GB2234217A - Front-facing rowing arrangement with linkage to accelerate blade - Google Patents

Abstract

A front-facing rowing arrangement for a boat includes a pair of oars each of which includes a handle 1 and a blade 3 mounted for pivotal movement about spaced parallel axes on a supporting member 5 which is itself hingely mounted for movement about a horizontal axis extending parallel to the direction of travel of the boat. The handle 1 and blade 3 of each oar are connected by a lever/linkage system which is such that the angular velocity of the blade relative to the angular velocity of the handle increases steadily throughout a notional 60 DEG power stroke. <IMAGE>

Description

APPARATUS FOR THE PROPULSION OF BOATS Field of the Invention This invention relates to apparatus for the propulsion of boats and is concerned with the provision of a new design of oars for use in rowing facing the direction of travel.

Background to the Invention As mentioned by Holm in Canadian Patent Specification No.

1172522, there have been many proposals for the provision of forward-facing rowing, the majority of which have been cumbersome, complicated or bizarre. Holm discloses an oar construction which includes overlapping inner and outer components pivotally connected to each other and a pivoting brace acting between a rear support post and the inner end of the outer oar component.

In British Patent Specification No. 342445 (Devienne) there is disclosed an oar arrangement for forward-facing rowing which comprises two coacting and separately pivoted members, one forming the handle and the other carrying a pivoted blade.

The handle and blade are interconnected in such way that, when the oar and handle are in line, the maximum relative blade velocity is obtained.

A further oar arrangement permitting forward-facing rowing is described in British Patent Specification No.

2056930A (Witchell). In this arrangement, each oar has an inboard and outboard section the ends of which come together pivotally at a common zone of attachment to the boat and are mechanically interconnected so as to promote an opposite movement of the inboard section to that of the outboard section, the interconnection being in the form of two arms or links each connected to an oar section and themselves coming together at a pivot moving within a fixed channel attached to the gunwhale of the boat.

Although the oar arrangements described in these earlier specifications permit forward-facing rowing, the rowing action is of limited efficiency. Other forward facing rowing arrangements are shown in British Specifications Nos. 283411 (Kruse), 319059 (Baxter), 1426652 (Bosmorin) and 2213119 (Deutschmann), and in US Patent SpecificationS Nos. 1381923 (Kemp) and 3729369 (Trull). Trull also discloses an automatic feathering arrangement. A gear arrangement for the provision of forward-facing rowing is shown in US Specification No. 3884175 (Bellis). These other arrangements are also of limited efficiency and, so far as the applicant is aware, have not been produced commercially.

It is accordingly an object of the present invention to provide a forward-facing oar arrangement which is more efficient than previous proposals.

Summary of the Invention The invention accordingly provides a forward-facing rowing arrangement which includes an oar handle and an oar blade interconnected by a lever/linkage system which is so arranged that the angular velocity of the blade is greater than the angular velocity of the handle during at least the final part of the power stroke and the acceleration ratio (as herein defined) is significantly greater than 1.

The term acceleration ratio as used herein is the ratio of the angular movement of the oar blade at a position approaching the end of a notional power stroke resulting from a given angular movement of the oar handle to the angular movement of the oar blade at the commencement of the power stroke resulting from the same given angular movement of the oar handle. The notional power stroke comprises a handle movement of 60 starting at a position 30 prior to its position at right angles to the intended direction of travel.

Thus if the relative velocity of the blade at the commencement of the power stroke has a value B, then the relative blade velocity at the end of the power stroke is significantly greater than B. For example, the acceleration ratio appropriate for a young or elderly rower may be between 1.7 and 2, whereas appropriate ratio for a trained athlete may be 2.7,3 or higher.

The oar blade and oar handle are preferably pivotally mounted on a supporting member for pivotal movement relative thereto about axes which are spaced apart in a direction which extends athwartships, i. e. at right angles to the intended direction of travel of the boat, the lever or linkage system being such that the axis of the oar handle extends athwartships at the mid-point of the power stroke.

The lever or linkage system interconnecting the oar handle and the oar blade preferably comprises crank arms on the oar handle and on the oar blade, which crank arms are of substantially equal length L and are interconnected by a link the length of which is significantly greater than L, being at most 2.7 L, but which preferably has a length of between 2 L and 2.5 L.

