Monthly Archives: December 2018

Daisy Drive Capstone Project

Fig. 1 – Solar-powered tricycle, Daisy, at Burning Man

Introduction

The Capstone project is usually done during the final year of your engineering degree. Each department get projects provided by companies related to their areas of expertise. For UBC Mechanical Engineering, the projects range from fluid dynamic pipe flow testing, biomedical knee braces, to rovers that fix wind turbine blades.

All the potential projects are presented to you in the first week of September. Then you’re allowed to rank your choice of top five projects. I was matched with my second choice, eatART Daisy Drive project, along with three other Mechanical Engineering students. The eatART (energy awareness through art) foundation is a not-for-profit foundation composed of volunteers from the STEM and art fields. Our client is the Co-Executive Director who is also a mechanical engineer and UBC alumni. Our project is to optimize the design of the electrical belt drive of the largest solar-powered tricycle in the world, Daisy.

Built approximately 20 years ago by inventor Bob Schneeveis, Daisy traveled to Burning Man, an annual festival celebrating community and art and was used to drive passengers around using purely solar power. At its maximum capacity, Daisy can carry four adults in its carriage plus a driver in the front. It is steered by a hand crank and speed-controlled by a foot pedal throttle. Due to its size and weight, Daisy has only been able to travel on flat ground, such as the desert where Burning Man takes place. Now that Daisy is in the possession of the eatART foundation in Vancouver, our aim is to improve Daisy’s climbable incline so that it fits in with the hilly terrain of Vancouver.

First Term Steps to Capstone

1. Define value for stakeholders. Establish scope of your project.

Since our team is working for a not-for-profit organization, our project’s value is in the social-good generated rather than monetary value. With an optimized drive system, Daisy can be used in Whistler village, where roads are at a slight incline. Allowing Daisy to carry visitors in Whistler allows the eatART foundation actively showcases the accessibility of renewable energy technology such as solar power.

Initially, our client mentioned that the major design issue is in the V-belt that translates the motion of the rotating motor shaft to the three meter tall front wheel. When the V-belt slips from the sheave, this means that despite the motor still turning, the wheel stays stationary. This is particularly dangerous on an inclined road, since the front wheel will start to slip backwards without braking. Even with brakes applied, Daisy remains stuck on the inclined road, and cannot move forwards at all.

Another mechanical design flaw was in the belt tensioning mechanism. This mechanism provides tension in the V belt by pulling the two sheaves apart further. This is currently done by winding up a torsion screw attached to the motor and the front frame. This tensioning system doesn’t seem to be properly designed and may be experiencing induced strains and stresses. By redesigning the tensioning mechanism, we could eliminate these stresses and eccentricity, allowing the sheaves to be correctly positioned relative to each other.

To climb a hill, a certain torque is required. Imagine changing to a smaller gear on your bike while climbing a hill. You slow down significantly, but it becomes easier to pedal. A smaller gear ratio means that speed is traded off for torque. Similarly, the current motor and gear configuration could not provide sufficient torque to climb any incline because the gear ratio was too big.

Limitations also arise from the electrical system, as the batteries only provide 24 volts, the motor controller seemed to be old and out-of-date. The motor’s torque capability sets another limit. Its peak torque (stall-torque) and power could be simply insufficient to move the large tricycle.

To sum up all the aforementioned design flaws, they include:

V-belt slippage,
belt tensioning device,
low gear ratio,
and electrical power limit.

2. Investigate the problem. Define functions of your solution.

Since Daisy was quite old, the information on its components were not recorded well. Through testing and investigation, we collected data on the electrical motor, the motor controller, and the drive.

For instance, we tested the efficiency of the motor controller. Running the motor without the V belt attachment, we measured the input current from batteries to the controller, and the output current from controller to motor. Then, the power was calculated from the simple P=IV equation. The ratio of P_in / P_out represents the controller’s efficiency. Since Daisy has a throttle, we ran test trials by varying the power draw from motor, from 17% to 100% of power draw. The controller efficiency we calculated is represented in the graph below.

Fig. 2 – Controller efficiency as power draw from battery increases

Evidently, the controller efficiency was above 60% at all times. More importantly, the controller was operating at 100% efficiency near the max power draw from motor. We concluded that a replacement for the controller was not necessary.

3. Conceptualize different solutions.

After defining the functions required to perform by your solution, create various concepts through simple sketching. Aim for quantity instead of quality. You want as many concepts for each function as you can. These become your concept fragments; they are fitted together into whole concepts through mechanical mounts.

