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The different types of RC helicopter design from conventional, coaxial to quad rotor

BRAND NEW! The Lil’ Draganflyer Mini Quadrotor is a great beginner RTF Helicopter.

Lil' Draganflyer Quadrotor RC Helicopter

The Lil’ Draganflyer Mini Quadrotor is an ideal beginner 4-channel Ready-to-Fly 2.4GHz electric helicopter. Use it indoors or outdoors for unlimited fun. The Lil’ Draganflyer has flight characteristics similar to its bigger brothers, the Draganflyer X4, X4-P, X6, and X8. With three gyros, the Lil’ Draganflyer offers unsurpassed stability and incredible control. The 2.4GHz digital proportional 4-channel remote control ensures strong, glitch-free performance. Because of its small size, the Lil’ Draganflyer is easy to fly indoors, but it is also powerful enough to fly outdoors even with mild winds.

The Lil’ Draganflyer comes 100% assembled and Ready-to-Fly right out of the box with no assembly required.

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Posted in Electric RC Helicopters - Quad Rotor - Draganflyers, Learn to Fly RC Helicopters, Quad-Rotor RC Helicopter Design, RC Helicopter Controls, Throttle, Yaw, Pitch, Roll, RC Helicopter Flight Training, RC Helicopter Training Gear, RC Helicopters Using Electric Power

RC Helicopter Quad Copter Propellers Tested – Huge Amount of Data, Free for Download

There is a spreadsheet available with test data from over 251 unique propellers frequently used on RC helicopters and RC quad copters. Dr Phil Millener, Chattanooga, Tennessee (RCGroups.com user “Dr Kiwi”) made a spreadsheet of test data from lots of commonly used RC airplane and quad copter propellers, and gave us permission to make the file available to you for download. For your convenience, there is also a reformatted version which only contains the results without any macros (available in .xls format and .csv format.)

This spreadsheet has over 13000 data points for different propellers. Each row contains the following information:

  • Propeller Name
  • Motor Used
  • Gear
  • Propeller Diameter
  • Propeller Pitch
  • Amps, Volts and Watts drawn
  • RPM
  • RPM as % of Kv * V
  • Motor Weight
  • Motor and Gearbox weight
  • Thrust (in g and oz)
  • Grams per Watt
  • Pitch Speed

From this data, you can make a more educated choice on which propeller is best for your application. Looking at figures such as the number of grams per watt obtained can help you choose between similar propellers by giving you an estimate of which ones are more efficient in different situations. Depending on if you’re building a quad copter for hovering and aerial photography, or a high performance RC airplane, you can now get an objective picture of the differences between the propellers.

Because simulating how propellers perform in the real world is difficult, testing is necessary to measure their true performance. Before now, finding a unified source of data for many different propellers was difficult.

Here’s some example data, taken for an APC 8×6 E Thin Electric Propeller with a Hacker A20-22L  brushless motor:

Volts Amps Watts RPM Thrust (g) g/W
10.9 13.55 148 8650 567 3.83
9.9 11.7 116 8100 484 4.17
8.9 9.85 88 7440 406 4.61
7.9 8.2 65 6780 333 5.12
6.9 6.65 46 6120 267 5.80

If you wanted to know how this propeller performs with this motor as RPM is increased, you could make a plot like this in any spreadsheet program.

Adding a trendline to the data allows you to make a prediction about the thrust this propeller and motor would provide at other RPM values. A simple polynomial fits the measured data well.

Another quantity you might be interested in is the efficiency of the propeller and motor in grams of thrust produced per watt of power used. Here is one such plot.

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Posted in Latest RC Helicopter News, Quad-Rotor RC Helicopter Design

The E-Flite MASH Electric RC Rescue Helicopter Crash Kit – What you Get, How to use it, and How it Saves You Money

RCtoys.com has been selling the MASH rescue helicopter by E-flite for a few months now, and it’s turned out to be a great little scale helicopter for indoor flight. The MASH helicopter looks great in the air and handles better than most co-axial RC helicopters out there. It’s also got a fair bit of weight, making it great for flying outdoors in low winds. The MASH helicopter is so easy to fly that it’s perfect for anyone who’s new to RC, but sometimes we make mistakes and the helicopter can require repair.

