Overview

Design

Our design philosophy is simple: 

“Keep it simple and cheap by reusing used bicycle parts and other parts whenever feasible ”.

Good engineers design the simplest solution to the requirement that they can. They have a qualified mentor, Leonardo Da Vinci, who said something like “Simplicity is the ultimate form of sophistication.” He was right, of course. Any dufus can design something overly-complicated at greater initial and on-going cost than necessary. When you do that you are wasting the earth’s valuable resources and people’s time and money for little or no return or payback. 

Following this philosophy our designs try to use the MKS (meters, kilograms, seconds) or metric system of units, which, I am certain most of you will agree, is far more elegant and simple than the FPS (feet, pounds, seconds) system. FPS is still used by the US and our problem in Canada is the influence of our southern neighbour in the construction materials and components (eg. nuts, bolts) industries. As such we have used the FPS system in the 2D and 3D CAD designs.  I will investigate automatic conversion from FPS to MKS units. Where conversion introduces abnormal risk, I have provided secondary MKS equivalencies. The American reluctance to convert to MKS continues to be a monument to stupidity which continues to affect their biggest trade partner,  Canada.

We also like to keep things inexpensive and encourage use/reuse of commonly available components within the constraints of the requirements. Each vehicle base design is typically made with  3 used bicycles, a few sheets of plywood, one 2x4, and scrap metal for steering gear. However there are some components like the motor, battery, controller, freewheels and parts of options that are probably purchased new. Investigate the cost of these first when making a budget. If your wife is like mine, she doesn’t like budget surprises.

Guidance

Detailed, step-by-step construction information accompanies each design and option. Our designs are meant to be altered/adapted to your requirements. There’s that word again. Your requirements list for an e-vehicle is where you start: at a table with pencil and paper, not in a garage or workshop. Make a list of your requirements and include your constraints too. 

Classify the requirements into MUSTs and WANTs. Rate the WANTS into high, medium, low categories. This is document 1: Requirements. The MUSTs are your baseline for comparing designs. Pay special attention to the usage requirements such as range (distance travelled between chargings) as they determine the cost of the most expensive variable – the battery size. MUSTs make choosing a design easy because they are a simple yes or no comparison list – does the product have this feature or not? MUSTs get rid of a lot of ambiguity, sales hype and feature “noise”. 

Now compare the features of each surviving design (and options) to your list of WANT requirements. Which design scores the highest? Document these decisions and choose a base design. Then make a list of the changes (additions or subtractions) that will be required to the chosen design, This is the 2nd document – the To Be Built design. 

From this list, make a cost estimate, rough construction plan, and initial budget (document 3 – Project Plan). Negotiate with your “significant others” on the 3 documents and agree on a result. If you fail to plan, you are planning to fail. If you have a family, “doing it yourself” never seems to apply to the planning stage. That would be way too risky. 

Of course, revise the plan and budget as you proceed. The rule of thumb for estimating the duration of engineering projects is to take your most pessimistic estimate and multiply by 3. Nothing with real value is created without problems to be overcome and risk. The best you can do is to minimize it. Even though we have made our designs as simple as feasible, building an e-vehicle is a significant project. Do your research and start slowly. Successful DIY (do it yourself) projects require thought, common sense, discipline, patience and, most of all, perseverance. And lots of book, article and Youtube learning time! 

Favour experiments with the components you have rather than just theory and calculations. A great example is determining how many batteries you will need for your vehicle. By collecting voltage and amperage data under various motor loads on a benchtop using a few batteries, graphing that data, and extrapolating the real need is a better model of reality (and way less risk) than just theoretical calculations. Of course, to have these experimental and theoretical approaches corroborate each other reduces your risk a lot. We describe this and other processes in detail. 

Don’t be afraid to learn new skills, but practice before you apply a new skill to your expensive materials. We won’t wish you luck because that is a rare commodity in engineering and construction. So don’t rely on it – “do your homework” and don’t cut corners without experience.

Cost

To save you time determining if this project is even financially feasible for you, let’s deal with this topic right now as best we can. Obviously the costs will vary greatly depending on location – assess as best you can. These costs DO NOT include common power or hand tools whose costs can vary greatly and are known as indirect costs.

