Dynamic balancing of the crankshaft. Balancing

Balancing the cardan shaft can be done both with your own hands and at the service station. In the first case, this requires the use special tools and materials - weights and collars. However, it is better to entrust the balancing to the service station workers, since manually it is impossible to accurately calculate the weight of the balancer and its installation location. There are several “folk” balancing methods, which we will discuss later.

Signs and causes of imbalance

The main sign of the occurrence of an imbalance in the cardan shaft of a car is appearance of vibration the entire body of the machine. At the same time, it increases as the speed of movement increases, and, depending on the degree of imbalance, it can manifest itself both already at a speed of 60-70 km / h, and more than 100 kilometers per hour. This is a consequence of the fact that when the shaft rotates, its center of gravity shifts, and the resulting centrifugal force as if "throws" the car on the road. Additional feature in addition to vibration is the appearance characteristic hum emanating from under the bottom of the car.

Unbalance is very harmful to the transmission and chassis of the car. Therefore, when its slightest signs appear, it is necessary to balance the “cardan” on the machine.

Neglect of breakdown can lead to such consequences.

There are several reasons for this breakdown. Among them:

• normal wear and tear parts for long-term operation;
• mechanical deformations caused by impacts or excessive loads;
• manufacturing defects;
• large gaps between separate elements shaft (in case it is not solid).

The vibration felt in the cabin may not come from the driveshaft, but from unbalanced wheels.

Regardless of the cause, when the symptoms described above appear, it is necessary to check for imbalance. Repair work can also be done in your own garage.

How to balance the gimbal at home

Let's describe the process of balancing the cardan shaft with our own hands using the well-known "grandfather" method. It is not difficult, but it can take quite a while to complete. a lot of time. You will definitely need viewing hole, on which you must first drive the car. You will also need some weights. different masses used in wheel balancing. Alternatively, instead of weights, you can use electrodes cut into pieces from welding.

Primitive weight for balancing the cardan at home

The algorithm of work will be as follows:

1. The length of the cardan shaft is conditionally divided into 4 equal parts in the transverse plane (there may be more parts, it all depends on the amplitude of the vibrations and the desire of the car owner to spend a lot of time and effort on this).
2. To the surface of the first part of the cardan shaft securely, but with the possibility of further dismantling, attach the aforementioned weight. To do this, you can use a metal clamp, plastic tie, tape or other similar device. Instead of a weight, you can use electrodes, which can be placed under the clamp several pieces at once. As the mass decreases, their number is reduced (or vice versa, with an increase, they are added).
3. Next is testing. To do this, go by car to flat road and analyze whether the vibration has decreased.
4. If nothing has changed, you need to return to the garage and re-weigh the load to the next segment of the cardan shaft. Then repeat testing.

Mounting the weight on the cardan

Items 2, 3 and 4 from the above list must be followed until you find on cardan shaft the area where the weight reduces vibration. Further, similarly empirically, it is necessary to determine the mass of the weight. Ideally, with the right choice vibration should be gone. at all.

The final balancing of the “cardan” with your own hands consists in rigidly fixing the selected weight. For this, it is desirable to use electric welding. If you don’t have it, then in extreme cases you can use a popular tool called “cold welding”, or tighten it well with a metal clamp (for example, plumbing).

Balancing the cardan shaft at home

There is another, albeit less effective method diagnostics. In accordance with it, it is necessary dismantle cardan shaft from the car. After that, you need to find or pick up a flat surface (preferably perfectly horizontal). Two steel corners or channels are placed on it (their size is unimportant) at a distance slightly less than the length of the cardan shaft.

After that, the "cardan" itself is laid on them. If it is bent or deformed, then its center of gravity is shifted. Accordingly, in this case, it will scroll and become in such a way that its heavier part will be at the bottom. This will be a clear indication to the car owner in which plane it is necessary to look for imbalance. Further actions similar to the previous method. That is, weights are attached to the cardan shaft and the places of their attachment and mass are calculated empirically. Naturally, the weights are attached on the opposite side from the one where the center of gravity of the shaft is shifted.

Another effective method is to use a frequency analyzer. It can be made by hand. However, a program is needed that imitates an electronic oscilloscope on a PC, showing the level of the frequency of oscillations that occur during the rotation of the gimbal. You can say it from the Internet in the public domain.