Fig. 3 – Concept sketches; (on left) treads with timing belt; (on right) pedal chain drive

After attaining several whole concepts, you should evaluate them on a impartial basis through winnowing, Pugh chart, and a weighted decision matrix. We evaluate our concepts based on a variety of performance metrics, one of which essential to any project is cost. Even though our team had lots of different concepts involving electrical components, they did not do very well in the cost criterion of the Weighted Decision Matrix. In the end, we ended with two concepts with good potential, the chain drive and added traction on wheels. The two-stage chain drive concept we came up with would eliminate slippage and increase the effective torque translated.

Fig. 4 – Two-stage chain drive concept sketch

As opposed to a single stage chain drive, two stage would allow a much greater gear ratio while staying within the recommended roller chain to sprocket contact.

4. Create a critical functional prototype (CFP).

The critical functional prototype (CFP) is designed around a selected function that’s critical to your solution. This is a great chance to see the physical (not theoretical) feasibility of your concept without investing resources into the whole concept. The CFP also allows you to detect unexpected failure modes, undesirable defects, and incalculable performance issues.

We needed to confirm that a chain drive can sufficiently translate motion from motor to the wheel, so we built a chain drive prototype consistent of a motor, a driving sprocket and a driven sprocket. The gear ratio (# teeth driving / # teeth driven) is 17:73 or approximately 1:4. We also set up the different transverse offset to see the upper limit at which the chain starts to derail, rendering the drive useless.

Fig. 5 – Chain drive critical functional prototype test rig

The motor was running at different speeds with light shocks applied. What we found was that for commercially made sprockets (with special profiled teeth), there was almost no derailment at any transverse offset or motor speed. However, for the water-jetted sprocket, there was almost always derailment. Upon closer inspection, the aluminum plate may also have deformed while in storage, so the sprocket it made was slightly bent, leading to the chain derailing.

5. Reiterate the design

After presenting to the client once more with our CFP experiment results, the chain drive concept was deemed too risky to implement. It would increase the number of mechanical components, and due to lack of slippage, could cause irreparable harm to the motor and electrical components if the drive gets jammed.

The concept we ended up with is increased traction (through additive materials and increase wheel width) and better tensioning of the driving pulley to eliminate V belt slippage.
Through preliminary calculations, we also discovered that the batteries shifted a lot of weight to the rear of the tricycle. On a hill, this would create a lifting effect on the front wheel. By shifting the position of the batteries closer to the front wheel, we could better distribute Daisy’s weight and give it more grip on the road.

We decided, along with the clients, that a prototype wheel should be built to test different traction materials such as truck bed liner, spray-on rubber, and etching notches into the flat bar metal. We will be building a section of the wheel out of steel flat bar, attached to an electric motor at the same torque and the power level as the one on Daisy. Then we can apply the various materials onto the section and run it on a ramp. If the section successfully climbs the ramp, then it proves that the material provides sufficient power. If the section slips, then there is not enough traction. Oppositely, if the section is stuck, then there is too much traction force.

That’s all for now. The design process will resume next semester with fabrication.

If you have any questions, please comment down below. I look forward to chatting with you.

Cheers,

Kirsten

Acing Finals – A Video Guide

Finals can be a stressful time of year. Now that I’m finishing up my 3rd year of Mechanical Engineering, I’ve personally had my fair share of those panicked last minute cram sessions (and have learned to avoid them at all costs).

If you’re interested in learning about how I personally get through finals nowadays, you’re in luck! The first ever Mech Ambassadors Vlog covers just that, check it out!

Music: Bensound – Hip Jazz

Busy As Usual – The Third Year Shuffle

Hello everyone,

I’m now back at UBC for the second term of my third year of Mechanical Engineering, which is on Term 1 of the winter session in the Co-op schedule. Trying to explain the Co-op schedule is always complicated, so I’ve just started saying I graduate on May 2020 (assuming everything goes as planned).

I ended up taking an online course over the summer and I strongly recommend it. It didn’t feel like an extra burden on top of Co-op work since it was only one course and now I only have to take five courses this term instead of the usual six.

And the best part?

Only one course starts at 8:00am. A dream come true.

Now, when I was first looking at this semester on paper it seemed like an easygoing semester. Only five courses? Sounds like smooth sailing to my final year. But engineering being engineering, this term is just as packed as all of my other ones. Here’s my quick student perspective off the courses this term.

MECH 325 – Mechanical Design 1

This course applies to all options of the Mechanical Engineering program (Thermofluids, Biomedical, Mechatronics, and General. More info on those here).

