AU2016101673A4 - Long Vehicle Combination with Steerable Wheels - Google Patents

Abstract

A longer vehicle combination for road transport uses a prime mover 6 connected to a front trailer 12 and then a rear trailer 16 and the trailer 12,16 axles are arranged in three tandem sets 14,24,18. The leading tandem set 24 of the rear trailer is part of a dolly 22 which supports a fifth wheel 20 of the rear trailer 16 and the spacing of the tandem sets 14,24,18 is 1.5-2.5m. The rear axle of each tandem set 14,24,18 has a pair of self-steered wheels 14',24',18' which assist in the reduction of the turning circle over rough terrain when the combination is a bulk milk tanker combination. Fig. 1 co (NJ0

Description

TITLE OF INVENTION

Long Vehicle Combination With Steerable Wheels TECHNICAL FIELD

This invention concerns larger combination vehicles (LCVs).

BACKGROUND

In Australia the maximum width of road vehicles is 2.5m and the maximum height is 4.3m. Vehicles may exceed these limits but are restricted to selected road routes.

The most popular configurations of trailer combinations have a prime mover which with dual drive axles, with three axles on each trailer and four tires on each axle. In lighter duty combinations the trailer may have only two axles.

In trailer design it is usual to limit the load carried to 9 tonnes per axle. When the trailer has tandem axles, the pair in practice can only support 17 tonnes. This would normally be overcome by using a triple axle configuration but this in turn introduces other unwelcome restrictions.

Bulk liquid tankers face special design requirements in that the steering characteristics change moving from full to empty. If the trailer is being used for milk collection from farm to milk processing centres, the access road may not be ideal having regard to the length of the truck. Its turning circle may be too large for some collection areas having regard to the layout of farm buildings. If the vehicle combination has to travel over grassy areas these may become muddy in wet weather and the prime mover may lose traction.

Reducing length to reduce turning circle tends to proportionally reduce load capacity. This affects the economics of the collection operation. B-doubles are limited to a length of 26m if they are fitted with front underrun protection devices and have a maximum weight limit. Milk tankers must be able to travel in all parts of the state in which they collect on behalf of a business. Such vehicle combinations commonly have a 12m turning circle.

SUMMARY OF INVENTION

This invention provides a longer vehicle combination comprising a prime mover, a first trailer and a rear trailer, wherein the trailer axles are arranged in three tandem groups. The rear of the front trailer may have a tandem group, the rear trailer may have a leading tandem group and a trailing tandem group. The leading tandem group of the rear trailer may support a fifth wheel of the rear trailer. The spacing of the tandem may be wider than is customary. The spacing may be 1.5-2.5m. The spacing between the tandem groups may be adjusted so that the load is better distributed and the limit or mass is increased.

In a preferred arrangement the vehicle combination has a three axle prime mover with a fifth wheel and connected to this fifth wheel is the lead tanker, via its king pin. This trailer is supported at its rear by two axles, spaced widely apart (between 1.5m and 2.5m) to improve the performance of the steer axle that the rear axle possesses. A tandem dolly is connected to the rear of the lead trailer via a ring feeder, and may or may not have a steer axle at its rear. The dolly supports a fifth wheel and connected to this fifth wheel is the king pin of the tag trailer.

The tag trailer is also supported by tandem axles at its rear (between 1.5m and 2.2m), with the most rear axle being self-steering. The king pins and fifth wheels are located in positions to optimize weight distribution.

The tandem axles of both trailers may be 1900-2100mm apart.

The tandem axles of the dolly may be 1400-1600mm apart.

The rear axle of the front trailer and the front of the dolly frame may be 2200 - 4200mm, and still more preferably 3300-3800mm apart. The distance between the rear tow point of the first trailer to the centre of the fifth wheel supported by the dolly is 3000 - 4500mm, and more preferably 4100-4500mm. The rear tow point being the RINGFEDER® coupling.

The rear axle of each trailer pair may be self-steering. Self-steering for the rear axle of the dolly pair is optional.