So, to measure sound vibrations, you need a sensitive microphone in mechanical protection(foam rubber). If it is not there, then you can make a device from a speaker of medium diameter and a metal rod that will transmit sound vibrations (waves) to it. To do this, a nut is welded into the center of the speaker, into which a metal rod is inserted. A wire with a plug is soldered to the speaker outputs, which is connected to the microphone input in the PC.

1. The drive axle of the car is hung out, allowing the wheels to rotate freely.
2. The driver of the car "accelerates" it to the speed at which vibration usually occurs (usually 60 ... 80 km / h, and gives a signal to the person who takes the measurements.
3. If you are using a sensitive microphone, then bring it close enough to the place of marking. If you have a speaker with a metal probe, then you must first fix it to a place as close as possible to the applied marks. The result is fixed.
4. Conditional four marks are applied to the cardan shaft around the circumference, every 90 degrees, and numbered.
5. A test weight (weighing 10 ... 30 grams) is attached to one of the marks using a tape or clamp. Also can be used directly bolted connection clamp like a weight.
6. Next, measurements are taken with a weight at each of the four places in sequence with numbering. That is, four measurements with the movement of cargo. The results of the oscillation amplitude are recorded on paper or computer.

Location of imbalance

The result of the experiments will be the numerical values ​​of the voltage on the oscilloscope, which differ from each other in magnitude. Next, you need to build a scheme on a conditional scale that would correspond to numerical values. A circle is drawn with four directions corresponding to the location of the load. From the center along these axes, segments are plotted on a conditional scale according to the data obtained. Then you should graphically divide segments 1-3 and 2-4 in half by segments perpendicular to them. A ray is drawn from the middle of the circle through the intersection point of the last segments to the intersection with the circle. This will be the unbalance location point that needs to be compensated (see figure).

The desired point for the location of the compensation weight will be at the diametrically opposite end. As for the mass of the weight, it is calculated by the formula:

• unbalance mass - the desired value of the mass of the established imbalance;
• vibration level without test weight - voltage value according to the oscilloscope, measured before installing the test weight on the gimbal;
• the average value of the vibration level - the arithmetic average between four voltage measurements on the oscilloscope when installing a test load at four indicated points on the gimbal;
• the value of the mass of the test load - the value of the mass of the established experimental load, in grams;
• 1.1 - correction factor.

Usually, the mass of the established imbalance is 10 ... 30 grams. If for some reason you did not manage to accurately calculate the imbalance mass, you can set it experimentally. The main thing is to know the installation location, and adjust the mass value during the ride.

However, as practice shows, independent balancing of the cardan shaft by the method described above only partially eliminates the problem. The car can still be driven for a long time without significant vibrations. But it will not be possible to completely get rid of it. Therefore, other parts of the transmission and chassis will work with it. And this negatively affects their performance and resource. Therefore, even after self-balancing, you need to contact the service station with this problem.

Technological repair method

Cardan Balancing Machine

But if for such a case you don’t feel sorry for 5 thousand rubles, this is exactly the price of balancing the shaft in the workshop, then we recommend going to the specialists. Performing diagnostics in repair shops involves the use of a special stand for dynamic balancing. To do this, the cardan shaft is dismantled from the machine and installed on it. The device includes several sensors and so-called control surfaces. If the shaft is unbalanced, then during rotation it will touch the mentioned elements with its surface. This is how the geometry and its curvature are analyzed. All information is displayed on the monitor.

Performance repair work can be done in various ways:

• Installation of balancer plates directly on the surface of the cardan shaft. At the same time, their mass and installation location are accurately calculated computer program. And they are fastened with the help of factory welding.
• Balancing the cardan shaft on a lathe. This method is used in case significant damage element geometry. Indeed, in this case, it is often necessary to remove a certain layer of metal, which inevitably leads to a decrease in the strength of the shaft and an increase in the load on it in normal operation modes.

Similar balancing machine cardan shafts it will not work with your own hands, because it is very complicated. However, without its use, high-quality and reliable balancing cannot be performed.

Results

It is quite possible to balance the cardan yourself at home. However, it must be understood that it is impossible to choose the ideal mass of the counterweight and the place of its installation on your own. That's why self repair possible only in the case of minor vibrations or as a temporary method of getting rid of them. Ideally, you need to go to a service station, where they will balance the cardan on a special machine.

