Homemade propellers for airplanes with your own hands. Air propeller. Prices for different types of weather vanes

Many owners are trying to find a highlight for the exterior of their home, but there are not many such devices. A weather vane is ideal for this. It simultaneously performs both practical and aesthetic functions.

Features of a weather vane with a propeller

This device can be of different shapes, most often the weather vane has the shape of a domestic or wild animal, an angel, fairy tale hero, airplane.

A weather vane is not only a functional device, but also a decoration for the roof of a house.

Selecting material for making a weather vane

The main criterion when choosing material for a weather vane should be the ultimate purpose of its manufacture. But, despite this, it is recommended to choose the material that will make the structure a decoration of your home for a long time. A weather vane can be made from almost any material, but each of them requires different instruments and equipment.

Wood weather vane

Quite light and easy to use construction material, which does not require specific tools and skills. Suitable raw materials for a weather vane High Quality. Before use, it is recommended to impregnate the wood with mixtures to protect it from dampness and harmful insects. However, such a product will not last long.

This material is durable and resistant to any mechanical stress. Most often, black or stainless steel is used for weather vanes. The second type is resistant to corrosion, has a long service life, but still requires proper maintenance and timely repairs. This can be a problem because the weather vane is installed in a place where repairs are quite difficult.

Steel has high anti-corrosion properties, which is why a steel weather vane can most often be seen on the roof

It is a durable metal that can even withstand hurricanes. It's quite easy to work with. Additionally, a layer of silver can be applied to the surface of a copper weather vane, for which reagents that are used in making photographs are ideal. This metal It is resistant to corrosion, so the product can be exposed to rain for a long time and will last a long time without repair.

Copper is highly resistant to weather conditions, so it is best suited for making weather vanes.

Plastic structures

Plastic is modern material, characterized by high strength and resistance to sun rays. Another advantage is ease of processing. Plastic products can be sawed, glued, soldered, and the properties of the material do not change.

The plastic weather vane can be made in any color; it is highly durable and resistant to sunlight

Plywood

To make a weather vane, only multi-layer waterproof plywood is suitable, but you need to be prepared for the fact that such a product will not last long. Dyeing the material will help artificially increase its service life, but for a very short period of time.

To make a weather vane, you can only use multi-layer waterproof plywood

Tools for making a weather vane

The list of tools for making this device is quite simple:

metal scissors;
hacksaw or saw;
sandpaper of different fractions;
electric drill;
Bulgarian;
office tools, for example, ruler, pencil, glue.

Basic elements of a weather vane

Regardless of what shape your weather vane will be, it must contain certain elements, the main ones being an axis and a flag with a counterweight.

Vane body and axis

The body serves as a support for the entire structure. Both steel and brass pipes with a diameter of 1 inch are suitable for its manufacture. The body has a strictly vertical axis - a rod, usually made of steel reinforcement.

The main function of the support rod is to hold the windmill. The diameter of the reinforcement is about 9 mm, this is enough to withstand strong winds and any other mechanical load that will act on the weather vane.

The weather vane body is the support of the entire structure

Flag with counterweight (wind vane)

The main part of the device located on the vertical axis. The flag shows which direction the wind is blowing. The counterweight serves to balance the flag and is located on the opposite side. The main difficulty in the manufacture of this element is that the flag and the counterweight must be located evenly on both sides of the axis, that is, have the same mass.

Of the entire structure, it is the weather vane that is of artistic value. An experienced craftsman is able to make a part of any shape without disturbing the balance between the flag and the counterweight.

When making a weather vane, it is important to maintain an even distribution of mass on both sides of the axis

Protective cap

The protective cap has the shape of a circle or a cone and is located on the axis of the weather vane, most often directly above the body. Its main function is to protect the housing and bearings from moisture and dirt.

Rose of Wind

A cardinal direction indicator consisting of two rods crossed at an angle of 90°. As a rule, the rods are attached to the top of the lid in a stationary state. At the ends of the pointer, letters are installed to indicate the cardinal directions. To capture an element in correct position, you need to use a compass.

