Here’s the idea:  It’s an electric skateboard with no hand-held controller.  Instead, it senses the portion of the rider’s weight on the fore and aft trucks with strain gauges and commands motor current (~= torque) according to the differential between them.

So the trucks (where the wheels go on) are actually electronic scales.  It knows which way I’m leaning (toward one end of the board or the other), and accelerates in that direction.  That’s pretty much it.

I and the great Frank Schmitt tried to make one of these back in the 20th century when we lived in California.  He’s carrying the torch presently, while I fired all of my guns at once on this proof-of-concept.

I came up with some way to belt-drive the wheels, glued the strain gauges (the little brown rectangular thingies) down to some custom trucks, and hacked together an all-analog (!!!) motor controller that used the strain gauge signals to compute a current command and drive an H-bridge power stage accordingly.

Upside down to show the complexity. The big metal box housed the batteries, and the 9-volts were to deliver +/- 18V to the analog motor controller! (I forget what the black box is.)

Closer-up of the back end. I think those are Speed-400 motors, one per wheel, belted to pulleys that I somehow screwed onto the polyurethane wheels. The strain gauges are visible as little brown rectangles on the trucks.

Left of the purple truck piece is the analog-output current sensor, and to the right are the battery/controller current fuses (lot of good they did me).

(I like how the photography came out. Thanks to Mom and Dad's 1967 Nikon!)

My Crap-o-Matic H-bridge power stage for the motors. Notice the SOOT emanating from the second MOSFET! (Power electronics is hard.)

Of course it's an all-analog strain-gauge-informed current-mode DC motor controller. What else could it be?

One Saturday night I finally got it all together at work, turned it on, and I swear to God, good people, that it worked for ten seconds.

Ten seconds.

For ten seconds, it responded to my fore/aft shifts in my CG and motored to get under me.

And then the power stage caught fire.

Sadly, that ends my chapter of the story, because I’m just not that into skateboards anymore.  The great Frank Schmitt is making progress a version with just two rolling-pin-style wheels that’ll allow direct-drive motors, which will be very cool.  When he updates me I’ll link to it!  Go go Frankus!

]]> http://longshotcity.com/2009/05/28/the-weight-sensing-controller-less-electric-skateboard/feed/ 1 craigrmeyer sc00097af9 sc00099269 sc00095ec5 sc000a043f sc0009fc6f sc0009c624 sc0009b239 http://longshotcity.com/2009/05/27/the-six-six-keyboard/ http://longshotcity.com/2009/05/27/the-six-six-keyboard/#comments Wed, 27 May 2009 23:58:35 +0000 craigrmeyer http://longshotcity.com/?p=678 ]]>

So get a load of this.  I wanted to do some simple playing along to my favorite Oasis and Tears for Fears songs.  Play what?  Well, I tried guitar classes, but man is guitar hard.  So how about a musical keyboard?

I had actually taken a basic piano class across the street from Harvey Mudd at Scripps College (where the girls were), and was indignant to learn how the conventional piano’s “seven-five” (seven white keys, five black keys) layout meant that a C-major chord, while embodying the exact same sequence of half-steps between notes as a B-major chord, for instance, ended up looking very different.  Bullcrap!

The sequence of four, and then three, half-steps between the notes in a major chord is an easy concept to learn and understand, but that doesn't mean that all major chords look remotely the same!

The same goes for scales.  Playing a C-major scale is easy, but an A-major scale is more complicated, even though the sequence of half-steps is exactly the dingdang same:

Same thing with scales. Even though all major scales are the same series of half-steps, they look very different. Learn one learn them all? Nope!

So how about this.  How about a “six-six” keyboard, with six white keys and six black keys per octave?  That way, the geometric patterns (and the shape necessarily made by one’s hand) between keys that correspond to half-step interval patterns will be consistent, regardless of where you’re starting from:

Aha, now that's more like it. The same half-step pattern corresponds to the same geometrical pattern between keys, wherever you start from!

Now we’re talking.

What’s weird now is that the “white” keys are no longer always the “natural” (as opposed to “flat” and “sharp”) keys.  The C, D and E keys look the same as before, but F, G, A and B are black keys now.

It’s all the same notes, though.  All the same notes.

Bingo! I took the brain of a cheap Midiman MIDI controller and figured out how to re-wire it to a new set of key switches. (Now in a storage room at Cornish College of the Arts).