The self-steered wheels preferably have castor action.

The vehicle combination of the invention provides a prime mover with a fifth wheel, a front tanker trailer with a pin for coupling to the fifth wheel of the prime mover and tandem axles at the trailer rear, a rear tanker trailer with a pin for coupling to a fifth wheel and tandem axles at the trailer rear, and a dolly with a frame for supporting said fifth wheel, a draw bar for mutually connecting the two trailers, the dolly frame being supported by tandem axles, wherein if the mutual spacing of the tandem axles is x, the separation between the rear driven wheel of the prime mover and the tandem axle of the front trailer and the separation between the rear dolly axle and the tandem axle of the second trailer is about 2.5x. The extent of variation may be +5%.

The dolly aspect of the invention provides a dolly for joining a rear trailer to a front trailer comprising a frame for supporting a fifth wheel, an A-configuration draw bar extending forwardly of the frame, a pair of wheel axles and wheel assemblies rendering the frame mobile, wherein the wheels of the trailing axle are self-steering.

The trailer aspect of the invention provides a trailer with a locating pin for a fifth wheel coupling at the front end and a pair of axles at the rear end, wherein the leading axle has wheels and the trailing axle has self-steered wheels.

Advantageous Effects of Invention 1. The purpose of this arrangement is to share the load more evenly by spacing the axles differently, which is kinder to roads and bridges. The combination can carry three lots of the capacity of two axles, instead of two lots of the capacity of three axles. Therefore, as the load is better distributed, the limit on the mass is increased. Currently in Victoria, the higher mass limit (HML) of three axles is 21TN (7.5TN per axle), and the HML of two axles is 17TN (8.5TN per axle). This means by using tandem axles, all of the axles in the configuration can carry an extra tonne each. 2. The self-steering axles used in this invention also decrease the swept path of the combination. By having the self-steer axles, the swept path can be less than that of a 19m B-double. The self-steer axles are also designed to lock up at higher speed, so that they act as a rigid axle which improves the stability at said higher speeds. 3. The self-steering axles will reduce the tyre scrub, which in turn reduces the tyre wear. This in turn means less friction, less fuel consumption and lower emissions. If the combination only drives from factory to factory, self-steer axles are less critical.

In another aspect, the invention provides: a large vehicle combination including: one or more tag trailers each having a plurality of wheel sets with trailer axles arranged in group sets; wherein : the rearmost wheel set of at least one group set are steered; and the spacing between adjacent in-line wheels in the same group set is greater than in traditional groups sets, the spacing of adjacent axles being between about 1.5m and about 2.5m.

The steering of the rear set of wheels may be achieved by a variety of configurations, including self-tracking or steerable axles, individually steered wheels or other mechanisms whereby the wheels track in response to the direction of travel of a lead towing vehicle. The steerability of the rear-most wheels greatly reduces wear on the tyres, enabling an extension of the life of the tyres of the rear steerable wheels by a factor of over 3 times, reducing lateral or horizontal drag across road and ground surfaces thereby avoiding damaging wear and tear on roads and ground surfaces.

Another advantage of providing steerable rearmost wheel sets is the reduction in the ring feeder pin and king pin loads during turning. Structural fatigue and wear on component parts of the vehicle are substantially reduced. For example, a king pin load that would normally be 2500kg in a non-steered trailer combination may be reduced by a factor of 2 - 3, down to about 900kg.

The positioning of the ring feeder is preferably immediately behind the first trailer’s end to minimise the distance between the end of the first trailer and the tag trailer’s dolly or forecarriage, whilst providing sufficient clearance for turning. Preferably the ring feeder coupling is located within 300mm - 600mm of the rear of the first trailer.

