Before moving on to the description of the receiver, let's consider the frequency distribution for radio control equipment. And let's start here with laws and regulations. For all radio equipment, the distribution of frequency resources in the world is carried out by the International Committee on Radio Frequencies. It has several subcommittees on zones of the globe. Therefore, in different areas of the Earth, different frequency ranges are allocated for radio control. Moreover, the subcommittees only recommend frequency allocations to the states in their zone, and the national committees, as part of the recommendations, introduce their own restrictions. In order not to inflate the description beyond measure, let us consider the distribution of frequencies in the American region, Europe and in our country.
In general, the first half of the VHF radio wave range is used for radio control. In the American region, these are the bands 50, 72 and 75 MHz. Moreover, 72 MHz is exclusively for flying models. In Europe, the bands allowed are 26, 27, 35, 40 and 41 MHz. The first and last in France, the rest throughout the EU. In our native country, the permitted range is 27 MHz and, since 2001, a small portion of the 40 MHz range. Such a narrow distribution of radio frequencies could hinder the development of radio modeling. But, as Russian thinkers correctly noted back in the 18th century, “the severity of laws in Rus' is compensated by loyalty to their non-compliance.” In reality, in Russia and in the territory of the former USSR, the 35 and 40 MHz bands according to the European layout are widely used. Some try to use American frequencies, and sometimes successfully. However, most often these attempts are thwarted by interference from VHF radio broadcasting, which has been using precisely this range since Soviet times. In the 27-28 MHz range, radio control is allowed, but can only be used for ground models. The fact is that this range is also given over to civil communications. There are a huge number of “Wokie-talkie” stations operating there. Near industrial centers, the interference situation in this range is very bad.
The 35 and 40 MHz bands are the most acceptable in Russia, and the latter is permitted by law, although not all of it. Of the 600 kilohertz of this range, only 40 have been legalized in our country, from 40.660 to 40.700 MHz (see Decision of the State Committee for Radio Frequencies of Russia dated March 25, 2001, Protocol N7/5). That is, out of 42 channels, only 4 are officially allowed in our country. But they may also contain interference from other radio media. In particular, about 10,000 Len radio stations were produced in the USSR for use in the construction and agro-industrial complex. They operate in the range 30 - 57 MHz. Most of them are still actively exploited. Therefore, no one is safe from interference here either.
Note that the legislation of many countries allows the use of the second half of the VHF range for radio control, but such equipment is not commercially produced. This is due to the complexity in the recent past of the technical implementation of frequency generation in the range above 100 MHz. Currently, the element base makes it possible to easily and cheaply form a carrier up to 1000 MHz, however, the inertia of the market is still hindering the mass production of equipment in the upper part of the VHF range.
To ensure reliable untuned communication, the carrier frequency of the transmitter and the receiving frequency of the receiver must be sufficiently stable and switchable to ensure joint interference-free operation of several sets of equipment in one place. These problems are solved by using a quartz resonator as a frequency-setting element. To be able to switch frequencies, the quartz is made replaceable, i.e. a niche with a connector is provided in the transmitter and receiver housings, and the quartz of the desired frequency is easily changed directly in the field. In order to ensure compatibility, frequency ranges are divided into separate frequency channels, which are also numbered. The interval between channels is defined as 10 kHz. For example, a frequency of 35.010 MHz corresponds to 61 channels, 35.020 to 62 channels, and 35.100 to 70 channels.
The joint operation of two sets of radio equipment on the same field on the same frequency channel is in principle impossible. Both channels will continuously glitch regardless of whether they are in AM, FM or PCM mode. Compatibility is achieved only by switching equipment sets to different frequencies. How is this achieved practically? Everyone who arrives at an airfield, highway or body of water is obliged to look around to see if there are other modelers there. If they are, you need to go around everyone and ask in what range and on what channel their equipment operates. If there is at least one modeler whose channel coincides with yours, and you do not have replaceable crystals, negotiate with him to turn on the equipment only one at a time, and in general, stay close to him. At competitions, the frequency compatibility of the equipment of different participants is the concern of the organizers and judges. Abroad, to identify channels, it is customary to attach special pennants to the transmitter antenna, the color of which determines the range, and the numbers on it indicate the number (and frequency) of the channel. However, it is better for us to adhere to the order described above. Moreover, since transmitters on adjacent channels can interfere with each other due to the sometimes occurring synchronous drift of the transmitter and receiver frequencies, careful modelers try not to work in the same field on adjacent frequency channels. That is, channels are chosen so that there is at least one free channel between them.
For clarity, here are tables of channel numbers for the European layout:
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Channels that are legally permitted for use in Russia are highlighted in bold. In the 27 MHz band, only preferred channels are shown. In Europe, the channel spacing is 10 kHz.
And here is the layout table for America:
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In America, they have their own numbering, and the interchannel interval is already 20 kHz.
To fully understand quartz resonators, we will run a little ahead and say a few words about receivers. All receivers in commercially produced equipment are built according to a superheterodyne circuit with one or two conversions. We won’t explain what this is, but anyone familiar with radio engineering will understand. So, frequency formation in the transmitter and receiver of different manufacturers occurs differently. In a transmitter, a quartz resonator can be excited at the fundamental harmonic, after which its frequency doubles or triples, and maybe even at the 3rd or 5th harmonic. In the receiver local oscillator, the excitation frequency can be either higher than the channel frequency or lower by the intermediate frequency. Double conversion receivers have two intermediate frequencies (typically 10.7 MHz and 455 kHz), so the number of possible combinations is even greater. Those. the frequencies of the quartz resonators of the transmitter and receiver never coincide, both with the frequency of the signal that will be emitted by the transmitter, and with each other. Therefore, equipment manufacturers have agreed to indicate on the quartz resonator not its real frequency, as is customary in other radio engineering, but its purpose: TX - transmitter, RX - receiver, and the frequency (or number) of the channel. If the quartz of the receiver and transmitter are swapped, the equipment will not work. True, there is one exception: some devices with AM can also work with mixed quartz, provided that both quartz are on the same harmonic, but the frequency on the air will be 455 kHz higher or lower than that indicated on the quartz. However, the range will decrease.
It was noted above that a transmitter and receiver from different manufacturers can work together in PPM mode. What about quartz resonators? Whose should I put where? We can recommend installing a native quartz resonator in each device. Quite often this helps. But not always. Unfortunately, tolerances for the manufacturing accuracy of quartz resonators from different manufacturers vary significantly. Therefore, the possibility of joint operation of specific components from different manufacturers and with different quartz can only be established experimentally.
And further. In principle, in some cases it is possible to install quartz resonators from another manufacturer on equipment from one manufacturer, but we do not recommend this. A quartz resonator is characterized not only by frequency, but also by a number of other parameters, such as quality factor, dynamic resistance, etc. Manufacturers design equipment for a specific type of quartz. The use of another may generally reduce the reliability of the radio control.
Brief summary:
- The receiver and transmitter require crystals in the exact range for which they are designed. Quartz will not work on a different range.
- It is better to take quartz from the same manufacturer as the equipment, otherwise performance is not guaranteed.
- When purchasing quartz for a receiver, you need to clarify whether it has one conversion or not. Crystals for double conversion receivers will not work in single conversion receivers, and vice versa.
