Create and Improve

The biggest mistake that I made in this design assessment was that I failed to record the making process, including all the prototypes and the final result. I will at least try my best to show by text how I made my final rubber band car.

After the first sketch, since our design doesn’t use much material and if there’s a problem, it’s easy to disassemble and remake it, I decided to make a prototype immediately.

I have made the exact same design as the first sketch and found some problems:

1.  The connection between the main body and the stick sustains the tension of the rubber band is quite weak. I had to use plenty of glue guns on it.
2. the main body itself was also very weak. It needs something to sustain it.
3. there were too many wheelspins, and the car didn’t move that much.

Then I improved this previous design by firmly fixing the stick with multiple using of glue guns, adding a support fixture, and adding friction to the wheel by adding rubber bands to the wheel after making the second sketch in the previous blog post.

Lastly, I moved on to considering the ratio between the rear and front wheels. Since this car is an RWD, to make the car more efficient, I had to make the rear wheel bigger. So I used a wheel in the design lab which was bigger than the bottle cap and was not too big(if the real wheel is too big it will rather decrease efficiency since it makes it harder to gain speed).

Develop&Plan

sketches

#1

I made sketches about each part and scales I will follow.

• uses used bottle caps for wheels
• it uses wooden sticks for the body and straws to let the wheel spin inside.

#2

After making a prototype with my first sketch, I found out the wheels have too little friction, and the body is unstable.

• wrapped rubberband to all the wheels to increase friction
• Add one more stick to the main body to increase stability and prevent it from breaking.

 

#3

after making more prototypes, I learned it works fine but is too slow and doesn’t go far.

• I decided to change the rear wheel into a bigger wheel from the school’s design area. (considering the ratio of wheels).

Making sure everything was ok, I moved on to Create&Improve.

Define& inquire

Request(task): Design and make a toy that converts energy.

Design and make a device that can be used to teach energy conversion.

Target audience: anyone who wants to look at energy transformations directly in an interesting way, but the main audience will mostly be high school students who have the ability to understand how energy transferring works.

Things that need to be considered(design problems):

1. It should ALWAYS BE SAFE. 

2. the process of transferring energy should be clear and easy to understand.

3. We’re making a ‘toy’; it should be entertaining.

Precedents	Explanation	Pros	Cons
https://www.youtube.com/watch?v=Jw9n_KbxvqA	this infinite marble loop rail converts the battery’s potential chemical energy to kinetic rotational motion, then convey the kinetic energy to the marble, which makes the rotational motion into linear motion and shoots the marble again to the top of the marble rail.	It looks cool, and the conversion can be easily seen.	It’s too hard to build; I need to 3d model and print everything or have an extremely precise model using math formulas that I don’t even know.
https://www.youtube.com/watch?v=8DgCcYbs9JQ	Rollercoaster converts position(potential) energy into kinetic energy, and it also uses the opposite.	A rollercoaster is a most commonly used example to show energy conversion. It shows both ways of transfer.	But it’s way too common.
https://www.youtube.com/watch?v=b7zWwo9dbiU	Mouse trap cars use the potential energy held in the spring in the mousetrap, transfer the energy into kinetic energy, and move the car.	It’s a really good way to visualize the conversion; It moves a very long distance if well-made.	We don’t have mousetraps or any alternatives for the parts. But since this was the most unique and relatively easy thing to make, We tried to find alternatives.
https://www.youtube.com/watch?v=WLu2Eols0BI	This rubber band car was the alternative we found. It uses the same function as the mousetrap car; potential to be kinetic, but it uses rubber bands instead of springs.	This should be the alternative that’s most close to a mousetrap car.	It became too easy and doesn’t look very good, but we don’t have enough classes.

Final Defining of the design(success criteria): A Rubber band car that has high efficiency, by using the information that was on precedent #3 about the ratio of the wheels.