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PERSONAL TRANSPORT: GROUND, WATER, AIR
Fast paced aquaped. Personal transport
Directory / Personal transport: land, water, air Vessels that use the muscular strength of a person for movement have never been classified as high-speed. The only exception is racing boats for rowing, which are the fastest of the muscle ships. Thanks to their successful configuration and the most complete use of the muscular energy of athletes, the G12 boats are capable of speeds up to 20 knots over a two-kilometer distance. But this does not mean at all that such a speed is the limit of the possibilities of human movement on the water surface. If we move away from the canonical designs of rowing vessels intended for official competitions, then it becomes possible to create muscle-walking devices that reach speeds of up to XNUMX knots! When designing high-speed non-motorized ships, the designer has to solve two main tasks: creating an efficient propulsion device and manufacturing a hull with minimal movement resistance. Further improvement of the oar propeller is unlikely to lead to any noticeable increase in its efficiency. The cyclicity of the oar action, its slippage in the water during the stroke, the aerodynamic resistance during the non-working (reverse) course, the losses when the blade enters the water at the beginning of the stroke and when it exits the water at the end - all this leads to the fact that the efficiency of this propulsion unit is only about 65 percent. The propeller has a noticeably greater efficiency. Few people know that ordinary rowing boats were equipped with a muscle-driven propeller at the beginning of the last century. Its advantages are obvious: it does not have a cyclical stroke, and the so-called thrust of the propeller blades is constant during its rotation. In addition, with a relatively low drive power and low speed, low-speed propellers of large diameter with narrow blades can be used - the efficiency of such a propulsion unit reaches 90 percent.
When creating a body with low resistance to movement, it must be taken into account that its movement at the boundary of two media causes a large wave resistance. You can get rid of it by moving the body completely into one of the environments - under water or in the air. In the first case, it will be necessary to create an apparatus consisting of a streamlined float moving under water with a propeller and a seat with a pedal drive unit located above it, in the air. In the second - to create a pedal glider or a hydrofoil. It must be said that all these schemes were once implemented by designers, and the fastest (with hydrofoils) muscle hoists developed speeds of up to 13 knots! However, all these record-breaking aquapeds, designed to achieve the highest speed, are unlikely to ever be able to find practical application. The fact is that they have either unsatisfactory stability or insufficient displacement, and special training is required to move on such an apparatus. Our goal was to create a high-speed muscle walker capable of becoming a real water bike, which can be controlled by almost any person. The displacement body of the aquaped is made extremely streamlined, with a large ratio of length to width. In order to make it easy, it is advisable to make it by gluing on a block. The blockhead itself is easiest to make from wood, cement and gypsum.
First of all, you need to make a base for a blockhead - it can be a flat floor area in a barn, or better, a shield made of even boards: its length is 4,5 and its width is 0,7 m. In accordance with the theoretical drawing, the axis of symmetry is depicted on the shield (diametrical plane ) of the hull and perpendicular to it - the line of location of the frames. The latter are cut out of plywood 6-8 mm thick; on the shield they are temporarily fixed with the help of braces.
Further, rails are fixed on each of the frames on both sides - they will be the basis of the wooden sheathing of the blockhead. Please note that the rails should be positioned so that the distance from the surface of the wooden sheathing to the outer contour of the frame is at least 10 mm. For sheathing, you can use any trimming boards, slats or picket fence strips. Sheathed blockhead is brought to the desired shape with a cement-sand mortar. To keep the solution on the skin, it is advisable to hammer more nails into the boards so that the head of each protrudes 6-8 mm above the surface. The solution is first thrown onto the lining with a trowel, and then smoothed out with a flat board, as shown in the figure. In this case, the board should rest on the ends of the plywood frames. Finally, the blockhead is brought to the desired shape with the help of gypsum or alabaster, as well as putty. The final stage of work is sanding, painting and coating the surface with an actiadge coating (wax parquet mastic). Food packaging film can also be used as a separating layer - it is very thin and literally sticks to any surface. To mold the body shell, you will need glass matting (for two or three initial layers), a thinner finishing glass fabric to level the surface, as well as a binder - epoxy or polyester resin. It is desirable to stick out in one step so that each subsequent layer of binder and fiberglass lies on the not yet fully cured resin of the previous layer. After gluing is completed, it is desirable to roll a thin polyethylene film to the surface of the case - it prevents the hardener and plasticizer from volatilizing from the epoxy resin, which accelerates polymerization, and as a result improves the strength and durability of the shell. A day after gluing, the shell is removed from the blockhead, and plywood frames are fitted to it, forming the aquaped cockpit, fender, keel and false keel slats, gunwale and stringers. It is desirable to glue them into the body after the manufacture of the deadwood and the pedal mechanism. The upper part of the hull (deck and fairing) - made of plywood 3 mm thick; after assembly, it is pasted over with one layer of fiberglass using epoxy resin. In the manufacture of the hull, it is necessary to provide drain holes in its front and rear parts, plugged with a pair of plugs - through them, after each swim, it is necessary to drain the water that has entered the hull. The propeller drive is pedal driven, using a standard bicycle bottom bracket, sprocket and a pair of cranks with pedals. The torque from the sprocket is transmitted by means of a bush-roller chain to the multiplier from a hand drill, and then to the stern shaft and, accordingly, the propeller. It is desirable to use the multiplier from a two-speed drill - this will allow you to choose the optimal gear ratio of the chain and gear drives from the pedals to the mover. Before installing the multiplier, it is desirable to seal its body with the help of the “hermesil” or “auto-sealant” composition, and fill its cavity with gear oil - this will increase the durability of the mechanism and the efficiency of the gear. In this case, most likely, complete tightness will not work (the oil will still penetrate through the gaps in the input and output shaft plain bearings), so a plastic trough should be installed under the multiplier to collect the oil. The pedal assembly carriage is welded to a beam (square section steel tube), which, in turn, is fixed to the front and rear cockpit frames. The seat of the aquapedist is also installed on the beam. As the latter, a stamped plastic frame of a small office chair was used, although, in principle, this can be done independently. Fastening the seat to the beam - using a pair of clamps. Deadwood consists of a duralumin tube with two bearing units at its ends - a steel shaft rotates in them. At the rear of the deadwood there is a sleeve with a locking device that allows you to change the propeller pitch (blade angles) in order to achieve optimal propeller efficiency and, accordingly, the maximum speed of the aquaped. The bushing consists of a duralumin spinner and a two-disc clamp, with which the screw hubs are fixed. In the manufacturing technology of the fixing device, there is one feature that must be taken into account. Before cutting the M10 threaded holes for the propeller hubs, a round duralumin plate 0,5 mm thick is clamped between the disks. After drilling and threading, the plate is removed - a guaranteed gap of 0,5 mm will ensure that the hubs are securely fixed in the bushing. When assembling the stern tube into the cavity between the stern tube and the stern shaft, it is necessary to introduce several felt rings impregnated with cyatim grease. This will prevent water from entering the body of the aquaped through the stern tube.
On an aquapede, it is most advantageous to use a propeller with a diameter of 400 mm with narrow blades cut from 4 mm thick duralumin sheet. These propellers are most efficient at low power transmission and low blade load and have an efficiency of over 90 percent! The workpiece is first bent in accordance with the shape of the concave part of the propeller blade and twisted, after which its convex part is profiled in accordance with the theoretical drawing of the propeller. The finished blades are fixed on the hubs with aluminum rivets, and when adjusting the propeller pitch, they are installed strictly at one angle to the hub axis using a template. The optimal propeller pitch is selected in trial runs.
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