The swept path of the vehicle is preferably less than about 6m, preferably less than 5.8m, and most preferably 5.7m. Such a small swept path is achieved under the invention by the combination of the spacing of the larger spacing of the wheel axles and the provision of at least one steerable wheel set in the group set. However, the length of the vehicle also is a contributing factor. A standard 25m B Double swept path is about 8.5m, whereas a 26m A Double fitted with wheel group sets according to the invention has a swept path of about 6.33m. A standard 19m B Double has a swept path of about 6.7m, whereas a 20m A-B Double fitted with wheel group sets according to the invention has a swept path of about 5.8m. A standard 30,000L long tri-axle single vehicle has a swept path of about 6.7m, whereas a 26m A Double single lead trailer fitted with wheel group sets according to the invention has a swept path of about 5.7m.

By providing a steerable final wheel set on each tag trailer, the tag trailer is able to pivot about a vertical axis corresponding to the wheel set immediately in front of the trailing steerable wheel set and the steerable wheel set generally turns onto the direction of the path that the lead vehicle is following.

Preferably the group sets comprise a pair of axles in tandem. Preferably the sets of wheels have pairs of wheels, one wheel on each end of the axle, so that only one steerable wheel set is required for each group set. However, group sets may comprise triple axle group sets.

The vehicle combination may have a front trailer and a rear trailer. The rear of the front trailer may have a tandem group, the rear trailer may have a leading tandem group and a trailing tandem group. The leading tandem group of the rear trailer may support a fifth wheel set of the rear trailer. A fifth wheel coupling describes a trailer hitch support structure comprising a substantially horizontal wheel commonly located on the tail end of a prime mover or dolly.

Although counter-intuitive, the spacing of the wheel sets in the tandem (or triple) group is preferably greater than is customary. This greater spacing was thought to be undesirable because of the trade off with regard to vertical load capacity for the relevant group set supporting a vertical loading. However, with regard to this invention, the spacing from axle axis to axle axis of adjacent axles in the tandem or tri-group set is advantageously in the range 1.5-2.5m. The spacing between adjacent axles in each of the tandem groups may be adjusted so that the load is better distributed and the total load limit or capacity of the vehicle is maximised. The spacing allows each axle set to be categorised as an independent or separate axle set that can be rated to carry a 10T load, compared to the smaller load ratings per axle set of about 7T for tandem and triple axle groups. This greatly increases the total load able to be carried by a LCV. For example, a 20m B Double made according to the invention with axles in the same group widely spaced by about 1500 - 2500mm, preferably about 1800 - 2200mm, and most preferably about 2200mm, is designed to carry 63.5T, compared to the equivalent prior art vehicle (a 19m B Double) having a load capacity of 57.5T. Another example is a 26m B Double made according to the invention that has a prime mover with a typical load carrying capacity of 23.5T, but due to the wide spacing of the axles sets within groups of about 1.5 - 2.5m, preferably about 1800 - 2200mm, and most preferably about 1900mm, the first trailer and tag trailer, being supported by 6 wheel sets each rated as a single and independent axle set and engineered to carry a load of up to 10T, results in a significantly larger load capacity of over 70T, preferably 75T, most preferably over 80T and specifically 83.5T, or where single axles are rated to carry up to 9T, a maximum capacity of 77.5T for a LCV that is between 25 - 26m in length.

In a preferred arrangement the vehicle combination has a three axle prime mover with a fifth wheel and connected to this fifth wheel is the lead tanker, via its king pin. This trailer is supported at its rear by two axles, spaced widely apart (between 1.5m and 2.5m) to improve the performance of the steer axle that the rear axle possesses. A tandem dolly is connected to the rear of the lead trailer via a ring feeder, and may or may not have a steer axle at its rear. The dolly supports a fifth wheel and connected to this fifth wheel is the king pin of the tag trailer. The tag trailer is also supported by tandem axles at its rear (the tag trailer axles spaced from one another by between 1.5m and 2.2m), with the rearmost axle being self-steering. The king pins and fifth wheels are located in positions to optimize weight distribution.

The tandem axles of both trailers may be 1900-2100mm apart.

The tandem axles of the dolly may be 1400-1600mm apart.