To install cardinal direction indicators in in the right direction, you need to use a compass

Bearings

They are located inside the body and ensure free movement of the supporting rod under gusts of wind. The internal diameter of the parts is 9 mm.

Fasteners

The choice of fasteners depends on the material used and the method of fastening. These can be corners, overlays, bolts, rivets.

Propeller

It helps determine wind speed. You can make the propeller yourself from plastic and wood or use ready-made parts.

It is the airplane with the propeller that looks most organic, since this detail is also present in the original design. And it’s much easier to model this shape than others.

The plane is ideal for making a weather vane with a propeller

Drawing of an airplane weather vane with a propeller

The weather vane is usually located on the roof, so high aesthetic demands are placed on it - according to him appearance they will judge not only the taste of the owner of the house, but also his wealth. Therefore, it is very important to design the structure correctly, while showing maximum imagination and creativity. The drawing of the future model should be as detailed and accurate as possible.

The drawing of the future aircraft model should be as detailed as possible and with exact dimensions

Step-by-step instructions for making an airplane weather vane

This device will become the hallmark of the home only if the element is properly made and installed.

Metal weather vane

It is performed in the following sequence:

Cut a pipe 120 mm long. Make small holes in it for fastening to the support with rivets or bolts. The holes must first be tapped.
Insert bearings from each end into the pipe, securing with welding. Additionally, the bearings can be fixed by heating the pipe into which the bearing must be inserted. After the pipe has cooled, the bearings will sit quite firmly in it. Fill the pipe itself with grease.
Bearings help the weather vane to easily rotate around its axis
Close the top of the pipe with a cap, which can be a plastic plug. Now you need to seal this place with insulating tape. A layer of felt gland must be laid between the cap and the body.
Now you can start making the weather vane. You need to make a drawing on paper, which then needs to be transferred to a steel sheet. Remember that the dimensions of the aircraft must be proportional to the body parameters. It is recommended to make a product with a length of 400–600 mm and a height of 200–400 mm.
It is very easy to cut steel sheets with special metal scissors
After the airplane figurine is ready, you need to attach it to the supporting rod using clamps or welding. The last stage is the installation of the propeller. It must be installed on a weather vane or on a supporting rod. In the case of an airplane, it will look more harmonious on the weathervane. For fastening, it is recommended to use a bolt, which must be placed between two washers. To reduce the noise of the weather vane, it is recommended to place it on a bearing.

Weather vane made from plastic bottles

You can make an airplane weather vane from plastic bottles. To do this you need:

Collect empty containers and wash them thoroughly. For a weather vane in the shape of an airplane, 4 bottles are enough. Cut off the top part of two bottles with the cork halfway. As a result, you should have 2 cut tops with a cork and 4 bottoms, the height of which is 5 cm.
You need to cut off the top and bottom of the bottle
On each bottom at an angle of 45°, make cuts in the form of burrs, which will serve as fasteners.
The bottom of the bottle must be cut into strips
Now you need to work with the top parts of the bottles. You need to unscrew the plug in which to make holes for the axle. This can be done with an awl or a hot rod. Screw this plug back. Leave one top part of the bottle without a cork.
Use an awl to make holes in the plugs for the axle.
Now you can start assembling the weather vane. The two upper parts are connected with cut surfaces facing each other. This process is reminiscent of collecting nesting dolls. It is necessary to attach the bottoms with cuts, placing them around the body in one direction. Now you need to thread a rod or metal rod through the bottom holes of the bottle, and place the bottle cap on top of it. That's it, the plane's weather vane is ready. Install it in a suitable place.
A weather vane made from a plastic bottle does not look very aesthetically pleasing, but it performs its functions effectively

Video: weather vane airplane made from plastic bottles

For a homemade weather vane, you can use scraps of plywood. In addition to this material, you will need:

nails or screws;
flat beads - 3 pieces;
special glue for plywood;
small wooden beam OK;
protective paint.

