On February 2nd we left to meet a 11 month-old girl with Spina Bifida. Due to her condition she has little to no use of her legs and her body size closer resembles that of a 5 month-old. Thus a hand-powered trike would have been impossible for her to operate until near the age of 3 or 4. However, the Physical Therapist suggested building a crawler. After watching the young girl, with assistance, inch her way across the floor we were all convinced that it would be something productive for her to own. This will help teach her to crawl, as well as improve her overall body control and hopefully improve her lifestyle in general.

Design Specifications

1. Safety - Crawler must be easy for child to be placed into and move about without causing harm.
2. Adjustable - The harness should be allowed to move up and down to compensate for her growth.
3. Comfort - One issue was that the crawler she tried would rub her face, we either need a different support system or softer padding.
4. Efficient - This crawler should be designed to ease friction on wheels and make it easy for her to move across the floor.
5. Affordable - The components we use must be sufficient enough so that there are no worries on safety but cost effective.
6. Appealing - This is a small girl, so the crawler should look desirable and something the parents can be proud to show to others.

Measurements:
Shoulder - 16 cm
Top Length - 17 cm
Arm Length - 22 cm
Hip to Knee - 18 cm

Design Concepts

Our designs range from:

the use of 3 wheels or 4 wheels
a collapsible frame for ease of storage
rotatable top to allow a 360 degree range of motion
softer padding on harness to ease skin irritation
Detachable handles

ORIGINAL CRAWLER:

After studying the original we decided to create 3 different design concepts simply modifying from the initial crawler.
The harness used below is designed specifically for crawlers therefore we will not be modifying the harness but how it is attached.

Design Concept 1

Original Crawler (We know it works and can modify for specialization)
Fixed frame with swivel wheels

Design Concept 2

Still uses the 4-wheel base like the original crawler
Rotatable top for an increase in manuverability
Possibly a wider frame to ensure no contact points with child

Design Concept 3

3-wheel base
Static frame like that of the original

This design allows the child to have more freedom of movement and a more compact design. The drawbacks are the lack of handle bars or a seat for the parents to lay on while helping the chid.

Design Concept 4

Combination of all of the above
3-wheel base
Rotatable top

Concept Evaluation

Rated 4-1; worst to best
Consideration	Design 1	Design 2	Design 3	Design 4
Ease of Use:	4	3	2	1
Cost:	2	4	1	3
Weight:	3	4	1	2
Motion/Manuv.	4	2	3	1
Ease of Construction:	1	4	2	3
Appeal:	4	2	3	1
Total	18	19	12	11

After much brain-storming, discussion, and including the results shown above the consensus is to proceed with Design 4.

Design Overview

After meeting for the preliminary design review we spent some time revisiting ideas such as the rotatable harness system and 3-wheel design. The following analysis is considering the stress distribution along the curved beam (legs), the stresses being produced when looking at the entire mechanism, and lastly determining the radius from the central point to the wheels. This was a key analysis point because we needed to be certain with the rotatable harness support system that Lauren would not be able to rotate into a strut.

Engineering Analysis

On only the curved beam, assuming it is a solid bar.

Bill of Materials

Part	Supplier	Quantity	Cost
7/8 OD, 1/16T GALVANIZED STEEL TUBE	LOWES	2 length (10ft ea.)	$ 8.90
SVIVEL GRY WHEEL , ITEM# 235528, MODEL# 4031399LG	LOWES	3	$ 17.94
HARNESS	REDBARN ENTERPRISES	1	$ 125.00
2.5" High Profile Aluminum Push Pins	McMaster-Carr	3	$ 57.81
2"x3"x6" Multipurpose Aluminum (Alloy 6061) Block	McMaster-Carr	1	$ 29.41
.5"x12"x12" Multipurpose Aluminum (Alloy 6061) Thick Sheet	McMaster-Carr	1	$ 40.21
2" OD 7/8" ID (Double Sealed) Steel Ball Bearing	McMaster-Carr	1	$ 16.44
1 3/8" OD 7/8" ID Steel Thrust Ball Bearing	McMaster-Carr	1	$ 5.67
Steel Plate for Harness Attachment	eMachineShop.com	1	WAITING ON QUOTE
Grey Genuine Sheepskin Seat Belt Shoulder Pad Cover - Pair	Amazon	1	$ 24.93
		Total Cost:	$ 326.31