Deadwood with propeller for radio-controlled models. Stern tube diagrams

First, a little historical background about the prototype. The history of the creation of German torpedo boats dates back to the First World War. The first example of ships of this type was built in 1917. We can immediately say that he was very far from perfect. But still, by the end of the war, the German fleet consisted of 21 boats. After the end of the war, many countries lost interest in this type of weapon. Things were different in Germany, which was subject to many restrictions on weapons, according to the Treaty of Versailles. By the way, nothing was said there about torpedo boats. Therefore, the Germans in 1923 First, they purchased several old torpedo boats for the Hanseatic School of Yachtsmen and the German High Seas Sports Society. Under the cover of these organizations, work began to improve existing boats and create new ones. By the end of the 30s, tactical and technical requirements for the new “mosquitoes” were developed. According to German naval doctrine, speed indicators, in contrast to boat designs from other countries, were relatively low - about 40 knots. By that time, different companies presented three versions of boats with different layouts and different numbers of gasoline engines. But they did not satisfy the military, therefore, a completely new project was required. In 1928 The attention of specialists was attracted by the motor yacht Oheka II, built by Lurssen for an American financial tycoon. The hull, at that time, had an advanced design, its power set was made of light alloys, and the skin consisted of two layers of wood. Three gasoline engines allowed the yacht to reach a speed of 34 knots. At that time these were outstanding characteristics. In November 1929 The Lurssen company received an order for the development and construction of a torpedo boat. The designers took the design of the yacht Oheka II as a basis and almost doubled the displacement to compensate for the moment created by the high-mounted torpedo tubes. The boat entered service on August 7, 1930. and changed its name several times, as a result it received the designation S-1 (Schnellboot). It should be noted that even increasing engine power did not help achieve the design speed of 36.5 bridles. At speeds close to maximum, the bow of the boat came out of the water, the sides washed out and strong splash resistance arose. This problem was solved by using the so-called “Lurssen Effect”. Its essence was that small auxiliary rudders were placed in the outer propeller flows, which turned 15-18 degrees towards the side. This helped achieve an increase in speed to two knots. Subsequently, auxiliary rudders became a mandatory part of the design of all snailboats. S-1 and became the progenitor of the entire series of German S-class torpedo boats. Since 1943, boats of the most successful modification, Schnellboot type S-100, began to be produced. It differed from previous types of ships by its armored dome-shaped conning tower. The S-100 class boats were almost twice as long as enemy boats of the same class. They were equipped with cabins, a galley, a latrine and everything necessary for long journeys, which made it possible to use them at a great distance from the bases. Boats of this type had engines with a total power of 7,500 hp, which allowed them to reach a speed of 43.5 knots.

Preparing and assembling the case

A 1:72 scale model of the S-100 torpedo boat is produced by the German company Revell. I’ll say a little about the model itself; now there are only these photos of the sprues.

Upon closer inspection, you can see that all the details are made to a high level, there are no sink marks or offsets, and very little flash. I was pleased with the large number of details and the quality of their workmanship. This model was immediately, even before acquisition, planned for radio control. Its decent length - 500mm, made it possible to make a good radio-controlled model of a boat. It was also intended to compete in the F-4A class at ship modeling competitions. Work on the model began even before the creation of the blog, but the idea was already there, so some photos of the construction process were taken. The construction of the radio-controlled boat model began with preparing and gluing the hull. In principle, the fit of the model parts is good, but for convenience, I glued the body, which is almost 500mm long, in parts.

Then, to seal the case, I poured polystyrene very well over the entire seam.

Manufacturing and installation of stern tubes and helmport pipes

The next stage is preparation for the manufacture of stern tubes and helmport pipes. To do this, I turned the bushings on a lathe. For propeller shafts and rudder stocks I will use a rod with a diameter of 2 mm. The inner diameter of the stern tube bushings must be maintained strictly according to the diameter of the propeller shafts. This is necessary to ensure tightness. The pipes themselves were made from tubular elbows of antennas of the required diameter. Unfortunately, the photos of the stern tubes did not turn out well, but I think the point is clear.

The process of making helmport pipes is the same, but here the photos are good and you can see everything on them. We insert bushings into the pieces of tubes and seal them well.

