WO1999067122A1

WO1999067122A1 - Trailer wheel assembly

Info

Publication number: WO1999067122A1
Application number: PCT/GB1999/001868
Authority: WO
Inventors: Ian Charles Howlett
Original assignee: Howlett Ian C
Priority date: 1998-06-23
Filing date: 1999-06-23
Publication date: 1999-12-29
Also published as: GB9813419D0; GB2354494B; AU4378499A; GB2354494A; GB0100049D0

Abstract

Boats are conventionally transported by road on a trailer (2). The axles (7) of the road trailer (2) comprise ball or roller bearings (12) housed in an axle hub to reduce the friction experienced. However, when a boat is launched the road trailer (2) is usually immersed in the water. There is a risk of corrosion damage to the bearings especially if the road trailer is placed in seawater. There is then the potential of bearing failure at motoring speeds. One known solution is to provide a separate launching trolley which is carried by the road trailer. Such trailers are known as combination trailers. The wheels of the launching trolley generally have a pair of plain bearing wheel hubs which rotate on the two trolley axles and do not generally include ball or roller bearings as they do not experience high rotational speeds. The use of a road trailer plus a launching trolley significantly adds to the complexity of manufacture and the weight of the load being towed. The present invention provides a trailer comprising two interchangeable sets of detachable wheel assemblies (1) and a quick release mechanism (30).

Description

TRAILER WHEEL ASSEMBLY

The present invention relates to a detachable wheel assembly for a trailer and is concerned particularly, although not exclusively, with sets of detachable wheel assemblies for a boat trailer.

Boats are conventionally transported by road on a trailer. The axles of the road trailer comprise ball or roller bearings housed in an axle hub to reduce the friction experienced. However, when a boat is launched the road trailer is usually immersed in the water. There is a risk of corrosion damage to the bearings especially if the road trailer is placed in seawater. There is then the potential of bearing failure at motoring speeds. One known solution is to provide a separate launching trolley which is carried by the road trailer. Such trailers are known as combination trailers. The wheels of the launching trolley generally have a pair of plain bearing wheel hubs which rotate on the two trolley axles and do not generally include ball or roller bearings as they do not experience high rotational speeds. The use of a road trailer plus a launching trolley significantly adds to the complexity of manufacture and the weight of the load being towed.

According to a first aspect of the present invention there is provided a trailer comprising two interchangeable sets of detachable wheel assemblies.

Preferably the first set of wheel assemblies comprise respective wheels each attached to a wheel hub, and each comprising coaxial radially inner tubular sleeve assemblies adapted to be secured to trailer axles, and a second set of wheel assemblies comprising respective wheels each attached to a wheel hub, and each second set of wheel assemblies comprising a coaxial radially inner tubular sleeve and rolling bearing means, the tubular sleeves of the second set of wheel assemblies each being adapted to be secured to the trailer axles, the arrangement being such that, in use, either of the first or second sets of wheel assemblies is placed on the respective axles of the trailer and the respective wheel hubs of said sets of wheel assemblies rotate about the respective axis of the inner tubular sleeve assembly.

Preferably each set of detachable wheel assemblies is secured to the trailer by quick release means.

Preferably the trailer comprises a set of detachable supporting struts to replace the wheel assemblies when the trailer is static.

According to the second aspect of the present invention there is provided a detachable wheel assembly for a boat trailer, said detachable wheel assembly comprising quick release means being operative from a first condition wherein the detachable wheel assembly is secured to the boat trailer frame, to a second condition wherein the wheel assembly is detached from the boat trailer frame.

According to a first preferred assembly of the present invention the detachable wheel assembly for a boat trailer comprises a wheel attached to a wheel hub, and a coaxial radially inner tubular sleeve assembly adapted to be secured to a boat trailer axle, the arrangement being such that, in use, the wheel hub rotates about the axis of the inner tubular sleeve assembly.

