How to choose motor for gearbox?

[Ussli]

How to choose motor for gearbox?

I have been playing airsoft for a long time and specialize in modification of motors and gears. Many friends don’t know how to choose a suitable motor, here I will share my motor research for the friends who need it.

There are two types of motors according to the working principle, brushed motor and brushless motor. Brushed motor is widely used in airsoft for its low cost and good performance. Now lets talk about brushed motor first.

A、Some common parameters of the motor

Specification of motor　

The motors commonly used for V2 and V3 are 460, 470 and 480 motors. Taking the 480 motor as an example, 4 represents a rotor length of 40mm and 8 represents a diameter of 8mm. The larger the diameter, the more copper wire can be wound, which can improve the performance of the motor. Due to the limitation of installation space, 480 motor is the largest size motor that can be used by conventional airsoftguns.
Long axis & short axis: refers to the length of the motor shaft.

Motor for V2 gearbox is separated from gearbox, installed in the grip, it’s long axis motor.

Motor for V3 gearbox is installed in a motor frame which is fixed in gearbox, it’s short axis motor.

 

Torque:

For easily understand, the torque is the power of the motor. The bigger the torque, the stronger the power, and the larger spring it can driven.

Rotating Speed

The speed of motor’s no-load rotation, the higher the speed, the higher the RPS. Usually there will be a mark of voltage and rotating speed on the motor, for example, 11.1V 28000RPM.

TPA:

Turn per Arm. The number of coils wound on the rotor, mainly affects the speed. Generally, the higher the number of turns, the lower the speed and the lower the heat generation. Many people like to use TPA to judge the performance of a motor, but this is not a scientific way. Don't worry, continue to read this article, I believe you will understand how to comprehensively judge whether a motor is suitable for you.

Magnetic tile type

Ordinary magnetic tile and strong magnetic tile：

Usually, the stronger the magnetism, the larger the motor torque, the shorter the startup response time, the higher the electromagnetic conversion efficiency, and the faster the motor stops.

Ordinary magnetic tile:

It is a black magnet, general magnetism, belongs to low torque motor. Mostly used for some cheap original guns, why? Because the cost is low enough.

Strong magnetic tile

Commonly used are NdFeB rare earth materials, according to the process, it is divided into two types: bonding and sintering. The bond magnetism is medium, generally used for medium torque motors, Sintered magnetic is the strongest, usually used in high torque motors. Since NdFeB is easy to oxidize, the magnet needs to be electroplated, and the surface will be electroplated silver. Through the motor shell, we can observe the magnetic tile to identify. (Note that many fakes will also use ordinary black magnets to pretend to be NdFeB magnets by electroplating or painting silver)

Depending on the performance of the magnetic tile, common specifications are as follows:

N35 N35M N35H etc.

N35 refers to the magnet material code, the common ones are N28, N30, N33, N35, N38, N40, N42, N45, N48, N50, N52, (N56, N58).

The larger the number, the stronger the magnetic performance and the higher the price.

The most commonly used ones for making 480 motors are N35, N38, N52. For cost reasons, magnets above N52 are rarely used to manufacture 480 motors. N52 is currently the strongest 480 motor magnetic tile.

The code behind the number refers to the temperature resistance level. Without exceeding this temperature, the magnet will not demagnetize significantly, and doesn’t affect performance.

For the same letter, the temperature resistance limit of each magnet tile grade is not exactly the same.

The summary information is as follows:

No letter: 70-80°C

M：100°C

H：120°C

SH：150°C

UH：180°C

EH：200°C

AH：240°C

If it is a normal N35 magnet 480 motor, due to the continuous heating of the motor, when the temperature exceeds 80°C, there will be permanent loss of magnetism, the higher the temperature, the bigger the loss. Therefore, some guns will feel that their performance has decreased after a period of use, which may be caused by the performance loss of the motor, especially for gearboxes using electronic trigger unit, when playing single shot, the electronic trigger unit frequently brakes the motor, the temperature rise will be more obvious, and it is easier to exceed 80°C for long-time use, and a magnet with a higher temperature resistance must be used in order to maintain the durability of motor performance.