Now you need to glue the stern tubes into the hull of the radio-controlled boat. To do this, we first mark on it the places for pipes and propeller shaft brackets. We make cuts and install the stern tubes without glue. To facilitate installation, you can make a device, as shown in the photo, for example, from a piece of a floppy disk body.

We set the required angle of the propeller shafts and glue the device to the hull. Now you need to make the propeller shaft brackets. We sharpen brass bushings on a lathe; here the internal diameter can be made a little larger. If during the manufacture of stern tubes and helmport pipes the internal diameter was kept strictly 2 mm, for the existing shafts, then in the brackets it can be made 2.1 mm. Since it is practically impossible to set all three points on which the propeller shaft rests on one line. And if there is even a slight misalignment, the propeller shaft will rotate slowly, which will lead to a loss of motor power, an increase in current in the circuit and unnecessary battery consumption. On a small radio-controlled boat model, battery consumption is a very important parameter. Since the space and weight of the battery are limited, we will not be able to accommodate a large capacity battery. In each bushing, we make grooves-cuts by slotting and solder brass strips there, obtaining a V bracket, according to the drawing. Plastic parts of the model can be used as templates. In the part that will be glued into the body, there are several cuts, so that later it will be easier to bend the part and glue it to the textolite pads with epoxy resin.

Now we make slots in the model body for the brackets and install them without gluing them. We check the ease of torsion of the shafts, if they rotate very easily, first we bait the stern tubes with a small amount of cyacrine and again check the ease of rotation of the shafts. If everything is in order, you can finally glue the stern tubes. After the cyacrine has hardened, you can remove the device. Now you need to glue in the propeller shaft brackets. In principle, some colleagues glue them into the body and then cover them with polystyrene diluted in glue. But after one unsuccessful model, perhaps due to the quality of the plastic of the hull, where after this composition dried, the parts moved and pinched the propeller shafts, repeated re-gluing did not help, I began to make this unit according to this scheme. Perhaps this increases the time spent, but after gluing, absolutely nothing will move anywhere due to deformation. In small pieces of fiberglass, grooves are cut for the brackets and holes with a diameter of approximately 2.5 mm are drilled around the perimeter. These plates are then installed inside the housing so that their slots align with the slots in the housing. Afterwards, holes are marked and drilled in the boat hull so that they coincide with the holes in the plate. Now parts like nails are sharpened from pieces of sprue. Their small diameter should match the diameter of the holes that are drilled in the plate and in the body. Using these parts, gluing them with model glue, we secure the plates on the inside of the boat hull. This operation is necessary in order to be able to glue the propeller shaft brackets to the hull with epoxy resin. During the curing process of the epoxy resin, it is possible to control the position of the brackets and, if necessary, adjust it. Also, after polymerization of the resin, there will be no deformation of the plastic case and displacement of the brackets. Then you can mark and glue the helmport pipes onto the cyacrine. Then, to seal and strengthen the adhesive joints, we lay them with two-component epoxy putty Epoxy Putty from Tamiya.

Now you can putty the installation sites of the stern tubes and plates under the brackets. For this I use two-component car putty BODY SOFT.

BODY SOFT automotive putty hardens quite quickly; after just a few hours the body can be treated. I do these things at night so that by the next evening everything will definitely harden.

Making a motor mount

The next stage is the manufacture of a motor mount and installation of electric motors on it. I bought the commutator motors in our Hobby store; apparently they are made in China. It is not possible to establish their type, I can only say that the supply voltage was written on the price tag: 3-12V.

In terms of size, something similar is used in CD-ROMs. By the way, the choice of engines is a very important moment when building a radio-controlled boat model. It is necessary to try to select electric motors in such a way that whenWith the supply voltage you planned and the minimum current consumption, they provided sufficient torque. At this stage, you can also layout the model. In the case, place mass-dimensional models of electric motors, a receiver, steering gears and a power battery. This operation can be performed in the bathroom. It is necessary to ensure that the model is located in the water as close to the waterline as possible. You also need to avoid rolls and trims. At the same time, do not forget about the accessibility of the equipment elements and chassis after gluing the deck. At this stage, it is necessary to consider removable units for access to them. For example, superstructures or some other structural elements. It is also necessary to think in advance about the tightness of the entire structure. I chose a scheme with the entire main deck removable and the false deck made of oracal. This scheme has already been tested several times and has proven its viability. Let's return to the motor mount, I made it from foil fiberglass. Two plates were soldered perpendicularly and a brace angle was soldered between them for structural strength. The engines are attached to the frame with M2 bolts.

