Thoughts on Magnets and Book Music
By Mike Ames
RE: Some thoughts in response to Robbie Rhodes comments about electric valves.
From: Mike Ames and Dave Wasson
Covering too much ground in too short a time can cause confusion. The following comments are meant to clarify minor misunderstandings. We want to thank Robbie for his insights and enthusiasm in helping us. We are not really looking for a source of cardboard for book music. We think there is no source of cardboard in the US as robust and durable as the German cardboard. The German cardboard is still available in blank rolls or ready-made blank books, with or without hinges. In general there are two styles of cardboard books, those with linen hinges and those without.
For those interested in making blank cardboard books, there is a very good video of Arthur Prinsen making cardboard books in his shop in Belgium, which can be obtained from MBSI. A while back Ron Bopp (of MBSI) wrote an excellent article about making book music which appeared in the MBSI Bulletin.
David Wasson has never made music books out of shoe box cardboard. His small street organ is a keyless book organ and reads the books using a pressure system.
Book organs come in two flavors, key or keyless style. The keyless system reads the books using air pressure not vacuum. The books are held to the tracker bar by a grooved roller. The keyed system looks similar to the keyless system, however there are hardened steel fingers which read the holes in the cardboard mechanically. The fingers pop upward into the holes and are subsequently depressed by the end of the hole. This system also uses a grooved roller.
We have built a MIDI input to the large 101 key Mortier Dance Organ (with out injuring its originality) and therefore we have less need for cardboard.
On the subject of electro-pneumatic valves:
Why ? Because some of us would like to operate pneumatically controlled musical instruments with these valves.
We question whether any realistic heating or cooling will affect the spring rate. There are several different electric valves being discussed, it's time for review and definition.
Reisner makes two valves that might apply to this situation. The first is their Series 25 & 26, "Chest Magnet" which is the modern-day equivalent to the oldest style of electric pipe organ magnet. Because of its distinctive shaped electromagnet, we call it a horse-shoe chest magnet. The second valve is called a model 601 "Direct Pallet Magnet". This style of device consists of an electromagnet and a pivoting armature which has a leather covered felt pallet attached.
The two additional valves that are discussed by Robbie, are the so-called Concertola valve and the Stahnke valve. The Concertola valve is a small electromagnet and core surrounded by a iron cup-shaped pole and a thin iron disk covered with felt and leather for an armature. The Stahnke valve as we understand it is a solenoid operated armature with spring loaded return.
The ease of adjusting a concertola valve appears to be consistent with the construction of equipment in which it was to be installed.
It appears to us that the magnetic path in each of these designs is optimized by small gap and/or magnetic lead-in. None of these designs return the armature by gravity alone.
The duty cycle of a typical MIDI operated valve is very low due to the nature of music, as seen in the low density of holes to blank paper in music rolls. Therefore heat dissipation is almost not an issue.
We have a mystery about valve speed remarks because we are not aware of any testing data. In fact the proposed testing of these, and other valves is only now being planned.
There are those "purists" who become very nervous at the thought of contaminating pneumatic instruments from yesteryear with any of todays electrons. Because we have several MIDI systems in somewhat visible locations, we have in times of stress and misunderstanding, heard remarks decrying anticipated sluggish temporal response. So far we have used the valve which would appear to be the slowest of all (the Reisner pallet valve) and to date no one has been able to demonstrate that it has any perceived inadequacies. We will be delighted to supply a sample of each of the valves that we have for testing and we will look forward to the published results.
We have spoken to Reisner about fabricating a truncated version of their horse-shoe style valve for the MIDI market. They are looking into it.
Mike Ames and Dave Wasson
(Message sent Wed 3 Jan 1996, 22:06:30 GMT, from time zone GMT-0800.)