Group 1 2012 Gate 2
This section deals with the documentation of the dissection of our piano as planned in Gate 1. This plan laid out the ground work for the piano dissection, but in practice it required more problem solving and planning as we took on each step as a group. This included what we were going to do with the individual parts as we removed them from the piano in a way that would insure that the pieces were kept intact as well as have some sort of organization. Beyond dissection, we will analyze the interactions between parts and subsystems.
Possible Corrective Action
On the whole, our work and management plans have proven to be at least moderately successful:
- The dissection of the piano that was completed in almost the amount of time we allotted.
- We have continued progress update meetings after every MAE 277 lecture.
- The often resulting group meetings have done a good job of keeping us relatively on track to meet our self-imposed and actual deadlines.
One of our biggest problems is still attendance. Meeting directly after MAE 277 all but ensures timely meeting attendance, but our main meeting for this gate was on a weekend, and several group members showed up somewhat late or not at all. The absence of the group member during the actual piano dissection has proved very problematic, as they have less insight into the workings of the piano and very little knowledge of the steps we took to dissect it, which impacts their ability to contribute to the write-up of Gate 2. We will continue to stress the importance of attendance.
Our other most pressing problem is our inability to effectively work on important sections of the wiki pages simultaneously. We discovered during gate one that there is the possibility of accidentally overwriting work done by other gate members working on the same section if one saves after they do. To date, we have attempted to avoid this by having everyone work on different sections, and also having them prepare their sections in external word processors, but it became somewhat complicated to coordinate and took significantly longer to update key sections of Gate 2. In the future, we will most likely stress the use of word processors instead of the actual wiki pages.
As a general rule, no part of the piano is truly meant to be taken apart by a consumer. The top hatch lifts up to expose parts of the action, and the bottom baseboard can be removed fairly easily without tools, but other than that, everything requires the use of a screwdriver to remove. That said, a screwdriver is really the only tool actually needed to take the entire piano apart. Almost all of the piano, save for those structural sections which are laminated together, is held together by screws. This results in the physical difficulty of each step being both highly similar and remarkably low. This causes the main difficulties of every step to be caused more by required delicacy of handling of parts and the amount of thought that is involved in deciding which part to take apart and how to get at them.
The following is the difficulty scale we will use to describe the difficulty of each step outlined in the deconstruction in the piano. To allow for flexibility in actions taken in the steps, difficulty ratings will be given for each separate column. For instance, a step that requires one person to spend twenty minutes and has a moderate logic component would be denoted as "1-3-2".
|Scale #||Number of People Required||Time Taken||Conceptual Difficulty|
|1||One Person||<5 minutes||Readily Apparent|
|2||Two Persons||5 to 15 minutes||Some Investigation Required|
|3||Three Persons||15 to 30 minutes||In-depth Investigation of Parts and/or Planning Required|
- Flat Head Screwdriver:
- Most of the components of the piano were held together with basic flat head screws of various sizes. The flat head screwdriver was used for all of these components, and they were all directly reachable at their respective points in the dissection.
- Some of the components were simply held together by compression in slots or with pegs. To remove these parts we used the pliers to ensure precision and safety of the fragile parts.
- The only component that required the use of a wrench was the dissection of the pedals.
Action Internal Subsystem
The action as a whole contains the hammers and mutes, but within the action, there is a separate subsystem that takes input from the keys and pedals and operates the hammers and mutes. It consists of a pull-rod connected to the keys, a lever to operate the mute and a push rod that operates the hammer. To the right is an animated gif of the action-hammer-mute subsystem working. The hand is pulling the rod typically attached to the keys(See figure on right.).
The keys are the most easily accessible levers on the piano and serve as the primary input. They have no axle or spring; instead, they rest on a point on the bottom of the key and fall into place by weight balance. They transmit work done by the player's fingers to kinetic energy within each subsystem in the action.
The hammers are felt-covered, wood levers that transmit kinetic energy into the strings.
- They have light springs to return them to rest position.
The mutes are felt pads that press against the strings to dampen sound. They are on steel levers and use strong springs. Mutes for the lowest notes have two felt pads that are closely formed to match the thicker strings. The mid-upper notes have flatter pads. The highest notes do not have mutes because their sound dies out quickly without a mute.
The right pedal operates a metal bar that raises all the mutes off the strings simultaneously. A wood lever along the bottom of the piano on a spring operates the push-rod to transmit motion to the metal bar. The metal bar also has a spring to return it to rest position.
