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Common types of repair
Replacing Broken
Strings
I recommend replacing
broken or missing strings on a piano for a couple of reasons:
1. Volume on the note struck will be considerably reduced
and will not match with other notes being played.
2. The striking hammer will torque (twist) as it hits the
remaining string(s) damaging the friction necessary in the hinging parts.
3. The hammer over time will wear unevenly requiring it
to be surfaced or re-shaped so that the strings are struck evenly at the same time.
4. The note stuck may not play at all or get stuck.
Replacing Bridle
Straps
Bridle straps are named after
the bridles used for horses. There are 2 schools of thought on their function and one undeniable fact. Depending on who you
talk to, the function of the bridle strap is to help jerk the hammer butt back into position so that the note is able to play
again…or not. The undeniable fact is that they must be connected for the
action to be put back into the piano.
Bridle straps are made traditionally
of cotton braid and leather tabs. The unfortunate part is that as they age, they start to dry rot, start falling apart and
the small parts fall to get stuck between keys and other areas that prevent the piano from functioning properly. When you can break a bridle strap with your fingers by pulling it apart, it’s time to replace them.
Normally they last about 50 years.
Hammer Surfacing
Piano hammers are just like
they portray…little hammers that beat on the piano strings and make the strings vibrate. They have a little handle (thinner
than a pencil) while the hammer itself is made of felt (sheep wool) with a wooden core that the handle (hammer shank) fits
into. The felt it cut into shape then wrapped, glued and sometimes stapled to
the wooden core with hydraulic pressure until the glue dries. The hammer is designed so that there is a tremendous amount
of surface tension at the strike point…the point where the hammer contacts the string(s). This surface tension and compression
inside the hammer enables the hammer to bounce off the string with very little contact time with the string.
| piano hammer in motion |
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As a hammer wears, it develops
grooves at the strike point. These grooves develop into cuts which not only greatly reduce the surface tension of the hammer,
but change the tonal quality of the note. The felt becomes compacted and hard in the bottoms of the string cuts and gives
a harsh, uneven tone. Because some keys are used more than others, they will wear differently and provide an inconsistent
tone between notes.
If we were to look at worn
hammer from the side, you would be able to see the rounded shape in the front where it contacts with the string. Looking from
the front, we can see that the cuts in the hammer are flat because the strings are flat. Looking from the side again draw
an imaginary line vertically as deep as the grooves in the front of the hammer are.
By doing this we can see that the worn hammer slaps the string with a great amount of surface area. Between the large
surface area and the increased contact time with the string, many of the harmonics that we consider to be good tone are greatly
reduced or even eliminated.
In slow motion videography,
we now know that as a hammer moves forward to strike the string, it actually wobbles a considerable amount. Sometimes the
strings will contact the deep grooves of a hammer where the felt is compacted. The next time you play the note, it may sound
completely different in tone because the strings hit on the fluff between the cuts.
The process of surfacing
hammers peels layers of felt off the surface of the hammers down past the bottom of the cuts. This gives back a consistency
of tone much like when the piano was new. This can usually be done several times in the life of a piano before it is necessary
to replace the hammers.
Click on Pictures to view a larger size.
| From the factory |
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| After Surfacing |
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| Before Surfacing Hammers |
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| After Surfacing the Same Hammers |
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Key Bushing Replacement
Key bushings are small pieces
of felt glued inside the wood part of piano keys. They enable the key to slide with very little friction against metal pins
that keep the key in place. As a piano ages and is used, gradually the key bushings wear and the keys begin to wiggle from
side to side and even tip to the right or left.
The keys are one of the most
important parts of a piano because this is where we control our music. It is the only place we touch the piano (besides the
pedals). As key bushings wear there is a gradual loss of control, fingers begin to stumble because piano keys are not where
they are supposed to be, and children do not easily develop the ability to play without watching their hands.
Replacing
the key bushings will give back the control that the piano had when it was first new or in some cases…even better control.
Key Top Replacement
White piano keys are usually covered with one of two types of materials,
ivory or pyralin (plastic). Both types can have similar problems, they both can
chip they both can yellow and they both can wear from fingertips playing on them.
Chipping comes from something
being banged against usually the front part of the key and where it breaks off, the edges can be particularly sharp and even
draw blood. Yellowing can come from either cigarette smoke, keeping the lid shut
in the case of ivory (sunlight bleaches it), or the chemistry used in making the old plastic keytops when plastics were relatively
new.
