Monday, June 4, 2007

Sparkin' on the Cheap

Flying isn’t that hard. Birds fly. So do fish. Even insects. But if you wanna enjoy the thrill of powered flight you’ll probably need an engine and if it gets its power from burning gasoline then you gotta figger out some way to light the fire. Always been something of a problem, lighting the fire. Back during our Civil War they used what they called a ‘glow tube’ to light the fire. Closed brass or silver tube, closed end inside the combustion chamber, open out outside being heated by a kerosene or acetylene lamp. Actually worked, too. Engine put out nearly half a horsepower at about 100rpm and only weighed about 700 pounds.

State of the art, 1865.

Of course, soon as they had an engine, some kid wanted to make himself a motorsickle. Or mebbe a hot-rod.

Didn’t work too good. Soon as the thing started to move it would usually blow out the kerosene lamp, glow tube would cool off, engine would crap out. Ignition failure. Civil War motorcycle gang, Nazi helmets, Originals stiff as a board, lined up there on the side of the road... Hell of a problem.

Some guys used spark ignition. Low voltage, make & break stuff. But that meant a buncha batteries and they weren’t all that good back before we had the Energizer Bunny. Or they could generate their own lektrcity. Mike Whats-his-name... Faraday... had figgered out how to generate lektricity about thirty years before. All you had to do was twirly a coil of wire between the poles of a magnet and lektricity would magically appear in the coil. Unfortunately Civil War magnets weren’t any better than Civil War batteries. Just soft iron bars. Oh, you could magnetize the things but not very much nor for very long. If you wanted to produce the same amount of current you’d get from your bank of batteries you needed some humungous magnets, size of a wagon wheel. Magnets that big, your lektricity-maker ended up weighing about the same as the batteries, not only because you needed a lot of big soft iron magnets but because your coil was kinda fat. Big wire. And the insulation was just string or varnished thread wrapped around the wires, which pushed the wires pretty far apart so you needed a BIG coil to get any juice. And slip-rings, since you had to get the juice out of the coil once you made it.

Folks called it a ‘magneto’ because of the magnets, I guess. First ones weighed about a hundred pounds. But it actually worked and you ended up with an engine that was handier than steam because you didn’t ned a firebox and a boiler. Not a real handy engine, of course. Heavy as hell. Didn’t put out a lot of power and only ran at one speed. But the fire was all inside and there wasn’t any boiler to explode and you could run the thing yourself; didn’t need a certified Engineer.

Wasn’t a Hog of course but the thing did go. Bad as it was, it sold like hot-cakes since it cost less than a small steam-powered engine. And because it sold like hot-cakes a lot of people were building them. And improving them, too.

Twenty years goes by. Engines got smaller and more powerful. So did the magneto, thanks mostly to Elisha Gray, who developed a geared magneto that could produce nearly forty volts, thanks to stronger magnets, smaller wire, better insulation and those gears. That made the thing small enough to fit inside his telephones. Spin the crank, it could generate enough juice to trip the indicator down at Central, tell the operator you were on the line. Couldn’t use light bulbs because Edison hadn’t finished stealing the idea from Swan just yet but the solenoid-actuated ringdown indicator worked pretty good, assuming you weren’t too far from Central and the iron wire running along the fence posts wasn’t too rusty.

Better magneto made for a better engine but most real engines, like the ones in the trucks that could now be found all over Europe, still used glow tubes. Which sat the truck on fire now & then but glow tubes were more reliable than that silly Mag-Neat-Oh or that Make & Break method of generating the spark, rubbing the piston against the Sparking Rod inside the combustion chamber.

Stationary internal combustion engines had come even farther. Now that most towns had electric lighting they used a door bell arrangement to generate an alternating current that could be stepped-up by a transformer and fed to a spark plug, just as soon as they invented spark plugs. Didn’t work for those trucks, though. The vibrating reed-relay that buzzed those coils up to as much as five thousand volts was a real power hog and ran down your dry cells quick like a bunny.

Which is why the Wright brothers used Make & Break to light their fire. No spark plugs. Friction-drive magneto pressed into service as a dynamo, powered by putting a little wheel on the input shaft and letting it rub against the flywheel - - gave them about ten volts. Sparking bar inside the combustion chamber. Tried & true ignition system, having been in use for nearly fifty years by the time the Wright brothers flew. They’d heard about a new-fangled high-voltage magneto developed by a German outfit. Put out enough voltages to jump the gap on a spark plug, assuming you had spark plugs, which the Wright’s didn’t. Not at first.