The rear axle of the front trailer and the front of the dolly frame may be 3300-3800mm apart. The distance between the rear tow point of the first trailer to the centre of the fifth wheel supported by a dolly for the shorter (20m vehicle) in the form of a forecarriage is 3000-4500mm. The rear tow point may be a commercially available RINGFEDER® coupling.

The rear axle of each trailer pair may be self-steering. Self-steering for the rear axle of the dolly pair is optional, but preferable and steerage of this wheel set mitigates against unwanted horizontal forces when the vehicle is turning.

The self-steered wheels preferably have castor action.

The vehicle combination according to one embodiment provides a prime mover with a fifth wheel, a front tanker trailer with a pin for coupling to the fifth wheel of the prime mover and tandem axles at the trailer rear, a rear tanker trailer with a pin for coupling to a fifth wheel and tandem axles at the trailer rear, and a dolly with a frame for supporting said fifth wheel, a draw bar for mutually connecting the two trailers, the dolly frame being supported by tandem axles, wherein if the mutual spacing of the tandem axles is x, the separation between the rear driven wheel of the prime mover and the tandem axle of the front trailer and the separation between the rear dolly axle and the tandem axle of the second trailer is about 2.5x. The extent of variation may be ±5%.

The dolly aspect of the invention provides a dolly for joining a rear trailer to a front trailer comprising a frame for supporting a fifth wheel, an A-configuration draw bar extending forwardly of the frame, a pair of wheel axles and wheel assemblies rendering the frame mobile, wherein the wheels of the trailing axle are self-steering.

The trailer aspect of the invention provides a trailer with a locating pin for a fifth wheel coupling at the front end and a pair of axles at the rear end, wherein the leading axle has wheels and the trailing axle has self-steered wheels.

Advantageous Effects of Invention 1. The purpose of this arrangement is to share the load more evenly by spacing the axles differently, which is kinder to roads and bridges. The combination can carry three lots of the capacity of two axles, instead of two lots of the capacity of three axles. Therefore, as the load is better distributed, the limit on the mass is increased. Currently in Victoria, the higher mass limit (HML) of three axles is 21T (7.5T per axle), and the HML of two axles is 17T (8.5T per axle). This means by using tandem axles, all of the axles in the configuration can carry an extra tonne each. Moreover, advantageously according to the invention, where axle sets in a group set are spaced between 1.5 - 2.5m apart, they still can function as a group set, but are rated as independent or single axles with a load carrying capacity of 10T each. In a 20m B Double made according to the invention, the prime mover steering set of wheels can carry 6.5T, the prime mover tandem axles can carry 17T, and the 4 separate single axles supporting the trailers (see Fig. 4) can each support 10T, for a vehicle total of 63.5T. Substantial elimination of sideways drag from trailing tandem pairs of wheel sets and substantial increase in load capacity of the vehicle are achieved by this new configuration. 2. The self-steering axles used in this invention also decrease the swept path of the combination. Bv having the self-steer axles, the swept path can be less than that of a 19m B-double. The self-steer axles are also designed to lock up at higher speed, so that they act as a rigid axle which improves the stability at said higher speeds. 3. The self-steering axles will reduce the tyre scrub caused by horizontal tracking when cornering, which in turn reduces the tyre wear. This in turn means less friction, less fuel consumption and lower emissions.

In another aspect there is provided a longer vehicle combination for road transport of bulk goods comprising a prime mover, a front trailer and a rear trailer, wherein the trailer axles are arranged in three tandem sets, the rear of the front trailer has a tandem set, the rear trailer has a leading tandem set and a trailing tandem set and the leading tandem set of the rear trailer is part of a dolly which supports a fifth wheel of the rear trailer.

