Since our initial project began, we have learned a lot about how the guitar functions. By conducting a survey of guitarists of varied skill level and experience, we identified several areas that users would wish to see improvements in, and developed four designs that we felt were well suited to address these concerns in a practical and economical manner. After some debate over the potential usefulness and acceptability of our plans, we have settled upon a redesign of the method in which the strings are mounted to the bridge.
Our final design is for a bridge with removable saddles. Each saddle is a removable unit that comes pre-assembled with the string already attached in a tight fit. The saddle fits on a rail, and is held in place by the tension in the string. The new design will increase the length of time the guitar stays in tune while greatly reducing the time and hassle for swapping out a broken string. The end result is a much lower maintenance guitar leaving the performer more time to play and less time fixing their instrument.
There are several primary stakeholders for this product: the manufacturer, the supplier, the novice users, and the high-end users. There is enough variety in the market today that any major changes or improvements could be adopted competitively. While there are many guitar bridge designs on the market, we chose to consider the Fender and the Floyd Rose bridges, arguably two of the most popular among modern players. Even among guitars featuring these two designs, there is a wide spectrum of cost and quality. This can range from around a hundred dollars for a beginner’s guitar to a few thousand for a high quality custom job.
The major needs for manufacturers are within the design specifications. While a manufacturer can make the part to whatever their clients ask, an extra degree of precision can increase labor costs by an order of magnitude. The raw materials are all common and fairly low cost, mostly stainless steel and occasionally brass. Another issue for manufacturers is assembly. The bridge itself is a moderately complex assembly with many parts to fit together, as well as fitting the bridge to the guitar and mounting the strings. These delicate operations add many operations to the assembly process, making it more expensive. One particular worry is the tension springs that act to counter balance the strings. These springs, located under the rear panel, are very difficult to remove or install. Another issue is that the two common bridges require different mountings, meaning the parts are not readily interchangeable.
The suppliers primary concern is the saleability of the guitar and related products (amps, guitar straps, tuners, picks, ect.) and as a secondary concern the logistics of shipping the product from the manufacturers, to the stores, to customers. The product must fit the range of customers the supplier caters to (see below), and all of the related products should still be compatible with any new product on the market.
A novice user, for our purposes, is any user who does not play the guitar at a professional level or for profit. While quality is important, cost is a significant limiting factor for their choices. Beginning guitarists will tend more towards a Fender bridge and overall lower quality of guitar, as the levels of precision for a high quality instrument will not have a pronounced effect unless the user has enough skill.
High-end users are professional musicians who will invest significantly more into the quality of their instruments, and for whom cost is less of an issue. These users will almost always use a Floyd Rose bridge, (or in some cases an electronic self-tuning guitar), high quality guitar components, and even pay a large sum for custom detailing work. For some musicians it is common practice to have several guitars on hand and an assistant who will re-tune the guitars after each song.
|Manufacturers||Retailers||Novice Users||High-end Users||Other|
|* Materials, cost|
* Materials, ease of use
* Level of precision required for machining
* Standardized screws and fasteners
* Ease of assembly
* Packaging space
* Compatibility with existing products
* Low maintenance level
* Maintenance level
|* Shipping size and weight|
* End of life breakdown
Description of Research
Our initial research began with the product dissection, where we learned what the most difficult parts of guitar maintenance were. We also have musicians within our group who are familiar with common problems and who ‘talk shop’ with other artists and know the trends of the industry.
The bulk of our research was conducted through a survey. We approached musicians from a variety of backgrounds and experience levels, from friends and family who play to a travelling band that stopped on campus and internet forums. There were several common themes that emerged which are discussed below.
Results of Research
Among the users we surveyed there was a wide variety of problems to address, as well as a long list of features to keep or improve. Responses covered everything from ergonomics and control layout to electronic systems, but two common themes were the most prevalent. The first was the tuning of the guitar. This was further divided between the difficulty to tune with a locking nut (a feature designed to keep strings in tune better when using a tremolo) and how quickly the guitar loses its tune while operating the tremolo. The second issue that we saw was maintenance, particularly the difficulty of replacing a broken string.
