How to make a spring-vacuum crossbow
The device of a spring-vacuum crossbow
Dear lovers of homemade weapons, today I want to present to your attention not regular crossbow, which uses mechanical tension of the shoulders to throw an arrow, but something of a completely different kind. Namely, a spring-vacuum crossbow that can be used not only for ground hunting, but also for underwater hunting. It is compact, convenient, allows you to hunt in dense vegetation, vacuum energy greatly increases the range and speed of the arrow. Diagrams of this weapon were found on the Internet.
First, let's touch on brief description crossbow devices. This weapon has the following main components and mechanisms: crossbow stock 1 (fig. 1; 3), shoulders, which are fixed motionless in the front part of the crossbow stock strictly perpendicular to its axis 2 (fig. 1; 2), rotating guides, bowstring straightening mechanism . In the lower part of the crossbow stock, blocks are fixedly fixed: receiving blocks 3 (Fig. 2), which are secured using an angle 4 (Fig. 2) to the underside of the shoulders. Moreover, the angle between this pair of blocks should be strictly ninety degrees. Guide blocks 5 (Fig. 2) fixed through the stirrup 6 (Fig. 1; 4) in front of the vertical plane of the crossbow arms. Another pair of blocks is bowstring 7 (Fig. 1; 2; 3), they are located at the edges of the crossbow shoulders. Through these outer blocks there passes a cable 8 (Fig. 1; 2; 4), which actually is the bowstring 9 (Fig. 1; 2). On the crossbow stock itself there is a special mechanism that holds the bowstring 10 (Fig. 1). Stops 11 are attached to the bottom of the bed; 12 (Fig. 3). Between them there is a pipe 13 (Fig. 3; 4; 5), in which the spring-vacuum mechanism is located.
Now let's see how this mechanism works. First, let's analyze the structure of this mechanism for compression. Inside the through pipe 13 (Fig. 3; 4; 5) there is a helical compression spring 14 (Fig. 4; 5) and a vacuum piston 15 (Fig. 4; 5). Two parallel cables 8 (Fig. 4; 5) are rigidly attached to this piston, which are threaded through a spring. At the end of the pipe there is a rubber gasket, the so-called emergency shock absorber 16 (Fig. 4; 5). There is also a fuse 17 (Fig.5).
In the sealed chamber of pipe 22 there is a pump 19 for pumping out excess air and changing the power of the weapon, plus a pressure gauge for the vacuum chamber 20, which shows what kind of rarefaction there is in the chamber, and an instant discharge valve 21, which serves to ensure the safety of the cocked weapon. When it opens, the pressure in the chamber will be equal to atmospheric pressure and a spontaneous shot will not occur.
As you can see from the description of the device, the weapon is quite serious and to make it yourself, you need to invest a lot of work and brains.
How does this unique weapon work?
When we pull the string 9 -> 9a (Fig. 1), the cables pull the piston back. The blocks begin to rotate, guiding the cable. At the same time, the volume of the vacuum chamber increases and, as a result of this increase, the vacuum of air in the chamber increases. The piston moves until it is blocked by the fuse.
To fire a shot, turn off the safety, the string 9 -> 9a (Fig. 1) is released and the spring begins to move the piston forward, which pulls the cables 8, the blocks, rotating, direct the cable, the string 9 -> 9a (Fig. 1) sharply straightens up and fires. Compressed air is released into the decompression hole located at stop 12. If the arms have a span of forty centimeters, and the bowstring has a working stroke of thirty centimeters, then the working stroke of the spring will be equal to seventeen centimeters.
Unfortunately, I was able to find though detailed diagrams devices of a vacuum-spring crossbow, but without any specific dimensions. Therefore, not every homemade person can make this weapon, but only those who have some technical knowledge and design thinking. Good luck in your endeavors.
Figure 1 - crossbow top view.
Figure 2 - front view of the crossbow.
Fig.3 - crossbow side view.
Figure 4 - crossbow view from below. (the pipe is not shown in the diagram)
Fig.5 - spring mechanism in operation with a compression spring
Fig.6 - spring mechanism in operation with a tension spring
Figure 7 - action of the mechanism using the operation of a vacuum chamber
1 - crossbow stock, 2 - crossbow fixed arms, 3 - receiving pair of blocks, 4 - corner, 5 - guide pair of blocks, 6 - stirrup, 7 - string-forming pair of blocks, 8 - cable, 9 - cable-string, 10 - mechanism bowstring hold, 11 - stop, 12 - stop, 13 - pipe, 14 - compression spring, 15 - piston, 16 - rubber emergency shock absorber, 17 - fuse, 19 - additional air pump, 20 - vacuum pressure gauge, 21 - instant valve discharge, 22 - sealed vacuum chamber
P.S.
