Miss Shilling’s Orifice: Innovative Female Motorcyclist Designed

Miss Shilling's Orifice - Norton 500
Beatrice Shilling at Brooklands July 1935 on her Norton 500.

Before she helped win World War II for the allies, Beatrice Shilling was a prominent motorcyclist. Before she hit 30 years of age, she had earned a gold star for putting in a 100+ mph lap at Brooklands on a Norton 500. As smart as she was fast, Shilling (“Tilly” to her friends) later attended Manchester University, where she was awarded an engineering degree. That led to a Scientific Officer appointment to the Royal Aircraft Establishment (RAE).Miss Shilling's Orifice

As WWII raged on, the 1310-horsepower Rolls-Royce Merlin III engines used in the Spitfire and Hurricane aircraft were fed by an ATV35/135 carburetor manufactured by Skinners Union Carburetter Company (SU). When engaged in steep dives, the SU carb would flood with 100-octane fuel for 1.5 seconds as the floats hit the top of the bowl.

Shilling devised a solution in the RAE laboratories. She developed a restrictor with a calibrated aperture that was inserted into the fuel line. The orifice plate, as it was alternately known, restricted the fuel sent to the bowl. While the engines still had a bit of a hesitation, the 1.5 seconds of flooding was eliminated. By 1941, all SU carbs had adopted her modification—Miss Shilling’s Orifice—as standard fitment.

Shilling’s passion for speed continued after the conclusion of WWII, racing sports cars at Goodwood in the 1950s. Her work continued at the RAE labs, studying aircraft hydroplaning on wet runways. Her efforts led to an Order of the British Empire appointment in 1948, and she retained her position at RAE until 1969.

Burlen Ltd currently manufactures SU, Amal, and Zenith carburetors, and passed Shilling’s story and photos on to Ultimate Motorcycling.

“We are proud of Skinners Unions’ role in aeronautical carburetion history,” Burlen Managing Director Mark Burnett told us, “and have admiration for the Skinner family for pausing car production to help with the war effort. Beatrice Shilling is an inspiration to us all, not only was she a first-class engineer, but she also loved speed and was fast on both two wheels and four. Today, Burlen lives by that mantra, combining innovative product engineering and a love of all motor-powered vehicles. Miss Shilling should be celebrated and remembered for the incredible woman she was, and as an engineer who made wartime pilots’ lives as safe as they could be when in battle.”

We are happy to retell the story of Miss Shilling’s Orifice, and the remarkable motorcycle-riding woman who created it.