Senior Design Notebook

Columbia Vector Technologies Senior Design Group 8

1

Index

Project selection, 1

Bicycle with a Continuously Variable Transmission, 5

Smart-scale Hydrogen Generator, 5

Smart Roof using PVDF, 6

Project selection decision, 7

Faculty feedback， 8

Faculty feedback response, 8

Literature review, 9

Patent, 9

Literature, 9

Internet, 9

2

3

4

Sep. 25th, 2018

Project selection

Proposal 1: Bicycle with a Continuously Variable Transmission

Pros: purely mechanical project, interesting and practical

Cons: slightly difficult to make, high rate of failure

Mission of the project: The goal of this project is to create a CVT to be retrofitted

onto a bicycle. Currently one bicycle CVT transmission exists but it isn’t largely

commercially available and is very heavy. We plan to effectively retrofit a bicycle with

our CVT hub and create an interface for the rider to see live updates about bicycle

status.

Proposal 2: Smart-scale Hydrogen Generator

Pros: If successful, will be a great way for energy conversion

Cons: potential safety hazards, not very related to mechanical engineering

Mission of the project: The proposed project is to create a small-scale hydrogen

generator, roughly one cubic foot in size. Motivation for this project lies within the fact

that electrolysis is a well understood phenomenon, however, is not often effectively

used within small scale devices which offers several distinct benefits. Some of these

5

benefits include portability, long term storage of energy, and the ability to store

energy which would otherwise be lost if not used ie. wind and solar.

Proposal 3: Smart Roof using PVDF (Polyvinylidene fluoride or polyvinylidene

difluoride)

Pros: easy to make. Some existing experience with the material

Cons: Project might be too easy.

Mission of the project: This project aims to create a porous-polymer based scalable

model for a smart roof that has tunable optical transmittance and can be used to

switch between opaque and transparent states. Unlike the traditional electrochromic

glass technology which is already commercially available, the smart roof we are

proposing does not need any energy input to remain at either of the two states.

We are not really seriously considering this project

6

Oct. 12th, 2018

Project Selection Decision

Based on the advice from many of the TAs and the professor, we have chosen to

pick the first project, designing a CVT for bicycles.

Some bottlenecks of the CVT project

1. The CVT design itself is quite a difficult problem. Cannot use current CVT

design on cars, since it has slipping and does not work well for applications

with high torque and low RPM. Also, the current CVT design is too bulky.

2. Other challenges that arise from the first bottleneck, that need to be

considered, are that of transmission size and placement. All of the outlined

design options above are relatively complex systems requiring various moving

parts which will require considerable space. A bicycle provides significant

packaging constraints due to being a very narrow two-wheeled vehicle that

needs to be maintained under a certain weight.

3. Picking a bike (?). Should not be that much of a trouble.

7

Oct, 23rd, 2018

Faculty feedback

Below are some feedbacks from faculty members in the department

Myers/Lipson: This is a fun project. I think it is challenging, but doable. Though I do

know that the CVT bandin the car requires an extremely difficult manufacturing

technique to pull out all of the ductility of the material.

We are probobaly not going to copy the CVT designs are cars. This may need some

creativity, however, we are trying to make a brand new CVT design

Stolfi:This was successfully attempted a long time ago. The difficulty was gear ratio

which was very low. If their CVT is just 2 cones with a belt between them, it is difficult

to get high gear ratios.Variation in cone diameter is limited if it has to fit in a bicycle

frame. For bicycles, high gear ratios are required. A novel design is required (which

may be possible).

This further makes us sure that we cannot use a traditional cone design for the bike

CVT.

8

Nov. 7th, 2018

Literature Search Results

Patent:

We can only find car CVT patents on the internet (Google Scholar). The CVT uses

traditional V pulleys. (No. 881925A)

Internet:

Nuvinci CVT, sun and planatary gears. More information at:

https://www.fallbrooktech.com/nuvinci-technology

https://www.youtube.com/watch?v=kN8CCY1vFC8

Scientific journal:

Rockwood, D., Parks, N.,Garmire, D. (2014). A continuously variable

transmis-sion for efficient urban transportation.Sustainable Materials and

Technologies, 1-2, 36-41.doi:10.1016/j.susmat.2014.10.002

Link: https://www.sciencedirect.com/science/article/pii/S2214993714000049

9

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