All work on the manufacture of a weather vane from this material is carried out in the following order:

Video: DIY wooden weather vane with a propeller

The propeller can be made from any material

The manufacturing process is as follows:

Prepare a wooden block with a side of 5 cm. Draw diagonals on each face of the cube and mark the place where they intersect. Drill a through hole in one of the planes.
On a sheet of tin, mark segments equal to the width of the bar. Cut strips measuring 15x5 cm. There should be 4 such strips. Process the edges of each strip with a sharpening machine.
Each strip is roughly divided into 5 parts. Bend one of them with pliers at a right angle. As a result, you should have four L-shaped blades. Place each piece diagonally on one side of a wooden cube with a hole.
The protruding parts of the sheet must be cut off in such a way that the part that will be fixed is sharp-angled.
Now the blades need to be fixed with screws in two places.
Sharpen another wooden beam at one end into a cone, and attach the cube with blades to this side using a nail. This propeller can be installed on a pre-made weather vane.

Video: DIY tin propeller

Remember that when installing a weather vane on the roof, you need to ensure that the waterproofing of the latter is not damaged, otherwise leaks cannot be avoided. It is also not recommended to install a weather vane on a ridge or chimney pipe. Incorrect installation may also cause the device to make a lot of noise, scaring away birds and irritating others.

Probably everyone has come across a situation when the required screw is either not on sale, or the screws are needed tomorrow, but the package is stuck somewhere... Then a completely reasonable solution comes to mind - shouldn’t I make the screw myself?

Usually in this case there is only one reason that stops a healthy idea: how to get a screw with the given characteristics?

In fact, everything is quite simple - it does not require either complex calculations or highly complex equipment. As usual, a little common sense, a pencil, a ruler, knowledge of school geometry and a little straight hands are enough.

This article will discuss exactly this: how to correctly calculate the geometry of a screw with given parameters and how to manufacture it. Usually you don’t need much time - 1-2 hours for graphical calculations + 2-3 hours for making the screw itself.

Fig 1. Propeller theory. Screw pitch.

A similar situation arises if two screws are needed different directions rotation, or if we needed 3-4 bladed propellers. All this can be solved with a reasonable approach and the simplest tools.

Let's look carefully at Fig. 1. What do we see there? Here's what:
- A screw with radius R travels a distance H in the air in one revolution. R is the radius of the screw (from the axis of rotation to its end), H is the pitch of the screw if it does not slip in the air, but is screwed into it like a screw in a tree. These are actually the two main parameters of wine. D = 2xR and H - propeller pitch.

Usually a person knows well which screw he needs for the model... If not, then this is a topic for separate conversation. For now, we will assume that we have a good idea of what kind of screw we need: i.e. we know the parameters D and H, or R and H...

To learn the geometric dimensions of the required screw, if we know the R and H of the screw, the easiest way is to use a geometric calculation. We look at Fig. 2. Horizontally, we plot on some scale (I have (2:1 for greater accuracy) the radius of the screw. Vertically, the distance that the screw will travel in one revolution without slipping is H/2xPi, where Pi is known since school years number 3.14....

Figure 2. Determining the angle of inclination of the propeller profile.

Why exactly this and no other way - I will not prove here. Those who studied geometry well at school will immediately understand, but the rest need to either re-read the school textbooks or ask their questions during the discussion. A little lower is the side profile of the propeller. It was actually chosen solely from my experience in making simple screws. Everyone has the right to choose it quite arbitrarily. I chose the thickness of the screw at the butt (near the hub - 10 mm) and at the end - at the maximum radius - 2 mm. The purpose of this geometric calculation is to obtain the correct screw widths in the top view. Those. obtain the geometric dimensions of a screw with a diameter of 150 mm and a pitch of 100 mm... This is written down at the top right of the sheet..

See Fig. 2. To achieve this goal, we draw a straight line from the step point on the vertical coordinate to the required section (line 1). To begin with, I chose a section spaced from the axis of rotation by 37.5 mm = i.e. exactly in the middle of the designed screw. According to the lateral projection, the thickness of the screw in this place is 6.5 mm. Move this dimension up (operation 2) and draw a rectangle around the inclined line. It (the rectangle) gives us the width of the propeller blade in the top view - 14 mm. We move this measurement down (operation 3) and get the width of the screw in this section...