First, a base was cut out of foil fiberglass to which the engines would be attached. It has four holes drilled for M2 bolts and two holes for the round part of the motor housing. Then, from foil fiberglass laminate, we make a part that will be attached to the bosses mounted on the model body. I drilled two holes in it for fastening, but still, it’s better to think about where to place the third hole. Still, the three-point mount is more reliable. Then we solder these two parts at an angle of 90 degrees and install a corner between them for rigidity. As practice has shown, it is better to make the part to which the motors are attached from thicker material for rigidity.

This is what this unit looks like assembled with electric motors.

The frame itself is attached to the body of the radio-controlled boat model using plexiglass bosses with M3 threads.

Installing propeller shafts and brackets

Now you need to assemble the deadwood-shaft-bracket assembly. For my radio-controlled boat model Schnellboot S-100, I used 2 mm diameter shafts from Gaupner. To avoid bending or damaging them during preparatory work, bicycle spokes, also 2 mm in diameter, were used to install and adjust the chassis of the model. Since the stern tubes are already glued into the model, now we need to fix the propeller shaft brackets. To do this, we insert shafts from bicycle spokes into the deadwoods, install the brackets in place and bend their cut parts inside the body.

Then we check the ease of rotation of the shafts in this system. If necessary, we align and bend the brackets as needed. Ultimately, we need to ensure that the shafts rotate very easily throughout this entire system. Afterwards, using a small amount of epoxy resin, we attach the propeller shaft brackets, gluing them to the PCB pads. While the resin is curing, we constantly monitor the ease of rotation of the propeller shafts and, if necessary, adjust the position of the brackets. This stage is very important, since the correct installation and fixation of the sternwood - shaft-bracket system and the ease of rotation of the shafts will in the future greatly affect the driving characteristics of the model and affect the battery consumption. After the epoxy resin has completely hardened, we once again check the ease of rotation of the catch, and if everything is in order, we finally fix the brackets, thoroughly pouring the gluing area on the textolite areas with epoxy resin. This photo shows the assembly with the brackets already bent and glued with epoxy resin.

The next stage, after fixing the brackets, is the installation of the motor mount with engines. To do this, first, on a lathe, we sharpen the bosses and cut threads into them for the screws that will secure the motor mount. In the photo above you can see that the bosses are already installed in the body. I will describe in some detail the process of installing them. I made the bosses from plexiglass, and the threads were cut for M3 bolts. To simplify the process of installing a motor mount with engines, we make two simple adaptations. We sharpen two bushings on a lathe. Since our propeller shafts and electric motor shafts have a diameter of 2 mm, we make the inner diameter of the bushings 2 mm. Their length is approximately 30mm, and the outer diameter does not matter much. Then, using these bushings, we will connect the motor shafts and propeller shafts into one whole. We screw the bosses to the motor mount, and adjusting them, we position the motor mount in the housing so that the propeller shafts rotate with maximum ease.

Connection of electric motors with propeller shafts

After installing the propeller shafts and motors on the radio-controlled boat model, you need to think about connecting them. There are several different schemes. You can connect these nodes using a flexible connection, such as a spring, or using a universal joint. We will use the second option. To do this, on a lathe, first, from steel, we turn two bushings with a ball. Let's drill the balls for further installation of wire dowels.

Here is a photo of the already installed part on the shaft with a key.

Then we will machine two cups from steel and make cuts for the keys. Then we drill the cups, on both sides with a 1.6mm drill, and cut an M2 thread for the fixing screws.

Let's put all the details together. We machine the limiting bushings onto the shafts and solder them so that there is a slight play when the propellers are screwed on and the limiting bushings are installed.

Next, we solder bushings with balls to one end of the shaft and insert wire keys into the holes so that they move easily. You saw the end result in the photo above. We secure the cups with screws on the shafts of the electric motors. Now we insert the shafts into the deadwoods, install the motor mount in place and put everything together.

The next stage is the manufacture of propellers. How to do this is described in the article.

For now we will use untreated propellers.

Now you can apply power to the engines and check how everything works.

