Ever wonder how a modern, high tech aluminum rad is constructed? We did too. Here’s a basic “snapshot” of how it’s done: At Ron Davis Racing Radiators, once an order it taken, it goes to the shop where a CAD designer turns the customer requirements into CNC machinery “language”. This permits precision CNC cutting of the sheet metal components. Each design is made with the idea that form follows function. Davis points out that angled tanks, or difficult designs aren’t bypassed for cost either. CNC cutting results in precision to 0.005-inch, which, in turn produces a perfect fit along with a high degree of repeatability (pretty important, if for example, you’re building a bunch of custom aluminum rads designed to fit where a VW Scirrocco rad once went). |
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Once the welding is complete, all parts are pressure tested to 32-PSI. Finishing technicians then assemble the radiator with stainless button-head fasteners and seal the fans to the shroud with foam tape (something you should consider). |
There’s some other stuff going on here too: The radiator in such a system is a huge tank that allows large amounts of hot coolant to come in contact with an equally large amount of (hopefully) cool air. The coolant is first forced into the radiator side tank (upper tank if it's an old fashioned non-crossflow system). From this point, the coolant makes its way through rows of very small copper or aluminum tubes, finally returning to the adjoining side tank where it is returned to the engine. While the coolant has progressed through the series of tiny tubes, it is cooled by air flowing over and beside the tubes. The primary purpose of the "fins" contained within the core (and surrounding the little tubes) is to direct airflow into the proper area of the radiator, however there are secondary reasons for the fins, as you’ll soon see. The most common core construction is the tube-fin or the ribbon-cellular design.
The actual numbers of fins within the radiator are actually very important. As a rule of thumb, a conventional radiator will normally have between eight and fourteen fins per inch (this can, however change depending upon the rad). Generally speaking, when the fin count number is increased, the radiator can "radiate" more heat to both the surface airflow and the surrounding air. Unfortunately, as fin count increases, so does the opportunity for plugging -- especially by bugs, dirt and other foreign junk. But for drag racing, the amount of road debris and other foreign objects encountered by the radiator is likely minimal.
Take Your Pick -- Copper Or Aluminum Construction ...
Radiators can be built from copper or aluminum (German silver and other expensive materials are sometimes used on high buck rads, but that’s beyond the scope of this article). They’ve been built this way for many years. So which rad material is better -- copper or aluminum? That's a good question. Most recently Detroit has embraced aluminum as the radiator material of choice. There’s a reason for this, aside from considerable vehicle mass reduction (aluminum radiators, on average can be as much as 1/3 lighter than an equivalent copper-brass radiator – that’s something any racer worth his or her salt should think about). And that’s cooling capability.
Certainly the choice of copper is a good one for radiators. It has better heat dissipating properties than aluminum. But there’s a caveat: The primary source of cooling in any radiator is the tubes. Heat dissipates from the coolant through the tube walls. This heat is then transferred to the fins that are in contact with the tubes. In turn, this provides a secondary source of cooling. As air passes through the fins, the heat is carried away. Radiator manufacturers know that wider tubes are more efficient because there is more "tube to fin" contact (in a typical modern aluminum radiator, the "tube-to-fin" contact surface area is increased by 20% over an identically sized copper/brass unit). This isn’t possible with a copper-brass design, because of tube wall thickness limitations. Today’s radiator technology (which typically uses wider tubes inside aluminum rads coupled with multi-louvered fins) has allowed the aluminum radiator to cool efficiently. Just as important, aluminum rads are now as strong, if not considerably stronger than their copper-brass counterparts.
The truth is, aluminum radiators simply cool better. Tests from various sources document a 28% improvement in performance when directly compared to a brass-copper equivalent, provided both radiators are identical in size. In reality, the use of aluminum in radiator construction can often lower engine temperature by as much as 30-degrees. Any vehicle will benefit from an aluminum radiator. And obviously, that includes bracket cars.
Size & Shape Matters …
Believe it or not, the shape and form of the radiator outlets might have a profound effect upon cooling. Now, I don’t have any concrete proof of this, but I’ve witnessed one particular car (a high horsepower 427 Ford powered job) that went through two different radiators. One was a Ron Davis model and the other from another manufacturer. The only (visible) external differences were the shapes of the outlets. The Davis-built rad had formed outlets with soft bends. The other had fabricated outlets with sharp bends (virtually a series of 45-degree joints welded together). The car consistently boiled over with the sharp-bend equipped rad. With no other changes (aside from the rad swap), the operating temperature was entirely satisfactory with the formed outlet radiator. The theory was that the sharp outlet corners actually restricted the coolant flow (perhaps more than we knew).