Stationary engine
Although the romantic era of steam is long gone, we miss the old days when you could see wagons pulled by huge magnificent locomotives, red-hot steamrollers kneading road rubble, or steaming locomotives working in the field.
A single stationary steam engine used to drive centrally, by means of a belt drive system, all factory machines or looms. Her boiler burned ordinary coal.It may be a pity that we will not see such machines outside the museum, but it is possible to build a wooden model of a stationary machine. к it is a great pleasure to have such a wooden mobile at home, a mobile working device. This time we will build a model of a more complex slide synchronized steam engine than before. To drive the wooden model, of course, we will use compressed air from a household compressor instead of steam.
Steam engine work it consists in the release of compressed water vapor, and in our case compressed air, into the cylinder, then from one side, then from the other side of the piston. This results in a variable sliding motion of the piston, which is transmitted through the connecting rod and drive shaft to the flywheel. The connecting rod converts the reciprocating motion of the piston into rotational motion of the flywheel. One revolution of the flywheel is achieved in two strokes of the piston. The distribution of steam is carried out using a slider mechanism. Time is controlled by an eccentric mounted on the same axis as the flywheel and crank. The flat slider closes and opens the channels for introducing steam into the cylinder, and at the same time allows the used expanded steam to be expelled.
Tools: Trichinella saw, saw blade for metal, electric drill on a stand, drill mounted on a workbench, belt sander, orbital sander, dremel with wood attachments, electric jigsaw, glue gun with hot glue, carpentry drills 8, 11 and 14 mm. Scrapers or wood files may also come in handy. To drive the model, we will use a home compressor or a very powerful vacuum cleaner, the nozzle of which blows air.
Materials: pine board 100 mm wide and 20 mm thick, rollers with a diameter of 14 and 8 mm, board 20 by 20 mm, board 30 by 30 mm, board 60 by 8 mm, plywood 4 and 10 mm thick. Wood screws, nails 20 and 40 mm. Clear varnish in spray. Silicone grease or machine oil.
Machine base. It measures 450 x 200 x 20 mm. We will make it from two pieces of pine boards and glue them together with longer sides, or from one piece of plywood. Any irregularities on the board and the places left after cutting should be smoothed out well with sandpaper.
Flywheel axle support. It consists of a vertical board and a bar covering it from above. A hole for a wooden axis is drilled at the point of contact of their surfaces after they are screwed. We need two sets of identical elements. We cut supports from a pine board with dimensions of 150 by 100 by 20 mm and rails with a section of 20 by 20 and a length of 150 mm. In the rails, at a distance of 20 mm from the edges, drill holes with a diameter of 3 mm and ream them with an 8 mm drill bit so that the screw heads can easily hide. We also drill holes with a diameter of 3 mm in the boards on the front side so that the planks can be screwed on. At the point of contact with a 14 mm drill, we drill holes for the flywheel axis. Both elements are carefully processed with sandpaper, preferably an orbital sander. Also, do not forget to clean the holes for the wooden axle from the roller with sandpaper rolled into a roll. The axle should rotate with minimal resistance. The supports created in this way are disassembled and coated with a colorless varnish.
Flywheel. We will start by drawing a circle structure on plain paper.Our flywheel has an overall diameter of 200mm and has six spokes. They will be created in such a way that we will draw six rectangles on the circle, rotated 60 degrees with respect to the axis of the circle. Let's start by drawing a circle with a diameter of 130 mm, then we denote the spokes with a thickness of 15 mm.. In the corners of the resulting triangles, draw circles with a diameter of 11 mm. Lay the paper with the circle structure drawn on the plywood and first mark the centers of all the small circles and the center of the circle with a hole punch. These indentations will ensure the accuracy of the drilling. Draw a circle, a hub and a wheel where the spokes end in a pair of calipers, right on the plywood. We drill all the corners of the triangles with a drill with a diameter of 11 mm. With a pencil, mark the places on the plywood that should be empty. This will save us from making mistakes. With an electric jigsaw or a trichome saw, we can cut off pre-marked, excess material from the flywheel, thanks to which we get effective knitting needles. With a file or a cylindrical cutter, a stripper, and then with a dremel, we align possible inaccuracies and bevel the edges of the spokes.
