support in the bushing. Above the bushing (6) is a pulley (5) fixed to the column with a screw (4). The turning of the bicycle handlebar makes the pulley (5) rotate, i.e., the rudder cable move. Dwg. 4 shows subassembly "B" attached to the board. The subassembly consists of

345 a shaft (6), a support (6), a detachable support (10), a nut for tightening the rear fork (1), a hub (2), bearings (7), gear wheel (3), a tooth belt (9), a sprocket wheel (4) and a nut with sleeves (5). Supports (8 and 10) are fastened by 8 mm screws to inserted threaded bushings, and into the board. The shaft is fastened with nuts - sleeves (5) to the supports (8 and 10) in which it slides round its axis when the bicycle frame is moved

350 up and down, caused by the action of the bicycle's front shock absorber. The gear wheel and the sprocket wheel are seated in the shaft by means of bearings and the two-part hub. The detachable support (10) enables the chain to connect with the sprocket wheel (4). Dwg. 5 shows subassembly "C", the steering system. The rudder cable (2) is placed

355 across and around the front pulley (1) and the rear pulley (4) and freely passes through the guide (3). The cable is firmly connected with the pulleys. The rear pulley is connected with the rudder shaft, the front pulley with the support column of the front fork. Dwg. 6 shows subassembly "D" attached to the board. The subassembly consists of

360 the rudder (6) with the shaft (4), the upper (3) and the lower (5) bushings, the pulley (2) and the screw (1). The shaft is inserted into the prepared bushings. The rudder is firmly mounted on the shaft, whereas the pulley is fixed to the shaft by the screw (1). Dwg. 7 shows the lower transmission subassembly "E", combined drawing No. 8 "F" and drawing No. 9 "G". The lower transmission subassembly is attached to the board by

365 supports and bushings, and connected to the upper support through the opening in the board with the tooth belt. As seen on drawings No. 8 "F" and No. 9 "G", the shaft (lOoll) is seated in the casing by means of the bearings (5<>4) and linked to the gear wheel (18) and the propeller (19). The housing is so designed that the bearings are placed in sealing chambers, protected by gaskets (6, 13, 15), filled with oil and mutually

370 connected by a plastic jacket (9<>12). The gaskets rest on the INOX sleeves (17, 1, 6) which are pressed onto the shaft. Oil is discharged and refilled through openings topped by screws (14). The propeller is screwed onto the end of the shaft and secured by a counter-nut. The transmission gear can be modified by replacing the conventional bearings with ceramic or some other non-oxidising ones. In that case, the water in 375 which the mechanism is submerged would serve as lubricant, and the oil seals would be eliminated together with resistance they cause to the shaft. The transmission gear is attached to the board via two column supports, drawing No. 10, subassembly "H", on which it is secured each by one central pin and two Allen screws on the side. In their central part the column supports have a 6 mm borehole for 380 insertion of a rod of that diameter. By turning the central part of the column support, which on one side has a left-hand and on the other side a right-hand thread, the height of the transmission assembly and thereby the tightness of the tooth belt are adjusted. Drawing No. 11 shows subassembly "HI", which has the same function as subassembly "H", except that the adjusting nut (3) for belt tightening is accommodated 385 under the support, so the belt tightness adjustment is done by unscrewing or screwing of the nut along the notched part of the support (5). In lifting the support by unscrewing the nut the sliding part of the support in the bushing (7) will keep the subassembly compact. Drawing No. 12 shows subassembly "J", the alternative design of the rear support of 390 the bicycle fork. This support has the same function as the metal support shown in drawing "B", except that it is made of plastic and more attractive, as well as easier to insert into the bushings previously glued into the board. Drawing No. 13, marked "Jl", shows the detachable right-hand support from drawing "J" for inserting the bicycle chain. Quick disassembly/ reassembly is made 395 possible by unscrewing the nut (2) from the notched part of the support column. Conclusion The advantages of the described and illustrated designs compared with similar ones: - possibility of dual-purpose use of the surfboard: windsurfing and water cycling - very fast changing of the use of the board

400 - possibility of purchasing a set for mounting on the already available board - use of an already available bicycle of any size - minimum weight of the whole assembly - simple design dispensing with a structure for seats, pedals, etc. - easy and cheap to manufacture

405 - possibility of adapting the transmission system for sports competition - elimination of Cardan and similar shafts, as well as conical or transverse gear wheels, plus attractive design.

Claims

PATENT CLAIMS

1. The Dual-purpose Sailboard propelled by muscle power is characterised in that a multiple-part mechanical assembly is mounted on a standard sailboard to hold a standard bicycle without its front and rear wheels, whereby power transmission is effected from the pedals to the propeller.

2. The Dual-purpose Sailboard, according to claim 1, is characterised in that the multiple-part assembly, detachable, is attached to the sailboard by means of bushings inserted into holes on the board and joined to the board.

