Happy Birthday to me

It's 5:13pm, and I'm sitting in the shade in my back yard, tweaking some really neat flexure mounts, while keeping an eye on two of my kids and two of their friends frolicking in the pool I built years ago. It's hot out, and there is steady traffic between the two hives near the back of the yard and the fountain to my right. A pair of ducks have been watching the kids too, and though they like the look of all that water they're leaving for someplace less noisy.  Lady Jane, our black Labrador, is lying in the grass, which is overdue for mowing, ripping up stems and chewing away. There are stains from fine droplets of sunscreen on the back of my laptop that won't be coming off. Martha will bring my youngest daughter back from gym class in an hour and then we'll head out for my birthday dinner.

At least once a day, at least one person helps me accomplish something I cannot achieve myself, things I am really happy to be working on.  I wonder if I manage to help someone else every day in the same way.

I have a lot to be thankful for.

Wicked

Just read "Wicked: the Life and Times of the Wicked Witch of the West". This after we saw Wicked in London as part of our summer Europe trip. My cousin Christopher plays the drums and various other percussion pieces in that production.

The musical is a blast. We had great seats, the music and singing were fabulous, the staging sometimes overwhelming, the kids loved it, Chris showed us around a little bit... what fun.

When we got back, we got the music, and now the kids have mostly memorized all the songs. It's slightly disturbing seeing my 4 year old singing "No one mourns the wicked".

Martha got the book out of the library, and we both read it. Like all tragedies, it's frustrating. It's a vastly more complex and subtle story than the musical. If you're reading this but haven't read the book or seen the musical, see the musical first, as it'll be tough to enjoy after the book. And don't read the rest of this post.

SPOILERS.

Like most things that I really like, I wanted the book to be better. In particular, a good tragedy should make me feel the inertia of doom, the sense that the characters are carrying themselves towards their downfall. In the book, there was definitely some of that, but I also got the feeling that doom was coming in the form of spunky little Dorothy Gale, and that the characters were bending their wills to the needs of that other story arc. So that wasn't as impressive. And why the hell couldn't a smart girl like Elphaba convert the tactical (and unsuspected) advantage of being able to fly on a broom into a way to pick off the wizard and his chief lieutenants.

The part that I really liked was how Elphaba's desire to do good was a significant part of what drove her to her doom. I find myself strongly agreeing with the idea that the desire to do good is not good in itself, and can actually lead to evil. If you want to be good you have to actually *do* it.

But there were so many things to love about the book. The dialog, the political machinations, tictocism, Elphaba's reaction to Dorothy asking for the forgiveness that Elphaba herself had been denied... I love reading an author who has insights way past my own.

A Great Day

Today my dad and I took my daughter Anya to an event hosted by the UC Berkeley Nuclear Engineering group. I got my BA at Berkeley, and my dad was a post-doc there in what was then called the Nuclear Chemistry group. It was great fun showing Anya around a small portion of the campus where I spent nearly seven years.

We started with lunch and about half an hour of Frisbee on Memorial Glade. After that, Anya (7 years old) spent three consecutive hours in 6 classrooms listening to and participating in discussion and demonstrations about radioactivity and nuclear power.

Anya spent probably 20 minutes of that wriggling around in her seat and the rest of the time she was engaged. The presentations were perfect for someone her age. The students doing the presentations were energetic and interesting. We got to see the old reactor room in Etcheverry Hall which now houses a bunch of interesting experiments. I got to meet a bunch of other parents, and it was fabulous to talk with other people who don't freak out when they discover that every home's smoke detector has a little bit of Americium-241 which sends the Geiger counter up several orders of magnitude once you get it close enough that the air isn't shielding it. (Pop - pop - pop - bzzzzzzzeeeeeeee)

Afterwards Anya and I walked around campus some more, watched some students learning to walk on a tightrope, and then went out to dinner together at Zachary's Pizza. For most of the hour long drive home we talked about how to design an "earth-friendly" town -- things like arranging the houses around a central area for the kids to plan in, building at the edge of but not in a forest, etc.

So, basically, I had a perfect day.

Pool is filled

Thursday was a big day for all of us. Any passers-by seeing the girls running around in bathing suits for a few days now may have guessed the reason: we plastered and then filled the swimming pool.

Pocohontas Retold

Spoiler alert: I discuss the movie Avatar below.

