The Chomper

Wednesday 2/27/2013
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Created the "Chomper" today after finishing our racing car.

Instructions from: 

http://www.picocricket.com/motion.html

Before.

After. Chomp chomp!

Racing Car: Older Design

This was one of our older design (in fact the design before our final one). The body was wider, so the car used longer axles. However, this was not an effective design because when the weight was placed onto the car, the weight pushed down on the axles, bending them. This made the car very slow or even prevented the wheels from turning entirely.

From this design, we were able to figure out our mistakes/misunderstandings of concepts. We learned from them and created a car that crossed the finish line in about 5.6 seconds!

This car moved more slowly. Its average time was about 9 seconds. (Our final design really improved!)

Older design.

Our old gear mechanism. Not much has changed, except for the fact that we placed the elastic pulley system on the other side of the blue Lego piece. 

This design was not very effective. (It took about 8-9 seconds to cross the finish line.)

Racing Car: Final Design Video

We ran 2-3 tests, and each time, our time was about 5-6 seconds. Our actual race time was 5.6 seconds (but we only had one run).

Racing Car: Day 2

Day 2
February 22, 2013
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On Friday, we continued to experiment with different Lego pieces, and we developed several conclusions:

-Using four wheels would be better than using three because it was difficult to balance the heavy weight using only three wheels.
-The location of the weight was important. We tried placing it in the front, middle, and back and decided the ideal position was in the middle. This prevented the weight from applying so much pressure on the wheels.
-We tried to build a sturdy base/frame of the car, but it was also important to make it fairly light.
-We had to consider the strength of the axle. In the early stages, we had used a rod connector to connect the rods for the axle, but this type of axle was not ideal. When we placed the weight, these axles were bent, preventing the wheels from turning. Therefore, we made the width of the body smaller, enabling us to use shorter rods. This way, the axle was less bent.

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We modified our design (sometimes just parts and other times the entire design) several times, with us learning from our mistakes each time.

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Our latest design used the "ganging together" method for the gear system. We used two 1:3 gear mechanisms and achieved a 1:9 overall gear ratio.

Wednesday (2/27/2013)

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Using this gear mechanism and 8-cm wheels and adjusting the car body (light design and sturdy axles) helped our car cross the finish line in 5.6 seconds (2nd place)! The car was able to go further in one revolution due to these changes. 

Our final design.

A better view of our gear mechanism. A 1:3 gear system and a 1:3 elastic pulley system. Overall, a 1:9 gear ratio.

Car with the weight. Notice the placement of the weight (not above the wheels). 

Racing Car: Early Model

This was our first fully built model. The car moved fast without the weight, but with the weight, it couldn't move. We realized we had to fix the gear system (add more gears for more torque).

Racing Car Early Design Video (Elastic Pulley System)

Our early design. Worked fine without the weight.

But couldn't work (turn the wheels) with the weight so we added more gears to later models to add more torque.

Closer Look at the 1:3 Elastic Pulley System

Project #3: Racing Car Day 1

Day 1
February 20, 2013
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Challenge: "In a group with two or three members, design a vehicle with a single motor, powered by a PicoCricket, that can carry a 1.0 kg weight as fast as possible on a 3 meter course. You should use one of the old gray rectangular motors that does not have internal gearing. This will force you to experiment with building your own gear trains. This is a non-trivial challenge that will require many design iterations on your part. You will have today, Friday, and next Wednesday to work on this challenge. There will first be a test run in which you will pit your vehicle against others on the 3 meter course. On the following day final competitive event will be held. You should document each iteration of your design in your design blog."

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Today, my partner Dana and I used our class time to brainstorm and to experiment with different Lego pieces. We tried building different parts (the main body, wheel and axle system, and gear system) separately and selected what we thought were the best choices.
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Things to consider:

-car should be as light as possible 

-traction (wheels)

-old motor

-how and where we place the weight (sideways)

-use least number of gears (each time, can lose a bit of energy due to friction) 

*But, we realized that having more gears can provide more torque.

-simple yet effective design

Played around with parts 

-Looked at motors and PicoCrickets.

-Worked with different Lego pieces.

Ideas while playing with Lego pieces:

-Motor can power one set of wheels (versus all 2 sets)
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After our initial brainstorming session, we read the Powerpoint on gears provided by Professor Banzaert. We learned the importance of gears and their ratios. For our design, we decided to go from a smaller gear to a larger gear to add more torque. (We tried a gear ratio of 1:3:2, but we realized we had to think more about the gear ratio and avoid randomly trying out ideas.) At one point, we tried to use a crown gear (this gear was placed perpendicularly to the gear attached to the motor and the gear on the axle turning the wheel). However, we realized it was difficult to properly align the gears, and this system failed with the weight.