Figure 2. Determination of all inclination angles at all design points

Having carried out similar constructions for all 6 sections of the screw, we obtain the width of the screw at a distance of 12.5, 25.0, 37.5, 50, 62.5 and 75 mm. It is possible to construct a larger number of sections, but this will not add much accuracy. As a result, in Fig. 2, by circling the obtained screw widths at six points, we will obtain the profile of the screw in the top view.

We take a blank from suitable wood and mark it. First of all, we give it the thickness and length of the required screw - 10 mm x 150 mm. The width of the workpiece should be slightly larger than the width of the screw at its widest point - 15 mm.

Figure 3. Template and marked screw blank

We apply markings to the side view (the thickness at the butt is 10 mm and 2 mm at the end of the blade) and to the top and bottom views using a manufactured template.

Fig. 4 Top view of the marked workpiece.

Fig 5 Side and top view of the workpiece

In Fig. 4-5 you see the marked workpiece. First of all, using a file or knife, remove the excess wood in the side view. You can see what should happen in Fig. 6. If you are making a screw from fairly soft wood (linden, balsa), then it is enough to use a modeling knife and sandpaper, but if you need a screw from hard rocks like birch or beech, it is better to use a bastard file (with a large notch) or a fine-toothed rasp.

Figure 6. Balancing workpieces

Immediately after giving the workpiece the correct side profile, it is necessary to balance the workpiece. I usually do it this way: I screw a thin drill (0.5-1.0 mm) into the center of rotation and place the drill on two vertical supports. In this case, these are two identical glasses. (Figure 6.).
Then, by sanding, I achieve the same weight for both future blades.

Fig 7. Marking of the front section

After the side view is profiled, we move on to marking the hauls to obtain the desired fishing profile. In the top view - from the front (we are making a screw of normal rotation - counterclockwise) we mark a line passing through 2/3 of the width of the screw. See Figure 7.

Fig 8. Marking the sample of the rear part...

In the bottom (rear) view, draw lines spaced from the edge of the screw by approximately 1 mm. Bottom part the screw just sets the pitch (or the angle of inclination of the section)...

Fig 9 Selected rear part of the propeller.

Then we begin to remove excess wood with a knife or file, starting from the bottom (back) part of the screw according to the markings made. Having removed everything from behind (from below), we first sand the back part of the screw with coarse sandpaper (120-160), and then with fine sandpaper...

Figure 10. Selected front part of the propeller

Then we repeat the same for the front part of the screw. See Figure 10...
Having made sure that all excess wood has been removed, we carefully sand the entire propeller to give it the required profile - similar to the profile of the wing, i.e. rounded leading edge, maximum thickness approximately 30% of section width and sharp trailing edge. In the process of giving this profile, it is a good idea to constantly monitor the balancing of the screw being processed, as shown in Fig. 6.

Once both blades have acquired the desired shape and profile, as well as balancing, you can proceed to final stage- painting and varnishing. See Figure 11.

Figure 11. Balancing a varnished screw.

I usually paint the finished screw traditional black and then cover it with 2-4 coats of varnish. As a rule, I use classic enamel. Dries quickly and is easy to sand. During painting and varnishing, do not forget about balancing. See Figure 11.

The screws obtained in this way, in my opinion, are no worse than purchased plastic screws, which usually also require additional balancing. If you are more satisfied with screws made of carbon or glass-plastic, then using the screw made according to the method described above as a master model, you can make molds for screws from fiberglass....

In a completely similar way, you can easily make a screw of any diameter and pitch you need, as well as a reverse rotation screw - clockwise.

Moreover, having calculated and manufactured one blade of a two-bladed propeller, you can use it to make molds for three or 4-bladed propellers from glass-carbon-plastic, but this is a topic for a separate article...