When I read the Pocohontas story to my kids (we have the Disney version), we usually have a little discussion when we get to the page where Pocohontas attempts to dissuade her father (the local Indian chief) from starting a war with the settlers. The kids are interested in the idea that both people are trying to do the right thing, but they have completely different ideas about what the right thing is.

For those of you not familiar with the story, Pocohontas has fallen in love with a mercenary on the voyage (John Smith), and the two of them want to establish peace between the settlers and the natives. The book suggests that peace involves the settlers staying in North America. Powhatan, her father, is assembling a war party to drive the settlers away.

We can look back in history to better understand who was "right".

• As the book makes clear, a war between the settlers and the Indians is going to lead to many Indian casualties, since the settlers have guns and the Indians do not. Furthermore, most of the settlers are not intending to do harm to the Indians, as they've been told they are settling land that has no ownership yet. Pocohontas' efforts end up saving many well-intentioned people's lives.
• These same settlers would probably understand that, had they landed anywhere in England and built a village where they landed, they would be summarily evicted by whomever owned the land they were on. The racism here is lightly touched on in the book, but it's helpful because it's pretty easy for the kids to see how convenient it is for the settlers to suppose that nobody in North America owns anything yet.
  
• I usually tell the kids what little I know of the Mauri, the indigenous people of New Zealand. As I understand it, they immediately made war with white folks who arrived. I suspect that the Mauri were territorial in a way that worked better with the White conception of property, and because of that Mauri today have a significant representation in the New Zealand constitution and legislature, and own very large amounts of New Zealand's real estate. I expect many Native Americans would prefer the Mauri outcome to their own.

I recently went to see Avatar. It's basically the Pocohontas story, but the ending has changed and the natives switch from the Pocohontas to the Mauri approach. The change comes from two differences:

1. The Na'vi are territorial. They have a few specific high-value trees. My understanding is that most of the North American natives had a much less specific sense of property.
2. The movie has the natives resisting under human leadership, which is interesting to think about. It seems a bit condescending (especially the bit where the human, after 3 months of training, is outperforming the best of the natives), but historically North American natives really did not grasp the nature of the European threat fast enough to organize a massive resistance in time, and it seems at least possible that a charismatic European might have communicated the continent-level consequences of the European idea of property to enough of them to organize a resistance.
   

Although the movie doesn't make it clear enough, guns are a big advantage, but a multi-year supply line is an even bigger disadvantage. Although some of the dialog is a bit trite, I think the story is probably going to be a useful place to start interesting discussions. Hopefully they'll have some story books out at some point, because the PG-13 movie is far too violent for my kids to watch.

I once asked a friend who is a lawyer if all property rights, at least in North America, trace back to peace treaties of some kind, or if some (particular the French claim to the center of the continent that was then sold as the Louisiana Purchase) are based on bald assertions of authority without even a war. I never did get a decent answer.

If, in reading this post, anyone is wondering if I'm willing to cede my house to a Native American, the answer is no.

You are so beautiful, Kathleen

Reynolds number

It looks like one of the problems with the fountain is that I'm pushing slightly too much water through the flow straightener.

At very low velocities, flow through a pipe is laminar.  I wanted laminar flow in the flow straightener because laminar flow has no turbulence which can then break up the output jet.  It turns out that the flow velocity in the pipe has to be incredibly slow, and it turns out that I managed to design my fountain to be right in the transition region between turbulent and laminar flow.

Here is the Engineering Toolbox link on Reynold's numbers.

At full flow, I'm pushing about 180 gallons/minute through 16 of those flow straighteners.  Each has an internal diameter of 15.3 cm, so that the flow rate is 3.85 cm/sec.  Plug that into the handy calculator (the one using kinematic viscosity) and you get a Reynold's number of 5213.  That's turbulent flow.

At the flow tested in January (which worked properly), I was going up about 33 inches instead of 65 inches, so my jet velocity was 71% of full flow now.  Also, the cross section of the jets was .41 inches instead of 0.5 inches as it is now, so that the velocity inside the flow straightener was 48% of what it is now.  Plug 1.84 cm/s into that Reynold's number calculator and I get... 2491.  That's transient flow, but quite close to the 2300 needed for laminar flow.

If this is really the only problem with the fountain, then I ought to be able to slow down the flow enough to get the Reynold's number down to something around 2300, and see laminar flow at the output.  How slow?  To get half as much flow, the jet velocity is halved, and the arc height goes to 1/4 of what it is now, or 16.5 inches.  In fact, at that velocity, I do indeed get laminar flow:

Note that the impact here is on the first step into the hot tub, which is a little lower than the nominal water surface, and the arc is about 20 inches above the nozzle rather than 16.

