Cross Valves Again? Objections Welcomed
by Craig Brougher

I fully expected and received a few objections to my cross valve experiments and the comparison demonstration mentioned in my article, Duo-Art Cross Valves, Again? And I also appreciate the opportunity to answer, as best I might, this question centering around my comparison demonstration rig to compare a round and a cross valve.

Spencer Chase, whom I greatly respect, has added a few thoughts that give me the opportunity to reply to a few final objections which otherwise would have gone unanswered, and I appreciate the opportunity. I would also add that if I were an onlooker, I would probably have the same doubts, myself. So, I am happy to answer it.

I think we both agree that cross valves are unreliable as soon as the leather takes an impression, particularly if the piano is ever transported and then set up, again. The fact also that the original valves were dressed with pre-stretched, industrially tanned and staked satin suede leather which was tanned specifically for the Aeolian Company and is no longer available, also makes an enormous difference, as to the years of usability of such a valve restored with garment leather, under average home use.

Now I would like to just address his main points, with easily proven facts that any professional rebuilder of reproducing pianos would know if their experience dictated.

“Reproducing pianos rarely have single valve systems. Reliable operation over the wide range of pressures needed in a reproducing piano have generally prompted the manufacturers to use a double-valve system or other methods to improve valve responsiveness, such as the Ampico ball bleed.”

This is a bit misleading, in my way of thinking at the moment, in that it might imply to some who are not that well prepared that the old Aeolian valves must have been very good to do what they did without primaries. (The best player valve ever built by a mile, in my opinion, was the Ampico B valve, and nothing else could ever compete with it.)

Aeolian was able to utilize a single valve system, not because their valve was unusually sensitive, but because on average, the average tracker bar tubing length was less than 2 feet. If you would actually do this experiment (as I have) and operate the older stack’s valves off of the end note tracker bar tubing length of an Ampico, which averages 5-1/2 feet in a baby grand, WITH an actual Aeolian tracker bar nipple venting it’s end, you would find that those Aeolian valves operate either poorly or (usually) not at all at 5 inches of water vacuum. This doesn’t require actual flow measurements with fancy laminar flow measuring equipment. Just hop down under your Older model Steinway grand and make a momentary substitution. So the Duo-Art was not actually an exceptional valve. It was, however, an exceptional layout which took advantage of a very ordinary valve. As a matter of fact, that valve was one of the slowest player valves– far slower and heavier than a Standard double valve action. But then, it didn’t need to make over 1000 repetitions/minute, as Standard advertised in one of their own brochures.

“The Duo-Art is an exception. Whether it was a good choice or not, it is my belief that the designers of the Duo-Art were attempting to improve the responsiveness by the use of cross valves.”

I agree with this statement, in that the cross valve shape was utilized in order to allow a smaller pouch to activate a larger cross-sectional valve orifice than it was able to ordinarily handle. But I’ve already said that. That was the initial criteria, I suspect. It was intended that this design could use the smaller pouch, and it did. Their real goof-up in this department hasn’t been mentioned by anybody, yet. That was the fact that they initially used remote bleed placement, which early-on were celluloid, whose holes were often oblong or varied, the disks were not true and square, yet the plastic was relatively thick compared to the hole diameter which created all kinds of unwanted turbulence within the bleed orifice, itself (not my research, but Ampico’s). This fact alone proves that these valves were a “seat-of-the-pants” jump-to-conclusion” concept with very little critical testing before they were chosen.

To prove that for yourself, all you need to do is check out the extreme parameters of one of these valves at the lowest useable vacuum level, measure accurately the original bleed diameter, and then substitute a precisely drilled brass bleed cup for the celluloid, and test the valve again! Suddenly you see a slightly different response in about 4 out 10 samples, if you have measured accurately enough.

Another thing that any careful professional restorer would have noticed about these early Duo-Art valves, is that many of the celluloid bleeds in the center of the piano were enlarged or drilled out slightly by the factory, I suppose to quicken their speed of return (?). The fact that the end notes did not have the slightly enlarged bleeds indicate possibly that because of the slightly greater tracker bar tubing lengths to those valves, they could not afford to increase them for fear their sensitivity to faint air signals would be compromised. I have encountered literally dozens of Steinways and Webers with this factory bleed sizing as part of the piano’s regulation, both in the oldest stacks as well as the reverse stacks, and later even with the factory’s improved brass bleeds. I know it to have been factory, because the original cloth cover on the bleed strip had never been removed prior to my restoration.