The spacing of the tandem sets may be 1.5-2.5m, preferably 1900-2100mm. The rear axle of the tandem sets preferably has a pair of self-steered wheels which have a caster action as herein defined. The endmost axle of the combination is preferably devoid of caster action. The prime mover may have three axles with a fifth wheel and connected to the fifth wheel may be the front trailer. A tandem dolly may be connected to the rear of the front trailer by a coupling and may have a rear axle with self- steered wheels. The dolly may support a fifth wheel and a tag trailer may be connected to the fifth wheel. The tandem axles of the dolly are preferably 1400-1600mm apart. The tandem axles of both trailers are preferably 1900-2100mm apart. The distance between the tow point of the first trailer to the centre of the fifth wheel supported by the dolly is preferably 30004500mm, preferably about 3030mm, and most preferably 3035mm.

In still another aspect of the invention, there is provided a longer vehicle configuration for the road transport of bulk goods comprising a prime mover with a fifth wheel, a front tanker trailer with a pin for coupling to the fifth wheel of the prime mover and tandem axles at the trailer rear, a rear tanker trailer with a pin for coupling to a fifth wheel and tandem axles at the trailer rear, and a dolly with a frame for supporting said fifth wheel, a draw bar for mutually connecting the two trailers, the dolly frame being supported by tandem axles, wherein if the separation between the rear drive wheel of the prime mover and the tandem axle of the front trailer is x, the separation between the rearmost wheel of the second trailer and the rearmost wheel of the first trailer is about 2.5x. The extent of the variation of the separation is preferably ±5%.

In still another aspect of the invention, there is provided a dolly for joining a rear trailer to a front trailer in a longer vehicle combination for the road transport of bulk goods comprising a frame for supporting a fifth wheel, an A-configuration draw bar extending forwardly of the frame, a pair of wheel axles and wheel assemblies rendering the frame mobile, wherein the wheels of the trailing axle are self-steering.

BRIEF DESCRIPTION OF DRAWINGS

The invention may be better understood from the following non-limiting description of preferred embodiments, in which:

Figure 1 is a side view of a 26m A Double vehicle combination according to one aspect of the invention;

Figure 2a is a schematic side view of a prior art 25m B Double;

Figure 2b is a schematic side view of a prior art 19m B Double;

Figure 3 is a schematic side view of the 26m A Double shown in Fig. 1;

Figure 4 is a schematic side view of a 20m A-B Double vehicle combination according to another aspect of the invention;

Figure 5 is a comparative graph representation of the respective king pin loadings of various vehicle combinations according to the prior art and embodiments of the invention; and

Figure 6 is a side elevation of a dolly hitch arrangement of the embodiment shown in Fig. 1.

Referring now to the Fig. 1, prime mover 2 has steered wheels 4 beneath cab 6 and a pair of driver axles 8, 8' in conventional manner. A fifth wheel assembly 10 between the driver axles supports the forward end of a front trailer 12, 8560mm in length. The trailer 12 has tandem axles 14, 14' at its rear spaced at 1924mm. The latter spacing is economical and improved load distribution. The distance between axle 8' and axle 14 is 5053mm. Front trailer 12 articulates about the axis of the fifth wheel 10.

Rear trailer 16 is likewise 8560mm in length and has a tandem axle assembly 18, 18'. Again the spacing between the trailer axles is 1924mm. The forward end of the rear trailer is supported by a fifth wheel 20 borne by dolly frame 22. The tandem axle 24, 24' of the dolly frame are 1500mm apart. The dolly frame 22 has an Α-frame draw bar 26 which hitches to the rear of front trailer 12 via a RINGFEDER® coupling. The distance supporting the dolly frame 22 from the rear of trailer 12 is 3614mm which allows the dolly to articulate.

The fifth wheel 20 allows the trailer 16 to articulate. The combined effect of three axes of articulation is to reduce the turning circle to 21m diameter instead of the 23780mm which is the distance separating steered axle 4 and the rearmost axle 18'. General Mass Limit (GML) up to 68.5TN and Higher Mass Limit (HML) up to 74.5TN (currently).

The wheel axles are connected to the two trailer chassis and to the dolly frame by trailing arm suspension units incorporating air bags.

Conventional retractable legs 28 extend from both trailer chassis.

