Updated: Aug 8, 2020
In the early days of the automotive industry, that being the late 19th century and into the early part of the 20th century, passenger cars and trucks had about as many different styles of radiators as they did methods of getting the wheels to turn. And while manufacturers toyed around with gasoline, diesel, steam, electric and even hybrids (well, Porsche did), they were also experimenting with different modes to cool those engines. Most radiators of the time were astonishingly complex creations.
The design that became most prevalent was the honeycomb core radiator, which was invented by Wilhelm Maybach and patented in 1900. Prior to 1910 or so, when the water pump became common, most radiators were gravity-feed. Honeycomb radiators were made up of thousands of little hexagonal tubes that were normally 2” to 3” in length that were flared and bonded together in the front and back, leaving a gap between the tubes, but only inside the core. The coolant would get heated inside the engine, which led to expansion of the liquid. This would cause it to flow to the top of the radiator, which was always the highest point of the cooling system. The coolant would then cascade down through the copper tubes; air would blow through the radiator, dissipating the heat. Eventually, the coolant would find its way to the lower radiator hose and back into the engine at a lower temperature. Most engines in the early days of the automobile were under ten horsepower, so the ambient air was usually good enough and fans weren’t needed in the beginning.
Fortunately, other methods of radiator construction were developed by the time that pressurized radiator caps were invented. The design that successfully replaced the honeycomb was the cellular core. It wasn’t that great, but it represented a significant improvement over its predecessor. Unlike modern radiators, cellular cores have no separate tubes. The passageways are formed by pulling the copper material through a series of dies & rollers. Originally available in 1934, cellular cores were at the top of the radiator food chain until the late 1950s, when the tube-and-fin design hit the market in earnest. Cellular was also the top dog in the heater core sector through the 1980s, when aluminum took control.
In the late 1950s and early 1960s, radiator manufacturers began designing their cores with copper tube-and-fin radiator cores and brass tanks. This design, although modified tremendously over the past decades, is essentially the concept behind all radiators currently being made, including aluminum core radiators and heaters. Interestingly, tubular radiators with serpentine fins were invented around 1905. However, just like electric cars, they didn’t take root until decades later. There are several different configurations nowadays including:
Copper/Brass with standard serpentine (aka corrugated) fins
Copper/Brass Flat Fin
High Efficiency Copper/Brass
The flat fin design was the first tubular radiator to hit the market. While these fins are great for strength, they’re also extremely heavy and don’t provide terrific cooling. Still, it was an improvement and many semi-trucks are made with them today. Although the copper industry has found ways to make their products lighter, these radiators are still very heavy and for that reason, Cap-A Radiator (one of the very first shops ever certified by NARSA as Heavy Duty Specialists) has installed a system in our new shop to make it much easier to transport heavy duty industrial radiators
It wasn’t much longer before the car and light truck industry replaced their flat fin radiators with the serpentine design that you will see on almost all late-model radiators. In fact, this design is such an improvement over the older designs that they are also found on many earlier radiators that needed to be recored or replaced with new radiators. While the basic design, invented around 1905, became popular in the 1960s, the high efficiency (HE) setup followed in the late 1970s. To create the HE design, engineers started making the tubes smaller and more closely packed together. Most HE cores have 5/16” tubes on 3/8” centers or 3/8” tubes on 7/16” centers.* By comparison, standard tubes are generally 1/2” tubes on 9/16” centers. There are multiple advantages to the HE core. One is that more of the coolant stays in contact with the tubes. Another advantage is that by having the tubes closer together, there are about 20-25% more tubes on average. The HE configuration is such a significant improvement over the standard design that replacements of flat fin / cellular / honeycomb radiator for improve cooling will be either a high efficiency radiator or an all-aluminum one.
By the early 1980s, most original equipment manufacturers began putting plastic tank radiators in their cars, light trucks, and even semis. This configuration took hold during the 1980s in order to lower vehicle weight and subsequently get better fuel mileage. Whereas most major manufacturers, including Ford, GM, Mazda, Nissan and all of the German companies went with aluminum cores, a few stuck with copper cores at the beginning; this included Chrysler, Toyota and Honda. However all three of those companies have since joined with the others in using aluminum cores for their products.
Today, the majority of radiators in passenger cars, light trucks and vans are constructed of aluminum cores with plastic tanks. In heavy duty and industrial applications, the radiators of choice are more often copper cores bolted on to steel tanks or soldered to brass tanks. Although there are still copper/plastic tank HD radiators as well as aluminum core/plastic tank combinations.
* “Centers” refers to the distance from the center of one tube to the center of the adjacent tube. Please see the accompanying graphic.