CoytAW

i keep hearing about glow engines. are they the same as other gas engines or are they the only gas engines? i have had people tell me all sorts of different things. im very confused.

da Rock

Glow is a term that usually applies to alcohol/oil fuel that in the United States usually includes nitro.
When electric motors came along, there wasn't much problem even when they became popular and common place.
But when people started building what was first called "quarter scale" they started using converted weed eater and chainsaw engines that ran on gasoline.

And using the term "gas" to describe any liquid fuel engine was no longer a good, clear way to communicate.

But people still refer to liquid fuel as gas.

And it's going to get worse, because the automobile industry is developing cars that run on alcohol based fuel. Oh man, is it going to be a mess when those things start running on glow fuel. They're already running on electricity.

da Rock

BTW, the term "glow fuel" sorta came from the fact that our model engines that ran on alcohol needed glow plugs to run.

And our first model engines actually did run on gas and use small spark plugs. But modeling quickly switched to glow fuel. And during the switch over back then, modelers had the same problem with their terms.

downunder

There are 3 different types of model engines generally used and each has got their own commonly used name so we know what they are and what fuel they use.

The first type is spark ignition which uses gasoline (called petrol outside of America) and of course that gets shortened to just "gas". Outside of America gas is only used when referring to LPG (Liquified Petroleum Gas for cars) and house heating.

The second type is glow ignition which uses methanol as the basic fuel but because they use a glow plug to ignite the methanol then they're commonly called glow engines. Outside of America no glow engine is called a "gas" engine.

To confuse things even more, you're likely to hear of "nitro" engines. This is very common with the glow engines used in RC cars because they like to use lots of nitro in the basic fuel which is still just methanol. But nitro sounds powerful and it didn't take long for the advertisers to catch on that kids love the idea of power so even the big glossy ads in magazines talk about "nitro" engines and then they sell lots of expensive high nitro fuels to them . Just remember that a "nitro" engine is only a glow engine.

The third type is what we call a diesel but isn't strictly a true diesel, it's just easier to say than "compression ignition" . These use a fuel made with oil/kerosene/ether and don't use any source of ignition other than heating up the air by compressing it very quickly.

B.L.E.

As a general rule, gas dominates in planes with 80 inch wingspans or more. A gas powered plane with a 72 inch wingspan is a small gas plane. Glow is used in smaller planes. The trainers you will learn to fly with will probably be powered by a .40 or .46 cubic inch glow engine. Cox once made a tiny little .010 cubic inch engine that's now a collector's item.

Below 20cc (1.2 cubic inches), glow ignition dominates. There are smaller gas engines but they aren't common.
Between 20 and 30cc, it can be either one.
Above 30cc, gas dominates. There are glow engines bigger than 30cc but they aren't common.