In a non-illustrated variant, axles, 14', 24' and 18' are fitted with self-steered wheels which allow caster action. This is possible by the use of truncated cone mounts for the wheels. Caster action only occurs at speeds up to 40kph in order to confine this assistance to steering to the part of the vehicle journey in the vicinity of the collection area at the farm. At cruising speed there is no caster action. The speed at which the axles are locked and unlocked is programmed by the EBS system provided with the trailer.

Referring now to the drawings, in Fig. 2a a conventional vehicle 30 made according to the prior art is shown having trailers 12,16 with supported by trailing group triplet wheel sets 40,80 that are fixed and non-steerable. Such wheel sets 40,80 operate well when the vehicle 2 is travelling in a relatively straight direction. However, the very nature of LCVs is that they are often required to be driven into tight spots with limited room for turning. In such situations, the middle set of wheels 46 in the wheel group set 40, tend to turn with little sideways force as they are located close to the pivot point 20 of the tag trailer 16 mount. However the front 42 and rear 44 wheel sets tend to drag sideways, causing road or ground infrastructure damage, and a high rate of tyre wear.

In Fig. 2, there is shown a 19m B Double 30a having a prime mover with a typical front set of steerable wheels rated to support 6.5T and a trailing tandem group set rated to bear a load of 17T. The front trailer is supported by a forecarriage 21a that has, at its rear, a tandem set of non-steerable wheels 40a, as does the rear tag trailer with the tandem set of wheels 80a, each tandem wheel set having a load supporting capacity of 17T. The total load bearing capacity of the vehicle 30a is therefore: 6.5 + 3 x 17T = 57.5T compared to 63.5T for the inventive equivalent vehicle 100 shown in Fig. 4 as described below. A vehicle 1 having a prime mover 2 is shown in Figs. 1 and 3, which vehicle 1 has steered wheels 4 beneath cab 6 and a pair of driver axles 8, 8' in conventional manner. A fifth wheel assembly 10 between the driver axles supports the forward end of a front trailer 12, 8560mm in length. The trailer 12 has tandem axles 14, 14' at its rear having an unusually large spacing of 1924mm. The latter spacing is economical and improves load distribution, reduces the horizontal forces to which the non-steered wheels might be subjected. The distance between axle 8' and axle 14 is 5053mm. Front trailer 12 articulates about the axis of the fifth wheel 10.

Rear trailer 16 is likewise 8560mm in length and has a tandem axle assembly 18, 18'. Again the spacing between the trailer axles is 1924mm. The forward end of the rear trailer is supported by a fifth wheel 20 borne by dolly frame 22. The tandem axles 24,24' of the dolly frame are 1500mm apart. The dolly frame 22 has an Α-frame draw bar 26 which hitches to the rear of front trailer 12 via a RINGFEDER® coupling. The distance from the king pin 25 at the rear of trailer 12 supporting the A-frame 26 to the front of the dolly frame 22 is 3614mm, which allows the dolly to articulate.

The fifth wheel 20 allows the trailer 16 to articulate. The combined effect of three axes of articulation is to reduce the turning circle to 21m diameter instead of the 23780mm which is the distance separating steered axle 4 and the rearmost axle 18'. The improved weight distribution of three tandem axle sets 14,18,24 over the prior art twin triplet combination enables the General Mass Limit (GML) to be up to 68.5TN and the Higher Mass Limit (HML) to be up to 74.5TN. In particular, the spaced apart wheel sets 8,8’; 24,24’; and 18,18’, each individually have a load rating of 10T, (currently 9T in the State of Victoria, Australia, but engineered to support 10T), so that the total load carrying capacity for vehicle 1 is 6.5 + 17 + 6 x 10T = 83.5T, compared to the equivalent prior art 25m B Double vehicle 30 represented in Fig. 2a of 6.5 + 17 (for the prime mover 6) + 21 + 21T (2IT for each of the tri-group sets 40,80) = 65.5T. This represents a significant load carrying advantage for the inventive vehicle 1 over its prior art equivalent vehicle 30.

