Pneumatics and Organ Reeds
By Robert Linnstaedt
Regarding air pressure (suction), a reed organ plays it's reeds on a mere breath of air. A piano pneumatic requires a greater amount of kinetic energy.
Reed organs use low pressure of higher volume, whereas piano pneumatics use high pressure at lower volume. The difference is in a) the kinetic energy of the air, and b) the volume of air being moved. To what may we compare? A reed organ is like a man who eats many small meals throughout the day. A player piano is like a man who eats big meals but less frequently.
Consider the mass of the little brass tongue in an organ reed, compared to the mass (not weight!) of a piano action. Vacuum first has to overcome inertia to set reed or hammer in motion; the more mass, the more kinetic energy (higher pressure/vacuum) required. Also, the tongue vs. hammer are doing 2 very different things. The tongue is merely vibrating. The hammer has to travel and strike with significant force.
It might seem that the same vacuum reservoir would serve both purposes, if it's on the high vacuum required for pneumatics. Let me inform you, before you make an irreversible mistake. The organ reeds will likely ruin because they (being "free" reeds) have nothing to rest against if overblown. The result is that the force of wind can bend them over. Or they may just break off!
|
(Message sent Mon 4 Dec 1995, 17:23:30 GMT, from time zone GMT-0500.) |
|
|
Mechanical
Music Digest™ Archives
