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Project 7: Crawl / Stance Assist


The goal of this project is to design a device that can assist a set of infants in learning to crawl. We will analyze multiple designs to find the one that best suits our use case.

Team Members: Kanin Shull, Axel Olivera, Christian Sunday, Mario Armanios

Problem Statement

There are two infants who are getting ready to crawl but do not have the strength or coordination to do so. The children need an assistive device that can reliably support their weight and allow them to crawl unobstructed.

Design Specifications

-Frame: It must support the weight of the children, without obstructing their range of motion. It must also fit through doorways as small as 29 inches.

-Harness: the harness must be able to be adjusted to fit both children, and support their torso and head. the harness will need to be removed so that it can be washed.

-Wheels: the wheels must be able to roll over small obstacles, such as thresholds in the house.

-Strength: the frame and harness must be able to support the weight of the children, preferably with room to grow.

-Weight: the entire device must be light enough to be moved by an infant.

Background Research

For background research/Inspiration, we focused mainly on one device called the Creepster Crawler. This product most closely fit our initial ideas and was suggested to us by the family. It utilizes a 7-point adjustable harness suspended by a 4-wheeled frame. It does not however, provide any head and neck support.

Concept Design 1

Concept 1 is a 4-wheeled frame that features adjustable legs. The legs can be adjusted to different angles to control the width of the frame and allows easier storage. the harness is attached to the frame using adjustable clips so that it can also be removed. The head support is separate from the body harness so that it can be removed when no longer needed, and features a “ring pad” so that the child can still see through the harness.

Concept Design 2

Concept 2 is a circular frame with 4 legs attached at the top, and wheels attached at the base.  This design features a stance-assist bar on either side so that way the children can progress from crawling to standing. The harness design for this concept is also different.  It is more of a large “hammock” rather than a dedicated harness.  It features 2 arm and leg holes as well as a face hole for added neck and head support.

Concept Design 3

Concept 3 is similar to the other designs, the only difference being that it is not a circular nor rectangular frame. The “legs” are connected to each other in order to make it foldable and easier for storage. This design also features a harness so the baby can move freely, with the upper body being the only part of the body being attached to it.

Selected Concept Design

We did not proceed with any of our initial concept designs, but combined multiple favored features from each.

Decision Matrix

Overview of Selected Design

We decided to create the most simple version of our concept designs, minimizing complexity to save weight; focusing primarily on efficiency for both the child and the parents.

Describe Design Details

The design will be constructed out of two bent, single-piece arches, connected by multiple horizontal support beams. The entire frame will be made out of 1-inch diameter 6061-T6 aluminum tubes with a wall thickness of 0.065 inches to keep the frame as light as possible. There will be four 2-inch casters, one on each corner. The harness will be connected to the frame in seven different locations using adjustable buckles so that the lengths can be changed and the harness can be removed for easy cleaning. There will be two sideways holes in the harness so that when the child gets old enough the device can be rotated and used as a walker as well.

Engineering Analysis 1

By using an estimated possible weight that a child might weigh while using our device, the summation of forces in the y-direction, the moment of stress about the upper bars where the straps will attach, and the factor of safety could be found.  Our calculated factor of safety is 8.21.

Engineering Analysis 2

Calculating the total volume of aluminum used in the frame and multiplying by the approximate density of 6061-T6 aluminum, we can find the expectedd weight of the aluminum frame.

Engineering Analysis 3

Calculating the deflection in the Aluminum and force required to bend

CAD Drawings

Bill of Materials

Document Fabrication Process

  1. First we had to cut the tubing sections to the required length
  2. Once the tubing was cut to length we had to bend the two 8ft sections of pipe to create the support arches
  3. we then cut the ends of the 27-inch pipes at a 1-inch radius so that they can be welded to the arches
  4. then we had to machine 4 threaded inserts to weld in the bottom of the arches, so that the casters can be threaded into the pipe
  5. We welded the entire assembly together and powder coated it a blue color to match the harness
  6. Finally we screwed in the casters and attached the harness using the removable straps

Testing Results

After final assembly we tested to confirm that the frame was very easy to roll along the ground, and that it could support our weight without any signs of stress.

Instructions for Safe Use

The child should be put inside of the harness, and the harness should be adjusted for a comfortable fit ensuring that the height from the ground is set per recommendations of the physical therapist

Project Summary/Reflection

We did have to deviate from our initial concept designs, to ensure that the crawl assist device was as simple and light as possible. However we believe the final design does include all of the necessary adjustable elements to accommodate the children. Overall, we were able to complete the project for around half the price of a similar retail device. We hope that this will be the tool the family needs to aid with the children’s development.


2023 Fall