Types of receivers
As we have already indicated, a receiver is installed on the controlled model.
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Radio control receivers are designed to work with only one type of modulation and one type of coding. Thus, there are AM, FM and PCM receivers. Moreover, RSM varies from company to company. If on the transmitter you can simply switch the encoding method from PCM to PPM, then the receiver must be replaced with another.
The receiver is made according to a superheterodyne circuit with two or one conversion. Receivers with two conversions have, in principle, better selectivity, i.e. better filter out interference with frequencies outside the working channel. As a rule, they are more expensive, but their use is justified for expensive, especially flying models. As already noted, quartz resonators for the same channel for receivers with two and one conversion are different and not interchangeable.
If you arrange receivers in increasing order of noise immunity (and, unfortunately, price), then the series will look like this:
- one conversion and AM
- one conversion and FM
- two conversions and FM
- one conversion and RSM
- two conversions and RSM
When choosing a receiver for your model from this range, you need to take into account its purpose and cost. From the point of view of noise immunity, it is not bad to install a PCM receiver on the training model. But by driving the model into concrete during training, you will lighten your wallet by a much greater amount than with a single-conversion FM receiver. Likewise, if you install an AM receiver or a simplified FM receiver on a helicopter, you will seriously regret it later. Especially if you fly near large cities with developed industry.
The receiver can only operate in one frequency range. Converting a receiver from one band to another is theoretically possible, but it is hardly justified economically, since this work is very labor intensive. It can only be carried out by highly qualified engineers in a radio laboratory. Some frequency ranges for receivers are divided into subbands. This is due to the large bandwidth (1000 kHz) with a relatively low first IF (455 kHz). In this case, the main and mirror channels fall into the passband of the receiver preselector. In this case, it is generally impossible to ensure selectivity over the mirror channel in a receiver with one conversion. Therefore, in the European layout, the 35 MHz band is divided into two sections: from 35.010 to 35.200 - this is the “A” subband (channels 61 to 80); from 35.820 to 35.910 - subband “B” (channels 182 to 191). In the American layout, two subbands are also allocated in the 72 MHz band: from 72.010 to 72.490, the “Low” subband (channels 11 to 35); from 72.510 to 72.990 - “High” (channels 36 to 60). Different receivers are available for different subbands. In the 35 MHz range they are not interchangeable. In the 72 MHz range they are partially interchangeable on frequency channels near the border of the subbands.
The next sign of the type of receiver is the number of control channels. Receivers are available with a number of channels from two to twelve. At the same time, circuitry, i.e. based on their “gibles”, receivers for 3 and 6 channels may not differ at all. This means that a three-channel receiver may have decoded signals of the fourth, fifth and sixth channels, but there are no connectors on the board for connecting additional servos.
To make full use of the connectors, receivers often do not have a separate power connector. In the case when servos are not connected to all channels, the power cable from the on-board switch is connected to any free output. If all outputs are enabled, then one of the servos is connected to the receiver through a splitter (the so-called Y-cable), to which the power is connected. When the receiver is powered from a power battery through a speed controller with the BEC function, there is no need for a special power cable at all - the power is supplied through the signal cable of the speed controller. Most receivers are designed to operate at a nominal voltage of 4.8 volts, which corresponds to a battery of four nickel-cadmium batteries. Some receivers allow the use of on-board power from 5 batteries, which improves the speed and power parameters of some servos. Here you need to be attentive to the operating instructions. Receivers that are not designed for increased supply voltage may burn out in this case. The same applies to steering gears, whose service life may drop sharply.
Receivers for ground models are often produced with a shortened wire antenna, which is easier to place on the model. It should not be lengthened, since this will not increase, but rather reduce the range of reliable operation of the radio control equipment.
For models of ships and cars, receivers in a waterproof housing are available:
Receivers with a synthesizer are available for athletes. There is no replaceable quartz, and the working channel is set by multi-position switches on the receiver body:
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With the advent of the class of ultra-light flying models - indoor ones, the production of special very small and light receivers began:
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These receivers often do not have a rigid polystyrene housing and are housed in heat-shrinkable PVC tubing. They can be built into an integrated speed controller, which generally reduces the weight of on-board equipment. If there is a tough competition for grams, it is allowed to use miniature receivers without a housing at all. Due to the active use of lithium-polymer batteries in ultra-light flying models (their specific capacity is several times greater than that of nickel batteries), specialized receivers have appeared with a wide range of supply voltage and a built-in speed controller:
Let's summarize what was said above.
- The receiver operates only in one frequency range (subband)
- The receiver only works with one type of modulation and coding
- The receiver must be selected according to the purpose and cost of the model. It is illogical to install an AM receiver on a helicopter model, and a double-conversion PCM receiver on a simple training model.
Receiver device
As a rule, the receiver is housed in a compact housing and is made on a single printed circuit board. A wire antenna is attached to it. The case has a niche with a connector for a quartz resonator and contact groups of connectors for connecting actuators, such as servos and speed controllers.
The radio signal receiver and decoder are mounted on the printed circuit board.
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A replaceable quartz resonator sets the frequency of the first (only) local oscillator. The values of intermediate frequencies are standard for all manufacturers: the first IF is 10.7 MHz, the second (the only one) is 455 kHz.
The output of each channel of the receiver decoder is connected to a three-pin connector, where, in addition to the signal signal, there are ground and power contacts. The structure of the signal is a single pulse with a period of 20 ms and a duration equal to the value of the channel pulse of the PPM signal generated in the transmitter. The PCM decoder output has the same signal as PPM. In addition, the PCM decoder contains a so-called Fail-Safe module, which allows you to bring the steering gears to a predetermined position if the radio signal is lost. More information about this is written in the article "PPM or PCM?".
Some receiver models have a special connector to provide the DSC (Direct servo control) function - direct control of servos. To do this, a special cable connects the trainer connector of the transmitter and the DSC connector of the receiver. After which, with the RF module turned off (even in the absence of quartz and a faulty RF part of the receiver), the transmitter directly controls the servos on the model. The function can be useful for ground-based debugging of the model, so as not to unnecessarily pollute the airwaves, as well as for searching for possible faults. At the same time, the DSC cable is used to measure the supply voltage of the on-board battery - this is provided for in many expensive transmitter models.
Unfortunately, receivers break down much more often than we would like. The main reasons are impacts from model crashes and strong vibrations from power plants. Most often this happens when the modeler neglects the recommendations for damping the receiver when placing the receiver inside the model. It's hard to overdo it here, and the more foam and sponge rubber you use, the better. The most sensitive element to shock and vibration is the replaceable quartz resonator. If after an impact your receiver malfunctions, try changing the quartz - in half the cases this helps.
Combating on-board interference
A few words about interference on board the model and how to deal with it. In addition to interference from the air, the model itself may have sources of its own interference. They are located close to the receiver and, as a rule, have broadband radiation, i.e. They act simultaneously at all frequencies of the range, and therefore their consequences can be disastrous. A typical source of interference is a commutator traction motor. They learned to deal with its interference by powering it through special anti-interference circuits, consisting of a capacitor shunting each brush to the housing and a series-connected inductor. For powerful electric motors, separate power is used for the motor itself and the receiver from a separate, non-running battery. The stroke controller provides for optoelectronic decoupling of control circuits from power circuits. Oddly enough, brushless electric motors create no less level of interference than brushed motors. Therefore, for powerful motors it is better to use speed controllers with optical isolation and a separate battery to power the receiver.
