Hey and hello to Part 3 of "Anatomy of a RC Crawler" by Sabaot.
Previously we covered topics of Radios and overall look at a Crawler. Now - the motor time, our model's engine.
It gives power and moves out Crawler. It is an electric device that converts electric power into magnetic field that rotates a
motor's shaft providing torque. In simple words: electric motor changes electric power into mechanical power.
Currently we have several types of RC motors that can be used in a RC models (mind that used "models", not "Crawler"):
- electric brushed
- electric brushless
- nitro powered
- gasoline powered
- turbine
For our Crawler the only suitable and viable options are those first two (both electric ones). Why? Turbines are too big,
costy and produce way too much power, not to mention the noise. They are perfect for flying models (bigger scale) and
maybe in some fast RC Cars (dragster?). Nitro/Gas powered are heavy, noisy and fast engines (same constructions are in
real cars) and they are too powerfull for our needs. Probably you can construct a nitro Crawler but it surely be a
tremendous task - especially in terms of torque transmission between motor and wheels.
So only electric stays, for several reasons:
- they provide quite good power compared to size
- are quiet
- you can operate it slowly to achieve more torque or fast for speed
- easier to maintain
Now let's talk about difference between brushed and brush-less. If you want a deep-in comparison and explanations visit
Auntie Wiki, there you will find much more detailed info about construction and differences. Now lets focus on basics.
BrushED motor.
Older design that is based on an element that we call "a brush" (hence the name). Brushes in this motor are responsible
for altering electric power into mechanical power. I'm no physics master but I will try to explain it: brushed motor consist of
2 parts - inside and outside (for the sake of simple example lets leave it that way). Inside part has brushes, metal things
that connects inside with outside. When you put power to the engine, inside and outside creates a magnetic field. Electric
power runs from inside to outside through brushes, making it spin. And spinning is our output torque.
Pros of a BrushED motor:
- cheap
- easy construction
- water resistant (you can submerge it completely and it will be running without any problem)
Cons:
- less reliable (brushes gets used, they don't fit well with time which makes motor run less and less effectively)
- prone to overheating
- internal damage can jam the motor
Wire winding, turns and other stuff.
The mentioned inside of a motor consists of frames on which there is a copper wire wrapped around. This is important
because the amount of wire rounds decides on overall motor's performance, and it's described as a T factor (eg. 12T motor,
21T motor). Many of new RC modellers ask questions - what does it means (myself included). To K.I.S.S.:
T = "turns" = amount of times the copper wire is wrapped around moving part of a motor.
LOW T (eg. 12T) = weak motor, but fast motor (good for achieveing higher speed)
HIGH T (eg. 25T) = strong motor, but slow motor (perfect for crawling)
There are other vital factors but for now it is suffice to know the above. Rest will come with time.
BrushLESS motor (commonly abreviated BL).
This is newer design and what makes it special, well you guessed that, it has no brushes. Its internal design is based on
magnets which has lots of advantages over brushED one. First thing is that BL is far more reliable and has longer life span
(no brushes that can malfunction). BL provides more power compared to the same size/class brushED. No risk of
overheating when running idle (well, every electric motor can overheat while working under stress, we are talking here a
fact that internal design avoids physical contact like brushes in brushED hence no friction that produces heat. And be
aware - DO NOT RUN BL BY ITSELF - YOU CAN DAMAGE IT OR/AND DESTROY).
But it has also drawbacks - no roses without thorns. It's more expensive in purchase, requires specially designed speed
controller and IT IS NOT water resistant.
Kv.
Similarily to "turns" in brushED motors, BL have their own efficiency indicator - kv factor.
kv = rpm/v (<revolves per minute> per volt).
It describes how fast out BL will spin under certain power input as it can reach different max values under different
batteries (more about batteries later on). For now lets compare max RPM under 7.4v and 11.1v. Digits time.
I have a motor described as a 3,500kv. This means it can reach 3,500 RPM per 1v of input power, so:
running it with a 7.4v battery 3,500 * 7.4v = 25,900 max RPM
running with a 11,1v battery 3,500 * 11.1v = 38,8500 max RPM
The higher volt input, the faster motor will spin. But mind the motor's max RPM value. Mine has max of 50,000 RPM so max volt input I can plug in is 14.2v (3,500 * 14.2v = 49,700 RPM). Over that I can destroy it.
But motor isn't connected to shafts directly. Can you imagine a Crawler that spins its wheels at 40 THOUSAND rounds per minute? It's 666.666 (devil's amount, literally. And not intended example) spins per second! Drifter, not Crawler. So, to fix that Crawlers possess a special part - transmission gear (btw, this it the part where shafts go into).
More about that particular piece in Part 4 of the "Anatomy of a RC Crawler" by Sabaot. Stay tuned.
