Week 13

 Week 12 {15.7.2021}

Hello! 👋Today we're back to talk about what we learned this week. This week is mainly about operating principles and mechanisms design. 

Operating principles are basically the science🔍 behind how different things work. For example, the operating principle behind distillation is the difference in relative volatilities. ♨️The different boiling points allow for the separation of the mixture which are then collected as the top and bottom products. Also, we also learned that there can be multiple operating principles behind one chemical device depending on what and how complex the chemical device is.

Activity 1📑-Operating principles behind our ideas

For the first activity, we are supposed to apply what we have just learned and think about the operating principle behind each of our own chemical devices. For our group, our chemical device is a coffee machine. There are hence, 3 main operating principles that we have come up with. 

1. Leaching
2. Heat transfer ( conduction, convection, radiation)
3. Buoyancy

For leaching, this refers to how coffee is made in the coffee machine. The water would act as a solvent for the extraction of coffee solubles(caffeine) in solid coffee grounds. The coffee solubles which are soluble in water, dissolve into the water forming the coffee☕️ that we all know.

As for heat transfer, it is the operating principle behind the operation of the coffee machine itself. Coffee is usually made with hot water unless we are talking about cold brew, for which the coffee grounds are steeped in cold water for anywhere between 12~16 hours for extraction. Anyway, the leaching rate generally increases with temperature, and there are optimal temperature ranges of the hot water to produce a good cup of coffee. The coffee machine will usually heat up the room temperature water💧 as desired before contacting it with the coffee grounds. Hence, conduction and convection to transfer heat to the water are involved. Since the temperature of the whole process is <2000C , radiation is insignificant.

Finally, we also have buoyancy 🛶as an operating principle for the transportation of water in the coffee machine. Since there are no pumps in the coffee machine, increased buoyancy of the heated water due to decreased density will act as a pump to drive the water up the coffee machine to where the coffee grounds are held.

Moving on we talked about Mechanism🦾. Mechanism is the enabler and enhancer of the operating principles. In order for the identified principle above to work efficiently, it usually requires mechanical movement. For example, in chemistry🧪, the mechanism is the chemical process itself. While in engineering, a mechanism is something that transforms forces and movement into a desired set of output forces and movement.

There are six essential mechanisms in functional prototyping and they are...

1. Actuators
2. Cams
3. Gears
4. Lever
5. Ratchets
6. springs

Actuators help to convert stored energy into motion. The stored energy usually comes in 3 forms: compressed air, liquid pressure, electrical potential. While the actuators come in 3 principle types: electric, pneumatic and hydraulic.

Cam help to convert the rotation of a shaft into simple or complex reciprocating linear motion. They can be sliding or rotational pieces in a mechanical linkage.

Gears help to transmit torque which is a force that tends to cause rotation and to hence adjust rotational velocity. There are many different types of gears: spurs, helical, worm, planetary and bevel gears, and etc

Levers help to transmit and amplify force by fixing the input and output about a fulcrum or pivot point⚖️

Ratchets lock in one direction, allowing them to tighten without fear of literally "going backward." An example would be cable ties.]

Springs store and dissipate energy. There are many types of spring: compression, extension torsion, plate, constant force and etc.

Activity 2📑-Mechanism of the toy

Moving on to the second activity, now that we learned about the different types of mechanisms. Our groups were each given a different toy. We are to play with the toy and then identify the different types of mechanisms present in the toy that allows it to operate the way it does. 

Figure 1: Backview of the toy.                        Figure 2: Sideview of the toy.

This is the toy our group had. Originally, we had no idea what the toy was supposed to be and how it is supposed to be played with. Then we noticed that there were ratchets, gears, and lever present on the toy. 

When we rotated the handle which is a type of lever seen on the side view of the toy in Figure 2, the gears on the toy moved. The gears can be seen on the back view of the toy in figure 1. This leads to the clicking noise by the ratchet and after a few "clicks", the stored energy is converted into the motion of the 5 sticks on the side of the barrel. This then makes us think that the toy is supposed to mimic a drum.

Activity 3📑- Ping Pong ball Launcher!

Next, we were tasked with the final activity of the day, to design a ping pong ball launcher.🏓💨

Figure 3: Lecture slides week 13.

We discussed as a group and eventually came up with this design...

Figure 4: Sketching of the Ping Pong ball Launcher.

Basically, as the labeled sketch suggest, the rubber band will act as an extension spring. When released by the paper clip it will launch the ping pong ball in the kitchen roll barrel, forward. The rubber band caught on the toilet roll barrel can then be replaced and the stored ping pong ball will also move downwards to reload the launcher!😀 Do you think this is a good idea?

Till next time!👋