On models with gasoline engines and spark ignition, the latter is a source of powerful interference over a wide frequency range. To combat interference, shielding is used on the high-voltage cable, the spark plug tip and the entire ignition module. Magneto ignition systems create slightly less noise than electronic ignition systems. In the latter, power is supplied necessarily from a separate battery, not from the on-board one. In addition, they use a spatial separation of on-board equipment from the ignition system and engine by at least a quarter of a meter.
The third most important source of interference is servos. Their interference becomes noticeable on large models, where many powerful servos are installed, and the cables connecting the receiver to the servos become long. In this case, it helps to put small ferrite rings on the cable near the receiver so that the cable makes 3-4 turns on the ring. You can do this yourself, or buy ready-made branded extension servo cables with ferrite rings. A more radical solution is to use different batteries to power the receiver and servos. In this case, all receiver outputs are connected to servo cables through a special device with optical isolation. You can make such a device yourself, or buy a ready-made branded one.
In conclusion, let us mention something that is not yet very common in Russia - giant models. These include flying models weighing more than eight to ten kilograms. Failure of the radio channel with the subsequent crash of the model in this case is fraught not only with material losses, which are considerable in absolute terms, but also poses a threat to the life and health of others. Therefore, the legislation of many countries obliges modellers to use complete duplication of on-board equipment on such models: i.e. two receivers, two on-board batteries, two sets of servos that control two sets of rudders. In this case, any single failure does not lead to a crash, but only slightly reduces the effectiveness of the rudders.
Homemade equipment?
In conclusion, a few words to those who want to make their own radio control equipment. In the opinion of authors who have been involved in amateur radio for many years, in most cases this is not justified. The desire to save money on the purchase of ready-made serial equipment is deceptive. And the result is unlikely to please you with its quality. If you don’t have enough money even for a simple set of equipment, buy a used one. Modern transmitters become obsolete morally before they wear out physically. If you are confident in your capabilities, take a faulty transmitter or receiver at a bargain price - repairing it will still give better results than making a homemade one.
Remember that the “wrong” receiver is at most one ruined model of its own, but the “wrong” transmitter with its out-of-band radio emissions can destroy a bunch of other people’s models, which may turn out to be more expensive than its own.
In case the urge to make circuits is irresistible, first search the Internet. There is a very high probability that you will be able to find ready-made diagrams - this will save you time and avoid many mistakes.
For those who are more a radio amateur at heart than a modeler, there is a wide field for creativity, especially where the serial manufacturer has not yet reached. Here are a few topics worth tackling yourself:
- If you have a branded case from cheap equipment, you can try to make computer stuffing for it. A good example here would be MicroStar 2000 - an amateur development that has complete documentation.
- In connection with the rapid development of indoor radio models, it is of particular interest to manufacture a transmitter and receiver module using infrared rays. Such a receiver can be made smaller (lighter) than the best miniature radios, much cheaper, and have an electric motor control key built into it. The range of the infrared channel in the gym is quite enough.
- In amateur conditions, you can quite successfully make simple electronics: speed controllers, on-board mixers, tachometers, chargers. This is much easier than making the stuffing for the transmitter, and is usually more worthwhile.
Conclusion
After reading articles on radio control transmitters and receivers, you were able to decide what kind of equipment you need. But some questions, as always, remained. One of them is how to buy equipment: in bulk, or in a set, which includes a transmitter, receiver, batteries for them, servos and a charger. If this is the first device in your modeling practice, it is better to buy it as a set. This automatically solves compatibility and packaging problems. Then, when your model fleet increases, you can buy additional receivers and servos separately, in accordance with the other requirements of the new models.
When using higher voltage on-board power with a five-cell battery, choose a receiver that can handle this voltage. Also pay attention to the compatibility of the separately purchased receiver with your transmitter. Receivers are produced by a much larger number of companies than transmitters.
A few words about a detail that is often neglected by novice modelers - the on-board power switch. Specialized switches are made in a vibration-resistant design. Replacing them with untested toggle switches or switches from radio equipment can cause an in-flight failure with all the ensuing consequences. Be attentive to both the main thing and the little things. There are no minor details in radio modeling. Otherwise, according to Zhvanetsky: “one wrong move and you are a father.”
Camber Angle
Wheel with negative camber angle.
Camber angle is the angle between the vertical axis of the wheel and the vertical axis of the car when you look from the front or rear of the car. If the top of the wheel is further outward than the bottom of the wheel, it is called positive camber. If the bottom of the wheel is further outward than the top of the wheel, it is called negative camber.
The camber angle affects the vehicle's handling characteristics. As a general rule, increasing negative camber improves grip on that wheel when cornering (within certain limits). This is because it gives us a tire with better distribution of cornering forces, a more optimal angle to the road, increasing the contact patch and transmitting forces through the vertical plane of the tire rather than lateral force through the tire. Another reason for using negative camber is the tendency of the rubber tire to roll relative to itself when cornering. If a wheel has zero camber, the inside edge of the tire's contact patch begins to rise from the ground, thereby reducing the contact patch area. By using negative camber, this effect is reduced, thus maximizing the tire's contact patch.
On the other hand, for maximum straight-line acceleration, maximum grip will be obtained when the camber angle is zero and the tire tread is parallel to the road. Proper camber angle distribution is a major factor in suspension design, and must include not only an idealized geometric model, but also the actual behavior of the suspension components: flex, distortion, elasticity, etc.
Most cars have some form of double wishbone suspension, which allows you to adjust the camber angle (as well as the camber gain).
Camber Intake
Camber gain is a measure of how the camber angle changes as the suspension is compressed. This is determined by the length of the control arms and the angle between the upper and lower control arms. If the upper and lower control arms are parallel, the camber will not change as the suspension is compressed. If the angle between the suspension arms is significant, the camber will increase as the suspension is compressed.
A certain amount of camber gain is useful in keeping the tire surface parallel to the ground when the vehicle leans into a corner.
Note: The suspension arms should either be parallel or should be closer together on the inside (car side) than on the wheel side. Having suspension arms that are closer together on the wheel side rather than on the car side will result in radically different camber angles (the car will behave erratically).
The increase in camber will determine how the car's roll center behaves. The car's roll center, in turn, determines how weight transfer will occur when cornering, and this has a significant impact on handling (see more on this below).
Caster Angle
The caster angle (or caster) is the angular deviation from the vertical axis of the wheel suspension in a car, measured in the longitudinal direction (the angle of the steering axis of the wheel when viewed from the side of the car). This is the angle between the joint line (in a car, the imaginary line that runs through the center of the upper ball joint to the center of the lower ball joint) and the vertical. Caster angle can be adjusted to optimize vehicle handling in certain driving situations.
