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Project 13: Larger Adaptive Walker


The name of the child we are involved with is Miguel. Most days, Miguel crawls along the carpet flooring of his house, sometimes pulling himself up momentarily by relying on the support of a nearby table or couch. The therapist and family thought a walker would work great for Miguel, allowing him to start learning to take his first steps, gaining lower body strength, and developing good posture.

Cameron Johnson, Thomas Dupont, Nicolas Capelle, Jonathan Bryan, Ethan Mabry

Problem Statement

Currently three years old, Miguel shows delay in the development of his gross motor skills. With that in mind, our chief goals for this project are to provide Miguel with the support he needs to learn how to walk and explore the outdoors he loves so much. Working hand-in-hand with the family’s therapist Ms. Cruz alongside Miguel’s mother, our mission is to design, model, and assemble an adaptive walker suitable for Miguel.

Design Specifications

  • Development – Supports and corrects posture as the child learns how to walk
  • Adjustability – The amount of support provided by the walker can be altered to accommodate each stage of development
  • Mobility – Offers some degree of independent movement to interact with the environment/surroundings
  • Comfortability – Useable for prolonged periods without causing discomfort
  • Reproducibility – The extent to which the components are commercially available or can be fabricated
  • Adaptability – Traverses through both indoor and outdoor terrain
  • Dependability – Supports the forces acting on the walker and provides a stable structure to lean against; remains balanced
  • Portability –  Made lightweight and/or smartly designed for ease of transport; fits through doorways with clearance

Background Research

Since we had little to no prior experience designing walkers, we started by engaging in some basic research. We learned that most walkers offer features such as height adjustable legs and are sometimes made to be foldable. At this point, we started asking some necessary questions amongst ourselves in order at the crux of what we want from this project.

Question 1: Wheels or no wheels?

Walker vs. Rollator 
  • Walker – Main frame supports the user by having stumps attached on the bottoms of four legs maintain contact with the ground while stationary and are lifted into the air when moving
    • Advantage(s)
      • simple and intuitive braking method
      • lightweight
    • Disadvantage(s)
      • requires user to briefly support his or her own body weight to walk
      • inflexible design
  • Rollator – Variation of the standard walker design where main frame supports the user by having wheels attached on the bottoms of the legs
    • Advantage(s)
      • fairly mobile
      • variation in design
    • Disadvantage(s)
      • quality of brakes affect when and how the user can stop motion
      • generally more complicated design

Answer 1: Choosing a rollator, a rolling walker, was a relatively easy choice since the physical specifications of an ordinary walker are probably too much for Miguel.


Question 2: How many wheels?

2-Wheel vs. 3-Wheel vs. 4-Wheel Walkers

  • 2-Wheel – A rolling walker where the two front legs have wheels attached on the bottom while the back two legs have stumps
    • Advantage(s)
      • most intuitive braking method
      • stable design
      • lightweight
    • Disadvantage(s)
      • requires weight to be placed on front in order to move
      • inflexible design
  • 3-Wheel – A rolling walker designed to be used on three wheels
    • Advantage(s)
      • highly mobile
      • easier to navigate tight spaces
      • customizable (seats, backrest, etc.)
    • Disadvantage(s)
      • some concerns involving general stability and potential for tipping over
      • depends on brakes to fix moving
  • 4-Wheel – A rolling walker designed to be used on four wheels
    • Advantage(s)
      • stable design
      • Fairly mobile
      • customizable (seats, backrest, etc.)
    • Disadvantage(s)
    • depends on brakes to fix motion

Answer 2: After some careful deliberation, taking the mother, the therapist Ms. Cruz, and even Miguel’s opinions into account, we moved forward on the assumption that a 4-wheel walker would best satisfy everyone, offering a middle ground between the rigid design of a 2-wheel walker and the mobility of a 3-wheel walker.


Question 3: What should the general frame of our design resemble?

  • We developed three different solutions to answer this query. These ideas became the basis for our three concept designs.

Answer A: We referenced the traditional design of a Klip 4-wheel walker produced by Circle Specialty.

Answer B: We referenced the design of the 4 Wheel Rollator walker produced by Drive Medical.

Answer C: We referenced the outdoor design for the Klip 4-wheel walker produced by Circle Specialty.