Our research into the stakeholder needs shows a lot of promise for innovation. There are several issues to be addressed with the use and function of a guitar, and each of them offers design opportunities. As our intent is to modify a sub-assembly of the full guitar, the needs of retailers and shipping take a secondary place – there is very little difference for them between our product and anything else on the market. Manufacturers will be one of our focuses – if the product is too difficult to create, then labor costs and end price will both increase beyond what the user is willing to pay. Our real focus, however, is on the needs of the end user and seeking to increase their overall satisfaction with the product.
After considering a wide array of potential designs to solve the problems we identified, we developed four solutions. Two directly address the tuning of the guitar, focusing on maintaining the tremolo function while improving the ability of the guitar to keep its tune song after song. Our other two designs sought to eliminate the cumbersome task of replacing broken guitar strings, shortening the process such that it could be done in a few moments on stage. After several revisions, the finalized designs are shown below.
Our first idea was a linear bridge. This bridge creates a vibrato effect by moving horizontally (with respect to the guitar body), instead of rotating. Instead of pivots and tension springs, the linear bridge would fill the bridge cavity with a high-strength track, a tremolo mounted on a “cart” on the track, and either compression or tension springs to return the bridge to pitch after the user releases the lever.
The linear bridge addresses the non-linearity we discovered in the string frequency vs. tremolo angle function that we derived in the first design . It would also address the tuning stability issues, as the track and cart setup would return it its exact starting position much better than a pivot system, and would not wear out nearly as fast. The linear bridge would be easy to manufacture, because the actual bridge plate and saddles do not need to be changed from current designs (either the Fender or Floyd Rose). The current bridge plates and saddles could be made to bolt right on to the linear track. Installation is also improved for the linear bridge. With the rotational bridge designs, installing the springs is a difficult (or even dangerous) task. The linear bridge would have the springs integrated into the unit, and installing the bridge would never require the user to touch them.
The digital bridge is an “outside the box” solution to the problems of standard tremolo designs, but one that addresses most of the issues far better than conventional solutions. Instead of using a mechanical system to change the tension of the strings, which is fraught with unpredictable factors and non-linearities, our digital bridge uses a digital signal processor (DSP) to change the pitch of the sound without ever mechanically adjusting the strings. The user controls the digital bridge in the same way he would a standard tremolo bridge. A lever is located next to the bridge which the user pushes down to lower the pitch of the strings. The lever is connected to a digital rotary encoder, which is connected to a DSP chip located in the tremolo cavity. The DSP changes the pitch of the bridge in proportion to the lever, emulating the function of a regular bridge.
The digital bridge addresses most of the issues of current bridge designs. Since the pitch change is accomplished digitally, the string pitches are always in exact proportion to each other, making the digital bridge the most musical design alternative we created. Because the physical bridge is fixed, not on any sort of pivot, tuning stability is not an issue at all. The cost and manufacturability of the digital bridge is very similar to that of current designs. The physical bridge is much simpler than a regular tremolo bridge, and the circuitry is relatively simple and not expensive to create. The only point at which the digital bridge is worse than current designs is installation. The guitar would have to be modified in order to accept the new bridge. This is not an issue when the guitar is being built with the digital bridge, but it would be a problem for users looking to retrofit their guitars with a new bridge.
The cartridge bridge works by eliminating standard string saddles, and instead features string “cartridges” that mount to the bridge base plate. The cartridge has a standard string, with a saddle built into one end instead of a ball end. The saddle would slide into and lock onto the bridge base plate, and the string would be secure and ready to be tuned up.
