Exhibit in Detail: The unique gravity-driven phonograph “Tin Foil"
The gravity-driven phonograph “Tin Foil" created by August Stroh in 1878 is posted under the heading "Exhibit in Detail".
The first gravity-driven phonograph “Tin Foil" with air governor, designed by the English engineer August Stroh, was presented at a meeting of The Society of Telegraph Engineers by its vice-president Sir William Henry Preece on February 27, 1878.
On August 3, 1878, information about this phonograph was published in The Illustrated London News. Gravity driven phonographs improved by August Stroh were distributed through the London Stereoscopic and Photographic Company.
Highly likely, it is the gravity-driven phonograph “Tin Foil" (the improved by A. Stroh phonograph with fixed cylinder and moving carriage with sound box) that is presented in the museum Collection exposition that is described in the publication “The EMI Collection”. This surviving copy was granted the status of "Science and Technology High-level Achievement” in December 2018.
The phonograph “Tin Foil" mechanism, originally designed by the English engineer August Stroh, with gravity-driven engine and air regulator, is mounted on polished mahogany base. Hollow cylinder with a helical groove, on which thin tin foil is fixed, rotates on two supports. The cylinder inner cavity is protected from dust by fabric. The left spindle of the cylinder, threaded along the entire length, lies on the support with a blade and a lock. The right smooth spindle with longitudinal groove is embedded in the drive mechanism leading hollow cylinder. A carriage with sound box and limiting screw is installed in front of the cylinder. The sound box consists of a body on the bracket, wooden ear cushion, steel diaphragm and spring-loaded sapphire needle in the holder. With the help of two adjusting screws, the bracket can be moved to accurately position the needle in relation to the groove on the cylinder. Gravity-driven engine is mounted to the right of the cylinder. The drive gear, driven by chain with the weight, transmits rotation to the hollow cylinder and the centrifugal air governor shaft. The airshaft has two connected diverging levers on the rotating support. Thin brass discs are fixed on the levels’ loose ends; they serve as air brakes. The levers are connected by coil spring, which can be moved along the levers and adjust the speed of rotation. The engine is driven by a chain slung over two sprockets and passing through apertures in wooden base. The chain forms two free loops, on one of which hangs movable block with weight. The weight is lifted to the upper position with the help of a handle with star wheel.
The phonograph is fixed on wooden stand of carcass structure, under which a weight with an eyelet is suspended on chain through pulley. Before recording, a tin foil is fixed on the cylinder. When the load is lowered, the cylinder rotates and moves along the axis. While recording the needle pressed against the cylinder lateral surface leaves a helical groove on the foil. The diaphragm, capturing sound vibrations, transmits them to the needle, which records them on the foil. The groove profile changes according to the sound vibrations. During playback, the needle placed in the recording groove causes the membrane to vibrate according to the groove profile and reproduce the recorded sound.