If you’ve crashed your MASH helicopter and need new rotor blades, grips, or even a new flybar then you’re grounded until new parts arrive. Enter the crash kit – a carefully chosen assortment of the most commonly needed replacement parts, all in one convenient and discounted package. If you keep one of these on hand, you won’t have to stop flying and wait for new parts in the mail again. The MASH helicopter was designed to be user-serviceable just like larger fuel and electric helis. If you’ve got a broken part, then it’s almost certain that it can be replaced without anything more complicated then a screwdriver. This guide will walk you through replacing the most common parts:

Replacing Main Rotor Blades

The main rotor blades can become cracked in a severe crash and pieces can break off. While it’s completely possible to fix small cracks and dings with some medium CA glue and accelerator, this can negatively affect blade balance and make the helicopter vibrate. It’s easier and faster to replace the old blade so here’s how to do it:

  1. Get a small Phillips head screwdriver and unscrew the single aluminum screw at the root of the damaged blade. The blade will now be free, and you can remove and dispose of it. Damaged blades can be sharp, so be careful not to cut yourself.
  2. All the top rotor blades come with a white warning label on their upper surface. Choose from the upper and lower rotor blades as needed so that the rotors look like this when viewed from the front. As viewed from the front, the right top rotor blade should curve upwards and the bottom right rotor blade should curve downwards. This picture shows the correct blade orientation.
  3. Install the replacement blade and tighten the screw just enough so that the blade swings freely when you tilt the helicopter, but is secure enough that it won’t fly off. This has to be done by feel – it’s not critical that the screw is perfectly adjusted, but the blade should feel secure and move freely.
  4. Repeat this for any other rotor blades that need replaced. It’s helpful to install them one at a time to keep track of the orientation.

Replacing the Blade Grips

The blade grips / holders are black clevis like objects which clamp down on the root of each blade and hold it to the main shaft. If one of these becomes damaged, use this procedure to replace it:

  1. Remove the both of the rotor blades that the blade grips are holding by following the instructions above.
  2. Lay the helicopter on its side and observe the two screws that hold the blade grips together and on the main shaft. This picture shows one screw removed, viewed from the bottom of the helicopter.
  3. Unscrew the blade grips and keep the screws in a safe place where they can’t roll away.
  4. Replace the broken blade grip and install the screws.

Replacing Ball Linkages:

Ball linkages connect the RC helicopter’s servos to the swashplate and flybar. It’s fairly unlikely that these will get broken in a crash, but if they do, here’s how to replace them:

  1. Snap off the damaged ball link using your fingers or a screwdriver.
  2. Find the replacement link that matches the one you took off and press it on to the spherical plastic nubs where the broken link connected. This picture shows a partially disconnected ball linkage on the flybar:

What makes the MASH helicopter unique is its ability to be completely disassembled and user serviceable. You don’t usually find this on helicopters in the 100 to 200 dollar price range, which are usually meant to be flown and then discarded when they break. Want to learn more about the MASH helicopter, or get one to fly around your living room? RCtoys sells them at a great price. If you just want the crashkit, RCtoys.com has that as well.

The swashplate isn’t included in the crashkit, because it rarely breaks.  If you need a replacement swashplate, you can get one online for a low cost.

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Posted in Coaxial RC Helicopter Design, Electric RC Helicopter Power Systems

All About the EF MASH Rescue Chopper Indoor RTF RC Electric Helicopter 2.4 GHz

EF MASH Rescue Chopper 

The helicopter became a prominent military asset during the Korean conflict of the early 1950s. The United States Army started using helicopters for medical evacuation in order to increase the survival rate of critically wounded soldiers. Helicopters were used in conjunction with forward mobile army surgical hospitals (MASH units).

When many people think of helicopters being used for medical evacuation in Korea the Bell H13 Sioux (designated the Bell-47 by the US Army) is the one that most comes to mind. Most people know this helicopter as the MASH helicopter because of its important role in the TV series MASH. EF has come out with an amazing flying replica of this famous MASH helicopter.

