Miniature Pediatric Posterior Walker - Horizontal Style

This semester our group was tasked with designing and building a mini-walker for a 2-year-old named Nehemiah. Nehemiah has a genetic condition that has caused a development delay for him. He weighs only 12 pounds and cannot provide his legs with enough support to stand and move independently. His physical therapist has a handful of experience with children with developmental delays and stressed the importance of taking early precautions of teaching one to stand and move independently while their bones are in an early stage of development.

After considering a range of mini-walkers, she could not find a walker that accommodated Nehemiah's height and width. Thus, with the help of our instructor for this course, our goal was to design and build this mini-walker which would gradually allow Nehemiah to have stability in his mobility.

1x Aluminum Round Tube, Aluminum, Alloy Type 6061-T6, 6 ft, 0.745 in Inside Dia., 7/8 in Outside Dia.

1x Aluminum Round Tube, Aluminum, Alloy Type 6061-T6, 6 ft, 0.87 in Inside Dia, 1 in Outside Dia.

2x Debris-Resistant Standard Plate Caster, Rigid, Polyurethane, 175 lb, 3 in Wheel Dia.

2x Debris-Resistant Standard Plate Caster, Swivel, Polyurethane, 175 lb, 3 in Wheel Dia.

1x Heavy Duty Casters, Lockable Bearing Plate with Brakes, 360-degree Swivel, 375 lb, 3 in Wheel Dia.

2x 1/4 in. x 2 in. Zinc-Plated Universal Clevis Pin

1x 2-Piece 1/4 in. Zinc-Plated Hitch Pin Clip

1x Aluminum, Flat Bar Stock, Thickness (Decimal) 0.125 in, Width and Length 3 in x 24 in

1x Spray Paint and Primer

16x 1/4-20 Bolts, nuts and washers

Our team met with Nehemiah's mother and physical therapist, who both explained his condition to us and showed the benefits a walker like this could bring to him. We talked through how and where Nehemiah would use the walker to inform our design features and specifications for the walker.

His physical therapist took specific measurements:

• hip width
• hand width
• hips to the floor
• elbows to the floor

The minimum design requirements to ensure Nehemiah has enough support while using the walker included having wheels with resistance and additional forearm support for him to put pressure on.

Because Nehemiah has difficulties supporting his legs in a standing posture, we designed the walker with the primary goal of practicing gaining the comfort of standing before moving independently.

The design is relatively simple with inspiration drawn from existing walkers - an aluminum frame that accommodates switchable caster wheels while having armrests and handles on the top.

Fusion360 was used to create the necessary CAD models. Dimensions and requirements given by the physical therapist were taken into consideration when designing the walker.

Hand grips, armrests, and caps to cover tube ends were 3D printed.

MakerBot 3D printers were used to produce the parts. Parts were printed at 100% scale with a higher than default Infill density, and an increase in shell count to increase their strength.

Foam padding would later be added to the arm rest to ensure a more comfortable experience.

A flat plate of aluminum was sheared into four pieces that would act as mounts for the caster wheels:

• Four holes were drilled into each individual plate to fit bolts through the plates and caster wheels.
• Each plate was filleted on all edges to make sure that accidental collisions would not hurt.
• The plates were milled in the center to be welded from below.

Two tubes were bent into a 'U' shape using a tube-bender: one for the base of the walker and another for elbow and hand support.

A small section of tube was cut off and both ends were made into a shape of a half-cylinder using an electric cut-off tool. This section would fit perpendicular between the top and bottom U-bars as support.

The top u-bar had a series of holes drilled into them on both sides to accommodate the adjustable armrests.

The tubes were cleaned to avoid having impurities when welding. Then, the U-bars, vertical bar, and plates were assembled and welded together. To ensure the walker was stable structurally, a rosette welding was performed. It gave a clean and neat finish to the joints.

The final assembly was polished and painted. A layer of primer was applied to the surface to ensure the coat of paint would last, before painting over the primer.

Epoxy was used to joint the handles and caps to ensure a strong bond between the metal and plastic.

A different set of caster wheels can be attached and switched out to fit different criteria. We included two sets of caster wheels in our build; one set with brakes and another set without.

Nehemiah tested out the mini walker to check for fit and comfort. Overall feedback was good with one exception, the distance between the armrests would make it uncomfortable for Nehemiah to rest his arms on. Our team took the walker back to the lab to make final modifications.

We needed to reduce the width of the hand grips. Using a one-inch pipe and two t-joints, we created a horizontal bar across the top u-bar. The bar is kept from moving using clevis pins and is fitted with two new 3-D printed hand grips.