TheJoker
Active Member
In here you will find a beginnersguide of the different parts of an rc car.
Content:
1 Brushed vs brushless motors
2 What is an ESC?
3 What is a servo?
4 The differentials and how to use them
5 Suspension
6 Tires
7 Transmitters and Receivers
8 Batteries
more to come.....
1 Brushed vs Brushless motors
One of the choices you have to make when you buy a new Rc car, is whether you want a car with a bushed motor or a brushless motor.
Only the easy to understand technique is explained here (we don't cover the whole in-dept of these motors)
Brushed motors use carbon brushes to glide the power. These brushes are subject to wear, and also at high torque, they create more resistance, wich leads to less power-outlet.
brushed motors are most of the time used in lower-end cars and in mini-cars.
They are cheap to produce and easy to connect to an ESC because they only have 2 wires. (Thats also an easy way to reckognize them.
Brushless motors don't use carbon brushes (as the name implies). This will result in less friction, thus also less motor-wear.
Their coils are activated by the ESC (electronic speed controller, wich will be covered later) one phase after the other as cued by the signals from the sensors of the rotorposition
More important to know when you are going to make the brushed or brushless-choice is their specific advantages and disadvantages.
Below are a few of them summed up:
Brushed motors:
- they need maintenance, as the brushes are subject to wear.
- the higher the speed, the higher the friction (so less available torque and speed, thus slower then brushless)
- their heat-flow is not as good as brushless motors because of the way the motor is build.
BUT.....
- they can outlast life expectations due to repeated maintenance
- Cheap to build
- Easy to control, they only have 2 wires
Brushless motors:
- High construction cost, so a car with t his kind of motor will be more expensive
- An ESC is required to control the motor, wich is also expensive.
BUT....
- they require less maintenance due to the lack of brushes.
- Highly efficient also due to the lack of brushes (no friction)
( in depth :
1- not having that brush to comm electrical connection. The friction resistance may be small, but the electrical resistance is big, due to the arc gap. Properly breaking in the motor is critical to minimize this gap, but it will always exits.
The #2 big change is the Neodymium magnets in brushless motors. Stronger magnets = stronger motor. For whatever reason, brushed motors never used Neo-magnets.
( thank you Jerry-rigged for the in-depth input)
- Higher power output wich means the car can ride at higher speeds
Offcourse there are more advantages and disadvantages you can think off, but the above are sufficient to make a good choice wich one to choose.
Always ask yourself the question "Whatt do i want with the car now and in the future, and what is my budget"
Compromises are needed!
2 What is an ESC?
An ESC (Electronic Speed Controller) serves to activate and control the motor.
For a brushed and brushless motor, different kind of esc's are used.
The values of the Esc should be in range with the values of the motor.
By brushed esc's the term turns is used to implicate the amount of roundings at the coil of the motor.
The lower the amount, the more power the motor can deliver and the more energy it uses.
On an esc there is a value which implicates the minimum amount of turns the motor needs to have.
If you connect a motor with less turns then is advised by the values on the esc, then the esc might burn out. (Fry)
In the RC world, the term "turns" is a standard term, so it is very easy to find an appropriate esc and an appropriate motor.
On a brushless esc, most of the time, you wont find "turns" on it, but simply the maximum amount of power the esc can deliver.
On most engines the maximum powerusage is given, so you can search for the correct set of an motor and an appropriate esc.
A brushless esc can be sensored or sensorless...
An sensored esc has a sensor and a sensorless esc doesn't...(duuhhh)
A sensored esc is more expensive then a sensorless esc but also has a big advantage over the sensorless esc, it functionates smoother.
Because a brushless motor operates through three lead wires instead of two power wires by a brushed esc, there must be a proper timing between the current-pulses delivered by the ESC.
On a high Torque you wont notice any difference, but with low Torque, like which is the case by accelerating and taking corners, having a sensor gives a big advantage.
Sensorless esc's are known to have the cogging effect on low torque, wich means they can falter,(stutter) until they reach the higher speeds again.
This is normal when you have a sensorless esc with an also sensorless motor, but it means also that your car has a slower acceleration and isnt as fast in cornering.
Offcourse a sensored esc and motor combo is way more expensive then a sensorless combo, so again....sacrifices need to be made, all depending on your wallet
3 What is a servo?
A servo is in fact a motor that knows its own driveshaft-position towards an earlier given referencepoint.
With the right steering-elektronics, parts in a machine or for example an rc car, can be powered very accurate, within 0,00001mm or so.