The article is a rewrite. The administrator is not responsible for the accuracy of the information. Everything you do, you do at your own peril and risk
A hunting crossbow is a fairly effective weapon, which, if necessary, can serve as a worthy replacement for a rifle. The main advantage of the weapon is its silent shooting. Therefore, when using it, it is quite difficult to scare the animal.
Design features
What does a hunting crossbow consist of? The photos presented in this material allow us to see that the following components can be distinguished in it:
- The body is the main power unit, which bears the load when lowering the bowstring. Serves as a basis for installing functional parts.
- Blocks are part of the structure for installing bowstring tension arcs.
- The stock is the part of the crossbow that is used to place the arrow.
- The bowstring is a functional part that serves to propel the projectiles used.
- The shoulders are an elastic structural element that releases energy when the bowstring is pulled.
- A stirrup is a part that makes loading a crossbow easier.
- The trigger mechanism is a device due to which the lock opens and the bowstring is released when fired.
- Sight - mounted on the crossbow to facilitate aiming at the target.
Hunting crossbow with wooden shoulders
It is the simplest design. As follows from the definition, the shoulders here are made of wood. Such a crossbow cannot be called a model of reliability. Products in this category are frankly short-lived and therefore are not in very high demand. Most often this hunting crossbow used as collectible and decorative weapons.
Crossbow with metal arcs
An extremely common option. Hunters pay attention to such crossbows because they demonstrate high power when shooting. Hunting bows and crossbows with metal bows are suitable not only for training, but also for use in the field when tracking down prey. For manufacturing, both solid arcs and composite structures are used, which are assembled from several symmetrical parts.
Recurve crossbow
Classic version with curved shoulders. Such a hunting crossbow is an extremely easy-to-handle and convenient device to use. It has small dimensions and improved characteristics. Easily disassembled and transported.
Recurve crossbows contain reinforced arms, the tension force of which can reach about 50 kg. This, in turn, opens up the possibility of hunting small and large animals.
Compound crossbow
The design includes a whole system of eccentrics, thanks to which the process of loading the weapon is facilitated and the acceleration of the arrow is ensured. Compared to recurve models, a compound hunting crossbow is more compact. The power figures here are also excellent.
Small dimensions are ensured by installing short arcs. The use of this solution makes it easier for the weapon owner to overcome areas covered with thickets and bushes.
The characteristics of a block-type hunting crossbow provide simple cocking of the bowstring and insignificant recoil, which is achieved due to the rational distribution of the force vector.
type
- due to their reduced dimensions, they are extremely convenient for transportation;
- have high power and allow you to hit targets at both medium and long distances;
- differ less lethal force compared to block systems, however, they throw arrows at a higher speed;
- in addition to arrows, they can fire darts, harpoons, and metal balls.
Sights
The main feature of crossbow shooting is a significant shift in the aiming line. In other words, after firing the shot, the fired projectile begins to gravitate towards the ground quite quickly. Therefore, it is advisable to install optics with a special crossbow reticle on such weapons. To effectively aim at a target, it is enough to equip crossbows with optical sights with 4x zoom.
Some hunters prefer collimator systems, which also prove to be quite effective. Moreover, this option makes it possible to hunt both during the day and evening time days. Collimator sights are extremely convenient to use when aiming at moving targets.
DIY hunting crossbow
Having decided on the necessary parameters and characteristics of the future weapon, it is worth moving on to developing the appropriate drawing. You can use a ready-made diagram as a sample or create one yourself. Be that as it may, a home-made hunting crossbow will ultimately have to be customized to suit you.
When preparing a drawing, you should focus not only on personal wishes, but also take into account accessibility necessary materials, based on their cost and processing complexity.
How to make a hunting crossbow with your own hands? Usually, to begin with, a stock is prepared, onto which the shoulders, stirrup, guide, and trigger are subsequently attached. Difficult for self-made the elements are arcs. Therefore, in some cases it is better to purchase them ready-made.
They will help you make hunting drawings, examples of which are shown in the photos below.
Frame
The base on which the stock and shoulders of the product are fixed is the body. It is advisable to cut it from a metal blank with a thickness of about 2.5-3 mm.
The crossbow stock is fixed in the central part of the body and at the end using bolts. The use of such a solution facilitates the rapid assembly of weapons to bring them into combat condition and disassembly during transportation.