Shaft - a part of machines and mechanisms designed to transmit torque along its longitudinal axis. The most common are shafts assembled with impellers, pulleys, sprockets, etc. installed on them.

Like any other mechanical part, the shaft may be incorrectly installed in bearing supports, have inhomogeneities in the density of the material, violations in the geometry of manufacture and insufficiently accurate fit of parts rotating with it, etc. As a result of the above reasons, unbalanced masses appear in the rotating shaft, causing low-frequency vibrations of the shaft. These vibrations can be so significant that they can lead to shaft bending and complete destruction of bearing assemblies and other machine parts. That is why it is so important to balance the influence of unbalanced masses by performing a shaft balancing procedure.

Earlier, we have already considered the types of rotor unbalance and the corresponding types of balancing - static and dynamic. It was noted that the accuracy of dynamic balancing is an order of magnitude higher than the accuracy of static balancing, and that for rotors whose diameter is much larger than the length (pulleys, impellers, sprockets), only static balancing can be limited.

In the case of shaft assemblies (for example, a shaft with an impeller), in most cases it can be limited to static balancing of the impeller and dynamic balancing of the shaft assembly on the machine and / or in its own supports. In fact, a perfectly balanced shaft assembly is a shaft with separately balanced parts, then balanced as an assembly on the machine, and finally balanced in its own supports.

According to the statistics of the BALTECH company, a recognized expert in the field of balancing, proper balancing of the shafts of rotating machines increases the service life of impellers and impellers by 23%-100%, and also increases their useful power by 10%-25%.

Balancing shafts in their own bearings must be entrusted to specialists technical service"BALTECH", armed with the most modern balancing tools - mobile kits "PROTON-Balance-II" and BALTECH VP-3470 and the program of multi-plane balancing BALTECH-Balance.

The main production direction of the BALTECH company is the production of modern pre-resonance machines for horizontal, vertical and automatic type for rotors of various configurations, weights and dimensions. Let us consider in more detail the capabilities of BALTECH balancing machines using the example of a vertical balancing machine of the BALTECH VBM-7200 series.

Balancing machines of the BALTECH VBM-7200 series are designed for one-plane or two-plane balancing of shafts and parts (impellers, pulleys, disks, etc.) without shaft journals. In relation to our case of shaft balancing, cutting tools and cartridges are also balanced on these machines.

The shaft balancing procedure takes only a few minutes and includes:

• Input geometric parameters balanced shaft;
• Starting the balance shaft into rotation and taking automatically calculated data on the size and installation angle of the corrective mass.
• Installation / removal of the corrective mass.

We note in particular that high speed and measurement accuracy is achieved through the use of the BALTECH-Balance program, the standard functionality of which allows multi-plane (up to 4 planes) and multi-point (up to 16 points) balancing with vibration amplitude and phase measuring instruments of any manufacturer.

To get deep theoretical knowledge and professionally master the skills of working with balancing machines and devices "BALTECH", we recommend that you sign up for the next Course TOR-102 "Dynamic balancing" in training center company BALTECH.

DYNAMIC BALANCE OF ROTORS ON THE MACHINE WITH ROCKING FRAME

Balancing the rotors is a procedure necessary if the rotating part of the machine is out of balance. In this case, during rotation, there is a shaking (vibration) of the entire machine. In turn, this can lead to the destruction of the bearings, the foundation and, subsequently, the machine itself. To avoid this, all rotating parts must be balanced.

The rotor itself is a rotating part, which is held during rotation by means of bearing surfaces in the supports (trunnions, etc.). The axis of the rotor is a straight line connecting the centers of gravity of the contours on the cross sections of the center of the bearing surfaces. There are several types of details:

Double support;

Multi-bearing;

Intersupport;

Console;

Two-console.

Distinguish balancing of rotors static and dynamic. The first is performed on prisms, the second when the part to be balanced is rotated.

Specialists of the company "KardanBalance" offer services for high-quality balancing of the rotor. Our centers are equipped modern equipment, which guarantees the accuracy of balancing. This is quite difficult to achieve, because it must completely coincide with the accuracy of the manufacture of the rotor. All work is carried out on stands own development, which give a balancing accuracy five times higher than the factory requirements!

