Paper pinwheel. Paper propeller

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 we need two propellers of different directions of rotation, or if we need 3-4 bladed propellers. All this can be solved if there is reasonable approach and simple 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 a 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 The number 3.14, known since school years....

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 model knife and sandpaper, but if you need a screw from hard wood like birch or beech, then 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. The lower part of 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, acranoplanes, microplanes and microgyroplanes, various fan installations and other machines cannot operate without a 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 they are easiest to make 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 tree 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 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 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, after final processing have a very beautiful appearance.

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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 apply center lines, outline the side view of the template (Fig. 3-B) and remove excess wood, 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 The propeller blades are 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 solid wood, its diameter must correspond to the diameter of the hole in the screw 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 is determined to match the blade to the profile templates. 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 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.

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 by various reasons: sometimes due to various specific gravity butt and top parts the bar from which the screw is made, or different densities of layers, local nodularity, etc.

How to be in this case? It is impossible to adjust the blades according to weight by cutting off a certain amount of wood from heavier ones. 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 appeared in Lately 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- so-called “chemical-hardening” parquet varnish. It holds up well on pure wood, and on the painted surface, giving it an elegant look and high mechanical strength.

Cheerful summer game- paper pinwheel in hands. And also development fine motor skills for first-graders. Or rather, already second graders!

First grade is over!

Ahead summer holidays. Textbooks have been put away for long-term storage throughout the summer, and old notebooks are no longer needed.

So let's make great toys from old, no longer needed math notebooks. After all, the first grade consists of special notebooks with large squares. Let's color them and make funny pinwheels that will be so fun to run down the street with.

So let's begin...

Step 1.

We take ordinary leaves from a math notebook for the first grade, that is, in a large square.

(You can do small ones, but then you’ll have to paint a lot more time).

Let's count the cells on the shorter side! (We count together with someone more mature or older).

Then mark the same number of cells on the other side and cut off the extra ones.

You will get a square!

That's how many exercises for a first-grader at once.

Using colored pencils, color the cells one at a time to create an ornament. It's about the same as in this photo.

Step 2.

Fold the leaf diagonally.

Unfold and fold along the second diagonal.

Let's expand.

We make cuts along the folds almost to the middle.

For those who don’t understand, look at the photo next to it!

Step 3.

Take the corner and bend it towards the middle.

Holding the tip with your finger, bend the second corner, then the third and fourth.

Step 4.

We take the button.

But it’s better not an ordinary stationery one, but in the form of a needle with a handle tip.

We pierce it in the middle so as to pierce all four curved ends and the leaf itself.

Many technical devices invariably require a propeller or, as it is otherwise called, a propeller. There are different goals, and for each you should choose a specific technology and strategy. If you are interested in how to make a weather vane with a propeller with your own hands, then this article is especially for you.

Which material to choose

What the screw will be made of should be chosen depending on its further purpose. For example, solid bars are ideal for making propellers intended for powerful engines (about 15-30 hp)

If you consider yourself experienced craftsman, then a blank made of aircraft plywood with a large number of layers is suitable for you. But amateurs should not start with it, because this specimen is very fragile and can form uneven surfaces.

Instructions

So, how to make a propeller with your own hands? The process of creating a propeller looks like this:

First you need to work on the templates, namely: 1 template for the top, 1 for the sides and 12 templates for the blade in profile.
Plane the screw blank according to the dimensions on all four sides and draw the axis lines and contours of the side view template.
Remove excess wood. First you do this with a hatchet, and then with a plane and rasp.
Now place the blade template on the workpiece and secure it with a nail in the center of the sleeve for a while, then trace it with a pencil.
Rotate the template 180° and trace the second blade. Excess wood can be removed using a fine-tooth saw. This work should be done carefully and not in a hurry.
Remove the wood without haste, making small and short cuts.
The screw must be brought to readiness using a plane and rasp and checked in the slipway.
In order to make a slipway, you need to look for a board that is the same length as the screw size, and also allows its thickness to make transverse cuts of 2 cm in order to install templates. To make the central rod of the slipway you will need solid wood. And its diameter should be the same as the diameter of the hole in the screw hub. The rod should be glued to the surface of the slipway at an angle of 90°.
Put the propeller on and see how much wood needs to be cut to get the blades to fit the profile templates.
Once the bottom surface of the screw begins to match the templates, you can begin finishing the top surface. This operation is very important, since the quality of the resulting screw is based on it.

For beginners, it is not uncommon for the blades to not match in size. For example, one turned out thinner than the other. But to make the correct propeller, you will have to achieve equal size by reducing the thickness of the other blade. Otherwise the propeller will not have balance. Small mistakes can be easily corrected. For example, stick small pieces of fiberglass or smear with small sawdust mixed with epoxy resin.

Prop Balance

The already made screw needs to be balanced. That is, to ensure that the weight of the blades matches. Otherwise, when the screw rotates, shaking will occur, leading to serious consequences - all the most important components of your device will be destroyed.

But in practice there are often cases when skilled craftsmen, who do not wonder how to make a propeller, the weight of the blades varies. And this is even if all the manufacturing nuances are observed! There are many explanations for this: different specific gravity of the various components of the block from which the screw is made, different densities layer and many other reasons.

But there is a way out of this situation. It is necessary to adjust the propeller blades according to the weight. True, there is one “but” here.

Finally

So how do you make the right propeller? Under no circumstances should wood be cut from a heavier blade. Just the opposite - you need to weigh down the smaller blade by riveting in lead.

Here is the answer to the question of how to make a propeller if the propeller does not move during balancing. We strongly recommend that you follow all personal safety measures. A propeller is, first of all, an object that quickly rotates around its axis, which means it can potentially be dangerous. If you are trying to figure out how to make a propeller, then make sure that safety is observed.

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.

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.

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.