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Quinn Connell

Engineering Design Portfolio 2014


Team Challenge: Design and build a robot to build a Lincoln Log cabin, stack rings on a peg, fit shaped blocks through their correct holes, and rescue a doll from a locked dog cage.

Solution: A robot which uses a single claw mechanism to accomplish all tasks. I was personally responsible for design and fabrication of the claw mechanism, front differential, and led systems integration and troubleshooting.

CAD model of a remote-control robot built for a course competition.

CLAW SUBSYSTEM DESIGN PROCESS Mock-ups helped vet design alternatives and unveil key specifications. In this case, such design parameters as claw dimensions, required holding torque, and optimal “finger” configuration were derived from the initial models. The final claw configuration followed the same strategy as the mock-ups shown; a servo-operated finger on a rack-and-pinion pinches objects between two fixed fingers. This allowed the machine to manipulate both curved and straight bodies with ease. Foam core mock-ups of the machine’s claw subsystem with pieces from the challenge.

CAD model of the machine’s grabber mechanism.

CLAW SUBSYSTEM DESIGN PROCESS Rear view of the claw mechanism.

Roller Brackets

Roller Axles

Plexiglass Rollers

Engineering drawings for the bracket, ready to be machined. Exploded view of the roller assembly which supports the rack-and-pinion.

The primary mechanism by which the claw operates is a rack-and-pinion linkage which moves the third finger. A set of plexi-glass rollers resists the bending moment generated by force against the finger and prevents side-loading on the servo motor.

Claw assembly on the final machine: front view.

Final CAD model of the claw subsystem.

Claw assembly: rear view. Pictured: roller assembly, rack-and-pinion lingage and servo motor.

CLAW SUBSYSTEM FABRICATION & FINAL PRODUCT All parts were CNC milled or lathed. The structural plates (brass) were brazed together on a hand-made welding jig. Motors and gearing were sized such that the claw opened and closed at a reasonable rate, and had sufficient holding torque. The vertical support plate interfaced with a vertical track which allowed mobility perpendicular to the ground. The claw subassembly worked reliably and performed well in competition.

R/C ROBOT Photograph of the final machine, fully assembled.


The machine performed well in competition and successfully completed all challenges. I led systems integration and troubleshooting; the largest issue we encountered was the lack of sufficient power to the lift motor. We provided more power to the motor by soldering a harness to allow it to be run off of two batteries in parallel. This required replacing the speed controller with a servo-operated switch.

MOBILE TACKLING TARGET –– CONCEPT DESIGN Need Statement: In order to decrease risk of concussive injuries, football teams are in need of a dynamic and mobile device or system which simulates player motion as realistically as possible in order to safely practice tackling form without playerto-player contact.

Solution: A free-standing dummy which is remotely controlled by a coach or other player. A novel uniball traction system is powered by opposing omni-wheels. This allows instant acceleration in any direction analogous to a player’s evasive motion. Geometry and weight distribution are designed such that the dummy is selfrighting, which cuts down reset time and allows for a high number of repetitions in a practice. Key specifications were derived from conversations with players, coaches, and data extracted from practices and NFL combine scores.

Ball-Driven Dummy.

Novel Ball Drive System.


Our team embraced an iterative design process. Initial proof-of-concept models led to more sophisticated prototypes of the drive system and continually informed design decisions. The use of modular, easily modifiable materials left room for design modifications and improvement.

Novel uniball traction system provides instant acceleration in any direction.


Revised drive system ready for fabrication.

A humanoid form figure creates a realistic tackling experience. Air-filled support adds stiffness without added injury risk or weight. A combination of closed and open-celled foam give structure and protection to internal components, while remaining soft, durable and weatherproof.

DIWHEEL VEHICLE –– HUMAN-CENTERED DESIGN A team of four engineers designed and fabricated a human-powered, two-wheel device from a limited set of materials. Considerations ranged from ergonomics to optimized power to the drive train. FEA failure and deformation analysis under static and dynamic loading conditions was performed in order to ensure performance, maintained balance, and minimize “sloshing.” Fabrication included extensive machining, welding and plasma cutting. All drawings were produced following GD&T best practices.

Novel clutch system (left, below) allows variable application of power for acceleration, braking and turning.


Vertical Arm

NX 8 FEA showing Von-Mises stress under maximum loading conditions in the “foot”

For the Naval Postgraduate School’s Space Systems Academic Group, I designed a quickrelease lift fixture for a satellite's ground support system. The previous design was cumbersome and difficult to attach and remove. Pictured is a foot-and-shoe mechanism in which the foot attaches to the satellite. The shoe slides on, and is attached through a vertical rod to a crossbeam. A shoulder bolt allows the entire arm to swing open for ease of use. A quick-release pin holds the shoe in place when no lifting force is applied to the crossbeam. The same assembly occurs on the opposite side of the crossbar, supporting the satellite evenly. *Satellite not pictured for proprietary reasons


Quick-Release Pin


Quick-release lift mechanism for easily and securely transporting satellites.