Preferably, the inner tubular sleeve assembly is secured to the boat trailer axle by the quick release means. It is preferable that the inner tubular sleeve assembly comprises a tubular sleeve and rolling bearing means. The rolling bearing means preferably comprises a radially innermost bearing housing and a radially outermost bearing housing, the wheel hub being preferably in contact with the radially innermost bearing housing, the arrangement being such that in use the radially innermost bearing housing remains substantially stationary and the radially outermost bearing housing rotates about the axis of the tubular sleeve assembly.

Alternatively, the wheel hub and radially inner tubular sleeve form a plain bearing arrangement for the wheel assembly.

The rolling bearing means preferably comprises two radial bearings axially spaced along the inner sleeve, the arrangement being such that the wheel hub, the inner sleeve and the two radial bearings define an annular chamber.

Alternatively, the rolling bearing means preferably comprises two radial bearings being axially separated by a spacing tube which is in contact with the inner sleeve, the arrangement being such that the wheel hub, the spacing tube and the two radial bearings define an annular chamber.

Preferably the annular chamber contains a friction reducing substance.

Preferably, the inner tubular sleeve assembly comprises means to prevent substantial axial movement of the wheel hub when the detachable wheel assembly is in use.

The means to prevent substantial axial movement preferably comprises a portion extending radially from the radially outermost surface of the tubular sleeve against which the wheel hub abuts. The portion is preferably an annular disc. It is also preferable that the means to prevent substantial axial movement comprises two annular discs spaced axially, and being disposed either side of the wheel hub. Preferably one of the annular discs is removable from the inner tubular sleeve.

It is preferable that said quick release means to secure the inner tubular sleeve to a boat trailer comprises a bar extending through a hole formed through the boat trailer axle and inner tubular sleeve, the hole being transverse to the axis of the assembly and the boat trailer axle.

Preferably the bar is a quick release pin. Alternatively, the bar is a nut and bolt assembly. The term 'quick release pin' may incorporate any type of suitable release pin such as, but not limited to, a split pin or spring loaded drop nose pin.

The securing means preferably secures the detachable annular disc substantially against the inner tubular sleeve.

It is preferable that the securing means comprises a tubular section formed with two holes disposed to correspond with the hole through the axle and the inner sleeve and adapted to receive the bar, the arrangement being such that, in use, the tubular section is placed over an end of the inner tubular sleeve and abuts the detachable annular disc, substantially holding said disc in contact with one of the rolling bearings, the tubular section being secured by the bar.

According to a second preferred assembly of the present invention the detachable wheel assembly comprises a wheel attached to a wheel hub, rolling bearing means and a detachable axle, the arrangement being such that the wheel hub and rolling bearing means are secured to the axle and the detachable axle is secured to the boat trailer frame by the quick release means. The detachable axle is preferably secured to a suspension arm of the trailer frame.

Preferably the quick release means is in the form of a removable pin, the arrangement being such that in the first condition said pin extends through the suspension arm and is received by a slot formed in the axle.

The slot formed in the axle is preferably an annular slot extending around the circumference of the axle.

Alternatively the quick release mechanism comprises a removable pin extending through a hole in the axle of the boat trailer the arrangement being such that, in use, the pin prevents the wheel assembly detaching from the axle.

The pin preferably comprises locking means. The locking means preferably comprises a portion pivotally connected to one end of the pin and biasing means. The biasing means is preferably in the form of a spring.

According to a third preferred assembly of the present invention the detachable wheel assembly comprises a wheel attached to a wheel hub, bearing means rotatable about an axial and a subframe portion, the arrangement being such that the subframe portion carries the axial, the bearing means and wheel hub and the quick release means secures the subframe portion to the boat trailer frame.

Preferably the subframe portion is secured to, and forms part of, the suspension arm of the boat trailer frame.

The bearing means preferably comprises rolling bearing means. Alternatively the bearing means comprise plain bearing means.

According to a third aspect of the present invention there is provided a boat trailer comprising at least one wheel assembly according to the first or second aspect of the present invention.