The cartridge system mainly addresses the issue that modern bridges are exceptionally hard to change the strings on. The cartridge system would allow you to quickly remove the old saddle cartridge and snap on a new one in seconds. Since the strings are securely mounted in the cartridges, the tuning stability will be better than conventional Fender bridges, and on par with more expensive Floyd Rose designs. The cartridges would contain pre-stretched strings, and would be precisely calibrated for string height and intonation, both of which would also improve tuning stability. The system would be easy to manufacture and inexpensive to buy, since most of the bridge parts are very similar to current Fender bridge designs. The cartridges would be inexpensive, made mainly of plastic with a few metal pieces. A pack of string cartridges would only cost a few dollars more than a pack of standard strings.
“Raccoon Trap” Saddles
The “raccoon trap” saddles would be drop in replacements for either Fender or Floyd Rose saddles. Instead of conventional string securing methods (usually a simple clamp or simply holding the ball end of the string), the raccoon trap saddle would integrate an internal one-way clamp (like a zip-tie). The string can slide easily into the saddle, but when the string is pulled on, the clamp digs in and the string will not move. The string could be released by pushing a button on the saddle.
The “raccoon trap” saddle addresses the issue of difficult string changes. Instead of frustration resulting from trying to feed an uncooperative string through numerous minuscule holes, the guitar player would simply have to push the string half an inch into the saddle, and it would be secure. Removing the string is even easier, requiring only a button press. Since the string is secured very well by the clamps, tuning stability would also improve. The saddles themselves will be made to retrofit into standard bridge designs, replacing the standard saddle. The “raccoon trap” saddles would be twice as expensive to manufacture as current saddles, but since standard saddles cost so little, this cost would not be particularly significant. The saddle would be made out of cast and stamped steel, and would only have a few parts, making it easy to manufacture and assemble.
Comparison of Designs
|Design||Fender Bridge||Floyd Rose||Linear Bridge||Digital Bridge||Cartridge Bridge||“Raccoon Trap” Bridge|
|Criteria||Weight||Datum 1||Datum 2||Design 1||Design 2||Design 3||Design 4|
|String Change Difficulty||3||0||+||+||+||++||++|
|Easy to Use||2||0||–||+||+||+||+|
All of our designs make significant improvements over the state of the art in most areas users are concerned about. The linear bridge and digital bridge are both unorthodox redesigns that show major improvements in most areas. However, they both would require major redesigns of all the bridge components, and possibly to guitars they are installed on. The raccoon trap saddles and cartridge design are more modest in their upgrades, but would not require modification of most of the components of the bridge to achieve their improvements.
Depending on the manufacturing and marketing capabilities of our client, we would not hesitate to recommend any of our design concepts. However, given the specific instructions given to us by Initech, we feel that the best design is the cartridge bridge. The cartridges combine major improvements with more modest changes to the overall design of the guitar, which will make it easier for Initech to manufacture and sell new guitar bridges. A cartridge design will also create a new market for guitar string cartridges, which Initech can capitalize on.
Comparison to the State of the Art
Benchmark of Performance and Function
The two bridge designs investigated, the Floyd Rose and the Fender, both are designed to answer certain questions regarding the performance of the musical instruments. The original Fender tremolo bridge was designed as a variant of a standard electric guitar bridge at the time. The Floyd Rose was designed specifically to address a problem with the Fender and earlier tremolo designs: the problem of keeping tune. However, the Floyd Rose was an imperfect solution, and also added a lot of complexity to the bridge design.
When we surveyed guitarists regarding problems they found with tremolo bridges, several problems came up more frequently than others. Tuning, the reason the Floyd Rose was developed, was mentioned often by guitarists. Additionally, the design of a guitar with a tremolo necessitates more difficult string changes, and this was mentioned in the survey as well. Another major problem noted was the inability to tune a Floyd Rose while the guitar is locked, something that was addressed with the addition of fine tuners to Floyd Rose bridges. There were other problems noted in the survey, including the difficulty of palm-muting a Floyd Rose-equipped guitar, general playing discomfort, and also specific issues with Fender bridges, like the ability to ‘dive bomb’ (use a tremolo to quickly plunge down to a low note).
The designs we are proposing are trying to address two key issues that have been problems with tremolo bridges: keeping tune and changing strings.