Magazine "Modelist-Constructor"

Article from Modelist-Constructor magazine No. 1 for 1974.
Scan: Petrovich.

Snowmobiles, airboats, all kinds of hovercraft, akranoplanes, microplanes and microgyroplanes, various fan installations and other machines cannot operate without propeller(propeller).

Therefore, every technical enthusiast who plans to build one of the listed machines should learn how to make good propellers. And since in amateur conditions it is easiest to make them from wood, we will only talk about wooden propellers.

However, it should be taken into account that using wood (if it turns out to be successful) it is possible to make completely similar screws from fiberglass (by molding into a matrix) or metal (by casting).

Due to their availability, the most widespread are two-blade propellers made from a whole piece of wood (Fig. 1).

Three- and four-blade propellers are more difficult to manufacture.

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Rice. 1 . Two-bladed wooden screws made from a whole piece of wood: 1 - blade, 2 - hub, 3 - front flange, 4 - hub stud nuts, 5 - shaft toe castle nut, 6 - shaft, 7 - rear flange, 8 - studs.

MATERIAL SELECTION

What wood is best to make a screw from? This question is often asked by readers. We answer: the choice of wood primarily depends on the purpose and size of the screw.

Screws intended for engines of higher power (about 15-30 hp) can also be made from monolithic hardwood bars, but the requirements for the quality of wood in this case increase. When choosing a workpiece, you should pay attention to the location of the growth rings in the thickness of the block (it is clearly visible at the end, Fig. 2-A), giving preference to bars with horizontal or inclined layers, cut from the part of the trunk that is closer to the bark. Naturally, the workpiece should not have knots, crooked layers or other defects.

If it was not possible to find a monolithic bar of suitable quality, you will have to glue the workpiece together from several more thin planks, 12-15 mm thick each. This method of manufacturing propellers was widespread at the dawn of the development of aviation, and it can be called “classical”. For reasons of strength, it is recommended to use wood planks different breeds(for example, birch and mahogany, birch and red beech, birch and ash), having mutually intersecting layers (Fig. 2-B). Screws made from glued blanks have a very beautiful appearance after final processing.

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Rice. 2. Propeller blanks: A - from a whole piece of wood: 1 - sapwood part of the trunk, 2 - location of the blank; B - a blank glued from several planks into a rectangular package: 1 - mahogany or red beech; 2 - birch or maple.

Some experienced specialists glue blanks from multilayer aircraft plywood brand BS-1, 10-12 mm thick, assembling a package from it required sizes. However, we cannot recommend this method to a wide range of amateurs: veneer layers located across the screw, during processing, can form difficult-to-remove irregularities and deteriorate the quality of the product. The ends of propeller blades made of plywood are very fragile. In addition, in a high-speed propeller, a very large centrifugal force acts at the root of the blades, reaching in some cases up to a ton or more, and in plywood the transverse layers do not resist breaking. Therefore, plywood can be used only after calculating the root section area of the blade (1 cm2 of plywood can withstand about 100 kg of tearing, and 1 cm2 of pine - 320 kg). The screws have to be thickened, and this worsens the aerodynamic quality.

In some cases, the attack edge of the propeller is covered with a strip of thin brass, the so-called fitting. It is attached to the edge with small screws, the heads of which, after cleaning, are soldered with tin to prevent self-loosening.

PRODUCTION SEQUENCE

According to the propeller drawing, first of all, it is necessary to make metal or plywood templates - one top view template (Fig. 3-A), one side view template and twelve blade profile templates, which will be needed to check the propeller on the slipway.

The screw blank (block) must be carefully planed, observing the size on all four sides. Then the center lines and contours of the side view template are drawn (Fig. 3-B) and the excess wood is removed, first with a small axe, then with a plane and rasp. The next operation is processing along the contour of the top view. Having placed the blade template on the workpiece (Fig. 3-B) and temporarily secured it with a nail in the center of the sleeve, trace the template with a pencil. Then turn the template exactly 180° and trace the second blade. Excess wood is removed band saw, if it is not there, use a hand-held circular saw with fine teeth. This work must be done very accurately, so there is no need to rush.

