TBone2008

so what does it mean a Glow engine, how it differs from other gasoline engines ?

Scar

My Feedback: (3)

Glow engines run on a mixture of alcohol and oil. Ignition with a "glow plug" is catalytic, rather than spark ignited.

Best wishes,
Dave Olson

TBone2008

pros and cons !?

rcdude7

My Feedback: (264)

#1 Only needs a glow plug for ignition, that's why the glow plug was developed over 50 yrs ago.


Not to sound rude, but do you really want someone to type the history of the glow engine? They go back to the 1950's, maybe earlier........

MinnFlyer

My Feedback: (4)

Glow engines are lighter and can be made smaller, so they are used in most 90-size and smaller planes. Once you get into 120-size and above, I prefer to use Gas. They are less messy, and the fuel is a LOT cheaper. The down side to them is that they are heavier than their glow counterparts and you need different fuel lines and tank plugs, but for larger planes, I'll take gas any day!

wcmorrison

My Feedback: (2)

The Methanol reacts with the filament in the glow plug to keep it lit.  Initially, it is lit by using a battery, usually a volt and half battery.  Once the engine is running the methanol reacts with the platnum filament and it continues to glow, ergo glow plug.  That means no wires, no additional battery, etc. to be carried in the vehicle (model airplane or model car) to keep the glow plug lit while it is running.

The engine itself uses the lost method of lubrication.  That is the lubrication is in the fuel and goes through the combustion process.  Some of it is burned and the remainder is expelled overboard via the exhaust system.

The fuel is ususally a mix of 80% methanol and 20% oil (lubricant).  The most common oil is Castor oil derived from the Casto plant.  It is used in baking and as a laxitive.  Today one can also get synthetic oil too.  Most of the fuel now days is a blend of Castor, Synthetic and Methanol.

There are two basic types of engine, the two cycle and the four cycle.  The two cycle is simpler, more powerful  and cost less.  The four cycle is more complex, cost more but uses less fuel and sounds different. 

They are quite powerful for their size.  A .46 engine can develope about one horse power at 12,000 RPM.  The amount of power varies the RPM and  of course the cubic displacement of the engine.  Smaller engines produce less power, swing smaller propellers than the bgger ones. 

Before you get into them, read up on them.

Chip

earlwb

It's easier to refer to where someone else did all the work typing it up.
Here http://en.wikipedia.org/wiki/Glow_pl...odel_engine%29
and
http://en.wikipedia.org/wiki/Glow_fuel

coriolan

Ray Arden developed the Glow plug ignition in 1948:
http://www.craftsmanshipmuseum.com/arden.htm

AMB

Technically it could be considered a semi-diesel since no external source of ignition is required, however model diesels as we know them
run a fuel mixture of ether, kerosene and lube oil, the compression of the engine ignites the the ether hence no glow or sparkplug is used
martin

1QwkSport2.5r

Diesels are compression ignition engines, so I dont agree with even calling them semi-diesels since they aren't fired by compression alone. If anything, I'd consider them to be a catalytic engine since the glow plug has to be heated to get it started and (as said) the catalytic reaction keeps it running.

I'm not trying to be nitpicky, just so you know.

378

My Feedback: (4)

Compression does effect on ignition timing though. Not enough compression and, if it starts at all, the timing will be retarded to the point it won't make any power or rev for -beep-. Too much compression and the ignition advances to the point of detonation, you may get lots of power if it's screaming along at the far top end but it's firing way too early for the low-end.


So yeah, I'd say glow engines are semi-diesels. They're like diesels in that the compression directly affects the ignition, but they aren't in that they don't use compression as their sole means of ignition. It's just like a hot bulb engine, only the hot spot is kept hot catalytically instead of just by latent combustion heat.

1QwkSport2.5r

But to call it even a semi-diesel is misleading because the definition of a diesel is (more or less) compression ignition. Glow engines do not operate by compression alone to ignite the fuel. The level of compression an engine has will effect power output, idle quality, and rpm.. but it is not the reason the engine operates as it does. The glow plug and fuel mixture control the point of ignition in a glow engine whereas a diesel is controlled by fuel mixture and contra piston position. Moreover, a glow engine's combustion is already done or darn close by the time the piston reaches TDC, whereas a diesel's combustion event is done at or just after TDC - similar to a 4-stroke. Ever run a glow engine "open faced" or without a muffler? You'll see flames coming out of the exhaust port. You won't see that on a model diesel.