The interconnecting link may be adjustable in length, for example, it may include a turnbuckle, the acceleration ratio being increased by reducing the length of the link by means of the turnbuckle. The interconnecting link may be either a straight link or a cranked link, such cranking of the link, if provided, being such as to permit the oar blade to be moved into a position extending alongside the boat without the link coming into contact with the pivot axis for the oar blade.

In order to further increase the efficiency of the rowing action, an automatic feathering action is preferably provided, the feathering action being afforded by supporting the outer end portion of each blade on low-friction bushes, each blade outer end portion having a centre of gravity which is offset from the centre line of the oar such that, when the blade is in the air, it adopts a position generally parallel to the surface of the water whereas, when the blade is immersed in the water during the power stoke, it adopts a position perpendicular to its line of travel.

Brief Description of the Drawings Figure 1 is an isometric view of a first form of interconnection between an oar handle and an oar blade, Figure 2 is a plan view of the arrangement shown in Figure 1 fitted to a boat, Figure 3 is an end view of the boat shown in Figure 2, Figure 4 is a diagrammatic plan view of the blade and handle connection of Figure 1, Figure 5 is a diagrammatic plan view of a further form of blade and handle connection, Figure 6 is an isometric view of the blade and handle connection of Figure 5, including a detail to an enlarged scale of a joint between the links, and Figure 7 is an exploded perspective view of an end of an oar illustrating a preferred form of automatic feathering mechanism.

Description of the Preferred Embodiments Referring first to Figure 1, this shows an arrangement which includes an oar handle 1 which is mounted on a pivot pin 2 for rotation of the oar handle 1 about the axis of the pin 2.

The oar blade 3 is similarly mounted on a pivot pin 4, with both pivot pins 2 and 4 carried by a plate-like supporting member 5 to which is attached a hinge 6, the hinge 6 including a pair of pivotally connected yokes, one of which is attached to the supporting member 5 and the other of which is secured on or near the gunwhale of the boat with its centre line or hinge axis parallel to the centre line of the boat itself.

In an alternative arrangement, which may be adopted when the width of the boat is significantly less than that illustrated in Figure 2, the hinges 6 are carried by outriggers which extend outwardly of the sides of the boat and are appropriately braced to withstand the torsional loads to which the hinges are subjected during rowing.

When an outrigger arrangement is provided, the two outriggers may be interconnected to form a single structure which can then be built into the shell of the boat, this structure being provided, if desired, complete with the forward-facing oar construction of the invention. In addition, with such structure, a braced support for the pivot axes can be provided with such axes located, if desired, so that they do not project beyond the sides of the boat.

The handle 1 is provided at its inner end with a crank or lever arm la, and the blade 3 is similarly provided at its inner end with a crank or lever arm 3a. As illustrated, each of the two cranks or lever arms la and 3a is fabricated from two plates, the top plate being illustrated in each case in broken lines. The cranks or lever arms la and 3a move between the supporting member 5 and a cover plate, of similar dimensions to the supporting member 5, which is disposed above the supporting member 5 but has been omitted from Figure 1 for the sake of clarity.

Crank or lever arm la carries a pivot pin 8, and crank or lever arm 3a carries a pivot pin 9, the two pivot pins 8 and 9 being interconnected by a link 7. The lengths of the crank arms or levers la and 3a, i. e. the distances between pins 2 and 8 on the one hand and between pins 4 and 9 on the other hand, are equal or approximately equal, and of a length between approximately 6% of the handle length and approximately 15% of the handle length. The length of the link 7 is between 1 and 2.7 times the length of each crank arm. The preferred length of the link 7 is between 2 and 2.5 times the length of each crank arm. If desired, the link 7 may include a turnbuckle or other form of length adjuster to enable the length of the link 7 to be adjusted between the limits mentioned above. The relative proportions of the components interconnecting the handle 1 and the blade 3 are such as to provide a compact construction while at the same time enabling the components to be of adequate strength to withstand the stresses to which, in use, they are subjected.

