Beginner / Starter Info

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Arrma RC's
In here you will find a beginnersguide of the different parts of an rc car.


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.
- 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.
- 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! :D

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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- Highly efficient also due to the lack of brushes (no friction)

Over all a good post, but I am not sure this is correct. Sure the brushes all friction, but that is only a small difference in efficiency. The bigger gains are from

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.

But this is probably more info than a noob is looking for... :).

Brushless = more power, more efficency, longer life.
Brushed = cheaper, better low speed control (compared to sensorless brushless motors)

7 Transmitters and Receivers


The transmitter, also called TX, is the radio u use to control your Rc.
The receiver is a little chip wich is inside the little box in your rc car with the antenna sticking out. It receivers the signals from the transmitter (tx) and translates them into a signal wich the ESC and servo can understand and thus know what they should do.
There are a few different types of Tx/Rx systems. The TX and RX must be of the same type to work correctly together.
First, we have AM and FM. Both of them are made to work on one of several frequencies, and each of those frequencies are broken down into a handful of channels.
With these systems, never use the same frequenties (channel) as somebody else close by, because that would cause some unwanted interference. (could be funny to see lol)
The latest system is Digital Spread Spectrum (DSS). This is by far the best system available.
With this system, your Tx and Rx work together on a 2,4Ghz band, wich means that your Tx and RX should be bound together to succesfully communicate with eachother. When bound, they will work together without interfere, or being interfered by other people's systems.
Also DSS systems have a very long range, wich means you can let your rc ride far away from you and be sure to not loose control of it because of its distance.
Every Tx is rated based on the number of channels (control channels, not to be confused with the frequency channels) it supports. Most cars only need two - one for the throttle and one for steering.

8 Batteries

For Rc Cars, the most used battery-types are nickle metal hydride (NiMH) and lithium polymer (LiPo).

Offcourse there are some other types of batteries but since these 2 are by far the most used, we only talk about them.


The most important key ratings of a battery you should be aware of are Voltage (V) and milliamp-hours (mAh).

Voltage can be thought of as "electrical pressure". The higher the voltage, the stronger the battery is. The mAh rating tells you the capacity of the battery. The higher the rating, the longer the battery can run between recharges, wich means the longer you can run your car before the battery should be recharged.

NiMH batteries consists of 6 or more cells. Each cell provides 1.2V, so a 6 cell pack would be rated for 7.2V. NiMH batteries are heavier and cannot provide as much current as LiPo's, but they are cheaper and less prone to damage and risks.

Lipo batteries excist in many different types.

The first thing i want to point out is that no mather wich brand of lipo you choose, cheap or expensive, they are all made in China!

There are lipo's wich have 2 cells (2s), 3 cells (3s), and so on...

Now, for example an 2s lipo means the battery has 2 cells of 3.7V each. (a lipo is build off one or more cells from 3.7V each)
The “s” stands for “series”.
So simply said, a 2s lipo is build out off 2 cells connected in series, from 3.7V each.

Besides Voltage (V) and MAH, lipos have another very important rating, the C rating.
The C rating tells you how much current (amperage) the battery can supply.
Simply said, a high performance motor (mostly brushless motors) require a much higher C rating then low performance motors (mostly brushed motors)

So instead of Nimh, a Lipo is lighter in weight and also can provide much more power, wich means the car is going to be faster and more explosive (sometimes literally)
Lipo's are also more expensive and should be threaten with a lot of care.
For charging a lipo, you need a special Lipo-charger.
Lipo batteries are very sensitive...All their cells should be charged at the same speed and level.
All LiPo batteries have a 2nd, smaller connector called a "balancing connector" so that the charger can monitor and charge the cells individually. If you discharge the batteries too far (below 3V per cell), they will be damaged and cease to function properly. If you overcharge them (above 4.2V per cell, although some can get a bit higher) , short them out, or physically damage them, they can even explode!
Some manufacturers are now producing "hardcase" LiPos which, as the name implies, are enclosed in a hard plastic shell to help prevent physical damage.

Important to know also is that lipo's are sensible to heat. Offcourse they shouldnt get to hot that will swole up (altough a little swelling is normal), but when the lipo cells warm up to their ideal temperature, they give the most power. So if you noticed your car being a little bit faster after a few minutes driving, then now you know how that is possible.

