After problems sourcing materials last week, we finally found the gears, motor and belt we need. Our team took a trip to Grainger in San Jose to buy the gears in person. After spending time comparing many different gears and constantly converting from millimeters to inches (and vice versa), we finally bought the following materials. 

Before diving into the teams progress for this week, we wanted to discuss our prototype plan. Our prototype is focused on achieving the following user requirements:

1. Low cost
2. Simple to assemble and repair
3. Can be used by an average human

Inspired by electrical tillers and other farm mechanisms, we settled on a simple motor belt system that turns an axel with blades attached on it. See similar designs here : https://www.johnnyseeds.com/tools-supplies/bed-preparation-tools/tilther/tilther-9286.html.

​Our design utilises a simple motor or a drill, which is easily available from most hardware shops. Our goal is to build a simply motor driven circuit that drives a small gear which then drives a larger gear through the belt. The larger gear drives the axel which has blades attached on it. The small gear drives the big gear results in a lower rotational speed of the axel but a larger torque. The larger torque is required to cut/break the sturdy cotton stalk. 

To build our first iteration of the prototype we acquired the following materials. 

After testing the motor, we realised the rotational speed of the axel is too slow. We iterated the prototype with an electrical screwdriver which delivered much better rpm. We had success with the rotation of the gear system! Here is what the rough prototype looks like:

Our next steps for this week are:

• 3D print axel and blades
• Attach axel- blade system to the larger gear 
• assess rotation of the axel-blade system 
• Laser cut wood to create a sturdier holder for the mechanism

Looking forward to sharing our finished rapid prototype in the next blog!

​- Boomitra team

During Week 3 the ESWxBoomitra team prioritized finalizing the prototype's sketches and design. After meeting at the Stanford Farm in Week 1 and looking further into potential designs throughout Week 2, our team has finally started moving forward with building a prototype of a portable shredder that can easily be handled by one adult and that will incorporate a simple, yet powerful motor. 

For the purposes of creating a functional prototype for the Week 5 presentation, we have decided that the initial prototype will mostly be built out of scrap cardboard and wood. As such, the motor that will be incorporated into the prototype will be significantly less powerful than the motor used in a finalized future design where the shredder will be made out of metal. Otherwise, the overall design of the prototype for this quarter should closely resemble the more robust designs that will be carried out for the shredder in the future. 

The ESWxBoomitra team has spent time working with the Stanford Farm and in the Product Realization Lab (PRL) the first two weeks of spring quarter. The team is working on two goals concurrently: 

1. Acquire cotton seeds and test the effect of stubble incorporation on the germination of cotton. To that end, the team has secured a planting bed at the O'Donohue Family Farm for testing. 

2. Complete a preliminary design sketch of the shredder using existing designs and models for shredders. On Tuesday 4/5/2022, the team met at the PRL to research existing designs and discuss the design process. The goal is to develop a prototype that, for the time being, is functional and able to "cut/ shred" simpler materials such as paper, grass, etc...  ​

Below are some of the designs  being considered and will be further explored moving forward.

The team spent time studying various blueprints to further understand the mechanisms driving blade design. The goal is to acquire ready made blades from manufacturers designed for tilling, for use in the prototyping phase:    

​The team plans to have a prioritized design sketch by the end of week 2, so that prototyping can begin promptly starting week 3. We are also excited to discuss our design with our community partner, Anirudh, who is a mechanical engineer himself and receive his feedback before prototyping. Planting will likely occur in week 3, after which the team will focus on developing and iterating the prototype in preparation for the week 5 showcase.