Herbie--there is a lot of information on that website. I know perhaps 2% of it. All of the information I have to give about the two gears is on the drawings. All in all, there are only really two critical factors. The gears must have a 2:1 ratio, and they must have a center to center distance of 0.9375". The center to center distance is arrived at by adding half of the pitch diameter of the 15 tooth gear (.3125") to half of the pitch diameter of the 30 tooth gear (.625"). I used two different gear cutters to cut them, a #7 for the 15 tooth and a #4 for the 30 tooth. The depth of cut is 0.090". I used my rotary table and divider plates to set the spacing in degrees between the cuts. (24* between cuts on the 15 tooth and 12* between cuts on the 30 tooth.) If you built the main body as per the dimensions I gave, the crankshaft and camshaft will be 0.9375" center to center, to accept these two gears. If I can help in any way, let me know.---Brian