Making steering wheels for the model

Now we need to make rudders for the radio-controlled model of the boat Schnellboot S100. For this model you need to make 3 of them. According to the rules, rudders and propellers can be made in several larger sizes. While the central steering wheel is quite large, the side steering wheels are too small. The feather has the shape of a trapezoid, so first we will make a pattern from paper. You can take the rudders from the kit as a basis and slightly increase the area. After trying on the patterns, we will transfer them to the material from which we will make the parts. Here it is better to use stainless and well-soldered metal. For these purposes, I use sheet brass with a thickness of 0.2-0.3 mm. We make the baller from a bicycle spoke, its diameter is 2mm. One end, the length of the feather, is flattened and sharpened on an electric sharpener. These are the parts prepared for soldering.

We install the stock at the location of the axis of rotation and solder it well with a powerful soldering iron to one of the walls of the pen. Then we bend the feather and solder the back edge, then solder the ends.

This is how the raw parts turned out.

Now they need to be processed and the rudders given the desired shape.

We use the same principle to make the central steering wheel. It is somewhat more complex in form, but the essence of the process is similar to that described above. The only difference is that here the leading edge is made of copper tube.

In the end you get rudders like this

Sealing the hull and ensuring buoyancy

The next stage is the installation of watertight bulkheads in the hull. This is necessary in order to provide the radio-controlled boat with buoyancy when water gets inside. For a small model, this is especially critical, since even a small amount of water can lead to flooding and possible loss. Therefore, we will divide the internal volume into four compartments and install waterproof polystyrene bulkheads. Now we can carry out a buoyancy test; for this we will flood the compartments with water.

One compartment is flooded.

Two compartments were flooded.

Three compartments were flooded.

As you can see in the photo, even when three compartments were flooded, part of the radio-controlled boat remained afloat. It follows from this that it is possible to save the model in such a situation. Thus, it turned out to be divided into four compartments: bow,

the second is the electronics compartment,

third – motor

and stern

with steering gear and steering gears. But in order to prevent water from getting inside, it is necessary to seal the case well in advance. To ensure sealing of the internal volume, by gluing the body with oracal, we will glue a polystyrene side to the sides. To gain access to the electronics compartment, after gluing the bow part of the deck, a hatch is made in the bulkhead that goes up. And to make it possible to photograph the propeller shafts, holes are made in it, which will then be sealed with oracle.

Steering gear and electronics installations

Now it’s time to install the steering gear and electronics on the Schnellboot S100 radio-controlled boat model. To do this, first, let’s think about how to mount the servo drive. I made three post-brackets from thick sprue and reinforced them with polystyrene corners. The frame itself was made from a plastic plug from a computer. It has the shape of a corner and it turns out to be quite a convenient mount.

As a servo drive I used a Chinese steering machine HXT-500, weighing 8 grams. The rod was made from wire with a diameter of 1 mm with latches made from aircraft model cord.

We install everything in place, fasten the frame with self-tapping screws to the racks from the sprues.

In the second compartment we place the electronics. The receiver and speed controller will be located there.

The deck with the main superstructure has not yet been installed, but in the future they will be glued in and to allow installation and removal of electronics, a hatch will be made in the bulkhead.

We will place the batteries for the model in the engine compartment. To prevent the battery from interfering with the rotation of the propeller shafts, we will make a partition substrate, also from a computer plug. On the sides, so that the battery does not dangle, we will lay strips of porous packaging material.

Now the radio-controlled boat model Schnellboot S100 is ready for sea trials.

Sea trials video

To be continued…

Marine site Russia no September 21, 2016 Created: September 21, 2016 Updated: November 24, 2016 Views: 27985

The purpose of the stern tube device is to provide the necessary waterproofness of the ship's hull, and the propeller shaft - one or two supports, to absorb static loads from the weight of the shaft and propeller and dynamic loads from the operation of the propeller under different immersion conditions.

Stern tube devices of sea vessels are divided into two groups: with non-metallic and metallic liners.

In the first case, backout, textolites, wood-laminated plastic, rubber-metal and rubber-ebonite segments, thermoplastic materials (caprographite, caprolon), etc. are used as antifriction bearing materials.

In an oil-lubricated metal bearing, the support bearing shells are filled with babbitt.

