GB2388828A - Start hook for motorcycle racing - Google Patents

Abstract

A hook 302 is located on an upper front fork 107 of a competitive racing motorcycle and is engageable with a slot 202 in a guard 109 positioned adjacent to the front forks. The hook 302 is engaged to retain front wheel suspension in a compressed state for aiding a rider in starting, subsequent shocks releasing the hook to enable normal suspension action to occur. The hook is mounted on a two part collar for fixing around the upper front fork 107 at a lower widened end. The hook may be manufactured by a process of injection moulding in a plastics material.

Description

Start hook for motorcycle racing The present invention relates to a hook

for use on the front forks of a competitive racing motorcycle, configured to engage within a guard positioned adjacent to said front forks, where an effect of said engagement is to enable said motorcycle to gain the most rapid possible start.

The sport of motocross has grown in popularity in recent years. This activity involves the competitive racing of motorcycles on dirt track road, cross-country courses and the like, and riders are constantly seeking to find ways of deriving superior performance from their machines. In competition, riders leave the start line in a pack and have found from experience that whichever of them is able to reach the first corner, or turn, is well placed to win the race. Achieving this is termed in the sport as "getting the hole shot". As a consequence riders try to achieve the fastest possible start. If a rider does not make a good start he will find himself caught in the melee of other riders, or "mid-

pack" as this is described in the sport. A rider in "mid-pack" is more aware of the other riders around him and has to back off the throttle and reduce speed in the event of any problems, rather than being free to concentrate exclusively on winning the race. Besides the loss of competitive advantage being caught mid-pack is also dangerous, since collisions between the riders are common.

For a competing motocross rider therefore making the first turn, or "getting the hole shot", is a crucial objective, and often the most significant of the entire race. When a rider accelerates rapidly away from the start line towards the first turn, however, he faces two risks. Because a motorcycle is driven from the rear wheel and is relatively light in overall weight there is a danger of the front wheel ilfting off the ground. This is known in the sport as "doing a wheelie" and is highly undesirable. The second danger is loss of traction and an impaired degree of control over the motorcycle.

( At the present time the only way a rider wishing to make a quick start can try to minimise these problems is by varying his sitting position on the motorcycle. To prevent the front end coming up he has to sit as far forward as physically possible. However, because the rider's weight is on the front end rather than over the rear wheel, traction with the ground is reduced leading to poor starts.

In order for a rider to achieve more traction he must sit further back so that more of his weight is distributed over the rear wheel. This, however, can produce "wheeling" due to the aforementioned tendency of the front end to lift up at high rates of acceleration.

To "get the hole shot" a rider requires a range of factors to be in his favour at the critical moment. His body position is important, particularly his seat position, lean of the body and back movement. The controls of the motorcycle must be correct. The rider's right hand is on the throttle at the right point, over gripping the accelerator. At the same time his left hand has complete control of the clutch, whereby the clutch is let out slightly until its is near to disengagement. The starter official displays a notice to the riders advising that the race is to start in five seconds; this is known as the "five second board".

Once a rider has seen this he looks at the start gate or pin; as soon as these move he releases his clutch and opens the throttle.

According to a first aspect of the present invention, there is provided a hook for use on the front forks of a competitive racing motorcycle, configured to engage within a hole located in a guard adjacent to the front forks, with the object of enabling said motorcycle to gain the fastest possible start.

According to a second aspect of the present invention, there is provided a hook for use on the front forks of a competitive racing motorcycle, where said hook can be readily fastened to and unfastened from the front forks.

( The invention will now be described by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows riders in a competing in a motocross race leaving the start line; Figure 2 shows the front wheel, forks and fork guards of a motorcycle competing in a motocross race; Figure 3 shows the forks seen in figure 2 onto which a hook has been attached; Figure 4 shows the forks seen in Figure 3 onto which a hook has been attached, where said hook is engaged in a hole provided in one of said guards; Figure 5 shows a section through the hook assembly seen in Figure 4; Figure 6 shows a section through the hook assembly showing the means of fastening onto said forks; Figure 7 shows the completed hook assembly; Figure 8 is an exploded view showing the components which make up said hook assembly; and Figure 9 is an exploded view of a second embodiment showing the components which make up said hook assembly.

