The Straightstrung, Overdamper, piano

Overdamper means that the darnpers damp the strings above the hammer strike line. Straight strung means all the strings are parallel including the hass ones.


Again this type of piano is made of 3 major assemblies;


1. The strung hack


2. The casework


3. The action and keys.


1. The strung back assembly.

This is similar to the chipping back we have just dealt with except it will not have the modern design features. The strings are not overstrung but parallel throughout. This means that you cannot get such a long bass string into the same height piano as compared to an overstrung piano. It also doesn't have a suspended bass bridge but one that is directly fixed to the soundboard and may be a continuation of the long bridge. The bass bridge goes a lot closer to the edge of the soundboard in the bottom left hand corner which together with the shorter bass string, gives a poorer tone. Because the soundboard bridge is discontinuous, caused by the iron frame bracings chopping the long bridge into distinct lengths, you find the last note of the tenor break and the first note of the treble break tend to be poor.


The grain of the soundboard is usually horizontal and the belly bars are vertical otherwise the soundboard is made in the same way as a modern piano.


This type of back will probably have a three quarter iron frame (finishes at the top bridge) and not webbed (frame doesn't cover the wrest plank). Though there may ie a decorative iron moulding around the wrest plank which gives the impression of a full iron frame, it is separate and provides no support to resisting the pull of the strings.


The overall string tension is less on this older type of piano so a webbed iron frame was not essential.


You will notice too that often the bass section has a pressure bar which is possible because the strings are not angled. This may be a reason why bass strings in overdampers don't appear to break very often when pitching.


The older overdampers have "pin bridges" meaning that there is no pressure bar but instead the top hridge has the same system as the soundhoard bridge ie. a top and bottom bridge pin.


There is little or no difference in the back bracings. You never have a hackless overdamper because the iron frame was not strong enough to cope by itself.


Finally you may come across a piano with the strings all parallel but at an angle of 11 to 5 o'clock. We call that oblique stringing.


2. Casework.


We will divide this into 2 groups, those parts which are removable for tuning or repairs purposes, and those which are glued or screwed on.


Removable parts; 1. Half top which is hinged to the hack half top. It swings hack to reveal the wrest pins. Nearly always has mouldings aroundits edges. 2. Top dooris the panel which covers the action, held in place by dowels and clips. Often it is a framework with several panels plus mouldings. The hanging music desk is screwed to the top edge and will swing inside the top door when not wanted. 3. Back hollow and fall. The top door sits on the hack hollow which is a quarter circle in section and the fall is hinged to the hack hollow. Often you find the makers or dealers name on the inside of the fall. 4. The nameboard rail or stretcher rail is either screwed to the underside of the back hollow or to the key blocks. Quite often the makers or dealers name may be on this.


On its underside is glued a strip of nameboard felt so if a key rises up the balance pin it won't click against it.


The following items are removable for repair purposes: 5. The lock rail on which the fall rests. It contains a lock to keep the fall closed and is screwed to the keybed from underneath by 4 screws. 6. key blocks are found either end of the keys inside the cheeks. They may he screwed to the keybed or the cheeks themselves. 7. The hottom door lies helow the keybed covering the strings and pedal work. Again held in by clips and dowels, often panelled with mouldings.


Non-removable caseparts: 1. The back half top which is glued to the top of the back bracings and covers the wrest plank.


2. The ends are the "sides" of the piano glued to the sides of the back bracings.


3. The cheeks are glued and screwed to the insides of the ends and provide support for the keybed and hence the keys and action.


4. The pallisers are the pieces of wood between the bottom door and the ends, not always present though.


5. Toes plus castors. The toes are glued in the angle between the bottom board and the ends. They extend out the front to hold the front castors. They are often a laminate of 4 pieces of pine for strength.


6. The plinth is a thin plank of wood on which the bottom door sits. It is glued to the front edge of the bottom board and there are 2 central slots in it through which the pedals protrude. These pedal holes are lined with baizes.


7. The keybed is included in the casework because its front and side edges are visible below the lock rail and cheeks.


8. Columns or brackets are pieces of wood which support the keybed from the front

toes. A bracket touches the palliser, a column does not.