When operating a ship, constant and variable loads arise in the stern tube under the influence of forces and moments transmitted to the propeller shaft from the propeller, which cause stress in the stern tube bearings and pipes. The engine transmits torque to the propeller, which is not constant.

Periodic changes in torque in the engine-shafting-propeller system cause torsional vibrations. When the frequency of the disturbing forces coincides with the frequency of natural torsional vibrations, resonance conditions arise, under which the forces in the parts increase sharply.

Significant forces are also observed in near-resonance zones, when partial coincidence of frequencies occurs. In the range of 0.85-1.05 of the calculated shaft rotation speed, the presence of forbidden resonance zones is not allowed.

During the operation of the propeller, periodic disturbing forces and moments arise on its blades, which are perceived by the stern tube device and transmitted to the ship's hull through its bearings. These forces arise as a result of the change in its thrust and the tangential force of resistance to rotation of each blade during one revolution of the propeller. In this case, conditions may be created under which the frequency of the forces occurring on the propeller coincides with the frequency of the natural bending vibrations of the shaft line, which will lead to resonant vibrations of the propeller shaft and high stresses in its main sections.

The total bending moment consists of the moment from the mass of the screw, the hydrodynamic bending moment and the moment from inertial forces during bending vibrations of the shaft line.

Hydrodynamic imbalance of the propeller occurs due to differences in the pitch of each blade or when the propeller operates partially submerged. During the manufacture of the blades, their pitch differs slightly, but during operation, if individual blades break or deform, the resulting forces can lead to vibration that is dangerous for the stern tube supports. During ballast transitions, due to the difference in thrust, an additional bending moment is created, which leads to significant hydrodynamic imbalance and, as a consequence, increased vibration of the ship's hull.

The load from the mass of the propeller shaft and propeller is perceived by the stern tube bearings, which also perceive the construction static imbalance of the propeller. The maximum part of the load falls on the stern tube bearing and its aft part. During operation, additional loads may occur on the stern tube device when the propellers hit foreign objects.

The stern tube device is the same for all ships, regardless of their size and purpose, and consists of a stern tube, inside of which there are bearings, and a sealing device that prevents the penetration of sea water into the vessel. In Fig. Figure 1 shows the stern tube arrangement of a single-screw vessel with non-metallic bearings, the most widely used in the navy. The bow end of the stern tube 4 with a flange 11 is firmly attached to the afterpeak bulkhead 12, and the aft end is inserted into the stern tube 3, sealed with rubber rings 15 and tightened with a union nut 16 with a special stopper 2. The sealing rubber is installed between the restrictive collar 14 of the stern tube and the stern tube with the bow side and the union nut and the sternpost on the other side to prevent the penetration of sea water into the space between the stern tube and the sternpost.

In the area where the stern tube exits, a stuffing box seal is installed inside the vessel, which includes a packing 9 installed between the shaft and the pipe, and a pressure sleeve 10. The stuffing box is accessible from the engine room or the propeller shaft tunnel. In the middle part, the stern tube is supported by floras 13, which can be welded to the pipe or rest on a movable support, as shown in Fig. 1.

Inside the stern tube there is an aft stern tube bushing 5 and a bow bushing 7 with backout strips or its substitute 6 and 8 assembled in them according to the “barrel” or, less commonly, “dovetail” design. The stern tube bushings are secured to the pipe with locking screws to prevent rotation; the longitudinal displacement of the stern bearing strips is prevented by ring 1.
To ensure reliable lubrication and cooling, the bearings are forcibly pumped with sea water; for this purpose, grooves are provided in the set of bearing strips at their joints for the free passage of water. In the backout set, the lower strips have an end-to-end arrangement of fibers, the upper ones have a longitudinal arrangement (see Fig. 1, section A-A), since the lower ones perceive large specific loads. Brass thrust strips 18 are installed between the lower and upper backout strips, with the help of which they are prevented from turning in the stern tube bushing. To protect the propeller shaft from the corrosive effects of sea water in the area of ​​the stern tube, it has a bronze lining 17 or is protected with a special coating.

