UNDERSTANDING MINI RC TOY HELICOPTERS

OK - why is it that mini RC toy helicopters haven’t been around for years and why am I so taken with these little helicopters.

Let’s go back in time say about 30 years. I was about 8 years old, and got something called a VertiBird toy helicopter for Christmas.

If any of you remember these things you are as old as I am, and you also know it was one of the coolest toys you probably ever had.

For the younger crowd out there – a VertiBird was a small plastic helicopter (about the same size as a Havoc heli) and was attached to a meter long thin rod. This rod was attached to a rotating base and the helicopter would fly in circles around the base.

You could control the throttle and pitch angles of the helicopter so it could hover, fly forwards and backwards. It even had a little hook on the bottom to pick up small items off the ground.

Sure it was tethered to this rod and could only fly in circles, but 30 years ago, it was awesome. I remember rushing home from school with friends to play with this thing.

As we got older we started lighting it on fire and of course, that was the end of my VertiBird. Gone but not forgotten... this humble little toy helicopter is what sparked my interest in rotary aircraft that continues to this day.

Sorry for the long winded toy helicopter history lesson, but now you know why I am so thrilled with the new generation mini RC helicopters. When I first started flying the Havoc helicopter, I felt like I was 8 years old again and the days of the VertiBird seemed like yesterday.

The symbolism of the Havoc heli being the phoenix born from the flaming VertiBird is a bit obvious – but so true. The new technology now allows kids and us kids at heart adults, to fly all over the house or office harassing siblings or co-workers... finally breaking the bonds of the tethered VertiBird.


ELECTRONICS

There are two technological reasons the new generation mini RC helicopters didn’t show up to a few years ago. The biggest reason being the invention of extremely light and powerful Lithium Polymer batteries. The other reason is of course mass produced surface mount electronics. Now you know why there were no Havocs hovering in living rooms 15 years ago.


ROTOR DESIGN

The first thing you will notice on the Havoc and like helicopters is the Rotor Head. Yes it is a version of a self correcting Hiller Rotor Head . There is a weighted fly bar rotor on the top and it is connected to the main rotor blade by two very tiny push rods.

Any tilting of the helicopter will produce an increase and decrease in pitch angle to the main rotor blades to self correct the tilting of the helicopter. Thus the little heli is very stable. You will also notice this little upper fly bar rotor is situated about 20 degrees in front (clockwise) of the main rotor.

This is to compensate for the small amount of Gyroscopic Precession that is produced by the clockwise rotating main rotor blade. Unlike larger hobby grade RC helicopters, the mini RC helicopters have a very low rotor mass. This is why the gyroscopic precession is only 20 degrees in front of rotor rotation instead of 90 degrees typical on larger helis.

The rotor speed is of course controllable from the infra-red (IR) controller to allow you to gain altitude, hover, and descend. There is a detailed explanation of how this happens in the Helicopter Theory And Controls section under the topic of Lift Control .


BODY CONSTRUCTION

The next thing you will notice is that the body is made from polypropylene foam. I have heard all kinds remarks about this – generally not positive. Everything from "cheap" to "Nerf like".

From an engineering stand point, flexible polypropylene is brilliant.

  • It is super light weight.
  • It is cost effective- ok cheap (not the main reason it is used however)
  • It can be easily shaped to create a decent looking helicopter.
  • The most important feature... it is the perfect shock absorber. This not only protects the small motor, gear, and micro electronics buried inside the mini heli - it protects the battery.

    You can fly these mini RC helis into walls, windows, and house plants with out any damage. I even flew mine (actually got sucked) into the ceiling fan. It got launched clear across the living room but was still flying ready to do battle with that rotten ceiling fan again & again.


    TAIL ROTOR

    Onto the little tail rotor... I didn’t think they could make electric motors that small. Take a look at this tiny tail rotor motor; it is no more than 4mm in diameter. I know... small things amuse small minds.

    At any rate, the tail rotor on mini RC toy helicopters has the exact same function as on hobby grade or real helicopters – to counteract the Reactive Torque produced by the main rotor.

    The speed of the tail rotor motor on our mini RC toy helicopter is controlled by the IR controller to vary the thrust produced by the tail rotor and allows yaw control (right/left) rotation of the helicopter.


    LIMITATIONS

    There are of course limitations with these little RC toy Helicopters, specifically they don’t have Cyclic Control This means you can’t hover in one spot, fly side ways, or fly backwards.

    The Havoc helicopter is designed with the center of gravity being a little bit forward of the rotor mast. This makes the helicopter fly in a forward direction. See my Tips And Tricks section to alter this.

    These mini toy RC helicopters don't have a gyro . This makes for very vague and sensitive tail rotor control. Any moderate to large increase or decrease in rotor speed will cause a corresponding torque change and around the heli spins until you can get things back under control.

    The other small limitation is you can’t fly mini RC toy Helicopters outside. This is because the controller uses infra-red(IR) control instead of radio-control(RC). Infra-red is simply a region of light waves that the human eye can not detect.

    IR light is produced on the controller by several IR light emitting diodes (LED’s). This is to keep the cost and more importantly the helicopter weight down. So really we should call this method of control IRC(infra-red-control).

    No mater, what is important to understand is the IR controller won’t work outside. The IR LED’s can’t produce enough light to compete with natural IR light from the sun.

    Even if you fly after dark, you will still loose control of your mini heli outside because the IR controller is designed to scatter the IR signals and bounce them off the walls and ceiling inside a room.


    FUTURE DEVELOPMENTS

    I bet you a Havoc there are engineers working on a cyclic version with gyro correction as I write this. To introduce one under $100.00 will be the big hurdle, but considering the old VertiBird from the 70's cost as much as the Havoc does today... who knows what exciting and fun RC toy helicopters are around the corner.