“There is no disagreement that the force to unseat a cross valve that will pass the same amount of air as a round valve is less than that required to unseat the round valve. The force to unseat a valve is determined by the area of the valve face exposed to vacuum, the weight of the valve poppet and the contact surface of the seat. When tests of flow are made, it is important to consider the actual operating range of the valve, in its intended application. A stack valve is marginally
adequate at low vacuum pressures and this range is where valves should be compared.”

I think this frankly says it all, and I agree with it, fully. What we are discussing is NOT whether the valve in question was adequate. It was MORE THAN ADEQUATE! We are discussing a minute technical point that centers on the reliability of the valve, over time and various situations. And we both agree that its reliability is questionable, particularly with modern leather available to rebuild these kinds of valves. The only other question is the best way to restore these valves, and that question is not even brought up by Spencer. So, I would have to say that Spencer and I agree on every important aspect of this valve. He is a good researcher and has my full respect.

“All but the worst valves will perform adequately at higher vacuum if they perform well at low vacuum. Measuring the flow through a valve at high vacuum does not necessarily indicate how it will operate in the critical low vacuum ranges. It is likely that greater turbulence will diminish the total flow in the cross valve. However, since the flow is likely to be more than adequate at higher vacuum, this is not of much importance.”

Sensitive flow measurements are never required to evaluate the characteristics of a player piano valve at high and low pressures, although I don’t criticize any attempt to do so. As a matter of fact, such equipment is immaterial because precise flow is only meaningful in laminar flow measurements anyway, and that never happens in player piano equipment. Turbulence varies in valve chambers and crooked or thick bleed holes relative to both pressure, reflected forces from other turbulent areas, and rate of change of pressures produced (see the Ampico testing lab experiments with these very factors), and flow gauges don’t even begin to measure these variances. Nor do you have to. The best way to measure the performance of a valve is to measure the performance of the pneumatic it controls at low and high pressures and during the changes of pressures as the valve is actually paralleled to everything else.

In the next paragraph, Spencer Chase questions a device that I built to merely demonstrate two things– the noise produced by the cross valve and the flow efficiency of a cross valve as compared to a circular, round valve hole. (Please keep in mind that this is relative, it does not criticize the cross valve design to do what it was intended to do within its requirements, and is a simple demonstration which is easily duplicatable).

“Judging a valve on the basis of how it performs at higher vacuums is not likely to produce meaningful results. Measurement with a heavily sprung reservoir is not the right test. Accurate measurement at low vacuum is more likely to produce comparative indications that relate to how the valve will perform in actual use.”

The “heavily sprung reservoir” is exactly the right test for a demonstration, precisely because mine never exceeded 30" of vacuum, although a sensitive Henni gauge never rose more than 7", the setup was still testing in a wide spectrum range that probably faded out audibly at 2-3 inches. But I’ll show you what I mean:

When you collapse the reservoir on an ordinary pumper player, and measure the static (negative) pressures with a gauge, what do you generally read? (Hint: close off all nipples on a player pump, connect a gauge, collapse the reservoirs by hand, and see what the gauge rises to. 20" if you’re lucky? Usually no more than 15"? They vary because of the size of the plenum that must first be exhausted before the gauge can read. Now leave your nipples closed-- all except for one, to which you connect a typical player valve orifice opened by a poppet to .035, and check your initial vacuum once more. The average 7" vacuum startup is usually what you get).

If Spencer really wanted to know beforehand what sort of pressures were being generated by my demonstration at the AMICA meeting in St. Louis, he may have tried something like this:

1) Grab a typical player piano reservoir. I used a Standard Action Co’s right reservoir off an old double-valve player piano. Ignore the condition of the cloth. All you are interested in is the sprung weight.

2) press it closed on a good bathroom scale and see how much pressure it takes to close it. In this case, it was 34 lbs with two springs inside. (Nobody has monkeyed with the reservoir I rechecked for this article, which is still clothed in its green original cloth.)