Bearings are mounted in the stern tubes - they absorb the forces from the propeller and shafting. For the manufacture of stern tubes, steel is used, less often gray cast iron grade SCh 18-36. They can be manufactured welded or inset. In the first case, the pipe is connected by welding to the stern post, the flanges of the ship's hull frame and the afterpeak bulkhead; in the second, it is inserted into the ship's hull from the stern or bow and secured. Insert pipes are manufactured cast, welded-cast or forged-welded. The connection between the stern tube and the stern post is overwhelmingly cylindrical along its length, and in some cases it is conical. The wall thickness of the stern tube must be at least (0.1-0.15) dr, where dr is the diameter of the propeller shaft along the lining.

In general, the stern stem, stern tube, hull and reinforced stern bulkhead should form a single, well-bonded, rigid structure. The insufficient rigidity of this unit, the lack of a rigid connection between the pipe and the flanges of the set, and the presence of weakened fits in the connections of the stern tube with the stern stem do not ensure reliable and trouble-free operation of the stern tube devices and contribute to increased vibration of the stern part of the vessel.

Sealing glands are an important component in the stern tube device. Experience in operating stern tube devices on large-tonnage vessels shows that the most reliable designs in operation are those that provide not only rigidity of the unit, but also a reliable gland seal that prevents sea water from entering the vessel's hull.
In this case, preference should be given to such stuffing box devices that house both the main and auxiliary stuffing box, making it possible to break it afloat without trimming. The stuffing box device can be installed in the bow of the stern tube, as shown in Fig. 1, or have a remote housing.

Rice. 2. Propeller shaft seals

The remote oil seal of the stern tube (Fig. 2, a) consists of a housing 4, which is attached to the flange of the afterpeak bulkhead using studs 7. Inside the oil seal housing there is a packing 3, which is sealed by a pressure sleeve 6 using nuts 5. The auxiliary oil seal can be sealed with a special brass ring 1, the axial movement of which is ensured by simultaneous rotation of three brass screws 2.

The design of a remote, separately fixed gland is irrational, as it overloads the stern tube device and the gland itself with additional loads due to misalignment of the axial gland packing and the shaft.

The seal design shown in Fig. 1 is widely used on ships. 2, b. A separate stuffing box 5, together with packing 4, is completely recessed into the stern tube 3, thereby increasing the rigidity of the seal and improving the operation of the stuffing box assembly. Uniform compression of the oil seal is carried out by rotating one of the six running gears 1, interconnected by a gear 2.

In the design considered, as in many others, auxiliary seals are not provided and, therefore, the possibility of breaking the seal afloat without trimming the vessel is excluded. In this case, the “Pneumostop” seal (Fig. 3) of the Kyiv-type icebreaker, which is installed in the aft part of the stuffing box, is of interest.
A water distribution ring 2 is inserted into the body 1 of the bow stern tube until it stops, which is sealed with two rubber rings 5 ​​and locked with screws 9. The water distribution ring has a groove to accommodate a rubber ring 3 (pneumatic stop) with a bronze inner ring of stiffness 4.
The pneumatic stop is secured with a cover 8 and bolts 7, after which there is a space for stuffing the oil seal. If it is necessary to stop the access of water into the housing, it is necessary to supply air under pressure through channel 6 in the body of the stern tube bushing inside the shaped rubber ring of the pneumatic stop, which will compress the shaft. During normal operation, the gap between the pneumatic stop and the propeller shaft is within 3-3.5 mm, thereby preventing their contact.

Gearboxes are devices that allow you to lower or increase the engine speed of a ship model, as well as tell the propellers the desired direction of rotation. Gearboxes are installed in the hull of ship models between the engine and the propeller. Most of the engines for the models are high-speed. Therefore, they need gearboxes to reduce the speed and to impart rotation to several screws.

For the manufacture of gearboxes, cylindrical gears are usually selected from various instruments, telephone dialers and clock mechanisms, having previously calculated the required gear ratio.

Gear ratio i shows how many times it is necessary to increase or decrease the number of revolutions at the output of the gearbox. If you need to reduce the speed in i times, then the number of teeth of the drive gear Z1(the shaft of which is connected to the engine) must be in i times less than that of the driven gear Z2(the shaft of which is connected to the shaft

propeller), i.e.:

If you need to increase the number of revolutions, then do the opposite. Thus, the number of revolutions of the driven gear of the gearbox will always be greater or less than the number of revolutions of the drive gear by the same factor as the number of times the drive gear has fewer or more teeth.