Preferably, each wheel assembly is received by a separate trailer axle.

Each wheel assembly preferably comprises two or more wheels to help dissipate the load of the boat trailer for use in soft ground conditions.

Each axle preferably comprises a free end by which the wheel assembly is lifted from the ground by suitable jacking means.

According to a fourth aspect of the present invention there is provided a boat trailer comprising two or more sets of detachable wheel suspension assemblies, each assembly comprising a wheel rotatable about a wheel axle; a detachable suspension tube assembly connected to said wheel axle and suspension tube quick release means, the arrangement being such that, in use, one of the sets of detachable wheel suspension assemblies is attached to the boat trailer.

The invention may be carried into practice in various ways, but an embodiment will now be described by way of example only, with reference to the accompanying drawings in which:

Figure 1 shows a cross-section of a first embodiment of a wheel assembly mounted on an axle of a boat trailer,

Figure 2 shows a plan view of the boat trailer partly shown in Figure 1 , Figure 3 shows a rear view of the boat trailer carrying a boat,

Figure 4 shows a cross-section view of a second embodiment of a detachable wheel assembly mounted on a boat trailer frame,

Figure 5 shows a cross-section through AA of the release mechanism of the detachable wheel assembly shown in Figure 4,

Figure 6 shows a cross-section of a jig used for manufacturing the release mechanism shown in Figure 4,

Figure 7 shows a cross-section through BB of the jig shown in Figure 6 and a drill bit,

Figure 8 shows a side view of a third embodiment of a detachable wheel assembly secured to a boat trailer suspension arm, and

Figure 9 shows a side view of part of the detachable wheel assembly shown in Figure 8.

Referring to Figures 1 to 3, a detachable wheel assembly 1 for a boat trailer 2 comprises a wheel 4 attached to a wheel hub 6 and an inner tubular sleeve assembly 8. The wheel assembly is rotatable about axis XX of the axle 7 of the trailer 2.

The inner tubular sleeve assembly 8 comprises a substantially circular tube sleeve 10 and two single row radial ball bearings 12, 13. The ball bearing 12 comprises a plurality of balls 18 and a radially innermost annular bearing housing 14 carried by the sleeve 10 and a radially outermost annular bearing housing 16 which carries part of the hub 6. The ball bearing 13 comprises similar components and arrangement thereof as ball bearing 12. Axially disposed between the ball bearings 12, 13 is an intermediate circular tube 19.

The two bearings 12, 13, the intermediate tube 19 and the hub 6 define an enclosed annular chamber 20. The chamber 20 contains a suitable friction reducing substance such as grease.

An annular ring washer 22 is disposed at one end of the sleeve 10 and is welded to the radially outermost surface of the sleeve 10. The annular ring washer 22 can be attached to the sleeve by any suitable means. The washer 22 abuts the bearing 12. A second annular ring washer 24 abuts the bearing 13. The washer 24 is detachably held on the sleeve 10 and in contact with the bearing 13 by a bellmouth tubular support section 26 which is slid over an end of the sleeve 10. The support section 26 is held in position by a spring loaded drop nose pin 30. The washers 22, 24 provide a shielding cover over one end of each bearing which helps to keep unwanted particles from entering the bearings 12, 13.

A hole transverse to the axis XX is formed through the trailer axle 7, the sleeve 10 and the tubular support 26 and the securing quick release spring loaded drop nose pin 30 extends there through. The securing pin 30 can alternatively be a nut and bolt. The securing pin 30 prevents the wheel assembly 1 from moving in an axial direction. It will be appreciated that any suitable quick release arrangement can be used to secure the wheel assembly 1 to the wheel axle 7.

The axle 7 comprises a first part 7a for carrying the wheel assembly and a second part 7b extending from a trailer suspension arm section 32 which provides a convenient jacking point. The wheel assembly shown in Figure 1 is used when towing a boat on the highway. However, when launching the boat it is desirable not to immerse the wheel assembly 1 used for road use in the water. The wheel assembly 1 is easily removed by first lifting the wheel 4 off the ground by placing a suitable jack under the second part 7b of the axle 7 and extending the jack. Once the wheel assembly 1 is off the ground the pin 30 is removed and the wheel assembly is slid from the axle 7 in direction B. A second wheel assembly (not shown) is then slid onto the axle 7.

