My dilemma of finding a suitable bike to use (on the cheap) has been found! Sadly, it comes at the cost of my dear roommate's bike's demise. Seems like it was backed into by a car while locked up on campus and the back wheel got decently smooshed. She hadn't really been using it and she graciously offered to donate it to my project.
He suggested that I look into local recycling plants that will often sell you buckets of batteries for cheap with the idea that some of them may work and others may not. This would be a great option over buying one huge battery for both saving money and gaining a better understanding of how batteries work. Of course, there's potentially more of a safety risk using questionable batteries, but I'll enlist the help of my more experienced EE friends to make sure I don't blow anything up. Since my battery needs depend on the motor, and the motor depends on the bike (for the most part), it appears that the next step is to find a motor. The convenient coincidence is that in my Systems Analysis and Circuits classes this semester, we've just begun to talk about DC motors. Based on the preliminary research I've done, I want to look a motor that I can incorporate a torque sensor into. A torque sensor would make the motor "smart", in the sense that it would give more juice when it senses the rider applying more torque (going faster or going up a hill). I do want this pedal assist feature above anything because I want to be as safe as possible while riding this bike. An electric bicycle with a motor that's just either "on" or "off" starts to stray into motorcycle territory to me, and that's really not what I want. I still want to use my bicycle as a source of exercise and not take away pedaling altogether. The website The New Wheel is proving to be an incredibly useful source. I'll be looking for second opinions but their comparisons of different e-bike motors will give me a good starting point. Some motors available like the models by Bionx and Bosch have torque sensors built in, but you need to shell out some extra cash for the fancy ones. Could I integrate a torque sensor of my own? How does a torque sensor send signals to the motor? I need to know much, much more before I narrow down my motor options. I'd like to DIY as much of this as possible so I'd prefer to make my own, but I'm concerned about feasibility. The question of hub motor vs drive train motor is still up in the air, but with a torque sensor being a priority, I can push off that choice until later. An aside:
I'm getting a bit ahead of myself here but I'm thinking about how I'll need to make this whole system waterproof. I want to design a case myself and 3D print it. The students I mentor in the freshman engineering class will be doing a project exactly like this in a few weeks (to house an arduino and breadboard), so the timing works out well. I want to make sure that the case can keep splashes out but not prevent an air intake for temperature control. I believe that I'll have to make sure the batteries and motor don't overheat, or melt the plastic of the case, but I really don't know at this point what kind of heat I'll be dealing with. It's amazing, the more I learn, the more I realize I don't know.
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