3. The Dual-purpose Sailboard, according to claims 1 and 2, is characterised in that the multiple-part assembly consists of: - column support (A) of the bicycle's front fork with a cross or ball joint - rear fork support (B) with the upper transmission subassembly - transmission mechanism for rudder steering by means of a cable - rudder (D) with a pulley - lower transmission subassembly (E) - column supports (H) and (HI) of the lower transmission subassembly - rear column support of the fork (J) and (Jl)

4. The Dual-purpose Sailboard, according to claims 1, 2 and 3, is characterised in that the column support (A) of the front fork consists of upper and lower parts interconnected by a cross joint (3), with the upper part of the support containing a shaft with nuts (1) for fastening the bicycle's front fork, the lower part containing the belt pulley (5) which is fixed to the support with a screw (4), plus safety stops to prevent the assembly from coming out of the bushing during the ride (7) and (8).

5. The Dual-purpose Sailboard, according to claims 1, 2 and 3, is characterised in that the rear two-column fork support (B) and (J, Jl) consists of a left-hand support (8) and a detachable right-hand support (10), to which the shaft (6) is attached by sleeves-nuts (5), carrying the seated two-part hub (2) to which the gear wheel (3) is fastened, with the sprocket wheel (4) coupled to it.

6. The Dual-purpose Sailboard, according to claims 1, 2 and 3, is characterised in that the transmission unit for rudder steering by means of the cable (C) is mounted on the upper surface of the board, consisting of a front pulley (1), a rear pulley (4), a guide (3) and a cable tightener (2).

7. The Dual-purpose Sailboard, according to claims 1, 2 and 3, is characterised in that the rudder (6) is connected to the shaft (4) which passes through bushings (3 and 5) and the board and to which it is attached by the belt pulley (2) of the cable.

8. The Dual-purpose Sailboard, according to claims 1, 2 and 3, is characterised in that the lower transmission subassembly (E) is attached to the board with supports and bushings and connected to the upper support with a tooth belt of adjustable tightness, which changes the rotation axis and passes through the opening in the board.

9. The Dual-purpose Sailboard, according to claims 1, 2, 3 and 8, is characterised in that the transmission subassembly (E), shown in drawings (F, G)), consists of: - front cover (11) with thread (13) and notches for the key (1, 12) - oil chamber (3) - bolt for oil discharge and refill (14) - housings of front bearings (2) with a hole for the column support pin (4) and an opening for oil discharge and refill (14) - bearing (5) - gasket (6) - tooth belt guides (7) - tooth belt (8) - belt gear wheel (18) - jacket (9) with a water discharge opening (19) - shaft (10) - shaft base plate on the bearing (15) - retaining ring (16) - INOX sleeve under the gasket (17) (see drawing F) - propeller (19) - washers (8, 9) and threaded cover (10) - jacket for fixing the shaft and the bearing (18) - rear bearing housing (16) with a hole for the column support pin (3) and an opening for oil discharge and refill (14) - bearing and gasket fastener (17) - sleeves (17, 1, 6) - distance ring (5) between the bearing and the gasket - retaining ring (16) - fastener (15) of the bearing onto the shaft (see drawing G)

10. The Dual-purpose Sailboard, according to claims 1, 2, 3 and 8, is characterised in that the transmission subassembly (E) is fastened by screws (3) to the column supports (H), which are height-adjustable for belt tightening.

11. The Dual-purpose Sailboard, according to claims 1, 2, 3, 8 and 10, is characterised in that the column support (H) consists of the upper part (2), the lower part (8) and the belt tightener (5) which connects the upper and lower parts into a whole by a screw fastening, with the upper part of the support (2) containing the right-hand thread and a positioning bore; the lower part (8) contains the left-hand thread, whereas the belt tightener contains the right-hand and left-hand threads and a hole to insert the belt tightening rod.

12. The Dual-purpose Sailboard, according to claims 1, 2, 3, 8 and 10, is characterised in that the column support (HI) consists of the upper part (2), the lower part (8) and the nut (3) which connects them into a whole and with which the column support height and thereby the belt tightness are adjusted.

13. The Dual-purpose Sailboard, according to claims 1, 2, 3 and 5, is characterised in that the upper support (J) of the bicycle's rear fork consists of two column supports (3) which at the top have boreholes made into which bushes (2) with the inside thread are inserted, with the right-hand support also having an opening (4) for the travel of the gear lever.

14. The Dual-purpose Sailboard, according to claims 1, 2, 3 and 5, is characterised in that the upper right-hand support (Jl) of the bicycle's rear fork consists of two parts connected by a nut (2), with the upper part (1) containing the nut (2) and having a protrusion for alignment, the lower part (4) having the outside thread and a recess for positioning.