Included with the EF MASH Rescue Chopper

The EF MASH Rescue Chopper includes everything you need to fly, right out of the box. This is what is included:

  • 2.4 GHz 4 Channel Transmitter
  • RTF MASH Rescue Chopper
  • 7.4v 800 mAh LiPo Battery for the Helicopter
  • Two 7.6 gram Micro Servos
  • 3 in 1 2.4GHz receiver

Main Features of the EF MASH Rescue Chopper Indoor RTF RC Electric Helicopter

The EF MASH Rescue Chopper is easy and fun to fly while still maintaining the stand off scale looks of the helicopters used in the TV series MASH. The dual rotors (co-axial) make this micro electric helicopter easy to fly and perfect for the beginner RC helicopter pilot. Experienced helicopter pilots can work on there skills to make the flight look as realistic as possible.

It is very quick to get the EF MASH Rescue Chopper ready to fly. All you will need is a screw driver and 8 AA batteries. The MASH Rescue Chopper Indoor RC electric helicopter does require a small amount of assembly. Before you begin the assembly start charging the LiPo battery. This way you will be flying the helicopter in no time.

This mini indoor electric helicopter has a coaxial rotor design which provides great stability, and eliminates the need for a separate tail rotor to control torque induced yaw (rotation around the main rotor axis). Coaxial RC electric helicopters are great for flying indoors, because they are both stable and offer precision control.

A 3.7 volt LiPo battery powers the EF MASH Rescue Chopper for a flight time of eight to ten minutes. The battery is charged in the controlled and takes about 30 minutes to charge. To get maximum enjoyment out of your helicopter it is a good idea to buy a spare battery for it. This way you can be charging a battery while flying and cut down your down time.

If you do happen to have a mishap and crash the MASH Rescue Chopper you will be amazed at how incredibly resilient it is. However things do and can break, but not to worry as a full line of inexpensive replacement parts are also offered for this helicopter.

In summary if you want to try some basic scale electric RC Helicopter flying you should look into buying the EF MASH Rescue Helicopter.

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Posted in Coaxial RC Helicopter Design, Electric RC Helicopter Power Systems, Electric RC Helicopters - Coaxial Helis, Latest RC Helicopter News

All About the EVO Flight Mini Stinger Indoor RTF RC Electric Helicopter 2.4GHz

The Evo Flight Mini Stinger can be described as the sister RC Helicopter to the Blade MCX. The Evo Flight Mini Stinger shares many of the amazing features that made the Blade MCX unique from other indoor micro RC Helicopters.

Included with the EVO Flight Mini Stinger

Mini Stinger

The EVO Flight Mini Stinger includes everything you need to fly, right out of the box. Here’s what is included:

  • The EVO Flight Mini Stinger Micro RC Helicopter
  • A 2.4 GHz, DSM-2 Spread Spectrum Transmitter (requires 4AA Batteries)
  • A Portable Lipo Charger built into the transmitter
  • 1 cell 3.7V 110mAh Li-Po Battery

The Evo Flight Mini Stinger is great for beginner and experienced pilots, because you do not have to buy any additional parts. You can use this helicopter to get experience and practice your orientation indoors when you cannot fly outdoors because of the weather.

Main Features of the Evo Flight Mini Stinger Indoor RTF RC Electric Helicopter

Like the Blade MCX the Evo Flight Mini Stinger has a proportional four channel radio. Four channel control means that pilots can fly the helicopter with four dimensions of freedom. The Evo Flight Mini Stinger can fly up/down, rotate left/right, pitch forwards/backwards, and bank left/right. With a four channel radio you can precisely control the Evo Flight Mini Stingers’ movement through all three dimensions. With a rotor size of 188mm (7.4”) and a length of 213mm (8.4”) this helicopter can easily fit in the palm of your hand.

The coaxial rotor design of the EVO Flight Mini Stinger provides this helicopter with great stability, and eliminates the need for a separate tail rotor to control yaw (rotation about the main rotor axis). The main rotors spin in opposite directions, canceling out rotor torque caused by their rotation. Coaxial RC helicopter are great for flying indoors, because of their stability and the precision control provided.

