Piano action parts are highly complex mechanisms with thousands of working components. With use, the action parts fail due to impact pressures, environmental conditions, and reconstitution of materials. For example: wood dries, metal fatigues and stiffens, felt wears, and properties of each react with the others creating problems.
In many cases, parts can be reconditioned. However, replacement is required when extensive deterioration occurs or a piano is being rebuilt to optimal quality.
The single most important factor to consider when rebuilding an action is the selection of replacement parts. Fortunately, there are a couple of good after-market choices.
Selection is made on the basis of:
- Manufacturing quality of parts
- Dimensional replication
The following images show the steps taken in our shop to select new parts and replace parts on a grand piano action stack. The action stack contains action rails, action brackets, hammer shanks and flanges, and whippens. Replacing the hammer heads will be detailed in another page.
The action stack mounts to the key frame via the action brackets. The key frame houses the keys and provides precise positioning of the action parts to their corresponding keys, and alignment with strings.
On this particular job I selected from German made and Japanese made parts. My final selection was based on the duplication of exacting measurement as show in the following pictures.
Picture on left is of the original whippen and two replacement choices. Picture on right is of the original shank and an exacting replica.
Since the shank is a excellent replacment a decision only needed to be made for which whippen to select.
Notice the comparisions in these photos:
Both choices are exact with regards to the front to back dimensions relative to the flange center and jack center. The repetition levers are both a good match and each has the independent hammer rest felt just like the original. However, notice at the bottom how the saddle is exact in the left picture while in the right picture the saddle center is forward. This small difference can change the geometry of the action in a major way. For this reason I selected the part at left. The part is a Japanese made part. I do not favor or endorse any action part manufacturer but here is why this is interesting.
The German part is most often considered superior and demanded by clients, and set as criteria by purchasing managers of universities and organization. In some case this is valid. The point, however, that needs to be made is that priority should be based on dimension. I have tested both parts and found pros and cons with each, yet I use either depending on which is the best dimensional fit. Both are excellently made and both have issues with center torque variability. Both companies have exact measurements for some instruments and both will not match in some cases.
So, beware of brand selling. A rebuilder must have the knowledge to determine, by inspection, which part to use.
The following statement further supports my position:
Notice how I do not even consider the US made counterpart. I do not mean to be critical of the manufacturer. I am critical of the sentiment that if it is not original factory then it is not authentic and therefore, once rebuilt, the piano will not be authentic. Dealing with older pianos is a real game changer when it comes to this sort of sentimentality.
One-by-one the new whippens are installed onto the action frame.
After all parts are mounted the first step of regulation is performed by spacing and aligning according to the original positions. Later, once the action is inserted into the piano, finer spacing will be done.
This image shows new parts misaligned on the action rail. This is corrected by a process called traveling.
Traveling is the process of centering the parts within their arch of motion (travel) by inserting a thin paper between the flange and action rail. When the screw is set tightly the part will be aligned and move through it’s correct range of travel.
Notice how the shank narrows further up in the treble section. This will add “whip” or flexibility to the shank, minimizing a percussive collision with the string, and allow the hammer to rebound off the string to produce a clearer tone.
Action stack with new parts installed.