A stirrup is welded to the body at the bottom. The latter makes it possible to hold the crossbow with your foot when the bowstring is pulled. It is recommended to use wire with a diameter of 6 to 8 mm as the material for making stirrups.
Shoulders
The material for manufacturing the structural element can be a car spring. In such metal arms, semicircular recesses are made for bolts, with the help of which the part will be screwed to the body.
There is a widespread opinion that the use of metal springs as the basis for making shoulders is a rather dangerous decision. And in fact, when using homemade crossbow in conditions of low ambient temperature, the likelihood of part breakage increases, especially at fastening points. Such cases are accompanied by the release of small fragments. Therefore, you should apply the idea at your own peril and risk.
Blocks
Ready-made drawings of a hunting crossbow often include block devices. The latter ease the tension and give an advantage in strength. It is easier to put such a crossbow into combat condition than by simply connecting the ends of the bowstring to the ends of the arms. Moreover, during the descent, the starting speed of the arrow increases, which is reflected in the increase in the range of the weapon. The main disadvantage of installing a block system is the complexity of manufacturing and the increase in the overall weight of the crossbow.
Bowstring
As a bowstring, you can use a metal cable with a diameter of about 2-3 mm. A thicker string will be more difficult to attach to a weapon, and a thin one will begin to stretch as the product is used.
To fix the bowstring at the ends of the arms, it is enough to make a regular loop. It is better to place pieces of leather or any other dense material under the cable fastenings in advance. This solution allows you to avoid chafing of the bowstring when in contact with metal shoulders.
Lodge
To make the part, you can use an easily processed wooden blank in the form of a board about 30 mm thick. It is worth noting that, despite the high strength indicators, oak is not very suitable for these purposes due to its significant weight. As for spruce and pine, the latter are not sufficiently resistant to mechanical damage and warp when in contact with moisture. Therefore, the type of wood should be selected depending on the goals and conditions of future use of the crossbow.
How to make a hunting crossbow truly practical? During manufacturing, special attention should be paid to the guide in the form of a groove for the arrow, which you should try to make as even, smooth and polished as possible. The condition of the groove largely affects the accuracy of shooting. It is advisable that the width of the stock be equal to the diameter of the arrows used. You can cut it using a circular saw.
It is rational to use a spring as a means of holding the arrow, which will press the projectile to the stock and will not allow the latter to slip out of the groove before the shot is fired.
Trigger
The material used to manufacture the part will be sheet iron. It is desirable that its thickness be at least 6-7 mm. The mechanism drawing is presented in the following diagram:
All parts are placed directly into the stock. Here a special nest is cut out, through holes are made under the axes of the mechanism, onto which the trigger elements are subsequently installed. An example of setting the trigger is shown in the figure below.
Sighting optics
As a crossbow sight, you can use factory optics from firearms. A fairly practical solution is to use a front and rear sight. Using the latter, you can make vertical corrections. It is convenient to make horizontal adjustments using a front sight mounted at the intersection of the shoulders and the stock.
To ensure ease of transportation of the crossbow, it is worth making the sighting device removable. To do this, you can install a so-called Picatinny rail on the weapon, which makes it possible to mount individual factory-assembled sights.
In conclusion
Making and operating a hunting crossbow with your own hands is a rather radical solution. Often, in the absence of experience in this type of activity, the quality and reliability of a homemade device leaves much to be desired. In reality, even crossbows of the budget category, factory-made, the cost of which is about 3000-4000 rubles, turn out to be much more effective, convenient and practical compared to the creations of your own hands.
As you can see, making a hunting crossbow is quite possible. However, by purchasing a weapon in a specialized store, the user receives guarantees of its safety and reliability of assembly. When using a homemade crossbow, you can only rely on yourself.
To make a homemade crossbow you will need:
*A block of non-resinous wood, size 700x10x40 mm.
*The second leaf of the spring of the Moskvich car.
*Profile pipe 50x50x2 mm. 10 cm long.
*Profile pipe 15x15x1.5 mm.
*A small piece of 2mm sheet metal.
*Stainless steel metal 4 mm thick. and 0.5-1 mm. (for the descender).
*Steel corner 50x50x4 mm. 35 cm long.
*Rod D=8 mm. 40 cm long.
*Bolts with nuts D=8
*Stainless steel molding from the VAZ-2106 door 2 pcs.
*Metal rollers 2 pcs., glass lifting mechanism from the door of a VAZ car.
*Cable D=3 mm. 3 m long, two terminal loops.
*Epoxy resin, wood stain, wood varnish for exterior use.
*Two small springs (working in tension).
