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MODELING
A ship model with a steam engine. Tips for a modeler
Directory / Radio control equipment Reliability and safety are the main criteria that guided me when choosing the type of steam engine. A steam engine with an oscillating cylinder, as tests have shown, with the correct, accurate manufacture of the model, can withstand even double overloads. But not without reason I emphasized accuracy - it is the key to success. Try to follow all our recommendations exactly.
Now let's talk about the steam engine itself. Figures I and II show the principle of its operation and device.
A cylinder (parts 11, 1 and 2) with a spool plate 13 is hinged on the frame 8. A hole 3 is drilled in the cylinder and the spool plate for the entry and exit of steam. In addition, another spool plate 4 is rigidly installed on the frame. Two holes. During the operation of the steam engine, when the cylinder hole is aligned with the right hole of the spool plate 4, steam enters the cylinder (see Fig. I, phase A). The expanding steam pushes the piston 13 down to the so-called bottom dead center (phase B). Thanks to the flywheel 9, the movement of the piston at this point will not stop, carried away by inertia, it rises, pushing out the exhaust steam. As soon as the hole of the cylinder coincides with the left hole of the plate 4, the steam will be released into the atmosphere (phase B). The spool plates, as you understand, must be tightly fitted to each other, otherwise steam will penetrate into the gap and the engine efficiency will noticeably decrease. Therefore, a spring is installed on the axis 7, which presses the plate 4 to the plate 8. In addition to the main function, this unit also performs the role of a safety valve. When the pressure in the boiler rises for any reason, the spring will compress, the plates will move apart and the excess steam will come out. Therefore, the spring is tightened with a nut so that the motor shaft can make several revolutions by inertia. Check it by turning it by hand. Steam enters the machine through a tube 5. One end of it is connected to the inlet on the spool plate 4, the other end is fitted with a hose 6 connected to the steam boiler. Any rubber hose that does not contain thread or wire reinforcing elements is suitable for our engine. But best of all from the car's fuel line. The hose on the steam line is not fixed by anything. This is also a security measure. When the steam pressure increases, the hose will break off the tube, and the pressure in the boiler will instantly drop. The main working body of the machine is cylinder 1. From above it is sealed with a tin washer 2, from below it is closed by piston 13. A rod-piece of a knitting needle with a washer at the end is soldered into the piston. Through its hole passes the finger of the crank 14, soldered to the shaft 10 of the propeller, also made of spokes. A flywheel 9 is installed on the shaft. The shaft of the steam engine rotates in a plain bearing 12, which is soldered into the frame. We advise you to start the manufacture of a steam engine with the most labor-intensive parts - a cylinder, a piston, a steam distribution device. For the cylinder, select a brass tube with a diameter of 12-16 mm. The inner surface should be carefully polished. It is advisable to do this on a lathe with a rod with a gauze swab rubbed with GOI paste or any other for polishing metals. As a result of processing, the diameter of the tube at the ends may be larger than in the middle. Therefore, only the middle part is used for the cylinder, correspondingly increasing the length of the workpiece. Solder a tin cover to the finished cylinder, rinse the assembled part with kerosene and take on the piston. It consists of the piston itself, the rod and the washer. The piston is preferably made of bronze or cast iron. Turn the workpiece on a lathe to such a diameter that it fits tightly into the cylinder. Try it on without removing it from the chuck, and then drill a hole for the stem. Now cut the workpiece to the desired length and solder the rod into it. Solder the washer to the stem. If the piston diameter turned out to be larger than necessary, it is ground down with a file with a fine notch and sandpaper, and then polished. This is done on a lathe using a flannelette strip and polishing paste. It is advisable to cut the spool plates from brass with a thickness of 2-3 mm. For a tighter fit to the cylinder, make a notch in the spool plate 8. And then drill a hole for the axis 7 - a screw with a diameter of 3 mm with a countersunk