Adapted tricycle S13
Contents |
Abstract
Adjust a tricycle for a 16 year old boy. He has a tricycle that he enjoys but has been unable to use is since he broke the cheap plastic brackets that hold his feet. He has significant power when his legs hypertonicity causes his leg extensors to lock straight. We will adapt the brackets to hold up to his powerful legs.
Team members
Dan Buker
Logan Atkins
Ian Woods
Jon Thompson
Introduction
The meeting with our client went very well on Friday. She met us in Cookeville Friday, January 25 with her son. She brought her son’s tricycle for us to examine. Our group took some time to ask her exactly what she wanted us to do, and if she wanted it done a specific way. This was also a good meeting for us because we got to take some pictures of the tricycle, and a few measurements. It was helpful for us to see what we had to work with, and some possible ways to approach the problem. We included some pictures of the tricycle that we took during our meeting in this summary. It was good to meet our client and her son and look forward to working on the tricycle with them.
Design Specifications
Our clients tricycle brackets need to be stronger to withstand the power of his strong legs. The straps for the pedals also need to be made of a stronger material. We have a few ideas under conceptual design.lt
1. aluminum leg brace
2. seat belt type straps
3. foot holder
4. handle bar foam
Conceptual Design
Describe potetial designs
Design Concept 1
Give a description of one concept with schematics, diagrams, etc
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Design Concept 2
Inspired from a water ski this design is intended to maximize comfortably and ease of use.
Design Concept 3
Detailed Design
This section will describe a detailed design process
Description of selected design
For our final design we took ideas from each conceptual design to maximize performance.
Detailed description of selected design
Our selected design was a combination of ideas from the conceptual designs. We used stress analysis to test what made our project fail. We also used mobility equation to determine degrees of freedom of our pedal. We cut down on the leg brace material to eliminate unwanted stress.We plan to use rapid prototyping machine to build our leg support, and make it more efficient. Including better straps to our final design will increase comfort and strength.
Analsyis
Describe three types of analysis to be performed on the design
Engineering analysis 1
% Degrees of Freedom
n = 3; % # of bodies
F_1 = 2; % # of lower pair joints
F_2 = 0; % # of higher pair joints
DOF = 3 * (n-1) - 2 * F_1 - F_2;
fprintf('The tricycle pedal has %d degrees of freedom.\n', DOF)
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>> run Analysis
The tricycle pedal has 2 degrees of freedom.
Engineering analysis 2
As shown in the model below the old Leg Pad failed due to the method of which the strap passed through it.
Our newly designed leg pad does not experience any of the stresses that cause the old pad to fail while maintaining the function and increasing comfort.
Engineering analysis 3
FEA was perormed on the tower to ensure it would stand up under normal use.
Also the decision was made to weld the aluminum together instead of bolting to increase strength. The strength gained allowed us to minimize weight without compromising functionality.
CAD Drawings
Bill of Materials
2" nylon strap (25 ft)-$0.87 per ft
1" nylon strap (25 ft)-$0.57 per ft
1" non sew buckles-$7.05
2" non sew buckles-$6.30
Rapid prototype (3-D Print)-$12.83 per part
Total - $75.01
Assembly Instructions
Step 1 - Disassembled the previous pedal configuration
Step 2 - Replaced all of the nylon webbing, buckles, and inserted 3-D printed part
Step 3 - Reassembled pedal configuration
Step 4 - Replaced foam padding on handlebars, and around brake handle
Fabrication Process
The Leg pad was 3D printed, you can download the files for free through the link below. There are two files available, a .SLDPRT which is the part format for solidworks and .stl which is a common file format for 3D printers. The site requires that you register to download but it is completely free and just takes a moment.
http://grabcad.com/library/adapted-tricycle-leg-pad/files/Adapted%20Tricycle%20Leg%20Brace
Completed design
Insert pictures of the final product
Summary and Conclusions
The goal of this project was to repair and improve the leg brace, and straps on the pedal assembly. We started out by making rough sketches of our design, and from there improving on the design by drawing it on solid works. We performed some analysis to ensure that our part would be better than the previous part. Once finishing the design portion, we started the fabrication of the plastic leg support. We had the Stem Center at Tennessee Technological University fabricate the leg support on there rapid prototype machine. The assemply was the next part in this process which is specified above in the assembly instructions. Overall it was a good project, and will improve the tricycle's performance for our client.