9. Bottom hoard is the hase hoard of the piano onto which the pedals and back castors are fixed.


Old casework finishing; there was a lot more craftsmanship in the old pianos as labour was far cheaper, there were rnore panels and mouldings, the columns or brackets were more ornate. Sometimes the case parts were solid wood, mahogany, rosewood, walnut or oak. But usually the base wood was pine with a wood veneer covering, so this thin veneer could be any type of wood including ebony or rosewood which are expensive. At the time overdampers were made, dark finishes were popular and french polish was nearly always used. This type of finish was applied by hand and gradually built up so it was very time consuming. The finish was not resistant to heat and water.


3. The overdamper action and Keys.

Qualities required of a keyboard. A. quickest possible response from key contact to the sound produced. B. an even touch so volume can be predicted from the force one puts into a key. C. requires fast repetition so the note is ready to play again as soon as possible after having been played.


We shall deal with the action in 2 parts, the framework and the action members.


1. Action framework. a. the action standards are the vertical supports at either end of the action to which all the action rails are secured. They sit on blocks from the keybed and clip into place on blocks screwed to the inside of the ends of the piano. Nearly always made of wood, maple, beech oak or hornbeam though high quality overdampers may use metal, cast iron or mild steel.


b. the damper rail lies on top of the action standards, held to it by a screw in each one. This rail secures all the dampers and the damper lift rail. There may be a

central support for this rail by a bolt from the wrest plank and it is this that may obscure access to certain wrest pins. Rail is made of maple or oak or perhaps beech. On the underside is a strip of cushion felt which stops the damper bodies rising too high. Overdamping is a poor system because it is less efficient to damp above the hammer strike line compared to below it, but also this long damper rail is pron-e to warping and twisting and throwing the damper regulating out which makes the damping even worse. Again on quality pianos this rail may be of mild steel.


c. damper lift rail is found running across the underside of the damper bodies. It is hinged to the damper rail by 2 flanges and on its top side is cushion felt so it is quiet when it lifts the dampers. It is made of maple or perhaps mild steel in high quality pianos.


d. hammer rest rail is the one on which the hammer shanks rest. It is made of maple or oak and covered with a thick hammer rest baize or 2 layers of cushion felt with a nameboard felt covering.


e. action beam rail is a highly shaped rail which holds the levers and hammers in position in relation to the strings. It is made of beech or maple and has nearly 200­screw holes in it. It is reinforced by a mild steel bar running near its bottom edge for about 5 octaves. This is necessary to prevent twist on the wood which would throw the regulating out. Its other function is to secure the following 2 action rails.



f. the set-off rail is found just above the feet of the jacks and may be in 1, 2 or 3 sections. It is held onto the action beam rail by special screws which have forked heads, flattened bodies and threaded ends. Small screws on the rail slot between the forked ends and tighten down. The rail is made of beech or maple. For each note there is a mild steel set-off wire is a wooden set-off button (maple or hornbeam) with a cushion felt pad on it where it hits the foot of the jack. There are 2 or 3 securing screws for the rail per section. The function of this rail is to cause the jacks to trip out of the notch before the hammers hit the strings.


g. the jack slap rail (repetition rail) lies just above the set-off rail. It is a thin wooden rail covered by cushion felt on its hack surface whose job is to stop the jacks coming too far out of the notch and so improve repetition. Made of maple, it is secured to the action beam rail by special screws which have flat heads, and 2 opposite threads on their stems. As you screw them into the action beam rail the slap rail also moves along the stem. There are 2 or 3 securing screws per section.


Action members of the overdamper action.


There are 3, the damper, hammer and lever.


1. The damper. The damper head is a wooden moulding (maple or hornbeam) hollowed out and filled with damper felt made from merino wool. The ends of the damper felt fibres rest on the strings as this is more effective than actually lying on the strings. The damper felt is sandwiched between 2 thick pieces of nameboard felt. You will notice the length of the damper heads taper from the bass to the treble section as less felt is needed to damp thinner strings. Notice too that the last batch of damper heads are different in that the heads are very much smaller and they clasp a thin, hard type of damper felt. The felt needs to be thin and hard here to get between the hammer striking and the top bridge. The gap between hammer strike line and the top bridge diminishes as the treble section is reached. Beyond the 65th damper it is impossible to put a damper head between the top bridge and hammer strike line. That is why you can't overdamper the entire compass of the piano.

Overdamping is now defunct because damping below the hammer strike line is far more efficient (you can prove this on a chipping back.)


The damper head is held onto the damper body by a right angled piece of mild steel wire which has threaded or fluted ends. The damper body is a wooden moulding (maple or hornheam) into which lead weights are inserted. A hass damper has more lead in it than a top treble one because it is harder to stop a big fat string vibrating. This tells you that the strings are damped by gravity operating through the lead weights.