In this section, you can get acquainted with the main technical information regarding the methods of dynamic balancing of the rotor (the method of exceptions, the method of B.V. Shitikov). Useful practical material that will give a basic understanding of the problem. What is hydraulic balancing, what is a wheel balancing machine and other information is clearly presented on our resource. You can also use our services, which include cardan repair, truck wheel balancing, crankshaft etc. How much does balancing and other work cost is described in the "Services and prices" section.

1. INTRODUCTION. BASIC CONCEPTS

When rotating m(mass) around a point (stationary) with w (angular velocity) F(centrifugal force of inertia) of this mass:

(1.1)
Where and n - normal acceleration of the mass; is the distance from the axis of rotation to the center of mass. As the mass F moves, it will change direction and act (vibrate) on the supports and through them on the structures attached to the post.
D(imbalance) - a vector quantity that is equal to the product of the unbalanced mass and the eccentricity (radius vector of the center of mass). The value is measured in g/mm.

And the vectors " D" And " e" collinear quantities.

In vector form, the formula has the following form:

The vectors F and D turn out to be proportional to each other.

2. ROTOR UNBALANCE AND ITS MANIFESTATION

According to GOST 19534-74, a rotor is a body that, during rotation, is held in supports by its bearing surfaces. In automobiles, this can be a gear wheel, a pulley, an electric motor rotor, a drum, a crankshaft, etc.
If the masses are distributed in the rotor so that during rotation they cause loads in the supports, then it is called unbalanced. Moreover, there are 3 types of rotor unbalance:

• Static. At which the axis of rotation and the main axis of inertia are parallel. In this case, the pressure variables are equal to 0

• Dynamic. In which the main axis and the axis of rotation intersect or intersect, but not at the center of mass, because of this, imbalance occurs most often.
• Instant

In all cases of unbalance of the rotor, the forces of inertia of its masses create dynamic loads. They are eliminated by the redistribution of masses (by installing counterweights).

Dynamic balancing is carried out using a special machine equipped with an oscillating frame

3. Rotor balancing by elimination method

In order to determine the parameters of the mass (corrective) in the P plane, the rotor is installed on the machine and the eccentricity of the mass is assigned. A circle is outlined in the plane, and its center must coincide with the geometric axis of rotation. The radius is taken equal to the selected eccentricity. The circle is divided into 4 parts. We attach the mastic (plasticine) so that the center of the piece coincides with point 1. Let's bring the rotor into rotation and measure the amplitude of the oscillations. The indicator is recorded near point 1.

We transfer the mastic to point 2, accelerate the rotor and again fix its amplitude. Let's write it down. We fix the remaining 2 points.

We compare the amplitudes until they are the smallest. Point K, found by us, determines the final position of the corrective mass. The opposite point H is an unbalanced mass.

Now we begin to change the mass of the mastic into points K and measure the oscillations of the rotor. So we find the value of the corrective mass.

4. BALANCE OF THE ROTOR BY THE B.V. METHOD SHITIKOVA

Install the rotor on the frame and accelerate it. After that we fix the amplitude A 1 .

At point P 1 we will install an additional mass m g with eccentricity e g . At resonance, we fix the amplitude AS.

We rearrange the mass to the opposite point and fix the second amplitude. We denote points on the plane in accordance with the inequality under which the first amplitude is greater than the second.

By 3 amplitudes we build a parallelogram and find the fourth amplitude and angle

1

Using the formula, we determine the coefficient of proportionality of the mass

m= A g /D g = A g /( m g e g),

Determine the imbalance of masses

Now we set the value of the mass (corrective) from the equality of imbalances and find the desired eccentricity

D to \u003d D 1 e k \u003d D 1 /m k.

It remains to determine the points of installation of weights and test runs to determine the residual amplitude, as well as to evaluate the quality of balancing in the plane.

Doct =Aoct /m

In the company "KardanBalance" you can buy a Chevrolet Niva cardan shaft, a UAZ cardan shaft, a Mercedes Vito cardan shaft, as well as components for other cars. We carry out not only the sale of spare parts, but also their subsequent installation.

