Nate Watts and Maxine Laroche Agenda Standards Testing plans Frame DesignFEA LeverRatchet SystemFeasibility Brake Mounting System Caster Design Folding Systems BOM Next Stage Plan ISO Standards ID: 776066
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Slide1
All-Terrain Walker
Angel Hambrecht, Justin Kibler,
Nate Watts, and Maxine Laroche
Slide2Agenda
Standards
Testing plans
Frame Design/FEA
Lever-Ratchet System/Feasibility
Brake Mounting System
Caster Design
Folding Systems
BOM
Next Stage Plan
Slide3ISO Standards
ISO-7176-3 Determination of effectiveness of brakesForce needed to apply brakesDistanced traveled with brakes appliedISO-11199-2 Requirements and Test Methods-RollatorsStability-tipping conditionsDurability- support weightBrake handle positioning
Slide4Frame Design
The frame is to be welded aluminum or steel tubing. Using FEA, a size of 1” OD and a thickness of 1/4” for aluminum and 1/16” for steel was selected. There is a compromise between frame strength and frame weight. After discussing frame design with RIT’s Baja team, steel is the likely candidate, but aluminum is still an option.
The shape of the frame is an adaptation of existing walker designs. The wheelbase was extended for increased stability and other dimensions were determined using center of gravity calculations to prevent tipping on inclines.
Slide5Finite Element Analysis
The frame of the walker was modeled in Autodesk Inventor. It was tested with Inventor’s built in FEA software using our worst case scenario of a 250lb user. The FEA confirmed that the frame design will hold up under the load and will safely support the user.
Slide6Lever-Ratchet System
A team from Cambridge designed an attachment for wheelchairs that adds the hand drive system that we were looking to incorporate into our walker. Their design is open to the public and files of the parts are available so anybody can 3D print them. We will be printing a set and slightly modifying them to use with our walker. The system attaches to the wheel spokes, not the axle. This allows them to be attached to a wide variety of wheels.
Slide7Lever-Ratchet System Feasibility Testing
To test the feasibility of the hand drive lever-ratchet system we attached sockets to a set of wheels that we put on a rollator walker. Socket wrenches were used in place of the previously mentioned system. Our testing proved that a user can easily propel themselves around on flat and inclined terrain with little effort which supports our preliminary torque calculations.
Slide8Disc Brakes
Our brake rotors and calipers were designed to be fitted to a mountain bike frame. A special bracket will need to be machined and fitted to the axle to secure the rotor and a plate will need to be welded to the frame to fit the caliper. There will be two sets of brake handles, one set on the frame and one set on the hand drive handles. Using a cable splitter we are able to route both sets to one brake caliper.
Slide9Caster Design
The 12” front wheels of the walker need to swivel to allow the user to change direction easily. Most purchasable casters of this size are much too heavy to accommodate our design and they will not work with our bike wheels. We will be machining a custom set of casters from aluminum to reduce weight and increase functionality.
Slide10Foldability
The current frame design has the walker folding front to back, with a hinging device in between the two rods going to each front wheel. The current idea is to have a locking hinge that inserts itself into both ends of the tubing being used for the frame, with O-rings to prevent water from going inside the frame. The hinges would be pushed on the side to unlock and move the arms to the desired position.
Slide11Handle Adjustability
One of the requirements of our design is adjustability in the handle position to accommodate different user heights. The height will be adjusted using a design similar to the one shown in the picture.
Slide12Current look at Bill of Materials
Slide13Current look at Bill of Materials
Slide14Current look at Bill of Materials
Slide15Plan for Final 3 Weeks
Machine drawings and FEA - JustinPurchasing and quotes - NateImplement standards and manage EDGE - MaxineCreate and implement test plan - AngelSecond phase of test rig build and gathering faculty input - All
Slide16Questions?