According to my personal experience, it is recommended to use H level or above to better protect the performance and life of the motor. Of course, the higher the temperature resistance level, the higher the price.

Another rare-earth permanent magnet used in high-torque strong-magnetic 480 motor is samarium cobalt magnet. Compared with NdFeB magnets, the temperature resistance limit is higher (the highest temperature resistance level can exceed 500°C), but the disadvantage is that the magnetism is weaker and the cost is higher, it is not the best choice for gearbox motor, therefore, the current mainstream high-torque strong-magnetic 480 motor use NdFeB to achieve a balance between comprehensive performance and price.

B、Structure of 480 Motor

 

1. Bottom cover

2. Motor shell

3. Fixing spring

4. Motor teeth

5. Shaft sleeve

6. Electrodes

7. Carbon brush fixing spring

8. Carbon brush

[Ussli]

 

B、Structure of 480 Motor

1. Bottom cover

There are two common materials for the bottom cover, one is plastic and the other is metal. The two bases have their own advantages and disadvantages. The plastic bottom cover has low cost and good insulation, and it is not easy to cause a short circuit accident when the power cord is broken or loosened.

However, the heat resistance limit of plastic is not as good as that of metal,

At high temperature (over 250°C), it may deform and cause failure. But in fact, it is difficult to achieve such a high temperature in normal use. If there is such a high temperature, the motor itself will almost be scrapped, so this is not a very direct disadvantage at all. The CNC metal bottom cover is just the opposite. High cost and poor insulation (Most factories will spray insulating paint on the surface, but the insulating layer may be worn during disassembly and assembly, so be sure to insulate the power cord just in case), high temperature resistance, and help to dissipate heat.

2. Motor shell
   The casings are basically made of metal, and some will have heat dissipation holes. However, since the motor is installed in the handle, both sides are sealed, not open space, and there is not enough heat dissipation space. Therefore, opening the heat dissipation holes has limited improvement in the heat dissipation effect.
3. Fixing spring
   Keep the motor in a stable longitudinal position in the grip or motor frame. Fixing the position of the motor relies on the force on both sides of the screw of the grip bottom cover and the spring, they clamp the motor in a fixed position to achieve the effect of stable gear engagement.
4. Motor gear
   The motor gear is used to engage the bevel gear of the gearbox to drive the action in the gearbox. Generally, there are two kinds of materials: nylon and metal. Metal is divided into three types: powder die casting, injection, and steel cutting. Note that the motor gear and the bevel gear must be made of the same material, otherwise the nylon gear will be aggravated and damaged.
5. Shaft sleeve
   The shaft sleeve extends into the motor hole of the handle and the gearbox to fix the lateral position of the motor. If the lateral position is not fixed, the gears will be mis-engaged, which will aggravate the wear of the gears and cause damage. A good shaft sleeve and motor shaft will be fixed with bearings for better stability.
6. Electrodes
   There are positive and negative electrodes on the motor tail cover, which are used to connect the power cord.
7. Carbon brush fixing spring
   Keep the carbon brush in tight contact with the rotor commutator.
8. Carbon brush

There are two carbon brushes, which are respectively connected to the positive and negative electrodes, and the inner side is in contact with the rotor commutator to supply power to the rotor coil. Note that carbon brushes are consumables. After friction loss, they will not be able to supply power to the motor, and new carbon brushes need to be replaced. (Some friends find that the motor can’t work after using it for a period of time, and they think that the motor is damaged and replace the motor. In fact, check the wear of the carbon brushes at this time. It is very likely that the carbon brushes are worn out. Just replace a pair of carbon brushes. Repair the motor) carbon brushes commonly include graphite carbon brushes, copper-containing carbon brushes, (there is also a silver-containing carbon brush, the cost is high, 480 motors are generally not used). Graphite carbon brushes are relatively soft, not wear-resistant, and wear out very quickly and need to be replaced frequently. Copper-containing carbon brushes are divided into high-copper carbon brushes and semi-copper carbon brushes according to the copper content. The higher the copper content, the better the wear resistance and life, and the higher the price. However, too high copper content will lead to high hardness of the carbon brushes and aggravate the wear of the rotor commutator, so I prefer to use semi-copper carbon brushes to achieve a balance of life of each part.