The Evo Flight Mini Stinger uses a tiny 1 cell lithium polymer battery for power. Unlike most micro RC helicopters, the battery is removable and interchangeable. Each cell provides 3.7 volts of power with a capacity of 110 mAh (Milli ampere hours). You charge the battery using the included transmitter, which runs off four “AA” alkaline batteries. A typical charge takes about 30 minutes and provides an average flight time of 6 to 8 minutes. Because the battery is interchangeable, we recommend that you purchase an extra so that you can use one while the other is charging.

Weighing only 1 ounce, the Evo Flight Mini Stinger is virtually crash proof. A sudden drop from a few feet above the ground won’t damage it, and in most cases minor collisions with walls are not a problem. Although it is not indestructible, the Evo Flights durability makes it an ideal present for anyone over 12 years of age.
If you want to get into the exciting world of RC helicopters, the Evo Flight Mini Stinger makes a great starting place. It will show you all the basics of RC helicopter flight, and can be used as a starting place to more advanced models. If you’re already an experienced RC helicopter pilot, you’ll like the Mini Stingers control and stability. Watch our site for tutorials on the Mini Stinger, including a how to for installing replacement parts.

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Posted in 2.4GHz Digital Radio Transmitters for RC Helicopters, Coaxial RC Helicopter Design, Electric RC Helicopters - Coaxial Helis, Latest RC Helicopter News, Learn to Fly RC Helicopters

New Draganfyer X4 RC Helicopter Videos

Draganfly Innovations released their new Draganflyer X4 earlier this summer. The Draganflyer X4 RC Helicopter is an ultra portable aerial video and aerial photography platform. As seen in these videos:

Draganflyer X4 RC Helicopter Man Portable

This video depicts the Draganflyer X4 RC Helicopter being quickly set up and flown from its case which has an optional detectable back pack harness.




Draganflyer X4 RC Helicopter Soft Pack with Optional Back Pack Harness

In this video we see the Draganflyer X4 being transported in its soft pack with back pack harness on a man riding a mountain bike. This truly shows has easy it is to pack the Draganflyer X4 into a remote location.




Draganflyer X4 RC Helicopter with Panasonic FX-580 12.1 Mega Pixel Digital Camera

One of the camera payloads the Draganflyer X4 RC Helicopter can carry is the Panasonic FX-580 12.1 Mega Pixel Digital Still camera. This video gives a good description of how this camera integrates with in the Draganflyer X4 System.




Draganflyer X4 RC Helicopter Portable Live Streaming Video

This video gives us a picture in picture of what the camera sees as the rc helicopter is flying. The video is transmitted live while recording to the on board digital video camera.




Draganflyer X4 RC Helicopter – Micro Camera and Digital Video Recorder Payload

Another camera payload option for the Draganflyer X4 is a micro video board camera with a on board digital video recorder. This video gives you the details of the Micro Video board camera.




 
 

The Draganflyer X4 RC Helicopter, as demonstrated by these videos, is a very versitile and portable UAV aerial video and aerial photography platform. We here at RCHelicopter.com will be looking for new videos from Draganfly Innovations.

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Posted in Latest RC Helicopter News, Quad-Rotor RC Helicopter Design, RC Helicopter Commercial Aerial Photography Application, RC Helicopter Commercial Aerial Videography Application, RC Helicopter Commercial Inspection Application, RC Helicopter Military and Police Application, RC Helicopter Unmanned Drones and UAVs

Megatech Micro Flyer – The Perfect RC Helicopter For Kids

The Megatech Micro Flyer is a two channel RC helicopter built to extremely small dimensions. A durable plastic body and stable coaxial design make it the perfect RC helicopter for kids.

The Megatech Micro Flyer includes a charger that is built right into the transmitter. This lets you charge the RC helicopter on the field, maximizing flying time.

A simple to use transmitter operates on the radio band, not the line of sight infra red frequency that is often used with micro helicopters. The transmitter also uses buttons instead of sticks, requiring less skill to operate precisely.

The Megatech Micro Flyer uses a coaxial design, giving it good flight stability. A separate tail rotor is used to control yaw.