The product took on the shape of a screw (Fig. 3-D). Now the most important part of the work begins - giving the blades the desired aerodynamic profile. It should be remembered that one side of the blade is flat, the other is convex.

The main tool for giving the blades the desired profile is a sharpened, well-set ax. This does not mean that the work being performed is “clumsy”: with an ax you can do miracles. Just remember the famous Kizhi!

The wood is removed sequentially and slowly, first making small short cuts to avoid chipping along the layer (Fig. 3-D). It is also useful to have a small two-handed shaving. The figure shows how you can speed up and facilitate the work of trimming the profile part of the blade by making several cuts with a fine-toothed hacksaw. When performing this operation, you must be very careful not to cut deeper than required.

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Rice. 3. Sequence of screw manufacturing: A - templates (top view and side view); B - marking the blank block according to the side view template; B - marking the workpiece according to the top view template; G - workpiece after processing according to templates; D - processing of blades along the profile (lower, flat part); E - processing of the upper, convex part of the blade.

After rough processing of the blades, the propeller is brought to condition using planes and rasps and checked in the slipway (Fig. 4-A).

To make a slipway (Fig. 4), you need to find a board equal in length to the screw and thick enough so that transverse cuts 20 mm deep can be made in it for installing templates. The central rod of the slipway is made of hard wood, its diameter must correspond to the diameter of the hole in the propeller hub. The rod is glued strictly perpendicular to the surface of the slipway. By placing the screw on it, the amount of wood that needs to be removed to match the blade to the profile templates is determined. When doing this job for the first time, you need to be very patient and careful. The skill is not acquired immediately.

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Rice. 4. Slipway and blade profile templates: A - installation of templates in the slipway; B - checking the blade being processed using templates and counter templates.

After the lower (flat) surface of the blade has been finalized according to the templates, finishing of the upper (convex) surface begins. The check is carried out using counter-patterns, as shown in Figure 4-B. The quality of the screw depends on the thoroughness of this operation. If it unexpectedly turns out that one blade is slightly thinner than the other - and this often happens with inexperienced craftsmen - the thickness of the opposite blade will have to be reduced accordingly, otherwise both the weight and aerodynamic balancing of the propeller will be disrupted. Minor flaws can be corrected by gluing pieces of fiberglass (“patches”) or applying small grease sawdust, mixed with epoxy resin(this mastic is colloquially called bread).

When cleaning the surface wooden screw the direction of the wood fibers should be taken into account; Planing, scraping and sanding can only be carried out “layer by layer” to avoid scuffing and the formation of rough areas. In some cases, in addition to cycles, good help When finishing the screw, glass shards may occur.

Experienced carpenters, after sanding, rub the surface with a smooth, well-polished metal object, pressing firmly on it. By doing this, they compact the surface layer and “smooth out” the smallest scratches remaining on it.

BALANCING

The manufactured propeller must be carefully balanced, that is, brought to a state where the weight of its blades is exactly the same. Otherwise, when the screw rotates, shaking occurs, which can lead to the destruction of vital components of the entire machine.

Figure 5 shows a simple device for balancing screws. It allows you to perform balancing with an accuracy of 1 g - this is practically enough for amateur conditions.

Practice has shown that even with very careful manufacturing of the propeller, the weight of the blades is not the same. This happens for various reasons: sometimes due to various specific gravity butt and upper parts of the block from which the propeller is made, or different densities of layers, local nodularity, etc.

How to be in this case? It is impossible to adjust the weight of the blades by cutting off a certain amount of wood from a heavier one. It is necessary to make the lighter blade heavier by riveting pieces of lead into it (Fig. 6). Balancing can be considered complete when the propeller remains motionless in any position of the blades relative to the balancing device.

Screw runout is no less dangerous. A scheme for checking a propeller for runout is shown in Figure 7. When rotating on an axis, each blade must pass at the same distance from the control plane or angle.

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Rice. 5. The simplest device for checking the balancing of the screw is using two carefully aligned boards and an axial liner.

