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Chris Dunn,          Nowra, NSW, Australia          tarkey@optusnet.com.au        4/14/2007

Origianl design engine

The Engine is my design, there are no drawings other than some scratchings in a note book. It was first run in February 2007. The engine is 1.35" bore x 1.85" stroke. I should have made it smaller but I had some hollow cast iron on hand. I was inspired to build it by this web sight and by Joe Webster’s design (http://home.comcast.net/~Webster_engines/). Also by Jerry Howell's power house design. The bore is cast iron pressed into a aluminum cylinder, piston is aluminum with 2 cast iron rings. Over hung crank (old axel from some sort of mining machine) runs on 2 x 12 mm ball races. The big and little ends are plain phosphor bronze 1/2" and 1/4". Gudgeon is silver steel.

The cam was cut using Cam Cal from (http://modelenginenews.org/), 120 deg less tappet clearance. The engine is not really hit and miss as there is no governor etc it is throttled with a barrel type carbie. It is not balanced other than the 2 holes in the crank web and a brass counter weight, it vibrates quite violently if you let it rev to much. But it sounds nice at idle and drives the little alternator quite well. the carb is just open at idle. I oil the engine before every run, oil from the oilier drips through the piston at BDC and into a small hole in the little end. Some of this oil makes its way along the rod to the big end (and every were else). The longest it has run for is 30 minutes. As I said before it is more of a idle speed, about 250 rpm. it hunts a little at idle I believe this has something to do with the automatic inlet valve affecting carburetion. The head temperature is about 230 c measured near the exhaust guide. The engine was never meant to do useful work of course, but was meant to be a primer for more complex engines. There are several piston rings, valve guides and valves in the scrap box as the correct techniques were learnt.

Copyright 2007,  Florida Association of Model Engineers and engine builder as noted above, All rights reserved.