Design Goals -- Updated 09-13-07

Design Goals:
1-- Inexpensive. Recycled items where possible. Any purchase that must be made increases the likelihood it won't be completed.

2-- Electric-Assist: The motor isn't intended to do all the work, just enough of it to allow me to move more cargo and/or faster than I could by myself, and to have a longer range. It's Phoenix, Arizona--thus most of the time it's hot, and not much fun to bike 10+ miles to work, and having to essentially take a complete shower and change of clothes before I can start working, and again once I get home.

3-- K.I.S.S. It's already more complex than I'd like, but there are features I want that I can't get with the simpler ways I've thought of. Simple operation when completed is more important than simpler design/construction. However, the more complex the design, the less likely it is I'll finish it.

4-- "Automatic transmission": At some point, I want to have the whole motor assembly control itself to match the speed I set with the throttle in the most optimum way as possible. This is in direct violation of design goal #3, but unavoidable in order to get simpler actual operation, which is more important to the eventual goal of the whole thing.

5-- Weight/mass: Needs to be as light as possible, for all the obvious reasons. Batteries are probably going to be the heaviest add-on of all of this, with panniers second.

6-- Safety: Needs interlocks on the motor so it can't run:
a-- if the motor is too hot
b-- if my feet aren't pedalling
c-- if I'm not holding the throttle in position (needs spring return?)
d-- If I'm not on the bike
e-- if the batteries are too hot
f-- if ?? Need other possible failure modes that it should cut out on, and how to make it fail in a safe way.



These are new additions to this post on 9-13-07, after some discussions outside the blog that make it obvious that I haven't made my purposes and reasonings for this project clear enough.


7-- I won't use a kit.
a-- No challenge to me if I do so. Where's the fun in that? :-)
b-- Kits cost too much
c-- Many use inefficient hub motors
d-- Many hub motors in kits appear to be brushless and thus can't even use regen, AFAIK.
e-- I've not researched too many of the ones that use part of the pedal chain to transfer power, but they appear to have the problem that it's possible to get my feet knocked off the pedals by the motor if I am not careful to keep up with it, and that could cause an accident because I'll likely lose my balance, even if the motor includes a cut-off if it goes faster than I'm pedalling--it's too late once my feet are off the pedals. I'm not the most coordinated person in the world. :P
f-- A major goal is to use recycled parts wherever possible. Basically I'll take whatever I can find and make it work, if necessary. I'm a packrat and a pretty good scrounger. Plus I have all of you to help figure this out, right? ::crickets::


8-- Re: objections to using Electric power (vs gasoline, for instance) due to limited range vs heavy weight but cheaper batteries vs expensive lightweight batteries:
a-- Range is not as much of an issue as it might seem, because this is only an assist, and won't be running the whole bike, just adding power when I don't have enough of my own.
b-- It's a little bit of an issue, in that I do need to get at least 10 miles out of it, but once I get all the right parts in there, and learn how to shift for it, it should be efficient enough for at least that. If it's a workplace as my destination, I should be able to recharge there.
c-- Once I learn how to program and build the full version of the microcontroller for all this, it'll shift itself (motor only, not pedal drivetrain), and be even better, in theory (we'll have to wait and see on the practicality of that part).

Batteries and recharging are indeed a sticky point on this, and that will be the one thing that will cost. I have temporary testing solutions, but until I have a working design for the rest of it, the final choice of batteries will not be much of an issue. :-) I have some ideas about adapting various laptop and power tool batteries, potentially with adapters that allow usage of them in their original states, which includes their current, voltage, and thermal protections intact--if I can do this, then I can use old packs that might not give as much range as I'd get with new ones, but would be free to me as people often discard them when they replace them. I've collected many dozens of them over the years and reused the working cells in them to repair other packs for my own devices before. Most were still quite usable, just not necessarily for the device they came from. This is a topic I'll have to do practical research on after I have the rest of the design physically completed, and can actually test out theories on.


9-- Why Gas Won't Work:
a-- I can't stand the smell of it
b-- It costs too much
c-- it pollutes too much directly (yeah, I know, the technology that makes the batteries and other parts for my electric will also pollute, both during manufacturing and after the parts are used up and worn out and "discarded").
d-- I'm not convinced I can repair an ICE correctly, as I've never had much luck even with gas lawnmowers, while with electrical stuff I can even re-wind a motor if I have to (hate doing it, though), and I can design and build my own electronics, etc, where necessary.
e-- Gas and oil present spillage and fire hazards, as well, in case of an accident (yes, so do some battery solutions, especially Li-Ion and Li-Poly).
f-- Too noisy. I'd like a fairly quiet ride, when I just want to go and think on the way somewhere that I will need the assist to get to or from.
g-- ICE appear to be forbidden on some, perhaps all, bike trails and parks, etc, here in the Phoenix, AZ area (valley of the sun).
10-- Not sure of the DMV status exactly, but appears to require registration, licensing, insurance, etc once a vehicle uses an ICE. Don't want to deal with all that. Plus any emissions testing, if any.
11-- I also can't easily design starters and cutoffs and such for ICEs, whereas they're super easy for electrical stuff. Since I intend the entire system to only run when I am pedalling, and cut itself off entirely when I stop pedalling, mainly for safety reasons, then those starters and cutoffs are necessary.
12-- Since the only place I can keep the bike safely is in my livingroom, well, would you want to have that smell in your house, or stains on your carpet from it?


13-- Practicality of Electric-assist bike vs Car:
a-- Carrying power: almost every thing I need to carry, such as groceries, will easily fit on the bike.
b-- Range: Almost every place I need to go is easily within my pedal-only range.
c-- Time: Almost every place I need to go is *at least as fast* to get to on the bike as by car, and often enough is *faster* on a bike during heavy traffic times, even though I am obeying all traffic control points just like cars are, because there are alternate streets and routes that allow easier movement for bikes, without me disturbing the neighborhoods (which would happen if all those cars were driving thru them). For longer distances where freeways are involved, cars will win out time-wise, as well as when they use alternate routes with low or no traffic.
d-- Special arrangements are normally very easy to make for when a, b, or c make a bike impractical or impossible, but those are not usually necessary.
e-- For those who have suggested Motorcycle or a gas-powered bike instead of electric, I would still have to use special arrangements in case a-- was the issue, as the motorcycle or gas-powered bike wouldn't move the things that won't fit on the pedal bike, anyway. Range would be increased to as far as the tank would carry me plus any gas stations, but as per point 12 above there are many reasons gas itself is highly undesirable.


14-- Weight of Electric vs gas: Batteries are good enough even now for me not to have to have the weight of the rest of the system plus rider in batteries, just to get it moving. That's an improvement over when I very briefly considered this once before, about 11 or 12 years ago, I think--the batteries were what stopped me then, as the only alternatives I knew of were NiCad or LeadAcid, neither of which is all that light or energy-dense. Li-Ion came out, but then was so incredibly expensive (some ~1Ah laptop batteries were $350-$500 or more!) that I could not seriously consider even attempting it. But now, it's far far cheaper, and better technology. Good enough for what I want to do, even if not yet optimal. Since I am already needing the assist sometimes, I don't think my aging body will wait for the batteries to get better. :P