The degree of angular movement of the oar blade 3 for a given angular movement of the oar handle 1 is illustrated in Figure 2, the arrow showing the directions of movement of the handle 1 and the blade 3 during the power or working stroke. As can be seen, the first 10 of movement of the handle 1 results in 10 of movement of the blade 3. There is thus an initial relative blade velocity of 1. The handle 1 is movable through a total arc of 60 , i. e. 30 either side of a position at right angles to the centre line of the boat and, during the final 10 of movement of the handle 1, the blade 3 moves through 20 , i. e. there is a relative blade velocity of 2.

The term"acceleration ratio"as used herein is the ratio of the angular travel of the blade 3 for the first 10 of handle movement to the angular travel of the blade 3 for the final 10 of handle movement. As can be seen from Figure 2, the acceleration ratio is, in this case, 2.

In a conventional rowing construction, the boat steadily accelerates during the power stroke, and then decelerates while the oars are being returned to start the next power stroke. In order to maintain an effective rowing action, the rower must accelerate his oar during his power stroke but, inevitably, he will relax his pull just before he reaches the end of the power stroke in readiness for withdrawing his oar and effecting the return stroke.

An important advantage of the present invention is thus that, as the relative blade velocity increases during the power stroke, and is at its maximum at the end of the power stroke, the oar blade can be caused to accelerate during the power stroke without a corresponding requirement for acceleration of the oar handle. A much smoother, more efficient rowing action is thus obtained.

The preferred acceleration ratio will depend on the age and strength or fitness of the rower. Thus, for a young boy or an elderly rower, the preferred acceleration ratio will be less than for a trained athlete, for whom the maximum preferred acceleration ratio may be greater than 3.

As can be seen from Figure 3, the length of the oar handle is typically one third of the total length of the oar, and the oar is pivotable about the hinge axis between the position shown in full lines, which it occupies during the power stroke, and the position shown in broken lines, into which it is moved for the return stroke.

The acceleration ratio may be chosen in dependence on the type of craft and on the characteristics of the intending rower. Consideration of Figure 4 enables the design parameters to be evaluated. For crank arms or levers la and 3a of a given length and for a given length of the link 7, different acceleration ratios will be obtained by varying the angles and. Different acceleration ratios are also obtained by varying the length of the link 7 or the spacing between the pivots 2 and 4. If a device is produced with the relative proportions shown in Figure 4, the acceleration ratio will be 2.08. The angle is calculated in this instance as 6i to ensure that, for a handle stroke of 60 as shown, the blade 3 begins and ends the power stroke at equal angular spacings from the athwartship condition.

Each crank arm or lever is shown in Figure 4 as having two positions at which the link 7 can be connected. If, therefore, the link 7 of Figure 4 were disconnected from positions 8 and 9 and was reconnected at positions 8a and 9a, the angles and would be changed and the acceleration ratio would be increased to 2.58. If the spacings between the two positions on each crank arm or lever for connection of the link 7 were less than that shown in Figure 4, a smaller change in the acceleration ratio would be obtained.

If the link 7 shown in Figure 4 is replaced by a link having a length 9% greater than the link 7 and this longer link is fitted so as to extend between positions 8 and 9a, the resulting structure will provide an acceleration ratio of 2.92.

It will be appreciated from a consideration of Figures 1 and 4 that, if a straight link 7 is used as shown, the link 7 will foul the pivot pins if the handle 1 is moved beyond the end of the normal power stroke towards a stowage position in which the blade 3 extends almost in the direction of travel of the boat. If, however, the straight link 7 is replaced by an appropriately shaped, cranked or curved link, provision can be made enabling the blade 3 to be moved into a stowed position.

With this arrangement, in order to assist in maintenance of the oar blades in the stowed or parked position, a cord may be provided for linking together the two oar blades.

An alternative form of interconnection between an oar handle 1 and an oar blade 3 is shown in Figures 5 and 6 to which reference should now be made. This embodiment is less compact than the embodiment of Figures 1 to 4 but can be produced from relatively light-weight components. An inner end portion of the handle 1 performs the function of the crank arm or lever la while an inner end portion of the blade 3 performs the function of the crank arm or lever 3a. The handle 1 and blade 3 have a common pivot mounting on a pin 2 carried by the hinge mechanism 6 so that there is no torque applied to the hinge.