The receiver sends current as well as a signal trough the cable to the servo. It will be put trough the cable only in pulses of a few microseconds each.
For example, a 1ms pulse gives the servo the task to completely turn to a specific side, and a 2ms pulse gives it the task to turn to the opposite side.
To vary with the length of the pulse, every position between the 2 sides can be adressed.
A steeringtask only takes a very short time (max 3ms), therefore it is possible to send multiple steeringtasks within just a fraction of a second.
The only limitation there is, is the time it takes to send the signal from the sender to the receiver, and the time it takes the servo to reach the specific position.
Every servo needs to know what its starting position should be. (the 0 position)
Therefore each servo has a turn potentiometer wich lets the servo know wich position it is currently in.
The potentiometer is also the reason why a servo cant turn 360 degrees.
The potentiometer and the send-equipment determine the maximum turn-angle of the servo.
Because the potentiometer turns when the servo turns, the electronics on the servo mainboard can measure the resistance value on both sides. If these values are excactly the same, the servo knows that that specific point is its 0 point.
The servo itself has multiple gears wich are placed in the servos gearbox, wich is driven by a little motor.
The gears are getting smaller and smaller (starts with a big gear and goes smaller and smaller), thats why the power of the motor increases, wich accounts the strenght of the servo.
The more resistance a car catches, the stronger the servo needs to be to turn the wheels for example.
The gears can be made from plastic (in cheap servos) all the way up to titanium (expensive servos.
All the above counts for an analog servo.
There are also digital servos who have an own microprocessor who knows excactly what needs to
done with a specific signal.
Their main advantage is that this way is more accurate and the servo has a faster responsetime.
A digital servo is normally more expensive then an analog servo.
There are a lot of different kinds of servos. To be sure that you pick the right one for your needs, always do your homework. Check the size of the servo, its weight, its strength and offcourse the pricetag.
4 The differentials and how to use them
A differential actually has one important function. It sends all the rotations trough to the wheel wich has the least resistance.
The front differential (diff) distributes the twisting power from the drive shaft to the front wheels.
The rear differential distributes the twisting power from the drive shaft to the rear wheels.
The middle diff in a buggy or truggy actually has the task to give the car a better handling.
They are filled with grease, but preferebly diffoil.
I will try to explain what the oils do in the diffs.
If you change the oil in a differential you can greatly enhance the performance and handling of your car! (if you put the wrong oil in the diffs for your needs, you can make it worse too.)
Front differential: If you use thicker oil in the front differential, the car turns itself easier when you come out of a corner, and it accelerates faster.
But it will turn itself harder and more difficult when you want to turn in on a corner.
The car will feel more stable and controllable on bumpy courses with some jumps in it.
When you want the opposite of this, try a thinner oil.
Middle differential With thick oil in the middle diff the car will accalerate faster and also makes wheelies faster. Its also possible the rear wheels will go slide wich gives you a bit more steering control. (This sliding part needs good drivingskills)
The thicker oil will make riding on flat surfaces like onroad and little bumpy roads a lot heavier. Use thinner oil when you want the opposite effect.
Rear differential Most of the times the rear diff will have the most different setups by different people.
This is because the rear diff has lots to do with the traction of the rear wheels of the car, so the difference in drivingstyles will decide wich oil-thickness will be used here.
A thick oil in the reardiff makes the car more controllable with "throttle-steering"
You can start taking a corner really fast because the rearside will be very stable and will have a very controllable rear-tires-slide. Drifting is also easier done with thicker rear diffoil.
On a flat service or a little bumpy surface, the car will be harder to control.
In most cases, the reardiff will be filled with the thinnest oil if you compare it with the front and middle diff, who have thicker oil in most cases.
So if you want to find the correct setup for your car and or condition, you wil need to experiment with the oil-thicknesses in the different diffs. Only then you will know what diffsetup and oil will suits you best!
5 Suspension
The shocks on a rc car absorb the up-and-down impact on a rc car.
A shock is usually filled with oil and inside it is also a piston, wich helps dampen the rebound and helps to keep the car on the track.
Inside this with oil filled shock, there is a piston wich goes up and down in the shock and thus "slams" trough the oil, wich gives the dampen effect.
On the outside. a shock has a spring around its body. The springs make sure the car isnt slamming on the ground by impact.
The springs wich are mostly used are the so called coil springs.
Springs work in 2 ways: From left to right and from front to rear.