The jet is well behaved until it gets to the top of the arc, where the bottom of the jet interferes with the top of the jet, and the result is that is spreads out laterally. That lateral spread then turns into an oscillation in the flow until it hits the step.

Anya demonstrates that the jet is 18 inches above the bond beam, or about 20 inches above the nozzle.

At this point the default setting for the fountain is to throttle back to 40 inches throw height, which clears the occupants of the hot tub and isn't too noisy.

If we wanted to get the tall jets to behave properly, it appears we'd need to cut the flow rate approximately in half, which means we'd have to reduce the jet diameter to 0.350 inches instead of 0.500 as it is now (so the finished hole diameter would be 0.440 inches).  That means I'd have to pull the stainless steel nozzles (recall they are epoxied into the PVC heads right now), get new nozzle made (probably $300), and epoxy them back in.  That all sounds possible, and certainly cheap enough, and probably can be done fast enough given that it's going to take 5 weeks to get the tile delivered.

However, there's a good chance I'd just destroy the PVC heads in the process, and there is also a good chance I'd get the nozzles glued back in crooked.  I don't think we're going to try.

We're getting more comfortable with how it looks.

Fountain test

Belle, non?  (1/80 sec exposure)

Non. (1/4000 sec exposure)

Here it is with Martha for a sense of scale:

First, what went right?

• The geometry is right.  In this spreadsheet, I calculated the height of the fountain (69.4 inches, was actually 65.5 inches), and how far it would throw the water, and where the jets would come down into the hot tub.  Although some of the jets land about 5 inches off where I expected, and two jets collide in midair just before they hit the water, the geometry is about as good as can be expected, and fulfills my goals, which were:
  • It should be possible to walk between the rising jets without being hit by them.
  • It should be possible to sit in the hot tub without being hit by the jets.
  • It should be possible for a child to stand in the middle of the hot tub and have the jets come down all around, without actually hitting the child.
• All the jets rise to the same altitude, within about half an inch or less, which means the balanced binary tree distribution system with the shorted end terminals worked.
• The pump-side pressure stack does not overflow.
• The pumps don't cavitate.  They are incredibly quiet.  You cannot hear them unless you walk over to the pump vault and stand on top of it.  Once the lid is installed on the pump vault, I doubt you will hear the pumps even when you are on top of it.

However, the jets are not laminar.  Gloppy blobs of water fall into the water and make a dull roar instead of the quiet sizzle that I had wanted.  There is enough splashing from the jets entering the water that you wouldn't want that a few inches from your face.  The kids love it, of course, because it's loud, fast, and wet, but it's not so great for the adults.

I'm pretty bummed.  What happened?

The individual jets were flow tested in January, and this is what they looked like then:

As you can see, the jets were smooth, and landed smoothly and quietly, back in January.  Now Martha jokes that if we move the back yard table to the farthest corner of the yard, we can still have a nice conversation.

I'm not entirely sure why there is a difference.  Here are possibilities, ranked by my guess of most to least likely.

• In January, the heads had no lateral ports in them.  In this latest trial, there are two ports in each head, connecting each to the heads on either side.  These ports keep the pressure even across all the jets, which makes them shoot to the same altitude.  But these ports may also be causing the water to tumble slightly as it passes the edges, and that turbulence may be causing the breakup that I'm seeing.
• In January, the heads were surrounded by nothing, and so small amounts of water on top of the heads ran down the sides, away from the jets.  Now, the heads sit inside recesses in the gunite.  Each head has a small pool of water in it that terminates at the jet.  The water in this pool greatly disturbs the jet during startup, but it gets cleared in two or three seconds and then I don't think there is any more water recirculating through that pool and into the jet.
• In the January trial, I had an open-topped pressure stack between the pump and the jets.  In the production version, I have a stack after the pump, but it's not quite the same.  In this one, the water from the pumps goes to a Tee.  In one direction, the water heads for the jets, and in the other direction, the water heads for the stack.  It's possible this alternate arrangement works less well.
• This test has a closed air volume right before the jet, which was intended to be an additional flow smoothing device.  The January arrangement used open-topped pressure stacks either right before each flow straightener, or right after the pump, and both worked well.  The closed air volume is known not to work as well (since the pressure changes more with a small surge in water).  Also, since the current arrangement has two capacitors with an inductor between, it's possible that there is oscillating pressure being stored between the two capacitors.
• The nozzle holes are 0.590 inches, rather than the 0.500 inch holes that I tested in January.  This makes the jet diameters about 0.500 inches, which is necessary for all 200 gallons/minute to flow.  As a result of the larger jet and the larger jet velocity, the flow through the flow straightener is perhaps twice as fast as it was in January.  It would be great if this were the problem, since I can reduce the flow later when I have that plumbing finished.
• In January, the pump had air in the lint basket bowl, and the pump could be heard continually injesting air.  Now the pumps have no air in their lint basket bowls.  I would expect this to make things better now, but I thought I'd list it because it is a difference.

