Drawings of the jet propulsion and motor installation of the boat «Moray»
Water jet boat «Moray» (ending, beginning see here)
The boat provides for the installation of a single-stage water jet propulsion. Its main parts are: a water intake with a protective grille at the inlet and a flange for attaching the propulsion to the transom of the boat; a four-bladed rotor having a disk ratio A/Ad=0.8, diameter 189 and pitch 190 mm; a nozzle with a straightening device mounted in it; a reversible steering device and a propeller shaft with bearings and a deadwood seal.
Jet propulsion of the boat «Moray»
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1 — propeller shaft; 2 — deadwood bearing housing cover; 3 — oil seal Ø20x42x11; 4 — nut M8, 10 pcs.; 5 — washer 8, 10 pcs.; 6 — gasket; 7 — bearing No.46205; 8 — oil press; 9 — oil seal Ø25x47x11, 2 pcs.; 10 — deadwood bearing housing; 11 — water intake; 12 — inspection hatch housing; 13 — lamb nut M10, 2 pcs.; 14 — hatch cover; metal, foam, fiberglass; 15 — stator (ring with flange); 16 — bolt M8x70, 6 pcs.; 17 — cotter pin 2,5x45; 18 — fairing nut; 19 — reverse steering device; 20 — rubber-metal bearing; 21 — M4x12 screw; 22 — M24x1 nut; 23 — locking washer; 24 — nozzle — straightening apparatus; 25 — rotor; 26 — key B 8x50; steel 2x13; 27 — filler — foam; 28 — molding, fiberglass; 29 — screw M6x12, 8 pcs.; 30 — 3x18 protective grid strip; 31 — 4x20x150 strip, 2 pcs.; 32 — fitting — water intake of the engine cooling system; 33 — rotor ventilation fitting; 34, 35 — flanges; 36 — hub of the straightening apparatus; 37 — blade of the straightening apparatus; 38 — nozzle of the reversing steering device; 39 — stud M8x24; 40 — fairing.
The water intake is a pipe of a rather complex configuration. Its end, adjacent to the bottom, has a rectangular cross-section, which gradually turns into a cylinder at the location of the rotor. If the boat's hull is constructed of fiberglass, it makes sense to make a water intake also of plastic and mold its lower edge directly to the bottom of the hull. This does not require metal fasteners.
The rotor rotates in a stator — a steel ring, which ensures the necessary wear resistance of the inner surface of the water cannon and the accuracy of its assembly. It is with the manufacture of this ring and the flange welded to it that work should begin. It is desirable to use stainless steel for the metal parts of the propulsor; the use of dissimilar metals should be avoided if possible to prevent corrosion.
The final treatment of the inner surface of the ring with a diameter of 190 mm and the groove of the centering belt for assembly with the guide device must be performed after welding the flange. On the surface of the shell, to which the fiberglass water intake will be molded, it is necessary to cut grooves about a millimeter deep for more reliable adhesion of metal with plastic. It is desirable to polish the inner surface of the ring washed with water to reduce friction losses.
For forming the water intake, it is necessary to make a «dummy» mold, which exactly copies the inner surface of the nozzle and provides interface with parts that are sealed in plastic. The theoretical drawing of the water intake is given here. After the fiberglass has cured, the block has to be removed from the water intake, which must be taken into account. The easiest way is to make it out of small pieces of foam, connecting them together with a «point» bonding with an epoxy binder.
Dummy for forming the water intake
1 — a cylindrical part with a diameter of 190 mm for fitting the stator ring; 2 — a plate in the DP; 3 — a template for controlling the outer surface of the blockhead; 4 — a base plate cut along the contour of the hole in the bottom; 5 — plywood.
On a thin foam plate with a size of 600x250 mm, you need to draw the contour of the water intake in the DP. Having cut the plate along this contour, two parts of the base, processed along the contour of the bottom hole, are glued to it from the sides. Then two halves of a disk with a diameter of 190 mm are glued to the vertical plate, forming the cylindrical end of the branch pipe, which can be fitted with a stator ring. It remains to fill the space between these plates with pieces of foam and process them, controlling the surface using cross-section templates cut from plywood. The final treatment is carried out with a skin, then the surface is putty, re-treated with a skin and painted. Along the contour of the inlet, the water intake should have a flange 20-25 mm wide for molding to the bottom, so the dummy should be placed on a base of thick plywood.