Real ivory has
been banned from the import list because of poaching elephants for their tusks, so the only ivory that is “new”
is stuff that was already here in the US when they made the law. It’s hard to get hold of
and very expensive. However, there are oodles of pianos made here before that law that have real ivory on them, so many that
a perfect set of ivories adds only about $150.00 to the market value of a piano.
Because of the information
I just stated, I have gone to recommending replacing keytops with a new thicker type of plastic that doesn’t chip as
easily and being a more modern type of plastic with better chemistry, time has proven it doesn’t yellow with age. The result is striking, kind of like a big smile with new dentures. The new keytops are flat on top without any dips from fingertips wearing them down. This provides the best
result when you go to level the keys.
| Before |
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| After |
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Because the new keytop is
thicker than the previous keytop by a considerable amount, the key stick itself usually has to be planed down flat before
the new keytop can be glued on. As piano keys are different in width by a small
amount, after keytop replacement is done, there is usually some adjustment needed in the piano for proper clearance.
Key Leveling
The keys are the foundation
of the piano because everything else is based on the movement of the keys. The key must be high enough so that it can fit
properly within the case parts, be able to move deep enough and provide movement necessary for all the moving parts to function
properly and be able to keep the key in place without the key sticking.
Our fingers are extremely
sensitive and can tell the difference of even 1/1,000th of an inch. That’s about 1/3 the thickness of a hair
on your head. It is for this reason that key adjustment is so meticulous. Each note is individually adjusted to provide a
level keyboard where the keys are flat on top & not tipped to the side (square), spaced evenly, travel the right amount
for everything else to function properly (dip) with enough friction to keep the key in place without sticking (ease).
The parts we adjust are called
punchings and are made of various thicknesses of felt and paper. The paper punchings are color coded and come as thin as 1/1,000th.
of an inch. If the punchings are in good shape, we can just add or take away
as needed to control the key movement. In a case like this, you can expect 3
hours for this procedure.
When the punchings are worn, moth-eaten, or chewed
by mice, we have to start from scratch and replace all the punchings. When a piano is in this condition, you can expect about
5 hours.
Action Regulation
As a piano ages, normal wear
begins. In fact this is so normal, that manufacturers build in little adjustments to compensate for this wear. The wear I’m
talking about is due mostly to vibration, and compression of felt and leather parts.
After key work is done, we
have a solid foundation on which to build the action regulation. In short, regulation
is the adjustment of the geometry in an action so that it functions as efficiently as possible. Imagine the action as a transmission…you put in a certain amount of energy and it is multiplied. Instead of gears though, we have simple fulcrums and levers that create a ration of
1:5 or more. In other words, you play a note and the force is multiplied at least 5 times harder as the hammer hits the string.
Of course it’s a little more complicated than this, adding escapement mechanisms so that the hammer doesn’t block
against the string etc… but you can start to see the purpose of the action.
A few of the things that
action regulation does:
1. It provides
a consistency of touch and immediate control (makes all notes smooth & evenly the same)
2. It enables a greater dynamic range (the ability to play soft as well as loud)
3. It can increase
the speed at which you can play
Drawing of a vertical piano action
Drawing of a vertical piano action
Action regulation in other words
Action Regulation usually
takes about 2 hours in the piano for a vertical piano, more for a grand piano.
Damper Felt Replacement
Dampers are mechanisms that
absorb the vibrations of strings to silence them when not being played. If you stop playing the piano, but the piano doesn’t
get quiet, you might have a damper problem. Dampers lift off a string when a key is being played or when the sustain pedal
is depressed. It enables the note to continue sounding for a long duration. Dampers
are not made for all the strings on the piano, but only the strings that in the opinion of the designer have a long duration. You may notice that the last couple of octaves on pianos do not have dampers. The engineer who designed your piano decided that there was a point that the sound
died out quick enough not to bother with it. You can usually find this point
yourself by listening to the sound as you move up the piano not by note. The last note with a damper will be cut off as you
release the key, while the next note will continue ringing.
Dampers fail over time for a few reasons. The most common is they get too compact, hard & crusty from dust
impregnation and lose the ability to absorb vibration, they just bounce off the string when the key is released. Other reasons
are moth, rodents, or something being spilled into the dampers.
Damper Regulation
Because dampers are continually
pressed into the strings with springs, they get compacted (squished) over time and have different dimensions than the new
parts. This requires adjustment of the dampers after the felt has been replaced
so that they lift evenly with the pedal and also the key. These adjustments can be felt in the force required to press down
the key (touch weight) so these adjustments (damper regulation) are a must for a smooth consistent keyboard.
After the damper felt is replaced, damper regulation usually takes about 1 ½ hours in the piano.
Phone: 503-381-8289
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