Expansion Tank: Design and Construction
Ryan undertook design and construction of the new expansion tank. The tank was specifically designed to fit between the suspension and the roll bar of the RCR, yet preserve the appearance of the original. This required a tank with several cut outs and bends. The front of the tank is angled so it sits flush on the angled fire wall.
Ryan made patterns for each section of the tank. Test sections of aluminum were cut and partially assembled so the relationship between the tank and the surrounding structures, particularly the suspension, could be checked. Once satisfied that the dimensions were satisfactory fit, the pieces were cut from 0.10, grade 3003 aluminum. This grade of aluminum was selected because two of the pieces needed to be folded 90 degrees: a difficult task with 6061. In this application we are quite confident that this material will work fine.
Two sections required the use of a metal bender. One of those required two bends. A 30” metal bender for under $100 did the job.
A TIG welder was used. The sections were tacked then welded, doing one seam at a time. Each weld was allowed to cool before moving to the next to minimize distortion. Before the last section was welded the hole for the filler was drilled to permit heat to escape from what would otherwise have been an air tight structure. The welding rod used was 4043, eighth inch.
Two bungs were used: one 1/2” bung (Canton 20-884A) for the return to the water pump and two 3/8” bungs (Canton 20-883A) for the vent line which connects to the top of the radiator, with an extra should another vent line be needed.
The aluminum fill neck is a Canton part, number 80-092. It is mounted on a section of 2 ¼ aluminum tube, 1/8 inch thick 6061. Since the neck is angled, the opening on the tank is oval rather than round. This was cut using a hole saw, cutting two overlapping holes, alternating between the two so that both punched through at the same rate. A bit of filing and the hole closely matched the opening of the angled filler tube.
A bit of Scotch Brite and billet polish finished the job. Installation will need to await the replacement of the engine.