For example: a car with soft springs will experience a lot of body roll in fast turns, but it will also dive very hard under heavy breaking and squat a lot while accelerating. This is because the springs have to absorb the torque that is generated, and soft springs need to be compressed over a larger distance to be able to absorb a certain force.
The stiffness of a spring is very important, it effects almost everything while you drive, like roll-stiffness and the way the car reacts after a bumpy impact.
You can also adjust ride-hight with the springs wich also effects the handling of the car.
Shocks can be mounted to an rc cars in different ways. you can also adjust camber etc...but since this is a beginnerguide we wont cover this part over here.
The thickness of the oil also has an important role of how the shocks react at impact at certain tracks.
Onroad you need much handling and don't need the car being able to absorb heavy jump impact.
How thicker the oil. how slower the piston goes trough the oil, wich means the longer it takes for the shock to go in-and-back out again.
Remember to also adjust the oil to the proper conditions that you need.
There are also different kinds of shocks like piggyback shocks and big bores but this info is not covered here.
6 Tires
Actually the most important part on a rc car wixh influences car handling, are by far the tires.
The tires are the only part of the car who are in direct contact with the ground (surface). So tires should be always perfectly in shape and adjusted to the typ of tire wich is needed in a specific circumstance.
To keep it simple, make sure you always choose the right tire and make sure they are in perfect condition.
The tires influence the car handling by the traction they got.
Offcourse riding offroad on a soiltrack with onroad tires will result in very bad grip and thus very bad handling.
Offroad tires have different profiles, suited for ex. snow or soil.
Here are the most used tire-profiles and what they are suited for:
Slicks: Can be made of rubber or foam, high traction on hard surfaces, gives even traction in all directions, virtually no traction off-road. For wet conditions there are also V-grooved tires.
Grooved: Medium-low wear on hard surfaces, high side-to-side traction, low traction on acceleration on sand.
Pins: Extremely high wear on hard surfaces, low traction on hard surfaces, gives even traction in all directions, traction greatly reduced on sand.
X Pin: Medium-high wear on hard surfaces, relatively low traction on hard surfaces, gives even traction in all directions, traction less effected by sand.
Ribbed: Only used on the front wheels of 2-wheel-drive vehicles, good for most off-road conditions, excellent side-to-side traction.
Paddle: High wear on hard surfaces (especially during acceleration), extremely good traction on sand, can drastically reduce steering on 2WD vehicles
Content:
1 Brushed vs brushless motors
2 What is an ESC?
3 What is a servo?
4 The differentials and how to use them
5 Suspension
6 Tires
7 Transmitters and Receivers
8 Batteries
more to come.....
1 Brushed vs Brushless motors
One of the choices you have to make when you buy a new Rc car, is whether you want a car with a bushed motor or a brushless motor.
Only the easy to understand technique is explained here (we don't cover the whole in-dept of these motors)
Brushed motors use carbon brushes to glide the power. These brushes are subject to wear, and also at high torque, they create more resistance, wich leads to less power-outlet.
brushed motors are most of the time used in lower-end cars and in mini-cars.
They are cheap to produce and easy to connect to an ESC because they only have 2 wires. (Thats also an easy way to reckognize them.
Brushless motors don't use carbon brushes (as the name implies). This will result in less friction, thus also less motor-wear.
Their coils are activated by the ESC (electronic speed controller, wich will be covered later) one phase after the other as cued by the signals from the sensors of the rotorposition
More important to know when you are going to make the brushed or brushless-choice is their specific advantages and disadvantages.
Below are a few of them summed up:
Brushed motors:
- they need maintenance, as the brushes are subject to wear.
- the higher the speed, the higher the friction (so less available torque and speed, thus slower then brushless)
- their heat-flow is not as good as brushless motors because of the way the motor is build.
BUT.....
- they can outlast life expectations due to repeated maintenance
- Cheap to build
- Easy to control, they only have 2 wires
Brushless motors:
- High construction cost, so a car with t his kind of motor will be more expensive
- An ESC is required to control the motor, wich is also expensive.
BUT....
- they require less maintenance due to the lack of brushes.
- Highly efficient also due to the lack of brushes (no friction)
( in depth :
1- not having that brush to comm electrical connection. The friction resistance may be small, but the electrical resistance is big, due to the arc gap. Properly breaking in the motor is critical to minimize this gap, but it will always exits.
The #2 big change is the Neodymium magnets in brushless motors. Stronger magnets = stronger motor. For whatever reason, brushed motors never used Neo-magnets.