The damper flange is made of maple or hornbeam. The inside face of the flange has a recess in it which fits over a raised strip on the damper rail to give automatic spacing. The 2 holes in the arms of the flange are lined with bushing cloth so that the flange can move around the nickel­plated brass centre pin. The centre pin is held firm in the damper hody. The damper arm is the wooden moulding which is centred onto the end of the damper body, and holds the long damper wire. This wire screws into the damper arm and is locked in position by a small wooden dowel. The damper wire is bent to give clearance of the hammer rest rail and the bridle wires. At the bottom of the long wire is the lift dowel with cushion pad which is lifted by the lever section.



Overdampers have 65 dampers which can be removed collectively by undoing the 2 securing screws in the action standards. Then press the damper lift rail upto the damper rail, slide the damper rail off jthe standards, then lift slightly to pull the wires out of the lever holes. When replacing again grip the damper lift rail to the damper rail, slide the rail onto the hass action standard and put the screw in loosely, then slide the treble end on and screw in loosely. Reconnect the damper wires to the levers l~y starting with the very first bass damper as sometimes there are more levers with damper holes in that there are dampers.


The overdamper hammer




Also called the top section it is the part that hits the string. The hammer head consists of 2 parts, the wooden moulding (maple or hornbeam) and the hammer felt made from merino wool which is highly compressed. The hammer head moulding starts life as a single strip, its point tapers towards the treble section. A strip of hammer felt is glued onto the moulding under great pressure and heat. Mild steel staples through the whole head secures the felt further. The individual heads are then cut out.


Please note that the hammer felt is more dense in the treble section as the heads have to resist the cutting effect of the thinner treble strings. There is more felt on the hass hammer heads as you need a weightier hammer to set the larger strings in motion. The part of the hammer felt that touches the strings is called the hammer nose.


Piano tone depends on the hardness of the hammer felt, how thin or rounded the nose is, and whereabouts on the string it strikes. Soft, rounded noses give a mellow, soft tone. Hard, angled noses give a hard or harsh tone. Striking near the top bridge gives a harsh or even shrill tone. New hammer felt is very hard and has to be voiced or toned.


The hammer shank is of maple or perhaps hornheam and glued into the head and butt by scotch or animal glue. This glue dissolves with heat and is not waterproof. The hammer butt is the "body" of the hammer section and its limbs are the shank, the balance hammer shank and butt flange. The butt is of maple or hornl~eam. The butt notch is the angle formed between the notch leather and the notch cushion; it is in this that the top of the jack sits. The notch cushion is made of cushion felt and is glued on the notch ledge. The notch leather is glued into a groove in front of the notch ledge and also just below the halance hammer shank. The nap of the notch leather runs upwards so that the jack has a smooth ecscapement from the notch causing little wear to the leather. Underneath the leather are 1 or possibly 2 undercushions which help keep the leather supple from the eompressing effect of the jack. These are made of boxcloth.



Please note, lost motion is a gap between the top of the jack and the notch leather. The balance harnmer and its short shank are made of maple or hornbeam. It is covered with a skin of leather again with the nap upwards so when it meets the check head it will not cause excess wear (the balance leather always wears before the check felt). The linen tape is glued into the balance hammer hole, rarely it is glued to the butt. The butt flange is centred to the butt by a nickel-plated brass centre pin. The inside face of the flange has a recess in it to line up with the raised strip of the action beam rail. The butt screw is made of mild steel.


Overdamper lever section.


Also known as the whippen, bottom section or undercarriage. It has 5 functions. 1. Its

heel contacts the key dolly. 2. Its jack pushes the hammer towards the string. 3. Its bridle wire holds one end of the tape. 4. Its check wire holds the cheek head. 5. The lever body lifts the damper wire.


The undercarriage heel is the graphited or boxcloth covered block under the lever body which contacts the key dolly. Made of maple or hornheam. If the heel is boxcloth covered the key dolly will be graphited and vice versa.


The jack may he direetly centred to the lever l~ody or to a jack flange which is glued to the lever body. Made of maple or hornbeam, it may be slimmed to bypass the securing screws for the jack slap and set-off rails. Its head and foot are graphited to reduce friction as it rubs against the notch leather or set-off button. The back edge of the top of the jack is slightly bevelled to help the jack slip back into the notch. The jack spring or spiral spring is made of nickel plated brass and is held in position by circular grooves at its base. If there is a jack flange then the base of the spring is glued to the lever hody. Spiral springs vary in length from half inch to seven eighths.


