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| | HYDRAULIC STEERING SYSTEMS | |
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| | How to determine the correct VETUS hydraulic steering? | |
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| | THE NUMBER OF STEERING WHEEL REVOLUTIONS When a reduced number of steering wheel revolutions from starboard to port is required, a steering pump with larger capacity should be selected. It should be taken into account that the force to be applied to the steering wheel becomes relatively greater, possibly leading to the necessity of selecting a larger diameter steering wheel. To the cylinder a pump unit must be applied (two pump units in case of a dual hydraulic steering), in conformity with the required number of steering wheel revolutions from port to starboard. It is the hydraulic cylinder which determines the torque of a hydraulic steering system. As already stated, the cylinder determines the torque. The choice of the correct cylinder is determined by the rudder torque in Nm (or kgm). The rudder torque is the determining factor (Torque = force x lever). To ascertain the correct rudder torque, only the maximum speed of the vessel, the surface area of the rudder blade and the maximum rudder angle (in degrees) are of importance. Information such as length of boat suppliers and engine power are irrelevant. With a few admitted exceptions, the rudder performs best with a maximum rudder angle of 35° to either side. Contrary to what is sometimes claimed for rudders with the "usual" dimensions, a larger rudder angle | does not enhance the manoeuvring capabilities of a vessel. The formula to determine the rudder torque reads: M (torque) = F x b (per rudder) In other words: the force F, which is applied to the rudder (given in Newton = N), is being multiplied by the lever "b", being the distance between the centerline of the rudder stock and the centre of pressure which lies on the line X-Y. l*- AS_ | A rudder with balance section calls for the formula: b = (0.37 x c) - e (in metres). Calculation example of one rudder with balance section the maximum speed of the boat is 16 km/hour (v); the total width of the rudder blade is 57 cm (c); the width of the balance section is 9 cm (e); the height of the rudder blade is 100 cm (h). F = 23.3 x 0.57 x 1.00 x 162 = 3400 N (340 kgf) b = (0.37 x 0.57) - 0.09 = 0.12 m. Therefore, the rudder torque amounts to 3400 x 0.12 = 408 Nm (41 kgm). So, the VETUS hydraulic steering to be selected in this case is model MTC52. With a twin rudder installation, the required torque is 2 x 408 Nm = 816 Nm, which makes model MTC125 the one to choose. We recommend that you consult VETUS for an accurate calculation. We also calculate the effects of the propeller manufacturer wash, as well as the torque when going astern. Because smaller vessels tend to respond quite sharply to the rudder commands, the maximum rudder torque is not used and a reduction of 10 to 20% off the calculated maximum torque is quite acceptable most of the time, especially if the boat is not sailed in heavy weather. Careful: some other manufacturers of hydraulic steerings have already taken such reduction into account when stating their capacity (torque). We, at VETUS, are of the opinion however, that the choice of whether or not such reduction should be applied, is exclusively the option of the naval architect. | |
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| | Rudder without balance section Rudder with balance section F (the force applied to the central line XY) - taking into consideration a maximum rudder angle of 2 x 35° - is constituted in the following manner: F = 23.3 x a x v2 in Newton (N), or: F = 2.33 x A x v2 in kgf. A = total surface area of rudder blade in m2. v = speed in km/hour. A rudder without balance section requires the formula: b = 0.37 x c (in metres); | |
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| | NYLON HOSE Nylon hose 0 6 x 8 mm, for cylinder MTC30, in rolls of 15 or 100 metres. | NON-RETURN VALVE The picture shows the separate dual non-return valve. In the case of a dual station system, a separate dual non-return valve or two single built-in non-return valves are required, in order to switch over automatically from one position to the other. | |
| | Nylon hose 0 6 x 10 mm, for cylinders MTC52 - MTC175 in rolls of 1 5, 30, 50 and 100 metres. Nylon hose 0 8 x 12 mm, for cylinders MTC52 - MTC175 in rolls of 1 5, 30, 50 and 100 metres. | |
| | BY-PASS VALVE If, in an emergency, a quick change-over to tiller steering is required installation of a by-pass valve is necessary. | | |
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| | EMBELLISH YOUR STEERING PUMP, MODEL HTP - HTP..R | HYDRAULIC STEERING SYSTEM FOR TRANSOM HUNG RUDDERS ~ MTC7210SL Stroke: 225 mm Volume: 146 cm3 Length of rudder arm: 196 mm Weight: 3 kg. | |
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| | This polished stainless steel flange can be used to fit a pump type HTP to replace an older type MTP pump. It can also be used as a simple embellishment. Flange type HTPF will recess the pump by 38 mm. Flange type HTPF2 will recess the pump by 74 mm. Both flanges come complete with a set of 4 stainless steel bolts, washers and nuts. | For other details see MTC 72, page 45. | |
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| | VETUS TELESCOPIC STEERING WHEEL ADJUSTER For all hydraulic steering pumps, type HTP and HTPR, a telescopic steering wheel adjuster is available. This adjuster unit is fitted onto the steering pump and will greatly enhance the helmsman's steering comfort, both seated and standing. Maximum travel is 90 mm adjustable in 3 steps of 30 mm. The adjuster unit is made of stainless steel AISI 316, with the visible parts high-gloss polished. Slide components are made of synthetic materials. The adjustment unit may be fitted internally at any angle between horizontal or vertical. For external applications, it should only be fitted horizontally. The correct steering pump should be ordered separately and must be connected with flexible hydraulic hoses, such as VETUS hose type HHOSE. Weight of adjuster unit: 4,6 kg. For situations where this wheel adjuster may fill with water, a sealing set is available. This consists of a rubber seal and a stainless steel trim ring. | | |
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