Our Girl Scootaloo 3 of 3

by Cozy Mark IV

Ch 3.12 Revving the Engine

Our Girl Scootaloo

Part 3 of 3

by Cozy Mark IV & Jan. McNeville

Disclaimer: This is a non-profit fan-made work of prose. My Little Pony: Friendship is Magic is the property of Hasbro. Please support the official release

Chapter Three point Twelve: Revving the Engine

Celestia, Twilight and Rainbow had all gathered in the impromptu training room the Agents had set up in the hospital and were chatting with Scootaloo and Josie while waiting for the next lecture to start.

“Why do we have to be here again?” Rainbow complained.

Scootaloo tried to be patient. “You're here because you want to be allowed to fly in our world. To do that, you have to practice for forty hours and pass a test as a pilot of an earth flying machine.”

“I can handle myself in the sky better than anyone! There's no danger I can't...” She trailed off as the screen at the front of the room began playing a video of famous airplane disasters. Scootaloo played back a particular selection of a jet engine swallowing a flock of geese four times as Rainbow's cocky attitude mellowed somewhat and the others looked concerned.

Her point made, Scootaloo continued. “The rest of us are here because to understand our world, you need to understand how we get along without magic. All of you have asked me at one point or another how cars move, how planes fly, and so on. To that end, Josie” her friend nodded politely “has brought her husband in to explain what engines are and how they work.”

Philip had finished setting up at the front of the room and took the opportunity to introduce himself.
“Hello everyone, it's really quite a privilege to be your instructor today. Lets start off with the basics. By now you've all asked the question and probably gotten a lot of different answers, so let me ask you. What is an engine?”

“Duh.” Rainbow rolled her eyes. “It's the thing that makes cars and stuff go.”

“Fair enough. Do you know how or why they work?”

Half of Rainbow looked confused, while the other half of her expression was smug. Twilight was paying rapt attention, and Celestia and Scootaloo were following along.

“Okay, I get the feeling this will be old hat to Scootaloo and Dashie but don't go to sleep on me, I promise I'll throw in a few bits for you too.”
“First and foremost, an engine is a device that uses a change in temperature or pressure to make useful energy. All engines, no matter how simple or complex have either a hot and cold side, a high pressure and low pressure side, or both. They allow energy to flow from the hot, high pressure side to the cold, low pressure side and along they way they use some of this energy to do useful work. The more energy they use for work, they higher the efficiency of the engine.”

“So how efficient is one of those cars we saw on the street?” Twilight asked. “Ninety five percent or so?”

Philip laughed. “Not exactly. The average automobile is around twenty to twenty five percent efficient. That means seventy five to eighty percent of the energy from the fuel is lost, mostly as heat.”

Even Celestia looked a bit surprised. “The cars we have seen everywhere are actually that wasteful?”

“You got it. The most efficient engines in the world, the building sized power plants we use to make electricity, are a little over forty percent efficient. The very best ones are just a hair over fifty percent.” He thought for a moment. “Do you know why that is? What drives efficiency?”

Rainbow scratched her head. “Awesomeness?”

“Delta, actually. The difference between hot and cold, high and low pressure. The bigger you can make that difference, the better the efficiency you can pull out of a system. The really high efficiency power plants get there by using unbelievably hot, high pressure steam to run their turbines because the bigger the difference between the hot, high pressure steam and the cold, room temperature air, the more they can wring out of the engine.”

“I think I can follow that...” Twilight said as she looked up from her notes. “Bigger difference equals more efficient.” She thought again, tapping a hoof and pen against her jaw. “Does that mean that the cars we saw are powered by steam?”

“Good guess, but no. Steam is just a convenient way to run a power plant: Wrap pipes full of water around the hot side whether it's a big box full of burning coal, oil, gas, sunlight, lava, or a nuclear reactor. Steam turbines are efficient, but they're also big and heavy. Cars and mobile machines usually use piston engines, burning either gasoline or diesel fuel.”
He searched 'how piston engines work' and pulled up a couple of videos for them to watch. “The concept isn't hard; a piston engine just creates a series of hot, high pressure explosions and uses them to shove the pistons down and turn the car's wheels. The details get complicated fast, but at its core, that's all there is to an automobile engine.”

“What was that big round engine Scoot here showed us? The one that sucked in those geese?”