So I got a cheap Midiman keyboard and figured out to wire its brains to a new set of Cherry keyboard keys.  I water-jet cut the “white keys” from a sheet of fiberglass panel and glued the black keys down.

In triumph, I sat on the floor in my underwear for an entire Saturday and played along to my favorite songs with the help of some guitar tabs from the internet.  The regular geometric pattern of the keys meant that most of the time, when I intuitively reached out and played a chord, I actually got it right, like I’m Elton John!  Victory lap!

tinyurl.com/gnunits

Step 1

Step 2

Yesyesyes!

And a remaining mystery, to me anyway, was the question of how the hell to hook it to a ship in a safe and inexpensive way.  I was assuming that some kind of harness contraption would have to be bolted/welded/strapped to the boat to allow the ParaTow to attach to the ship in one place.

And that’s probably true… if I wanted to hook to the ship in one place.

But!

Take a look at this.  There are these thingies on ships called bollards.  They’re called bollards whether they’re part of a ship or part of a dock.  They’re the hard points where you tie on ropes or chains.

Bollard (I think on a ship, but I can't tell for sure)

Bollards on a dock.

Okay.  So.  I finally decided to ask just how much load these things were built to take, and then compare that to how much tension a ParaTow will be exherting on a ship to pull it around at full speed.

I couldn’t figure that out, actually, but I did figure out that the “bollard pull” of normal harbor tugboats (how hard they can yank on a ship’s bollard through a long rope) is around 50 tons.  Okay.

Further, the bollard pull of an oceangoing tugboat (basically, a tow truck for ships that break down at sea) is around 100 tons.  Okay-okay.

So great.  We know that ships’ bollards, and therefore the structure underneath supporting them, are built to take somewhere between 50 tons and 100 tons of force safely.  Okay.

So how many tons must a ParaTow exhert in order to pull the ship at full speed?  If power = force x speed, then force = power/speed, and the million-dollar linux utility “units” will spell it out for us.  For reference, a common Panamax cargo ship goes about 20 knots and has an engine no bigger than 50,000 horsepower, so:

You have: 50000 hp / 20 knot You want: tonf * 407.33261 / 0.0024549962

Aha, so about 400 tons of thrust.

Well then, if a ship’s bollard is easily good for 50 tons of oomph, then we’d (theoretically) only need to hook to eight of them (four on the left side plus four on the right side) in order to safely yank this thing along at full speed.

The good news is that according to the pictures I’ve found in Ships Monthly magazine, they all have at least ten bollards up front.

So what do you know, there it is!  I’m imagining some kind of super-tugboat platform with not just one winch and tow line, but ten or so.  Their relative lengths are tuned to the geometry of the given customer vessel, and it goes through some procedure to let the ship haul up each of them and loop it over the bollard in question.

So wow.  The real world is never as simple as the sixth-grade math in a casual blog post, but the basic message is still loud and clear: When working together, the bow bollards on a ship are together rated for the same range of cumulative line tension as a ParaTow needs to route into the ship’s structure.

So done intelligently, it’s looking possible to demonstrate the ParaTow concept at full scale without having to add new structure to the ship (what I think most of you have suspected all along, but I was trying to make complicated).  Wow!  Let’s hear it for logic!

Wow! I am ever so impressed by the volume, thoughtfulness and compassion in your comments to this one.  I’ve really pulled you mofo’s out of the woodwork. 

My experience with Mars Hill Church, now into only its third week, can be classified anywhere between the endpoints of A) being gifted eternal life and freedom by the salvation of Jesus, and B) being psychically metabolized by a cult.

I just have no idea where along the spectrum I am.  No clue.  Manhattan Island?  The Golden Gate Bridge?  Oklahoma City?  Tulsa?  Beats the goddamn out of me.

Once I get me some 20-20 hindsight it’ll make sense and I’ll tell you all about it.  Until then, thank you all for holding my hand in your little ways.  –Craig

——————————–

And now for something completely different.  If you don’t like to see people get bewildered and blubbery then Control-W this tab right now.

“Probably just one of those cry-for-help type things.” –Marla, Fight Club.

Can we talk about this?  I need to talk about this.

I went to church on Sunday.  Yes, church, as in Jesus church, and I’ve been a mess ever since.

I write you good and thoughtful people today to ask if you’ve had any kind of experience like mine, what it was like for you, how you made sense of it and what happened next.