Now, you know that a lipo always has one or more cells off 3.7V each.
Below are the mostly used lipos in the Rc-world:
3.7 volt battery = 1 cell x 3.7 volts (1S)
7.4 volt battery = 2 cells x 3.7 volts (2S)
11.1 volt battery = 3 cells x 3.7 volts (3S)
14.8 volt battery = 4 cells x 3.7 volts (4S)
18.5 volt battery = 5 cells x 3.7 volts (5S)
22.2 volt battery = 6 cells x 3.7 volts (6S)
29.6 volt battery = 8 cells x 3.7 volts (8S)
There are also higher volt lipos but they are not important to us Rc car drivers

In most Rc's its possible to connect 2 lipos together to get the double amount of cells.
Lets say you want to drive your car with 4s, that means you can also connect 2 lipos from 2s together.
This is indicated by a number followed by a "P". Example: 2S2P would indicate two, two celled series packs hooked up in parallel to double the capacity
In an Rc car, the mostly used lipocells are 2s,4s, 6s and 8s.

Also note that you cannot use any kind of lipo on any car!
The motor/speed controller combination will indicate what voltage is required for correct operation / RPM.

The Capacity (Mah) indicates how much power the battery pack can hold. This means how much load or drain (measured in milliamps) can be put on the battery for 1 hour at wich time the battery will be fully empty. For example an RC LiPo battery that is rated at 1000 mAh would be completely empty in one hour with a 1000 milliAmp load placed on it.
This lets you see that when you have a high performance motor \ ESC combo, you should adapt the Mah off the lipo to it, because you don't want to drive and notice that your battery needs to be recharged after just 2 minutes.
The more current the motor needs, the higher the capacity should be. Capacity equals driving-time.

The discharge rate (C) tells you how fast a battery can be discharged safely.
A battery with a discharge rating of 20C would mean you can discharge it at a rate 20 times more than the capacity of the pack, a 25C pack = 25 times more, a 50C pack = 50 times more.....etc...etc...
when a 1000mah battery has a discharge-rating of 20C, that would mean you could pull a maximum sustained load up to 20,000 milliamps or 20 amps from that battery (20 x 1000 milliamps = 20,000 milliamps or 20 amps). Timewise, this means 333 mAh of draw per minute so the 1000 mAh pack would be completely drained in about 3 minutes if it's exposed to the maximum rated 20C discharge rate the entire time.
Let me show you how that is calculated : 20,000 mA divided by 60 minutes = 333 mAh which is then divided into the 1000 mAh capacity of the pack giving us 3.00 minutes of time.

Lots of Lipo's will show you a Burst C rating also. The burst is only for a very short time, mostly a few seconds. So on a lipo you can find for example 40C / 80C burst.

Now, just look at the requirements of your motor / esc combo and make sure you get a apropriate lipo.
Simply said, the higher the C rating, the better, but keep in mind that the higher the C rating is, the heavier and more expensive the lipo becomes.
If your lipo has a C rate wich is to high for your car, that isnt a problem, but a lower c rating then what your car actually needs could result in ESC failures etc...

For safety, make sure you keep your lipos in a lipo-bag, so when something happens, the fire stays within the bag.
Also never discharge your battery underneath an average of 80%. If you go lower the cells could get permanently damaged.
Never let a lipo get to hot, because they can get permanently damaged or explode. Also the life expectations of the lipo are hanging together with usage.
Make sure your lipo has a higher C rating then needed, it will last longer then when you push the battery to its max.
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A brushed motor doesn't mind getting wet,it won't effect it's operation,whereas a brushless motor can't afford to be submerged in water.A brushed motor is only around 65% efficient,whereas a brushless motor's efficiency can be as high as 80-90% efficient.
i added a new chapter, but can a admin or mod please move this topic to the tips section please? tnx

thread updates with chaper 3 what is a servo?
[DOUBLEPOST=1462471690][/DOUBLEPOST]thread updated with chapter 4 differentials and how to use them

thread updated with chaper 5 Suspension
[DOUBLEPOST=1462557778][/DOUBLEPOST]Thread updated with chapter 6 tires.