“That was a gas turbine engine or jet engine. Instead of a series of explosions, a gas turbine creates one big, continuous explosion. The first half of the engine is made up of spinning blades that compress the air tighter and tighter. In the middle, they inject the fuel which explodes and expands out the back, turning the expansion stages and generating power or thrust.” He indicated the different parts of the animation as he spoke.

“So, in summary, that's how we get along without magic. Any time you see a machine moving, it's a safe bet it has an engine and burns some kind of fuel to make useful energy.”

Twilight looked thoughtful again. “But what about 'electric' cars? You didn't say anything about electric engines.”

Philip smiled at her catch. “That's because electric cars run on electricity from a battery. The battery is just a big jug full of electricity, and the car doesn't burn anything to make the energy. There is no hot and cold side, no high and low pressure side, so anything that uses electricity is not an engine, it's an electric motor.” He thought about that for a moment. “I should probably mention the basics of electricity while I'm at it. Who here knows what electricity is?”

“We see it as lightning on our world.” Celestia answered.

“True enough, but what is it? What is it made of?”

Silence filled the room.

“Okay, it's not actually that hard; let me explain.” He searched 'periodic table' and selected a model of a copper atom. “These are all the elements that make up everything you have ever seen. They're the building blocks of all matter including you and me. Simply speaking, all atoms are made up of protons, neutrons and electrons, usually with about the same number of each. Each positive proton in the center wants to hold on to an electron orbiting around the core of the atom, but some atoms like copper don't hold on to their last electron very tightly.”
The animation changed to show a chain of copper atoms, their electrons swirling around them. “Now in copper, because that last electron isn't held very tightly, we can start a sort of bucket brigade of electrons. If we shove one new electron onto this first copper atom, its own electron is kicked loose and jumps to the right, which kicks loose another electron which also jumps to the right, etc. That's all electricity is, its just a bunch of electrons surfing from one atom to the next like buckets being passed from person to person or like water flowing through a pipe.”

“Okay... That's kind of neat actually...” Twilight muttered as she frantically drew out the diagrams. “But how come it behaves so strangely? Some electricity jumps through the air like lightning but your people seem to have harnessed it and used it as a tool.”

“Fair question.” Philip replied. “That gets back to how you measure electricity. There are two basic ways: Current tells you how big the pipe of electricity is, so more current equals a bigger pipe. Voltage tells you how much pressure is pushing the electrons, so more voltage equals more pressure, and just like with water, if the pressure gets high enough, the pipe leaks and electricity arcs everywhere.”
“Power is measured in Watts, and its just pressure times pipe size, or voltage times current. You can have super high voltage, or pressure, and still not have any power if the pipe size is almost zero – that's like the static electricity you shock your friends with by scuffing your feet, er, hooves, on the carpet.”

“So...” Rainbow spoke up. “No matter how much I scuffed my hooves on the carpet, I couldn't make enough electricity to drive a car?”

“Basically, yes. The amount of electricity you make that way is so small as to be almost useless.”

“Okay...” Rainbow was thinking hard. “But lightning looks just like that, only bigger, and it can split trees and do all kinds of damage. How do you explain that?”

“Well, remember how you have both pipe size and pressure? Current and voltage? It's actually possible to trade one for the other. Power is pipe size times pressure, so you can constrict the pipe to boost the pressure, or make the pipe bigger and watch the pressure fall, but the power doesn't change.”
“Lightning has both high voltage/pressure, and a big pipe size/current. Put both of those together and you have a lot of power to do work, like splitting trees. I should also mention that it's the current, the pipe size that splits the tree. Remember how you can trade pressure for pipe size? Well, it turns out that only current/pipe size generates heat. If you shift the balance to almost all pressure in a tiny pipe, high voltage with low current, you can ship electricity very long distances with almost no loss of power.”

Rainbow and Celestia's eyes both widened as they remembered Scootaloo's demonstration with the metal pole their first night on earth.

“So that's why the lightning jumped out and fried the pole! Because it was high pressure, er... voltage!” Rainbow shouted. “And it's high voltage because...?”

“Because if they used high current/pipe size, the wires would have to be way bigger, and they would heat up like a toaster. Instead of shipping electricity across the country, you would be heating up the butts of all the birds who came to sit on the wires.”

Celestia and Twilight chuckled as he continued.