Rice. 108. Three-stage gearbox.

Sometimes it becomes necessary to make a gearbox with a very large deceleration, for example, for a clew winch for shifting sails on a radio-controlled yacht model. In this case, a multi-stage gearbox is made, i.e., from two or three pairs of gears. A worm gear is also used for this.

To determine the total gear ratio of such a gearbox, do this. First, determine the gear ratio of each pair of gears or worm gear separately, and then multiply them together to obtain the total gear ratio i. In Fig. 108 shows a general view of a three-stage gearbox, consisting of one worm gear and two pairs of spur gears. The total gear ratio of such a gearbox is i will be equal to: i1i2i3.

One of the most important quantities in gears is their engagement modulus m. The engagement module is the length in mm per one gear tooth along the diameter of the initial circle, numerically equal to the ratio of the diameter of this circle and the number of teeth. Only gears with the same module provide normal engagement and can be used in the gearbox.

Thus, when selecting ready-made gears, their modules must first be determined. If they are the same, they will work in pairs. To determine the module of a spur gear, you can use the following relationship:

Where d- outer diameter of the gear;

Z- number of gear teeth.

When manufacturing gearboxes, one should strive to use small-module gears, i.e. gears that have a larger number of teeth with the same diameter. The use of fine-module gears reduces friction losses, noise in the gearbox and improves smooth operation. The values ​​of the engagement module are standardized. For the manufacture of gearboxes for ship models, gears with a gearing module of 0.5 are most suitable; 0.6; 0.7; 0.8; 1.0; 1.25 and 1.5 mm. The greater the engine power, the larger the gearing module the gears for the gearbox are taken from. Thus, gears with a meshing module of 1.25 and 1.5 can be recommended for the manufacture of gearboxes only for internal combustion engines (Fig. 109).

Rice. 109. Internal combustion engine with gearbox.

Gearboxes made with such gears for an electric motor will be very “rough” and have large losses. For them, it is better to use gears with meshing modules: 0.6; 0.7 and 0.8. The use of gears made of different metals, such as steel and brass, also helps to reduce gearbox noise and improve the smoothness of its operation. The losses in the gearbox will be even smaller and the noise of its operation will be reduced if it is placed in a box filled with machine oil, and it will be quite enough if one of the gearbox gears is immersed in it by only 3-4 mm.

Rice. 110. Gearbox diagrams.

Fig. 111. Marking the side plate of the gearbox.

The manufacture of the gearbox begins with the manufacture of side plates. They are cut out of sheet brass or steel 1.5-2 mm. The plates must be well straightened on a flat metal plate with a wooden hammer, then folded together, clamped with a clamp or in a hand vice and drill 3-4 mm holes in the 4 corners, depending on what bolts they will be connected with. Next, both plates must be connected with two bolts (at opposite corners) and processed with a file along the drawn contour.

Now make precise markings of the positions of all gears on one of the side plates of the gearbox. Let us assume that a gearbox will be manufactured to reduce the number of revolutions using two screws. Then you need to draw two mutually perpendicular lines with a metal scriber - a horizontal line (A1 A2) at the level, depending on the diameter of the gear, and a vertical line (B1 B2) in the middle of the plate (Fig. 111). From the point of intersection of these lines (O), it is necessary to set aside along a horizontal line the centers of the driven gears - 001 and 002. The distance between these points O1O2 should be equal to the distance between the centers of the propeller shafts of this model.

Rice. 112. Installation of sliding bearings.

Rice. 113. Bushings for ball bearings.

Having marked the centers of all circles, drill holes in both plates for sliding bearings or ball bearings. Then the plates are separated and sliding bearings turned from bronze on a lathe are pressed into their holes (Fig. 112), or ball bearings are installed in special bushings or liners (Fig. 113). The best material for bushings is aluminum or brass.

They are attached to the side plates of the gearbox using three screws (Fig. 114). When turning bushings (liners) for ball bearings, it is necessary that the diameter “A” exactly matches the diameter of the outer race of the ball bearing; the race must fit tightly into place. Dimension “B” should be equal to the height of the ball bearing race, the thickness of the sleeve walls is 2.0-2.5 mm, and the base is 3.0-3.5 mm.

Rice. 114. Fastening gears to the axle.

