GB2449889A

GB2449889A - An outboard motor steering system

Info

Publication number: GB2449889A
Application number: GB0710870A
Authority: GB
Inventors: Simon Mcloughlin; Andrew Mcloughlin
Original assignee: Makmarine Ltd
Current assignee: Makmarine Ltd
Priority date: 2007-06-06
Filing date: 2007-06-06
Publication date: 2008-12-10
Also published as: GB0710870D0

Abstract

The present invention provides an outboard motor steering system 10 for a transom mounted outboard motor (34, Fig 2) of a watercraft. The steering system includes a member 42 which is slidably mounted to the engine bracket 30 of an outboard motor, and a steering arm 44 mounted to the member and, in use, connectable to the outboard motor. The slidably mounted member is slidable along a movement axis substantially perpendicular to the steering axis of the outboard motor in either of a direction to port or to starboard of the watercraft. The slidable member is provided at opposing ends thereof with connection means 62 to connect the slidable member to a steering input device 12 of a watercraft. The steering input device may comprise a steering member in the form of handlebars 22 and a force transmission means in the form of a disc 24 connected to the handlebars and a pair of cables 18 and 20 connected between the disc and the connection means.

Description

Steering System The present invention relates to a steering system for

a watercraft having a transom mounted outboard motor.

An outboard motor is a propulsion and steering unit which is mountable to the transom of a watercraft. The unit may typically comprise an engine and a gearbox which are arranged to drive a propeller. The propeller is mounted at the end of a transmission leg which extends from the engine and, in use, projects into the body of water upon which the watercraft is supported. The outboard motor is movable about a steering axis so as to direct the thrust from the propeller in a desired direction to effect steering of the watercraft when propelled by the motor. The outboard motor may also be pivoted relative to the transom about a lifting axis to lift the transmission leg and propeller out of the water. The motor may also be moved about the lifting axis to change the trim the watercraft.

Movement of the outboard motor about the steering axis may be effected manually by the manipulation of a tiller of the motor. This type of steering is suitable for relatively small watercraft having less powerftil outboard motors, and requires an operator to sit adjacent the motor at the stem of the watercraft. Larger watercraft with more powerful outboard motors are typically provided with a remote steering input means, such as a wheel, which is connected to the motor by an appropriate linkage.

The linkage may typically comprise a single push-pull steering cable which is coupled between a steering box driven by the steering wheel and the outboard motor. This system is common place on boats with outboard motors up to approximately 100 Horsepower and has proven very reliable over many years. A drawback of this type of system is that it suffers from excessive amounts of play and gives an imprecise feeling on the helm.

Alternatively, the linkage may comprise a hydraulic system having a cylinder connected directly to the outboard motor and a steering wheel coupled to a steering box which pumps hydraulic fluid into the circuit. Linkages of this sort typically have a gear ratio which is very low and hence provides steering with a very lightweight feel. A drawback of this type of system is that typically multiple complete turns of the steering wheel are required to turn the engine lock to lock. Also, the hydraulic circuit can leak and lead to a possible pollution issue. The hydraulic system of the type described above may be augmented by the addition of a pump to move higher loads, hence control for higher power engines. Such systems offer solutions to larger watercraft. The pump however increases the overall weight of the system.

According to the present invention there is provided an outboard motor steering system for a transom mounted outboard motor of a watercraft, the steering system including a member which is slidably mounted to the engine bracket of an outboard motor, and a steering arm mounted to the member and, in use, connectable to the outboard motor, said member being slidable along a movement axis substantially perpendicular to the steering axis of the outboard motor in either of a direction to port or to starboard of the watercraft, the slidable member being provided at opposing ends thereof with connection means to connect the slidable member to a steering input device of a watercraft.

In a preferred embodiment, the slidable member is mounted to the engine bracket such that the movement axis is coaxial with a pivot axis of the engine bracket relative to the transom of the watercraft. The slidable member may preferably take the form of a rod or bar of substantially uniform cross-sectional dimensions over it's length.

The steering arm may be substantially "L" shaped and have a first arm portion which is pivotably connected to the slidable member, and a second arm portion which is connectable to the outboard motor. The second arm portion may be longer than the first arm portion. The steering arm is preferably connected to an end of the slidable member.