The second wheel assembly can be the same as the assembly 1 shown in Figure 1. The second wheel assembly is then only used for launching the boat. Alternatively, the second 'launching' wheel assembly is similar to the assembly 1 except that the second 'launching' wheel assembly does not generally comprise rolling bearings. The rolling bearings of the second wheel assembly are replaced by a plain tubular bearing that rotatably slides over the sleeve 10.

It will be appreciated that the trailer can comprise a plurality of wheel assemblies. The trailer can have different wheel assemblies according to the present invention, suitable for different loads and different towing or launching situations.

The boat trailer can also comprise a set of detachable supporting legs to replace the wheel assemblies when the trailer is static. The support legs would be used when the boat and trailer are being stored in a dinghy park. The support legs may comprise suitable locking means to prevent their removal. The use of the support legs provides greater security when the boat and trailer are being kept in a dinghy park. Alternatively, the boat trailer can rest on the suspension arm section 32 when the wheel assemblies are removed.

The use of the support legs will help to reduce the storage space required in the dinghy park.

A further benefit of the present invention is provided because the boat trailer comprises two sets of wheel assemblies; one for road use and one for launching. If one of the wheels of the first wheel assembly has a puncture then it can be easily replaced by one of the wheels from the second wheel assembly. Hence, if the road wheel assembly has a puncture then the wheel can be replaced by a wheel from the launching wheel assembly.

It will be appreciated that the road wheel assembly does not necessarily need to comprise rolling bearings. A suitably wear resistant material can be used for the plain bearing arrangement.

The inner tubular sleeve assembly 1 can be adapted to fit any shape or kind of axle. The shape and dimensions of the tube sleeve 10 can be designed to correspond to the different types of axle design including, but not limited to, stub axles, tapered stub axles, axle hubs and tapered axle hubs.

Turning to Figures 4 and 5 , these show a further embodiment of a detachable wheel assembly for a boat trailer 2. This embodiment includes similar features to those described with reference to Figures 1 to 3 of the accompanying drawings and therefore similar numerals have been used to describe similar components and further description will not be given. However, with this embodiment the bearings 12 , 13 are mounted directlv on to a detachable axle 72. The axle 72 is formed with a screwthread at one end 74 and an annular shoulder 76 located at an intermediate point between the two ends of the axle. The innermost annular bearing housing 14 abuts the shoulder 76 and is held in contact therewith by a castle nut 78 threaded on to the screwthread at the end 74. The opposite end portion 80 of the axle 72 extends through a circular tube 82. A tube section 82 extends perpendicularly through the trailer section 32 and is welded thereto. The distal portion of the end portion 80 is formed with an annular groove 84 extending around the circumference of the axle 72.

The tube section 82 is formed with two holes 83, 85 that extend through the section wall. The holes are spaced from the axis XX of the tube section 82.

The holes 83, 85 and groove 84 are adapted to receive the straight leg of an 'R' clip 90. When the 'R' clip 90 is inserted through the holes 83, 85 and the groove 84, the detachable axle 72 is secured to the tube section 82. This arrangement provides a convenient quick release mechanism for the wheel assembly. It will be appreciated that the 'R' clip 90 can be inserted when the axle 72 is in any rotational orientation due to the groove 84.

Figures 6 and 7 show a drilling jig 92 used to form the holes 83, 85 comprising a rectangular block 93 formed with a first inner circular bore 94 extending from one end of the block 93 to a point about halfway through the block 93 and a second inner circular bore 95 of a smaller diameter extending from the innermost end of the bore 94 to the other end of the block 93.

