Brushless Motor Poles – Radio Control Info

When one refers to How many poles an electric motor has, they are commonly referring to how many magnetic poles there are. Many often wonder the differences between motors having more or less poles. Here, we will focus on a brief discussion concerning Brushless motor magnetic poles. Main focus will be placed on In Runner Motors, where the rotor spins inside of the stator.

Common in runner motors have 2 or 4 magnetic poles. There are some motors containing 6 poles as well. Outrunner motors may have in excess of 6 magnetic poles. You may want to read more on outrunners vs inrunners and what the differences are.

4 Poll Brushless Motor

4 Poll Brushless Motor

Motor Poles vs Motor Characteristics

The largest characteristic that a motor with more poles displays when all else is equal is a drop in the KV value. The KV value as we all know is the amount of RPM per volt. When all else is equal between 2 brushless motors, the one containing a higher pole count will have a lower KV value. This is the number one important characteristic of differences in a motors pole count. All else that we will talk about is based off of this.

How Cogging is effected by Pole Count

If you haven’t already read the article on cogging, I’d recommend following the link to read on this further. It may not be what you thought it was.  Pole counts do influence cogging torque on slotted motors. Generally on inrunner motors, cogging torque increases as you increase in magnetic pole count.

A drop in KV, what does that do? – Brushless Motor Poles

When a motors KV value drops when we keep the motor the same physical size and the number of motor electrical winds (wind / turn) the same, we gain motor torque. The torque is gained as a result of lower KV. Depending on the exact application this may be an advantage or disadvantage. More torque may mean greater acceleration but a lower KV value will reduce maximum RPM achievable.

How Does a Manufacture maintain a usable KV? – Brushless Motor Poles

There is one route a Motor Manufacture may take in order to bring the KV back up to a usable amount. The best option is to decrease the amount of winds in the motor. A 2 Pole motor for example will typically have many more winds than a 4 Pole motor. When a 4 Pole motor has the amount of windings reduced, KV will increase back to the amount needed. When a winding from the motor is removed, the physical size of the motor remains the same resulting in a void. The best solution to this created void is to add more copper. More Copper is added to the winding. This is done in such a way similar to moving down in the Gauge type. In other words the wire used as a wind is now increased in diamater.

As we know from electrical theory, when the cross section of a wire is increased the resistance decreases. This decreased resistance would allow a greater current load to pass through the motor.

Advantages and Disadvantages – Brushless Motor Poles

When comparing a 4 Pole motor that has the same physical size as a 2 Pole motor and the same KV as a 2 Pole motor, the 4 Pole motor in theory would be able to handle greater current loads. The greater current loads will result in greater power. This is similar to saying a 4 pole motor has better overall efficiency when compared to a 2 pole motor.

Although it sounds like there are many advantages, there are also some down falls to this as well. It is very common for 4 pole motors to not have as many motor options as a similar 2 pole motor. Less motor options may make it difficult to get the exact KV value you need. This is even with 4 pole motors using both wind types. A wind type is the difference in how a wind is terminated before it gets to the 3 wires hanging out the brushless motor that you typically see. These wind types are commonly known as the Delta wind and the Wye wind. Using one wind type over another does provide different motor characteristics yet again. We will note this as a possible disadvantage as well.

Which Pole Count Works best for me – Brushless Motor Poles

Overall, it will come down to testing, testing, and testing. These differences explained above may be very subtle to the point where you don’t even note any differences. There may be many reasons to this including your driving habits. In order to determine which works best for you, it is recommended to give both types a try. You may prefer either one of them.

Operating Temperature of Electric and Nitro/Gas Engines

Introduction

In all powered forms of Radio Control Modeling, the operating temperature of the main driving motor or engine is an important factor to consider for longevity and performance. Depending on the load or conditions the motor/engine must face will determine the correct operating temperature.

The operating temperature for a gas, nitro or electric motor/Engine has different characteristics and impacts on overall performance. We will now look into these separately.

