atomic_fungus (atomic_fungus) wrote,
atomic_fungus
atomic_fungus

#2206: "Evil sludge" heh

Way down in the comments of this post came a term I'm going to remember:
I’ve occasionally had cars that can burn old gas just fine after as much as two or three years, and I once saw a 1926 fire engine that hadn’t moved in 40 years fire up on whatever evil sludge was in the tank — but I still wouldn’t want to take that gamble.
"Evil sludge" is a fantastic term for old, old gasoline. Next time I need to refer to gasoline of indeterminate age, that's what I'll say.

* * *

To be honest, 80 HP from a 1.4 liter engine--in 2010--would be pathetic in a regular car. My Escort, designed and built with 1980s technology, gets 88 HP from 1.9 liters. The Fiero's Iron Duke, displacing 2.5 liters, makes 95 HP. The Volt is better than either of them on a HP/liter basis, but not by very much considering the technology which ought to have gone into building the thing.

Honda's doing a hell of a lot better than that; the Honda Fit gets 109 HP from 1.5 liters. The 2001 Honda insight made 73 HP from 1 liter.

But the Volt isn't a regular car, and the horsepower figure really doesn't matter all that much. Understand, though: the engine in the Volt is designed to run at one speed, which is its most efficient speed and which probably is not the same as its speed at its horsepower peak. In fact, because you're turning a generator, you want to run the engine at its torque peak. So this "80 HP" stuff isn't as stupid as it sounds, because an engine which is designed to maximize torque typically won't make all that much horsepower, and vice-versa.

My Escort, again--its torque peak is at 3,800 RPM. When I bought the green 1995 Escort I also considered buying a Dodge Neon; the Dodge Neon had an engine which made more horsepower (132 versus the Escort's 88) and more torque (115 vs 105), so why did the Escort feel snappier?

It's because of how I drive: I don't flog engines. I rarely run any engine past 3,000 RPM and I think I went past 4,000 once in my green Escort. The Escort's torque peak was at 3,800; the Neon's was at 4,800. And the horsepower numbers were at similarly elevated engine speeds, which I would never (almost never) hit--and that's why the Neon felt dog slow to me compared with the Escort.

So if GM made a cam which optimizes torque around the generator's most efficient speed, it would make the horsepower output of the engine suffer, particularly if the engine wasn't made to turn out its best torque at a particularly high speed. If you want the engine's torque peak to come somewhere around, say, 2,500 RPM, the horsepower peak is going to be pretty low.

Because Government Motors had to produce this rapidly--to make their new overlords in the US federal government happy--they had to use an off-the-shelf engine from the parts bin. Otherwise they could have used a small turbodiesel (sub-liter displacement) which would sip fuel and pump out crazy amounts of torque. GM doesn't understand diesel engines all that well, much less diesel engines sized for econoboxes, which is why this 1.4 liter gasoline idiocy is the best they can do.

* * *

Okay, one more example: the 3 liter 4-cylinder engine in a Cessna 152 produces about 100 horsepower at 2,500 RPM, which is also its redline. But its torque at that speed is 210 lb-ft, which is an incredible amount of torque from a four-cylinder gasoline engine; torque is what you want because torque is what makes the propellor turn, even when it's loaded up with all kinds of aerodynamic forces.

Eh? "Why not diesel, then?" Because diesel engines are heavier than gasoline engines, and weight is king in airplanes. (You can get diesel engines for aircraft, yes. But Cessna went with what they knew; the 152 was designed in the 1950s, as I recall.)

* * *

Besides which, there's an old saying: "Horsepower sells cars; torque wins races." It's really not as simple as that, otherwise everyone would be using big honkin' diesel engines in race cars. Torque is what turns the wheels against friction and inertia; simply put, torque is acceleration.

What about horsepower? Horsepower measures the rate at which the engine can provide torque; horsepower is speed.

All the torque in the world won't do you any good if you can only get it at 1 RPM, and because the strength of materials has a practical limit you can forget about gearing up speed too far from there. But all the horsepower in the world is similarly useless if you can only get 1 lb-ft of torque. Again, the limit of material strength means you can't gear down far enough to get a decent amount of torque out.

So Indy cars tend to have engines which run at 11,000 RPM and make gobs of horsepower at that speed--1,000 is not unusual--but the actual torque figures are quite low by comparison. In that example, 477 lb-ft at 11,000 RPM. That's a lot of torque but it's not stellar; compare that to the horsepower and torque output of a top-fuel dragster engine, which typically produces around 6,000 lb-ft of torque and 8,000 HP.

* * *

Mechanical engineering is pretty interesting to me, because you come up against the physical limits of materials and components a lot more concretely than you do with electronics.