Concept Design 1

The first concept design remains heavily based off of the standard Klip 4-wheel walker design. That being said, our concept design  intends to convert a Klip walker, which is typically designed to be pulled by hand grips on the side, into a push model. In order to realize this design, the front wheels must be switched out for back wheels and vice-versa. Typically, turnable wheels are positioned in the front of walker to allow for a greater degree of maneuverability. Along with that, there are foot activated wheel brakes on two of the front walker wheels that can be used to lock the walker in place. The most distinctive feature of the depiction of a seat strap or harness to support Miguel’s weight. The last major adjustment to original design was the addition of two handles protruding out of the back, reminiscent of the back part on a wheel chair.

Concept Design 2

The second concept design takes one of the standard variations on a lightweight walker design and strengthens the overall structure. By overhauling a preexisting compact walker design and adapting it to suit Miguel’s needs, there are several unique benefits to this design. One of the most notable differences between this design and the other ones is the presence of hand activated breaks attached to the rear handle grips. With these, breaking becomes  much more convenient. Another point of interest lies in the fact that the front of this design is significantly more open than the previous design. For this design, Miguel can be placed into the walker from the front. In addition to that, this design also has room to accommodate additional features to support Miguel such as a seat or backrest.

Concept Design 3

Similar to the first concept, the general frame of the design was greatly inspired by the Klip walker, again making many of the same changes as was done with the first concept design. However, the specific reference for this one was oriented towards outdoor use. For this design, we considered how the duality rigid back straps and a flexible seat may improve Miguel’s experience outside. The walker possesses foot brakes to lock the wheels in place. This time these brakes are positioned on the back wheels for ease of use. Moreover, the walker offers areas on the side and front bars for which Miguel can hold onto.

Decision Matrix

Overview of Selected Design

The selected design that we finally chose is a four-wheel walker equipped with 8-inch wheels. We selected this size of wheel because the walker is supposed to be used indoors and outdoors. The two front wheels are swivel wheels, and the back ones are straight, to allow a higher degree of mobility. In order to support Miguel’s weight, we will design a piece of trunk support. We will use bicycle parts to set up brakes on the handles of the walker so that the person accompanying Miguel can brake. The brakes affect the back wheels.

Describe Design Details

  • Frame – A foldable and height-adjustable aluminum frame for ease of transportation and to accommodate Miguel’s growth. Including the rest of the features, it weighs about 17 lbs and can support up to 150 lbs.
  • Wheels –  8” outdoor wheels that allow for travel both indoors and outdoors.
  • Hand Brakes – The mother can use the brakes on slopes or whenever she wants the walker to remain stopped.
  • Trunk support – A loop of aluminum tubing meant to support Miguel’s upper body weight.
  • Pannier – Used for storage of Miguel’s toys so that the walker provides some sort of entertainment.

Engineering Analysis 1

The walker will include a handlebar for Miguel to push/pull himself up. Because of this, some amount of stress will be introduced in the handlebar. We assumed a force of 100lb would be applied to the handlebar and that it would act at the middle.

  • Max moment = 2400 lbf*in
  • Max bending stress = 35.82 ksi


Assuming the product is made of an aluminum alloy with an allowable stress limit of approximately 40 ksi, the handlebar will be able to withstand Miguel’s weight.

Engineering Analysis 2

We felt it was important to calculate the minimum force required to push the walker to ensure that Miguel can push it himself. Because the walker will be used outside frequently, we assumed the surface to be gravel, as that is probably this highest friction value the walker will encounter.

  • coefficient of friction = 0.4
  • weight of walker = 17lb
  • Minimum force to push walker = 6.8lbf


Miguel should be more than capable to push the walker, even through a surface like gravel.

Engineering Analysis 3

Since the goal is for Miguel to rely less on the supports as he learns to walk, it is useful to understand the stresses flowing through the trunk support. Most notably, the trunk support is bore entirely by two small aluminum weld tabs.

  • Stress through a single weld tab is 133.333 psi

As such, the load passing through the weld tabs is at an acceptable threshold.