Dana and I decided not to use the Pugh chart for this project because we did not know enough about gear systems to compare. Instead, we experimented with different systems and determined what we thought were the best designs/systems. (More on this later.)

Slotted Connecting Rod Mechanism

There are many different ways to convert rotational motion to linear or linear-like motion.

A Diagram of the Slotted Connecting Rod mechanism (drawn by me using Paint)

I personally found the slotted connecting rod mechanism fascinating and most interesting because I saw a lot of potential from this mechanism. As the disk (in blue) spins, the small disk inside the slot (green) moves in an almost linear motion across the length of the slot, and as this happens, there is a brief pause in the motion of the arm (in gray). 

According to the website (http://kmoddl.library.cornell.edu/model.php?m=443&movie=show), this mechanism was used for brick production because the brief pause allowed the workers to place the brick mold and to take the finished brick from the machine.

I think this mechanism could be used to make more complex systems where there are multiple functions to be done or performed in a sequence or pattern. The brief pause would allow time for another function. For example, maybe one could create a mechanic model of a snail that uses this slotted connecting rod mechanism to move slowly, but when the system reaches the pause, there could be another mechanism that makes the snail raise its head or project its eyestalks.

Project #2: Well Windlass

Challenge: build a model of a windlass for a well.

-Well is 12 cm in diameter (12 cm gap between two tables) so device must span more than 12 cm.

-Available material: Delrin sheets and rod, 120 cm of string

-Device should be strong enough to withstand weight of bucket (a full 1 liter bottle of soda).

-The top 10 cm of the bottle should be lifted above the plane of the tables.

-Limited to 500 cm^2 of delrin sheet (1/8" or 3/16") and 50 cm of Delrin rod.

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My partner, Julia, and I had to brainstorm separately due to the snowstorm, but interestingly, our designs/sketches were a bit similar.

Julia's Sketches

My Sketches

We didn't have a formal Pugh chart, but we did compare different parts and determined the better alternative. We agreed that using 3 rods for our spool was better than using 1 rod because a single rod was too weak. We also agreed on having supports for the sides (rectangular sides) to make sure our device would be strong enough to lift the bottle of soda. Lastly, we decided to prioritize functionality (versus appearance).  

After brainstorming and deciding on a combination of various designs, we created a model of our well windlass using foam boards. We were satisfied with the model, so we began sketching on Solidworks.

One big challenge (and lesson learned from my first project) was determining the sizes of openings and holes.  We realized that the laser cutter cut a bit more than the dimensions on Solidworks, so we created several notches and pegs tests to determine what was tight-fit, loose-fit, and "middle-fit". Using the caliper, we decided the holes should be about 0.02-0.03 cm smaller on Solidworks (The laser cutter always cut more than what was shown on Solidworks). 

One new part of this project was creating an assembly on Solidworks. After we finished our sketches of all the parts, we created an assembly drawing using mates. Julia and I first had trouble mating all the necessary parts, but when we tried to do them slowly step-by-step, all the mates worked. 

Our Assembly Drawing on Solidworks

After we had the parts using the laser cutter, we assembled them using the drill press, hammer, and metal file.   We used 1/16" piano wires to make sure the device was sturdy and strong. We used the hammer to pound the short pieces of piano wires into the holes created by the drill press. The metal file was used to make the holes (for the Delrin rods) bigger because the holes were too small (we could have made them bigger on Solidworks). 

Parts labeled with tape (tape also used to cover sharp piano wires that we tried to file)

Julia using the hammer

Our Well Windlass

This project took a lot of time and effort, but seeing our well windlass work was exciting and rewarding!

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Update:
We figured out that our simple design used about 382.72 cm^3 of Delrin. Our design was simple and probably not the most visually appealing, but it used less than 500 cm^3 of Delrin, and it worked!

Random Idea (Final Project Idea?)

I just had a random idea I might use for my final project (although I do not know the guidelines yet).

I sleep on the top bunk, so it is really inconvenient for me to climb down, grab a pencil and a notepad, my iPhone, water bottle, or whatever I need, and then climb back up. So, it would be really interesting and awesome if I could have a system where I could send a container device from my bed to my desk (ski lift system-like) and have a robotic arm attached to my desk (I would have the remote) that could grab the object I want. Then, the arm would drop the object into the container, and I can bring the device back to my bed. 