 

 

 

 

Rotor structure

1. Rotating shaft
   Connectthe motor teeth, the heads are all D-shaped shafts
2. Iron core
   Used to wind coils, generally made of silicon steel sheets.
3. Coil
   Use enameled wire for winding. The thicker the wire diameter, the larger the current and the bigger the power. By the way, here is an explanation of the TPA and motor performance mentioned above. Under the same conditions, the larger the number of coils (TPA), the greater the torque and the lower the speed. The smaller the number of coils (TPA), the smaller the torque and the higher the speed. The upper performance of the gearbox is that high TPA can pull larger springs, but there will be lower RPS, and low TPA can obtain higher RPS, but cannot pull too high springs. At the same time, due to space constraints, if you want to get a higher TPA, you need to use a thinner wire, the current will be smaller, and the power of the motor will be lower, so the heat of the high-TPA motor will be relatively lower. We cannot blindly pursue high TPA or low TPA, we must choose the appropriate TPA according to the gears and springs (I recommend referring to the no-load speed of the motor to match the gearbox to obtain ideal performance, later I will talk about how to calculate and match)
4. Commutator
   Contact with the carbon brush to supply power to the coil, which is a wear part, and can continue to be used by replacing the rotor after reaching the service life. However, the life of the commutator is usually much longer than that of the carbon brush, so the commutator can continue to work after the carbon brush is replaced several times (depending on the type of carbon brush).
5. Base fixing shaft
   Fixed in the bottom cover to keep the motor axially stable. A good motor will use bearings to hold it in place to avoid wear and tear over long periods of time.

 

6. Wind blade
   Some motors will install a plastic wind blade at the end of the iron core, which can drive the airflow to help dissipate heat when rotating,it is helpful for the motor that runs for a long time.

[Ussli]

Consecutive previous content part 2-Ussli.com

C、How to choose the motor

Through the above study, we have a general understanding of the motors used by airsoft, so how to choose a motor according to our own needs?
Let's first understand the relationship between motors, gears, and RPS.

RPS=(motor no-load speed/60/gear ratio)*motor efficiency coefficient
The no-load speed of the motor is generally based on 11.1V. Below 25,000 is a low-speed motor, 25,000-35,000 is a medium-speed motor, 35,000-45,000 is a high-speed motor, and above 45,000 is an ultra-high-speed motor.

Gear ratio: The gear box is a set of deceleration gears in terms of the original working quantity. For example, 18:1 means that the motor rotates 18 times, driving the gearbox to complete one shot. The most common ones are 18;1,16:1 and 13: 1. Of course, there are also 12:1, 32:1 and DSG 9:1, TSG 6:1 and other specifications. (I will write a separate article about the choice of gears to introduce)

Motor efficiency: When the motor is running with load, the speed will be lower than that with no load. The actual load efficiency value is related to the performance and load of the motor itself. Generally speaking, the motor efficiency of the motor with strong magnetism and high torque can usually reach 0.8-0.95 , The middle torque can reach 0.7-0.8, and the low torque is below 0.7 (if the load is large, the motor efficiency will be reduced, the same motor may be slightly lower in the high FPS gearbox)
For example, we use a 22000 rpm original motor with 18:1 gear, and the estimated efficiency is 0.8. In theory, we can get (30000/60/18)*0.7=14.2RPS
If you want to increase the RPS to about 20, there are several ways.

Method 1 is to use the original motor to replace the 13:1 gear (22000/60/13)*0.7=19.7RPS. (Note that this method may have problems and will be discussed later)

Method 2 is to replace the ordinary motor with 30000 rpm, for example (30000/60/18)*0.7=19.4 RPS

Method 3 Replace the 16:1 teeth and use a high torque 22000 rpm motor, for example (22000/60/16)*0.85=19.5RPS

We can see that the easiest way is to replace the motor with a suitable speed, because the replacement of the motor is the most convenient and fast, only need to remove two grip base screws (V3 gearbox generally needs to remove one more screw), it is easy to replace by yourself. To replace the gear set, it is necessary to disassemble the gearbox and adjust the teeth again, which is very cumbersome and difficult for many players. Of course, there are certain limitations to adjusting the performance of the gearbox only by replacing the motor, but for beginners, replacing the motor does not require opening the gearbox, which is the easiest performance modification to get started. As mentioned above, one problem with method 1 is that if a 13:1 gear is used, it is very difficult for many low-torque motors to pull the spring, and it will be necessary to replace the medium-torque or high-torque motor. It also depends on the spring used.