*A dozen nails for roofing felt, one two hundred nail, tube D=6 mm, small washers.
We will use the following tools:
*Welding machine.
*Hand-held circular saw.
*Electric drill with speed control, carbide drills for metal D=3, 5, 8, 10 mm.
*Bulgarian, cutting discs for metal, grinding discs for wood.
*Keys, pliers, screwdriver, vice, narrow chisel, knife.
*File, sandpaper.
*Safety glasses.
Point 1. Making a stock.
Let's take a well-dried wooden block, mine was made of birch, and sketch out a sketch of the bed on it. We customize the size of the butt for each individual (according to your height), and the stock depending on the length of the arrows you will use. I use 440 mm arrows, but I had to save money on the stock, I left only 300 mm, so the total length turned out to be 740 mm, I didn’t dare to do more.
Let's draw a marking for the guide sample, for the arrow fletching, width 5 mm, depth 10 mm.
Using a circular saw, we cut out the groove the entire length, to the end of the trigger (lock).
It should look something like this.
Using a drill D=12 mm. select the cavity under descender, we level the ledges with a chisel and knife. We drill a hole for the trigger, bore it with a chisel and knife.
Point 2. Making a lock or release device.
Let's take the "walnut" type as the basis for the lock. To prevent anything from rusting, we will use stainless steel, take a sheet 4-5 mm thick, if you can’t find one, make it a composite of several sheets glued together and taken with rivets. Draw the shape of the parts on the metal.
Using a cutting disc and a grinder, we cut out the workpiece according to the markings.
In the center of the “nut” we drill a hole for the axis of rotation, D = 6 mm.
We process all sides with a file.
We sand with sandpaper, achieving a completely smooth surface.
It should look something like this.
We grind out the remaining elements of the lock, the sear.
I lengthen the trigger with two thin sheets of stainless steel and secure it with homemade rivets.
On the grinding machine we achieve the desired shape blanks
We make the housing of the trigger mechanism from a thin sheet of metal.
We drill three holes D = 2.5 mm in the body of the sear, one for the fastening axis and two for fastening the springs.
Let's attach the trigger spring into place.
Let's see on the table how the parts become in the cocked state.
And like after the shot.
Let's place one side of the case on the inside of the mechanism and drill holes in place for all the axes.
From a two hundred nail, 6 mm in diameter, we will make an axis for the “nut”.
Saw off the sharp end of the nail.
We measure the length of the future axis and saw it off.
Using thin nails for roofing felt, we will make the remaining rivet axles. Use a grinder to remove the shimmer on the nail heads.
Now they will fit well to the body.
Let's install the sear on the axle in the body, use intermediate washers.
We saw off the excess length of the nail, leaving 1 mm. on both sides for rolling.
Using an anvil, hammer the end of the axle.
We drill a hole for the axle with a spacer to attach the sear spring.
From a suitable tube we cut off a spacer sleeve for this axis.
We move one side of the body to the side.
We install the axle, bushing and engage the spring.
We assemble the body halves together.
We saw off the excess length, leaving a protrusion of 1 mm. under the hammer.
Let's roll it.
Now you can install the largest rivet axle of the lock. Aligning the holes.
Let's take the previously measured and sawed-off axis D=6 mm, and immediately tap it a little with a hammer on one side.
We install it in place.
And we’ll also roll it, the main thing is not to overdo it, so as not to jam the moving mechanism inside.
Point 3. Installation of the lock mechanism in the stock.
If something prevents the lock from sitting well in place, we modify it with a chisel or knife. After installation, check how the trigger moves.
If everything is fine, you can drill holes for the mounting screws and screw them into place.
Now we need decorations from the door of the VAZ-2006, they are also made of stainless steel, which is very good. To give them additional rigidity, epoxy resin was poured inside.
After complete hardening, in a day, we will drill four holes D = 3 mm in each for fastening screws.
Using a large drill, we will make hidden places for the heads of the screws so that the bowstring cable does not get caught when it slides along it.
We polish the hole exits with fine sandpaper to remove all burrs that damage the cable.
We install the finished guides on the bed.
We make sure that the screws do not go through in thin places.
We check that the lock moves without snagging on the guides.
Point 5. Making an arc or shoulders.
From the same donor doors, using a grinder, we extract the rollers of the glass lifting mechanism.
From these we will make blocks for the shoulders, and the arch itself from the second leaf of a spring from an old Moskvich car.
We will make pads to attach the spring to the stock.
To do this, from a 50x50 mm corner. let's cut it out constituent elements, to assemble by welding, this is the mount (block).