Extending co-axiallv through the bores 94, 95 is a circular bar 96 of a diameter equal to the diameter of the bore 95. One end of the bar 95 is welded to the block 93. The radially outermost surface of the bar 96 and the radially innermost surface of the bore 94 form an annular slot 97.

The block 93 is formed with a vertical circular hole 98 extending from the uppermost surface through to the lowermost surface of the block 93.

The hole 98 is distant from the central axis YY of the block 93. The block 93 comprises a locking screw 99.

In use the tube section 82 is placed within the annular slot 97 until the section 82 abuts an innermost annular shoulder 100. The locking screw 99 is tightened downwardly until it abuts and holds the tube section 82. A drill bit 102 is pushed downwardly through the hole 98 such that it cuts through the wall sections of the circular tube 82 so forming the holes 83, 85.

In an alternative embodiment of the present invention the boat trailer comprises two pairs of detachable wheel suspension assemblies 60. Only one pair of suspension assemblies is used with the trailer at a time. In use the assemblies are detachably retained within the respective ends of the main box-section cross member 62 of the trailer. The first pair of suspension assemblies comprises wheel assemblies to be used on the highway and the second pair of suspension assemblies comprises wheel assemblies to be used for launching the boat.

The suspension assemblies comprise the rectangular section 32 and a second rectangular section 64. One end of section 64 is held within the section 32. The section 64 extends perpendicularly from section 32 and into the main box-section cross member 62. The suspension assemblies are held within the ends of the cross member 62 by suitable quick release means . Referring to Figures 8 and 9, these show a further embodiment of a detachable wheel assembly for a boat trailer. This embodiment also includes many components that are the same as those described with reference to Figures 1 to 3 of the accompanying drawings and therefore similar numerals have been used to reference the similar components and further description of these components will not be given.

However, with this embodiment the detachable wheel assembly 100 comprises a wheel 4 attached to a wheel hub 6, rolling bearing means (not shown) for the wheel 4 and a detachable subframe portion 102 secured to the suspension arm 32 of the trailer frame 104 by a quick release spring-loaded drop nose pin 30.

The detachable subframe portion 102 comprises an outer box section 106 and an inner box section 108 each having a rectangular cross-section. The wheel axle 7 is attached to the outer box section 106 and extends therethrough and in a direction perpendicularly away from the longitudinal axis of the outer box section 106. The inner box section 108 is of a smaller diameter than that of the outer box section 106. The inner box section 108 is formed with two holes 110, 111 which are positioned such that when the inner box section 108 is inserted into the lowermost open end of the suspension arm 32, the holes 110, 111 align with two holes 112, 113 formed in the arm 32. The detachable wheel assembly 100 is secured to the arm 32 by the pin 30 passing through the respective holes 110, 111 , 112, 113 so preventing the inner box section 108 from being removed from the arm 32.

All of the components of the wheel assembly and parts of the trailer suspension and framework are made from suitable corrosive-resistant material such as, but not limited to, stainless steel . It will be appreciated that all of the above described embodiments of the present invention provide a convenient method of exchanging interchangeable sets of wheel assemblies. In the embodiments described the areas of the wheel assembly that are normally covered with grease or oil are not exposed to the operator when exchanging the sets of wheel assemblies. The connection means for the wheel assemblies remains separate from the areas which are usually covered with lubrication. This important feature helps the user of the boat trailer avoid contact with the lubrication means.

Claims

1. A trailer comprising two interchangeable sets of detachable wheel assemblies.

2. A trailer as claimed in claim 1 , wherein the first set of wheel assemblies comprise respective wheels each attached to a wheel hub, and each comprising coaxial radially inner tubular sleeve assemblies adapted to be secured to trailer axles, and a second set of wheel assemblies comprising respective wheels each attached to a wheel hub, and each second set of wheel assemblies comprising a coaxial radially inner tubular sleeve and rolling bearing means, the tubular sleeves of the second set of wheel assemblies each being adapted to be secured to the trailer axles, the arrangement being such that, in use, either of the first or second sets of wheel assemblies is placed on the respective axles of the trailer and the respective wheel hubs of said sets of wheel assemblies rotate about the respective axis of the inner tubular sleeve assembly.