Rice. 6. Balancing the propeller by riveting pieces of lead into a lighter blade: A - determining the imbalance using coins; B - embedding a piece of lead of equal weight on an equal arm (slightly countersink the hole on both sides); B - view of the lead rod after riveting.

Rice. 7. Scheme for checking a screw for runout.

FINISHING AND COLORING OF THE SCREW

The finished and carefully balanced screw must be painted or varnished to protect it from atmospheric influences, as well as to protect it from fuels and lubricants.

To apply paint or varnish, it is best to use a spray gun powered by a compressor at a minimum pressure of 3-4 atm. This will make it possible to obtain an even and dense coating, unattainable with brush painting.

The best paints- epoxy. You can also use glyphthalic, nitro- and nitroglyphthalic or the recently introduced alkyd coatings. They are applied to a previously primed, carefully puttied and sanded surface. Interlayer drying is required, corresponding to a particular paint.

The best varnish coating- the so-called “chemical-hardening” parquet varnish. It adheres well to both clean wood and painted surfaces, giving it an elegant look and high mechanical strength.

Find a design pattern. Try to find a suitable design template for the propeller. It is important to know the engine power, propeller diameter and rotation speed in order to select drawings and templates of a wooden propeller for such technical specifications. Find a template on the Internet or borrow a special book from the library. Some books have drawings of samples, which will do just fine.

Determine the number of blades. Most often, the propeller has two, three or four blades. Larger aircraft may use propellers with even more blades. The more powerful the drive motor, the more blades are needed to distribute the power evenly. Although, if you really want, you can make a propeller with three or four blades, still, if this is your first such experience, it is better to start with a simple propeller with two blades. The more blades, the higher the cost, weight finished product and time costs.

Determine the length of the blades. As with quantity, increasing blade length allows for more powerful engine. Also note that maximum length the blades are always limited by their distance to the ground. Measure the distance from the nose of the plane to the surface to get an idea of the limitations.

Aerodynamic profile. The propeller blade thickens near the motor shaft hub with a large angle of inclination, while the tip of the blade is always thin with a small angle of inclination. Determine the blade width and angle of attack. The propeller blades are attached to the hub at an angle similar to the threads on screws and screws.

Correct bending of the propeller blades. The propeller blade resembles a curved wing. Thanks to the bend, the propeller pushes air or water more efficiently. The tips of the blades always move much faster than the hub on the shaft. The blades must be bent so that the propeller maintains the same angle of attack along the entire length of the blade. Use a special calculator to calculate the required slope.

Select blade material. The more durable a wooden propeller is made, the better it will cope with aircraft vibrations. Use durable but lightweight wood such as maple or birch. When choosing wood, pay attention to the grain texture. Straight and evenly distributed fibers will help balance the propeller.

Use 6 to 8 boards, 2 to 2.5 centimeters thick and about 2 meters long. Spare boards won't hurt either. The more layers, the stronger the propeller will be, even if each layer is very thin. To save time, you can contact material suppliers who produce multi-layer plywood.

Magazine "Modelist-Constructor"

Article from Modelist-Constructor magazine No. 1 for 1974.
Scan: Petrovich.

Snowmobiles, airboats, all kinds of hovercraft, acranoplanes, microplanes and microgyroplanes, various fan installations and other machines cannot operate without a propeller.

Due to their availability, the most widespread are two-blade propellers made from a whole piece of wood (Fig. 1).

Three- and four-blade propellers are more difficult to manufacture.

..
Rice. 1 . Two-bladed wooden screws made from a whole piece of wood: 1 - blade, 2 - hub, 3 - front flange, 4 - hub stud nuts, 5 - shaft toe castle nut, 6 - shaft, 7 - rear flange, 8 - studs.

MATERIAL SELECTION

What wood is best to make a screw from? This question is often asked by readers. We answer: the choice of wood primarily depends on the purpose and size of the screw.