We will process the welds with a grinder. Let's drill mounting holes D=10 mm. under the bolts.
Based on the finished sample and the dimensions of the resulting block, we make grooves for fastening in the stock. We try on the fit, achieve a tight fit and fastening. According to the calculated position of the future bowstring, we outline and make a through groove in the sidewall of the stock, 70 mm long. 10 mm wide, the lower bowstrings will go here.
We bend and weld the leg bracket (stirrup).
Ears for blocks.
From a 50x50 profile pipe we will make eyes for attaching the roller blocks to the arc (spring).
The most difficult thing in making the arc itself from a spring at home is drilling holes in it. It is necessary to drill with a drill at low speeds so that the drill does not burn, and constantly use water. If possible, drill with drills of different diameters, from thin to thick in increments of 0.5-1 mm, and constantly sharpen the tool.
We fasten the brackets with short M8 bolts and grind off the caps.
We attach the spring to the block with two M8 bolts, followed by a small weld along the edge of the fastening.
Now you need to open the bed with varnish and dry it.
We install the block with an arc on the stock, hammer down the metal-wood for a tight fit.
Insert and tighten the M8 bolts.
From long M10 bolts we will make axle bolts reduced in length with a short thread for blocks.
Let's take a tube from the anchor and use it to make spacer bushings for the block axes.
Let's drill holes D=10 mm in the ears. to install blocks. We install rigid loop ends on the cable.
We install a block with a cable on one side of the shoulder. Do not tighten the nut too much, so as not to jam the rotation of the roller.
Drill a hole in the nut and bolt for the stud.
We install the stud and press it with the nut in the direction of unscrewing.
We push the cable through the hole in the stock and do the same with installing the roller on the other side of the shoulder.
Point 6. Upper part castle
From a profile pipe 15x15 mm. saw off two 120 mm sections. Using a grinder, we cut out two (L) shaped blanks from sheet metal, one rectangular plate (on the top) and a triangle (on the back).
We connect all the parts together by welding, and clean the welding seams with a grinding disc to make it look like a solid part.
From an old folding steel meter, we make an elastic boom holder.
The photo shows the mounting bolts for the rack for the optical sight.
The same thing, only the bolts also clamp the boom holder.
The sight rail itself (dovetail) is made of the same 2 mm sheet metal, with the sides ground off for mounting optics.
A square pad is visible along the optic rail to raise back and thereby tilt the sight down for correct aiming at a target further than 25 m.
We install the lock bracket on the stock and drill holes for fastening, self-tapping screws and an M6 bolt.
We tighten the small screws so that they do not go into the arrow feather channel.
We tighten the back screw.
Additionally, we drill a hole and install the last bolt.
We install an optical sight.
why111 11-03-2013 13:16
Hello ladies and gentlemen.
I’m turning to professionals (we ourselves are not local) with this question. There is a desire to think about a spring arrow thrower, and it is planned to use a coiled spring, like in an air rifle.
One option is the “Rustler” bow, but I want to do without a bowstring. How theoretically realistic is this? There are two options for now.
1. The spring directly accelerates a heavy arrow at a low speed, but due to its mass, the projectile has high penetration ability, albeit at a distance of up to 25 meters. By the way, I once made this in the form of a toy, it shot with electrodes (5mm cross-section), it flew up only 20 meters, but up to five meters it seemed to be powerful.
2. Use of speed-increasing blocks, for example, a pulley. Those. a short spring is compressed by a block of five “wheels”, and there are five counter-wheels; a cable passes through them, which accelerates the projectile.
Thanks in advance for your answers.
nixxx 11-03-2013 15:08
Can I guess... For self-defense?
why111 11-03-2013 16:39
Fear God! Self-defense with homemade cold steel throwing weapons - yes, it’s better to immediately turn yourself in. For self-defense, there are gas cans and, at worst, household penknives. everyday life appointments.
No, of course, it’s just for the soul.
Juris 11-03-2013 17:01
Yes, if such a shooting mechanism had been invented, it would have been produced industrially and sold in gun stores. At the moment there are compact, quite powerful crossbows. Here you will have to shovel the hansa and look for archers with crossbows on the forum. You can find some interesting schemes with springs and chain hoists. Even on our forum we had proposals with diagrams and drawings. You need to search and read, maybe you will find something interesting.
why111 11-03-2013 17:08
Those. impossible? Honestly, I seem to have skimmed the forum diagonally, but unfortunately I won’t be able to read it for two weeks. I thought maybe someone’s inquisitive mind had already thought about this topic.