The axles for the gears are turned from steel on a lathe. They should fit tightly into the center holes of the gears. If the gears have cylindrical projections, then they can be attached to the axles using a pin (Fig. 114, A). If there are no protrusions on the gear, the axles are machined with a shoulder (flange) and the gears are attached to it with screws or rivets (Fig. 114, B). When manufacturing axles, it is necessary that the “H” dimension is the same for all axles, and the gears are located symmetrically with respect to them.

In Fig. 115 shows the assembled gearbox. Its side walls can be fastened with studs with shoulders and threads at the ends, or with simple bolts, but with spacer tubes placed on the bolts.

Rice. 115. Gearbox assembled.

On ship models, internal combustion engines are installed on bases (foundations) made of wood, metal, or a combination of both (Fig. 116).

Electric motors are usually mounted on wooden bases (pillows) or screwed to a reinforced bulkhead of the model body. Sometimes directly to the gearbox, and the latter to the base, glued into the model body (Fig. 117).

Rice. 116. Foundations for internal combustion engines.

Propeller shafts are made of bar steel with a diameter of 3-6 mm, depending on the diameter of the propeller and engine power. At one end of the shaft, a propeller with a fairing is installed on the thread, and at the other, a device for connecting the shaft to the engine or gearbox. Very often, bicycle spokes or motorcycle wheel spokes are used to make propeller shafts.

Rice. 117. Installation of electric motors.

The propeller shaft is inserted into the stern tube, which is a metal tube with an internal diameter of 4-8 mm, at the ends of which brass (bronze, fluoroplastic) bushings (bearings) with an internal diameter corresponding to the diameter of the propeller shaft are pressed (Fig. 118, A). In order to reduce friction, very often ball bearings are inserted into the sternwood, which are pressed into a special bushing, tightly fitted onto the stern tube and soldered with tin (Fig. 118, B).

Rice. 118. Stern tubes: A - with brass second-plastic bushings; B - with ball bearings; B - with stuffing box for model submarines.

To fill the deadwoods with grease, a short (30-40 mm) piece of tube with a screw is soldered at one end (located in the model body) with a screw to tighten the grease as it is consumed. For model submarines, the deadwoods are made completely impenetrable. For this purpose, a bronze (brass) bushing (bearing) is deepened into the stern tube by 8-12 mm and soldered through a specially drilled hole in the stern tube. Part of the free space between the shaft and the deadwood is filled with twine or harsh threads soaked in grease. This filling is compressed with a second sleeve and soldered (Fig. 118, B).

Rice. 119. Connection of engines with propeller shafts.

The deadwoods are installed on the model so that, if possible, they are parallel to the centerline plane and the structural waterline of the model and provide a gap between the propeller and the model hull of at least 0.12-0.28 of the propeller diameter.

If the diameter of the propeller does not allow these conditions to be met, then the deadwoods have to be installed at a slight angle relative to the propeller and with an inclination to the waterline plane, and on high-speed steerable models this is generally inevitable. It must be remembered that both the shaft opening and their tilt by more than 12° greatly reduce the efficiency of the propeller. Therefore, on high-speed cord and radio-controlled models, brackets with a cardan are used to ensure the horizontality of the propeller shaft.

Rice. 120. Shaft joints.

The connection of engines with propeller shafts and gearboxes can be varied. The simplest connection between the engine and the propeller shaft is made using a spring, a rubber tube, bent hooks on the shafts themselves, brackets and simple clutches (Fig. 119). This connection is usually made on small models with low-power electric motors (about 5-10 5t) and rubber motors.

Rice. 121. Connection of gearboxes to the engine: A - articulated, with a roller; B - articulated, flexible roller.

The most common and reliable connection of engines of any power with gearboxes and propeller shafts is a swivel joint (Fig. 120). This design allows large loads on the shaft, and also does not require special alignment of the engine or gearbox with the propeller shaft.

Intermediate shafts between the gearbox and the electric motor can be made from a steel rod with a diameter of 4-6 mm (Fig. 121, A) or from a flexible shaft, for example from a car speedometer. You can make such a roller yourself. To do this, 1-1.5 mm thick OBC wire is wound tightly, turn to turn.

Ball ends are turned out of steel on a lathe, inserted into the spring on both sides (Fig. 121, B) and soldered with tin.