With electronics--at least to the piddling extent I've worked--you just don't see the give-and-take very much. Most of what I learned in tech school dealt with digital systems because almost no one is working with pure analog any more; and the standardization of component logic ICs have taken all the guesswork out of building circuits. You can connect X many inputs to a single output; your voltage will always be within a certain range; and if the circuit doesn't work the way you expected it's because you either evaluated your truth table incorrectly or else you made a bad connection somewhere.

You can teach a sufficiently bright junior high student to build useful circuits using digital logic. The rules are incredibly simple; the hard part is remembering what all the different symbols mean, and that's a piece of cake because there aren't very many of them to begin with. During my secondary school years I looked at the 7400 series logic ICs in the Radio Shack catalog (back when they had one) and was mystified by them; it looked complex and arcane.

...then I went to tech school and learned how f-ing simple 7400 series logic is, and felt cheated. I could have been doing neat things with digital circuits for years before college had I known how simple it is.

Build a clock--build a calculator--build circuits for the C-64 to control via its cartridge port--build WTF-ever came to mind. Shit.

In high school I looked at the block diagram of the C-64 that came in the official reference manual without really understanding how it worked; after college, I had occasion to look it over, and realized, "Okay, this is what that does; that's how the memory is addressed; this controls that--oh, crap, this is simple!" I could build one myself if I wanted to deal with the vagaries of wire-wrap circuitry.

That's the hell of it; the C-64 is simple. Shit, at most it's a two-layer circuit board. The memory is addressed with two bytes sent from the processor; you have two latching buffers to hold the address bytes until the memory operation is complete. I/O is handled similarly though (as I recall) I/O is handled on a different bus than memory. (I might be mixing that with what I learned about Intel processors. I can't remember. It's been more than a decade since I needed to.)

The hardest part of the whole thing to implement is the damn video circuitry, because that's analog; Commodore didn't bother with that, but just sourced an RF modulator unit from someone. Second-hardest is keeping noise out of the power bus, but you accomplish that with caps across Vcc and GND of the ICs anyway. No problem.

* * *

What I did manage to do in tech school was to buy a 5W amplifier module and build a small stereo system around it. The amp module needed only 12v input; having worked with AC circuits I was able to buy a transformer and bridge rectifier, and to build the appropriate AC-to-DC power convertor. I put it into a project box I had laying around, added knobs and external connectors; with the two 5" speakers I had built years before as aux speakers for my stereo, it made a quite nice amp unit for my computer's Sound Blaster Pro.

Unfortunately I lent it to a friend in Iowa, who lost it during one of his moves. Jerk.

* * *

It's kind of surprising to me that it can be as humid as it is now after we got two freakin' inches of rain today. I mean, the dewpoint is 78°; when you step outside the house it's like drowning in an electric blanket. Last summer was very cool; this summer is making up for it.

There certainly hasn't been any deficit of thunderstorms this year. If I had been capable of sentient thought around 5 AM this morning I would have gotten up and watched the rain come down; but my half-awake brain didn't connect "vivid lightning" and "monsoon". I got up to hit the can, saw the lightning, and thought, "Damn, that's a lot of lightning." Then I went back to bed. *sigh*

* * *

Anime:

Kimi ni Todoke is over. The last episode was perfect, the way the entire damn series has been. I really hope there's another series of this, but there probably will not be.

Started Arakawa Under the Bridge and had to watch ep 2 right after ep 1 because it's so damn weird. What's with the kappa dude? What's with the jerks in the masks? No, don't tell me; I'll find out sooner or later.

Ep 4 of Zettai Karen Children did not piss me off, so I'll watch ep 5. It's still on probation.

Ep 10 of To Aru Majutsu no Index has started another story arc. We'll see how fucked up Touma gets in this one. But it centers on Misaka Mikoto and--apparently--her robot double? I don't know, and won't know until I see more eps in this arc. But it's good stuff.

Ep 17 of K-ON!! downloaded in about ten minutes and I watched it; now I must wait for ep 18.

Either Working!! or Mayoi Neko Overrun will take KnT's place in the lineup, but I don't think either one can really replace it.

Yes, I'm going to watch it again.
Subscribe

  • #7607: Oh, yeah

    Had another opportunity today to play Pat Metheney's "Spring Ain't Here", because it snowed for most of the morning. But yeah, "global warming"…

  • #7606: LOOTING IS NOT PROTEST

    Some fatuous pinhead on the radio said that Chicago was ready for "looting and other forms of protest". But you know what? It's fine. We no longer…

  • #7605: I don't even need lettuce any longer

    See, the tacos I make at home blow away any tacos I've ever had anywhere else. Lettuce used to be necessary, but now it just gets in the way, so I…

  • Post a new comment

    Error

    default userpic

    Your reply will be screened

    Your IP address will be recorded 

    When you submit the form an invisible reCAPTCHA check will be performed.
    You must follow the Privacy Policy and Google Terms of use.
  • 0 comments