The Megatech Micro Flyer is a great, easy to fly electric RC helicopter for beginners. You can read more about it on it’s website

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Posted in Coaxial RC Helicopter Design, Latest RC Helicopter News

How to Modify A Micro Mosquito RC Helicopter

The Bladerunner Micro Mosquito is a small electric RC helicopter. It flies very well out of the box, but several users have come up with modifications which improve it’s appearance and flight characteristics. This article lists the different possible modifications, and explains how to do each one.

Increase The Speed Of The RC Helicopter

One of the most popular modifications involves increasing the horizontal speed of Micro Mosquito. This can be done in one of two ways:

  1. Shift the center of gravity forward - If the balance point of the Micro Mosquito is moved forward, then it will move forward faster. You can do this by adding small weights under the Micro Mosquito’s main rotors. This will result in increased forward speed, but decreased backwards speed.
  2. Get a different tail rotor – Standard mini heli tail rotors will fit the Micro Mosquito’s tail motor shaft. Mini heli tail rotors move air more efficiently in one direction than another, so using them on the Micro Mosquito will let you control the pitch in one direction more effectively. Normally, it is better to have more control in the forward (nose down) direction of travel.

Decrease The Weight Of The RC Helicopter

There are a number of ways that you can decrease the Micro Mosquitos weight. Decreasing the weight will provide longer flight times and more performance.

  1. Remove the rubber “feet” – You can do this by pulling them off of the Micro Mosquito’s legs.
  2. Remove part of the plastic shell – You can unscrew and remove the bottom part of the Micro Mosquito’s body, which will dramatically reduce the weight of the RC helicopter.

Optimize The Radio Range Of The RC Helicopter

The range of the radio transmitter is fine for flying inside a house, but more range is required for flying in a gym or other open area. This is one of the more technical mods, so proceed at your own risk. I have not actually tried this, but this thread on RCGroups.com says it should work. Follow this procedure carefully:

  1. Open the transmitter case - Do this by removing the 5 screws found on the back of the transmitter case.
  2. Remove the circuit board – Remove the three screws holding the circuit board down, and gently remove it.
  3. Remove capacitor C15 – Flip the circuit board over, and look for a capacitor marked C15. It should be on the left side of the circuit board. De solder this capacitor and remove it carefully. There should be no contact between the solder pads where the capacitor used to be.
  4. Re install the circuit board – Put the circuit board back on and replace the three screws that you took off earlier.
  5. Close up the case – Put the back of the transmitter case back on and screw it in place with the five screws you removed earlier.

Unfortunately, we know very little about this mod or if / why it works. Any comments on this matter would be greatly appreciated.

Remove the Throttle Spring From The Transmitter

Normal radio transmitters do not have a spring restrained throttle. Pilots of larger RC helicopters appreciate the control that not having a throttle spring provides, so here is how you remove it:

  1. Open the transmitter case - Do this by removing the 5 screws found on the back of the transmitter case.
  2. Find the spring – It should be behind the throttle stick.
  3. Remove one of the two screws the spring is attached to – And then put the screw back. You can leave the spring in the case or remove it entirely, it doesn’t really matter.
  4. Reassemble the case - Put the transmitter back together using the 5 screws that you removed earlier.

Now the throttle lever will stay where you last left it, so that the Micro Mosquito can hover without constant control input.

Improve Flight Stability and Control

Here are some tips to improve how the Micro Mosquito flies.

  1. Tilt the tail rotor – The micro mosquito tends to spin when the throttle is accelerated, sometimes leading to a hard landing. You can fix this problem by twisting the tail boom about 5 degrees to the left (when viewed from behind). Twisting the tail boom is easier if you heat it up slightly beforehand.
  2. Add weight to the main rotors - The inertia of the main rotors causes them to self stabilize when spinning. You can increase this tendency by coiling a small amount of very thin wire over the outer rotor wire. Do this twice on opposite sides of one main rotor, and then repeat for the other main rotor. As long as you don’t add too much weight this should improve the RC helicopter’s stability.

Color!