CAD Drawings

Bill of Materials

Document Fabrication Process

  1. Assembling the Main Body – The walker was assembled as a push walker with the outdoor wheels.
  2. Cutting Aluminum Tubing – Aluminum tubing was cut into four 45° equal length sections and sanded down.
  3. Welding the Trunk Support – The four pieces of aluminum are welded to form a square brace.
  4. Cutting the Radius Weld Tabs – Four weld tabs are cut from aluminum, shaped to fit around the edge of the pipe.
  5. Completing the Trunk Support – Holes are drilled through the back legs of the walker and cleaned up with a grinder. Then, the radius weld tabs are welded to the the square piece of aluminum tubing at a slight angle to match the slope of the legs on the walker.
  6. Welding of Brake Parts – Brake parts on the second walker are either cut or disassembled. The slots for the handle arms are welded onto the back arms of the walker. Two aluminum weld tabs are cut and welded onto the back of the walker.
  7. Assembling the Brakes – With a hole drilled slightly above each rear wheel, a set of spacers can be used to offset the brakes over the outdoor wheels. After that, the springs on the brakes were compressed by tightening the brake nuts until the braking mechanism reached the wheels.
  8. Spray Painting the Walker – Blue Epoxy spray paint was used to coat visible parts of the walker that had paint scratched off or faded from previous steps in the fabrication process. The walker was disassembled and reassembled as needed.
  9. Applying Foam – Adhesive spray was used to bond the foam to the the aluminum pieces. These strips of foam were cut to cover any dangerous elements on the walker and make using the walker more comfortable. Zip ties bound the foam tightly to the walker throughout the sticking process. After the foam had settled, the zip ties were cut off the walker.
  10. Finishing Touches – Boxcutters were used to cut out patches of the foam coverings, and sandpaper was used to clean the spots up. Bolts and screws were retightened. Wheels were cleaned with cleaning wipes. The seat bag from the second walker was linked between the aluminum trunk support and the front of the walker. Finally, the walker was folded for ease of transport.

Testing Results

  • Front Wheel Test – The walker usually encountered a probably while being pushed. There were design faults with the base walker that cause the front wheels to become stuck in a backwards orientation. To counter this issue, the front wheels were broken in as much as possible. This aspect of the walker was tested for improvements all throughout the entirety of the design process.
  • Support Test – Weight was placed on the trunk support of the walker to test its ability to support weight. The walker was still able to be pushed if force was applied horizontally through the trunk support.
  • Foldability Test – At every step of the process and in between some steps, the walker was tested to see if it still achieved maximum foldability. The first major hurdle was seeing if the walker could still fold with the trunk support passing through the legs. Some orientations of looping the brake cable could prevent the walker from folding all the way. Other than that, some patches of foam were removed as they inhibited proper folding.
  • Brake Test – The ability of the brakes to engage the wheels was tested from motion to stop. Forces were used to push the walker, testing the amount of force required to break static friction while brakes were set to park.
  • Sharp Edges Test – The walker was searched for potentially sharp, harmful spots and edges. Parts of the walker could be tested for sharpness by placing hand and fingers over the tested areas. Any potentially dangerous spot that could not be cleaned up by filing or grinding the general vicinity could be wrapped in foam.
  • Foam Shear Test –  Foam pieces were sprayed with adhesive and stuck on scrap pieces of aluminum tubing. By tearing the foam from the sections of test tubing, we were able the understand roughly how much shear force was necessary to separate the foam from the walker. Moreover, we were able to see how segments of foam would tear when exposed to a shearing force.

Completed Design Photos

Instructions for Safe Use

  • Stuck Wheels – Preferably, use the walker alongside Miguel as he starts learning how to walk. The orientation of the front wheels can be corrected by the parent/guardian lifting up on the back of the walker.
  • One Directional Rear Wheels – While beginning to walk, maintain the one directional mode by leaving the clip down on the back wheels to prevent the walker from rolling backward and lower the maximum speed.
  • Folding the Walker – Remember to squeeze from the bottom of the legs when folding the walker. Similarly, remember to pull out the bottom off the legs when opening the walker.
  • Brakes – Keep sharp object away from brake lines, and avoid engaging the brakes while fingers or appendages are located under or around the back two wheels.
  • Foam Padding – Do not use the walker for prolonged periods of time if the foam exterior of the walker is missing. If the foam padding falls off or tears, reapply some of the foam padding on the missing section before the next use.

Project Summary/Reflection

                                                                                                                                                                                                                                                                                    This was a necessary experience that forced every one of us out of our comfort zones. We had to approach each issue from a variety of angles. In the process, my group and I explored many of the resources here on campus and worked with a lot of different people to complete our project. Working as a team together with Ms. Cruz, Miguel, and his mother was a great opportunity. They were all wonderful people to work with every step of the way. Of course, there were more than just a few issues along the way. Still, I believe we managed to do more good than harm. Truthfully speaking, this project turned out significantly better than any of us could have anticipated at the start of the semester. After some encouragement, Miguel was able to support himself and push the walker around for short spurts. The excitement on the boy’s face. The gratitude of the mother. The overwhelming sense of accomplishment and simultaneous disbelief that lifted up each one of our expressions. Bearing witness to that sight, any lingering traces of exhaustion or discontent with how this project turned out was soon replaced with a deep and abiding sense of satisfaction.


2024 Spring