Blog 6 focuses on operating principles and chemical design.
Operating Principle and mechanism design
All devices have mechanical, electrical, chemical, and magnetism principles that work hand in hand. For example, distillation - principle: difference in relative volatility, LLE - principle: solute can distribute themselves in a ratio between 2 miscible solvents.
More examples:
1. steam trap - works on specific gravity
2. foil shavers - work on reciprocating motion
3. Airlift pump - the principle of buoyancy
4. brewing coffee - solubilities of coffee grounds (leaching)
Our chemical product: Heating Probe
Principle: Heat transfer, thermal conductivity
- thermodynamic law
- thermal conductivity of metal
- principles of heating
- mechanism of heating - how heating works
The heating probe generates heat. When it is submerged in water of a lower temperature, the water gains heat to equilibrium temperature with the probe. This is due to the first law of thermodynamics, heat travels from a region of higher temperature to lower temperature.
Mechanism helps to enable/enhance these principles. In order for the identified operating principle to work efficiently, mechanical movements are often required - moving a tea bag up and down helps tea leaves get absorbed by water faster/ fanning firewood to introduce oxygen for the firewood to burn faster. Mechanism can be explained as something that transforms forces and movements into a desired set of output forces and movements.
6 essential mechanisms:
1. Actuators - converts stored energy into motion
2. Cams - converts the rotation of the shaft into simple/reciprocating motion
3. Gears - transmit torque/ adjust rotational velocity
4. Lever - Transmit and amplify force by fixing the input and output about a fulcrum or pivot point
5. Ratchets - locks in one direction only (cable ties)
6. Springs - store/dissipate energy
Ping Pong Launcher
Practical 4
The objective of practical 4 is to utilize 1 kind of mechanism and create a toy that carries a marble and circulates/lasts for 30 seconds. Additionally, we have to use what we learned in practical 2, cardboard joinery to complete the marble run!
My group and I (Yeung Juen, Keith, and me 😀) decided to go with a rotating wheel carrying a marble through bridges that circulates back to the bottom of the wheel. Afterward, we will utilize a lever to make the wheel spin to carry the marble back to the start point, in which it will fall on the bridge and circulate again.
Parts of the design:
1. The bridges
To build the bridge, we used the cardboard at the back of a Foolscap pad. The cardboard joinery we used was slots and tabs. I learned this method of joinery through practical 2 where we were able to analyze how different cardboard fixtures were made.
2. Supports to hold the bridge
Supports are used to hold the bridges in place. To build the supports, we made use of flanges and L-braces for the cardboard joinery. The flanges were used to hold the support down, whereas L-braces were used to make the body of the supports.
(Our support, Rome could have learned)
3. The main body (aka the wheel)
The wheel was made with slots and tabs as well. It is then joined to the BIGGER support using fasteners.
(Our wheel, not on a bus though://)
4. The lever
The lever was unfortunately a fail. But it's okay! The lever was supposed to be attached to part of the wheel. and when moved up and down, it would cause the wheel to spin.
All in all, although it is unfortunate that we were unable to use our mechanism in our game, we managed to complete the design using cardboard joineries, under the time limit, and enabling the marble run to last more than 30 seconds. This practical has taught me a lot about the importance of teamwork and working together as a team to come up with solutions when a challenge is faced. It has really made us think critically and spontaneously on the spot which eventually made us complete the design. For example, we had trouble coming to a decision in making the support. We initially wanted to use slots and tabs, which did not work as well as we thought they would, and hence, we think back on what we have learned in practical 2 (and this can be done really easily with our previous blogs) in order to make the support strong and effective enough to hold our bridges as well as the marble.
I am also glad to be able to use and apply what I have learned in previous practical and the contents in class. The cardboard sheep that DR. Noel presented to the class were completely made of cardboard joineries only and I was able to use them in my design such as building the bridges. In addition to that, I was able to see all the other groups using different mechanisms for their marble run and it really deepens my understanding of how such mechanisms work hand in hand for a device to work. Being able to operate the different designs of my classmates also allowed me to critically analyze the working principle of different mechanisms
This also taught us how we can prepare earlier for mishaps like such. I believe that coming up with a game plan before this practical would have made us more prepared in facing failures like our failed mechanism. However, compared to the cardboard joinery practical, I personally felt that I have made an improvement in prepping for the execution of building the design.
Additionally, it has also shown me the importance and how prototyping would benefit us before manufacturing a device. In our practical, our mechanism was not able to work in place, if given more time, we could have amended the mistake and come up with a better solution. Similarly, for prototyping, a mistake can be made and overcome so as to enable the best design for the final product. This reduces the losses that could have been made (such as resources, materials, and cost) if the actual product was manufactured first.
This is our final design :)
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