Knowing the basic principle of matching the motor, we can choose the appropriate motor according to different needs

I have compiled a principle that I follow when helping my teammates modify the rifle for your reference.

• Rookie: bought an original rifle, and if want to simply improve the RPS and FPS, youcan choose a cheap high-speed motor and spring (note that the low-torque motor is not recommended when the FPS exceeds 300). If the gears are nylon gears, do not use a high-torque motor, excessive torque may cause a sharp decrease in the life of the nylon gears. If you want to upgrade to a high-torque motor, first upgrade the gear to a metal gear.
• Want to change FPS, after replacing the large spring, upgrade the high-torque medium-speed motor to ensure that the motor has enough torque to efficiently pull the spring.
• Want to change RPS, upgradea high-torque and medium-high-speed motor, and match it with a small gear ratio suitable for 16:1 or 13:1 gear to obtain the required RPS. Note that even if the FPS value is not high, we do not recommend the use of low-torque motors, because high-RPS gearboxes usually use metal gears. Due to the weight of the gear (The hollow design of the advanced gear will reduce the weight by 20%), the high speed and the large inertia, the braking performance of the low-torque motor is relatively poor after the trigger is released, and the inertial firing will still occur after the trigger is released. The high-torque motor has stronger braking performance, the inertial firing situation will be improved a lot, the feel of the entire shooting will be improved a lot, and the response time and heat of the first shot will also be improved.
• Gearbox with ETU(electronic trigger unit):Because the ETU has requirements on the torque and braking performance of the motor, the ETU needs to be matched with a medium or high torque motor. ETU users can be divided into three categories:
• Listen to the old players sayingETU is good, follow the trend and use ETU without thinking: Just choose a medium or high torque motor according to FPS and RPS. In fact, such people have not yet realized the difference in feel between mechanical switche and ETU, and even if they use the best motors, they may not understand the difference.。
• Mainly play AUTO, install ETU in order to improve the shooting feel (smooth brakes): It is recommended to usethe medium-high-speed, high-torque motors, which can get faster RPS and comfortable feel. The higher the torque motor, the quicker the starting response, the faster the braking, and the lower the heat generation.
• Those who mainly play SEMI, especially SQB players: using a high-torque motor is an entry-level configuration. For players who play in the back row and need single-shot firepower to suppress, the motor needs to continuously start the brakes, which requiresa certain performance and also heat generation will dramatic increase. At this time, it is recommended to use a brushed motor with the highest torque and high temperature resistance magnetic tile. If the budget is sufficient, you can consider upgrading to a brushless motor. However, a factor needs to be considered at this time, because the circuit logic of some ETUs may conflict with the circuit control logic of some brushless motor motherboards, and incompatibility may occur during work. Long-term use will affect the performance of brushless motors. Compatibility needs to be tested in advance when choosing a brushless motor. The brushed motor and ETU will not have this problem, the biggest problem is the wear of the carbon brush.

Since the motor heating caused by the ETU brake is much higher than that of the mechanical switch, it is recommended to use a low-heating and high-temperature resistant high-torque motor.

• Players who only hang the rifle on the wall or play at home：it is the same with or without a motor.
• Players needextreme violent RPS and FPS：Currently only brushless motors can meet your challenge of extreme performance.

 

Knowing so much, we can basically draw a conclusion: without considering the budget, the priority order of motor selection is always: brushless > high torque > medium torque > low torque
As the saying goes, you get what you pay for, and this can also be intuitively fed back from their prices. The brushless motor has the highest price, the higher the torque motor, the higher the price, and the lower the torque motor, the cheaper the price. Of course, there are some bad manufacturers who falsely standardize the performance and pull the price, and it is possible to buy products whose performance does not meet the standard. However, Cheap motors are basically impossible to have good overall performance.