If it was not possible to find a monolithic bar of suitable quality, you will have to glue the workpiece from several thinner boards, each 12-15 mm thick. This method of manufacturing propellers was widespread at the dawn of the development of aviation, and it can be called “classical”. For reasons of strength, it is recommended to use planks made of wood of different species (for example, birch and mahogany, birch and red beech, birch and ash), having mutually intersecting layers (Fig. 2-B). Screws made from glued blanks have a very beautiful appearance after final processing.

Some experienced specialists glue blanks from multilayer aircraft plywood of the BS-1 brand, 10-12 mm thick, and assemble a package of the required size from it. However, we cannot recommend this method to a wide range of amateurs: veneer layers located across the screw, during processing, can form difficult-to-remove irregularities and deteriorate the quality of the product. The ends of propeller blades made of plywood are very fragile. In addition, in a high-speed propeller, a very large centrifugal force acts at the root of the blades, reaching in some cases up to a ton or more, and in plywood the transverse layers do not resist breaking. Therefore, plywood can be used only after calculating the root section area of the blade (1 cm2 of plywood can withstand about 100 kg of tearing, and 1 cm2 of pine - 320 kg). The screws have to be thickened, and this worsens the aerodynamic quality.

PRODUCTION SEQUENCE

The screw blank (block) must be carefully planed, observing the size on all four sides. Then the center lines and contours of the side view template are drawn (Fig. 3-B) and the excess wood is removed, first with a small axe, then with a plane and rasp. The next operation is processing along the contour of the top view. Having placed the blade template on the workpiece (Fig. 3-B) and temporarily secured it with a nail in the center of the sleeve, trace the template with a pencil. Then turn the template exactly 180° and trace the second blade. Excess wood is removed using a band saw; if there is none, use a hand-held fine-toothed circular saw. This work must be done very accurately, so there is no need to rush.

After rough processing of the blades, the propeller is brought to condition using planes and rasps and checked in the slipway (Fig. 4-A).

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Rice. 4. Slipway and blade profile templates: A - installation of templates in the slipway; B - checking the blade being processed using templates and counter templates.

After the lower (flat) surface of the blade has been finalized according to the templates, finishing of the upper (convex) surface begins. The check is carried out using counter-patterns, as shown in Figure 4-B. The quality of the screw depends on the thoroughness of this operation. If it unexpectedly turns out that one blade is slightly thinner than the other - and this often happens with inexperienced craftsmen - the thickness of the opposite blade will have to be reduced accordingly, otherwise both the weight and aerodynamic balancing of the propeller will be disrupted. Minor flaws can be corrected by gluing pieces of fiberglass (“patches”) or applying fine sawdust mixed with epoxy resin (this mastic is colloquially called bread).

When cleaning the surface of a wooden screw, the direction of the wood grain should be taken into account; Planing, scraping and sanding can only be carried out “layer by layer” to avoid scuffing and the formation of rough areas. In some cases, in addition to cycles, glass shards can be a good help in finishing the screw.

BALANCING

Figure 5 shows a simple device for balancing screws. It allows you to perform balancing with an accuracy of 1 g - this is practically enough for amateur conditions.

Practice has shown that even with very careful manufacturing of the propeller, the weight of the blades is not the same. This happens for various reasons: sometimes due to different specific gravity of the butt and upper parts of the block from which the screw is made, or different densities of layers, local nodularity, etc.

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Rice. 5. The simplest device for checking the balancing of the screw is using two carefully aligned boards and an axial liner.

Rice. 7. Scheme for checking a screw for runout.

FINISHING AND COLORING OF THE SCREW

The finished and carefully balanced screw must be painted or varnished to protect it from atmospheric influences, as well as to protect it from fuels and lubricants.

The best paints are epoxy. You can also use glyphthalic, nitro- and nitroglyphthalic or the more recently introduced alkyd coatings. They are applied to a previously primed, carefully puttied and sanded surface. Interlayer drying is required, corresponding to a particular paint.

The best varnish coating is the so-called “chemical-hardening” parquet varnish. It adheres well to both clean wood and painted surfaces, giving it an elegant look and high mechanical strength.