I also have two unexpected observations which may be a clue to a solution if I can figure it out:

The ports in the sides of the fountain heads are connected via riser pipes to a plenum that is fed from a pipe that will ordinarily lead to a blocked valve.  This valve is used when the fountain is off to backflush the flow straighteners.  However, that plumbing is not yet finished, and so the pipe currently leads to many other pipes that are currently filled with air.  There is also a hose bib and a pressure gauge connected to those pipes (this is how we did the pressure test).  I have calculated that the static pressure at the top of those fountain heads is about 3 psi above ambient, and so I expected the plenum to be pressurized at 3 psi.

But that's not what the gauge says.  The gauge shows zero pressure (I don't have any gauges that show negative pressures).  If I open the hose bib while the fountain is running, then cover the opening with my finger, I feel a little pull.  It's very feeble, but it's there.  WTF?

The flow in the head is moving at 1.6 inches/second, and I calculate a dynamic pressure of 0.85 Pascals, or 0.00012 psi.  That isn't diddly compared to 3 psi pushing out.

[Update: Mystery retired: it turns out that the pipe connected to the top manifold is capped off right now, and those other pipes are just not connected to the fountain.  I can't explain why I was thinking that there was a small pull of air, but it certainly wasn't measureable.]

The second unexpected thing happened the first time I started up two of the three fountain pumps.  All three pumps are in parallel.  I had difficulty taking the lid off the third pump's lint basket bowl, so I had left that bowl filled with air, and just started the other two (which were properly filled with water).  I expected the first two pumps to push water backwards through the third pump, flushing the air into the intakes of the first two, where it would be blown into the fountain or otherwise ejected from the system.

Nope.  There was no noticeable flow through that third pump.  Later, I pulled that lid off and removed the air.  When I ran just two pumps again, the third pump did have flow going backwards, and in fact the impeller was turning backwards at perhaps half the RPM of the two powered pumps.

It's not clear to me how the air can block a >3 psi pressure drop.  The total drop from the top of the pump to the bottom of any associated piping is perhaps two feet, which would account for a 1 psi drop block, but not 3.

I suspect that the solution to these mysteries, especially the first, will tell me something about the fountain behavior.

Chickens

I'm amazed by our hens' abilities to eat.

I weigh 215 pounds, and eat something like 2700 calories a day, including about 150 grams of protein. So, about 22% of my calories are protein. Those are rough guesses, not measurements.

Our hens each lay one egg a day, with around 6 grams of protein. I'm going to guess that they must eat 24 grams of protein to deliver those 6 grams, and also run around the yard and make lots of feathers. 24 grams is about 1/6 of what I eat.

The hens eat grass, cornmeal, random bugs that they find, and snails. (Martha has found no snails at all in the last year in the back yard, but clears 10-20 every week from the front.) I don't think their diet is particularly higher in protein than mine. In particular, their cornmeal is almost identical. So, each hen must each 1/6 of the calories I eat.

These animals weigh 5 pounds! (Anya just weighed them.) Per pound, they eat seven times as much as I do. Since I spend at least an hour a day eating, it's no wonder that those hens spend every waking minute pecking at something.

Tooth Fairy Traffic

Anya just had a tooth pulled by the dentist.  She put it under her pillow but the Tooth Fairy seems to have not made it last night.  A few notes:

• The Tooth Fairy came on the fourth night after she lost her last tooth.  Anya's theory is that the day before she lost that tooth, a little boy lost one of his, but he was sick, and the Tooth Fairy caught a bug when she touched the tooth.
• I believe Anya is lying, eyes closed, in tense anticipation of the Tooth Fairy.  She was watching Martha and I as we climbed the stairs last night at 1:30AM, and she was wide awake and ready to go at 7:00AM when I got her up this morning.
• Little girls, of which I have 3, have 20 baby teeth each.  Even discounting the molars, which might come out much later, I can forsee a time when the Tooth Fairy will be making more than one visit per month.  With multiple little girls engaging in outright deceit in their attempts to catch the poor fairy, I forsee delays and uncertainty.
  

