HEADER PLATES he header plates are an interesting place to start, since they are unlikely to resemble anything that comes to mind when you think of a radiator; however, as the conduit between the header tanks and the actual core of the radiator, they are
1. The header plates begin life as sheets of brass, which are cut to the right size according to the radiator’s specifications. A job sheet will specify the number of rows required, as well as the radius of the corners. 2. The brass sheets, having been cut to the correct dimensions, are pressed for what are known as ‘piercings’ — holes through which the coolant will flow. The die used in the press is chosen to suit the radiator-core requirements. From here, the brass sheet, with fresh piercings, is brought to have its corners cut to the appropriate radius. 3. The header plate is then brought to the radius-forming press, where it will meet with one of a number of different radius dies, depending on the corner radius required. The process essentially gives the header plate a folded edge, along both the flat edges and the corner radii. 4. The completed header plate is ready to be attached to the rest of the core, the assembly of which is covered next. These can be made with different mountings, including bolt-on, weld-on, or with castellated edges that lock into place in plastic header tanks, sealed by a rubber O-ring. Adrad carries a range of header tanks for a variety of applications, from plastic header tanks for daily-drivers through to bolt-on brass tanks for a Kenworth truck.
The first step in producing the actual core of the radiator involves the ‘CT fin machine’, which is fed a large spool of copper that will eventually form the fins. The machine stamps the copper to achieve the accordion-like zig-zag shape, and punches louvres in it if required, before compressing the length to an appropriate finsper-centimetre measurement. All of this is preprogrammed into the machine according to the radiator being assembled, with each aspect of the procedure important in its own way. 1. The number of fins per centimetre is calculated based on the broader picture of the radiator’s application. If it is to be a narrow-core radiator, the convection effect could be enhanced with a narrower pitch, whereas a thicker core would function better with a more open pitch — “Having too tight of a fins-per-inch on a thick-core radiator would be like hitting a brick wall — not good for air flow,” explained Tara Maylin, Adrad’s New Zealand manager. Louvred fins are superb for most road-going vehicles, with enhanced cooling capabilities, but would not be used in certain applications. “On a hay-baler or machinery working in lime works, for example, it’s likely that louvres will not be stamped, and will have a more open pitch, due to the likelihood of seeds or foreign matter being lodged between the fins,” Tara said. Such radiators also use a tubularstyle core, rather than the CT cores shown here, and the design will make it easier to waterblast or manually clean the radiator core without damaging the fins. 2. Once the copper fins have been produced, they are arranged into what begins to resemble a radiator core. The tubes through which the coolant is channelled are brass that has been coated with solder — the solder coating will melt and fuse the fins with the tubes when the core is baked in a special oven. At this stage, the core can still be touched up cosmetically if it needs to look perfect, though aesthetic blemishes don’t adversely affect performance. Once the core has been baked, it stays as-is. 3. The fins and tubes are stacked alternately until the radiator-core specifications are met, with galvanized side plates on the top and bottom edges. A roll of solder is also applied between the galvanized side plates and top and bottom fins, as well as between the next row of fins — this is for adhesion, as stated in Step 2, since the uppermost and lowermost rows are most susceptible to damage from flex or pressure. 4. At this stage, the rows are stacked loosely, and the core assembly is clamped together from top to bottom to achieve the specified core height. Once the height has been achieved, the core assembly is held in place within a baking frame. 5. With the radiator core within the baking frame, the header plates can be applied. As described in the previous section, these are manufactured concurrently in a different part of the factory known as the ‘press shop’. 6. The header plates will eventually be connected to the header tanks — whether by welding, bolting, or locking tabs in plastic-tank applications. With the header plates in place on either side of the core and the ends of the tubes protruding through, the tube ends are flared to increase the water-channel openings for optimized fluid flow.