Una Corda Pedal
The left pedal operates a wood bar behind all the hammers. It moves them closer to the strings so they can't gather as much kinetic energy in their swing. The resulting sound is more quiet. The wood lever across the bottom of the piano is on a spring. The wood bar moves under the influence of gravity.
Strings and Cast-Iron Frame
The strings and cast-iron frame are on the back of the piano. The strings are meant to resonate at a frequency based on their length and mass. The lower notes are thicker and therefore heavier due to a wrapping of thicker wire around a basic steel wire. The cast iron frame supports the tension in all the strings.
Support Frame and Case
The piano's action and strings are housed in a wood case. The case has a top that can be propped open to allow more sound to propagate through the surrounding air. The back face of the case is made of a thinner wood with stiffening ribs. This so-called soundboard is directly attached to the cast-iron frame and strings and it allows the vibrations in the strings to produce sound outside the piano.
The front of the case supports the keyboard so it has upright posts to brace the keyboard against force from the player's hands. It also contains a fold-out cover to prevent accidental damage to the keys.
The entire case rests on four wheels to ease movement of the piano.
The action subsystem is a main hub of system input and output. It receives input signals and energy from the keys and pedals and outputs energy and signals to the strings and cast-iron frame.
Primary Input Interaction
The primary inputs of the piano are the keys and pedals. The keys send discrete signals based on which key is pressed and analog signals based on the relative force with which the key is struck. The pedals send binary signals.
The input signal from the keyboard to the action subsystem is in the form of material and energy. Which key is pressed determines which individual pitch section of the action is activated and the energy input to the key determines the output energy. The action sends the signals and energy to the hammers and mutes by striking the hammer and lifting the mute off the string for the note corresponding to that key. Once the key is released, the action subsystem instantly dampens the sound with the mute and allows the hammer to fall back to rest position.
The sustain pedal operates across all mutes in the action. It lifts all mutes off the keys to let any note to continue sounding after the player releases the key. It effectively bypasses the signal to the mutes from the action.
The una corda pedal operates across all hammers. It moves the hammers closer to the strings to prevent them from accumulating as much kinetic energy through their swing as they do without the pedal.
Final Output Interaction
The strings, cast-iron frame, and case all serve as part of the final output. The output is entirely sound energy. The inputs are analog signal and energy from the hammers and binary signal input from the mutes.
Which hammers have been activated and the energy associated with their inputs determines the pitch and volume of the sound output. The mutes determine how long the note continues to sound.
The keyboards and pedals are oriented to allow an ergonomic playing position. The action subsystem is positioned centrally between the keys, hammers, and mutes so that it can receive direct inputs and send outputs to those systems. It is also oriented linearly across all the notes to provide equal signals to all note outputs. The pedal push-rods run up the side of the piano and operate bars across all the notes. That way, they don't interfere with the action subsystem by running up the middle, yet it can still modify signals to all the notes.
Global, Societal, Economic, and Environmental Factors
A piano is a mechanical device, with all of the subsystems being interlinked via physical connections. The keys and action are directly linked through a system of levers and springs, and they send discrete and analog signals in the form of mechanical energy from the user inputs, being the keys and foot pedals, through the action to the hammers and mutes. The energy is converted from mechanical to acoustic by the strings, and the signals become acoustic signals. Because of this, the strings and soundboard are the only component which is not physically connected to the action, but the hammers do make physical contact with the strings during operation. This gap between the mechanical action and acoustic subsystem is necessary for this conversion of energy to take place. An upright piano is much more cost effective than a grand piano, in that it is smaller and requires less material to manufacture, with the cost of a lesser acoustic performance. The inner workings of the action are constructed almost completely from wood, which creates a fairly durable design, but is much less costly than any form of metal or plastic, and generally will result in better acoustic performance. This economic drive can also relate to environmental reasons, as wood is readily available, and is a renewable resource. Being constructed of mostly wood, the piano also tends to have an appeasing look in the home as well. The arrangement of the subsystems in an upright piano differs from that of a grand piano, in that they are in a more compact arrangement. This makes an upright piano much smaller and more household friendly. The main drawback with this type of arrangement is a slight decrease in acoustic performance. The action is directly adjacent to the keys because it allows for more responsive input, since the distance between the keys, which act as levers, and the action is smaller, and therefore will respond quicker and most likely have less maintenance issues. The action must be adjacent to the strings and soundboard in order for the mechanical energy to transfer properly.
All knowledge in this section of the report was obtained from our elementary and/or background knowledge of pianos, physics, and this pdf: http://www.ptg.org/userfiles/file/learningCenter/How_A_Piano_Works.pdf