The Floyd Rose bridge was designed entirely with tuning in mind, and tuning has been the key issue for tremolo bridges since they began to enjoy wide popularity. The Fender bridge, as Floyd Rose realized, is not well suited to keeping tune, as the pivoting action the bridge uses puts tension on the strings and can distort them. Floyd Rose’s bridge uses a similar action, but uses a double-locking bridge to limit the degree to which the string can go out of tune. A linear bridge design would use an entirely different dynamic process to change the string length, pulling the strings horizontally instead of using a pivot in the bridge. This will hopefully improve the guitar’s ability to keep tune. Additionally, the design, though more complex than a Fender bridge, could be created with the same simple basic design as the Fender, with the additional parts being larger and easier to manufacture than the tiny saddle pivots and clamp blocks of the Floyd Rose. The electronic tremolo would be a way to create a tremolo effect without altering the strings at all, and therefore keeping the tune of the guitar easily. The cartridge bridge would allow for more secure string attachment within the cartridges, which would help keep the strings in tune, though not as significantly as the linear bridge design, or a standard bridge without a tremolo. The raccoon-trap saddle would not directly affect the action of the bridge, and therefore wouldn’t necessarily affect the tuning of a guitar, either negatively or positively.
Changing the strings on a guitar equipped with a tremolo bridge is difficult, because a tremolo requires the strings to be mounted inside the body of a guitar, which is more difficult than other string mounting methods. Both the Fender and the Floyd Rose have these issues, as both use essentially the same string mounting method. A linear bridge design could potentially allow for easier string changes, as the springs that typically provide tension would be mounted to the bridge, meaning that it may not be necessary to use a through-body mount for the strings. The electronic tremolo would make string changing easier by obviating the need for a tremolo bridge, and therefore allowing a guitar to use a simple Fender bridge without a tremolo, which uses a simpler string mounting method. The raccoon trap string design would make the string changing process for a through-body bridge much easier. The design could make it unnecessary for the strings to be passed through the sustain block and up through the bridge, a difficult process, instead having the strings be clipped into the sustain block very simply. The cartridge bridge design would make string changing very easy, it only being necessary to clip in a cartridge, rather than passing a string through a series of small holes.
Benchmark of Stakeholder Needs
The needs of the consumer are generally in line with the performance of the guitar. One other important consideration is ease of installation. Installing a new bridge on a guitar is not a difficult process, and is fairly standardized. If the guitar has a tremolo bridge, it would have a through-bridge construction, where the strings are mounted through the bridge into a sustain block, which is mounted to the body of the guitar. Of the new bridge designs being investigated, the only one which would require a major change to a preexisting guitar would be the linear bridge, which would use an entirely different internal setup with regards to the tensioning springs and the sustain block. It is also important to note that an electronic tremolo would require a different retrofit, installing new electronic components into the guitar. It would be much more difficult to install an electronic tremolo unit into a guitar than it would be to install a new bridge.
Another important stakeholder to consider is the manufacturer. Most of the new bridge designs are not significantly different from existing designs, so would therefore not be significantly more difficult to manufacture. Both the linear bridge and electronic tremolo designs would provide new challenges, but they wouldn’t be significant: the linear bridge could probably be installed in a way similar to other through-bridge designs, and the electronic tremolo would be installed in a similar way to other built-in pre-amp units like internal distortion units, which are already available on existing guitars.
Each of the new designs provides different advantages and disadvantages. The linear bridge addresses the problems of tremolo bridges well, but adds a lot of additional complexity. Both the cartridge bridge and raccoon trap bridge address one of the problems very well, but may not address the other primary issue as well as the other solutions. The electronic tremolo provides a different type of solution for both problems, but introduces problems of its own when it comes to how faithfully it can reproduce a tremolo sound.