The mild steel check wire has fluted or threaded ends. The check head if of maple or hornbeam and covered with check felt which is a very firm felt. The mild steel bridle wire also has threaded or fluted ends, it holds the tape end.


The damper wire hole is bushed with bushing cloth or a thin boxcloth to prevent rattling noises. Sometimes you will find that there are more levers with damper holes than there are damper wires. There should be a small gap between the damper wire lift dowel and the lever body if the notes is well regulated. The lever flange is made of maple or hornbeam.


The overdamper keyframe


Consists of 3 rails. 1. The backtouch rail. 2. The balance rail. 3. The front touch

rail. All these rails are normally linked by thin wooden slats in 3 or 4 places so the whole keyframe can be taken out as one unit. Each rail is screwed to the keybed by 4 screws, please note that there may be packing (card or veneer) between the rails and the keybed. Make sure this packing stays in its place or the key regulation is thrown out.


1. The back touch rail is the rail on which the hack of the key rest. It is simply a piece of wood (pine or basswood) onto which is glued a strip of back touch baize. In some old pianos 2 layers of cushion feit is used instead of a single piece of baize. If this rail is packed up, it will remove lost motion from the action and reduee the depth of touch.



2. The balance rail has mild steel balance pins hammered into it so it is made of beech. This is the tallest of the 3 rails because the key has to rock on it. The balance pins are like nails with round heads, and at the base of each one is a cloth halance washer and perhaps some paper ones used in key levelling. If packing is placed between this rail and the keybed the fronts of the keys are higher against the lock rail and the depth of touch is increased.


3. The front touch rail is again made of beech (sometimes oak) as it has mild steel front touch pins (hat pins) in it. These hat pins are so called because they resemble miniature cricket bats. At the base of each 5,at pin is the front touch baize which may have paper washers under it used to regulate the depth of touch. If packing is put between this rail and the keybed, depth of touch is redueed throughout and stice versa.


The whole keyframe is screwed to the keybed which is very much like a miniature hack bracing system, made of pine or spruce. Usually the base of the keybed is covered with a thin ply.


Overdamper keys.


The key is the input end of the piano machine; the distance you depress the front of key by (depth of touch) is multiplied five times in the distance that the hammer moves. You may press the key down by 9 millimetres, then the hammer moves 45 millimetres.


A set of keys start life literally as a key board, the board being made up of several butt jointed pieces of basswood, quarter sawn to prevent twist. The holes for the bat pins and balance pins are drilled out and the already hushed keychase is glued on top of the key over the balance hole. On the eheaper overdampers there was no keychase and no balance bushings.

The celluloid key covering may be glued onto the key hoard so when the individual keys are cut the covering is cut also. This would not apply to ivory which is very much more expensive so you can not afford to waste any. Celluloid was an early plastic, cheap but would yellow with age and was inflammable. It was applied as one

piece. Ivory used on the better class pianos was applied in 2 pieces, the head and tail; it too yellows with age but was not inflammahle to the same degree. The joint between the head and tail leaves a very fine line between the two. Ivory has an individual pattern on it like finger prints. Celluloid was patternless or had a "grained effect". The key front was always celluloid even if the top was ivory. For the key covering of the sharps ebony was used, stained black and polished.


After the keys have been cut the dolly wires and lead weights were added. Basswood is used for keys hecause it is light and regularly grained and has few knots. Sometimes linden lime, spruce or pine was use.


There are several different ways in which the key may contact the heel of the lever. 1. The commonest one is for there to be a mild steel dolly wire with a wooden dolly threaded to its top. The dolly may he flat with a cushion pad on it or be curved and

burnished with black lead. You turn the dolly up or down to adjust lost motion. 2. Quite common is the pilot cloth and pilot screw. At the hack of the key is a countersunk pilot screw whose top is covered by a flap of boxcloth which is glued to the key. To adjust lost motion you lift the pilot cloth flap and turn the pilot screw up or down. In this situation the lever heel is burnished. 3. On rare occasions you might have a key carriage on the back of the key. This is a small piece of wood with an upward extension rather like a balance hammer which contacts the lever heel. The extension may be covered with boxcloth or burnished. To adjust lost motion you turn the grub screw in it as necessary then finally tighten the securing screw.


