Know How...

Nov 5th 2015

Know How... 168

Geared Turbofan, WinDroid, & Google History

Super Engine, Android on Windows, Google History.
Although the show is no longer in production, you can enjoy episodes from the TWiT Archives.
Category: Help & How To

Pratt & Whitney's new Super Engine, DuOS is full-Android in either a VM or a Container, Interdrone LightWare,

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 exaust 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.

* 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.

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

-- T Raburn
"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?"

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

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