Here are some tips and tricks you can use to personalize your Micro Mosquito:

  • Remove the case and spray paint it – take all of the radio components, batteries, and motors out of the Micro Mosquito’s body and spray paint it any color you like.
  • Fuel tubing effects – Get a piece of clear fuel tubing from your local hobby store. Then push one end over one of the Micro Mosquito’s green LED eyes. Bend the piece of fuel tubing over, and push it on to the other LED. When the helicopter is turned on, the light should produce a really cool neon tube effect. This is also a great way to move the center of gravity forward, so the helicopter goes faster.
  • Insect antenna – Use stiff wire and make a pair of insect antenna. You can glue these to the Micro Mosquito’s body to create an insect appearance. Be sure to keep them away from the main rotors. Just like the fuel tube mod, this will move the center of gravity forward and cause the helicopter to move faster.

Spare Parts / Experiment Pack

Need parts for your Micro Mosquito? RCtoys.com has a great selection and a special package of parts, chosen for easy modification. You can build all sorts of RC vehicles using the micro mosquito and it’s components. Get out your tools and let your imagination soar!

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Posted in Electric RC Helicopters - Coaxial Helis, Latest RC Helicopter News, RC Helicopter Construction and Design

How Cyclic and Collective Pitch Works on RC Helicopters

Cyclic collective pitch is used by RC helicopters to control flight. In a previous article, fixed pitch helicopters were explained. Fixed pitch helicopters change their direction and altitude by changing the rate at which their rotors spin, and sometimes by using a tail rotor. Finer control can be achieved by changing the pitch of the rotor blades. By changing the pitch of the blades, the airflow from them can be changed, moving the helicopter in different directions. Changing the pitch of the blades is more efficient than just increasing the speed of the blades. In this article, the mechanics of variable pitch helicopters will be explained.

How The Swashplate Works on RC Helicopters

Swashplate AnimationIn order for the rotor blades of an RC helicopter to change pitch, there must be a way to transform the linear motion of a servo arm into the rotating motion required by the rotor blades; this is accomplished by using a swashplate. The swashplate is a mechanical device, consisting of two plates mounted to the main rotor shaft. One of these plates is attached to the servo controls and the helicopter body, and the other rotates with the helicopter rotors. As can be seen in the picture, the swashplate transforms the motion of the servo arms into motion of the upper plate. Each rotor is connected to the upper disk of the swashplate, and so they will move as the bottom disk moves. The horizontal rods visible in the picture represent where the servo arms would connect, the number of rods included depends upon the individual helicopter. Every RC helicopter that can change the pitch of its rotor blades will have a swashplate attached to its main axial. There are many different implementations of swashplates, but each follows the same basic design shown in the image. In a conventional RC helicopter, two servos are used to control the swashplate. One servo is used to control the horizontal motion (bank) and the other is used to control the forward and aft motion (pitch).

RC Helicopter Collective Pitch – Climbing and Descending

When a RC helicopter needs to climb or descend, it uses collective pitch. When the command is given for the helicopter to climb, the servos push the entire swashplate upwards. This has the effect of simultaneously increasing the pitch of all the rotor blades. When the pitch is increased, the rotors grab more air as they move, and so lift produced is increased. This increase in lift occurs evenly, so the helicopter does not turn. When the helicopter needs to descend, the swashplate is lowered in the same way. This will decrease the amount of lift produced from the rotor blades.

RC Helicopter Cyclic Pitch – Attitude Control

Changing the bank and pitch of the helicopter requires the swashplate to tilt. This is accomplished by tilting the lower disk of the swashplate. When the lower disk is tilted, the upper disk will also tilt, while it is spinning. The main rotors, which are attached to the upper swashplate will also tilt. In order for this to happen however, each rotor must be given time to “fly up”, or “fly down” to the location where it needs to be. This is accomplished by using pitch links, which provide each rotor with the information of where it needs to go, before it has to be there. The net effect is that the blades move cyclically, and tilt the motion of each rotor in one direction. The swashplate can be tilted in any direction, so the helicopter can change its pitch and bank in proportion to the commands given by the transmitter.

