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Model aircraft engine pictures and information
Dismantling a 2 stroke SC25 model aircraft engine.
The engine shown here is a SC25 ABC (Aluminium piston, Brass liner with Chrome plating) fixed wing model aircraft engine dating from the late 90s but as yet unrun. The engine is fairly typical of most modern glowplug engines so is good to show many basic principles.
The main crankcase of the engine is a one piece, diecast aluminium alloy component incorporating housings for the crankshaft bearings and the cylinder. On this SC25 the casting quality is good with quite a fine finish, not quite up to the supreme standards of OS but plenty good enough.
Plain holes are drilled into the crankcase for bolting on the included silencer and the carburettor is mounted by the pinch bolt method.
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Looking down the cylinder of the engine with the cylinder head and liner removed. Here you can see the exhaust port at the top of the picture and the three inlet passages of the model engine where fuel mixture is forced upward.
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The engines backplate is fitted with a gasket and is attached with the usual four allen head machine screws. The alloy cylinder head is bolted onto the crankcase with six allen head screws, on this example the glowplug hole is plain aluminium (expensive engines often have bronze inserts for the glowplug to help avoid thread stripping).
The chrome plated brass cylinder liner came away with the head on this engine, no attempt at splitting these two components was made. The cylinder liner is the heart of any engine and is well made on this SC25.
ABC engine liners are slightly tapered towards the top to provide a good seal under compression, real precision stuff. A liner for use on a ringed model engine on the other hand in usually of the same internal diameter from top to bottom.
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The chrome plated brass cylinder liner with the engines cylinder head still attached.
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Another view of the liner and head.
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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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