Juris 11-03-2013 17:11
Or watch the video of our catapult generalissimo Joerg Sprave. He has a lot of videos with various firing mechanisms. Maybe it will give you the right idea.
Juris 11-03-2013 17:17
Everything is possible, the main thing is to want to know your goal.
why111 11-03-2013 17:22
Thank you, I saw his video, the head works well, although it’s not ours)
why111 11-03-2013 17:55
There was an idea somewhere about this, only simpler, of course.
I was thinking about one spring, a more compact type (not a rifle type, but perhaps a pistol type), and a spring in a case and for compression, not tension.
9_Gram 11-03-2013 19:38
Do you understand, dear Why, all these systems are not effective (excuse my clumsy Russian) The springs themselves are slow, plus they also have to drag their own weight. Also, all these blocks and pulleys are also heavy and bulky. On at the moment Of all the throwing devices (not driven by hot gases), a slingshot with good latex is probably the most productive thing. If you consider the energy and cost put into it and calculate the result obtained from this. Well, maybe some slingshot will still argue with her. ( Nice bow inferior in size, price and cost per shot. And of course, the energy invested in the shot must be truly pulled)
Well, I’ll give you an example, in this video you see the “Raptor” blocker set in motion by strong tires. (Springs were not taken, since their efficiency is worse than that of rubber)
This device has a tensile force of up to 80 lbs (approximately 36-38 kg) and accelerates a 10 mm ball at a speed of 140-150 m/s
Wow, that seems pretty good. But let's consider the energy expenditure in this thing. Firstly, to stretch 36 kg you need good health (I was visiting Jorg and also shot with this thing, I’ll tell you to pull oh oh how it should)
Then the dimensions, and finally the cost of this thing (I don’t know exactly, but it’ll probably cost $800.
If you try to do such a thing yourself, it is impossible. Or you need to have an excellent lathe at home. Or shell out a lot of money to the industry. Then where to shoot? In the garden? How to hang around with him? With this size and weight, it is not a very comfortable thing for walking.
Well, now we make a slingshot at home from hazel and purchased fitness tape.
Price? A penny, anyone can afford it.
Dimensions? Fits easily in your pocket, you can clutch it in your fist.
Where to shoot? Anywhere, the thing is not heavy. You can take it and drag it anywhere. It’s not conspicuous, no one will look at you idiotically. In extreme cases, it quickly gets out of sight.
How much energy do we spend when firing? With a tensile force ten kilograms with good latex in Albatross we will accelerate the same 10 mm ball well
at 110 m/s, maybe more if you try. How many shots will we make with a 10 kg drawstring (even a teenager can pull it)?
How many shots will we fire with a 36 kg Raptor?
After 10 shots, Jörg is already breathing with his tongue hanging out and blowing off steam like a steam locomotive. And he is a really strong man. But another one won’t pull it even once.
Well, about the same thing will happen with your gun on springs. You will struggle to do it. It will turn out to be a heavy, large-sized thing. And if it shoots at least a few meters per second better than a slingshot, then respect to you.
This is usually the case with all these homemade guns; if you look closely, there is already something more effective and cheaper than what you invest in your brainchild. It's just not worth the candle.
why111 11-03-2013 19:50
Thank you very much for your detailed answer. Of course you are right. It’s just that I’m itching to get my hands on something, but I’ve been thinking about this topic for a long time. And the spring is still more durable than plastic.
By the way, after studying the forums a little, I saw that a lot of archers and crossbowmen periodically think about this. Only a few are producing good, working models. Okay, let's see, maybe we can come up with something.
9_Gram 11-03-2013 20:08
Well, if it’s just for handjobs, then you can do whatever you want and in the end throw it away without regret if nothing good comes of it. If you fix anything, don’t be shy to show it.
ZlH 12-03-2013 14:47
2 why111
I really advocate for a gas spring with an ultra-light rod.
why111 12-03-2013 15:01
Well, gas is for the pros, I’m still thinking about something more budget-friendly and simpler, just to see what can come of it.
ZlH 12-03-2013 15:47
2 why111
Yes, there is nothing complicated there - but the usual twisted one in itself is quite heavy and inert.
+ how to cock?
why111 12-03-2013 16:47
Well, the simplest option is like the picture above. It cocks like a typical crossbow. A long time ago I made one that was cocked with an arrow; it had to be rested on something.
why111 12-03-2013 17:48
Well, that means the principle still works, the main thing is to design it. True, there is no machine park to make products like those in the link.