Again - likes, dislikes, flames? Post in a comment.
Previously we covered topics of Radios and overall look at a Crawler. Now - the motor time, our model's engine.
It gives power and moves out Crawler. It is an electric device that converts electric power into magnetic field that rotates a
motor's shaft providing torque. In simple words: electric motor changes electric power into mechanical power.
Currently we have several types of RC motors that can be used in a RC models (mind that used "models", not "Crawler"):
- electric brushed
- electric brushless
- nitro powered
- gasoline powered
- turbine
For our Crawler the only suitable and viable options are those first two (both electric ones). Why? Turbines are too big,
costy and produce way too much power, not to mention the noise. They are perfect for flying models (bigger scale) and
maybe in some fast RC Cars (dragster?). Nitro/Gas powered are heavy, noisy and fast engines (same constructions are in
real cars) and they are too powerfull for our needs. Probably you can construct a nitro Crawler but it surely be a
tremendous task - especially in terms of torque transmission between motor and wheels.
So only electric stays, for several reasons:
- they provide quite good power compared to size
- are quiet
- you can operate it slowly to achieve more torque or fast for speed
- easier to maintain
Now let's talk about difference between brushed and brush-less. If you want a deep-in comparison and explanations visit
Auntie Wiki, there you will find much more detailed info about construction and differences. Now lets focus on basics.
BrushED motor.
Older design that is based on an element that we call "a brush" (hence the name). Brushes in this motor are responsible
for altering electric power into mechanical power. I'm no physics master but I will try to explain it: brushed motor consist of
2 parts - inside and outside (for the sake of simple example lets leave it that way). Inside part has brushes, metal things
that connects inside with outside. When you put power to the engine, inside and outside creates a magnetic field. Electric
power runs from inside to outside through brushes, making it spin. And spinning is our output torque.
Pros of a BrushED motor:
- cheap
- easy construction
- water resistant (you can submerge it completely and it will be running without any problem)
Cons:
- less reliable (brushes gets used, they don't fit well with time which makes motor run less and less effectively)
- prone to overheating
- internal damage can jam the motor
Wire winding, turns and other stuff.
The mentioned inside of a motor consists of frames on which there is a copper wire wrapped around. This is important
because the amount of wire rounds decides on overall motor's performance, and it's described as a T factor (eg. 12T motor,
21T motor). Many of new RC modellers ask questions - what does it means (myself included). To K.I.S.S.:
T = "turns" = amount of times the copper wire is wrapped around moving part of a motor.
LOW T (eg. 12T) = weak motor, but fast motor (good for achieveing higher speed)
HIGH T (eg. 25T) = strong motor, but slow motor (perfect for crawling)
There are other vital factors but for now it is suffice to know the above. Rest will come with time.
BrushLESS motor (commonly abreviated BL).
This is newer design and what makes it special, well you guessed that, it has no brushes. Its internal design is based on
magnets which has lots of advantages over brushED one. First thing is that BL is far more reliable and has longer life span
(no brushes that can malfunction). BL provides more power compared to the same size/class brushED. No risk of
overheating when running idle (well, every electric motor can overheat while working under stress, we are talking here a
fact that internal design avoids physical contact like brushes in brushED hence no friction that produces heat. And be
aware - DO NOT RUN BL BY ITSELF - YOU CAN DAMAGE IT OR/AND DESTROY).
But it has also drawbacks - no roses without thorns. It's more expensive in purchase, requires specially designed speed
controller and IT IS NOT water resistant.
Kv.
Similarily to "turns" in brushED motors, BL have their own efficiency indicator - kv factor.
kv = rpm/v (<revolves per minute> per volt).
It describes how fast out BL will spin under certain power input as it can reach different max values under different
batteries (more about batteries later on). For now lets compare max RPM under 7.4v and 11.1v. Digits time.
I have a motor described as a 3,500kv. This means it can reach 3,500 RPM per 1v of input power, so:
running it with a 7.4v battery 3,500 * 7.4v = 25,900 max RPM
running with a 11,1v battery 3,500 * 11.1v = 38,8500 max RPM
The higher volt input, the faster motor will spin. But mind the motor's max RPM value. Mine has max of 50,000 RPM so max volt input I can plug in is 14.2v (3,500 * 14.2v = 49,700 RPM). Over that I can destroy it.
But motor isn't connected to shafts directly. Can you imagine a Crawler that spins its wheels at 40 THOUSAND rounds per minute? It's 666.666 (devil's amount, literally. And not intended example) spins per second! Drifter, not Crawler. So, to fix that Crawlers possess a special part - transmission gear (btw, this it the part where shafts go into).
More about that particular piece in Part 4 of the "Anatomy of a RC Crawler" by Sabaot. Stay tuned.
Again - likes, dislikes, flames? Post in a comment.