25 Sep, 2013 | News

Ask An Air Hogs Engineer

Last week we asked our Facebook fans to post questions about RC technology for our Air Hogs engineers. There we’re a ton of great questions so we pried one of our engineers away from designing the next Air Hogs to answer a few of the best ones!

Question #1:  How does a brushless motor work? - Paritosh

Air Hogs Engineer Ian:

Brushless motors work by magnetizing wire coils and causing strong magnets inside the motor to move.

By varying the current running through the wire coils at precise times it is possible to push the magnets around in circles.

The largest difference between a brushless motor and a standard brushed motor (most common type) is that it requires a controller to function. The controller reads signals from the motor to determine how fast it is spinning allowing it to charge and discharge the motor coils at the right times to make it run at the right speed.

Brushless motors are more efficient, more powerful, but much more expensive. They are only really used in high-grade hobby RC vehicles.

Brushless Motor
Brushless Motor

Question #2:  How does a gyro work? - Matt

Air Hogs Engineer Ian:

Gyro sensors are used to detect angular velocity, which means they can detect how fast something is spinning. Gyros sense changes compared to a reference speed or position. For a gyro to function properly it is critical that it is allowed to calibrate in a stable position to give it reference.

That is why you need to put your Helix X4 Stunt on a flat surface for a few seconds after switching it on. It allows the gyro inside to gain a reference point so it can keep the quad steady and level.

There are many different types of gyros but the two most common are mechanical and MEMS (vibrating) types.

  • Mechanical gyros work by spinning a heavy wheel very fast.  The force causes the wheel to stay in the same position (like a bike tire). Mechanical gyros were once used on ships to help them maintain their direction and can also be used to help keep an object upright by the force they generate (like a spinning top).

Mechanical Gyro
Mechanical Gyro

  • MEMS gyros have become very common now and are what are used in cell phones, gaming systems, and RC products.They contain a small vibrating crystal attached to a floating arm which is used to detect changes in rotation. Their small size makes them very convenient for engineers to use and, unlike mechanical gyros, can be used to sense changes in up to three axes.

Air Hogs uses a three axis MEMS gyro in the Helix X4 Stunt quad.

Fan Question #3: What is Scale Speed? - Geoff

Air Hogs Engineer Ian: 

Scale speed is a measure of how fast a RC vehicle goes in relation to a full sized vehicle - how fast the RC vehicle would travel if you blew it up to full size.

To calculate scale speed we measure the speed of the vehicle (usually by timing how long it takes to move between two points) and multiply by the inverse of the vehicle scale.  

For example, if a RC car is 1/24th the size of a full sized car we would multiply its speed by 24.  If that RC car can travel 10 MPH, it would have a scale speed of 240 MPH.

If you have any questions you want us to ask our engineers for you, post them on the Air Hogs Facebook page!

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