The wheel pivot points are angled such that a line drawn through them intersects the road surface slightly in front of the wheel contact point. The purpose of this is to provide some degree of self-centering in the steering - the wheel rolls behind the wheel's steering axis. This makes the car easier to control and improves its stability on straight roads (reducing the tendency to deviate from the trajectory). Excessive caster angles will make steering feel heavier and less responsive, however, in off-road competition, higher caster angles are used to improve camber gain when cornering.
Toe-In and Toe-Out
Toe is the symmetrical angle that each wheel makes with the longitudinal axis of the car. Toe-in is when the front of the wheels is directed towards the central axis of the car.
Front toe angle
Basically, increased toe-in (the fronts of the wheels are closer together than the rears of the wheels) provides more straight-line stability at the cost of some sluggish cornering response, as well as slightly increased drag since the wheels are now running slightly sideways.
Spreading out the front wheels will result in more responsive steering and faster corner entry. However, front toe usually means a less stable car (more jerky).
Rear toe angle
Your vehicle's rear wheels should always be aligned with some degree of toe (although 0 degrees toe is acceptable in some conditions). Basically, the greater the rear toe-in, the more stable the car will be. However, keep in mind that increasing the toe angle (front or rear) will result in reduced speed on straightaways (especially when using stock motors).
Another related concept is that toe that is suitable for a straight section will not be suitable for a turn, since the inside wheel must follow a smaller radius than the outside wheel. To compensate for this, steering linkages usually follow more or less the Ackermann principle for steering, modified to suit the characteristics of a particular car model.
Ackerman angle
The Ackermann principle in steering is a geometric arrangement of steering rods of a car model, designed to solve the problem of the need for the inner and outer wheels to follow different radii during a turn.
When a car turns, it follows a path that is part of its turning circle, the center of which is somewhere along a line through the rear axle. The rotated wheels should be tilted so that they both make an angle of 90 degrees with a line drawn from the center of the circle through the center of the wheel. Because the wheel on the outside of the turn will be on a larger radius than the wheel on the inside of the turn, it must be turned to a different angle.
The Ackermann steering principle automatically adjusts this by moving the steering joints inward so that they are on a line drawn between the steering axis of the wheel and the center of the rear axle. The steering joints are connected by a rigid rod, which in turn is part of the steering mechanism. This arrangement ensures that at any angle of rotation, the centers of the circles along which the wheels follow will be at one common point.
Slip angle
The slip angle is the angle between the actual path of the wheel and the direction in which it is pointing. The slip angle results in a lateral force perpendicular to the direction of wheel motion - corner force. This angular force increases approximately linearly for the first few degrees of slip angle, and then increases nonlinearly until it reaches a maximum, after which it begins to decrease (as the wheel begins to slip).
A non-zero slip angle occurs due to tire deformation. As the wheel rotates, the frictional force between the tire's contact patch and the road causes individual tread "elements" (infinitesimal portions of the tread) to remain stationary relative to the road.
This deflection of the tire results in an increase in slip angle and corner force.
Since the forces that act on the wheels from the weight of the car are distributed unevenly, the lateral slip angle of each wheel will be different. The relationship between the slip angles will determine the behavior of the car in a given turn. If the ratio of front slip angle to rear slip angle is greater than 1:1, the vehicle will be susceptible to understeer, and if the ratio is less than 1:1, it will promote oversteer. The actual instantaneous slip angle depends on many factors, including road surface conditions, but a vehicle's suspension can be designed to provide specific dynamic characteristics.
The main means of adjusting the resulting lateral slip angles is to change the relative front-to-back roll by adjusting the amount of front and rear lateral weight transfer. This can be achieved by changing the height of the roll centers, or by adjusting the roll severity, by changing the suspension, or by adding anti-roll bars.
Weight Transfer
Weight transfer refers to the redistribution of weight supported by each wheel during acceleration (longitudinal and lateral). This includes accelerating, braking or turning. Understanding weight transfer is critical to understanding vehicle dynamics.
Weight transfer occurs as the center of gravity (CoG) shifts during vehicle maneuvers. Acceleration causes the center of mass to rotate around a geometric axis, resulting in a shift in the center of gravity (CoG). Front-to-rear weight transfer is proportional to the ratio of the vehicle's center of gravity height to the car's wheelbase, and lateral weight transfer (front and rear total) is proportional to the vehicle's center of gravity height to wheelbase ratio, as well as the height of its roll center (explained below).
For example, when a car accelerates, its weight is transferred towards the rear wheels. You can observe this as the car noticeably leans backwards, or "squats." Conversely, when braking, weight is transferred towards the front wheels (the nose “dives” towards the ground). Likewise, during changes in direction (lateral acceleration), weight is transferred to the outside of the turn.
Weight transfer causes a change in the available traction on all four wheels when the vehicle brakes, accelerates, or turns. For example, since weight transfer occurs forward when braking, the front wheels do most of the braking work. This shift in "work" to one pair of wheels from the other results in a loss of overall available traction.
If lateral weight transfer reaches the wheel load at one end of the vehicle, the inside wheel at that end will lift, causing a change in handling characteristics. If this weight transfer reaches half the vehicle's weight, it begins to roll over. Some large trucks will roll over before sliding, but road cars usually only roll over when they go off the road.
Roll center
A car's roll center is an imaginary point marking the center around which the car rolls (in corners) when viewed from the front (or rear).
The position of the geometric roll center is dictated solely by the suspension geometry. The official definition of roll center is: "The point on the cross section through any pair of wheel centers at which lateral forces can be applied to the sprung mass without causing suspension roll."
The value of the roll center can only be estimated when the center of mass of the vehicle is taken into account. If there is a difference between the positions of the center of mass and the center of roll, then a “moment arm” is created. When a car experiences lateral acceleration in a corner, the roll center moves up or down, and the size of the moment arm, combined with the stiffness of the springs and anti-roll bars, dictates the amount of roll in the corner.
The geometric roll center of a vehicle can be found using the following basic geometric procedures when the vehicle is in a static state: 
Draw imaginary lines parallel to the suspension arms (red). Then draw imaginary lines between the intersection points of the red lines and the lower centers of the wheels, as shown in the picture (in green). The point where these green lines intersect is the roll center.
You need to note that the roll center moves when the suspension compresses or lifts, so it is actually the instantaneous roll center. How much this roll center moves as the suspension compresses is determined by the length of the control arms and the angle between the upper and lower control arms (or adjustable suspension links).
As the suspension is compressed, the roll center rises higher and the moment arm (the distance between the roll center and the vehicle's center of gravity (CoG in the figure)) will decrease. This will mean that when the suspension is compressed (for example, when cornering), the car will have less tendency to roll (which is good if you don't want to roll over).
When you use high-grip (foam rubber) tires, you must set the suspension arms so that the roll center rises significantly as the suspension is compressed. On-road ICE cars have very aggressive control arm angles to raise roll center during cornering and prevent rollovers when using foam tires.
The use of parallel, equal-length suspension arms results in a fixed roll center. This means that when the car is tilted, the moment arm will force the car to roll more and more. As a general rule, the higher your vehicle's center of gravity, the higher its roll center must be to avoid rollovers.