Problems:

-This seems complicated. My remote would have to be able to control the container device (send it to my desk and bring it back) and the robotic arm that would grab the objects (this would need some special grip). 

-My roommate. (I'm not sure if she'll be okay with this idea.)

This could just be me being really lazy.

Mini Workshops: Fastening and Attaching

Wednesday February 6, 2013
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Challenge: Learn how to join and connect various pieces of Delrin. Connect two pieces of sheet Delrin using heat-staking, piano wire, and notches/pegs.  Also explore the implications of loose fits vs. tight fits and bushings on Delrin rod. You will rotate through stations in the classroom/lab to learn each part of the process.


Today, during class, we had four mini "workshops" where we learned different skills.

1) I had to connect two pieces of Delrin using heat-staking. My pieces moved around a little because there was a small gap between the two pieces (I should have pressed it down more).
2) My next task was to connect two pieces of Delrin by drilling a hole and putting a piano wire through the hole. I could have centered the hole better. Also, the piano wire was bent, so I could not push it through all the way.

3) The third activity was to play around with different bushings and Delrin rods to develop a sense of what would be a loose fit versus what would be a tight fit.
4) We are not finished with sketching the 5 cm x 5 cm square (with different-sized openings) on Solidworks, but this activity is to show how 0.02 cm could make a difference (loose fit vs. tight fit). *Update: Our laser cutter had some problems, so we had to see our classmate Ashley's notches and pegs to gain a better idea of what was a good fit/tight fit/loose fit.


I made some mistakes, but they helped me gain a better understanding of how I should fasten/attach pieces of sheet Delrin. I am excited about using these new skills to design and to build my next project, a well windlass.

Reflection: Bottle Opener Project (Updated)

When Julie and I tested our bottle opener around 4-5 times, it worked but took a considerable amount of effort. If given more time, we would have improved our design by using 1 wider tooth (versus 3 smaller teeth) because the two teeth on the sides were not useful in the bottle opening process.

Also, we noted how our actual model was bigger than the model made of foam board. This meant that we had made a mistake on using the right dimensions on Solidworks. We had originally designed our bottle opener to be portable, but our actual model was too big to fit into a pocket.

Lastly, for my next project, I would like to be more "creative." I was satisfied with the bottle opener's performance, but the design was not very original.

Overall, I had a lot of fun and learned a lot about the engineering process and how much thought and patience were necessary to design and to create something.

Past Project on Solidworks (Bike)

I created this bike on Solidworks about 3 years ago.

It was my first project on Solidworks after working with ProDesktop for about 4 months.

This bike can turn in different directions, its wheels and pedals turn, and you can adjust the seat. (It still has many flaws though.)

Bottle Opener: Sketching and Building Process

Friday February 1, 2013
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Wednesday
On Wednesday, after Julie and I drew some sketches, we tried to make a model of our bottle opener using foam boards (to check for appropriate design and dimensions). Our first model had some problems (the opening of the bottle opener was too big), so our second model had a smaller opening.

Friday
We were satisfied with our second model, so we decided to use those dimensions. After completing our Solidworks tutorial, we drew our bottle opener on Solidworks. When we finished, we learned about operating the laser cutter and how to use it safely. It took about 3-4 minutes for our bottle opener to be cut (we chose the 3/16" thick Delrin board).

Our Sketch on the Foam Board (with dimensions)

1st model, 2nd model, and our actual bottle opener

Our Sketch on Solidworks

Our Sketch on Solidworks (after extruding)

Assignment#1: Bottle Opener

Wednesday January 30, 2013
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Challenge: In teams of 2, we have to design and build a bottle opener.
-Have to be made from a single piece of Delrin plastic sheet (either 1/8", 3/16" or 1/4" thick) using a laser cutter
-Could not be greater than 6" in any dimension (high cost of Delrin).

Our first assignment was to design and create a bottle opener. We (Julie and I) first had to brainstorm for some ideas. We first started drawing rough sketches (some looked ridiculous). Eventually, we decided to consider one part at a time (the head-part, the handle-part, and the teeth-part of a bottle opener). To make final decisions on the design, we created a Pugh chart to determine which design was the best. Our final decision was to make a rounded-shaped bottle opener with 3 teeth and a keychain hole. We didn't want our bottle opener to have sharp edges for better portability (to carry it easily in one's pocket). Our design was not the most original, but we tried to focus on the bottle opener's performance.

Brainstorming I (Random  sketches)

Brainstorming II (Thinking about one part at a time)

Pugh Chart