The primary difference between two of the designs, the electronic tremolo and the linear bridge, and the other two, the cartridge bridge and the raccoon trap bridge, is which problems the bridge was designed primarily to address. All designs have the potential to fully address both primary problems, but this is something we may not know until more research and some prototyping has been done. Right now, the information we have is based on how the new designs compare to the Fender and the Floyd Rose bridges, and how the inherent flaws in these designs shaped the way the new designs were composed.
Team Member Roles
Team Planner & Organizer
Design Sketcher & Recommendations
Brainstorm and Survey Coordinator
Appendix A: Brainstorming Ideas
- Knobs that go to 11
- Knobs that only go to 11
- Bearing Pivot Whammy
- Whammy Damper
- Fine Tuner Whammy
- Plastic/Wood Bridge
- Cam lever tremolo
- Separate trem and string anchor
- Button for string lock
- Easy lock nut for bridge
- Piano key controls for string pivot
- Individual string tremolos
- Ergonomic Guitar Neck
- Pre-set Bridge Mount
- Altered Bridge Motion
- Friction Pad for fret hand
- Guitar with flamethrower
- Modular, replaceable bridge
- Elbow-use whammy bar
- Auto-fretting (keys over strings)
- Fret buttons
- Light Guitar
- Fret Clamps
- Vertical Rack and Pinion Bridge
- Guitars that don’t look like guitars
- Tuning ‘spell-check’
- Pump-action trem
- Player guitar (like player piano)
- Aluminum/Plastic/Ceramic Bridge
- Hinged string locks – straight motion
- Redesign parts to only use one tool
- Theremin guitar
- Secret message transition guitar
- ergonomic fretting
- Spray-on calluses
- Padded neck
- Tube Guitar (Guitar that fits in a tube)
- Travel Guitar
- Optical/Laser Strings
- Pre-worn guitar neck
- Pre-rounded frets
- Position sensor (‘Star Power’ trem)
- Internal amp controls
- Rubberized, bendable neck
- Two degree of freedom tremolo
- Knee-activated tremolo
- Split-actuation trem (one trem for lower 3 strings, one for upper three strings)
- Locking tuning keys
- Individual trem pedals mounted to guitar neck
- Interchangeable Guitar/Bass Head Units
- Nano-wound small strings for consistent composition
- Torsional Spring Bridge
- Rotational Saddles
- Thumb clamp saddles
- Thumb clamp nut
- Laser pickup
- Computer generated sound
- Button frets
- Electrical contact frets
- Tube guitar
- Alternative pickup types
- Non-horizontal translation bridge
- Alternative neck material
- Neck angle changed
- Tuners at bridge
- Tuners at bottom of guitar
- Non-metal strings
- Electro-magnetic bridge
- Magnetic strings
- Ceramic strings
- Ceramic bridge
- Wood bridge
- Hinged Bridge
- Bearing Hinge Bridge
- Fluid bridge
- Magnetic Levitation Bridge
- Electromagnetic string excitation
- Neck tremolo
- Folding neck
- Bending neck
- Round neck
- Cheap portability
- Motor at trem pivot
- Sensor at pivot
- Multi-pivot bridge
- Wider pivot contact
- Wrist use whammy
- Knee use whammy
- Palm use whammy
- Toe switch activated whammy
- Bridge position lock
- Bridge position friction system
- Larger angle rotation bridge
- Small diameter bridge
- Geared bridge
- Rack and pinion bridge
- Swing arm bridge
- Aluminum bridge
- Carbon fiber saddles
Appendix B: Reference Patents
Appendix C: References
“Callaham Tremolo Blocks.” Callaham Guitars. 1 Oct. 2008. Callaham Guitars. 6 Oct. 2008 <http://www.callahamguitars.com/blocks.htm>.
“Floyd Rose Tremolo.” A Amps Electric Guitar Store. A Amps Electric Guitar Store. 6 Oct. 2008 <http://aampselectricguitarstore.com/floyd-rose-locking-tremolo/>.
GanttProject. 6 Oct. 2008 <http://ganttproject.biz/index.php>.
Original Version <https://wiki.ece.cmu.edu/ddl/index.php/Guitar_bridge_redesign>