Cooling an engine

[chizz]

Hi all I am designing and engine and probably going to incorporate a Fan in it some where or design that element into the flywheel.

But my question is what is everybody's view on a Fan should it be blowing on the area you want to cool or is it better to draw the hot air away?

Thanks

Chizz

 

[BronxFigs]

I am interested in model engines that are designed to be air-cooled. If the engine is isolated, and displayed, and not used for it's intended purpose, like powering a plane, will there be enough cooling for running it without a high-powered fan blowing across the cooling fins? I have read that model, Hit-and-Miss engines will rarely overheat, but air-cooled, glow-plug engines, etc....what about them?

Frank

 

[Septic]

Fan blades machined into flywheels add greatly to the aesthetics and also contribute somewhat toward cooling, no matter which way the airflow is directed.

As for the necessity for extra cooling, that would depend on the intended use, number and configuration of cylinders, speed of rotation, cooling fin area, machining accuracy, fuel mixture, lubrication, running-in procedure to mention just a few variables.....

 

[chizz]

Thanks for all the info the engines cylinders will get pretty hot so to prolong the engines running it needs to be cooled.

 

[chizz]

Hi All,

Made the flywheel in brass and ali ans im not sure which weight will work better, here are a couple of pictures.

chizz

 

[johnny1320]

Air cooled engines that are fan cooled usually are shrouded and the air is drawn in from the flywheels center and directed to the engines fins. weather that is the best way or the most practical way I am not sure. seems to me you need volume and I don't think small blades on the flywheel will be enough.

 

[chizz]

Thanks Johnny1320,

The engine i am designing was never intended to be cooled as it is a flame licker and it my design for a four cylinder one, so these fins were added if they make a marginal difference in moving the air then its better than nothing thanks for your input.

Chizz

 

[Coilmotorworks]

You do nice work. You can test the efficiency of the fan by slowly spinning the wheel and using a little smoke. My best guess on this design is that the tendency will be for the air to spill towards the rim than in line with the shaft.

 

[chizz]

Thanks Coilmotorworks,

you may be right just tried to fit some sort of fan detail on the flywheel within the capability of a 3 axis milling machine. It may end up just looking good but if it can a least move the air in some sort of fashion is probably better than nothing at all.

 

[Jasonb]

The old Mytags used something similar but the whole spoke was the fan blade.

http://www.homemodelenginemachinist.com/f14/up-right-maytag-18847/

 

[aarggh]

Love it Chizz! Looks great mate!

cheers, Ian

 

[BronxFigs]

Since this thread, and all the following Q and A are about engine cooling, I want to ask some very general questions:

If an model engine was designed to be water cooled, using a combination of a water jacket around the cylinder and/or water passages in the head, could I eliminate all the water cooling, pumps, radiator,etc. and convert the engine for air-cooling by adding cooling fins to the cylinder(s) and the head(s).

For example: The classic "Mastiff " is a 4 cylinder boxer, designed to be a water-cooled engine. Many multi-cylinder boxers are designed for air-cooling. I was wondering if I could add cooling fins around the cylinders add increase the mass in the heads, by adding more metal, and then milling cooling fins into the now thicker, heads. If this is done, how will I know if the engine is running too hot? Is there a formula for cooling fin area vs. cylinder diameter.

Some model engines can be built with the option of either being air-cooled, or, water-cooled. In certain engines, I don't see the big differences between either way to cool the engine. It's basically the same engine but it either uses a water jacket around the cylinder, or, cooling fins.

Do you think there is a huge temperature differential between the two systems of cooling.

Thanks for any information.


Frank