The steering system preferably further includes a steering input device having a steering member to which an operator of the watercraft can make steering inputs and a force transmission means extending from the steering member to the slidable member. The steering member is graspable by the operator and is preferably mounted for rotation about a steering input axis. The steering member may be a handlebar. The force transmission means may comprise a pair of cables, each of which has a first end connected to the steering member and a second end connected to the slidable member.

The first end of each cable is preferably mounted to a disc or drum which in turn is connected to the steering member and is rotatable about the steering input axis. The 1 0 cables are preferably mounted to the disc or drum in a maimer such that rotation of the steering input device in a first direction about the steering input axis causes one of the cables to be wound onto the disc and the other of the cables to be wound off of the disc.

Rotation of the steering input device in the opposite direction causes the cables to be manipulated in an opposite manner.

The second ends of the cables are preferably connected to the slidable member such that clockwise rotation of the steering input device results in movement of the slidable member in a portwise direction, and counter clockwise rotation of the steering input device results in movement of the slidable member in a starboardwise direction.

An embodiment of the present invention will now be described with reference to the accompanying drawings in which: Figure 1 shows a top plan view of an outboard motor steering system according to the present invention; Figure 2 shows a side view of the steering system of figure 1; Figure 3 shows a perspective view from above and to one side of a steering input device of the steering system; Figure 4 shows a perspective view from above and to one side of the engine bracket of the steering system of figure 1; and Figure 5 shows a perspective view of the steering input device having an optional steering damper.

V

Referring to the figures there is shown a steering system, generally designated 10, for a watercraft having an outboard motor. For the sake of simplicity the hull of the watercraft and the outboard motor are not shown. The steering system 10 includes a steering input arrangement 12, an engine bracket 14 and a steering linkage 16. The steering input arrangement 12 is connected to the steering linkage 16 by port and starboard bowden cables 18,20.

The steering input arrangement 12 comprises a handle bar 22 to which is connected a steering disc 24. The handle bar 22 and the steering disc 24 are mounted to the watercraft and are rotatable about a steering input axis 26. The engine bracket 14 is mounted to the transom of the watercraft and in turn carries the outboard motor (shown in outline 34 in figure 2). The engine bracket 14 comprises two substantially "L" shaped arms 28 which are joined by a plate member 30. A portion 32 of each arm 28 projects from the plate member 30 in a forward direction and is pivotably mounted to the transom of the watercraft. In use, the outboard motor 34 is mounted to the engine bracket 14. The engine bracket 14 and outboard motor 34 may be pivoted relative to the transom, as indicated by arrow 40 about a lifting axis 36 passing through said forwardly projecting portions 32 of the engine bracket arms 28. The outboard motor 34 is pivotable relative to the engine bracket 14 about a steering axis 38 as indicated by arrow 42 to effect steering of the watercraft by directing the thrust from the propeller of the outboard motor 34.

The steering linkage 16 is mounted to the engine bracket 14 and includes a slider bar 42 and a steering arm 44. The slider bar 42 is slidably mounted to aligned apertures 46 of the forwardly projecting portions 32 of the engine bracket arms 28. The slider bar 42 is thus slidable relative to the engine bracket 14 as indicated by arrow 48 in a dircction which is coaxial with the lifting axis 36 of the engine bracket 14. The steering arm 44 is substantially "L" shaped having a longer arm portion 50 and a shorter arm portion 52.

The steering arm 44 is pivotably mounted to the slider bar 42 at one end thereof. In the embodiment shown, the steering arm 44 is mounted to the port end 54 of the slider bar 42, however this configuration is not limiting and the steering arm 44 may alternatively

V

be mounted to the starboard end 56 of the slider bar 42. The shorter arm portion 52 of the steering ann 44 is pivotably mounted to the slider bar 42 by extending through an aperture provided in the end 54 of the slider bar 42. As can be seen from figure 4, the longer aim portion 50 of the steering arm 44 above the slider bar 42 and lies substantially parallel to the slider bar 42. It will be appreciated that movement of the slider bar 42 as indicated by arrow 48 results in corresponding movement of the steering arm 44 as indicated by arrow 60. In use, the free end 58 of the steering arm is connected to the outboard motor 34.