Flywheel rim. We will need two identical rims, which we will glue on both sides of the flywheel. We will also cut them out of plywood 10 mm thick. The wheels have an outer diameter of 200 mm. On plywood we draw them with a compass and cut them out with a jigsaw. Then we draw a circle with a diameter of 130 mm coaxially and cut out its center. This will be the flywheel rim, that is, its rim. The wreath should increase the inertia of the rotating wheel with its weight. Using wikol glue, we cover the flywheel, i.e. the one with knitting needles, wreaths on both sides. Drill a 6 mm hole in the center of the flywheel to insert an M6 screw in the center. Thus, we get an improvised axis of rotation of the wheel. After installing this screw as the axis of the wheel in the drill, we quickly process the spinning wheel, first with coarse and then with fine sandpaper. I advise you to change the direction of rotation of the drill so that the wheel bolt does not loosen. The wheel should have smooth edges, and after processing on our pseudo-lathe, it should spin smoothly, without side impacts. This is a very important criterion for the quality of the flywheel. When this goal is reached, remove the temporary bolt and drill a hole for the axle with a diameter of 14 mm.
Machine cylinder. Made from 10mm plywood. We'll start with a 140mm x 60mm top and bottom and a 60mm x 60mm back and front. Drill holes with a diameter of 14 mm in the center of these squares. We glue these elements together with hot glue from a glue gun, thus creating a kind of cylinder frame. The parts to be attached must be perpendicular and parallel to each other, so when gluing, use a mounting square and hold them in position until the adhesive hardens. The roller that will serve as the piston rod is well inserted into the holes in the back and front when gluing. The future correct operation of the model depends on the accuracy of this gluing.
Piston. Made of plywood 10 mm thick, has dimensions of 60 by 60 mm. Sand the edges of the square with fine sandpaper and chamfer the walls. Drill a 14mm hole in the piston for the piston rod. A hole with a diameter of 3 mm is drilled perpendicularly in the top of the piston for a screw that fastens the piston to the piston rod. Drill a hole with an 8mm bit to hide the head of the screw. The screw goes through the piston rod holding the piston in place.
piston rod. Cut out a cylinder with a diameter of 14 mm. Its length is 280 mm. We put the piston on the piston rod and install it in the piston frame. However, first we determine the position of the piston relative to the piston rod. The piston will move 80 mm. When sliding, it should not reach the edges of the inlet and outlet ports of the piston, and in the neutral position it should be in the center of the cylinder, and the piston rod should not fall out of the front of the cylinder. When we find this place, we mark with a pencil the position of the piston in relation to the piston rod and finally drill a hole with a diameter of 3 mm in it.
Distribution. This is the hardest part of our car. We need to recreate the air ducts from the compressor to the cylinder, from one side to the other side of the piston, and then from the exhaust air from the cylinder. We will make these channels from several layers of plywood 4 mm thick. The timing consists of five plates measuring 140 by 80 mm. Holes are cut in each plate according to the figures shown in the photo. Let's start by drawing on paper the details we need and cut out all the details. We draw patterns of tiles with a felt-tip pen on plywood, arranging them in such a way as not to waste material, and at the same time have as little labor as possible when sawing. Carefully mark the marked places for the auxiliary holes and cut out the corresponding shapes with a jigsaw or tribrach. At the end, we align everything and clean it with sandpaper.
Zipper. This is a plywood board of the same shape as in the photo. First, drill holes and cut them out with a jigsaw. The rest of the material can be cut with a trichome saw or disposed of with a conical cylindrical cutter or dremel. On the right side of the slider there is a hole with a diameter of 3 mm, in which the axis of the eccentric lever handle will be located.
Slide guides. The slider works between two skids, the lower and upper guides. We will make them from plywood or slats 4 mm thick and 140 mm long. Glue the guides with Vicol glue to the corresponding next timing plate.