The place is called Mars Hill Church (www.MarsHillChurch.org), and perhaps you’ve already heard about them.  The place is famous in certain circles.  They’re getting a lot of public flack nowadays for denouncing homosexuality, as well they fricking should, because come on people, Iran is that way.

“So why the hell’d you go in there, dumbass?” Yyyeah.  I’ll get to that.

I’d ridden my bicycle past their Ballard (a neighbordhood in Seattle) “campus” about a thousand times.  They have a bunch of “campuses” now, but Ballard is the O-G-rigional and the biggest.  No cross, no steeple, no stained glass, no funny-font sign, no nothing.  Were it not for the word c-h-u-r-c-h spelled out on the understated moderne sign, I’d have assumed it was an overpriced architecture firm or something.

Exterior shot, Mars Hill Church in Ballard, Seattle.

I’d been thinking about going in there for months because, to break it on down for a second, I was lonely.  The only groups of other humans (since college) in which I’d ever found myself were organized around either money, music and/or alcohol, and now that I’m 34 (where’s my cane?) I just can’t keep up with that hampster-wheel anygoddamnedmore.

And not just lonely from other people, but lonely from… something else.

To tell you the honest truth, I do not like the word “Jesus.”  I don’t like to hear it and I really don’t like to say it.  I have better Pavlovian associations with words like “murder” and “poison.”  Words like those I can say without wincing, but not “Jesus.”  All my life it’s been a stupid-person word, an ignorant-person word, the domain of charlatans and suckers like:

• George W. Bush
• Oral Roberts
• Jim Bakker
• Pat Robertson
• Jerry Fallwell
• The Ku Klux Klan
• Baby-killing conquistators
• People who honestly believe that the world is flat, 8000 years old, or that Adam and Eve actually existed, like in Sumeria or Utah or someplace

I mean seriously.  You have got to be kidding.

This sort of thinking just doesn’t work at my socio-econo-educational level.  We know too much.  Fossils, infrared background radiation, carbon-14 decay, you name it.

I had a friend in Engineering college named Luke.  He was a Christian, in my Freshman group and always honest and nice to me, and I was to him.  Fellow red-staters, we had things to talk about.  But we drifted in our different directions over the few years, and then the next thing I knew, he jumped off the library and killed himself Junior year.  Not a good sign.

But there’s more to it than that.  The plot thickens as complexity reveals itself:

I’ve also seen and heard the worlds “Jesus” and “love” in very close proximity over the years, and was both intrigued and repulsed.  I’ve expressed my feelings about the J-word above, so let me expound on the L-word now.

I’d never heard someone say they love me without feeling either guilty or suspicious.  I’ve never gotten some award or honor or compliment that I felt.  Straight-A’s?  Perfect attendance?  Yeah thanks, whatever.  Even when a girl would tell me [and it has happened --Craig's ego], I’d just withdraw, feel ashamed and think “Dammit…  my next victim.”

And that really sucks.  That really really sucks.  I know I have potential, and I know I can do good and important things, but this nagging sense of “No One Cares,” despite all objective and sworn evidence to the contrary, has held me back like a ball and chain for my entire sentient life (and don’t one of you motherfuckers make like you don’t know what I’m talking about, if only just a little, please please please).

And why this church?  Well, I’d visited the local Unitarian Universalist joint here in Seattle some years ago, and found it just boring, not unlike the UU church I’d been raised in back in Muncie, Indiana.  Perfectly nice and intelligent and informed and pleasant people, but frankly just not enough to get up in the morning every Sunday on a consistent basis.

And besides, at least I knew where Mars Hill was, and when to show up, because it says so right there on the sign.  I also knew that they were growing, and I’d heard that it was the youngest church in essentially the whole country.  That helped assuage my expectation of boringness too.

And I’d watched some videos on their website, www.MarsHillChurch.org, right there on the front page, including one called “Jesus Versus Religion” that really surprised me.

Saywhuh!?  Jesus Versus Religion?  The heck is going on here?

(Also, if you watch the YouTube, you’ll see the equally surprising and impressive “Why I Hate Religion.”)

I was also superficially intrigued, quite honestly, by this hip/neuvoux outfit in which they’ve dressed up what is essentially… uh… evangelical christianity (Craig sucks in through his teeth).  Homeboy “Pastor Mark” doesn’t even shave regularly, rolls to service directly from the Abercrombie and Fitch dressing room, and does his hair up with goop into a faux-hawk.  What.  The.  Hell.