The start of a motocross race is shown in figure 1 with riders and motorcycles 101, 102, 103 and 104 accelerating away from the start line 105. On motorcycle 101 can be seen the front wheel 106 and front forks 107 and 108 together with front fork guards 109 and 110. In addition to exhaust fumes, clouds of dust 111 are produced by rear wheels 112 spinning as a result of poor traction. All the riders 101, 102, 103 and 104 wish to be first to reach the first turn on the track and thereby try to assume control of the race.

Figure 2 shows part of the front end of a motorcycle 101 competing in the event shown in Figure 1. The front wheel 106 is located between the front forks 107 and 108 and attached to said front forks 107 and 108 are front fork guards 109 and 110. Fastened to front fork 107 is a hook 201 configured to engage within a hole 202 in the adjacent front fork guard 109, with the object of enabling said motorcycle 101 to gain the fastest possible start. The hook 201 is positioned at the bottom end of the front fork 107, said bottom end typically having a somewhat enlarged diameter with a flared or swaged profile 203.

Figure 3 shows a side view of the hook assembly seen in Figure 2. Lower fork member 301 is housed within upper fork member 107. When the motorcycle 101 is being ridden axial movement of said lower fork member 301 within upper fork member 107 is regulated by the suspension system of the motorcycle 101. The purpose of said regulated axial movement is to absorb the impact of any shocks caused to the motorcycle 101 by riding over bumps, holes and the like.

Because the outer diameter of lower fork shaft 301 is a lubricated bearing surface it is prone to damage caused by stones, dirt and the like. For this reason it is common to fit shielding means adjacent to said lower fork shaft 301 in order to provide some protection for said shaft. In the present embodiment, therefore, a front fork guard 109 has been attached at the bottom end of said lower fork member 301 which prevents said stones, dirt

( and the like flying up from the track surface in front and hitting said shaft. Typically, a front fork guard 109 is manufactured by injection moulding in a plastics material, usually polypropylene because said material is practically unbreakable. A hook 201 is attached to the bottom end 203 of the upper member of the front fork 107, said bottom end typically having a somewhat enlarged diameter with a flared or swaged profile 203. Said hook 201 is fastened securely to said diameter 203 such that said hook 201 cannot slip off.

Projecting forwards from said hook 201 is an engagement tooth 302. The front fork guard 109 is further provided with a hole 202.

Figure 4 shows the assembly described in Figure 3 when the motorcycle 101 has been prepared for a competitive motocross event. The front end of the motorcycle 101 has been pushed down so that lower front fork member 301 is pushed into the upper front fork member 107 by the distance indicated by arrow 401. The bottom end 203 of the upper member of the front fork 107 is therefore displaced from its former position as indicated by broken line 402 to its new position as indicated by line 403. In a preferred embodiment the distance indicated by arrow 401 is around three and a half inches. When the full amount of travel as indicated by arrow 401 is reached the engagement tooth 302 on the hook 201 aligns with the hole 303. Said tooth 302 is then engaged within hole 303, thereby securing front fork 107 and fork guard 109 together. Said engagement is facilitated by a partial flexing outwards of said fork guard 109 in the direction of arrow 404 to allow said engagement tooth 302 to clear the inside surface of said fork guard 109 and lock into the hole 202. Said flexing is made possible by the fact that said fork guard 109 is manufactured in a flexible plastics material such as polypropylene.

An effect of said exercise is that the front end of the motorcycle 101 is being held down, and the effects of the front suspension are greatly reduced. A further effect of said

( exercise is that the centre of gravity of said motorcycle 101 is shifted forwards towards the front wheel. An advantage of said effects is that the front end of said motorcycle is far less likely then before to lift up under large forces of acceleration. A further and related advantage of said effects is that, as a consequence, the rider can sit further back providing more weight distribution over the rear wheel, said sitting position producing much better traction than would otherwise be possible.

Figure shows the assembly described in Figure 4 as an elevation section through its centre. The hook 201 is fastened around the bottom end 203 of the upper member of the front fork 107, and the engagement tooth 302 on the hook 201 is locked into the hole 202 in the fork guard 109.

It is important that the engagement of the hook 201 with the fork guard 109 is temporary.