3. A trailer as claimed in claims 1 or 2, wherein each set of detachable wheel assemblies is secured to the trailer by quick release means.

4. A trailer as claimed in any one of the previous claims, wherein the trailer comprises a set of detachable supporting struts to replace the wheel assemblies when the trailer is static.

5. A detachable wheel assembly for a boat trailer, said detachable wheel assembly comprising quick release means being operative from a first condition wherein the detachable wheel assembly is secured to the boat trailer frame, to a second condition wherein the wheel assembly is detached from the boat trailer frame.

6. A detachable wheel assembly for a boat trailer as claimed in claim

5, wherein the detachable wheel assembly comprises a wheel attached to a wheel hub, and a coaxial radially inner tubular sleeve assembly adapted to be secured to a boat trailer axle, the arrangement being such that, in use, the wheel hub rotates about the axis of the inner tubular sleeve assembly.

7. A detachable wheel assembly for a boat trailer as claimed in claim

6, wherein the inner tubular sleeve assembly is secured to the boat trailer axle by the quick release means.

8. A detachable wheel assembly for a boat trailer as claimed in claim 6 or claim 7, wherein the inner tubular sleeve assembly comprises a tubular sleeve and rolling bearing means.

9. A detachable wheel assembly for a boat trailer as claimed in claim

8. wherein the rolling bearing means comprises a radially innermost bearing housing and a radially outermost bearing housing, the wheel hub being in contact with the radially innermost bearing housing, the arrangement being such that in use the radially innermost bearing housing remains substantially stationary and the radially outermost bearing housing rotates about the axis of the tubular sleeve assembly.

10. A detachable wheel assembly for a boat trailer as claimed in any one of claims 5 to 7, wherein the wheel hub and radially inner tubular sleeve form a plain bearing arrangement for the wheel.

11. A detachable wheel assembly for a boat trailer as claimed claim 8 or claim 9, wherein the rolling bearing means comprises two radial bearings axially spaced along the inner sleeve, the arrangement being such that the wheel hub, the inner sleeve and the two radial bearings define an annular chamber.

12. A detachable wheel assembly for a boat trailer as claimed in claim 8 or claim 9, wherein the rolling bearing means preferably comprises two radial bearings being axially separated by a spacing tube which is in contact with the inner sleeve, the arrangement being such that the wheel hub, the spacing tube and the two radial bearings define an annular chamber.

13. A detachable wheel assembly for a boat trailer as claimed claim 12, wherein the annular chamber contains a friction reducing substance.

14. A detachable wheel assembly for a boat trailer as claimed in any one of claims 6 to 13, wherein the inner tubular sleeve assembly comprises means to prevent substantial axial movement of the wheel hub when the detachable wheel assembly is in use.

15. A detachable wheel assembly for a boat trailer as claimed in claim 14, wherein the means to prevent substantial axial movement comprises a portion extending radially from the radially outermost surface of the tubular sleeve against which the wheel hub abuts.

16. A detachable wheel assembly for a boat trailer as claimed in claim 15, wherein the portion is preferably an annular disc.

17. A detachable wheel assembly for a boat trailer as claimed in claim 14, wherein the means to prevent substantial axial movement comprises two annular discs spaced axially, and being disposed either side of the wheel hub.

18. A detachable wheel assembly for a boat trailer as claimed in claim 17, wherein one of the annular discs is removable from the inner tubular sleeve.

19. A detachable wheel assembly for a boat trailer as claimed in any one of claims 6 to 18, wherein the quick release means to secure the inner tubular sleeve to a boat trailer comprises a bar extending through a hole formed through the boat trailer axle and inner tubular sleeve, the hole being transverse to the axis of the assembly and the boat trailer axle.