Advantages and disadvantages of key coverings: ivories are hard wearing, resistant to scorching, have individual patterns or grains, have a nice feel but cost 300 pounds for a set these days. Like celluloid they yellow with age and are difficult to match if one has to be replaced (rather like teeth). Normally it is just the head that needs replacing. To whiten them you would need to scrape them or bleach them in sunlight. Celluloid was cheap but easily burnt with a cigarette, difficult to match for replacements. Grained celluloid tried to imitate ivory. Galalith was another early plastic, soon discarded because it was found to blacken when in contact with human sweat.


Overdamper pedal systems.


The left pedal is the soft or celeste pedal, the right pedal is the loud or sustain pedal.


1. The sustain pedal lifts all the damper heads off the strings so notes played will eontinue to vibrate and cause other notes to vibrate in sympathy according to the harmonic series of the first note. In this way the sound of a note is embellished. In the overdamper action the damper bodies are lifted upwards by the damper lift rail, causing the damper heads to arc downwards off the strings. The vertical pedal rod moves the darnper lift rail up and down.


This rod is glued at its base onto the pedal rocker and guided near its top by going through a bushed hole in the action block. The pedal rocker acts like a seesaw, if the pedal end goes down the pedal rod end goes up. To achieve this seesaw action the rocker may he pivoted in one of several ways:


(a) the rocker may he screwed to the bottom board on its raised centre which provides the pivotal point. In this case it needs a spring to return it back to position. This may be a leaf spring screwed to the underside of the rocker at the pedal end pushing against a piece of leather on the bottom board. Or it may he a coil spring in a similar position rather like a giant jack spring. This system is most typical of overdamper pianos though it is a poor system because the rocker can move sideways on its central screw as well as up and down and the leaf spring is liable to make noises.


(b) the rocker may pivot within the arms of a huge flange (cradle), a mild steel pin going through it and the cradle. The cradle is glued and screwed to the bottom board. The returning spring may be a leaf or coil spring made of sprung steel. The cradle and pin provide a very clean pivot.


(c) in the more modern overdampers the rocker may be pivoting on a "u" spring so called because it is like a "u" on its die, screwed to the underside of the rocker and to the bottom hoard. Because it is a spring it provides a pivotal point and the returning mechanism. It is very popular in underdamper pianos but the rocker can move sideways as well as up and down. Sometimes the spring may be in the shape of a "t" or "z".



At the pedal end of the rocker, the pedal hook goes through the rocker, through the bottom board and through the pedal itself and hooks underneath it. There is a piece of leather between the pedal hook and the pedal where noises can he created as the leather hardens. As you know, on the end of the pedal hook is a baize and pedal nut for adustment which alters the amount of lost motion in the system. Normally there are padded blocks glued to the top of the bottom board which the ends of the rockers hit to prevent the pedals being depressed too far.


The pedal is of mild steel with a brass capping welded on where the pedal is visible. The pedal pivots on the pedal hinge which is screwed to the underside of the bottom board. Squeaks often develop between the pedal hinge and the pedal.


On the more modern or more advanced overdampers you will find that the pedal is housed on the top of the bottom board so is much easier to work with. This type of pedal system will be dealt with in underdamper pedal systems.


2. The celeste pedal system quietens each note played by bringing a piece of soft celeste felt between the hammer nose and the strings. The eeleste felt is of tapering

thickness glued to the eeleste rail; it is thick in the bass and thin in the treble. When the pedal is at rest, the celeste rail plus felt lies just below the level of the hammer strike line. On pressing the pedal the rail is lifted up so that the felt is hit by the hammers. Obviously hoth ends of the rail must lift at the same time so there are 2 pedal rods one at either end. The rods. are glued to the pedal rockers at their bases. Near the top of the rod is a slot in which a serew is located. The rod moves up and down on this screw.


The rockers pivot exactly like the rocker of the sustaining system but since there are 2, where they meet above the pedal they are recessed into each other and a single pedal hook passes through them hoth and then into the pedal itself. In this way one pedal can lift the 2 celeste rods at once.


Materials used: many woods are used for the celeste rail, the rods and the rockers; maple, beech, oak or pine. The pedal springs are of sprung steel, pedal hinges of

mild steel. The holes in the plinth through which the pedals go are lined with haizes and decorative nameboard felt. Boxcloth, haize, leather, cushion felt is found on the tops and bottoms of the pedal rods.


You may find that some overdampers have got a half blow system on the left pedal but we shall deal with this in context of the underdamper piano.












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