air cooling options

[Perko7Participant @perko7]

Hi all, relatively ignorant on construction of miniature I/C engines, but was just wondering, i've seen all the photos, videos and posts about turning cooling fins on cylinder barrels of air-cooled engines and wondered if there was an easier way. As an example, the air conditioning industry uses pressed corrugated aluminium fins which are a tight fit over copper tube for nearly all heat exchangers, whether it be a condenser, cooling coil or heating coil. Similarly car radiators are nearly always pressed metal fins slid over the tubes containing the fluid to be cooled. I realise that I/C engine cylinders run a lot hotter, but has this construction method been tried for cylinder barrels and if so what were the results?

[Perko7Participant @perko7]

[Roger BParticipant @rogerb61624]

I think there are two main reasons why the cooling fins are machined in place on model IC engines:

The first is trying to achieve a prototypical look if the model is based on a full size engine.

The second is mechanical considerations. The cylinder barrels are usually fixed to the crankcase and the cylinder head is then fixed to the cylinder barrel. The barrel needs to be able to take these loads so the depths of the fins are often adjusted in these areas to allow for the fixings. There are some designs where the head fixing bolts go down into the crankcase which would remove this constraint.

[Clive HartlandParticipant @clivehartland94829]

If you are going to use an engine for powering a model plane any 'Prang' would most likley smash any flimsy finning.

I have only ever seen machined finning or cast in finning on model engines. But, water cooling is a possible option with an engine where a jacket is made surrounding the cylinder. This for model boats and scoops are used to get the water flowing.

Practically stick with machined finning and accept that design.

[KWILParticipant @kwil]

What's not easy about turning the cooling fins? They are just a series of parting type cuts with a narrow tool.

[Neil WyattModerator @neilwyatt]

Surely a cylinder barrel with fins and a liner is the exact equivalent?

IC engines need thicker fins for greater heat transfer and robustness so turning is the best way of making them.

Neil

[dean clarke 2Participant @deanclarke2]

You can also set up a gang saw in the milling machine to the correct thickness and gap etc and rotary mill them all in one go, way quicker and easier than turning each fin separately, especially if your making more than one cylinder head.

Just a thought.

cheers

Dean

[JasonBModerator @jasonb]

Gang sawing also allows you to make thinner fins as a parting tool will tend to push the fin on one side of the cut into the previous one which is why they are often made a bit on the thick side so can then be made thinner and heat transfer will still be OK to a point.

[Perko7Participant @perko7]

Thanks all for the various responses, seems like my 'easy way' idea is not too practical in actual use . Glad i asked the question though, you never know until you ask (as the saying goes….. )

Cheers.

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