Connecting rod. We will cut it in a traditional shape, as in the photo. The distance between the axes of the holes with a diameter of 14 mm is important. It should be 40 mm.
Crank handle. It is made from a strip of 30 by 30 mm and has a length of 50 mm. We drill a 14 mm hole in the block and a blind hole perpendicular to the front. File the opposite end of the block with a wood file and sander with sandpaper.
Piston rod grip. It has a U-shape, made of timber 30 by 30 mm and has a length of 40 mm. You can see its shape in the photo. We drill a 14 mm hole in the block on the front side. Using a saw with a saw blade, make two cuts and make a slot in which the piston rod will move, using a drill and a trichinosis saw. We drill a hole for the axle connecting the crank to the piston rod.
Cylinder support. We need two identical elements. Cut out the 90 x 100 x 20mm pine board supports.
Eccentricity. From 4mm thick plywood, cut four rectangles, each 40mm x 25mm. We drill holes in the rectangles with a 14 mm drill. The design of the eccentric is shown in the photo. These holes are located along the longitudinal axis, but are offset from each other along the transverse axis by 8 mm. We connect the rectangles in two pairs, gluing them together with their surfaces. Glue a 28 mm long cylinder into the inner holes. Make sure that the surfaces of the rectangles are parallel to each other. The lever handle can help us with this.
рычагconnection of the slider with the eccentric. It consists of three parts. The first is a U-shaped handle that includes a slider. A hole is drilled in the plane for the axis along which it performs a rocking motion. An eccentric clamp is glued to the other end. This clip is collapsible and consists of two blocks of 20×20×50 mm each. Connect the blocks with wood screws and then drill a 14mm hole on the edge of the rib for the eccentric axle. Perpendicular to the axis in one of the blocks we drill a blind hole with a diameter of 8 mm. Now we can connect both parts with a shaft with a diameter of 8 mm and a length of about 160 mm, but the distance between the axes of these parts is important, which should be 190 mm.
Machine assembly. Using a bolt, install the piston on the piston rod inserted into the cylinder frame, and drill a hole at the end for the axis of the crank handle. Remember that the hole must be parallel to the base. Glue the following timing drive elements to the cylinder frame (photo a). The next first plate with four holes (photo b), the second one with two large holes (photo c) connects the holes into two pairs. The next is the third plate (photo d) with four holes and put the slider on it. The photographs (photo e and f) show that the slider, displaced by the eccentric during operation, sequentially exposes one or the other pair of holes. Glue the two guides leading the slider to the third plate from the top and bottom. We attach the last plate with two holes to them, covering the slider from above (photo d). Glue the block with the through hole to the top hole of such a diameter that you can attach the compressed air supply hose to it. On the other side, the cylinder is closed with a lid screwed on with several screws. Glue the flywheel axle supports to the base, being careful that they are in line and parallel to the plane of the base. Before complete assembly, we will paint the elements and components of the machine with a colorless varnish. We put the connecting rod on the flywheel axis and glue it exactly perpendicular to it. Insert the connecting rod axle into the second hole. Both axes must be parallel to each other. On the other side of the base, glue two boards to make a support for the cylinder. We glue a complete cylinder with a timing mechanism to them. After the cylinder is glued, install the lever that connects the slider to the eccentric. Only now can we determine the length of the lever that connects the connecting rod crank to the piston rod. Properly cut out the shaft and glue the U-shaped handles. We connect these elements with axes made of nails. The first attempt is to turn the flywheel axle by hand. All moving parts must move without undue resistance. The crank will make one revolution and the spool should react with an eccentric displacement.
A game. Lubricate the machine with oil where we expect friction to occur. Finally, we connect the model with a cable to the compressor. After starting the unit and supplying compressed air into the cylinder, our model should run without problems, giving the designer a lot of fun. Any leaks can be patched with glue from a hot glue gun or clear silicone, but this will make our model indelible. The fact that the model can be disassembled, for example, to show the movement of a piston in a cylinder, is a valuable advantage.
