Valves: Materials

Having taken a peek at the theory behind valves, it’s important to get practical with the materials.

In a Standard / Auto DeLuxe etc double valve system, the two principal valve types found in the stack are the primary valves – which are an outside valve – and the secondary valves, which are an inside valve. The terminology surrounding the player piano components has been the subject of debate; there is a mostly accepted convention about nomenclature, but better to not get bogged down too much for the purposes of this discussion.

The secondary valves are a stem-type valve, which varying methods of how the facings attach to the stem. For the purposes of this post, I am confining my remarks to the facings.

In this system both styles of valves have two facings; in an outside valve both facings seal against a wood seat, in an inside valve the upper facing seals against wood but the lower seals against a metal plate.

Leather against smooth wood is generally a reliable seal, all other factors considered.

Leather against a metal ring is far less forgiving, particularly if the leather is poor quality (uneven, too fuzzy, or stiff, or porous), or if the valve seat area of the metal plate is corroded or not perfectly flat. There are other reasons (beyond choice of leather) as to why the secondary valves require extensive exacting work to get them to perform well. More on that later, perhaps.

At the time of this writing, high quality leather, the kind required for inside lower valves seats (meeting metal plates) is difficult to source as it no longer widely produced and therefore not readily available, even from trade supply houses. Conventional wisdom dictates that this material be a split calf leather with a smooth nap, to prevent lateral leakage.

Old valve leather vs. new

Some rebuilders have resorted to using thin silicone or neoprene material for lower secondary facings. Like other non-traditional materials it is the subject of controversy, however if it can be made to work in a reliable and durable way – the results are what matter.

For the other leather in primary and upper secondary facings, I have received numerous recommendations for the Columbia Organ Leathers company. I am using it in my stack and find it fit for purpose. I know that others use OSI for their needs. These companies are also able to furnish good leather for other types of valves (not yet discussed) such as flap valves and pallet valves.

Wherever you choose to obtain your materials, make sure to inform yourself about the supplier and their product. Using inferior materials is a fool’s errand as it will waste time and money trying in vain to get good results.

As the prospect of restoring valves strikes terror into the hearts of some inexperienced restorers, they may be tempted to skip over doing it, if the older leather facings “look good”. Older restorers sometimes talk about having gotten away with this omission, when doing a restoration job on a player action when they were starting out.

The difference is that when senior rebuilders worked on players in their youth (e.g. the 1950s or 60s), the pianos in question may have been 30-40 years old. The leather in the valves and gaskets may still have had some life left in it at that time.
After 90 or 100 years, it is a safe bet that all original leather and cloth in the player action need replacing, to function as intended.

The bottom line: you can’t have well performing valves without good materials!

Valves: Theory

Although I don’t necessarily want to get too far into the weeds on this topic, I do believe it behooves me to discuss valves, given their importance in a player piano mechanical action.

The key to understanding player pianos is fundamentally a question of comprehending valves: air pressure and flow. Conversely if you don’t understand how valves work – in theory and practice – you probably won’t successfully figure out how to rebuild and troubleshoot your project. A helpful analogy may be to think of the airflow as an electrical signal, and the valves as switches.

Let’s focus on some theoretical basics for this post.
There are a number of different types of valves; the most common are inside and outside valves. Outside valves normally function as a “primary” role, while the inside valves are generally “secondary”. This is how they are assigned in a Standard style double valve player action.

Both styles of valves operate in a valve chamber, which needs a constant supply of suction from the pump to operate. Each valve has a corresponding pouch underneath it, which will activate the valve when the pressure builds enough to inflate the pouch. Every valve will have an input and an output as well. Note the following image, and how the output of the primary becomes the input of the secondary:

valve 1 annotated complete
Typical double valve action, taken from “Rebuilding the Player Piano” (Larry Givens, Vestal Press, 1963)

It is important to bear in mind too that the input signal doesn’t directly come into contact with the valve. The signal determines whether the pouch (below the valve) is up or down, which in turn determines if the valve is opened or closed.

Primary valves receive a small signal (usually via tracker bar), and augment it. They are signal amplifiers.

Secondary valves also multiply the signal, but the signal is reversed. This is an important note. In other words, if the input to the secondary (or any inside) valve is atmosphere, the output is suction. If the valve receives suction (i.e. the valve is closed) its output will be atmosphere.

Here is another line drawing of the signal path in a Standard double valve style action.

double valve system annotated v3.png

There are three discrete stages which occur almost simultaneously.
When a perforation in the music roll passes over a hole in the tracker bar, this admits a small amount of atmosphere and initiates stage 1. This small amount of atmosphere allows the pouch to rise and activates the primary valve. The now open primary valve allows a larger signal of air to enter the connecting channel to the secondary pouch, which is then raised and opens the secondary valve in the same manner (stage 2). The activation of the secondary connects the pneumatic to the valve chamber with its reduced level of atmosphere; in other words the valve outputs a signal of suction. Stage 3 occurs when the atmosphere has been reduced in the pneumatic the outside pressure of the atmosphere forces the pneumatic to collapse. The pneumatic (in this design) collapses upward, actuating the piano wippen and playing a note.

The cycle ends when the paper again covers the tracker bar hole; with no more atmosphere signal the suction in the primary valve chamber quickly equalizes the pressure on both sides of the pouch (aided through a small “bleed” passage next to the pouch). This in turn shuts off the signal to the secondary valve and then to the pneumatic, which equalizes once more with the surrounding atmosphere, and reopens.
This whole cycle may take a fraction of a second.

The valve chambers for the primary and secondary valves are under constant suction (as generated by the pump); in the diagram just above the blue arrows indicate the path of the suction back to the pump. This is to differentiate from the “signal” paths which are colored gold and orange.

I hope you have enjoyed valve theory 101; if you have interest I invite and encourage you to read more on the subject in one of the resources previously mentioned. Don’t feel bad if you don’t understand everything at a glance, it took me hours of study to really get what is going on in these diagrams!

On to materials!