"Bump Steer" is the tendency of a wheel to turn as it moves up the suspension travel. On most vehicles, the front wheels typically experience toe (the front of the wheel moves outward) as the suspension is compressed. This allows for roll understeer (when you hit a bump in a corner, the car tends to straighten out). Excessive "bump steer" increases tire wear and makes the car jerky on uneven roads.
"Bump Steer" and roll center
On a bump, both wheels rise together. When banking, one wheel goes up and the other goes down. This usually produces more toe in on one wheel and more toe out in the other wheel, thus producing a turning effect. In simple analysis you can simply assume that roll steering is similar to "bump steer", but in practice things like the anti-roll bar have an effect that changes this.
"Bump steer" can be increased by raising the outer joint or lowering the inner joint. Minor adjustments are usually required.
Understeer
Understeer is a condition of a car's controllability in a turn, in which the car's circular path has a noticeably larger diameter than the circle indicated by the direction of the wheels. This effect is the opposite of oversteer, and in simple terms, understeer is a condition in which the front wheels do not follow the path set by the driver for cornering, but instead follow a straighter path.
This is also often called pushing out or refusing to turn. The car is called “clamped” because it is stable and far from the tendency to skid.
Just like oversteer, understeer has many sources, such as mechanical clutch, aerodynamics and suspension.
Traditionally, understeer occurs when the front wheels have insufficient grip during a turn, so the front end of the car has less mechanical grip and cannot follow the line through the turn.
Camber angles, ground clearance and center of gravity are important factors that determine the understeer/oversteer condition.
It is a general rule that manufacturers deliberately tune cars to have slight understeer. If a car has slight understeer, it will be more stable (within the driver's average ability) during sudden changes in direction.
How to tune your car to reduce understeer
You should start by increasing the negative camber of the front wheels (never exceed -3 degrees for on-road vehicles and 5-6 degrees for off-road vehicles).
Another way to reduce understeer is to reduce the negative camber of the rear wheels (it should always be<=0 градусов).
Another way to reduce understeer is to stiffen or remove the front sway bar (or stiffen the rear sway bar).
It is important to note that any adjustments are subject to compromise. The car has a limited amount of total grip that can be distributed between the front and rear wheels.
Oversteer
A car oversteers when the rear wheels do not follow the front wheels, but instead slide toward the outside of the corner. Oversteer can lead to skidding.
A car's tendency to oversteer is influenced by several factors, such as mechanical clutch, aerodynamics, suspension and driving style.
The limit of oversteer occurs when the rear tires exceed their lateral grip limit during a turn before the front tires do, thereby causing the car's rear to point toward the outside of the corner. In general, oversteer is a condition where the slip angle of the rear tires exceeds the slip angle of the front tires.
Rear-wheel drive cars are more prone to oversteer, especially when using the throttle in tight corners. This is because the rear tires must withstand lateral forces and engine thrust.
A car's tendency to oversteer usually increases when the front suspension is softened or the rear suspension is stiffened (or when a rear anti-roll bar is added). Camber angles, ground clearance and tire temperature rating can also be used to adjust the car's balance.
A car with oversteer may also be called "loose" or "unclamped".
How do you differentiate between oversteer and understeer?
When you go into a corner, oversteer is when the car turns sharper than you expect, and understeer is when the car turns less than you expect.
Oversteer or understeer, that is the question
As mentioned earlier, any adjustments are a matter of compromise. The car has limited grip that can be distributed between the front and rear wheels (this can be expanded using aerodynamics, but that's another story).
All sports cars develop a higher lateral (ie side slip) speed than is determined by the direction in which the wheels are pointing. The difference between the circle in which the wheels roll and the direction in which they point is the slip angle. If the slip angles of the front and rear wheels are the same, the car has neutral handling balance. If the slip angle of the front wheels exceeds the slip angle of the rear wheels, the car is said to have understeer. If the slip angle of the rear wheels exceeds the slip angle of the front wheels, the car is said to have oversteer.
Just remember that an understeering car hits the guardrail with its front end, an oversteering car hits the guardrail with its rear end, and a neutral handling car hits the guardrail with both ends at the same time.
Other important factors to consider
Any vehicle can experience understeer or oversteer depending on road conditions, speed, available traction and driver input. Vehicle design, however, tends to reach an individual "limit" condition where the vehicle reaches and exceeds its traction limits. “Marginal understeer” refers to a vehicle that, due to design features, tends to understeer when angular accelerations exceed tire grip.
The ultimate handling balance is a function of front/rear relative roll resistance (suspension stiffness), front/rear weight distribution, and front/rear tire grip. A car with a heavy front end and low rear roll resistance (due to soft springs and/or low stiffness or lack of rear anti-roll bars) will tend to experience extreme understeer: its front tires, being more heavily loaded even when static, will reach the limits of their grip earlier than the rear tires and thus develop larger slip angles. Front-wheel drive cars are also prone to understeer because not only do they typically have a heavy front end, but sending power to the front wheels also reduces their available grip for turning. This often results in a "shudder" effect on the front wheels as grip changes unexpectedly due to the transfer of power from the engine to the road and steering.
Although understeer and oversteer can both cause a loss of control, many manufacturers design their cars for extreme understeer on the assumption that it is easier for the average driver to control than extreme oversteer. Unlike extreme oversteer, which often requires several steering adjustments, understeer can often be reduced by reducing speed.
Understeer can not only occur during acceleration in a corner, it can also occur during hard braking. If the brake balance (braking force on the front and rear axle) is too forward, it can cause understeer. This is caused by the front wheels locking and loss of effective control. The opposite effect can also occur; if the brake balance is too far back, the rear end of the car will skid.
Athletes on asphalt surfaces generally prefer a neutral balance (with a slight tendency towards understeer or oversteer, depending on the track and driving style), as understeer and oversteer lead to a loss of speed during cornering. In rear-wheel drive cars, understeer generally works better because the rear wheels need some available grip to accelerate the car out of corners.
Spring rate
Spring stiffness is a tool for adjusting the vehicle's ground clearance and its suspension position. Spring stiffness is a coefficient used to measure the amount of compression resistance.
Springs that are too hard or too soft will effectively result in the car having no suspension at all.
Spring stiffness referred to the wheel (Wheel rate)
The spring rate referred to the wheel is the effective spring rate when measured at the wheel.
The spring rate applied to the wheel is usually equal to or significantly less than the spring rate itself. Typically, the springs are mounted on the control arms or other parts of the suspension articulation system. Assuming that as the wheel moves 1 inch, the spring moves 0.75 inches, the leverage ratio would be 0.75:1. The spring rate referred to the wheel is calculated by squaring the lever ratio (0.5625), multiplying by the spring rate and by the sine of the spring angle. The ratio is squared due to two effects. The ratio is applied to force and distance traveled.
Suspension Travel
Suspension travel is the distance from the bottom of the suspension travel (when the car is on a stand and the wheels are hanging freely) to the top of the suspension travel (when the car's wheels can no longer go higher). If a wheel reaches its lower or upper limit, it can cause serious control problems. "Reaching the limit" can be caused by the suspension, chassis, etc. moving beyond its limits. or touching the road with the body or other components of the vehicle.
