OF ALL THE TYPES OF RC PLANE ENGINES AVAILABLE THE 4-STROKE GLOW OFFERS MANY ADVANTAGES.
The 4-stroke glow engine shares many similar features to the 2-stroke with the obvious exception of the valve design. As with any 4-stroke the rc airplane 4-stroke has pushrods, rocker arms and valves. (Usually one inlet and one exhaust per cylinder).
Unlike the 4-stroke in your car, the model version does not have a separate oil supply but uses oil in the fuel, for lubrication.
The 4-stroke ignition system fires on every second stroke so in theory the 4-stroke is not as powerful as a same size 2-stroke. In reality, development of the modern 4-stroke has increased the power output to high levels, closing the "power gap" between 2 and 4-stroke rc plane engines.
The advantages of the 4-stroke are a more realistic sound and better fuel consumption. They also tend to swing a larger propeller at a lower RPM which can be an advantage on some models.
The disadvantages are increased weight and they do require a little more maintenance.
Maintenance is similar to 2-stroke RC plane engines. For information on 2-stroke RC model airplane engines, visit this page. The exception is that the valve to rocker arm clearances need to be adjusted now and then.
Most new engines come with an adjustment kit, consisting of a special tappet wrench and a feeler gauge.
The manufacturer's instructions will describe the procedure and recommend how often to check the clearances,
The range of sizes generally available is from 0.3cu. in.(5cc) to 4.5cu.in.(74cc) and maybe larger. As well as single cylinder engines there are a range of multi-cylinder types available. The multi-cylinder arrangements can be inline twin, v-twin, boxer twin, radial etc. In fact almost any full size engine configuration is available as a model glow engine.
This is the OS FT 160 twin cylinder glow. I flew one of these for many years and it is still going strong in a flying buddies plane.
Easy starting, powerful and produces a glorious sound!
Visit the OS web site for details of all 4-stroke glow engines available.
Here we have the Saito FA 325 R5. A 5 cylinder radial of 3.25 cu. in. (53cc) capacity. Note that is has the Saito usual 2-plugs per cylinder for a total of 10!
These multi-cylinder beauties are gems of engineering and manufacturing and sound glorious when running! Needless to say, they do require an experienced touch and are definitely not recommended for the beginner!
Once again the procedure for a 4-stroke is very similar to the 2-stroke system. One possible exception could be the method of choking. Many 4-stroke engines have a choking device added on to the carburetor. This is especially helpful when the carburetor is mounted at the rear of the engine.
One tip I would like to pass on regarding the type of glow plug to use. I only use the OS Type F plug. I have found this plug to be very reliable and have a long life. It is expensive but I like to use it in my 2-stroke and 4-stroke engines and have had excellent results.