“Incidentally, that's how welding works. The welder changes the mix from some pressure, some pipe size, to nothing but pipe size/current. Then when the arc of electricity jumps through the metal, the metal gets white hot and melts so you can weld. Same idea with lightning spiting a tree. The lightning has high voltage and high current, so when high pipe size/current flows through the tree, it heats up the water in the tree until it boils into steam, then the steam explodes the tree from the inside.”

“Okay, that is pretty cool... But why do I have to know this again?” Rainbow asked, her cocky attitude making a reappearance.

Scootaloo just grinned. “Who did you think fixes the engine in a plane if it has problems during the flight?”

Rainbow slowly worked it out as Josie tried not to giggle.
“You mean I have to know how it works or I won't be allowed to fly?!”

“You got it, newbie.” Scootaloo confirmed with a grin and a slap on the withers. “Now anyone who doesn't need a pilot's license is okay to leave. Rainbow and I will be staying right here for the next few hours as Philip explains the intricacies of carburated aircraft engines.”

Rainbow just groaned.

…

The day was finally winding to a close and after all the excitement and stress, Scootaloo and David had both been looking forward to some time alone together. By the time she flew in to land on the roof of their apartment, David had already tucked the foals in for the night and he met her at the door of their third floor apartment.

“Long day?” He asked

“You have no idea.” She pulled him down to her for a long kiss. “Don't get me wrong, the seven of them are incredible, but I never really appreciated how nice it is to just turn the show off when I get tired.”

“Hmm... and how tired are you tonight? I've got a bowl of fresh fruit salad on the nightstand...” He knelt down and ran a hand up her neck, tracing a line under her chin before taking her muzzle in his hand and kissing her passionately in that way that made her knees week.

Scootaloo shuddered delightfully but managed to keep her footing and followed him to the bedroom. She hopped up onto their bed and helped him out of his clothes as he continued to plant kisses on her neck and face, pausing now to nibble her ears in a very... distracting fashion.
“Hmm! That's enough out of you!” she smiled mischievously as she shoved him down onto the bed and quickly locked his hands into the handcuffs waiting under the mattress at the head of the bed.

“Oh! So you're on top tonight?” He asked playfully.

She responded by pinning and kissing him, his head held in her arms.
“You got it, Doc.” She replied as she finally came up for air. “Now that I have your... undivided attentions, how about you....” She trailed off as she laid down along side him, her head on his knees as she exposed her belly and both rows of her nipples.

Several minutes later and just as she was starting to really enjoy herself, she felt her arms abruptly fall off. With a start, she looked back to find David had escaped the cuffs and unbuckled the straps holding on her prosthetic before tipping it harmlessly onto the floor.

“Hey!” She complained half-seriously as he pounced her and buckled the soft institutional cuffs around her front hooves, anchoring them to the foot-board. Her back hooves were soon similarly cuffed and spread as she complained; “No fair hiding the keys.”

David just smirked as he levitated the handcuffs in his right hand and moved his left hand lower, making her gasp. “Didn't need to. Magic, remember?”

Magic indeed! The feeling was like nothing she had ever felt before, and she was soon writhing in her bonds as he continued to experiment on her.

Then, as she pulled against the well worn cuffs they simply came off, their buckles open and unlatched.

'Right... Magic...'

This was going to be a long night...

…

Later the next morning a very frustrated Scootaloo sought out Rarity for some help. Rarity had just finished dictating more stories about her life to the researchers working out of the hospital, and was stepping out to use the ladies' room when Scootaloo found her.

“Hey, Rarity! Do you mind if-”

A somewhat pained look crossed her face as she gestured for Scootaloo to follow. “I'm sorry dear. I may have gotten just a tad carried away, and now I really need to use the powder room.”

Scootaloo raised an eyebrow. “How long were you in there telling stories?”

“Well, I got started right after breakfast... What time is it now?” She asked as she opened the door with her magic.

“Breakfast was over at eight. It's almost noon now.”

Scootaloo saw what looked like a blush as Rarity closed the stall door. After a moment there was a frustrated and most unladylike grunt. “Damn! I've been here for days now and I still can't get the hang of this.”

Scootaloo blushed as she realized the normal stall was too short to accommodate Rarity with all four hooves on the ground. There was a fumbling sound, and the door seemed to bow, straining against a great force. Scootaloo turned on the water and began washing her hands to hide her blush when there was a sudden 'Crack' and 'Bang!' as the latch gave way, dumping Rarity face first onto the bathroom floor.