And I’ve always loved black gospel music.

And religious country songs always choke me up a little.

And I still reflexively say “the lord” from time to time in conversation.

And Pastor Mark’s video sermon-ettes really touched me, right smack on that pre-verbal bulls-eye that waits, ever so vulnerably, within the protective fences of math, language and logic.  He asserts things like:

• There is such thing as morality.
• There is such thing as safety.
• There are differences between the sexes, and that’s a good thing.
• There’s Right and there’s Wrong, and Wrong will fuck you up every time.
• There is such a thing as love for no reason.

I mean dangit, this guy is either a perfect sociopathic genius or he’s… something else I don’t have the ready words for.

So yes:

• I’m an engineer,
• I got a B average at Harvey Mudd College,
• I’ve designed thermal and electronic components for NASA (that worked!)
• I started a company that now employs six with health insurance and everything,
• I wash, shave and dress myself every morning,
• I’m good at algebra, trigonometry and calculus,
• I got an 800 on my math GRE test, 640 verbal,
• I can find most countries on a world map,
• I’ve traveled to foreign countries,
• and…
• I felt the need to go into Mars Hill Church last Sunday.

So yeah.  Here we go.  Don’t look at anyone.  Act like it’s no big deal…

…

Ho!  Lee!  Crap!  It was like Def Leppard in there!

They have a band (guitar, singer, violin, drums and organ) just like James Brown’s church in the Blues Brothers.  They have five or six big-screen high-definition projection TV’s hanging from the ceiling, upon which they play a Powerpoint slide show of the lyrics alongside various inspirational clip-art like:

• The highway into the desert
• The cloud-obscured mountaintop
• The stairway up into the light of day

…so they don’t need no hymnals!  You just read the words right off the screen!

And then the lights go down and they play, on the TV’s, a little five-minute film noir movie about a woman riding around in a big Cadillac with a uniformed driver wearing a ring that says “hypocrite”.  They stop at a stoplight that says “worldliness.”  She gets out and walks into a seedy office building with a neon sign that says “SIN” and up the stairs to an office door with the crinkled-glass window (just like Humphrey Bogart’s offices) upon which is painted “The Trial: 8 Witnesses.  James 1-2″.  Because that’s the theme for the next eight months.  They give away a half-inch-thick study guide and everything.

Holy moly.  This must be what funding looks like!

And then the lights come up and there’s Pastor Mark Driscoll Himself.  And he preaches.  I honestly can’t remember most of it because my head was spinning with a general mental din of What The Hell Is Going On Here?

He’s dressed up in a black and white suit like a lawyer, because “God puts us through many trials to make us better Christians, and I’m your attorney.”  The stage is made up like a movie set of a 30′s art-deco legal office.  I repeat: The stage is made up like a movie set.

And the place is packed.  I’d never seen a church filled beyond 50% capacity in my life.  They had to strategically remove the side-ropes from alongside blocks of chairs in order to pack the people into the front seats, the next block back, the next block behind, etc.

Maybe one out of ten or twenty people there had gray hair.  Tops.  In a church.  I couldn’t believe it.  I just couldn’t believe it.

And they’ve got these Fujifilm cameras following Pastor Mark around like he’s Bono, and I noticed that I’m mostly watching the nearby HD TV, not the man himself further away, because I can see him better on the TV.  I can see his face and his expressions.  How he wiggles his hands and eyebrows.

And then it hits me: They’ve got like ten churches now, all with the exact same service times, and it’s not just for “the consistency of the brand,” like Big Macs at every McDonalds.  Oh no.  (Have you got it yet?)  The people in the other churches (one for almost every neighborhood of Seattle)?  They’re watching TV’s too… exactly what I’m watching in here.  Real time.  Booyah.

Ho!  This place is the laser-guided GPS bunker-busting smart-bomb superweapon of meme warfare.  After all, the memes that win are the memes that:

• Replicate quickly (thus the smaller neighborhood churches)
• Replicate accurately (thus the TV’s)
• Replicate cheaply (no raw materials and they tithe like the dickens)
• Reject and kill off competing memes (thus the Bible-is-true-and-other-religions-are-wrong thing).

Wow.  Shock and Awe fo-real.