( thank you Jerry-rigged for the in-depth input)
- Higher power output wich means the car can ride at higher speeds
Offcourse there are more advantages and disadvantages you can think off, but the above are sufficient to make a good choice wich one to choose.
Always ask yourself the question "Whatt do i want with the car now and in the future, and what is my budget"
Compromises are needed!
2 What is an ESC?
An ESC (Electronic Speed Controller) serves to activate and control the motor.
For a brushed and brushless motor, different kind of esc's are used.
The values of the Esc should be in range with the values of the motor.
By brushed esc's the term turns is used to implicate the amount of roundings at the coil of the motor.
The lower the amount, the more power the motor can deliver and the more energy it uses.
On an esc there is a value which implicates the minimum amount of turns the motor needs to have.
If you connect a motor with less turns then is advised by the values on the esc, then the esc might burn out. (Fry)
In the RC world, the term "turns" is a standard term, so it is very easy to find an appropriate esc and an appropriate motor.
On a brushless esc, most of the time, you wont find "turns" on it, but simply the maximum amount of power the esc can deliver.
On most engines the maximum powerusage is given, so you can search for the correct set of an motor and an appropriate esc.
A brushless esc can be sensored or sensorless...
An sensored esc has a sensor and a sensorless esc doesn't...(duuhhh)
A sensored esc is more expensive then a sensorless esc but also has a big advantage over the sensorless esc, it functionates smoother.
Because a brushless motor operates through three lead wires instead of two power wires by a brushed esc, there must be a proper timing between the current-pulses delivered by the ESC.
On a high Torque you wont notice any difference, but with low Torque, like which is the case by accelerating and taking corners, having a sensor gives a big advantage.
Sensorless esc's are known to have the cogging effect on low torque, wich means they can falter,(stutter) until they reach the higher speeds again.
This is normal when you have a sensorless esc with an also sensorless motor, but it means also that your car has a slower acceleration and isnt as fast in cornering.
Offcourse a sensored esc and motor combo is way more expensive then a sensorless combo, so again....sacrifices need to be made, all depending on your wallet
3 What is a servo?
A servo is in fact a motor that knows its own driveshaft-position towards an earlier given referencepoint.
With the right steering-elektronics, parts in a machine or for example an rc car, can be powered very accurate, within 0,00001mm or so.
The receiver sends current as well as a signal trough the cable to the servo. It will be put trough the cable only in pulses of a few microseconds each.
For example, a 1ms pulse gives the servo the task to completely turn to a specific side, and a 2ms pulse gives it the task to turn to the opposite side.
To vary with the length of the pulse, every position between the 2 sides can be adressed.
A steeringtask only takes a very short time (max 3ms), therefore it is possible to send multiple steeringtasks within just a fraction of a second.
The only limitation there is, is the time it takes to send the signal from the sender to the receiver, and the time it takes the servo to reach the specific position.
Every servo needs to know what its starting position should be. (the 0 position)
Therefore each servo has a turn potentiometer wich lets the servo know wich position it is currently in.
The potentiometer is also the reason why a servo cant turn 360 degrees.
The potentiometer and the send-equipment determine the maximum turn-angle of the servo.
Because the potentiometer turns when the servo turns, the electronics on the servo mainboard can measure the resistance value on both sides. If these values are excactly the same, the servo knows that that specific point is its 0 point.
The servo itself has multiple gears wich are placed in the servos gearbox, wich is driven by a little motor.
The gears are getting smaller and smaller (starts with a big gear and goes smaller and smaller), thats why the power of the motor increases, wich accounts the strenght of the servo.
The more resistance a car catches, the stronger the servo needs to be to turn the wheels for example.
The gears can be made from plastic (in cheap servos) all the way up to titanium (expensive servos.
All the above counts for an analog servo.
There are also digital servos who have an own microprocessor who knows excactly what needs to
done with a specific signal.
Their main advantage is that this way is more accurate and the servo has a faster responsetime.
A digital servo is normally more expensive then an analog servo.
There are a lot of different kinds of servos. To be sure that you pick the right one for your needs, always do your homework. Check the size of the servo, its weight, its strength and offcourse the pricetag.
4 The differentials and how to use them
A differential actually has one important function. It sends all the rotations trough to the wheel wich has the least resistance.
The front differential (diff) distributes the twisting power from the drive shaft to the front wheels.
The rear differential distributes the twisting power from the drive shaft to the rear wheels.
The middle diff in a buggy or truggy actually has the task to give the car a better handling.
They are filled with grease, but preferebly diffoil.
I will try to explain what the oils do in the diffs.