The respective port and starboard ends 54,56 of the slider bar 42 are provided with connectors 62 which enable ends 64 of the bowden cables 18,20 to be connected there to. In the embodiment shown, the port end connector 62 is defined by the end 66 of the shorter arm portion 52 of the steering arm 44 which extends through the slider bar 42.

The starboard end connector 62 is defined by a downwardly projecting member mounted to slider bar 42.

The bowden cables 18,20 extend between the steering disc 24 and the slider bar 42.

Each cable has a forward end which is connected to the disc 24 and a rearward end 64 which is connected to the slider bar. The cables 18,20 extend rearwardly from the steering disc 24 in a substantially parallel arrangement towards the rear of the watercraft. At or near the engine bracket 14 the cables 1 8,20 cross over one another such that the rearward end 68 of the starboard cable 20 connects via the port end connector 62 to the port end 54 of the slider bar 42, while the rearward end 64 of the port cable 18 connects via the starboard end connector 62 to the starboard end 56 of the slider bar 42. The sheaths of the bowden cables 18,20 are secured in an appropriate manner for example to brackets mounted to the transom.

Operation of the steering system 10 will now be described with reference to figure 1.

As a starting point it is assumed that the watercraft to which the system 10 is fitted is travelling in a straight line as indicated by arrow 70 under the influence of the outboard motor 34. The thrust supplied by the propeller of the outboard motor 34 acts in a direction indicted by arrow 72. In order to effect a turn to port, the operator of the watercraft makes a steering input to the steering input arrangement 12 by turning the handle bar 22 about the steering input axis 26 in a counter clockwise direction indicated by arrow 74. This steering input in turn results in counter clockwise rotation of the steering disc 24 and causes the forward end of the starboard bowden cable 20 to wind around the steering disc 24 and the remainder of the cable 20 to be drawn through its sheath in a forwards direction as indicated by arrow 76.

The rearward end of the starboard howden cable 20 acts upon the port end 54 of the slider bar 42 with the result that the slider bar 42 moves relative to the engine bracket 14 in a starboard direction indicated by arrow 78. The steering arm 44 is also moved in starboard direction as indicated by arrow 80 with the result that the outboard motor 34 pivots in a clockwise direction about its steering axis 38 as indicated by arrow 82. The direction of thrust provided by the outboard motor changes as indicated by arrow 84 with the result that the watercraft turns to port as indicated by arrow 86.

It will be understood that the starboardwise movement 78 of the slider bar 42 and counterclockwise rotation of the steering disc 24 results in reanvard movement of the port bowden cable 18 as indicated by arrow 88. By virtue of being connected to the starboard end 56 of the slider bar 42, the rearward end 64 of the port bowden cable 18 is able to act upon the slider bar 42 to move it in a portwise direction when the watercraft operator moves the handlebar 22 in a clockwise direction.

The present invention provides a handlebar steering for a watercraft which exhibits a levels of precision, agility and control that far exceed those of a conventional steering wheel helm. The twin cable embodiment described above provides very direct steering with no discemable backlash or play.

It is envisaged that the steering system described above may be modified so as to include a power assistance system. It will be appreciated that such a system may be provided to reduce the required input load on the helm. In one embodiment the assistance may be provided at the helm with actuators hydraulically or electrically powered driving directly onto the steering input axis 26 or the steering disc 24. The actuators may be hydraulically or electrically powered. Alternatively, the power assistance may be provided at the outboard motor. In such an embodiment the assistance may be provided by means of either hydraulically or electrically powered actuators driving directly onto the slider bar 42 or the outboard motor 34, In both embodiments it will be appreciated that power assistance system may be sensitive to a plurality operating parameters of the watercraft including, for example, steering angle, helm input load and craft speed to name but three.

A further modification of the above described steering system may comprise the provision of twin steering arms. The addition of a second steering arm would minimize the possibility of flexing between the outboard motor and the steering system during high load manoeuvres. The additional arm would mirror the existing steering arm 44 to provide system symmetry and balance. The pair of steering arms would connect to the outboard motor from opposite ends 54, 56 of the slider bar 42.

