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Posts Tagged ‘wind’

Getting Started on RC Helicopters – Part 5 (Gyros Explained)

So you’re new to radio controlled helicopters and you start to hear about gyros. Wondering what they are, what are they used for or even how they should be used? This post will clarify everything about gyros and i hope in the end you will have a better and clear idea about them.

The purpose of the gyro is to stabilize the tail. Without it, the model would be almost unflyable. Early gyros had a motor and two flywheels inside and at the time worked quite well but they are no match compared to more recent piezo gyros, which have no motor, but use an electronic sensor instead.

Piezo Gyros

Modern piezo gyros have never been so good and are no longer an expensive alternative but an essential part of the radio system. Modern peizo gyros can cost anything from $50 to $400. So how much should you spend and which one should you buy?

Well at the lower end of the scale, the gyro will be single rate, adjusted on the gyro itself and will not have pilot authority. At the top of the range, it will probably be dual rate in both normal and heading lock mode (sometimes called heading hold or AVCS), selectable from the transmitter, and it will also have full pilot authority.

Modern piezo gyros have a very fast response and will need a servo that can keep up with the gyro output. Servo speed is measured by the number of seconds it takes for the servo to turn 60 degrees, so a digital servo with a speed of 0.12s/60 to 0.08s/60 is the ideal but you will have to pay around $70 to $150 for it.

Gyro Gain

The best way to adjust gyro gain is to turn it up until the tail wags in forward flight and then turn it down a little. You should be able to get near 100% gain. If you can’t, then try changing the length of the rudder servo arm. There is no point in spending serious money on a good gyro and then only using 50% gain.

Pilot Authority

On a standard gyro, when you input a rudder command the gyro will try to correct the tail back to the centre. The higher the gain on the gyro, the less tail authority you will have. With pilot authority, the gyro gain decreases as you input commands so you can have 100% gyro gain and still have full tail authority.

Heading Lock

With the gyro in normal mode, the tail will weathercock to some extent so when flying circuits or hovering in to wind the tail will tend to follow the line of the model. In heading lock mode, the tail stays wherever you put it, so it is quite easy to fly the model sideways or backwards at speed without losing the tail position. The only downside to heading lock mode is that you have to steer the tail all the time as it will not naturally follow the model. And if you enter a maneuver, say a loop, with the tail offline it will stay offline throughout the maneuver. If you are not sure which mode the gyro is in, with the radio on and without the engine going, move the rudder control fully to one side: if heading lock is selected, the servo will stay at one end until you move the stick back to the other side.

Mixing Makes

I have used Futaba, JR, and CSM gyros on JR radio systems with no problems at all. Anyhow, i advise you to use a matching rudder servo in the case of JR or Futaba, as they were designed to work with their own servo.

iPhone Wind Meter

I have just found this new iPhone application that detects the wind speed using the iPhone microphone. It’s called “*Wind Meter*”. It’s been getting very good reviews and i  thought it might well be a useful tool for us. I gave it a try yesterday and to my surprise it works quite well! According to recorded tests against a real wind meter tool, this iPhone application has an error around 3% at most, which is quite acceptable for radio control usage.

iPhone Wind Meter
iPhone Wind Meter

A complete description and video of the application in use can be found at http://www.windapp.com. “Wind Meter” can be obtained at Apple iTunes App Store by searching for “Wind Meter”. This app is designed primarily for 3G/3GS iPhones, but it will also run well on the new iPhone 4G.

The concept for “Wind Meter” came from a group of Silicon Valley entrepreneurs that happen to love wind sports. The idea for converting the decibel reading from the wind “noise” on the mic to a velocity reading almost seemed obvious after-the-fact, and they were a little surprised to be the first to release something like this on the market. After a considerable amount of R&D, Wind Meter is a really fun gadget that actually works. If you have an iPhone, give it a try!

Aerobatic Maneuvers – Part 2 (Loop)

Here i am again to talk about more aerobatic maneuvers. This time, let’s focus on the loop.

Loop
Loop

This is one of the most basic maneuvers, but not easy to fly well. It has to be perfectly round, entry and exit have to be at the same altitude. The difficulty in flying this manuever well is in correcting for effects of wind drift. In competition, it helps if you don’t have to fly first, so you can watch what your competitors are doing and judge the wind drift that you have to take into account.

The maneuver starts with a pull up of about 3-4 g. Once past the vertical, the back pressure on the elevator is slowly relaxed to float over to top of the loop to keep it round. Past the top, the back pressure is slowly increased again throughout the back part till horizontal flight. The plane has to stay in one plane with the wings orthogonal to the flight path. Rudder is used to maintain the plane of the figure and ailerons are used to maintain the orientation of the wings.