The crankshaft, being one of the most important structural elements power unit any car produced using enough complex technologies. The inevitability of being present this process technological tolerances and errors, as well as the heterogeneity of the materials used in this case, together with the gaps in the interfaces of parts and assemblies, violate (albeit slightly) one of its main operating conditions- balance.

How to determine the need for crankshaft balancing. The main symptoms that help to establish the presence of a “disease” with a high degree of certainty are significant fluctuations in the power unit and the gear lever when the car is moving in the “idle” mode.

And then you have to resort to performing such an action, which is the balancing of the crankshaft. It (balancing) consists in the selection of additional masses, or balancing weights, as well as the removal of metal in the planes of the location of these weights from the side diametrically opposite. These activities are carried out in special areas of the crankshaft, called balancing sections.

Types of crankshaft balancing

Currently, two main types of balancing are used:

dynamic, providing high accuracy and requiring the use of special machines.

static. This type of balancing is used for parts made in the form of a disk and having the following ratio of diameter (D) and length (L): D>L.

The balancing of the crankshaft, which has an asymmetrical (for example, V-shaped) design or an odd number of cylinders, is distinguished by certain features, since the momentary component of such shafts is quite high and is capable of tearing it off the mounting supports.

To avoid this, the installation of bushings-compensators with a mass verified up to one gram on the crankpins will help. In the absence of these parameters in the special sections of the technical and operational documentation of the power unit, they are calculated discretely. For this, there are individual methods.

The next point, which requires a fairly clear understanding, is the definition of cases, necessitating crankshaft balancing:

Installation of non-standard or implementation of facilitating measures on standard connecting rod and piston groups.

Carrying out work on editing deformed crankshafts.

Flywheel replacement. It should be noted here that in this case dynamic balancing is not always necessary. In some cases, it is sufficient to perform only static type balancing.

So, we consider it established that balancing non-mirror crankshafts, a special case of which is the V-shaped crankshaft, requires the use of compensating bushings (often made according to special order), creating an imitation of a dynamic effect similar to the effect of connecting rod and piston groups.

How important is timely balancing of the crankshaft

The overwhelming majority of experts give the following arguments as an answer to this question:

It happens that on the engine it is necessary to replace the flywheel, its ring gear or clutch basket and after replacing the listed parts, and even after replacing (after washing oil channels), it must be balanced. If this operation is neglected, then your engine, even with an increase in the speed of the car to only 70 km / h, will begin to vibrate strongly due to imbalance. Naturally, this cannot be allowed, and the crankshaft must be balanced before installing it on the engine. How to make a simple balancing device in just a couple of hours, and what is required for this, we will consider in this article.

Most automobile or motorcycle factories balance their crankshafts as an assembly with a flywheel and clutch basket, and some, for example, the crankshaft of a Dnepr motorcycle or a Zaporozhets car, also balance as an assembly with a centrifuge. This must be taken into account and, before balancing, put all the parts on the crankshaft, and even a pulley or gear on the front of the shaft, unless of course they exist in the design of your particular engine.

Well, of course, all the connecting rods, complete with pistons, rings and fingers, will need to be weighed and achieve exactly the same weight. Many factories (usually domestic ones) neglect this, so I advise you to weigh the above parts at the first engine repair, and if there is a difference in weight, eliminate it (by removing excess metal).

By the way, when boosting the engine, many mechanics lighten the flywheel by turning it, and after lightening the flywheel, it is also necessary to balance the crankshaft, complete with a lightweight flywheel.

Crankshaft balancing tool.

The balancing device, which will be described in this article (see photo), is very simple and any driver who is not even experienced in plumbing can make it. For work, you will need a little profile pipe, or a corner, a steel bar with a diameter of 12 - 16 mm, (it can be construction), a grinder and.

First you will need to make a base - a frame, approximately 400 x 400 or 500 x 500 mm in size, which is welded from a corner or a profile pipe (the width of the corner or pipe is 45 - 60 mm). In general, the dimensions of the frame and the device itself depend on the length of your crankshaft, because if you need to balance the crankshaft from the truck, then naturally this device will need to be made in larger sizes.

After you weld the frame and clean welds, in two corners of the frame (numbers 1 and 2 in the photo) and in the middle of the opposite pipe (number 3 in the photo) you will need to drill holes (their diameter depends on the thickness of the bar from which the studs are made). Nuts are welded to the holes on top, the diameter of the internal thread of which depends on the diameter of the three studs that you buy or make from a bar.