Juris 13-03-2013 15:57
In general, it’s an interesting topic. But it’s a bit difficult to do it at home. Again, you can only look at Yorga systems made of wood, which can actually be done. Or look on the Internet for something like a pitbull crossbow and all its components. This requires a lot of testing and money. It’s easier for now. make a good slingshot or upgrade a compact Izhik fracture.
delete 13-03-2013 23:55
Yes, indeed, many people think about compact mechanical crossbows
Well, many are stopped by the very first factor, where and how to do all this
and is it necessary, since it is very difficult to force it to produce normal parameters
the design turns out to be bulky and heavy, since it turns out that the spring must be set to a compression force of at least 100 kg.
You can, of course, first start with mock-ups made of wood or something else, on which you can pre-work out the diagram, select the optimal shape of the block if the spring is meant to be weaker
but again this is not for everyone
For example, for me it won’t be difficult and generally not very annoying if my next project in terms of spring mechanical bows or crossbows in the form of a model will be checked and tested for professional suitability within six months, or even a year
I'm ready to wait, but find the best option
so maybe it’s better to actually make a slingshot for now
and the spring pushing the projectile directly will have very, very weak parameters
Well, and in addition, a video of a foreign Kulibin
http://www.youtube.com/watch?v=AXwTZLrtsRA
9_Gram 14-03-2013 02:05
delete 14-03-2013 07:56
but he tested his theory
first, a spring in such a design will not give the arrow normal speed
second, cocking with a screw and nut is very good way
why111 14-03-2013 13:02
quote: second, cocking with a screw and nut is a very good way
With a powerful spring - yes, but you need a thread with a wide pitch, trapezoidal, and a standard folding gate. You can consider a Chinese threaded jack as a donor.
9_Gram 14-03-2013 17:49
The screw and nut cock well, yes. But don't forget cocking time! After five shots you'll have to go home, it's night outside
Designer and gunsmith Bogdan Khmelnitsky often has to deal with mistrust. Having seen his bows and crossbows, people refuse to believe that the inventor made them with his own hands and that the development and manufacture of weapons is just a hobby for him, and not his life’s work. Indeed, with his high-tech samples in his hands, Khmelnitsky looks more like the head of a design bureau or the owner of a small arms factory. So the master has to constantly remind him that he makes his prototypes exclusively at home, and his house is very ordinary - without CNC machines, painting booths and “clean rooms”.
Although it would be possible not to explain anything: Bogdan Khmelnitsky’s weapons can withstand the harshest criticism of an industrial scale without any discounts on the hobby. We could verify this by studying the bows “Phantom” (PM No. 5"2011) and “Cobra” (No. 1"2014). The inventor's know-how is to use steel or gas springs instead of traditional flexible arms as energy sources for the shot. The result of this approach is a weapon that is as close as possible to sports bows in terms of characteristics and shooting technique, but is much more compact and easy to transport.
Khmelnytsky's bows are complex and elegant designs with paradoxical properties. For example, the stroke of the Cobra's string tension significantly exceeds the dimensions of the weapon itself thanks to a block with parallel grooves (the string rests twice on the same block) and a composite eccentric module of a complex shape.
This time Bogdan brought a crossbow to our editorial office, and, at first glance, there is nothing complicated about it: no eccentrics, just a few simple pulleys. However, Condor is not as simple as it seems. To figure it out, it’s worth remembering what crossbows of classical design are.
Member of the Russian national team and European champion in crossbow sports, Vladislav Liber, like no one else, is able to understand and appreciate the inventive talent of Bogdan Khmelnitsky. After all, he also holds a crossbow of his own design. Vladislav's know-how is rigid aluminum guides combined with a narrow ram made of good sliding resin.
Get itchy, shoulder!
A classic crossbow is also called a recurve crossbow. In it, the bowstring is attached directly to the ends of the flexible arms. The shoulders obey the same physical law as a spring, the elastic force of which is greater the more it is compressed. This means that the crossbow only develops maximum force when the bowstring is fully drawn. As soon as the arrow starts to move, the force begins to drop rapidly, so the speed of the arrow in recurve crossbows is relatively low.
To somehow combat this annoying effect, the Japanese made their two-meter (and sometimes larger) “yumi” bows. The long and very powerful arms had a small stroke, so the force remained more or less uniform throughout most of the bowstring's stroke. With recurve crossbows, everything is the same: the wider the shoulders, the more effective the weapon.
Compound crossbows (like bows) use a pulley system. The bowstring in them passes through rotating eccentrics, which work like a lever with a shoulder that changes along the tension. With the help of a chain hoist, the force curve can be adjusted to your liking. After the shot, the force on the bowstring constantly increases, and the arrow accelerates with effort throughout the entire stroke. Therefore, block crossbows can boast of high arrow flight speed with the most compact arms.