During a power stroke, a primary link 10 is in compression and acts upon a secondary link 11 which is in tension. A swivel joint 13 (which is shown to an enlarged scale in the insert to Figure 6) connects the primary and secondary links 10 and 11 and is forced to travel in a roughly fore and aft line by a third or restraining link 12 whose inboard end is attached to a swivel 14 on the craft itself, or on a part of the rigger 15/16.

The lengths of the handle and blade portions la and 3a should be limited to about 25% of the length of the handle with the links 10 and 11 both having a length about 50% of the handle length. The link 12 can be of any suitable length provided that it does not impede movement of the rower. With a device having the relative proportions illustrated in Figure 5, the resulting acceleration ratio is 1.88.

As shown, link 11 in Figure 5 has a length which is 91% of the length of the link 10. If the length of link 10 is maintained constant and the length of link 11 is reduced to 84% of the length of link 10 (with corresponding adjustment of the length of link 12), then the acceleration ratio is increased to 2.43. If the length of link 11 is further reduced to 77% of that of link 10, the acceleration ratio is increased to 3.60.

Intermediate adjustments of the length of link 11 will, of course, result in corresponding intermediate adjustment of the acceleration ratio.

Turning next to Figure 7, this shows the manner whereby automatic feathering can be afforded. The outer end portion 16 of the oar blade 3 includes a curvate portion of conventional form and a cylindrical sleeve portion within which a pair of spaced low friction bearing bushes 17 and 18 are located. The two bushes 17 and 18 are of polytetrafluoroethylene or of some other low friction plastics material whereas the other oar blade components are of anodised aluminium, or other material which is suitable for marine applications.

The stem of the oar blade 3 terminates in a shaft 21 which fits within the sleeve of the blade end portion 16 so as to be supported by the first bearing bush 17, the shaft 21 being held in position within the sleeve by means of a stainless steel pin 19. A stainless steel washer 20 is located between the head of the pin 19 and bearing bush 18 which supports an unthreaded portion of the stem of the pin 19. After assembly, the hole in the blade over the head of the pin 19 may be closed by means of a removable plug (not shown).

The curvate portion of the blade end portion 16 has a centre of gravity which is offset from the centre line of the oar. The easy sliding fits between the bush 17 and the shaft 21, and between the threaded pin 19 and the bush 18 thus ensure that, in still air, the blade end portion 16 adopts the feathered position in which it extends generally parallel to the surface of the water.

When, however, the blade end portion is immersed in the water, as it is during the power stroke, any movement of the blade results in it adopting a position perpendicular to its line of travel. For exposed sea conditions or in otherwise gusty conditions, it may be desirable to further weight the blade end portion 16 to ensure that it feathers positively.

Figure 2 shows one way in which the angular movements of the oar blade 3 may be related to the angular movements of the oar handle 1, i. e. for six successive angular movements of 10 for the oar handle 1, the oar blade moves through 10 , 10 po, 11 , 13 , 16 and 20 . There is thus a steady increase of the relative blade velocity, i. e. of the velocity of the blade 3 relative to the handle 1, throughout the whole of the normal 60 movement of the handle 1 which constitutes a notional power stroke.

This means that, if the oar handle 1 is moved at a constant angular velocity, the oar blade 3 will be moved at a steadily increasing angular velocity, i. e. that the blade 3 will be caused to accelerate throughout the power stroke, the acceleration ratio in this case being 2. Appropriate adjustment of the relative lengths of the connecting link and the lever arms enables this acceleration ratio to be adjusted as required while maintaining a relationship in which the relative blade velocity increases throughout the power stroke.

This steady increase in the relative blade velocity ensures that an efficient rowing action is obtained. If, therefore, the oar handle is moved at a constant rate throughout the power stroke, which should be the case for a proficient rower, the oar blade will accelerate throughout the power stroke and will achieve its maximum velocity at the end of the power stroke.

