DEVELOPMENT & VALIDATION
PARAMETER ANALYSIS
Embedded Files
Below captures a summary table of our parameter analyes, including the key task parameters we needed to test, what options we were evaluating within each tests, the factors we were considering in our analyses, the types of models or experiements we used to test those parameters, and our intermediate decisions for the beta prototype based off of thoses test. Additional details on our decisions can be found below and further testing details can be found in the validation section.
MATERIAL SELECTION
On making the decision on material selection we used Ansys Granta to compare different materials for different parts of the mechanism.
Baseplate :
In consideration of the need to secure the helmet and to stand the extreme weather conditions we finalized aluminum as the material for the baseplate. It is not only sturdy but also lightweight and easily malleable to form a shape with no sharp edges. We also wanted to be sure about the material being sturdy enough to bear an impact - an accident. Other options were Steel, Carbon fiber and Plastic, while steel did provide the necessary strength but it was too bulky to be mounted on the bicycle and plastic and carbon fiber did not provide enough security. We also have an eco audit report from Ansys Granta to support our findings. We found that Al alloy had lower energy consumption and carbon footprint as compared to Mg Alloy.
Straps :
The straps at the top of the helmet are to protect the helmet from falling off and from getting stolen. Initially we started working with the metal wires as we wanted to use something sturdy and lightweight. Soon we realized they did not provide enough security because it was easy to shift them around. They had less surface area to hold the helmet firmly at a point and so we decided to move forward with the straps. These straps have more surface area to hold the helmet in place and are difficult to break through. Other options were fabric straps similar to the straps in the seat belt. Based on our analysis using Ansys Granta, steel straps were the most secure and durable against potential theft or damage versus alluminum or other alternatives.
STEEL STRAP
The straps at the top of the helmet are to protect the helmet from falling off and from getting stolen. Initially we started working with the metal wires as we wanted to use something sturdy and lightweight. Soon we realized they did not provide enough security because it was easy to shift them around. They had less surface area to hold the helmet firmly at a point and so we decided to move forward with the straps. These straps have more surface area to hold the helmet in place and are difficult to break through. Other options were fabric straps similar to the straps in the seat belt.
RUBBER COATING
CROSS FRAME
In consideration of the need to secure the helmet and to stand the extreme weather conditions we finalized aluminum as the material for the baseplate. It is not only sturdy but also lightweight and easily malleable to form a shape with no sharp edges. We also wanted to be sure about the material being sturdy enough to bear an impact - an accident. Other options were Steel, Carbon fiber and Plastic, while steel did provide the necessary strength but it was too bulky to be mounted on the bicycle and plastic and carbon fiber did not provide enough security. We also have an eco audit report from Ansys Granta to support our findings. We found that Al alloy had lower energy consumption and carbon footprint as compared to Mg Alloy.
cOMPONENT SELECTION
CONJOINT ANALYSIS
Based on the results of our conjoin analysis, we based some of our material and mechanical choices based on user preferences. For example, we observed that lock types were actually more important to users than price.
Locking :
We extracted data from the conjoint analysis to finalize on the lock. Users prefer a lock which is hassle free and does not require to be carried around, and therefore preferred combination locks over other alternatives. Other options were key lock, dial combination lock. In our manufacturing plan we propose a custom made combination lock which snaps at the junction where the straps meet the baseplate.
Fixture to the bike frame:
Many different options of fixtures were thought over to fix the mechanism on the bike frame. Our initial thoughts were to bolt it to the bike frame but then we did not wish to tamper with the bike frame. We want the user to have the flexibility to attach or detach the fixture as they need. So the next best options were C-clamps or pipe clamps. We tested both the clamps on a variety of bike frames and realized cushioned pipe clamps work the best. The rubber casing around the fixture adds necessary friction to hold the bicycle frame. It prevents the locking mechanism from rotating or moving in its place.
Wires versus belt loops:
Iterating from our original alpha prototype, our conjoint analysis revealed that adjustable clamps were the least desired amongst other options. This forced us to re-evaluate component options for securing the helmet in our beta prototype. While our conjoint analysis revealed a strong affinity for retractable wires as a solution, we recognize that many of our users were unfamiliar with belt loop solutions, which skewed initial results. Further feasibility testing proved that wires would only work if they were wide enough to have enough surface contact and traction with the helmet. This forced us to move forward with wide straps as a reconciliation between wires and belt loops while contrary to on conjoint results.
Form SELECTION
From Cross Shaped Frame to V-Shaped Frame:
In our initial analysis, our finite element analysis (seen in detail on our proof-of-concept page) demonstrated that our cross-shaped frame would provide the most stability for the bike helmet. This was the form we then chose for our beta prototype. However, after a thorough analysis on the form we realized V Shape is the best to keep the helmet stable at its position when the bicycle is in motion. The form also makes sure that it causes minimum obstruction to the rider. This form was used instead for our manufacturing plan and our final design recommendations.
Strap Formation:
Primarily the straps are strategically positioned to keep the helmet secure and lock it in position. We also tried to minimize the material so that there is less weight on the bike. Assuming high tautness of these straps, the experiments we ran observed that two straps that converged together on both ends and had enough contact surface would the helmet would optimize helmet stability. In our validation testing, we cover more details as to how strap length affects the reliability of certain strap formations and how our formation choices would have changed with the availability of more materials.
ECO AUDIT REPORT
We then ran an EcoAudit of the top two material sets that aced our selection criteria to assess their CO2 and energy footprint. We compared Cast Aluminum Alloy for the cross frame and Butyl rubber for the steel strap covering with Low carbon steel for strap.
CROSS FRAME REPORT
Report Price and Density for Aluminum.pdfSTEEL STRAP REPORT
steel strap.pdfReport abuse