Next, you need to prepare the embedded parts — the body of the inspection hatch, the body of the deadwood bearing, the air fitting and the bars for fixing the grille. The required accuracy of mounting the shaft line is provided by means of a «false» shaft and a centering disk combined with the outer hole of the stator. Having passed the shaft through the hole drilled in the block, the body of the deadwood bearing is put on its inner end or, if the thrust bearing is mounted in the gearbox of the engine, a branch pipe for fixing the oil seal. The second option is preferable, since there is no need for precise alignment of the shaft line within the water jet propulsion. Tightening the nuts at the ends of the false shaft, fix the centering disc and the bearing housing on the block.
At the entrance part of the water intake, strips of rubber with a thickness of 4 mm are attached to the block, so that on the inner surface of the water intake there is a recess for the plates to which the protective grate is screwed.
The surface of the block is covered with a separating layer (wax diluted in turpentine, mastic for rubbing parquet floors, vaseline, etc.), which should ensure easy separation of the block from fiberglass after its curing. The surfaces of metal parts that must be securely glued to plastic are cleaned and thoroughly degreased with acetone or another solvent. Then a decorative layer is applied, which will protect the fiberglass surface from wear, will allow you to get a smooth glossy surface of the conduit. The decorative layer is prepared from an epoxy binder with the introduction of 10% titanium dioxide, chromium oxide or aluminum powder into it. After gelatinization of the pigmented layer, you can start gluing the water intake.
Fiberglass needs to be cut into pieces and strips in such a way that its layers fit tightly on the surface of the blockhead without wrinkles and air bubbles. After applying a layer of binder, a layer of fiberglass is applied and carefully smoothed to the surface, making sure that the binder evenly, without gaps, appears through the fabric. The total thickness of fiberglass should be 6-8 mm. After gluing several layers of fabric, they install the body of the inspection hatch, the air fitting and embedded metal strips with threaded holes for fixing the protective grille, then continue molding.
There is another option for installing the grate: after removing the water intake from the block, vertical grooves are cut through the ends of the longitudinal strips of the grate in fiberglass, the strips are inserted and temporarily fixed with wedges, then the grooves are sealed with epoxy glue with fiberglass. The fastening of the ends turns out to be more reliable if holes are drilled in the strips at the ends.
It is best to complete the molding of the water intake in one step and stand it on the block for two days, after which you can remove the foam block from it. This can be done from both sides of the pipe at once.A blockhead can be made of gypsum or wood, wax or plasticine can be used to facilitate the processing of the outer surface. In the manufacture of several water intakes for one blockhead, a wooden block of a detachable design is convenient, described in the 3rd edition of the book «15 projects of vessels for amateur construction».
Sometimes it is preferable to make a water intake from thin-sheet (2-3 mm) metal. And in this case, too, a dummy is needed, according to which they make a preliminary marking of individual parts of the water intake that have a relatively simple perish. For each part, a template is cut out of cardboard or thin tin, which is used for marking on metal. The blanks are subjected to gouging — they are given the desired shape by striking with a hammer with a rounded impact part on the inner surface of the workpiece placed on the end of a birch chock. Periodically, the blanks are applied to the dummy to control their shape.
At the end of the gouging, the workpieces are adjusted to each other along the edges and, laid on a block, they are picked up by welding. The final welding is performed after tacking the bottom flange and the cylindrical ring of the stator. All seams are welded from the outside, the welding sites are carefully cleaned; it is desirable to polish the inner surface of the water intake.
It is necessary to install and weld the body of the deadwood bearing using the same conductor with a false shaft, as in the case of a fiberglass water intake.
Diagram of the device for installing the deadwood bearing housing
1 — disc centering the propeller shaft in the stator; 2 — stator; 3 — water intake block; 4 — false shaft; 5 — deadwood bearing housing; 6 — disc centering shaft in the housing 5; 7 — nut M20.
Nozzle and straightening device. To manufacture the nozzle, it is necessary to turn a block on a lathe made of solid wood or metal according to the dimensions shown in the drawing and knock out or squeeze out a shell made of stainless steel 2-3 mm thick. To facilitate this work, the nozzle blank can be cut out in the form of three to six petals with an allowance along the edges for subsequent fitting; each of the petals is knocked out to fit snugly to the surface of the blockhead. Having laid the petals fitted to each other on the block, they are tightened with clamps made of soft wire, then a flange is put on the block and it is attached to the petals. The final welding of the seams is carried out in small sections on diametrically opposite sides of the nozzle to avoid warping.