Robert Bosch got into the magneto game in 1887 and made a pretty good magneto, although not very many of them. By 1896 he’d only sold a thousand of the things but he kept plowing the money back into the business, improving his product. Because everyone understood that if you wanted to make a hot-rod or a motorcycle you couldn’t afford the half-ton weight of the typical gasoline engine. Trucks, okay. But not motorcycles or flying machines or a Z-car. For that you needed a light engine. But it had to be a powerful light engine and all else being equal, that meant it would have to spin at a fantastic rate of speed, probably more than A THOUSAND REVOLUTIONS PER MINUTE, which was a lot faster than any engine was running at that time. Try running a Make&Break ignition at a thousand rpm, it’d break off the Sparking Rod or the insulated seal around the Sparking Rod gland-nut would leak even more than it already did and steal all your power. Carl Benz, a friend of Bob’s and another early car nut, referred to the ignition puzzle as “...the problem of all problems.” He said that in 1880 and odds are, he was still saying it in 1896. Nope. Couldn’t do it.

Actually, you could do it... if you used a sparking Plug with a fixed gap instead of Make & Break with its moveable Spark Rod with its variable gap. In fact, they’d already done it with stationary engines. But to jump the gap on a sparking Plug you needed thousands of volts, not just tens of volts. And while you could make that kind of voltage by plugging your ignition system into the wall, or powering a vibrator with a bank of batteries, nobody knew how to do that with a magneto.

Except for a guy named Gottlob Honold, who worked for Bob Bosch. And even Gottlob wasn’t sure he could do it, he just had this idea about how, maybe, it could be done, based on a couple of principles about inductance that Mike Faraday laid down fifty years before and some of the tricks Elisha Gray had come up with. Gottlob was lucky enough to be working for Bob, winding coils for those thousand pretty-good magnetos. Bosch who told him, Sure, take your best shot at it. Which Gottlob did, solving one problem after another over a span of five years or so until December of 1901 rolled around and he showed his boss a working model of a reliable, dependable magneto that put out enough juice to be used with a spark plug. “You really have hit the bulls-eye!” said Bosch. (But in German, of course.) By 1906 Bosch magnetos was bringing in over a million dollars a year, thanks to Gottlob Honold, who was given a raise and allowed to take Saturdays off.

What Gottlob had done was to put a transformer inside the magneto and to apply a couple of known but heretofore undeveloped electrical theories to make the transformer kick out a hot, blue-white spark exactly when needed, using an electrical switch driven by the magneto. Once the spark was generated it was connected to the proper spark plug via a rotary switch that was also driven by the magneto. The first switch, which controls the flow of juice to the primary side of the transformer, is what we today call the ‘points’ while the second switch, the one that directs the output of the secondary winding to the spark plug, is called the rotor and distributor cap.

Starting to sound familiar? Well, it should. Because the principle of spark ignition has remained pretty much the same right up to this day, despite something better having come along in the 1960's.

As soon as the Bosch high-tension magneto hit the market everyone started copying it. Or trying to improve on it. Like a young guy named Charles Franklin Kettering who worked for the National Cash Register Company in Dayton, Ohio. Which just happens to be where the Wright’s hailed from. In a sense, Dayton was the Silicon Valley of its day.

Magnetos were nice. Nice and expensive. Each was virtually hand-made. Their superb quality ensured their reliability but it also guaranteed the need for a high level of skill to maintain and repair them. They were a complete generating set and ignition system compressed in a tidy little package. And if any single part of that tidy little package went bad, the thing wouldn’t work and finding someone who knew how to fix it was roughly the same as for finding fur on a turtle.

But magnetos weren’t perfect. Since the amount of juice provided by the permanent magnet dynamo was proportional to the rotating speed of the coil, they were a bitch to hand-start. Once you got the buggy running things were okay. The faster it ran, the better the spark, up to the point where the electrical insulation began to break down. Hand-cranked on a cold morning? Forget it. Ford’s buzz-box ‘ignitors’ were the hands-down winner when it came to crank-starts because when you got right down to it, your horseless carriage was pretty much of a joke if you couldn’t start the thing. And for a lot of folks, crank-starting a car was about like programming their VCR.

