![]() ![]() It also becomes a means of locating the cam on the shaft in relation to the other cams and there-by solves one of ETW's problems. This keyway and the bore now become an effective means of holding and locating the cam in the subsequent machining operations necessary to finish the profile. Therefore if a "keyway" were to be put in at this location, then it would act, as an indexing point and it would not weaken the cam in any way. It is along this centre line of the cam under the "nose" where most of the material is. Taking the centre line that passes through the "nose radius" of the cam, each flank radius is symmetrically disposed about this centre line. For my peace of mind, I wanted a more positive, engineered location method which cut out relying on my eyesight. Further I was not happy with aligning the cams "by eye" in a jig-although that is not saying that this method is not satisfactory. ![]() Although my design had only two cams I was not altogether happy with the nibbling aspect of forming the cam and subsequent hand finishing by filing. I had decided that the cams for the Side-valve engine would be hardened it was therefore decided to adopt LCM's built up camshaft approach which he used in the "Mastiff" engine. The reasons he did not adopt this method was he felt the angular relationship cam to cam would be difficult to maintain and the means of holding each cam in position. ETW also states in his construction article on the "Seal" that by far the quickest way to manufacture a camshaft was to make all the inlet and all the exhaust cams together. Many builders have gone down this route but have resorted to building specialist-grinding machines to rectify this distortion. If the entire camshaft is made from "Silver Steel" and hardened then distortion might present bearing alignment problems, especially on multi-cylinder engines. Whilst ETW's method of camshaft manufacture is and was ingenious at the time, it does not lend itself to making the cams with hardened surfaces easily. Most of the designs of Edgar T Westbury and L C Mason use cams which have a radial flank. It was whilst designing this engine that I hit upon the following method of producing the Cams. The answer is yes, but it lacked the docile nature of a petrol side-valve, and it will subsequently be converted to spark ignition. Again I wanted to see if a side-valve engine could be persuaded to run compression ignition style. ![]() I could think of no better way than to design and build an engine in order to keep my interest in the learning curve. My second engine, a side-valve, came about after a career change and the need to learn AutoCAD. Whilst it was originally designed and built to run on petrol, it has been successfully running "compression ignition" style on paraffin/kerosene-with a slight modification of course. Lastly, there was only one "Tangential" cam to make which was a simple rotary table job, the intake valve working on suction alone. Model hit and miss engine tips and tricks how to#The second was a technique on how to make the gear cutters necessary, which I have passed on in previous EIM articles. Three things about this design appealed to me one was the fact that the entire engine was made from "Odds and Ends" which is how the engine got its name. The first four-stroke engine I made was to an American design based on a single cylinder "Hit and Miss" horizontal engine. Model Engine News thanks both for their generosity and for helping to de-mystify what may at first appear a daunting task to would-be engine makers. It is reproduced here by permission of the magazine, and the author, Graham Meek. ![]() This article on making harmonic cams for miniature four-stroke internal combustion engines first appeared in the British magazine, Engineering in Miniature, March, 2009. ![]()
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