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Model aircraft engine pictures and information
Dismantling a 2 stroke SC25 model aircraft engine.
Plain aluminium alloy piston.
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The piston and conrod assembly of the model engine. Note the oil holes drilled into the big end of the conrod for oil supply to the bearing surfaces.
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The piston of the SC25 engine is a simple aluminium alloy unit with a flat crown and an almost centre mounted steel gudgeon pin.
The piston to liner fit is spot on with this example. Smooth as silk over the entire stroke but with quite a bit of nip as the piston approaches TDC which should provide an excellent gas tight seal as the engine is run in.
The gudgeon pin is fixed in position by a couple of wire clips, no end pads are fitted to the pin on this engine. The conrod is again made from aluminium alloy and has a bronze bush fitted to the big end. Oil holes are drilled into this for big end lubication.
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Ground finish on most of the surface of the crankshaft.
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The crankshaft is a nicely made steel component with a ground finish on most faces and a separately fitted crank pin. The crankshaft doubles up as a rotating inlet valve like on most model aircraft engines. The mixture passing through the carb into the opening on the crankshaft shown in the picture then onward through the centre of the shaft and out the rear hole into the crankcase.
The engine's crankshaft is supported on two unshielded ballraces which are pressed into the crankcase.
The prop driver uses the split taper cone method to fix itself securely onto the crankshaft. This works by gripping onto a slight taper on the crankshaft as the propeller is tightened down, once again this is precision machined.
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Taper cone type prop driver is fitted to this engine.
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SC25 model aircraft engine page 1
SC25 model aircraft engine page 2
SC25 model aircraft engine page 3
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