Finally, summarize several parameters for selecting the motor:

Tips: TPA only represents the number of turns of the coil, but the performance and diameter of the copper wire of the coil are not the same, the quality of the silicon steel sheet of the rotor core of the motor is also different, and the performance of the final coil and the rotor are not necessarily the same. TPA can only be compared under the premise of the same wire, and it is only suitable for reference.

The above sharing is only personal use experience, just for your reference, if there is anything unprofessional or rigorous, please point out.

[colinjallen]

Thanks for posting that; I am sure that you felt it was useful.

[Guest]

On 07/05/2022 at 06:18, Ussli said:

Consecutive previous content part 2-Ussli.com

C、How to choose the motor

Through the above study, we have a general understanding of the motors used by airsoft, so how to choose a motor according to our own needs?
Let's first understand the relationship between motors, gears, and RPS.

RPS=(motor no-load speed/60/gear ratio)*motor efficiency coefficient
The no-load speed of the motor is generally based on 11.1V. Below 25,000 is a low-speed motor, 25,000-35,000 is a medium-speed motor, 35,000-45,000 is a high-speed motor, and above 45,000 is an ultra-high-speed motor.

Gear ratio: The gear box is a set of deceleration gears in terms of the original working quantity. For example, 18:1 means that the motor rotates 18 times, driving the gearbox to complete one shot. The most common ones are 18;1,16:1 and 13: 1. Of course, there are also 12:1, 32:1 and DSG 9:1, TSG 6:1 and other specifications. (I will write a separate article about the choice of gears to introduce)

Motor efficiency: When the motor is running with load, the speed will be lower than that with no load. The actual load efficiency value is related to the performance and load of the motor itself. Generally speaking, the motor efficiency of the motor with strong magnetism and high torque can usually reach 0.8-0.95 , The middle torque can reach 0.7-0.8, and the low torque is below 0.7 (if the load is large, the motor efficiency will be reduced, the same motor may be slightly lower in the high FPS gearbox)
For example, we use a 22000 rpm original motor with 18:1 gear, and the estimated efficiency is 0.8. In theory, we can get (30000/60/18)*0.7=14.2RPS
If you want to increase the RPS to about 20, there are several ways.

Method 1 is to use the original motor to replace the 13:1 gear (22000/60/13)*0.7=19.7RPS. (Note that this method may have problems and will be discussed later)

Method 2 is to replace the ordinary motor with 30000 rpm, for example (30000/60/18)*0.7=19.4 RPS

Method 3 Replace the 16:1 teeth and use a high torque 22000 rpm motor, for example (22000/60/16)*0.85=19.5RPS

We can see that the easiest way is to replace the motor with a suitable speed, because the replacement of the motor is the most convenient and fast, only need to remove two grip base screws (V3 gearbox generally needs to remove one more screw), it is easy to replace by yourself. To replace the gear set, it is necessary to disassemble the gearbox and adjust the teeth again, which is very cumbersome and difficult for many players. Of course, there are certain limitations to adjusting the performance of the gearbox only by replacing the motor, but for beginners, replacing the motor does not require opening the gearbox, which is the easiest performance modification to get started. As mentioned above, one problem with method 1 is that if a 13:1 gear is used, it is very difficult for many low-torque motors to pull the spring, and it will be necessary to replace the medium-torque or high-torque motor. It also depends on the spring used.

Knowing the basic principle of matching the motor, we can choose the appropriate motor according to different needs

I have compiled a principle that I follow when helping my teammates modify the rifle for your reference.

