The Journey
Prequel (Fusion 360 and 3D printing class):
Before we started embarking on our M&T journey, the kind professors held a workshop to teach us how to use Fusion 360 and operate the 3D printers available at the M&T lab. This workshop was of great importance as all of our designs would be done on fusion and we heavily used the 3D printers. We used the printers so much that we were once even questioned by the TA to justify our purpose for a 90 hour print.
Chapter 1 (Ideation):
Now equipped with the designing skills required to take on M&T, we as a group start thinking about what we intend to do. As it is with all ideation stages, we started off with just throwing random ideas around but one thing remained consistent which was that we wanted to focus on everyday household appliances. We quickly knew that just throwing random ideas would not work and we started looking through past year ideas and unfinished/incomplete past year projects for inspiration or continuation. Through this, we wondered on how we could maybe take our appliance and make it more sustainable. We decided that each group member would come up with one idea each and research on it before we compare them and choose the best possible one. The best possible idea did not just mean in terms of scale but also included feasibility and other factors. Through discussing with Prof Hanyang, we decided to go with making a water heater. We decided on the water heater because of the importance of boiled water in our everyday life and how often we need it in any situation we might find ourselves in even in the outdoors. Thinking about outdoors, one point immediately stood out to us: The fact that there is no electric plugs or any form of “permanent” electricity there! Reducing the reliance of electricity is a very important area of sustainability, and through our ideation process we came up with our end goal, which was to create a water heater that did not rely on electricity to heat water. Now that we had our idea, the only problem left was – How do we make it?
Chapter 2 (The Science):
We needed to figure out how to heat water without electricity. This really puzzled us as we did not know anyway this would be possible, so we looked went through what we were taught in physics and searched online for inspiration. This was how we were reminded by the concept of induction which was the use of magnets to generate heat through eddy currents. However, standard induction uses electricity to run. We knew that induction was the best way forward, but now we just had to modify it to work without the use of electricity.
Chapter 3 (Prototyping and Testing):
Eager to start dismantling and creating stuff, we decide to observe and dismantle a real induction cooker. Our insights from testing were that the important expect was the change in polarity which was what induced the current. We decide to prototype a design where we would spin magnets installed on a circular base side by side and of opposing polarity below a conducting surface. Through our calculations, we derived that a maximum temperature of 113℃ can be achieved from our intended setup. This would be a derivative of the induction system that would use lesser electricity as now we only needed to spin a disk instead of powering the entire device. With hopes and dreams, we started on our prototype.
Fig: Initial Prototype
The setup consists of:
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- An assembly comprising of 8 N52-rated magnets with alternating polarities is attached to a motor with a rating of 4000 RPM (revolutions per minute).
- A plastic cup with the base cut out is glued to the bottom of the aluminium plate and is held in place above the magnet assembly by 0.5cm
Achievement: We reached 50℃ at the span of 2 minutes, with increments of temperature of 20℃. (Note: Only 3.384 W was used!!!, using values obtained from the multimeter (0.282A) and the voltage supplied (12V))
Note: We kept the sizes of the items as similar in size as we could especially the conductive pad for easier calculation comparisons. The calculations were extremely difficult especially regarding how we would require to take the potential of N52 magnets using Gauss-Orsted units and convert them to potential max charge, relate it back to kinetic energy of aluminium atoms to find the temperature gain. We had to use some concepts from Quantum Mechanics which added a layer of “maximum possible” and “probability” which made the calculation extremely tedious and confusing so we tried to keep as many variables the same as possible for more reliable calculations.