Referring now to figure 5 there is shown a steering input arrangement 12 having a steering damper generally designated 90. Features common to the aforementioned embodiment are identified with like reference numerals. The steering damper 90 comprises an extensible and compressible cylinder or strut 92 which is mounted between the steering disc 24 and a mounting point (not shown) on the hull or other structure of the watercraft. The strut 92 is pivotably mounted to an eccentrically positioned projection 94 on the underside of the steering disc 24. The projection 94 is provided substantially at the 12 o'clock position of the disc 24, while the opposing mounting point is aligned with the 6 o'clock position of the disc 24. It will thus be appreciated that the strut 92 is provided at its maximum extension when there is no steering input to the steering input arrangement 12 as shown in figure 5, and that rotation of the disc 24 in either the clockwise or counter clockwise direction results in compression of the strut 92.

The strut 92 may be of the passive type wherein a resistive force is applied to both extensive and compressive movement of the strut 92. It will be thus understood that a strut 92 of this type will operate in a similar manner to that of a motor cycle steering damper by providing resistance to steering inputs but not itself being able to provide a steering input. Alternatively, the strut 92 may be of the gas strut type whereupon it provides a resistive force to compressive movement of the strut 92, but is urged towards an extended position. It such an embodiment, the strut 92 would provide a self centering function for the steering input device 12 by urging it back to the straight ahead position.

Claims

Claims I. An outboard motor steering system for a transom mounted

outboard motor of a watercraft, the steering system including a member which is slidably mounted to the engine bracket of an outboard motor, and a steering arm mounted to the member and, in use, connectable to the outboard motor, said member being slidable along a movement axis substantially perpendicular to the steering axis of the outboard motor in either of a direction to port or to starboard of the watercraft, the slidable member being provided at opposing ends thereof with connection means to connect the slidable member to a steering input device of a watercraft.
2. A steering system as claimed in claim I wherein the slidable member is mounted to the engine bracket such that the movement axis is coaxial with a pivot axis of the engine bracket relative to the transom of the watercraft.
3. A steering system as claimed in claim 1 or claim 2 wherein the slidable member is a rod or bar of substantially uniform cross-sectional dimensions over it's length.
4. A steering system as claimed in any of claims I to 3 wherein the steering arm is substantially "L" shaped and has a first arm portion which is pivotably connected to the slidable member, and a second arm portion which is connectable to the outboard motor.
5. A steering system as claimed in claim 4 wherein the second arm portion is longer than the first arm portion.
6. A steering system as claimed in any preceding claim wherein the steering arm is connected to an end of the slidable member.
7. A steering system as claimed in any preceding claim wherein the steering system includes a steering input device having a steering member to which an operator l0 of the watercraft can make steering inputs and a force transmission means extending from the steering member to the slidable member.
8. A steering system as claimed in claim 7 wherein the steering member is a handlebar.
9. A steering system as claimed in claim 7 or claim 8 wherein the force transmission means comprise a pair of cables, each of which has a first end connected to the steering member and a second end connected to the slidable member.
10. A steering system as claimed in claim 9 wherein the first end of each cable is mounted to a disc which in turn is connected to the steering member and is rotatable about the steering input axis.
11. A steering system as claimed in claim 10 wherein the cables are mounted to the disc or drum in a manner such that rotation of the steering input device in a first direction about the steering input axis causes one of the cables to be wound onto the disc and the other of the cables to be wound off of the disc.
12. A steering system as claimed in claim 10 or claim 11 wherein the second ends of the cables are connected to the slidable member such that clockwise rotation of the steering input device results in movement of the slidable member in a portwise direction, and counter clockwise rotation of the steering input device results in movement of the slidable member in a starboardwjse direction.
13. A steering system as claimed in any of claims 10 to 12, wherein a damper arrangement is provided between the disc and a mounting point on the watercraft.
14. A steering system as claimed in any of claims 7 to 13 wherein the steering system includes power assistance which is arranged to act upon the steering input device.
15. A steering system as claimed in any preceding claim and including an additional steering arm wherein said arms are connected to opposing ends of the slidable member.

15. A steering system as claimed in any of claims 1 to 13 wherein the steering system includes power assistance which is arranged to act upon the slidable member.