Why are there only three studs and not four in each corner of the frame? Because in order to set the frame before balancing strictly horizontally (with the help of a level), it is enough to turn only three pins, and the fourth only complicates the adjustment. Lock nuts will also need to be screwed onto each stud, which, after adjusting the frame, will lock. At the top of each stud, it is useful to sharpen two flats for a wrench with a grinder, so that later it is easy to turn them when adjusting the level.

Now it will be necessary to drill four holes closer to each corner of the frame, with a diameter of 14 - 16 mm. 4 studs (racks) made of a bar are inserted into these holes and clamped with nuts, about 14-16 mm thick and about 250 mm long (the length of all four studs is exactly the same).

Now, on the upper part of each pair of studs - racks, you need to put on two corners (20 - 40 mm wide and about 300 mm long) of the corner, (before that, we drill holes in the corners). We put on the corners and grab them by welding so that their sharp edge is at the top, the crankshaft will fit on this edge. You will get two U-shaped racks located opposite each other (like two horizontal bars). That's all - a device for balancing the crankshaft in a garage or even at home is ready!

Crankshaft balancing.

Before balancing, you must first set the device strictly horizontally, relative to the force of gravity of the Earth. To do this, first we lay the level on the corner (20 mm) of the U-shaped rack located near the numbers 1 and 2 and twist the pins 1 and 2 until we achieve its absolutely horizontal location and, accordingly, the corner on which it lies.

Then we turn the level perpendicularly and lay the level across, that is, immediately on two corners of both U-shaped racks, and by rotating the pin 3, we achieve an absolutely horizontal position of the entire device as a whole.

Having set the device exactly horizontally, you can lay the crankshaft assembly on it with the details as in the photo. If there is an imbalance, then the crankshaft will immediately begin to rotate, that is, roll along the edge of the corners until the center of gravity of the parts is at the lowest point (the gravity of the Earth helps us). Naturally, this imbalance (overbalance) must be eliminated.

To eliminate the overweight, you need to drill out excess metal in the heaviest (lower - indicated by the arrow in the photo) part of the flywheel to remove excess weight. But how to know exactly this weight. To do this, to the lightest opposite side of the flywheel (above), you need to glue magnets of different weights or pieces of a large magnet (you can break the magnet from the speaker into pieces).

You will need to add (glue) magnets to the flywheel until the crankshaft assembly with parts, no matter how you turn it on the corners, should lie motionless (do not roll either to the right or to the left). All the magnets that were glued must be weighed, and this exact weight will be an advantage (imbalance). Now there are a lot of Chinese electronic scales on sale - you will need to buy them, they are not expensive (or ask to weigh the magnets in the store).

Now you will need to drill out enough metal from the flywheel so that the weight of the chips is the same as the weight of the magnets that compensate for the imbalance. When drilling, it is advisable to lay a cloth under the flywheel so that the chips can be collected and weighed. But almost one hole drilling (about 7 - 8 mm) is always not enough, and you have to drill several. If there is a milling machine, then excess metal can be milled in the flywheel. But the main thing is not to overdo it in this matter, otherwise you will have to drill on the opposite side of the flywheel later.

By the way, if you have a pulley, gear or centrifuge at the other end of the crankshaft, and you changed them and not the flywheel, then you will need to balance along with these parts (as in the photo) and drill out excess metal in them, and not in the flywheel. Well, if you changed the clutch basket, then you need to balance your crankshaft with the basket fixed on the flywheel (here it will be possible to drill out excess metal in the basket, where the holes for its fastening are).

And finally, I will add that this device can also be used to check the beating of the crankshaft, using an indicator stand with a clock type. To do this, you just need to drill two holes in the upper corners (on which the crankshaft is laid) and fix two prisms on them, on which the crankshaft will subsequently be laid, to check its runout with a clock indicator.

I hope this article will help all drivers who love to do everything on their car themselves, and who, with the help of this device, can easily balance the crankshaft in their garage.

To complete the picture, as well as for everyone to understand how balancing the crankshafts of any engine affects the softness of its operation, watch the video below; good luck to everyone!