It should be noted that, were said engagement to be permanent, the consequences would be catastrophic for both rider and motorcycle. This is because said motorcycle would no longer be protected from the effects of riding over rough surfaces, and as a result the front forks 107 would be damaged with the rider unseated and probably badly injured, perhaps fatally. The engagement tooth 302 on the hook 201 therefore has a height not exceeding that of the hole 202. When the motorcycle 101 hits the first bump on the track surface the lower fork member 301 is momentarily pushed even further up inside the upper fork member 107. This action causes the top of engagement tooth 302 as indicated by the line 501 to be displaced in the direction of arrow 502 down the outside of the fork guard 109 until it reaches the top of the hole 202 as indicated by the line 503. Said fork guard 109 then springs back in the direction of arrow 504 and comes to rest at a position indicated by the line 505. The upper fork member 107 complete with the hook 201 is then free to travel in the direction of arrow 506 back up to its usual position.

( Figure 6 shows the assembly described in Figure 5 as a plan section through its centre. The hook 201 substantially consists of two halves 601 and 602 which close together around the shank of the upper fork end 107. A major advantage of said two piece construction is that the hook 201 can be readily fitted without the need to take the front of the motorcycle 101 apart, as would be the case with a single ring type of component. Said advantage saves both riders and mechanics a large amount of time and trouble before an event, which is when they are keenest to concentrate on the race itself.

The two halves or shells, 601 and 602, which make up the hook 201 are injection mouided in a plastics material. In a preferred embodiment, said plastics material is acetal.

This is a very tough polymer which possesses the high impact strength required by the application. The preferred grade of acetal is designated acetal-F20-03 reinforced.

Although the hook 201 could be manufactured as an aluminium casting, for example, plastics is preferred owing to its lower cost. A pivot 603 is provided in the form of a hinge barrel 604 on shell 601 over which cooperating cradle 605 on shell 602 rotates towards its closed position in the direction of arrow 606, from an open position as indicated by broken line 610. A nut 607 is provided in shell 601 which co-operates with a bolt 608 located in shell 602 to fasten the two said shells 601 and 602 together.

When the two said shells 601 and 602 are rotated from an open position towards a closed position it is helpful during assembly of the hook 201 to partially engage the bolt 608 in the nut 607 before the said shells 601 and 602 are completely fastened home. An amount of additional clearance is therefore provided as indicated by arrows 609 in the recess within shell 602 provided for said bolt 608 to allow the required displacement.

Figure 7 shows the hook 201 assembled around the bottom end of the upper member of the front fork 107. The pivot assembly 603 is viewed from underneath to reveal the moulding details of the hinge barrel 604 and the co-operating cradle 605. When shells 601 and 602 are open said cooperating cradle 6Q5 can be disengaged from said hinge barrel 604. Once said shells 601 and 602 begin to close then said hinge barrel 604 is linked to said co-operating cradle 605 such that the shells cannot come apart. Said linkage is of great assistance in fitting of the hook 201 to the front fork 107 since attempting to secure two floating shells would be more difficult and time-consuming.

Grooves 701 are provided on the internal diameter of the two shells. Said grooves have two primary functions and advantages. A first advantage is that the overall thickness of wall section for the shells 601 and 602 is increased from simply one wall thickness of plastic to one having a more castellated profile, thus creating a much stronger section. It should be noted that it is not good practice in the field of injection moulding to try to

produce solid sections of undue thickness, since this creates a number of serious problems including sinking, difficulties with removal from the mould, difficulties relating to the flow of material in the mould, excessive cost and so forth. in a preferred embodiment the standard moulded wall thickness is 2 millimetres. The incorporation of said castellated profile therefore enables the overall thickness of wall section for the shells 601 and 602 to be increased to 5 millimetres. With the incorporation of an interchangeable insert in the tooling said internal diameter can be reduced so that said hook 201 will fit around correspondingly smaller diameters of front forks.

A second first advantage of said grooves 701 is that these provide an enhanced degree of grip on the shank of the fork member 107.

The bolt assembly 608 is located opposite said pivot assembly 603, and the engagement tooth 302 projects from shell 602. Forty five degree chamfers 702 are provided on the tip the engagement tooth 302 in order to assist the passage of said tooth

( 302 into the hole 202 in the fork guard 109. In a preferred embodiment said tooth 302 has a height of around seven millimetres. A rib 703 extends downwards from said tooth 302 at an angle of 45 degrees in order to provide additional strength.

A recess 704 is provided on the outer diameters of both shells 601 and 602 in order to allow the fitting of tapes bearing printed logos, designs and the like.

