Fahad Al-Subaiei, Matt Joganic, Harvest Montemayor, Samuel ZerbibDepartment of Mechanical Engineering, Northern Arizona University; Karin Hallberg, Professor of Music Education

Research

Final Design

Acknowledgments

AbstractFiona Carroll is a thirteen-year old girl who has been playing the violin under the instruction of NAU Music Professor Karin Hallberg since she was three years old. Born with an atypical cleft hand, she is unable to hold a bow without a special apparatus. Her previous attachment design had evident limitations; it was uncomfortable, very heavy and made certain bowing techniques impossible to perform at the level of skill necessary for advanced playing.

The team’s objective was to develop a new attachment that provided improved and unrestricted movement during practice and performance. Through modern materials and innovative ideas, our design will giver her better grip on the bow while providing improved sound quality.

Reviewed old attachment

• In constant contact with bow hairs, affecting sound and performance

• Made of ebony

• Lacks custom fit

PrototypingPrototyping PhaseThis phase was essential to our project’s success. Rounds of prototypes were developed from the design concepts and each one tested by Fiona. Each prototype shown had a different variable changed such as texture, hole size, number of holes, angle and distance between fingers. Her feedback on each of the prototypes provided the team direction toward the final design.

Figures: Materials from top left to right; Green foam, MDF, pine, redwood, black HDPE, grey PVC with red polyurethane inserts, opaque LDPE .

• We would like to acknowledge and thank Karin Hallberg• Thank you to Fiona Carroll and her parents• Thank you to Jeff Robinson for his expertise• Thank you to Carl’s Plastics of Minneapolis

Classified hand conditionHelped us obtain a better understanding of her range of motion and muscle strength• She has full range of motion in her wrists

• Missing tendons that allow knuckle bending

• Movement in thumb is only in one plane

Problem Definition

Requirements1. Weight of the attachment should not exceed 15 grams2. Design will be custom fit to her hand and finger dimensions3. The design will provide a non-slip surface 4. The design does not change the violin bow itself in any way5. Will allow Fiona to play with better dynamic contrast

Design and construct a light-weight, custom-fit bow attachment that will allow Fiona to continue her musical career with comfort and confidence.

Fiona’s current violin bow attachment is heavy, adding 28 grams to the already 52 gram bow, and greatly alters the bow’s balance point. It lacks a custom fit as her hand has grown, She has had the attachment for two years and it has cracks propagating through it. Her hand tends to slip out of the finger holes when playing fast strokes. The current attachment comes in contact with the bow hairs, reducing the playable length of the bow.

Figure 1: Karin Hallberg playing using her bow, no attachment

Figure 2: Fiona playing with her old attachment

Figure 3: Fiona playing with our new design

Sound Defined While the most basic sound will contain only one frequency, resembling a sine wave, instruments produce sounds that contain an infinite mixture of sine and cosine waves. The reason that we hear only one sound is that one of these frequencies has the highest peak, this is called the fundamental frequency.

Method In order to analyze and contrast the sound produced by Fiona using her old and new attachments, her instructor Karin was recorded playing the same sounds.

The three images to the right are a selection from De Beriot’s “Violin Concerto,” each spectrum was created by selecting the same note from each recording.

Results Fiona produced many harmonic overtones past 10,000Hz using her old attachment (Figure 2), that do not appear in her instructor’s spectrum. These disappear when she plays with the same bow, but with our new design

Her fundamental frequency is shifted to the right with her old attachment; her frequency corresponds to her instructor’s highest peak when using the new attachment

Conclusions

‘A successful attachment should be simple, light-weight, comfortable,’ advice of Adrian Anantawan. professional violin soloist; he is missing his right hand and uses a bow attachment while playing.

In order for us to minimize material used, and thus make the attachment as light as possible, a 3-D model of our design was drawn using a computer aided design software called SolidWorks.

Once we had concluded the prototyping phase of the project, our team had enough feedback from Fiona’s experiences using those prototypes to proceed confidently toward a final design.

Sound Analysis

Design Analysis

Design Concepts Design 1Figure: Left; This design was to be composed of two carbon fiber rings that would be light-weight and adjustable along the bow.

Design 2Figure: Left; This design includes a fit-form insert material, such as polyurethane. Soft inserts should improve comfort and grip-ability.

Design 3Figure: Below; This design uses a ball-joint between the attachment and bow. It creates a tripod action improving leverage and gives a greater range of motion.

• Universal fit, will fit on any bow, anywhere along bow

• Thumb hole is no longer in contact with bow hairs

The final design file was created and analyzed in SolidWorks and compared to Fiona’s old attachment. Fiona’s violin bow was modeled from point cloud data using a NextEngine 3D-scanner and then imported to SolidWorks for analysis.

Main findings of this analysis include:

• The bow’s moment of inertia with the new attachment more closely resembles that of a plain bow

• Improved center of balance

• Much higher strength than

• old attachment

Figures: From top; new attachment design as a rapid prototype part, surface generation from 3-D cloudpoint data from Fiona’s previous attachment and center of balance of Fiona’s violin bow, all modeled in SolidWorks

• Our goal was to make a bow attachment that would make Fiona as comfortable as possible when playing

• We have made Fiona a lightweight, long-lasting attachment that fits her hand and can be moved to any bow she may buy in the future.

• Fiona has already seen improvement in technique and comfort since playing in a Master’s Class with Adrian Anantawan and her new attachment.

Features:

• Two-piece design

• Weighs 12 grams

Figures: X-ray of Fiona’s hand and a photo of her old attachment. Courtesy of Mark Carroll.

Figure: Above; A ball joint assembly connects the violin attachment to a plaster model of Fiona's hand with glove.

Center of balance measured from frog end:

Plain bowBow with old attachment

Bow with new attachment

11.2 “

9.4 “

6.6 “Frog end

Figures: Counter-clockwise from top right; SolidWorks model, new attachment made of Delrin, Fiona using new attachment.

Fiona’s Bow