The wheel axles of the wheel sets 14,14’,18,18’24,24’ are connected to the two trailer chassis 12,16 and to the dolly frame 22 by trailing arm suspension units incorporating air bags.

Conventional retractable legs may be provided to extend from the underside of both trailer chassis.

The axles of wheel sets 14', 24' and 18' are fitted with self-steered wheels which have a caster action whereby to trail the direction generally determined by the prime mover 6. This is effected by the use of truncated cone mounts 15 for the wheels with each wheel set joined by a horizontal tie rod 17\ Caster action only occurs in wheel sets 14', 24' and 18' at speeds of up to 40kph in order to confine this assistance to steering to the part of the vehicle journey requiring turns at slow speeds. At cruising speed (above 40kmph) the wheel sets 14’, 18,24’ are locked and there is no caster action. The speed at which the axles of the wheel sets 14’, 18’,24’ are locked and unlocked is programmed by an electronic braking system (EBS) provided with the trailer 12,16.

Another version of the vehicle combination of the invention is shown in Fig. 4 in the form of a 20m A-B Double 100 having a prime mover 106, hauling a first trailer 112 and a tag trailer 116. The first trailer is supported at its front end by a fifth wheel coupling 110 and a single fixed wheel set 114 at its rear end. The tag trailer 116 trails the rear end of the first trailer 112 by a ring feeder coupling 125. A forecarriage frame 122 supports the front end of the tag trailer 116 and is drawn by an Α-frame drawbar 126 in a manner similar to the A-frame drawbar 26 of the embodiment shown in Figs. 1 and 3. The front end of the tag trailer 116 is mounted on the forecarriage 122 for articulation by a fifth wheel coupling 120. The forecarriage 122 is supported by a wheel group set of widely spaced front 124 and rear 124’ wheel sets in a manner similar to the wheel sets 24,24’ shown in Figs. 1 and 3, their spacing being of the order of about 2.2m so that the wheel sets 124,124’ are rated as single axles with an engineered load capacity of 10T. The trailing wheel set 124’ in steerable at low speeds (less than 40kmph) to effectively mitigate sideways forces to which non-steerable wheels would be subjected when a vehicle made according to the prior art, such as a vehicle 30 shown in Fig. 2, is turning.

In the present embodiment 100, the front pair of wheels 124 follow the lead of the first trailer with limited sideways drag and the trailing wheel set 124’ is steered by a caster action so that there is little or no sideways drag by the trailing pair of wheels 124’. The rearmost wheel set 118 is fixed and trails effectively without steering.

The vehicle 100 advantageously comprises 4 wheel sets 114,124,124’, 118 on the trailers 112,116, that are well spaced (the distance between the paired wheel sets 124,124’ on which the dolly 122 is mounted being between about 1.9 - 2.0m) to better distribute the load. This wide base support and more dispersed distribution of load support is achievable by providing a steerable wheel set 124’.

With reference to Fig. 5, a modelling graph of a king pin 10,110 load of various LCV combinations is shown, including that for vehicles 1,30,100 as they travel through a 180° turn. A like for like comparative study may be made between prior art vehicle 30 and the preferred embodiment vehicle 1 which haul similar massed loads of about 60T. It can be seen that at the high load mid-point of the turn (around 30 - 40 seconds into a turn that takes about 40 - 50 seconds to complete), the king pin 10 load of the prior art vehicle 30 is about 3 times the loading on the king pin 10 of the preferred comparable vehicle 1, despite hauling similar loads. Accordingly, this demonstrates the large advantage of the preferred wider spacing of the wheel sets within each group set to permit improved load distribution and the steerability of the trailing wheel sets 14’,24’, 18’ have a direct effect on reducing the load applied to the king pin 10 when the vehicle 1 is turning.

Accordingly a A_B or A Double vehicle 1,100 is provided that subjects the king pin coupling 10,110 to a maximum load on a flat standard road surface of less than 1000kg.