Damping
Damping is the control of motion or vibration through the use of hydraulic shock absorbers. Damping controls the speed and resistance of a vehicle's suspension. A car without damping will oscillate up and down. With the help of suitable damping, the car will return back to its normal state in a minimum amount of time. Damping in modern vehicles can be controlled by increasing or decreasing the fluid viscosity (or piston bore size) in the shock absorbers.
Anti-dive and Anti-squat
Anti-dive and anti-squat are expressed as a percentage and refer to the dive of the front of the car when braking and the squat of the rear of the car when accelerating. They can be considered twins for braking and acceleration, while the roll center height works in corners. The main reason for their difference is the different design goals for the front and rear suspension, while the suspension is usually symmetrical between the right and left sides of the car.
The percentage of anti-dive and anti-squat is always calculated relative to the vertical plane that intersects the vehicle's center of gravity. Let's look at anti-squat first. Determine the location of the rear instantaneous center of the suspension when looking at the car from the side. Draw a line from the tire contact patch through the instantaneous center, this will be the force vector of the wheel. Now draw a vertical line through the center of gravity of the car. Anti-squat is the ratio between the height of the intersection point of the wheel force vector and the height of the center of gravity, expressed as a percentage. An anti-squat value of 50% would mean that the force vector during acceleration passes halfway between the ground and the center of gravity. 
Anti-dive is the counterpart of anti-squat and works for the front suspension during braking.
Circle of forces
The circle of forces is a useful way to think about the dynamic interaction between a car's tire and the road surface. In the diagram below, we are looking at the wheel from above, so the road surface lies in the x-y plane. The car to which the wheel is attached moves in the positive y direction. 
In this example, the car will turn right (ie the positive x direction is towards the center of the turn). Note that the plane of rotation of the wheel is at an angle to the actual direction in which the wheel is moving (in the positive y direction). This angle is the slip angle.
The limit of the value of F is limited by the dotted circle, F can be any combination of the components Fx (turn) and Fy (acceleration or braking) that does not exceed the dotted circle. If the combination of forces Fx and Fy goes outside the circle, the tire loses traction (you slide or skid).
In this example, the tire creates a force component in the x direction (Fx) which, when transmitted to the vehicle's chassis through the suspension system in combination with similar forces from the remaining wheels, will cause the vehicle to turn to the right. The diameter of the force circle, and therefore the maximum horizontal force a tire can produce, is influenced by many factors, including tire design and condition (age and temperature range), road surface quality, and vertical wheel load.
Critical speed
A car that understeers has an accompanying instability mode called critical speed. As you approach this speed, the control becomes increasingly sensitive. At critical speed, the yaw rate becomes infinite, that is, the car continues to turn even with the wheels straightened. At speeds above the critical speed, simple analysis shows that the steering angle must be reversed (counter-steering). A car that understeers is not affected by this, which is one of the reasons why high-speed cars are tuned to understeer.
Finding the golden mean (or a balanced car model)
A car that does not suffer from oversteer or understeer when driven to its limit has neutral balance. It seems intuitive that athletes would prefer a little oversteer to spin the car around a corner, but this is not commonly used for two reasons. Early acceleration, as soon as the car passes the apex of the turn, allows the car to gain additional speed on the subsequent straight section. The driver who accelerates earlier or faster has a big advantage. The rear tires require some excess grip to accelerate the car in this critical phase of the turn, while the front tires can dedicate all their grip to the turn. Therefore, the car should be tuned with a slight tendency to understeer or should be slightly "pinched". Also, a car that oversteers is jerky, increasing the likelihood of losing control during long events or when reacting to an unexpected situation.
Please note that this only applies to competition on road surfaces. Competitions on clay are a completely different story.
Some successful drivers prefer a little oversteer in their cars, preferring a car that's quieter and easier to corner. It should be noted that judgment about the handling balance of a car model is not objective. Driving style is a major factor in the apparent balance of a car. Therefore, two drivers with identical car models often use them with different balance settings. And both can call the balance of their cars "neutral."
On the eve of important competitions, before completing the assembly of a KIT car kit, after an accident, at the time of purchasing a car with partial assembly, and in a number of other predictable or spontaneous cases, there may be an urgent need to buy a remote control for a radio-controlled car. How not to miss the choice, and what features should be given special attention? This is exactly what we will tell you below!
Types of remote controls
The control equipment consists of a transmitter, with the help of which the modeler sends control commands, and a receiver installed on the car model, which catches the signal, deciphers it and transmits it for further execution by actuators: servos, regulators. This is exactly how the car drives, turns, stops, as soon as you press the appropriate button or perform the necessary combination of actions on the remote control.
Car modelers mainly use pistol-type transmitters, when the remote control is held in the hand like a pistol. The gas trigger is located under the index finger. When you press back (towards you), the car moves, if you press in the front, it slows down and stops. If you do not apply force, the trigger will return to the neutral (middle) position. There is a small wheel on the side of the remote control - this is not a decorative element, but the most important control tool! With its help all turns are performed. Rotating the wheel clockwise turns the wheels to the right, counterclockwise turns the model to the left.
There are also joystick type transmitters. They are held with two hands and controlled using the right and left sticks. But this type of equipment is rare for high-quality cars. They can be found on most aircraft, and in rare cases - on toy radio-controlled cars.
Therefore, we have already figured out one important point about how to select a remote control for a radio-controlled car - we need a pistol-type remote control. Go ahead.
What characteristics should you pay attention to when choosing
Despite the fact that in any model store you can choose both simple, budget equipment and very multifunctional, expensive, professional equipment, the general parameters that are worth paying attention to will be:
- Frequency
- Hardware channels
- Range
Communication between the remote control for a radio-controlled car and the receiver is ensured using radio waves, and the main indicator in this case is the carrier frequency. Recently, modelers have been actively switching to transmitters with a frequency of 2.4 GHz, since it is practically not vulnerable to interference. This allows you to assemble a large number of radio-controlled cars in one place and run them simultaneously, while equipment with a frequency of 27 MHz or 40 MHz reacts negatively to the presence of foreign devices. Radio signals can overlap and interrupt each other, causing control over the model to be lost.
If you decide to buy a remote control for a radio-controlled car, you will probably pay attention to the indication in the description of the number of channels (2-channel, 3CH, etc.). We are talking about control channels, each of which is responsible for one of the actions of the model. As a rule, for a car to move, two channels are enough - engine operation (gas/brake) and direction of movement (turns). You can find simple toy cars in which the third channel is responsible for remotely turning on the headlights.
In sophisticated professional models, the third channel is for controlling mixture formation in the internal combustion engine or for locking the differential.
This question is of interest to many beginners. Sufficient range so that you can feel comfortable in a spacious room or on rough terrain - 100-150 meters, then the machine is lost from sight. The power of modern transmitters is enough to transmit commands over a distance of 200-300 meters.
An example of a high-quality, budget remote control for a radio-controlled car is. This is a 3-channel system operating in the 2.4 GHz band. The third channel gives more opportunities for the modeler’s creativity and expands the functionality of the car, for example, it allows you to control the headlights or turn signals. In the transmitter memory you can program and save settings for 10 different car models!
