Propwash April 2019 web.pub

The bath must be maintained at 125* to 135* F. The clearance between the anode's OD and the cylinders ID is approximately .250" (6 mm). You will want to make this distance as small as possible and still allow for an adequate space for the chromic acid/ sulfate solution. For larger diameter bores it will be necessary to have several anodes or a machined cast anode. The anode could also be made in the form of a hollow cylinder closed at both ends. The anode I use for the 1.125” (29 mm) bore is cast in a mold and then machined to size. The length of the anode should be about the same as the The Nitro Engine Part 2 By Lohring Miller NAMBA Safety Chairman Last issue we looked at how the modern, high performance nitro engine developed. The next parts will be about their construction. A long time ago I had a discussion with noted engine tuner Glen Dye. He stated that the most important factor in engine power was the piston and sleeve fit. Today’s engines use either ABC (aluminum pistons with brass chromed sleeves) or AAC (aluminum pistons with chromed aluminum sleeves) construction. The high silicon pistons (SAE 4032 or similar) have close to the same expansion as SAE 360 free machining brass. That way the fit remains close as the temperature increases. I’m going to use edited versions of Jim Allen’s description of the piston and sleeve manufacturing process used for his and Aero Precision’s (the maker of Nelson racing engines) engines. Both aluminum and brass can be efficiently and easily plated with properly designed fixtures in the basic chromic acid/sulfate bath. Finishing of chrome plated cylinder bores needs to be done by honing or grinding. One important part of the chroming tank is the lead antimony anode. It needs to be placed in the center of the cylinder's bore to ensure that an equal amount of chrome is plated on the cylinder's ID. Chrome tanks have very poor throwing ability which means a very high current density and closeness of the anode to the part being plated are necessary. The photos show the casting mold and the finished machined lead antimony anode positioned on center by the PVC fixture. At a current density of 3 amps/ sq in (total of 24 amps), the tank will give .0012" of chrome/ side/ hour in 2 hours. PROPWASH April 2019 25 Chrome tank