In terms of its properties, Khmelnitsky’s “Condor” is something between a recurve crossbow and a “block gun”. It does not have eccentrics, but the gas spring itself has a much more even force characteristic than a flexible arm. At the very beginning of the stroke, it already develops more than 75% of the maximum force, so during acceleration it is able to transfer much more energy to the projectile than traditional shoulders. At the same time, the width of the Condor is smaller than that of the most compact block cars. But in terms of weight (4.5 kg), it is definitely closer to “block crossbows” - recurve crossbows are much lighter.
To charge the Condor, a tensioner is used - a special device, which is a strong cord with handles at the ends and hooks for gripping the bowstring in the middle. A stirrup helps hold the crossbow motionless.
Of course, Bogdan is thinking about installing eccentrics instead of conventional pulleys. With them, the Condor could demonstrate miracles of efficiency. The law allows citizens to operate crossbows with a force of up to 43 kgf without a permit, and it is better to have these 43 kg at the end of the stroke than at the beginning - after all, this gives up to a 40% increase in the speed of the arrow.
Word to the champion
“Who are the judges?” — we remembered the classic and decided to turn to the Russian Crossbow Union for expert comments. On the territory of the Hunter shooting center, Condor met face to face with professional crossbows of the Russian team, and Bogdan Khmelnitsky met with Vladislav Liber from the Cheetah team, an international master of sports, a member of the Russian national team, and European champion in the team championship. At first, Vladislav also mistook the inventor for an enterprising businessman and did not make any concessions to the weapon.
Bogdan Khmelnitsky // Age: 37 years old // Profession: milling operator // Hobbies: archery, invention of weapons. Bogdan became interested in archery as a child. Soon his interest grew into a serious hobby sports shooting. Bogdan even trained at work during his lunch break, but in a cramped room it was difficult to turn around with the Olympic bow. This is how a professional milling machine operator came up with the idea of inventing a compact weapon for archery athletes.
The athlete's main criticism was that the guides were too long. “The longer the arrow moves along the guides, the longer the shooter must hold the weapon motionless after firing. This is not an easy task, so the longer the weapon and the greater the stroke of the bowstring, the lower the accuracy,” explained Vladislav.
Looking at the Condor disassembled, it is easy to understand that the length of the crossbow is dictated by the dimensions of the gas spring. But the stroke of the bowstring tension can be reduced by using additional blocks or installing wider “shoulders”. However, it should be remembered that extra blocks will reduce the speed of the arrow due to friction, and increased “shoulders” will deprive the weapon of perhaps its main advantage - compactness.
Criticism also affected the material of the guides. According to Vladislav, aluminum is not suitable for them best choice. Firstly, it is far from ideal in terms of friction. When abraded, microscopic irregularities form on it, which prevent the arrow from sliding freely. Sports crossbows use polymer resins and plastics, which, due to their molecular structure, remain smooth for a long time.
Secondly, with prolonged use, a barely noticeable depression is machined into aluminum guides, and a vertical component appears in the trajectory of the arrow, which negatively affects accuracy and takes away some of the energy. Vladislav himself designs sporting crossbows and uses hybrid guides with external aluminum rails and a resin head. Hard aluminum bears the main weight of the projectile, and soft resin is responsible for sliding.
Of course, members of the Russian crossbow sports team noted high quality production of the Condor, and head coach Sergei Chikishev even suggested that a reliable and unpretentious crossbow with long guides could be useful when training shooters - to train hand steadiness.
Bullseye!
When shooters talk about weapons, even nightingales fall silent. Bogdan and the members of the team enthusiastically discussed the features of the Condor, shooting at targets from 25-50 m. Having reached a consensus on the issue of zeroing the weapon (strictly at the center of the target!), they decided to give the newcomers a chance.
The first to go to the firing line was our photographer Dima, who that day picked up a crossbow for the first time. I remembered all the shooters’ recommendations, held my breath, pulled the trigger and... hit the target at a distance of 25 m right on the bull’s eye! It is difficult to describe how wildly Dima rejoiced at such a pleasant “accident”.
Then it was the turn of your humble servant, who had also never held a crossbow in his life. The result is the same - right on target. Agree, a repeating result can no longer be attributed to chance. Despite the criticism, Condor proved its worth in action.
We will be looking forward to Bogdan's visit for the fourth time to shoot from another hitherto unseen weapon.
The editors thank the President of the Russian Crossbow Union Valery Ashikhmin for his assistance in preparing the material.