I'm not sure if the full-body tension I'm feeling right now is because I'm worried that my contractor won't be able to lay out my circuit board properly, or because the damn house creaks even though it's only six years old.  Yeesh!

Keep women away from stairs!

I have summarized for your convenience the top 7 consumer killers in the United States in the year 2001, and swimming pools, for comparison.  I think the conclusion here is inescapable: women must be kept away from stairs. This is a significant issue for me because I live in a house with two stories and a basement, with my wife and three daughters. Although the statistics presented are not specific, it does appear that the problem is largely with older women, so we'll definitely have my mother in law stay in the downstairs bedroom.

As I write this my two older girls are directly behind me, messing around in the crib that we generally use for our youngest. A quick check shows that I should escort them outside where they can safely fool around in traffic on some ATVs!

total deaths	male accidents	female accidents	category
202104	767142	1274004	Stairs, Ramps, Landings, Floors
45964	248445	291530	Beds, Mattresses, Pillows
30271	203930	252960	Chairs, Sofas, Sofa beds
25023	125312	168238	Bathroom structures and fixtures
24750	414008	151660	Bicycles
21239	169834	38022	ATVs, Mopeds, Minibikes
19085	150667	72498	Ladders, Stools
5322	88864	72894	Swimming Pools, Equipment

Fountain Prototype

Martha and I are building a pool in the back yard. In that pool will be hot tub, and pouring into that hot tub will be a fountain. I want lots of water flow, and curves, especially since the overall pool will be rectangular (due to the automatic cover). To give you an idea, here's the pool:


The hot tub is circular, and has a 1 foot thick wall that seperates it from the pool. Out of the center of that wall, water will leap up, arch over, and fall into the tub. This will pour nicely over your shoulders if you are an adult, and it will make a fancy tube to explore if you are a child.

The trouble is that nobody sells a curved fountain like this. No problem, I'll just assemble it from a number of straight sections. Also, I do not want to use high-pressure pool pumps for this thing. Instead, I want to use low-power, low-pressure pond pumps. The manufacturer of the fountain has specs for the amount of water flow you need, but not the pressure. I smell project risk. Time for a prototype. Here's the overall arrangement: two fountain units, 1 foot wide each, one Sequence 4200seq12 pump, and some pipes to move the water.





I've got a flow gauge, two pressure gauges, and a ball valve so I can figure out how many gallons per minute throws the water how far.


I've also got a peanut gallery. They're interested because they're going to get to dance around in the water in a bit.


The fountains throw water about as far as the manufacturer claims. Note that my flow rates are for two 1 foot units.

Flow rate	Throw	Notes
48 GPM	26.0 inches	7 inch rise
45 GPM	23.5 inches
41 GPM	18.7 inches
37 GPM	14.7 inches
35 GPM	11.5 inches	3+ psi pressure drop

I learned a bunch of things from this prototype:

• The flow through the two units was not identical. One moved about 8% more water than the other, and threw the water a little further.
• The flow through each units was not uniform. The unit throwing farther was throwing farther on one end.
• With no fine filtration, and just a skimmer before the pump, the fountain units quickly accumulated debris that interfered with the flow.
• The water sheet from each unit contracts from surface tension as it gets farther from the fountain. A 14 degree included angle between the two units turned out to roughly match the contraction, but this still left a constant gap from one to the next. I may try to fix that by mitering the two fountains together.
• Martha and I agreed that 15 or 20 GPM per linear foot is not enough. We really like 25 GPM/foot better.
• The fountain water entering the water surface was the cause of all the noise. The pump was really quiet, and you could only hear it when you walked right over to it.
• The pump really doesn't prime itself. I had to stuff a hose up the intake and fill it full of water before the pump would move anything.
• This pump can just move 48 GPM with this setup (which implies it is seeing about 5 feet of head). With more angles and losses in the system, I am going to need more pressure at that flow.

I also noted that the water sheet was rough. Water entry was noisy. I took a high-speed shot of the water, and sure enough, it's breaking up in flight. Note also how much shorter the rear fountain is than the front.