The blanks of the blades of the straightening apparatus are bent and processed, controlling the shape of the cross-section according to the template. Grind the hub, adjust and weld the ends of the blades to it. To ensure the accuracy of the assembly, it is best to make an assembly conductor in which the blades, hub and flange of the nozzle attachment to the water intake are fixed. After welding the blades with the hub, their outer ends are drilled along the longitudinal profile of the nozzle, then all the parts are fixed in the conductor. Here, a flange is welded to the end of the shell, seams are welded at the ends of the blades. Then the final groove of the seat recess in the flange is made and the bushing is drilled under the rubber-metal bearing. A fitting for water intake into the engine cooling system is welded into the shell.
All surfaces of the straightening apparatus, washed with water, are cleaned from welding surges, small shells are putty with epoxy putty, everything is polished.
The rotor. The four-bladed rotor can be made of cast (brass, aluminum alloy) or welded construction (steel).
D=189, H=190. A is the straightened surface of the blade.
Bend from the sheet according to the appropriate radius (bulge on us).
To process the blades, it is necessary to make a stepper slide consisting of a base-plate — disk with annular grooves drilled in it for installing stepper angles, the angles themselves and counter patterns to control the cross-section of the blade at the radii specified in the drawing. Step angles and counter-patterns are cut out of 1.5-2 mm sheets of metal and bent according to the corresponding radii.
Diagram of the device for assembling the rotor and processing the blades
1 — steel plate; 2 — grooves for stepper angles; 3 — gasket, δ=13; 4 — roller; 5 — hub; 6 — blade blank; 7 — counter template; 8 — step square; 9 — axial line of the blade; 10 — control risk.
The rotor of the water cannon is of right rotation. This means that the right edge of the blade should be higher than the left, if you look at the blade from its outer end. The pre-turned rotor hub is mounted on the plate with the rear end facing down and is centered using a short roller.
The general sequence of work on the manufacture of a welded propeller or rotor is described in the aforementioned book «15 projects». Note that the screw surface of the discharge side of the blade can be obtained from a flat blank only when bending with uniform metal extraction. The blade is bent by clamping the root section of the workpiece in a vice and striking it with a hammer. On the reverse side, the blade must be supported with a light sledgehammer. In this case, the blade should bend between the support and the place of impact, and not at the root. The surface of the blade is controlled by applying the workpiece to the step slide; the gap between the blade and the edge of the square should not exceed 0.3 mm. The final finishing is carried out with a saw blade.
The convex (sucking) side is processed using counter patterns for these radii. The cross sections of the blades are of a segmented profile, i.e. they represent a part of a circle bounded by a chord coinciding with the discharge side. Having three given points of the profile — the thickness and width of the section, it is easy to find the value of the radius for constructing the profile back. You can also use the ordinates of the profile given, for example, in the «Handbook of boats, boats and motors» (1982, «Shipbuilding»). Then the blade is electro-welded to the hub, straightened and finally welded in short sections alternately on both sides of the blade. After welding all the blades, check the density of their fit to the stepper angles, if necessary, bend, cut the rotor in diameter, process the welds and drill a hole in the hub for the propeller shaft. The finished rotor must be subjected to static balancing on a wall with parallel and horizontal knives. The balanced rotor should not turn spontaneously on the knives. The metal from the side of the heavier blade, which turns out to be at the bottom, is removed from the inside of the hub. Of course, the blades and the outer surface of the hub must be polished.
Shaft line. The case of the deadwood bearing shown in the drawing is designed for the installation of angular contact ball bearing No. 46205. If such a bearing is not available, it is necessary to adjust the dimensions to the available one, capable of withstanding an axial load of up to 200 kgf at a rotational speed of about 4000 rpm. It is possible to make this unit according to the type of «vortex» gearbox — with thrust bearing No. 8106 and needle 2.109-000, or to embed the thrust assembly of the propeller shaft into the gearbox.
The rubber-metal bearing can be made independently, using the help of an auto repair shop. Having turned the bearing sleeve out of bronze or brass, it is filled with finely chopped pieces of crude oil- and gasoline-resistant rubber used to repair car tires. The sleeve is inserted with a sliding fit into a steel cup and the rubber is compacted using a plunger, which is deposited by any press. Then the glass with the sleeve is placed for 2.5 hours in the hob. After cooling, a hole with a diameter of 2 mm smaller than the shaft neck is drilled in the rubber and four triangular grooves are cut along it for the flow of water, which in this case serves as a lubricant.
Ending, beginning see here.
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