iskandar taib

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As I thought - pretty interesting reading. And they're a little less like model glowplugs than I thought. The tube is designed so that the exhaust gases within it act as a "gas spring" to keep the new charge from coming into immediate contact with the glow element - the charge only reaches the element when the pressure in the cylinder has reached the desired level. This is a little different than the way it works in a model glow engine, where the charge ignites when the pressure in the cylinder reaches a critical level, even though the charge is always in contact with the element. The Smartplug would then be more amenable to design for a specific situation. The third patent has to do with adjusting ignition timing for varying engine load and RPM. The element is put halfway up the tube, gases rushing by will tend to cool it. In this patent, they envision that the element is constantly being electrically heated, so they describe using a knock sensor to de-power the element as necessary.

I'm not really sold on glow plug ignition for big engines (cars, airplanes, etc.) because spark ignition is much simpler to control and far more precise when it comes to ignition timing. You can even control it by computer. But for our small engines, the weight saving is considerable.

Incidentally, I recall having an argument a while back (mainly with Darzeelon) about glow plugs and gasoline, where I mentioned Gottlieb Daimler's motorcycle that used a hot platinum tube for ignition. You used a bunsen burner to heat the tube before starting the engine, after the engine started you could remove the heater. Very much akin to hot bulb engines, except latter-day hot bulb engines run on heavy fuels which are injected into the bulb. In any case, it's mentioned on Wikipedia. I suppose it's a precursor to our present-day glowplugs.

http://en.wikipedia.org/wiki/Gottlieb_Daimler

Iskandar

iskandar taib

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Some interesting glow heads I got off ebay some time ago, see how many you can identify. Someone on another list told me what they were, there are some rare ones in there. Ignore the OS plugs on the top left, nothing remarkable about them.



The REALLY INTRERESTING part about all this - turn them upside down and you see:



All the plugs in the lower group are like this, plus the one that looks like a plain old Cox 325 on the top right hand corner.

I suspect this group of heads came out of someone's collection, and they were collected because of those elements.

Iskandar