You learn all about gears, pulleys and all sort of mechanical systems. There’s tons of information and equations coming your way so get ready to soak in all types of variables. There’s group work involved with designing components and small mechanical systems, but not every week.

MECH 327 – Thermodynamics 2

Oh boy, here we go again. Thermodynamics 2: 2 Hot 2 Handle

Only students in the General and Thermofluids options of the program have to take this one. It’s one of the most important and applicable courses for the field I want to go into after graduation (energy). That first midterm didn’t go so well though, so this class has been my top priority.

The second midterm is two days from the time I write this, so wish me luck.

MECH 328 – Mechanical Engineering Design Project

This one applies to all options and it’s the main design course this term. The project this year is to design an autonomous ocean microplastic sampler.

Here’s a little information on microplastics and why they are increasingly a problem in the ocean: https://oceanservice.noaa.gov/facts/microplastics.html

The project is actually pretty neat, but it’s quite a bit of work. We don’t have to build anything, but we do have to develop our design using engineering design principles. This means that we have to be very thorough with our decision process and there’s tons of documentation is involved, so it’s good preparation for the engineering field.

MECH 386 – Industrial Fluid Mechanics

This course only applies to the Thermofluids option, so it is one of the more interesting courses for me. It’s essentially a continuation of previous fluid courses, but more grounded in industry applications. There’s a semester long project involved where you contact companies and try to solve problem they are having specific to fluid mechanics.

I did pretty well on the first midterm, so the course is currently on my good graces. The turbulent flow midterm is just around the corner, so I’m not sure that good grace will last.

PHIL 101 – Philosophy 101

This is my non-engineering course this term.

I highly recommend taking Philosophy. It’s a nice break from the regular engineering courses were we get smacked over the head with all of the rules that we have to follow. The physics and math with equation after equation after equation. I feel like this course provides a different perspective on things.

It’s nice to take a step back and go “Wait, do I even exist?” If I don’t exist neither does that grade I got on the Thermodynamics midterm. There’s comfort in that.

And that’s about it. Two design courses, two regular engineering courses, and one humanities for a total of five courses.

Like I said, it looks like a pretty straightforward semester. After this it’s an 8-month Co-op and then my final year. I just have to make it through this term first.

Denmark Study Abroad Experience

HEY readers! I missed you all. It’s been almost three months since I’ve come back from Denmark. There’s so much to cover. One of the topics in this blog are the Mechanical and Energy Engineering courses I took at Denmark Technical University (DTU). Furthermore, I will talk about the job market in Copenhagen. Of course, there are also the people I’ve met, whether professors, students, or industry professionals.

So firstly, the courses I took at DTU included some of the standard requirements for UBC Mechanical Engineering, such as Mechanical Vibrations and Manufacturing Technologies. These courses covered the standard content and material. Perhaps the only difference is that Mechanical Vibrations course did not have a laboratory portion at DTU. Instead, we had assignments in Matlab that simulated the displacement and velocity measurements we would get from real life vibrations. Manufacturing Technologies was a distance-learning course. It also had a more interesting content, covering metallurgy (the design and manufacturing of cast components), glass-making, and how to select the best processes for a desirable product function and performance. Both of these courses were considered to be Bachelor level at DTU. However, most of the technical electives I chose were at Master level.

Wind Turbine Racer

Trying to get a grasp around how wind power operates in Denmark, I selected technical electives tailored towards my goal. The Wind Turbine Racer course was one of the most interesting courses I’ve ever taken. It was the equivalent of a design team at UBC, but with the added support from a professor and an assistant professor and the resources provided by DTU. The class was very small, containing only 7 students. However, only 2 of them were Danish; other students in the course were from Columbia, US, and Spain. Just like most of my other courses, I was the only Canadian. In this course, we were trying to optimize a wind turbine racer that generated forward propulsion when wind speeds were high. It could drive up to 113.1% of the wind speed (which is between 6m/s and 10m/s or 22km/h and 30km/h). The turbines spun on a shaft connected to bevel gears and would in turn translate the rotational energy to the rear axle of the car. There are many potential areas for optimization. We learned that we can perhaps install a feedback loop that angles the turbine perpendicularly towards the direction of the wind. That was a major implementation. Smaller ways of improving the vehicle was to play with the curvature of the turbine shield, length of turbine blades, and the efficiency of the gear train.