If you change the oil in a differential you can greatly enhance the performance and handling of your car! (if you put the wrong oil in the diffs for your needs, you can make it worse too.)
Front differential: If you use thicker oil in the front differential, the car turns itself easier when you come out of a corner, and it accelerates faster.
But it will turn itself harder and more difficult when you want to turn in on a corner.
The car will feel more stable and controllable on bumpy courses with some jumps in it.
When you want the opposite of this, try a thinner oil.
Middle differential With thick oil in the middle diff the car will accalerate faster and also makes wheelies faster. Its also possible the rear wheels will go slide wich gives you a bit more steering control. (This sliding part needs good drivingskills)
The thicker oil will make riding on flat surfaces like onroad and little bumpy roads a lot heavier. Use thinner oil when you want the opposite effect.
Rear differential Most of the times the rear diff will have the most different setups by different people.
This is because the rear diff has lots to do with the traction of the rear wheels of the car, so the difference in drivingstyles will decide wich oil-thickness will be used here.
A thick oil in the reardiff makes the car more controllable with "throttle-steering"
You can start taking a corner really fast because the rearside will be very stable and will have a very controllable rear-tires-slide. Drifting is also easier done with thicker rear diffoil.
On a flat service or a little bumpy surface, the car will be harder to control.
In most cases, the reardiff will be filled with the thinnest oil if you compare it with the front and middle diff, who have thicker oil in most cases.
So if you want to find the correct setup for your car and or condition, you wil need to experiment with the oil-thicknesses in the different diffs. Only then you will know what diffsetup and oil will suits you best!
5 Suspension
The shocks on a rc car absorb the up-and-down impact on a rc car.
A shock is usually filled with oil and inside it is also a piston, wich helps dampen the rebound and helps to keep the car on the track.
Inside this with oil filled shock, there is a piston wich goes up and down in the shock and thus "slams" trough the oil, wich gives the dampen effect.
On the outside. a shock has a spring around its body. The springs make sure the car isnt slamming on the ground by impact.
The springs wich are mostly used are the so called coil springs.
Springs work in 2 ways: From left to right and from front to rear.
For example: a car with soft springs will experience a lot of body roll in fast turns, but it will also dive very hard under heavy breaking and squat a lot while accelerating. This is because the springs have to absorb the torque that is generated, and soft springs need to be compressed over a larger distance to be able to absorb a certain force.
The stiffness of a spring is very important, it effects almost everything while you drive, like roll-stiffness and the way the car reacts after a bumpy impact.
You can also adjust ride-hight with the springs wich also effects the handling of the car.
Shocks can be mounted to an rc cars in different ways. you can also adjust camber etc...but since this is a beginnerguide we wont cover this part over here.
The thickness of the oil also has an important role of how the shocks react at impact at certain tracks.
Onroad you need much handling and don't need the car being able to absorb heavy jump impact.
How thicker the oil. how slower the piston goes trough the oil, wich means the longer it takes for the shock to go in-and-back out again.
Remember to also adjust the oil to the proper conditions that you need.
There are also different kinds of shocks like piggyback shocks and big bores but this info is not covered here.
6 Tires
Actually the most important part on a rc car wixh influences car handling, are by far the tires.
The tires are the only part of the car who are in direct contact with the ground (surface). So tires should be always perfectly in shape and adjusted to the typ of tire wich is needed in a specific circumstance.
To keep it simple, make sure you always choose the right tire and make sure they are in perfect condition.
The tires influence the car handling by the traction they got.
Offcourse riding offroad on a soiltrack with onroad tires will result in very bad grip and thus very bad handling.
Offroad tires have different profiles, suited for ex. snow or soil.
Here are the most used tire-profiles and what they are suited for:
Slicks: Can be made of rubber or foam, high traction on hard surfaces, gives even traction in all directions, virtually no traction off-road. For wet conditions there are also V-grooved tires.
Grooved: Medium-low wear on hard surfaces, high side-to-side traction, low traction on acceleration on sand.
Pins: Extremely high wear on hard surfaces, low traction on hard surfaces, gives even traction in all directions, traction greatly reduced on sand.
X Pin: Medium-high wear on hard surfaces, relatively low traction on hard surfaces, gives even traction in all directions, traction less effected by sand.
Ribbed: Only used on the front wheels of 2-wheel-drive vehicles, good for most off-road conditions, excellent side-to-side traction.
Paddle: High wear on hard surfaces (especially during acceleration), extremely good traction on sand, can drastically reduce steering on 2WD vehicles
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