In Fig. 6, the ring feeder arrangement 25 of the 26m B Double vehicle 1 is showing in greater detail. The position of the ring feeder 25 and particularly the vertical axle hitch point 27 is mounted to the front trailer 12 as far forward as possible towards the centre C of the axle group 14,14’ to greatly improve the dynamics of the dolly 22 connected to the ring feeder 25. The ring feeder coupling 25 is located within 300mm - 600mm (when considered in plan view) of the rear axle of wheel set 14’ of the first trailer 12, preferably about 500mm in distance, and most specifically in the embodiment shown, within about 520mm. The wheel sets 14,14’, axle to axle, are advantageously spaced between 1700 -2200mm of each other, preferably 1900 - 2000mm, and most specifically, about 1920mm of each other, so that the pair of wheel sets 14,14’ operate ostensibly as separate, single axles.

It is to be understood that various modifications of and/or additions to the invention can be made without departing from the basic nature of the invention. These modifications and/or additions are therefore considered to fall within the scope of the invention.

Throughout the specification and claims the word “comprise” and its derivatives are intended to have an inclusive rather than exclusive meaning unless the contrary is expressly stated or the context requires otherwise. That is, the word “comprise” and its derivatives will be taken to indicate the inclusion of not only the listed components, steps or features that it directly references, but also other components, steps or features not specifically listed, unless the contrary is expressly stated or the context requires otherwise.

In the present specification, terms such as “apparatus”, “means”, “device” and “member” may refer to singular or plural items and are terms intended to refer to a set of properties, functions or characteristics performed by one or more items or components having one or more parts. It is envisaged that where an “apparatus”, “means”, “device” or “member” or similar term is described as being a unitary object, then a functionally equivalent object having multiple components is considered to fall within the scope of the term, and similarly, where an “apparatus”, “assembly”, “means”, “device” or “member” is described as having multiple components, a functionally equivalent but unitary object is also considered to fall within the scope of the term, unless the contrary is expressly stated or the context requires otherwise.

Orientational terms used in the specification and claims such as vertical, horizontal, top, bottom, upper and lower are to be interpreted as relational and are based on the premise that the component, item, article, apparatus, device or instrument will usually be considered in a particular orientation, typically with the wheels 14,14’, etc. lowermost.

Claims (4)

1. A longer vehicle combination for road transport of bulk goods comprising a prime mover with a fifth wheel, a front trailer and a rear trailer, each having trailer axles, the trailer axles being arranged in tandem sets, the rear of the front trailer having a front tandem set, the rear trailer having a leading tandem set and a trailing tandem set, and the leading tandem set of the rear trailer being part of a dolly which supports a fifth wheel of the rear trailer, wherein the spacing between the trailer axles of each of the tandem sets is 1.5 - 2.1m, the front tanker trailer comprising a pin for coupling to the fifth wheel of the prime mover and tandem axles at the rear of the front trailer, the rear trailer comprising tandem axles at the rear of the rear trailer and comprising a pin for coupling to a fifth wheel of a dolly, the dolly comprising a frame supported by tandem axles and, in turn, supporting the fifth wheel of the dolly, an A-configuration draw bar extending forwardly of the frame for mutually connecting the front trailer to the rear trailer by the dolly frame which in turn is supported by tandem axle and the wheels of the trailing axle of each of the tandem sets are self-steering.

2. A longer vehicle configuration as claimed in Claim 1, wherein the rear axle of each of the tandem sets has a pair of self-steered wheels which have caster action to achieve a smaller swept path in turning the vehicle combination than the swept path of a traditional combination with no steered wheels on the dolly.

3. A longer vehicle configuration as claimed in Claim 1 or 2, wherein a front axle and the rear axle of the dolly are 1400-1600mm apart.

4. A longer vehicle configuration as claimed in any one of Claims 1-3, wherein the distance between a tow point of the front trailer to the centre of the fifth wheel supported by the dolly is 3000-4500mm.