Restoring a Challen Grand Piano: Dismantling begins

After a long time getting other projects sorted, the Challen can now be properly started!

Removing the dampers

I always like this part of the rebuild process. It seems quite theraputic to be taking a piano apart every so often, rather than the painstaking process of putting everything together just so.

Even so, there is somewhat of an artform, even at this stage of the process! The photos show several stages which most rebuild projects go through which I work on.

First, the dampers are unscrewed from the damperlift mechanism behind the keyboard, and can then be removed.


Bass String Rubbing

Next, we measure the bass strings by doing a wax rubbing with a sheet of thick paper. We also push the paper over the hitch-pins, bridge-pins and agraffes. This rubbing will then get sent to a bass-string manufacturer who can accurately create a bespoke set of strings specifically calculated for the piano, to give the best possible tone from the instrument in the lower octaves.


Strings Removed

Once this is done, the strings can then be removed from the piano. This is done gradually at first, reducing the tension throughout the piano evenly, so as to avoid putting too much pressure on any part of the frame and soundboard. The strings are then mostly recycled, apart from one or two of the bass strings, which are sent to the string manufacturer as references in his calculations.

Measuring The String Lengths

As for the treble strings (ie, any strings which are just plain steel, not copper covered,) the length of each these is measured carefully. We use this measurement to calculate the gauge of wire to replace on each note. (Notes near the top of the piano require a thinner gauge of wire from those further down.) Thickness of wire is measured to within a small fraction of a millimetre.

Measuring Downbearing

Another thing we do at this stage is measure the downbearing of the piano. Downbearing is a term which refers to the fact that, when the strings run along the length of the piano, they pass over a bridge (seen in the picture marked Measuring Downbearing, on the left), and this bridge should be slightly higher than the contact points of the string on either side. On some pianos, this downbearing can disappear and need adjusting. Running a piece of ordinary string is a good way to test this. The Challen had no real issues. Downbearing was still present, and little differences in the balance can be adjusted out later.

Removing the Wrest-Pins

After this, the wrest pins which are used to tune the strings were removed. Several of these are measured to get their correct diameter, as we will need to put new, slightly larger pins back into the piano when it is restrung.

Following this, the bolts and screws which hold the frame in the piano are taken out. It is common practice to put the screws in a piece of cardboard, as this helps to relocate them in their correct position later.

Taking the Bolts Out

Finally, the frame can then be lifted out of the piano! This is another moment I like about the whole procedure; as it means you finally can get access to the soundboard underneath. I'm hoping this to be the next entry in the blog, and will be able to talk about what we are doing to restore this important part of the piano to great condition.