TRAVEL SPOON: INJECTION MOLDING Designed and injection molded a reusable plastic spoon for college students, intended to eliminate waste. Key ring allows easy transportation on keys or backpacks.

3-part tooling was CNC milled using AutoCAM.

BOTTLE CADDY Designed and fabricated a bottle holder which uses the bottle’s weight to stabilize the structure. Works with a range of bottle sizes, both full and empty.

Production involved SolidCAM, CNC milling, TIG welding, plasma cutting & powder coating.

Center of Gravity analysis to optimize the holder’s stability.

RUBIK’’S BALL Designed and rapid prototyped a 3dimensional, color-coded tessellating puzzle using icosahedral pieces.

Emphasis on GD&T for practical applications, interface with Z-Corp 3D printer, and spatial and aesthetic considerations.

A MORE PORTABLE LITTER Challenge: Create a wilderness rescue device that increases speed and ease of access to the victim. Decreased response time saves lives. CAD model of the final design.

Solution: A collapsible, lightweight, rugged, foam-core composite litter. “It would be great if you could make a cheap, light, backpackable litter that might not necessarily be rated for vertical lifts. Breaking down to less than half of the original size would be a huge improvement on what’s out there.” - Dan Schneider, Upper Valley Wilderness Response Team

A hand-made prototype in action.

A MORE PORTABLE LITTER: DESIGN EVOLUTION Required materials properties to implement the “Telescoping Frame” design put the cost of production beyond the scope of this project. We redesigned to a simpler, more elegant solution. In the “Folding Litter,” side panels fold flat to allow the bed to fold upon itself. When fully straightened, side panels erect and latch to end boards which provides structural integrity. The Folding Litter design proved to be a much more feasible and effective solution.

CAD model of the initial “Telescoping Frame” design.

CAD model of the folding design, fully collapsed (left) and fully assembled (below).

Foam core mock-up of the “Folding Litter.” Pictured mid-fold.

A MORE PORTABLE LITTER: PRODUCTION Hinged panels allow for a collapse to 1/3 the original size and quick, easy setup. Easily accessible anchor points and strict adherence to industry standards make our solution a safe, highly effective tool which is a significant improvement on the state-of – the-art. The final model was constructed using a multi-layer fiberglass/epoxy composite. For large-scale production, the most costeffective method would be to roto-mold litters in a single body using HDPE.

Fabrication of the final product: laying up fiberglass.

A wooden prototype of the folding design.

“That’s pretty damn spiffy!” – Captain Hinsley, Hanover Fire Dept

The final prototype: fully functional.


CAD model of a caulk gun, Complete with snap-on stock and grip.

At Logos Technologies, my supervisor used to joke that he wished the caulk gun had a butt stock on it. After I had finished all tasks on my last day, I designed a set of snap-on accessories ready to rapid prototype.

STATIC BALANCER For Logos Technologies I created an assembly to quickly and easily balance interface plates during production. During operation of payloads, it was important for all components to statically balance about a central axis. I designed and rapid-prototyped a simple setup which uses gravity to determine where ballast must be added. The assembly consists of a stand, axle, and collars which fit the interface plate precisely and connect to the axle through ball bearings. When perfectly balanced, the plate will spin freely and have no preferred orientation. Modular interface collars can be interchanged to balance similar components in the future.

An assembly to statically balance circular plates.


My initial truss design.

Later truss design, modified to minimize stress concentrations.

SolidWorks FEA of previous truss showing deformation under loading conditions. Color indicates Von-Mises stress.

Challenge: Design a truss to be rapid prototyped on a Z-Corp 3D printer which meets minimum clearance requirements and optimizes strength: weight ratio.

Solution: We approached the design iteratively with each group member designing and testing their own model in SolidWorks. As a team, we combined successful components from the individual trusses to maximize strength and optimize material use. The truss was able to support several thousand times its own weight and broke within 10% of the predicted value.

COURSEWORK/SKILLS SolidWorks NX AutoCAD Civil 3D Rapid Prototyping CNC & Manual Machining 2 & 3 Axis Mills Lathes Injection Molding Plasma Cutting MATLAB C Composites Instron Load Frame LabView SampleViewer Clean Room Best Practices

Six-Sigma Certified Solid Mechanics Computer-Aided Mech. Design Statistics Materials Science Environmental Engineering Naval Architecture Fluid Dynamics Thermodynamics Biomedical Engineering Lumped Parameter Systems Distributed Systems and Fields Basic Programming Physics Chemistry Differential Equations

CONTACT Quinn Connell Dartmouth College class of 2013 Thayer School of Engineering class of 2014 8000 Hinman Dartmouth College Hanover, NH 03755 (541) 868-6322

Connell portfolio 2014  

Engineering Design Portfolio

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