Revolutionaries in the world of radio control - the best remote controls for your car
The use of telemetry systems has become a real revolution in the world of radio-controlled cars! The modeler no longer needs to be at a loss about what speed the model is developing, what voltage the on-board battery has, how much fuel is left in the tank, what temperature the engine has warmed up to, how many revolutions it makes, etc. The main difference from conventional equipment is that the signal is transmitted in two directions: from the pilot to the model and from telemetry sensors to the remote control.
Miniature sensors allow you to monitor the condition of your car in real time. The necessary data can be displayed on the display of the remote control or on the PC monitor. Agree, it is very convenient to always be aware of the “internal” state of the car. Such a system is easy to integrate and simple to configure.
An example of an “advanced” type remote control is. The app uses DSM2 technology, which provides the most accurate and fast response. Other distinctive features include a large screen on which data on the settings and status of the model is displayed in graphical form. Spektrum DX3R is considered the fastest among analogues and is guaranteed to lead you to victory!
In the Planeta Hobby online store you can easily select equipment for controlling models, you can buy a remote control for a radio-controlled car and other necessary electronics:, etc. Make your choice wisely! If you can’t decide on your own, contact us, we’ll be happy to help!
Tuning the model is needed not only to show the fastest laps. For most people this is absolutely unnecessary. But, even for driving around a summer cottage, it would be nice to have good and distinct handling so that the model obeys you perfectly on the highway. This article is the basis for understanding the physics of the machine. It is not aimed at professional riders, but at those who have just started riding.
The purpose of the article is not to confuse you in a huge mass of settings, but to tell you a little about what can be changed and how these changes will affect the behavior of the machine.
The order of changes can be very diverse, translations of books on model settings have appeared on the Internet, so some may throw a stone at me that, they say, I don’t know the degree of influence of each setting on the behavior of the model. I will say right away that the degree of influence of this or that change changes when the tires (off-road, road tires, micropores) and coating change. Therefore, since the article is aimed at a very wide range of models, it would not be correct to state the order of changes and the extent of their impact. Although I will, of course, talk about this below.
How to set up the car
First of all, you must adhere to the following rules: make only one change per race in order to feel how the change made affected the behavior of the car; but the most important thing is to stop in time. It is not necessary to stop when you show the best lap time. The main thing is that you can confidently drive the car and cope with it in any mode. For beginners, these two things very often do not coincide. Therefore, to begin with, the guideline is this: the car should allow you to carry out the race easily and without errors, and this is already 90 percent of the victory.
What should I change?
Camber Angle
Wheel camber angle is one of the main tuning elements. As can be seen from the figure, this is the angle between the plane of rotation of the wheel and the vertical axis. For each car (suspension geometry) there is an optimal angle that gives the greatest traction between the wheel and the road. The angles for the front and rear suspension are different. The optimal camber changes with changing surfaces - for asphalt, one angle gives maximum grip, for carpet another, and so on. Therefore, for each coating this angle needs to be looked for. The wheel tilt angle should be changed from 0 to -3 degrees. There is no point anymore, because... It is in this range that its optimal value lies.
The main idea of changing the angle of inclination is this:
- “larger” angle means better grip (in the case of wheels “stalling” towards the center of the model, this angle is considered negative, so talking about increasing the angle is not entirely correct, but we will consider it positive and talk about its increase)
- smaller angle means less wheel grip
Wheel alignment
The toe-in of the rear wheels increases the stability of the car on a straight line and in turns, that is, it seems to increase the grip of the rear wheels on the surface, but reduces the maximum speed. As a rule, toe-in is changed either by installing different hubs or lower control arm supports. In principle, both have the same effect. If better steering is required, then the toe angle should be reduced, and if, on the contrary, understeer is needed, then the angle should be increased.
The toe-in of the front wheels varies from +1 to -1 degrees (from wheel divergence to toe-in, respectively). Setting these angles affects the moment you enter the turn. This is the main task of changing toe. The toe angle also has a slight influence on the behavior of the car inside the turn.
- larger angle - the model is better controlled and turns faster, that is, it acquires the features of oversteer
- smaller angle - the model takes on the characteristics of understeer, so it enters the turn more smoothly and turns worse inside the turn
Suspension stiffness
This is the easiest way to change the steering and stability of the model, although not the most effective. The stiffness of the spring (as well as, in part, the viscosity of the oil) affects the “adhesion” of the wheels to the road. Of course, it is not correct to talk about changes in wheel grip with the road when the suspension stiffness changes, since it is not the grip as such that changes. For easier understanding, the term “clutch change” is easier to understand. In the next article I will try to explain and prove that wheel grip remains constant, but completely different things change. So, the grip of the wheels on the road decreases with increasing suspension stiffness and oil viscosity, but the rigidity cannot be increased excessively, otherwise the car will become nervous due to the constant separation of the wheels from the road. Installing soft springs and oil increases grip. Again, no need to run to the store in search of the softest springs and oil. If there is too much grip, the car starts to slow down too much when cornering. As the racers say, it starts to “get stuck” in a turn. This is a very bad effect, since it is not always easy to feel it, the car can have excellent balance and handle well, but the lap time deteriorates very much. Therefore, for each coating you will have to look for a balance between two extremes. As for oil, on bumpy tracks (especially on winter tracks built on a plank floor) it is necessary to fill with very soft oil 20 - 30WT. Otherwise, the wheels will begin to lift off the road and the grip on the surface will decrease. On flat tracks with good grip, 40-50WT is quite suitable.
When adjusting the suspension stiffness, the rule is as follows:
- The stiffer the front suspension, the worse the car turns, and it becomes more resistant to drift of the rear axle.
- The softer the rear suspension, the worse the model turns, but becomes less prone to drifting the rear axle.
- the softer the front suspension, the more pronounced the oversteer, and the higher the tendency for the rear axle to drift
- The stiffer the rear suspension, the more the handling takes on oversteer characteristics.
Shock absorber angle
The angle of the shock absorbers essentially affects the stiffness of the suspension. The closer the lower shock absorber mount is to the wheel (we move it to hole 4), the higher the stiffness of the suspension and the correspondingly worse the grip of the wheels on the road. Moreover, if the upper mount is also moved closer to the wheel (hole 1), the suspension becomes even stiffer. If you move the mounting point to hole 6, the suspension will become softer, as in the case of moving the upper mounting point to hole 3. The effect of changing the position of the shock absorber mounting points is the same as changing the stiffness of the springs.
Kingpin angle
The kingpin angle is the angle of inclination of the axis of rotation (1) of the steering knuckle relative to the vertical axis. Popularly, a king pin refers to the axle (or hub) in which the steering knuckle is installed.
The main influence of the kingpin angle is on the moment of entering the turn, in addition, it contributes to the change in handling inside the turn. As a rule, the angle of inclination of the kingpin is changed either by moving the upper link along the longitudinal axis of the chassis, or by replacing the kingpin itself. Increasing the angle of the kingpin improves the entry into the turn - the car enters it more sharply, but there is a tendency for the rear axle to skid. Some people believe that with a large angle of inclination of the kingpin, the exit from the turn on the open throttle worsens - the model floats to the outside of the turn. But from my experience driving models and engineering experience, I can say with confidence that it does not affect the exit from a turn in any way. Reducing the angle of inclination worsens the entry into the turn - the model becomes less sharp, but it is easier to control - the car becomes more stable.