2 questions....I cant add anymore topics becuse i cant make a post with more then 15000 characters. How are we going to resolve this? I need all the chapters standing underneath eachother. this sticky worth material maybe?
Maybe Woodie or a mod can delete the non info posts in this thread so it stays a purely info-based thread.
I already asked Jerry if im allowed to use his bearrings-post into my info-chapters with a reference to him offcourse.
Can you guys write something about lipo batteries too please
Correct settings on how to charged them safely
Example this battery what settings wiould you charged this type of battery
Batteries will be a future chapter for sure.
Will be finished at the end of the coming week at latest.

Ill just start a new post but it would be nice if they can be placed underneath
I just read the esc part
I think ill upgrade my senton with a sensored esc
What would be the best sensored out there
As the sensored motor is much faster to respond to you command no lagging
I think i like that
I would like to add that with LiPo batteries, choosing the correct 'cutoff' voltage (on your ESC) as well as choosing the "terminal voltage cutoff" (TVC) (on your charger) have a significant impact on battery longevity. This may not be "beginners guide" worthy, maybe more "intermediate topics"?

LVC / Low-Voltage: The choice of the low voltage cutoff (LVC) on your ESC is the point at which the ESC shuts itself off (or goes into a 'limp' mode, depending on your ESC) in order to protect the LiPo cells from voltage going too low (undervoltage) and becoming dangerous. Most ESCs have a default 3.2v/cell (3.2v per cell, so on a 2s pack it would be 6.4v, on a 4s pack it would be 12.8v, etc.) while some others default to 3.0v/cell. Since LiPo's can be quite dangerous at low voltage, I recommend always going with 3.2v/cell (or higher) as your LVC. This gives your pack a small cushion of voltage, so that if you run them dry and then do not charge them right away, you avoid letting your LiPos reach a dangerous low voltage.

Storage: LiPos are reported to do best when stored at a 50-80% capacity range. Keeping your LiPos always 100% at rest, or always near empty at rest (1+ days at a time) have a negative impact on your battery's full capacity and cycle longevity in addition to being potentially dangerous (if voltage is too low). Most manufacturers tend to agree that an appropriate "Storage" voltage of 3.85v/cell is ideal, and generally is equal to 55% of the battery's capacity. A built-in "Storage-ready" function of battery chargers is one of the reasons I recommend a good quality charger, the "Storage" mode on the UP100AC/UP200AC charger for example will detect what voltage the battery is at and either charge or discharge the battery until it reaches 3.85v/cell. Barring that, your only other option is to remove the battery from the charger periodically and test the resting voltage with a multimeter and stop charging when it is in the 3.85-4.0v/cell range (for 2S that is 7.7-8.0v, 4S is 15.4-16v, 6S is 23.1-24v) Personally I put my LiPos into a storage level capacity anytime I am not using them within the next 24hrs.

TVC / Charge cutoff: When charging LiPos most chargers will automatically end the charge at a terminal voltage cutoff (TVC) of 4.2v/cell (2S is 8.4v, 4S is 16.8v, 6S is 25.2v). However there are both reports from manufacturers as well as evidence from testing that shows what voltage you end your charge at will affect the battery's longevity (number of cycles). Specifically, if you charge up only to 4.15v/cell you will increase the battery cycle life by 40% (i.e. if you expected to get 500 cycles, which is very common, you now will get appx 700 cycles), in exchange when your batteries are "fully charged" at 4.15v/cell you pack will only contain appx 96% of the original capacity (so if it was a 5000mAh pack you would be starting with appx 4800mAh). Alternatively, you can increase the TVC to 4.25v/cell and you will increase the battery pack capacity to 106-108% of rated capacity (so if you have a 5000mAh pack charged to 4.25v/cell it would have appx 5300mAh) in exchange you will be reducing the cycle longevity of the pack to appx 71% (so if you originally expected 500 cycles of normal use, you would now expect just 355 cycles). Below are two graphs (showing results attributable to many other similar tests and research) that show how the TVC affects capacity as well as cycle life. Personally on low-cost packs that cost me $40-60 I stick with 4.2v/cell for my TVC, on packs that cost me $100-200 I use 4.15v/cell as the TVC.


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