By the way, you can build this vehicle without power tools. We did not assume you have electric power available. And, if you install the solar panel roof, you can charge the batteries without grid power. If you do not have welding skills (or access to a welder to develop those skills) you will likely need to use a welder’s services. As the wife reminds me, that is a more cost-efficient approach than buying a welder for a single project. She is right, of course - dammit! Then again your decision would depend on the cost of a welder, access to grid power for it, etc.

The direct costs of the older base V3 Scottmobile in Edmonton, Alberta, Canada was about $CDN1300 +/- 30% at time of building (1Q 2022). Based on V2,3 costs, the estimated cost of the V4 Scottmobile as pictured at bottom of Home screen above is (in $CDN): 

•  48V Li-ion battery pack (~$400 new), 

• 2000W, 48V, 42A BLDC motor + controller (~$175 new)

• twist throttle/voltmeter (~$30 new)

• 3 used bicycles (~ $120 used)

• plywood 3/4" x 4' x 8'(~ $180 new),

• scrap metal, fasteners (~$50 used)

•  welding services (~$100)

• miscellaneous (screws, bolts, nuts, hinges...) (~$200). 

Total ~$1300CDN

By the way, do not assume these materials will be cheaper in Canada. For example I received a quote from a New Delhi, India plywood manufacturer for waterproof, marine grade plywood (much better quality than needed, but NOT delivered) for $50CDN/sheet of 18mm/.71″ x 2440mm/8′ x 1220mm/4′. This item would be about $220CDN in Canada.

Again, this is the base V4, the base electric vehicle pictured with pedals, but no options. The most expensive component and variable to any e-vehicle is currently the battery. The more range you need, the more you use the motor, the more expensive it will be. Cost this component carefully. The vehicle was designed for a mixed usage mode between pedalling and motor use - usually pedalling to start. A mix of the 2 gives you the best overall benefit. The younger and healthier you are, the more pedalling you can provide, the less battery you may need. The older you are, perhaps the more battery you can afford. 

Some other costs you should be aware of will complete the TCO (Total Cost of Ownership) amount.  As any truthful and informed automotive engineer will tell you, the operating and maintenance cost of an EV is far less than an ICE vehicle. Why? Again, it comes down to simplicity. 

Operating Costs

In the operating cost area, the biggest cost is fuel. To produce a litre of gasoline and deliver it to its end-consumer is vastly  more complicated than simply charging a battery by plugging it into an electric grid. And even simpler still is when you use a solar panel and charge the battery(ies) directly. 

Maintenance Costs

The typical modern ICE car drive train (engine, transmission) has about 1000 - 2000 moving parts. An equivalent EV has about 6. Which of these  would you guess has a lower maintenance cost?  An EV does not need oil or oil filter changes, clutches, automatic transmissions with fluid, mufflers, tail pipes... the list goes on and on. You often wonder why the world ever went/continues to go ICE. There are no more excuses!

Cost Summary

Because an EV is a  fundamentally simpler solution to the problem of transportation than an ICE vehicle,  the total cost of ownership is much less than an ICE vehicle. And, if the comparisons are fair, always will be. Why always?  The reason is because of physics, thermodynamics and entropy (a measure of disorder or chaos). The more complicated something is to begin with (in mechanics, the more moving parts it has), the more energy you need to maintain it in a steady state (or "working condition") so it does not degrade and fail. Of course, the energy you expend to maintain the system is either work or money (for someone else to do the work.)  

This is intuitive for maintenance, but also, of course, applies to the main cost of operating a vehicle: the fuel. Today's fuel production and distribution systems, besides their huge polluting problems, are,  in my view, incredibly complicated and, therefore, very prone to cost increases.  Capturing the energy of the sun and storing it in batteries is and will remain an elegant, simpler, lower cost alternative. At time of writing (4Q23) solar panels generate electricity at less than $0.02USD/KWh. One liter of gasoline generates 8.8 kWh, so if 1 liter gas costs ~$1.20CDN, $1.20/8.8 = ~$.13CDN or $.10USD/KWh  or about 5 times as expensive.