Tilt angle of the lower arm swing axis
It’s good that one of the engineers thought of changing such things. After all, the angle of inclination of the levers (front and rear) affects exclusively the individual phases of cornering - separately on the entrance to the turn and separately on the exit.
Exit from a turn (on gas) is affected by the angle of the rear arms. As the angle increases, the grip of the wheels on the road “deteriorates”, while with the throttle open and the wheels turned, the car tends to move to the inner radius. That is, the tendency for the rear axle to skid increases when the throttle is open (in principle, if the wheels have poor adhesion to the road, the model can even spin out). As the angle of inclination decreases, grip during acceleration improves, so it becomes easier to accelerate, but there is no effect when the model tends to move to a smaller radius on gas; the latter, when handled skillfully, helps to take turns and exit them faster.
The angle of the front control arms affects the turn-in when releasing the gas. As the angle of inclination increases, the model enters the turn more smoothly and acquires understeer characteristics at the entrance. When the angle decreases, the effect is correspondingly opposite.
Transverse roll center position
- center of mass of the car
- upper arm
- lower arm
- roll center
- chassis
- wheel
The position of the roll center changes the grip of the wheels during a turn. The roll center is the point about which the chassis rotates under the influence of inertial forces. The higher the roll center is (the closer it is to the center of mass), the less roll there will be and the higher the grip of the wheels on the road. That is:
- Raising the roll center at the rear reduces steering performance but increases stability.
- Lowering the roll center improves cornering but reduces stability.
- Raising the roll center at the front improves steering but reduces stability.
- Lowering the roll center at the front reduces understeer and increases stability.
Finding the roll center is very simple: mentally extend the upper and lower arms and determine the point of intersection of the imaginary lines. From this point we draw a straight line to the center of the contact patch of the wheel with the road. The point of intersection of this straight line and the center of the chassis is the roll center.
If the attachment point of the upper arm to the chassis (5) is lowered, the roll center will rise. If you raise the attachment point of the upper control arm to the hub, the roll center will also rise.
Clearance
Ground clearance, or ground clearance, affects three things - rollover stability, wheel traction, and handling.
With the first point, everything is simple, the higher the ground clearance, the higher the tendency of the model to tip over (the position of the center of gravity increases).
In the second case, increasing the ground clearance increases the roll when turning, which in turn worsens the grip of the wheels on the road.
With the difference in ground clearance front and rear, the following happens. If the front clearance is lower than the rear, then there will be less roll in the front, and, accordingly, the traction of the front wheels with the road will be better - the car will oversteer. If the rear clearance is lower than the front, the model will understeer.
Here's a quick look at what can be changed and how it will affect the behavior of the model. To begin with, these settings are quite enough to learn how to drive well without making mistakes on the track.
Sequence of changes
The sequence can be varied. Many top racers change only what will eliminate shortcomings in the car’s behavior on a given track. They always know what exactly they need to change. Therefore, you must strive to clearly understand how the car behaves in turns, and what behavior does not suit you specifically.
As a rule, the machine comes with factory settings. Testers who select these settings try to make them as universal as possible for all tracks, so that inexperienced modelers do not get into the weeds.
Before starting training, you need to check the following points:
- set ground clearance
- Install the same springs and fill with the same oil.
Then you can start customizing the model.
You can start customizing the model small. For example, from the angles of inclination of the wheels. Moreover, it is best to make a very large difference - 1.5...2 degrees.
If there are small flaws in the behavior of the car, then they can be eliminated by limiting the corners (let me remind you, you should be able to handle the car easily, that is, there should be a slight understeer). If the shortcomings are significant (the model unfolds), then the next stage is changing the angle of inclination of the kingpin and the positions of the roll centers. As a rule, this is enough to achieve an acceptable picture of the car’s handling, and the nuances are introduced by other settings.
See you on the track!
How to set up a radio-controlled car?
Tuning the model is needed not only to show the fastest laps. For most people this is absolutely unnecessary. But, even for driving around a summer cottage, it would be nice to have good and distinct handling so that the model obeys you perfectly on the highway. This article is the basis for understanding the physics of the machine. It is not aimed at professional riders, but at those who have just started riding.
The purpose of the article is not to confuse you in a huge mass of settings, but to tell you a little about what can be changed and how these changes will affect the behavior of the machine.
The order of changes can be very diverse, translations of books on model settings have appeared on the Internet, so some may throw a stone at me that, they say, I don’t know the degree of influence of each setting on the behavior of the model. I will say right away that the degree of influence of this or that change changes when the tires (off-road, road tires, micropores) and coating change. Therefore, since the article is aimed at a very wide range of models, it would not be correct to state the order of changes and the extent of their impact. Although I will, of course, talk about this below.
How to set up the car
First of all, you must adhere to the following rules: make only one change per race in order to feel how the change made affected the behavior of the car; but the most important thing is to stop at the right time. It is not necessary to stop when you show the best lap time. The main thing is that you can confidently drive the car and cope with it in any mode. For beginners, these two things very often do not coincide. Therefore, to begin with, the guideline is this: the car should allow you to carry out the race easily and without errors, and this is already 90 percent of the victory.
What should I change?
Camber Angle
Wheel camber angle is one of the main tuning elements. As can be seen from the figure, this is the angle between the plane of rotation of the wheel and the vertical axis. For each car (suspension geometry) there is an optimal angle that gives the greatest traction between the wheel and the road. The angles for the front and rear suspension are different. The optimal camber changes as the surface changes - for asphalt, one angle gives maximum grip, for carpet another, and so on. Therefore, for each coating this angle needs to be looked for. The wheel tilt angle should be changed from 0 to -3 degrees. There is no point anymore, because... It is in this range that its optimal value lies.
The main idea of changing the angle of inclination is this:
a “larger” angle means better grip (in the case of wheels “stalling” towards the center of the model, this angle is considered negative, so talking about increasing the angle is not entirely correct, but we will consider it positive and talk about its increase)
smaller angle - less traction of the wheels with the road
Wheel alignment
The toe-in of the rear wheels increases the stability of the car on a straight line and in turns, that is, it seems to increase the grip of the rear wheels on the surface, but reduces the maximum speed. As a rule, toe-in is changed either by installing different hubs or lower control arm supports. In principle, both have the same effect. If better steering is required, then the toe angle should be reduced, and if, on the contrary, understeer is needed, then the angle should be increased.
The toe-in of the front wheels varies from +1 to -1 degrees (from wheel divergence to toe-in, respectively). Setting these angles affects the moment you enter the turn. This is the main task of changing toe. The toe angle also has a slight influence on the behavior of the car inside the turn.
larger angle - the model is better controlled and turns faster, that is, it acquires the features of oversteer
smaller angle - the model takes on the characteristics of understeer, so it enters the turn more smoothly and turns worse inside the turn 
How to set up a radio-controlled car? Tuning the model is needed not only to show the fastest laps. For most people this is absolutely unnecessary. But, even for driving around a summer cottage, it would be nice to have good and distinct handling so that the model obeys you perfectly on the highway. This article is the basis for understanding the physics of the machine. It is not aimed at professional riders, but at those who have just started riding.
