Know How... 168

Pratt & Whitney's new Super Engine

• Modern aircraft are all about the turbofan engine
• The Turbofan combines massive amounts of power, with decent efficiency and impressive reliability.
• Even the non-exotics are amazing works of engineering

Here's how a traditional turbofan works:

• A Jet engine compresses air, adds fuel, burns it, then is thrusted forward by the expansion of exhaust gasses
• A "Fan" moves huge amounts of air, thrusting itself forward (Think of the props on a Quadcopter)
• A Turbofan combines the two: a HUGE fan in front of, and drive by a jet engine

In a modern high-bypass turbofan you have:

1. The Fan
2. The low-pressure compressor
3. The High pressure compressor
4. The Combustion chamber
5. High pressure turbine
6. Low pressure turbine

Here's the key

• The low pressure turbine is connected by a shaft to the low pressure compressor and fan
• The high pressure turbine is connected to the high-pressure compressor
  • So, as the gasses and burned and expanded, they provide the power to the fan and compressors that allow for the gasses to be burned and expanded.

This is a good system... but the folks at Pratt and Whitney just made it obsolete!

The Pratt & Whitney "PurePower" Geared Turbofan

• They burn 16% less fuel for the same thrust
• They put out less NOX for the same thrust
• The create 75% less noise while on the ground
• It cost 30 years and $10 billion to make them work

Why is it so much better?

• Let's talk about propellors.
  • Small props that spin quickly, vs large props that spin slowly
  • Large is more efficient, and less noisy
    • But we wouldn't use larger fans on Turbofans because the speeds as which you needed to spin the shaft for the compressors was spinning too fast for the ideal-sized fan.
    • So... P&W added a gear box (It's 20 inches in diameter and weighs 250lbs)

They used a orbital gear design to step down the speed of the low-pressure turbine/compressor shaft.

• This allows the fan to spin much more slowly, but with far more torque
• Slower speeds with more torque means they can use a more aggressive fan that moves more air at lower speeds.
  • While a traditional turbofan might have a 5:1 bypass... PurePower does 12:1

So... more efficient, more thorough burn (less pollutants), and MUCH quieter on the ground.

WinDroid & Google History

AMIDuOS!

• Created by AMI - "American Megatrends - The company that so many of us know from their BIOS days"
• They were founded in 1985 by Pat Sarma and S. Shankar (who will be on Triangulation in the future)
• Their first customer was "PC's Limited" which became "Dell Computers"

But this is DuOS...

• Unlike "Bluestacks" which is an Android App Emulator, DuOS is full-Android in either a VM or a Container
• It gives FULL access to all the major peripherals (this was a major problem with emulators)
  • Keyboard, Mouse, touchscreen, microphone, ambient light sensor, accelerometers, compass, orientation, etc.
  • It also supposed variable screen sizes.

Notes:

1.  There are two versions: AMIDuOS 1.1 (Running Android Jellybean) and AMIDuOS 2.0 (Running Android Lollipop)
2. Jellybean will cost you $10 // Lollipop will cost $15
3. Once you install, you WILL need to install Google Apps and Services

Let's talk about what Google stores in your online history

1. Websites
2. Voice Commands/Searches
3. Connected Devices
4. Location History
5. YouTube Video History
6. YouTube Search History

Feedback

MATHS IS HARD!

"I'm finally rebuilding my quad and I'm using "RTF 2208-2300kv" motors with "Rotorgeeks RG20" 20Amp ESCs. I'm planning to get a 2200mah 4S battery to keep from overloading the ESCs. What C rating 4S battery should I get. If my calculations are correct, anything over 10C would overload the ESCs anyway. That doesn't seem right. Am I using the wrong equations?"

-- T Raburn

Let's talk about Power!

• Motors are typically rated for Watts, with a maximum voltage.
• ESCs are rated for Amps, with a maximum current (amperage)

In this case, the RTFQ 2208-2300KV motors are rated for 295 watts MAXIMUM

• It also tells us that it can handle a 4s battery, (14.8 volts)
• Watts = Volts * Amps
• SOOOO.... at 295 watts, 14.8 volts, it's going to pull 19.934 Amps of current

Now the ESCs

• We know that our motor will pull a maximum of 19.934 amps of current at 14.8 volts, so we need to ask ourselves:
  1. How much current can the ESC handle
  2. How much voltage can the ESC handle?
• It will do 20 amp and AT LEAST 14.8v (4s) so we're good.

But now the battery:

• You're going to have 4 x 2208 motors puling a max of 295 watts each
  • That's 1180 watts of continuous power (at maximum)
• So... how do you determine the C-Rating that you need?

Again: Watts = Volts * Amps

• The "C" rating multiplied by the Amperage rating of the battery = discharge current: how many amps can you pull from the pack

If I have a 3s, 2200mAh 20C battery

• (2.2amps * 20C = 44amps discharge current) // 44amps * 11.1volts = 488.4 watts

If I want to be able to support all my motors at max power, I need a battery that can pull 1180 watts

• If I know I want to use a 4s (14.8 volt) battery, then the equation is simple:
  • Watts = Volts * Amps * C-Rating
  • 1180 = 14.8 * Amps * C-Rating
• To get the required power, I can either up the rated Amperage of a battery, or up its discharge rating

For Example:

• 4s 1000mAh 25C battery
  • 14.8 * 1amp * 25
  • 370 watts
• 4s 5000mAh 25C battery
  • 14.8 * 5amp * 25
  • 1850 watts
• 4s 2200mAh 60C battery
  • 14.8 * 5amp * 60
  • 1953.6 watts

Connect with us!

• Don't forget to check out our large library of projects at https://twit.tv/shows/know-how.
• Tweet at us at @PadreSJ, @Cranky_Hippo, and @Anelf3

Links

• The Little Gear That Could Reshape the Jet Engine
• Run Android Apps in Windows® 7/8/10 with AMIDuOS
• Rotorgeeks RG20 ESC
• Stupidest Drone Crash Ever (w/pumpkin) - I'm a moron