And I feel compelled toward the guy.  He draws a crowd for a reason.  He makes sense of my life in a way no one else has.

And..

And..

AND the crazy bastard insists that Adam and Eve were real.  And that the Bible is literally true, and that all the other holy books are wrong.

Dammit!  I’m going crazy!

Communion time.  More music, more slideshow lyrics.  Everyone gets up and does the thing, but I’d sat in the middle of my row so I don’t have to move.

I watch a young couple in front of me.  His arm is around her, her head is on his shoulder, and they get up and walk to communion holding hands.  I think of all the wonderful beautiful things I’ve been just so sure I could never have (also for no reason!), and then about the malignant sureness itself and If Only If Only and that’s it, I’ve had it.  I can’t take it anymore and bust up crying.

And then the other pastor comes out with his day-three beard, emo plastic eyeglasses and zip-up hoodie sweatshirt telling us all how much he loves us, and here are today’s announcements.

I sit in my chair for a half-hour after it’s over, expressionless.  I’m affected, okay?

I find the Visitor Center (of course there’s a Visitor Center), drink their coffee and eat their cupcakes.  I turn to the nearest name tag, Deacon Joe, and I just let him have it as best I can.   I really appreciate this, but what the heck is up with that?  And we talk for two hours.  And he gives me a book (“Vintage Jesus”, in which Pastor Mark explains how certain parts of the Bible prove why other parts of the same Bible are true, help me Jesus help me).  As I finish my last cupcake Deacon Joe puts his hand on my shoulder and prays for me.  And I let him.  Because I’m grateful anyway, no bullshit.  And Deacon Joe goes to his meeting.  And I go to the grocery store.  I’ve been in there for four hours.

…

And I’m angry.

I’m angry for being so weak as to get sucked in there at all, and for wanting to go back again too.  I’m angry for being asked to sell out my knowledge and intelligence and denouce my gay friends, who have always been there for me and been so much more generous towards me than I’ve been toward them, just to have a community that I can come to at a regular time and says it cares about me… (and also collects tithes).

I’m angry for not being smart enough to… to find a better way through life that works, makes sense and doesn’t ask me to be dishonest.

…and that’s it.  I’m just exhausted.  I’ll keep you posted.  It’ll make sense later. I apologize for putting anyone off, but I felt the need to come clean about this somehow, and my co-workers are not into this sort of thing at all.  WhatEVER you feel like sharing I would very much appreciate.

“It’s been emotional.”  –Big Chris, Lock Stock and Two Smoking Barrels.

(Viva Italiana... lordy.)

Let’s hear it for standards again.  I wish it were my idea, but nope.  Give it up.

A solar-powered light that uses your Nalgene bottle as a sort of diffuser.

Standards standards standards!  Let’s hear it for standards!

This is a solar-powered LED doohickey that you hang from your backpack or whereever to recharge during the day.  At night, you screw it onto your Nalgene bottle and it uses the bottle as a sort of diffuser/desk lamp.

What a trick.  I just had to pass this one on.

Well.  Last night all was revealed when I witnessed four, count ‘em one-two-three-four, 737 bodies, just sitting there, hovering above the rail cars by their cradle brackets.  Each of the bodies must have been worth at least twenty million dollars.  I could have walked up and touched them, or peeled off the tape around the orifice plugs and climbed inside.

An eccentric fellow who hangs around there explained to me how the Boeing people have to carefully inspect the bodies for bullet holes upon arrival, one square inch at a time, because rednecks along the way like to shoot for the windows.

Here's one of the 737 cradle cars sitting unloaded. I took this picture (yay iPhone!) two days later, and thus the better light. There are two brackets. A first one grips the landing gear in front, and a bigger one halfway back bolts onto the fuselage as if it were the wings. The steel "fence" in front whacks away bushes and stuff, and the big box in the back must be for... uh... for carrying other bits that go along with it.

Four 737 bodies, assembled in Kansas, at the Magnolia railyard awaiting final transport to Everett Washington, where they'll be joined with their wings and tailfins.

Closer up on one of the 737 bodies sitting on its its special rail car. Notice the special-purpose black plastic plugs used to block various orifices over which other elements like tailfins or wings will later be bolted. Otherwise, critters will move into it along the way.

Another angle on the same. Note the steel fence in front for whacking away what bushes and weeds grow into the rail car's path and prevent their whacking the 737 instead.