Chuck Kettering thought about the problem for a while then decided to take the magneto apart. Instead of that niffty little permanent magnet dynamo to provide the juice he decided to run the thing off a big lead-acid car battery. To keep the battery charged you’d have to fit the engine with some kind of electrical generator but now that Edison had copied the light bulb folks were even using them on cars, not only to replace the blindingly expensive acetylene-powered driving lights but even for that new fad of having a light come on when you stepped on the brake. (Cute. But it’ll never catch on.) And besides, Chuck had a crazy idea about replacing the hand-crank with an electrically powered starter-motor, for which you’d need big battery... and some means of recharging it.

After tearing the magneto apart and spreading it around the table Chuck saw how you could retain the transformer principle that gave you such a nice hot spark while eliminating most of the complexity that made magnetos so expensive. Instead of building the transformer inside the magneto Chuck Kettering wound a new transformer, one you could bolt anywhere you wanted it. He put the points in a device driven off the engine’s cam. The points went into the bottom part of the thing. The top part was reserved for the task of distributing high voltage from the coil to the individual spark plugs, which everyone started calling the ‘distributor’ about ten seconds after Chuck invented the damn thing.

Now you had all the pieces of an effective spark-ignition system spread out where you could get at them. The components were larger and designed for mass production; no brains required. If a part of the system went bad, any damn fool, meaning you, could simply replaced that particular part and drive on. What you ended up with was a cheap, easily manufactured ignition system that was inexpensive, reasonably reliable, didn’t cost very much and took virtually no skill at all to maintain. And it was cheap. Best of all, it actually worked. (Did I mention it was cheap? Cuz it was, compared to a magneto.)

Genius or not, Charles Kettering hadn’t improved on the magneto in the electrical sense. Indeed, at high speed the Kettering ignition system doesn’t work nearly so well as a magneto. But boy did it make an engine easy to start! And it was cheap, too.

Auto makers loved it. At least, most of them. Ford stuck to his own patents. A fellow named Sloan, maker of a car he called the ‘Cadillac,’ took one look at Charles Kettering’s ignition system and said, “I take a million of them, please.” (Or words to that effect :-)

Which isn’t to say magnetos vanished. Far from it. But over the years the Kettering-type ignition system got better an’ better while magnetos stayed pretty much the same.

First big improvement was getting rid of that distributor with its rotor and graphite button and all them sparks as the thing whirled around. Just a year after Boss Kettering patented his ignition system a feller in England started using it on a two-cylinder motorsickle. What he did was to wind the coil with a center ground so that both ends of the secondary were hot. Snap the points, which you could now mount just about anywhere, and you got two sparks, one from each end of the winding. He wired the sparks to his two cylinders and roared off to win the Isle of Man.

Waaait a minute. Howz that gonna work, both cylinders firing at the SAME time. But the feller just smiled and roared off. From that day to this no one has been able to figure out how a Waste Spark ignition system works, largely because Auto Shop 101 doesn’t do a very good job of teaching how real engines work. But I’ll give you a hint: It doesn’t really matter what the other cylinder is doing when the spark fires. So long as that jug is near TDC on the compression cycle, then the engine will run... because if that jug is near TDC it means its twin is near TDC on the exhaust cycle, because that’s how Otto Cycle engines operate. The Good News is that you got to toss that damn distributor in the trash. You still had a set of points... somewhere. But they didn’t cause nearly so much trouble as that wonky distributor cap and rotor and having the ignition leads running all over the place.

That was in 1920, by the way.

In 1960 I built my first electronic ignition system and I wasn’t the first guy to do so (I hold a General Class ham radio ticket; hams are always fooling with stuff like that). Later on I built a capacitance-discharge ignition system. And a little while after that I built an ignition system that runs off a dilithium crystal, which worked great except those damn crystals became rare as hen’s teeth after they canceled ‘Star Trek.’

Nowadays they’re working on a spark plug that contains its own coil which also happens to be a fuel injector. But that can’t be right, according to Auto Shop 101 :-) It's also possible for someone building their own airplane to put together an ignition system that is more durable and more reliable than the traditional magneto. Wanna know how? Just stay tuned.


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