The difference between Wet Sand Casting and V-Pro plate casting in pianos

In this video, Student Coordinator Michael Stilwell CPT explains the difference in the two way of making a piano plate or "harp". Michael covers the benefits and downfalls of each method as well as shows a Baldwin L with a wet Sand Casted Plate. www.PianoTechnicianAcademy.com
#PTA #BaldwinL #pianoplate

[@studentjohn35]

I had the privelege to visit to Feurich factory in Gunzenhausen, back in 1987. Their sand-cast plates came from a foundry in Weissenberg. Julius told me that they deliberately left the cast plates untreated out in the loading dock right through the winter to get quite rusty. It further cured stresses in the iro, and made them easier to sand down. Of course all that wisdom was lost when "The New Feurich" came in.

[@sanjeethedwin1334]

Great video! At 1.39, were you referring to the wet sand casting instead of V pro plate?

[@thepianotechnicianacademy9560]

Ya that was confusing! Sorry about that! we were referring to wet sand casting. Thanks for pointing that out!

[@sanmateopiano4926]

I respectfully disagree with you. I think the information you are providing has been given to you secondhand, and you have not done any serious research. I think people in the piano industry have the responsibility to provide accurate information to the general public. I will suggest two readings "The Physics of the Piano" by Nicholas Giordano and "Five Lectures on the Acoustics of the Piano" You will find out that the plate is the most neutral component in the piano and has no contribution to the sound.
The following explains properly the casting process:
Let me explain one thing. In the V process the sand is dry and vacuum is used to assist the filling of the sand mold with the liquid metal. The dry sand causes the metal to cool more slowly allowing easier metal flow in narrow sections. That, along with the vacuum assist permits large slender castings to be made such as is the case with the cast iron frames in certain Japanese and some of the German pianos. Normal sand casting uses wet sand to permit compaction and to increase metal cooling rate. Typical sand castings are also poured in air (no vacuum). The result is that typical air poured castings must be have larger section thicknesses due to the faster cooling (metal can’t fill small section molds when it is cooling rapidly) and there is typically much more porosity.
The result is that typical sand castings are bulkier, have more porosity and other defects, but the metal in places may be slightly stronger due to the more rapid cooling. On the other hand the vacuum castings are much more slender, have less defects, but the tensile strength is slightly lower due to the lower cooling rate. In most situations the overall strength of a “more perfect” casting is equivalent or higher than that of a casting containing porosity.
Lastly the cast iron piano frame is not a “strength critical” component. It is a “stiffness critical” component as most engineering applications are. This tension of the strings is only 30-40000 lbs which does not stress the cast iron very much. The stiffness, or rigidity, or elastic modulus (different terms for the same parameter) which is an constant physical parameter and not affected by strength, is unaffected by any casting method. It is this stiffness which resists the tension of the strings and is pretty much insensitive to casting method. If you were to examine the cast iron frame closely before and after the strings are tensioned, you would note that the frame compressed slightly. Upon releasing the tension, the frame would return to its original size and shape. (We are talking about very small changes in dimension). If you could measure the stress on the frame at any one point, you would find that the stress was far below that of the typical strength. That is why we say that this is not a strength critical component.