Electric Operating Temperatures

In all electric powered models can be found 3 main components. These commonly are the motor, ESC, and Battery. Each component has different heat characteristics and specific operating temperature ranges.

Electronic Speed Control

The general maximum temperature for an ESC ranges from 60C (140F) to 74C. (165F) In general the lower the temperature is, the safer or more reliable your system tends to be. Higher quality ESC’s will tend to be able to operate on the higher end of the safest maximum range.

LiPo Battery

A LiPo battery tends to be the odd component of the 3 main components in an electric system. The reason being is the LiPo battery does not perform its best at colder conditions. However, the LiPo Battery does still have a maximum recommended temperature. This maximum recommended temperature is 60C. (140F) It is recommended to have your LiPo at temperatures above 21C (70F) for optimal performance. Many racers will target higher start off temperatures.

Motor

The motor is critical in the sense that the correct temperature range is followed. It is recommended to keep the motor as cool as possible for optimal performance. As temperatures increase, as does resistance. If the motor were to get too hot, possible magnet demagnetization may set in. This will permananetly damage the motor magnets.

The maximum recommended motor temperatures range between 60C (140F) to 75C. (165F) A water cooled motor should stay on the lower end of this range and a higher quality motor may achieve a higher value. Keep in mind it is best to keep the motor as cool as possible for maximum reliability and performance.

Gas and Nitro Engines

Gas and nitro engines operate best within a specific range. The internal temperature of an internal engine has a large impact on the thermal efficiency of the engine. A nitro engine temperature range typically exists between 82C (180F) and 115C. (240F)

A Gas engine operating temperatures typically exist between 100C (212F) and 155C. (310F)

It is critical to understand that the operating temperatures should not be used as a tuning tool. They are just more of a reference point and to not alarm you if you are experiencing higher temperatures than you thought was safe. Use these temperatures as a guide. Keep in mind that operating temperatures will change through the course of one tank of fuel.

Measuring Thermal Temperatures

To measure thermal temperatures, it is best to use a Temperature Gun. This is the most popular tool that is in use. They can range in price from about $20USD and up depending on brand ect. The second way to determine temperatures is to use a loggin device. Many small logging devices on the market are able to keep a log of temperature vs time. This is a better way for determining temperatures over a long period of time as this better represents the data.

On an internal combustion engine, this reading should be at the plug boss. On an electric component the highest reading found should be recorded. This may exist in multiple locations that build heat.

Prop Box Build – Boat and Airplane Props

Whether you need to store Airplane Props or Boat Props, this DIY (Do it Yourself) Prop Box guide will get the job done.

When Prop Numbers start to increase and it’s getting more difficult to safely store your props, a Prop Box is in desperate need. Safely storing props is always a must as props can be easily damaged.

Although this guide contains photos only for boat props, the same method is used for airplane props. DIY builds are always excellent since you may change the original thought of how it was done to better custom fit your requirements.

Getting Started

Photos will follow each step.

You will need the following materials:
-Some type of box as explained in step one
-Piece of wood that may fit in the interior of the box
-Machine Screws that will fit the bore of your props
-Nuts that will work with the Screws selected
-Nitro Fuel Tubing (Optional but recommended for certain applications)

Tools Needed:
Drill with a bit to match your screw diameter.
Scroll Saw / Band Saw / Or Hand Saw to cut out the wood material
ScrewDriver / Wrench for the fasteners

1)
It is best to pick out an appropriate sized box of any kind that will allow you to fit what ever quantity of propellers you wish to store. The size of the propellers themselves will determine the size of box needed.

Here a simple plastic box that measure approximately 13″ x 11″ x 3″
It had also included the inner foam lining which will be used later. Cost was less than $10.

 

2)
First thing to do is trace out the exact shape by measuring the location in the box where the wood is to be placed. The shape to be cut out is on the bottom left hand corner. 1/4″ piece of scrap MDF was used here. Although any type of wood will work and 1/4″ is plenty thick.