3) Measure the reservoir (17-1/2 x 6), compute area (105 sq. in) and use the expression (P=.6W/A), found in The Orchestrion Builder’s Manual pg. 51, under Pumps and Reservoirs, to calculate the expected (maximum possible) vacuum created by collapsing that hinged bellows under static conditions (zero airflow)

4) And the answer is 28" of static vacuum. However, a gauge would not read more than about an average 5-6". Here is why:

Although that is not what anybody would consider a “high vacuum” it is a top max. (ideal) calculation for static pressure only– which is never achieved, not even half of that tension, because when it’s released, a valve is always open, so the usual “area under the curve” calculus (or your favorite method) to equate the curve of release from static to zero isn’t necessary. All that one needs to do is time the release, roughly. It takes about a second to exhaust 4 inches of bellows travel through the round hole with .035 valve travel. Since the energy released is flat spring energy, just estimate the first 1/4th second represents roughly 50% of the stored pressure, the second 1/4th second represents 50% of what’s left, and so forth, then the response through either valve plate averages less than 7" (with a really fast gauge) and the effects are perfectly relative between the two valve plates because they share the exact same turbulent conditions (as physically possible to achieve because they share the same valve chamber) so variations other than the actual differences between valve plates is canceled out.

My suggestion– ignore pressure readings because they are immaterial, relative to either valve, and well within the useful range of a sensitive reproducer, and actually below the range of most for 3/4ths of the second. Few pumper player reservoirs would have any use for pressures over 20 inches, anyway.

That means that the pressure is collapsing (kinda) exponentially but very predictably at an average (center position) pressure of about 5-6." The ear actually hears the change of pitch during this entire exhaust, including the very lowest pressure remaining (which goes far lower in pressure than a player piano runs) and compares it to the other valve plate’s pitch. The pitch of the cross valve plate is both higher and louder, and lasts 25% longer. The round valve plate is a low, quick, almost inaudible whoosh like a sigh (but you can hear it exhaust the entire reservoir with your ear close to it), and the cross valve plate is a low hiss, as though a quick sigh through your teeth, instead. (Not bad, you understand. It works fine for a note pneumatic. But just not quite as efficient as the round hole, and that’s our only purpose of this discussion– a comparison between two valve plates under realistic pressures encountered).

“There is a definite relationship between area perimeter, valve gap and flow and this can be measured under conditions similar to a valve operating in a stack. We can be scientific and measure the performance of valves instead of attempting to discredit the opinions of others by quoting them out of context and distorting their arguments.”

“Whether increased performance is worth the risk of increased maintenance can be better determined once the performance is accurately evaluated. “I have the tools to accurately measure flow in real time, under actual playing conditions. I do not have the time to construct a model of each of the valves which should be compared but will find time to evaluate them if someone else has the time to construct the models”

I appreciate Spencer’s time and he’s right-- he should not waste it researching a subject that has been beaten to death for years, and has been so many times proven and re-proven by the bitter experience of cross valve owners.

“Pneumatics, loaded to simulate the piano action, fitted with each of the valves to be compared, can be driven with identically timed signals and real time graphs of flow to the pneumatic can be produced. Additionally the pneumatics can be fitted to operate an actual piano action so as to limit the performance comparison to the conditions which are relevant.”

Once this is decided for all time, my question still is, “Who cares?” I also sense that Spencer is making the same point to us, as well! The initial topic with me has always been the reliability of the cross valve and that depends completely on the number of years of heavy use with modern day leather and materials available. I, as well as every other rebuilder, agree that it was an adequate valve for the piano, given the layout and requirements by the roll. I disagree with those who would leave the cross valve plates in the piano and have already demonstrated how replacement valve plates should be utilized, what changes should be made as to the valve leather punchings, and why. Since Spencer has not challenged this point but rather agrees, I think the point is made to everyone, and I appreciate Spencer’s contribution.

Craig Brougher

I Don't..

This page was last revised on March 14, 2014

Page Design by Player-Care

Grand 16 IconGrand 32 Icon

407 19th Ave, Brick, NJ, 08724
Upright 32 IconUpright 16 Icon
Google Adsense Ad