RC Helicopter Cyclic Collective Pitch Mixing (CCPM)

Model RC helicopters can use more than two servos in combination to control the motion of the swashplate. Software running on the rc transmitter (radio) tells each servo how much to move to achieve the desired motion of the RC helicopter. Each linkage to a servo is represented by a silver rod in the above picture. All of these rods are placed equidistant from each other. A swashplate mix refers to the number of linkages attached. For example: a two linkage swashplate would be controlled by two servo rods, placed 180 degrees apart from each other. A three linkage swashplate would use a 120 degree swash plate mix. The swash plate in the picture above has 6 control rods, and so it would use a 60 degree swash plate mix. Most RC helicopters will use a swashplate with between two or four control rods. The largest RC Helicopters use 4 control rods, because of the extra strength they give the swashplate mechanism.

In Summary

  • Every RC Helicopter that can change the pitch of its blades has a swashplate.
  • The swashplate consists of two disks, one which spins and one that does not.
  • The bottom swashplate does not spin, and is connected to the servo control rods.
  • The swashplate consists of two disks, one which moves and one that does not.
  • To rise or descend, the rotor blades move collectively
  • Pitch and bank require the swashplate to move cyclically.
  • Pitch links control the position of each blade.
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Posted in Conventional RC Helicopter Design

Introduction to Coaxial RC Helicopters

Chinook C-47 Dual Rotor HelicopterThere are different ways that coaxial RC helicopters can be designed. The main rotors of a RC helicopter can be mounted in two ways. In conventional helicopters, a main rotor is mounted on the top of the fuselage, and a smaller tail rotor is added to the end of the fuselage. The tail rotor is used to control the yaw, and every other aspect of flight is controlled by changing the pitch of the main rotor blades. It’s also necessary to have a tail rotor so that the torque from the main rotors can be canceled out. Torque is created when the main rotor spins. For every action, there is an equal and opposite reaction, so the nose turns in the opposite direction.

Coaxial Helicopters – How Do They Work

Besides using the tail rotor to control the yaw, two main rotors can be mounted on the helicopter, and spun at different rates. The difference in thrust causes the helicopters nose to turn. This duel rotor design is used in several full scale helicopters. The CH-47 Chinook is a good example of this duel rotor design, and is frequently used as a military transport helicopter because of its large lifting capacity. RC Helis use the same principle, but most of the time each rotor is mounted on the same axial, hence the term “coaxial”.

Twin rotors that spin in opposite directions

The rotors of a coaxial helicopter need to spin in opposite directions to cancel out the gyroscopic force. On some helicopters, both rotors are mounted on top of each other The main axial of a coaxial helicopter is actually two separate axils. One axial is mounted inside the other. Each sub axial is connected to a gear at the base of the main shaft, and each gear is connected to an electric motor. These two motors operate independently of each other, so the speed of each rotor can be changed.

Since the rotors need to spin in different directions, the top and bottom rotor blades are curved in different directions. This is because each rotor needs to be traveling into the air flow in order to work. The bottom rotor spins in a clockwise direction, and the top rotor spins in a counterclockwise direction.

Two Channel Coaxial RC Helis

It is possible to build a coaxial helicopter so that it only needs two main rotors, and eliminate the tail rotor entirely. Tilting the main rotors forward slightly, results in a constant forward movement. These helicopters are great for beginners due to their simple controls.

Three Channel Coaxial RC Helis

In some coaxial helicopters, a tail rotor is still added. The tail rotor is oriented in the same direction as the main rotors. The forward and reverse rate of the helicopter can be changed, because this system allows pitch control. You can fly forwards, backwards and also hover with this kind of helicopter.

Four Channel Coaxial RC Helis

Esky Lama V4 Coaxial RC HelicopterEven though the coaxial design is most frequently used in small, fixed pitch RC helicopters, it can also be used for models with cyclic collective pitch. The only difference between these models and the conventional designs is their lack of a tail rotor. As with the models above, yaw is controlled by changing the rate at which each rotor spins, but the rotors can change their pitch. This allows the helicopter all four degrees of freedom: pitch, bank, throttle, and yaw. The Esky Lama V4 is good example of the four channel coaxial design.

How The Coaxial Design Benefits RC Helicopters

  • Yaw can be controlled by changing the speed of the main rotors, so the pitch can be controlled with the tail rotor.
  • The main rotors spin in opposite directions, which gives the helicopter stability.
  • Coaxial RC helicopters are a good way to learn how to fly, because they are very stable.
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