“Oh crap! Are you okay?” Scootaloo asked as she bounded over and helped her friend up.

Rarity was red as a beet and looked like she just wanted to sink into the floor but seemed otherwise unhurt.

Scootaloo managed a small smile. “Damn bipeds, am I right? Here, let me show you.” She tossed the broken latch into the trash, then flipped up both seats, tucked her tail back and splayed her legs into a half seated position with her front hooves pressed against the support columns between the door. “This is one way if there isn't an alternative but in any decent rest room they should have a handicapped stall at the back.” She got down and gestured to the last stall. “I think you'll find that one more to your liking.”

Moments later, a much relieved Rarity emerged to clean up in front of the mirror, still blushing a little at the cheeks.
“Thank you, Scootaloo, that was much better.”

She chuckled. “Hey, it's not easy being a pony sometimes. When I got here they had to remove some of those damn 'low flow' toilets that didn't work like they ought to. You should have seen me blushing as I tried to explain to the dean that nearly three hundred pounds of purely vegetarian pony isn't compatible with 'low flow' designs.”

Rarity grimaced. “I can only imagine. I just feel bad for the Princess.”

“Ha! Yeah, Agent Tyler told me what happened that first night. It shouldn't really have surprised anyone that fifteen hundred pounds of pony was too much for normal plumbing. Is it true she actually gave the princess a package of horse diapers?”

Rarity's eyes went wide. “Is that what that box was full of? No wonder she was in such a foul mood when I asked her what was wrong!”

“Well the plumbers had a new room set up for her by morning, so I guess she didn't need them, but given the scare she gave my Sophie Belle, she got off light.”

Rarity seemed to consider this as Scootaloo changed the subject.

“At any rate, that wasn't the reason I came to find you.”

“Oh?”

“I heard you went to one of the local strip clubs on that first night here, and that you fit right in with some of the dominatrices. Agent Tyler said you sell... bondage gear in the boutique back home?”

Rarity's eyes lit up with glee. “Well, of course darling, it's one of my specialties. I can usually guess someones interests without too much trouble and I would guess that you enjoy a little... restraint in the bedroom?”

Scootaloo smiled and blushed just a little. “You would guess rightly then. But I have to ask, how do you do it back in Equestria? It was easy enough before, but now...” She trailed off as she used a hoof to levitate a quarter. “Nothing will stay on anymore. It was bad enough when we had to move all the chemicals out of the kids reach, but now this? How do you deal with this back home if anyone can just open a padlock or undo a knot anytime they like?”

“You mean...” Rarity ran that over in her head. “Ah. I keep forgetting you couldn't use your hooves to pick things up before we got here.”

“Well, yeah. I've used a set of prosthetics all my life.” Scootaloo answered, tossing the coin from hand to hand.

A growing blush set in as Rarity imagined just how helpless she would be without magic or prosthetics. She shook her head to clear it of... thoughts.
“Well, at any rate, its not particularly hard. You need only wrap something around the hoof or horn, and put a binding spell on it.”

“Binding spell?”

“My goodness,” Rarity smirked, “you're not a complete novice are you?”

Scootaloo blushed again, glad they had the bathroom to themselves, but decided to up the anti. “Well, given that David and I had to figure it out from scratch, and without magic, I doubt we have your skill set.” She took a step nearer, rubbing her hands together with feigned glee. “But who knows? We're both dedicated researchers. Maybe you should stop by some evening and we could show you a thing or two?”

In her line of work, Rarity got that a lot, but she hadn't been expecting to hear it from the little orange foal they had come to rescue.
'On the other hoof, she certainly isn't a little foal any longer...' She thought to herself as she ran her eyes over Scootaloo's body. A smile slowly spread across her face. 'Oh, what the hey, what fun is life without a change now and then?'

“Why, I'd love to, darling. Does tomorrow night work for you?”

'Shit!' Scootaloo thought frantically as she maintained her outward composure. 'I'm not into girls!... But this is something she does for a living... And all we'd have to do is go through the toy box with her...'
A wicked thought occurred to her as she remembered the tiny high voltage transformer she had wired into the AED unit that was an integral part of her prosthetic arms. Careful to keep the AED off, she flipped on the transformer with a thought and traced a finger up Rarity's neck, watching the hairs stand on end under the crackle of the violet electrical discharge. “I'd like that.”

