Putting it together
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:
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:
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 design of the shredder currently has three main elements: the handle frame, the box holding the motor system and covering the blades, and an axel with specialized blades within the box. Although we have determined that the handle frame and the box itself can be made out of the scrap cardboard we've acquired, it was necessary for the items for the motor system that will spin the blades to be purchased on Amazon. These items include: a 12V DC motor, 1.5V batteries, an aluminum belt pulley, and ball bearings. Since items for the motor system have yet to arrive from Amazon, we might have to adjust the dimensions of the box to properly fit all the parts.
In the upcoming weeks we expect to spend most of our time as a team in the product realization lab (PRL) putting together the prototype. With the Stanford Farm we have also clarified the organic cotton seeds that can be used in their growing beds; planting of the seeds to begin measuring germination rates is likely to commence at the beginning of Week 4.
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.