378

My Feedback: (4)

By that definition hot bulb engines aren't semi-diesels either. They operate pretty much the same way glow engines do, a hot spot igniting the fuel/air mixture when the piston nears TDC with ignition timing controlled by compression, only instead of a catalytic reaction latent combustion heat keeps the hotspot hot.



Guess everyone's been mislabelling those for over a hundred years, eh?



I consider glow engines compression ignition because without compression you have no ignition. A worn out gasser still has spark, even if there's a hole in the piston crown, but a worn out glow engine simply will not fire without outside assistance because there isn't sufficient compression. Ignition may not initiate entirely from compression, but ignition is directly controlled by compression and is dependent on compression to exist in these engines.

1QwkSport2.5r

I'll agree to disagree and leave it at that.

cutaway

Engineers refer to glow plug engines as hot head diesels.

the pope

I thought a glow engine meant they glow in the dark. Is this not right ? Cheers the pope

mike109

G'day Pope

They do "glow in the dark". Years ago when I was a lad flying control line, I was flying a model of some sort right on dusk. In those days we did not use mufflers and I could see into the exhaust port of my OS 15 II and it was clearly glowing in the dark.

Cheers

Mike

Turk1

Also a diesel cycle have to be "constant pressure cycle"/http://en.wikipedia.org/wiki/Diesel_cycle
but our self ignition glow engines all are having otto cycle which is a "constant volume" cycle http://en.wikipedia.org/wiki/Otto_cycle

Diesel Fan

In the strictest sense modellers do not use 'diesel' engines, they are technically 'homogenious charge combustion igntion' engines or HCCI.

Diesels are hot air ignition engines (and thats caused by the extreme compression alone) with an injected charge.

Glows are catalytic combined with more modest compression.

Model 'diesels' use the same technique as real diesels with heat caused by compression alone but have they charge premixed with the air just as glows do.

Confused yet?

NoOneFlysAtMyClub

My Feedback: (32)

Bet you wish you never asked.

Tony

the pope

Say what ?

Rudolph Hart

I'm with tony mate!,interesting reading tho.

rowdog_14

My Feedback: (5)

Why did we even bring up diesel he asked about Glow

I am going to run behind MinnFlyer and give you direct input...
I agree with MinnFlyer, I have two OS 160FX(1.60) engines and a Supertigre 2300(1.40) engine and they drink nitro like there is no tomorrow.

One question I might ask is what type of planes are you looking to fly? Sport, scale, warbirds, ...this will help compile a list of pros and cons.

Pros:
They are lighter(especially 4 stroke glow)
Produce more power than a gas engine of the same size
Great on small and medium planes
...there are a few more personal pros for me.

Cons:
*They are light, putting in a larger/scale plane could cause balance issues and may require adding a lot of dead weight to the plane
*The fuel cost $18-$30+- a gallon
* If you have a large glow 120 or bigger you can use a gallon up in one weekend
* If you have a small glow and fly about 4-10 flights a weekend/week you could possibly only use about 2-3 gallons a year.
*If you do go glow for medium/larger plane the glow engine sometimes cost more than a Gas engine
*Engines are costing more while gas engine are coming down in price

I have all Glow engine and love them, I plan on buying a Gas but only when I get my 31% Comp Arf Gee Bee. I love glow, and I love the cost saving for Gas I just do not have any

Hope this helps a little

pe reivers

you have:
spark ignition engines (gas or methanol for fuel)
glow ignition engines (AKA glow engines, using a glow plug and methanol as fuel)
self ignition engines (AKA diesels in model engine use. They do not inject fuel into the combustion chamber, combustion pressure is peaky)
Self ignition engines, (true diesels, which inject the fuel at the end of the compression stroke. Ideally, combustion pressure remains constant.)

RoyR

As a kid I had control line models with the Cox 049. That's the way I checked my battery, with the piston down you could see the glow plug reflecting through the ports. And of course when it was running you could see the glow.