So we still had to use electricity to spin the magnet however compared to the 2000-5000W used by a standard electric cooker, we had struck a gold mine. But the goal was still left unaccomplished. We created more and more prototypes to give us better understandings on how different factors such as arrangement of the plate relative to the magnet, height gap between the base and aluminium pad ,spin rate of the magnets, distance between the magnets, size of base or pad, etc. We made multiple prototypes on the fly reusing the parts we had. One example is these two prototypes:
Prototype A:
Result: Reached 50 ℃ using 3W in 8 minutes
Prototype B:
Result: Reached 50 ℃ using 3W in 7 minutes
In this comparison we were testing the impact of height gap between magnet base and conductive pad to see how this affected the eddy current induced. During the experimentation of the prototypes, it was noticed that the plate sorts of resist the movement of motor, thus the motor moves slower as compared to the original setup.
This resulted in the heating up process being longer. Thus, the original setup where the plate was placed at the side was chosen for the actual product.
Chapter 4 (Eliminating Electricity):
So through our various prototypes and insights gained, we are able to see that rotating the magnet at about 4000 RPM allows for efficient heating even compared to industrial induction heaters. The question lied on how to power the spin in a way alternative to electricity. The answer was Handcranks! Through our research and looking at past year projects we got the idea to use handcranks to then take the motion generated by the rotation movement of the hand to spin the magnet base. As excited as we were, there was a issue. We needed a RPM of 4000 while a standard healthy human would only reasonably be able to generate a RPM of 60 (one rotation a second). The question was how would we scale up from only having a available input of 60 RPM to having the output of 4000 RPM. Luckily the answer was soon discovered, it was with the use of a gear train.
Chapter 5 (Gear Trains):
A gear train is a system of gears used to transmit rotational motion and torque between different parts of a machine. The primary purpose of a gear train is to change the speed, direction, or torque of the mechanical energy being transferred. In simpler terms, it allows one gear to turn another, with each gear having a specific function depending on its size and the number of teeth it has.
Calculating our Gear Ratio and what gears we needed was relatively simple:
Fig: Gear Train Ratios
We can see we require a gear ratio of 72 and the gear train we need to make our product reasonably realistic and theoretically work. Having our specifications, we went to buy our gears and assemble our gear train and in essence our Handcrank Water-Heater. We bought our gears from the same shop to ensure that all teeths between gears have the same pitch and are meshed perfectly. While this has limited the size and number of teeths the gears could have, in hindsight this was the right choice as we would start combining metal and plastic gears together in our design. We then started designing and making our final design, which we incorporated in a temperature sensor that is programmed using an Arduino to detect the temperature of the water as it heated and display it . The Temperature Sensor had its own considerations and difficulties we faced as presented on our slides, but lets first move on with the gear train. There were two types of gears used being spur and bevel gears in our gear train. This is how our initial attempts looked like:
Fig: Initial Attempt of Final Design
Some limitations are immediately faced:
1) Gear Slippage – caused when gears don’t engage properly or have too much backlash, losing grip and reducing power transfer. can result from worn teeth, misalignment, or poor lubrication. We solved this issue by modifying the gear by attaching a coupler (more points of contact to shaft), filing down shaft for better contact between set screw and shaft and with the use of Metal Gears to increase reliability.
2) 3D Printer Limitations – The parts we 3D print are not able to handle the force from the gear train and sustain itself:
Fig: Broken printed parts
We solved this issue by redesigning the product so that all our parts are modular and printing them with more percentage filling to enhance the durability of the part. This also allowed us to switch out a faulty part easily whenever necessary.
Chapter 6 (Finale):
With our continuous improvements and even a scare in the first presentation slot that made us have to extend to the next presentation day due to gear issues we were able to complete our product that is able to successfully heat water without any use of electricity:
Fig: Final Product
Our Achievements:
- Able to crank product for somewhat long periods of time
- Does not rely on electricity
- Heat up an average of 1°C every 30 seconds when in a room temperature
- Tapers off at 50°C unlike our prediction of 113°C
Overall, it is a pretty successful design despite its flaws such as only able to heat up the water to 50℃ which we discovered was due to the size of the pads later on. We are proud of our product and hope you had enjoyed reading our M&T Journey!