 

3)
After Cutting out the piece of wood, lay the props you will be storing on the wood. This is where it gets interesting as you can lie them out in any fashion you wish. You can keep them tight or space them out. Some may prefer to seperate manufacture and organize by size like I have done, while others may choose a different route. Next drill holes in the location of where the bore of the prop will be. Insert your choice of fasteners in to the holes and secure with a nut. Notice the two holes missing screws. This is for mounting in to the box but will still be used for props. Choose two locations or more where the box mount screws will be fastened.

 

4)
Secure the piece of wood with the fasteners in them to the box by first drilling a hole in the box. Do so by lining up the wood and drilling through the already drilled hole in the wood right through the plastic box. Place a fastener here and secure with a nut. Next, repeat this step with a minimum of one other screw.


5)
This is optional, however recommended. Place a piece of fuel tubing on all the machine screws in the propeller box. This will raise the prop off of the steel nut for added prevention of damage. Standard size fuel tubing can be used, size is not that critical as it can stretch quite well. 1/8″ – 3/16″ in length was cut.


6)
Place all your props on the fasteners. Place another piece of fuel tubing on this side followed by the securing nut. This is the Octura side shown. Each Prop is secured so that it can not move and damage the other props.


This is the Prather side of the box.

 

Here is what the box looks like complete. Here you can see the seperation of the props in terms of manufacture and the organization of the props in terms of size. The smallest size prop located here is an X637 (37mm Diameter) while the largest is a Prather 280 (79mm Diameter)

 

Now it’s only a matter of placing the rest of the props in. The great thing about this layout is it can be disassembled and additional holes can be made. Nothing is secured permanently.

Measuring Speed for all RC Models

For Measuring Electrical Parameters visit – Measuring Electricity

Being able to measure the speed of your Radio Control Model may be important by many. I know my most favourable recorded value is definitely SPEED. The faster, the more thrilling. However, some of you may be wondering how is this possible? How do people determine the speed of their models?

It’s not like an RC Model has a speedometer with a needle that can be read, or does it?

Well not entirely, but fairly close. The majority of people use devices that do not measure speed in real time available that second, however there is units out there that will do this.

There are 3 main sources for determining speed. This includes a Radar Gun, GPS, Or a Logger.

 

Radar Gun – Measuring Speed RC Models

 

 

A popular Radar Gun is one from the Bushnell Series. It is used by holding the trigger down while aiming at the RC model. The advantages of this, is it does not take up any room on the RC model itself. However, it must be used by a seperate person holding the gun.

In most cases it is best to have the RC model passing by your location. A small model may make it more difficult getting a correct reading. And also a model that is more difficult to drive close to the individual holding the gun, will make it that much harder to get an accurate reading. A radar gun only serves one purpose, to measure the speed of an object moving towards or away from you.

 

 

 

GPS Receiver – Measuring Speed RC Models

 

This source of measuring Radio Control Model Speed may be a bit more popular for many. The Garmin etrex is just one of the smaller hand held units that do a great job. The advantages of a GPS unit is it can record a max speed throughout the entire run vs a Radar gun which is just one pass. The GPS will log the entire route and has trip data, visual path data, and some additional data. The size of the unit makes it more difficult to fit into smaller models. I have used this in 1/8th scale on road, most boats, and in a few larger planes. The Garmin Foretrex is just as popular as this model however it has a sleeker smaller case and can be mounted in some locations easier.

Disadvantages include its limitations to certain models, and the fact it must be mounted securely in the RC model.

 

 

 

Data Logger – Measuring Speed RC Models

 

Similar to a GPS, Eagle Tree Systems provide a unit that has an expandable GPS add on. The first item needed is the Data Logger as pictured. To read more on this visit –Measuring Electricity.

The add on GPS module plugs in to the Data Logger. It has the capability to log the models speed in real time. This device may output a graph so not only do you receive max speed, you also get to see where it achieved maximum speed. It’s Disadvantages include having to use two devices at the same time. This may be difficult to mount as they do not have a hard case. However for this reason, everything is kept extremely light making it excellent for RC Airplanes, Cars, or Boats. The capabilities are quite high as it is not only used for determining speed.