• Rookie: bought an original rifle, and if want to simply improve the RPS and FPS, youcan choose a cheap high-speed motor and spring (note that the low-torque motor is not recommended when the FPS exceeds 300). If the gears are nylon gears, do not use a high-torque motor, excessive torque may cause a sharp decrease in the life of the nylon gears. If you want to upgrade to a high-torque motor, first upgrade the gear to a metal gear.
• Want to change FPS, after replacing the large spring, upgrade the high-torque medium-speed motor to ensure that the motor has enough torque to efficiently pull the spring.
• Want to change RPS, upgradea high-torque and medium-high-speed motor, and match it with a small gear ratio suitable for 16:1 or 13:1 gear to obtain the required RPS. Note that even if the FPS value is not high, we do not recommend the use of low-torque motors, because high-RPS gearboxes usually use metal gears. Due to the weight of the gear (The hollow design of the advanced gear will reduce the weight by 20%), the high speed and the large inertia, the braking performance of the low-torque motor is relatively poor after the trigger is released, and the inertial firing will still occur after the trigger is released. The high-torque motor has stronger braking performance, the inertial firing situation will be improved a lot, the feel of the entire shooting will be improved a lot, and the response time and heat of the first shot will also be improved.
• Gearbox with ETU(electronic trigger unit):Because the ETU has requirements on the torque and braking performance of the motor, the ETU needs to be matched with a medium or high torque motor. ETU users can be divided into three categories:
• Listen to the old players sayingETU is good, follow the trend and use ETU without thinking: Just choose a medium or high torque motor according to FPS and RPS. In fact, such people have not yet realized the difference in feel between mechanical switche and ETU, and even if they use the best motors, they may not understand the difference.。
• Mainly play AUTO, install ETU in order to improve the shooting feel (smooth brakes): It is recommended to usethe medium-high-speed, high-torque motors, which can get faster RPS and comfortable feel. The higher the torque motor, the quicker the starting response, the faster the braking, and the lower the heat generation.
• Those who mainly play SEMI, especially SQB players: using a high-torque motor is an entry-level configuration. For players who play in the back row and need single-shot firepower to suppress, the motor needs to continuously start the brakes, which requiresa certain performance and also heat generation will dramatic increase. At this time, it is recommended to use a brushed motor with the highest torque and high temperature resistance magnetic tile. If the budget is sufficient, you can consider upgrading to a brushless motor. However, a factor needs to be considered at this time, because the circuit logic of some ETUs may conflict with the circuit control logic of some brushless motor motherboards, and incompatibility may occur during work. Long-term use will affect the performance of brushless motors. Compatibility needs to be tested in advance when choosing a brushless motor. The brushed motor and ETU will not have this problem, the biggest problem is the wear of the carbon brush.

Since the motor heating caused by the ETU brake is much higher than that of the mechanical switch, it is recommended to use a low-heating and high-temperature resistant high-torque motor.

• Players who only hang the rifle on the wall or play at home：it is the same with or without a motor.
• Players needextreme violent RPS and FPS：Currently only brushless motors can meet your challenge of extreme performance.

 

Knowing so much, we can basically draw a conclusion: without considering the budget, the priority order of motor selection is always: brushless > high torque > medium torque > low torque
As the saying goes, you get what you pay for, and this can also be intuitively fed back from their prices. The brushless motor has the highest price, the higher the torque motor, the higher the price, and the lower the torque motor, the cheaper the price. Of course, there are some bad manufacturers who falsely standardize the performance and pull the price, and it is possible to buy products whose performance does not meet the standard. However, Cheap motors are basically impossible to have good overall performance.

Finally, summarize several parameters for selecting the motor:

Tips: TPA only represents the number of turns of the coil, but the performance and diameter of the copper wire of the coil are not the same, the quality of the silicon steel sheet of the rotor core of the motor is also different, and the performance of the final coil and the rotor are not necessarily the same. TPA can only be compared under the premise of the same wire, and it is only suitable for reference.

The above sharing is only personal use experience, just for your reference, if there is anything unprofessional or rigorous, please point out.

TL:DR

 

That’s a massive post. 

[Ussli]

On 08/05/2022 at 02:20, colinjallen said:

Thanks for posting that; I am sure that you felt it was useful.

I'm thinking about releasing gear. I am waiting for time. recent research on laser tag.

[colinjallen]

8 hours ago, Ussli said:

I'm thinking about releasing gear. I am waiting for time. recent research on laser tag.

I have no idea what you are trying to say.

我不知道你想说什么。

[Ussli]

On 11/05/2022 at 02:16, colinjallen said:

I have no idea what you are trying to say.

我不知道你想说什么。

Adjust the fit of the gearbox gears；The laser tag is another gun, which fires through the helmet and armor induction, and is controlled through the center console. I'm assembling this gun recently.