Figure 8 is an exploded view of the hook 201 assembled around the bottom end of the upper member of the front fork 107. The whole of the pivot assembly 603 can now be seen, where the substantially cylindrical hinge barrel 604 is provided with chamfers 801 where it meets the adjacent wall. Corresponding chamfers 802 are provided in the co-

operating cradle 605. The nut 607 and the bolt 608 are manufactured from either hardened steel or anodised aluminium. The bolt 608 is of the caphead type accessed by an alien key and the nut 607 is of the shakeproof "Nylock"m type. Said nut is provided with a thread cut into the metal and also a plastic, typically nylon, sleeve 803 adjacent to said thread. When the threaded shank 804 of said bolt 608 is engaged into said nut 607 said thread cuts into the nylon sleeve 803 and provides a vibration-resistant fit. This is important since the hook 201 must not become detached during a race and create a hazard. In a preferred embodiment the nut 607 and bolt 608 are sized at M5. The nut 607 and the bolt 608 assembly on the hook 201 is strengthened by the provision of buttressing ribs 805 radiating from the fixing centres.

Figure 9 is an exploded view of the hook 201 assembled around the bottom end of the upper member of the front fork 107 as seen in Figure 8, with the addition of a packing strip 901 which is positioned between said front fork 107 and the internal diameters 902 and 903 of shells 601 and 602.

( The purpose of the packing strip is both to increase the amount of purchase of the hook 201 on said front fork 107 and also to allow the use of the hook 201 with front forks having diameters smaller than fork 107. In such cases the tape packs out the difference in size, where the variation is within about ten millimetres in diameter. In a preferred embodiment said packing strip consists either of self-adhesive tape or else an extruded strip of rubber or thermoplastic elastomer. In the case of said extrusion the profile could be castellated so as to correspond with that on the internal diameters 902 and 903 of shells 601 and 602.

Claims (51)

Claims

1. A hook for use on the front forks of a motorcycle, configured to engage within a guard situated adjacent to said front forks, where an effect of said engagement is to enable said motorcycle to move away from a stationary position at a greater rate of acceleration than would be possible without said engagement.

2. A hook according to claim 1, wherein said hook temporarily engages in a hole provided in said guard such that the front end of said motorcycle is held nearer the ground.

3. A hook according to claim 1 or claim 2, wherein the lower members of said front forks are temporarily retained within the upper members of said forks at a higher position than prior to the engagement of said hook.

4. A hook according to any of claims 1 to 3, wherein said hook consists of a collar fitted around one of said front forks; hooking means provided adjacent to said collar; and fixing means by which said collar may be fastened to and unfastened from said front forks.

5. A hook according to any of claims 1 to 4, wherein said hook consists substantially of more than one component fitted around the shank of said front fork.

6. A hook according to claim 5, wherein said hook consists substantially of two halves fitted around the shank of said front fork.

(

7. A hook according to claim 5 or claim 6, wherein said components are removably fastened together.

8. A hook according to claim 7, where the means of removably fastening said halves together is a nut and bolt assembly.

9. A hook according to claim 8, where said bolt is of the caphead type.

10. A hook according to claim 8 and claim 9, where said nut is of the shakeproof Nylock _ type.

11. A hook according to any of claims 5 to 10, where said substantial components are removably joined at a pivot assembly.

12. A hook according to claim 11, where said pivot assembly consists of a hinge barrel and co-operating cradle.

13. A hook according to any of claims 1 to 12, wherein said hook is provided with strengthening ribs.

14. A hook according to claim 13, wherein said ribs provide additional grip against the front forks of a motorcycle where said ribs are located about the internal diameter of said hook.

15. A hook according to any of claims 4 to 14, wherein the external diameters of said shells are provided with a recess in order to allow the fitting of tapes bearing logos, designs and the like.

16. A hook according to any of claims 1 to 15, wherein said hook is manufactured by a process of injection moulding of a plastics material.

17. A hook according to any of claims 1 to 16, wherein said plastics material is acetal.

18. A hook according to claim 17, wherein said acetal is of the acetal-F20-03 reinforced grade.

19. A hook according to any of claims 16 to 18, wherein said moulding tool incorporates an interchangeable insert.

20. A hook according to any of claims 1 to 15, wherein said hook is manufactured by a process of casting in metal.

21. A hook according to claim 20, wherein said metal is aluminium.

22. A hook according to any of claims 1 to 21, wherein said hook incorporates a separate packing element to effectively decrease its internal diameter.

