The "Fan"

The "Fan", detail of split hub

The Wright Brothers tested each piece of their equipment to make sure it performed as required. In the case of the Vertical Four Engine, the Wrights mounted a flat bladed propeller, which they called a "fan", on the flywheel. They knew the resistance of this fan from their wind tunnel tests. Knowing this resistance, and using a hand-held revolution counter, they were able to calculate the horsepower of the engine.

The Wright Experience reproduced this test, following written descriptions of the Wrights' original test. On the second run of the engine, the fan screwed itself to the flywheel and split. Fearing they had made a serious misjudgement, the team review Orville's notes on the test. At the bottom, they found this entry: "Second run, 600 rpm, fan split". The Wrights had the same problem!

The solution used by the Wright Experience is the same one employed by the Wrights: a two-bladed flat fan with a steel hub.