20. A detachable wheel assembly for a boat trailer as claimed in claim 19, wherein the bar is a quick release pin.

21. A detachable wheel assembly for a boat trailer as claimed in claim 19, wherein the bar is a nut and bolt assembly.

22. A detachable wheel assembly for a boat trailer as claimed in any one of claims 16 to 21, wherein the securing means secures the detachable annular disc substantially against the inner tubular sleeve.

23. A detachable wheel assembly for a boat trailer as claimed in any one of claims 19 to 22, wherein the securing means comprises a tubular section formed with two holes disposed to correspond with the hole through the axle and the inner sleeve and adapted to receive the bar, the arrangement being such that, in use, the tubular section is placed over an end of the inner tubular sleeve and abuts the detachable annular disc, substantially holding said disc in contact with one of the rolling bearings, the tubular section being secured by the bar.

24. A detachable wheel assembly for a boat trailer as claimed in claim 5 , wherein the detachable wheel assembly comprises a wheel attached to a wheel hub, rolling bearing means and a detachable axle, the arrangement being such that the wheel hub and rolling bearing means are secured to the axle and the detachable axle is secured to the boat trailer frame by the quick release means.

25. A detachable wheel assembly for a boat trailer as claimed in claim 5 or claim 24, wherein the detachable axle is secured to a suspension arm of the trailer frame.

26. A detachable wheel assembly for a boat trailer as claimed in claim

25, wherein the quick release means is in the form of a removable pin, the arrangement being such that in the first condition said pin extends through the suspension arm and is received by a slot formed in the axle.

27. A detachable wheel assembly for a boat trailer as claimed in claim

26, wherein the slot formed in the axle is an annular slot extending around the circumference of the axle.

28. A detachable wheel assembly for a boat trailer as claimed in claim 5, wherein the quick release mechanism comprises a removable pin extending through a hole in the axle of the boat trailer the arrangement being such that, in use, the pin prevents the wheel assembly detaching from the axle.

29. A detachable wheel assembly for a boat trailer as claimed in any one of claims 26 to 28, wherein the pin comprises locking means.

30. A detachable wheel assembly for a boat trailer as claimed in claim 29, wherein the locking means comprises a portion pivotally connected to one end of the pin and biasing means.

31. A detachable wheel assembly for a boat trailer as claimed in claim 30, wherein the biasing means is preferably in the form of a spring.

32. A detachable wheel assembly for a boat trailer as claimed in claim 5, wherein the detachable wheel assembly comprises a wheel attached to a wheel hub, bearing means rotatable about an axial and a subframe portion, the arrangement being such that the subframe portion carries the axial, the bearing means and wheel hub and the quick release means secures the subframe portion to the boat trailer frame.

33. A detachable wheel assembly for a boat trailer as claimed in claim 32, wherein the subframe portion is secured to, and forms part of, the suspension arm of the boat trailer frame.

34. A detachable wheel assembly for a boat trailer as claimed in claim 32 or claim 33, wherein the bearing means comprises rolling bearing means .

35. A detachable wheel assembly for a boat trailer as claimed in claim 32 or claim 33, wherein the bearing means comprise plain bearing means.

36. A boat trailer comprising at least one wheel assembly as claimed in any one of the preceding claims.

37. A boat trailer as claimed in claim 36, wherein each wheel assembly is received by a separate trailer axle.

38. A boat trailer as claimed claim 36 or claim 38, wherein each wheel assembly comprises two or more wheels to help dissipate the load of the boat trailer when used in soft ground conditions.

39. A boat trailer as claimed in any one of the preceding claims 36 to 38, wherein each axle comprises a free end by which the wheel assembly is lifted from the ground by suitable jacking means.

40. A boat trailer comprising two or more sets of detachable wheel suspension assemblies, each assembly comprising a wheel rotatable about a wheel axle; a detachable suspension tube assembly connected to said wheel axle and suspension tube quick release means, the arrangement being such that, in use, one of the sets of detachable wheel suspension assemblies is attached to the boat trailer.

41. A boat trailer substantially as herein described with reference to the accompanying drawings.