Energy Systems Analysis and Optimization

Another course I took was very relevant to a potential career path. In Energy Systems Analysis and Optimization, we used thermoeconomic modelling to design cogeneration plants that were more efficient than conventional power plants. Approximately 11% of electricity and heat demands in today’s European society are met using cogeneration technology. In Denmark, electricity supply system operates at 65% efficiency overall [1]. This proved to give more than environment improvements, but it also has long term economic implications that electrical power corporations are interested in, especially when implemented at a regional or national level. We used Engineering Equation Solver (EES) to simulate the power and heat outputs of real life systems of heat exchangers, steam turbines, and boilers. Heat recovery steam generators (HRSG) are used to absorb the energy from hot exhaust gases released by gas turbines. Using thermoeconomic models, we designed HRSG for a real life gas turbine cycle. Overall, this course taught me how to design components of energy systems at a micro level. At a macro level, I needed to know how electricity generated was distributed in the Danish and Scandinavian power systems.

Power Systems Balancing with Large Scale Wind Power

Starting with basic concepts of different types of wind turbines, Power Systems Balancing course built up to the dynamic simulation models for power balance control. With large scale integration of fluctuating wind power into conventional power grid, the challenge arises concerning whether operation can be reliable [2]. When wind power decreases unexpectedly, an imbalance is created in the power system that could lead to power outages and dangerous shutdowns. To prevent this, conventional electricity generating units are necessary as backup that can respond quickly. By creating a feedback loop, measurements of wind power output is used to regulate amount of power produced from conventional power plants [2]. This sums up the technical electives I took at DTU.

Job Market in Copenhagen, Denmark

Two fields of engineering jobs stood out very clearly above others, pharmaceutical and information technology. Copenhagen, and Denmark at large, is home to some of the world’s leading pharmaceutical companies, such as Novo Nordisk. Surprisingly, Denmark is ranked one of the lowest users of pharmaceutical products among OECD countries [3]. The result is a huge export to other countries. The amount of pharmaceutical product exported has tripled within the last decade [3]. Even though this field is not blatantly related to Mechanical Engineering, there are opportunities in quality control and process validation. One of my friends in Industrial Engineering landed an internship with Novo Nordisk using his skills for industrial layout optimization.

The second most frequently posted jobs relate to information technology. This includes software development, data management, and network architecture. Companies like Cisco, Microsoft, and even non-software dominant companies like Siemens Gamesa Renewable Energy has many job postings within this field. How does that relate to mechanical engineering? Computer simulations like computational fluid dynamics, finite element analysis, and dynamic modelling are some key technical electives that the department provides. Outside of the courses, I’m learning Python and other software languages on my own, and will take exams to attain certificates. Evidently, the job market in Denmark isn’t tailored towards mechanical engineering. This challenge simply means we need to be flexible to changes in the society.

Life in Copenhagen

Copenhagen is a curious city. It has all the charms of Scandinavian architecture, with its green spiraling church tops and rustic brick exteriors. The infrastructure was an old legacy, but everything else was new. From trendy restaurants and cafes to the brand name clothing lines, the gleaming store fronts belie how crammed it is inside. Every nook and cranny of space was precious, as seen by the tiny washrooms that seem to be carved into the walls. As always with older infrastructures, retrofitting was not the only challenge. Reliability of electricity supply was also a question. Sometimes an intersection in the middle of the city would not light.

Despite its modernity, available products were not as abundant as in Vancouver. It took me a while to discover that underneath the veil was an undeniable better quality of life. The Danes might not show it in the fancy products they use, wear, and consume, but they show it in how much they enjoy what little they have. I discovered you can pick up anything in a store and it would be of great quality. For instance, a variety of the cheapest store brand food like oatmeal, vegetables, fruits were organic. Organic wasn’t just a healthier alternative, it was pretty much integrated in everyday life. Consuming these affordable organic food products actually made a difference in how my body feels. This led me to think that maybe it is exactly this brand-driven, commercialized mentality that’s hindering us to get money’s worth of quality in Vancouver.

Aside from commodities, the quality of life in Copenhagen was much better because of the social securities that Danish government provides. All of my Danish classmates received free university education. In addition, they were subsidized with monthly living allowances that they did not have to pay back. This enables such them to be financially stable and stress-free during their university years. Being a Canadian student, I could not enjoy the Danish financial benefits. However, I found a job and was able to take advantage of the high wages in Copenhagen. I also appreciate seeing this social system in action and the massive impact it has on the way of life.

I really enjoyed writing about my study abroad experience and hope you enjoyed reading it. If you have any questions, please comment down below. I look forward to chatting with you.

Kirsten