23. A method of manufacturing a hook for use on the front forks of a motorcycle, configured to engage within a guard situated adjacent to said front forks, where an effect of said engagement is to enable said motorcycle to move away from a stationary position at a greater rate of acceleration.

24. A method of manufacturing a hook according to claim 23, wherein said hook temporarily engages in a hole provided in said guard such that the front end of said motorcycle is held nearer the ground.

(

25. A method of manufacturing a hook according to claim 23 or claim 24, wherein the lower members of said front forks are temporarily retained within the upper members of said forks at a higher position than prior to the engagement of said hook.

26. A method of manufacturing a hook according to any of claims 23 to 25, wherein said hook consists of a collar fitted around one of said front forks; hooking means provided adjacent to said collar; and fixing means by which said collar may be fastened to and unfastened from said front forks.

27. A method of manufacturing a hook according to any of claims 23 to 26, wherein said hook consists substantially of more than one component fitted around the shank of said front fork.

28. A method of manufacturing a hook according to claim 27, wherein said hook consists substantially of two halves fitted around the shank of said front fork.

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29. A method of manufacturing a hook according to claim 27 or claim 28, wherein said components are removably fastened together.

30. A method of manufacturing a hook according to claim 29, where the means of removably fastening said halves together is a nut and bolt assembly.

31. A method of manufacturing a hook according to claim 30, where said bolt is of the caphead type.

(

32. A method of manufacturing a hook according to claim 30 and claim 31, where said nut is of the shakeproof "Nylock"_ type.

33. A method of manufacturing a hook according to any of claims 27 to 32, where said substantial components are removably joined at a pivot assembly.

34. A method of manufacturing a hook according to claim 33, where said pivot assembly consists of a hinge barrel and co-operating cradle.

35. A method of manufacturing a hook according to any of claims 23 to 34, wherein said hook is provided with strengthening ribs.

36. A method of manufacturing a hook according to claim 35, wherein said ribs provide additional grip against the front forks of a motorcycle where said ribs are located about the internal diameter of said hook.

37. A method of manufacturing a hook according to any of claims 26 to 36, wherein the external diameters of said shells are provided with a recess in order to allow the fitting of tapes bearing logos, designs and the like.

38. A method of manufacturing a hook according to any of claims 23 to 37, wherein said hook is injection moulded in a plastics material.

39. A method of manufacturing a hook according to any of claims 23 to 38, wherein said plastics material is acetal.

(

40. A method of manufacturing a hook according to claim 39, wherein said acetal is of the acetal-F20-03 reinforced grade.

41. A method of manufacturing a hook according to any of claims 38 to 40, wherein said moulding tool incorporates an interchangeable insert.

42. A method of manufacturing a hook according to any of claims 23 to 37, wherein said hook is manufactured by a process of casting in metal.

43. A method of manufacturing a hook according to claim 42, wherein said metal is aluminium.

44. A method of manufacturing a hook according to any of claims 23 to 43, wherein said hook incorporates a separate packing element to effectively decrease its internal diameter.

45. A method of enabling a motorcycle to move away from a stationary position at a greater rate of acceleration by means of a hook for use on the front forks of a motorcycle than would be possible without said engagement, wherein said hook is configured to engage within a guard situated adjacent to said front forks.

46. A method of enabling a motorcycle to move away from a stationary position at a greater rate of acceleration according to claim 45, wherein said hook temporarily engages in a hole provided in said guard such that the front end of said motorcycle is held nearer the ground.

(

47. A method of enabling a motorcycle to move away from a stationary position at a greater rate of acceleration according to claim 45 or claim 46, wherein the lower members of said front forks are temporarily retained within the upper members of said forks at a higher position than prior to the engagement of said hook.

48. A method of enabling a motorcycle to move away from a stationary position at a greater rate of acceleration according to any of claims 45 to 47, wherein said hook consists of a collar fitted around one of said front forks; hooking means provided adjacent to said collar; and fixing means by which said collar may be fastened to and unfastened from said front forks.

49. A hook substantially as herein described with reference to the accompanying figures.

50. A method of manufacturing a hook substantially as herein described with reference to the accompanying figures.

51. A method of enabling a motorcycle to move away from a stationary position at a greater rate of acceleration than would be possible without said engagement as herein described with reference to the accompanying figures..