I noticed that the flow gauge was bouncing around a fair bit, so I presume I'm getting a bunch of turbulence, which probably does not help the fountains at all. These units are the "short lip" version of these fountains, which means they have just 1" of flow straightener before they launch the water. The standard version has a 6 inch lip, which I think might damp the turbulence more and lead to a cleaner sheet of water.

Inside the unit there are apparently 3 supports of some sort. These have visible wakes, but I wasn't able to see that the wakes caused more breaking up when they hit the edges.


So, my plan is not yet validated.

• I need bigger pumps. 3 of the 5100SEQ22 will produce 200 gpm total at 10' head. That should give me enough extra force to push through the extra twists and turns.
• Each fountain unit is going to need it's own throttle. The best way to implement this is probably a bank of eight $20 ball valves, and a seperate run to each fountain unit.
• As long as I'm doing a seperate run to each fountain unit, I might arrange for the final connection to be long and straight to reduce turbulence. There will be a lot of turbulence in the fountain unit itself, so maybe this is hopeless.
  
• I should order a fountain unit with a 6" lip, and see if I like that flow better.
  

Lady Jane

We have a new puppy, Lady Jane.

She's a black Lab, just like Iniki was. She's really cute and full of sharp teeth.

Teddy Bear Tea

I took my daughter to the Ritz-Carlton's Teddy Bear Tea today. $184 for a few dried-out finger sandwiches and a bunch of chocolates, a teddy bear, some singing, and a chance to get pictures with... a person-sized teddy bear. I couldn't help but think of how tasty a $184 dollar dinner can be. Or how fun the local production of "'Twas the night before Christmas" had been the day before.

Children of all ages gather for a favorite family tradition at The Ritz-Carlton. Guests enjoy a fun-filled afternoon in festive surroundings featuring a storytelling Teddy Bear, a pianist, hot cocoa, tea, a selection of tea pastries and mini finger sandwiches, and a Christmas candy and sweets buffet table. Each child takes home a teddy bear and photo as souvenirs. $75 per guest, $65 for children 12 years and under, exclusive of tax and gratuity. For additional information or reservations, please call (650) 712-7040.

I could wonder how the Ritz-Carlton could end up serving crud for such an expensive lunch. Stories from Teddy may have happened before we got there, 10 minutes late. But why bother with these specifics? A more important question is: how did I ever end up in such a travesty?

I did ask, several times before going, what exactly this "tea" entailed. Martha was nonspecific. Since the other folks going were all in one of Martha's mother's groups, I knew essentially no-one. I'm antisocial as it is; dropping me into a mother's group without something to specifically contribute to the proceedings turns me into a stone wall. I went because I was led to believe that the event had already been paid for, Martha could not attend as she had a cold, so, I might as well see what we paid for. Instead, I got a 3-digit bill. I think the lesson here is to (a) ask for specifics beforehand, which I did, but then (b) refuse to go when specifics are not provided.

From Kathleen's point of view, there was: (a) nothing to climb on, (b) nothing to legitimately squish with her fingers, (c) nothing with which to draw on herself, nor stickers, fake tatoos, or dress-up clothes, (d) no pool, and (e) no kids singing or doing something else to be emulated. Even a desert wasteland would at least have had rocks to turn over.

If anyone from the mother's club reads this, let me get in a last word: it's not you, it's me. Given something specific to do and at least some semblance of DIY flair, I can have a great time with y'all. But I'm never going to convincingly pull off an hour of small talk.

Tyrannosaurus Regina

My daughter Anya is 4.5 years old. She likes to have me make line drawings of things and then paint them. Today she wanted a dinosaur.

"Stegosaurus?"

"No, Tyrannosaurus Rex."

I'm no artist, but I did my best, and I was fairly pleased with the result. You know, the strong nose ridge, the gaping jaw filled with long sharp teeth, the massive tail, and the huge talons at the points of the rear feet.

Anya added a crown. "A princess Tyrannosaurus Rex!"

Then she insisted that I add glass slippers.

These things weighed what, ten tons? A great deal of that was the neck and torso musculature necessary to thrash car-sized animals to death. It's hard to overstate how dangerous these things would have been around princes and princesses and folks with chain mail and so forth. The talons on these things could probably punch through an unreinforced driveway.

And then, the glass slipper. The most impractical possible footwear. Like clogs, inflexible. But also prone to shattering, possessing little traction, and probably heavy once made thick enough to be safe. I'm personally certain that the glass slipper concept is due to some sort of mistranslation. But still, how do you apply glass slippers to a Tyrannosaurus?