head (the figure shows the marking of the plate). On the spool plate 4, using a compass and a punch, mark the places for the inlet and outlet holes. Drill them and start sanding both plates with sandpaper. Then they are also polished. Spool plate 8 must be soldered to the cylinder. First, insert the axis into it, tie the plate to the cylinder with a thin wire, lubricate the soldering points with flux, cover them with pieces of solder and heat them on a gas burner. The solder will spread over the surface lubricated with flux and grab the parts. If the cylinder cover is soldered when heated, it does not matter - it is easy to solder it again. Steam holes must be drilled in the cylinder. The conductor for them can be the steam distribution hole 3 in the plate B. The assembled unit is mounted on a frame 11, bent from tin. When making it, try to accurately maintain the distance between the axis 7 and the axis of the bearing 12. Solder the spool plate 4, the tube 5 of the steam line 6, the bearing 12 to the finished frame. The hole for the shaft 10 is drilled in place, and the distance between the parts of the frame is selected depending on the size of the flywheel 9. The flywheel can be any steel or bronze part, the dimensions of which are not less than those indicated in our figure. Bearing 12 is best machined from bronze. Now let's talk about the manufacture of a steam boiler (Fig. III).
Bend the shell 1 (side surface) of the boiler from tin. Solder two slightly concave tin bottoms 2 into its end parts. The shell is made as follows. Stretch a strip of tin from a can 80 mm wide and about 200 mm long around a thick rod several times - the workpiece will take the form of a regular ring. Cut a strip of the desired length from it and solder a cylinder with a diameter of 40 mm. Bottoms 2 are made in the form of an already soldered boiler. An ordinary flat bottom cannot withstand steam pressure. Therefore, give the workpiece a spherical shape. This is done with light blows of a hammer with a convex striker on a thick wooden plate (you can also use soft metal, for example, lead). Solder the bottoms with the convex side inward, bend the edges and solder. For pouring water, a special fitting is provided on the boiler. It consists of an MZ-M4 nut 10-12 mm long (item 3) and a corresponding screw that acts as a plug. Fill the boiler with a medical syringe. The steam formed in the boiler exits through hole 4 (its diameter is 6 mm). Water droplets usually fly out along with the steam, which interferes with the operation of the steam engine. Therefore, a special trap cap 5 must be installed above the outlet, and a branch pipe 6 of the steam pipeline must be soldered to it. Then the droplets flying out of the boiler will settle on the walls of the hood, and only dry steam will enter the pipe. Check the finished boiler for leaks. Lubricate all sealed seams with soapy foam and blow into the boiler through the steam line. In those places where soap bubbles appear, re-soldering is needed. Solder legs 7 to the boiler and bend the burner for dry fuel from tin. The steam engine is ready. We have already said that, with proper handling, our steam engine is perfectly safe. However, testing precautions are not superfluous. First of all, remember that the steam formed in the boiler must constantly leave it: be spent on the operation of the piston, and then flow out through the hole in the spool plate. If this does not happen, you must immediately extinguish the fire, wait until the boiler has completely cooled down, find and fix the problem. This safety rule must be strictly observed. And we advise you to invite someone from knowledgeable adults before starting the test. Connect the steam engine to the boiler with a hose. Do not fasten the ends of the hose to the nozzles. To prevent the burner flame from ruining the hose, wrap it in foil. Pour 30-40 ml of boiled water into the steam boiler and light the burner with two (no more) dry fuel tablets. Slowly start turning the shaft of the steam engine. After about 30 - 40 seconds, the water in the boiler will make a noise, and hot water will drip from the exhaust outlet of the machine. Then steam will also come out of the slot of the spool device. A properly made steam engine starts working in 1-2 minutes. Make sure that the water in the boiler does not boil away, otherwise it will melt. Install the steam engine that has been proven in operation on the model. It can be ready-made, purchased or made with your own hands from tin or polystyrene. Author: A.Ilyin
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