Claims (12)

CLAIMS:

1. A forward-facing rowing arrangement for a boat which includes an oar handle and an oar blade interconnected by a lever/linkage system which is so arranged that the angular velocity of the blade is greater than the angular velocity of the handle during at least the final part of the power stroke and the acceleration ratio is significantly greater than 1, said acceleration ratio being the ratio of the angular movement of the oar blade at a position approaching the end of a notional 60 power stroke resulting from a given angular movement of the oar handle to the angular movement of the oar blade at the commencement of the power stroke resulting from the same given angular movement of the oar handle.

2. A rowing arrangement according to Claim 1, in which the oar blade and oar handle are pivotally supported on a supporting member for pivotal movement relative thereto about spaced parallel axes and in which the lever/linkage system is such that the axis of the oar handle extends athwartships at the mid-point of the power stroke.

3. A rowing arrangement according to Claim 1, in which said acceleration ratio is at least 1.7.

4. A rowing arrangement according to Claim 3, in which said acceleration ratio is adjustable.

5. A rowing arrangement according to Claim 1, in which the lever/linkage system comprises lever arms rigidly attached to the oar handle and to the oar blade, said lever arms being in the form of cranks which are inclined relative to the axes of the oar handle and the oar blade respectively, and a link interconnecting the free ends of the lever arms.

6. A rowing arrangement according to Claim 5, in which the two lever arms are of substantially equal length and the link interconnecting the lever arms has a length at least equal to twice that of one of said lever arms.

7. A rowing arrangement according to Claim 1, in which the outer end portion of the oar blade is supported on low friction bushes and has a centre of gravity offset from the centre line of the oar such that, when the blade is in the air, it exhibits a feathering action.

8. A boat having a front-facing rowing arrangement comprising a pair of oars each of which includes an oar handle, an oar blade and a supporting member hingedly mounted for movement relative to the boat about a generally horizontal axis, the oar handle and the oar blade of each oar being pivotally mounted on the associated supporting member for pivotal movement relative thereto about spaced generally vertical axes, the adjacent ends of each oar handle and blade comprising fixed crank arms which function as levers and have a substantially equal length, and a link interconnecting the free ends of the crank arms of each oar, each link having a length at least equal to twice the length of the associated crank arms and the lever system afforded by each link and its associated crank arms being such that, during rowing, the relative blade velocity increases during at least the final part of the power stroke, the acceleration ratio afforded by said lever system being significantly greater than 1, said acceleration ratio being the ratio of the angular movement of the oar blade at a position approaching the end of a notional 60 power stroke resulting from a given angular movement of the oar handle to the angular movement of the oar blade at the commencement of the power stroke resulting from the same given angular movement of the oar handle.

9. A boat having a front-facing oar arrangement comprising a pair of oars each of which includes an oar handle, an oar blade and a supporting member hingedly mounted for movement relative to the boat about a generally horizontal axis extending generally parallel to the intended direction of travel of the boat, the oar handle and the oar blade of each oar being pivotally mounted on the associated supporting member for pivotal movement relative thereto about spaced parallel axes, each oar blade being connected to its respective oar handle by a lever/linkage system such that, if the handle is moved at a uniform rate, the blade will accelerate relative to the handle throughout the power stroke.

10. A boat having a front-facing oar arrangement comprising a pair of oars each of which includes an oar handle, an oar blade and a supporting member hingedly mounted for movement relative to the boat about a generally horizontal axis extending generally parallel to the intended direction of travel of the boat, the oar handle and the oar blade of each oar being pivotally mounted on the associated supporting member for pivotal movement relative thereto about spaced parallel axes, each oar blade being connected to its respective oar handle by a lever/linkage system such that the angular velocity of the blade relative to the angular velocity of the handle increases throughout a notional 60 power stroke and such that the acceleration ratio is significantly greater than 1, said acceleration ratio being the ratio of the angular movement of the oar blade at a position approaching the end of said 60 power stroke resulting from a given angular movement of the oar handle to the angular movement of the oar blade at the commencement of said power stroke resulting from the same given angular movement of the oar handle.

11. A boat having a front-facing oar arrangement, or a front-facing oar arrangement for a boat, substantially as hereinbefore described with reference to and as shown in Figures 1 to 6 of the accompanying drawings.

12. A boat or oar arrangement as claimed in Claim 11, which includes an automatic feathering means substantially as hereinbefore described with reference to and as shown in Figure 7 of the accompanying drawings.