Rarity leapt back, eyes wide and she nearly fell again at the unexpected assault on her senses. “What... What was that?”

Scootaloo found herself genuinely smiling now. “Oh, just a little... modification I installed for my husband's benefit. Its just a different power tap that shares the same electrical contacts I use in my work as an EMT. But enough of that. Weren't you about to teach me some novice technique? Binding spells I think you called them?” She added, matching Rarity's wicked grin.

'Hmm... This could be interesting after all...' Rarity though to herself.
“Um... Yes... Binding spells.” She cleared her throat. “They're really quite simple, and any pony can do them, even Pegasi and Earth ponies. It works like this;” Rarity took out a bit of ribbon and held it in her hoof, while she concentrated. “You think something along the lines of 'no magic' or 'bind' or similar, followed by the pony's name, or your memory of them.” She passed the ribbon to Scootaloo who took it in her hoof. “Now you do the same thing. Think 'bind', then 'Scootaloo', then your safeword.”

Scootaloo raised an eyebrow, but did as Rarity asked.

“All done? Good, here now hold out a hoof, like that, very good.” Rarity tied the ribbon around Scootaloo's right hoof in a bow. “There. Now try to pick something up with that hoof.”

An attempt to catch the quarter showed that she now had all the dexterity of a horse's hoof again.

“And that's all there is to it. The spell will last a few years under normal circumstances, and will only work on you, or whoever else is a target and puts in their own safeword.”

Scootaloo untied the ribbon, then tied it around her left front hoof with similar results. She tried her safeword, but found she still couldn't hold the coin.
“What gives? I thought the safeword would undo this?”

Rarity chuckled. “Yes, it will, but it takes some time because I put mine on there too. Try fighting it hard, really reach for the coin.”

Scootaloo concentrated hard, and she could almost feel something straining, then giving way with a 'snap!' as she grasped the coin and picked it up.

“That's all there is to it. Usually both partners put their binding spells on the cuffs or ropes they use together. It works the same way for a unicorn's horn.”

Scootaloo thought that over. “And you can put these on any object?” Rarity nodded. “Even a wedding ring?”

Rarity smiled back at her. “Why Scootaloo, you are a quick learner. Though it is, of course, bad form to ask a lady in public.”

“Wouldn't it be fairly obvious?”

She laughed. “Oh, binding spells can become quite complicated if you want them to be. In my line of work I have become quite proficient with them. I once had a unicorn mare and stallion come in wanting a set of plain looking shoes that would match their rings, but they wanted them to hold on by themselves, and switch on and off with a key word.”

Scootaloo remembered some of the exhibitionist games she sometimes played with David... That delightful feeling when he unplugged the battery in her prosthetic, leaving her with nothing but her mouth to open doors and grip things. They could be out in public for hours and yet no one would know.

She felt a little shiver run down her spine at the memory. “Kinky mare.”

Rarity laughed. “And Stallion. She made sure he had a matching set too.”

“I don't suppose you have a book on the subject?” Scootaloo asked hopefully. “With a few million people new to magic on this world, you sure have a captive audience.”

Rarity grimaced at the pun before suddenly looked thoughtful. “Publishing? Well I do have a well known name...”

Author's Note:

Sorry for the long explanation at the beginning, but I am just tired of issues like this getting hand waved. Twilight asks 'what makes the car move?' and the answer is 'it moves because of 'engine', your curiosity is now satisfied, on with the story'.

Comments

[p0nypanda]

While it's true electric cars run on electricity, they also have some gasoline in them to take over if the electricity runs out.

[AnormalUnicornPony]

3356727
Not all electric cars have that in their design. The ones that do usually have an electric generator inside that has a small gasoline engine attached and those are usually called a hybrid vehicle (although there are other types of hybrid vehicles out there this is one of the most common types due to "range anxiety" the most common type.).... I am pretty sure the author was just not mentioning the far less common varieties so as to continue with the story and not get bogged down into a discussion of engineering varieties.

In any case the authors comparison of word meaning engine vs motor would still have merit since the electric motor still uses electricity (which is using a potential current (which is itself a differential)) to do the work while the engine uses a temperature/pressure differential (even the engine attached to the generator in (most?) electric cars nowadays). Yo! I heard you like differentials! So I used a differential to make another differential in the same system!

Also my arm is itchy....