All Franklin cars were air cooled, which the company considered simpler and more reliable than water cooling, and the company considered light weight to be critical in making a well-performing car given the limited power of the engines then available. Franklins were wood-framed and light aluminum was used in quantity, to the extent that Franklin was reckoned to be the largest user of aluminum in the world in the early years of the company.
Franklin cars were technological leaders, using six cylinders by 1905 (a world first) and in 1907 were the first automobiles to have automatic spark advance. They were the undisputed leader in air-cooled cars. Prior to the invention of antifreeze, the air-cooled car had a huge advantage in cold weather, and Franklins were a popular buy among people, such as doctors, who needed an all-weather machine.
The early 1920s saw Franklins redesigned to look like conventional cars, a dummy 'radiator' (actually simply an air intake) at the front of the hood. The Franklin styling was beginning to look old-fashioned compared to other makes.
In 1932 Franklin introduced another first, an air-cooled, 398 cubic inch V12 developing 150hp, installed in the finest automobiles the company had ever built, the Franklin Airman Limited. Unfortunately, this was simply the wrong vehicle to be building after the crash of 1929 and the depression that followed, and they sold poorly, nowhere near to recouping the company's investment. The company declared bankruptcy in 1934.
Car production did not survive, but the company continued under new management and ownership as an aero-engine manufacturer.
Franklin engines powered numerous light planes as well as (thanks to their light weight) most early American-built helicopters. The company declared bankruptcy again in 1975 and its designs were sold to the Polish government; engines based on these designs are still in production.