Electric bicycle ideas. thoughts and theories...

I started writing this in the "electric trike 130 mile range" thread, when I decided what I was saying was going well off topic. I thought maybe I should start a new thread that's actually on topic. Here's what I was saying...

Here's some more thoughts to chew on (continuing from the thread mentioned above):

Take two identical "permanent magnet" motors. Hook the wires from one motor to the other and vice-versa. Now rotate the shaft or gear on one motor by hand. What happens? The other motor will rotate (theoretically) the same number of turns that you spin the first one by hand, either in the same direction or the opposite direction, depending on if you cross the wires(blue to red, red to blue) or not (blue to blue, red to red).

Of course, that's with no load and assuming 100% efficiency. On those dinky little hobby/toy motors, you get an almost perfect 1 to 1 ratio. Spin one motor once, the other spins around once as well. I've not tried it with these "big" bicycle motors, but the principles are the same.

Needlessly put technically, if anyone wants to know: Move a coil through a magnetic field and it will force electrons (electricity) to flow. Flow that electricity through a stationary coil, it will create a magnetic field. If that magnetic field is in opposition to another magnetic field that's already present, the fields will exert against one another(try pushing the "north" side of two magnets together, they'll repel each other, right?). The magnetic field of the armature(the shaft) pushes against the magnetic field of the permanent magnet(in the motor's casing). Something has to give. The permanent magnet can't move(it's bolted down, hopefully), so the armature has no choice but to move instead...and your second motor starts spinning.

Not that you needed to know why, but there you have it. There is a point to this. No, really, there is!

Now, hook that first motor up to your pedals. And hook the second motor up to your rear wheel, and the wires from one motor to the other, of course. Now, when you pedal, the first motor spins, which makes the second motor spin, which in turn makes your rear wheel spin. Viola, you now have a bike that doesn't need to run a chain from the crank to the rear wheel. Technically.

In reality, the efficiency of the motors and everything would mean you'd be better off just running a chain from your crank to the rear wheel. You might be fine on a flat, smooth surface, once you got going, but taking off and hill climbing would most likely be an act of futility. You'd lose the benefit of the large amount of torque your legs/gravity/the crank can produce. Unless you have some damned impressive and efficient motors, anyway.

So what do we do? Lets say that all your not-so-hard pedaling amounts to creating 150 watts of usable electricity to drive the motor on the rear wheel. Well, we need, say, 350 watts just for take-off and hill climbing. Well, throw in some batteries! Now we have something to provide the additional 200 watts we need.

Now we're flying...as long as the batteries hold out. But hey...the batteries will last almost twice as long with you pedaling. Maybe longer, since you'd only be using the full 350 watts on hills and takeoff...you might only be pulling 100 watts from the batteries on level ground, the other 150 still coming from your easy - but consistent - pedaling. Lets go on a limb here and say that you've just gone and doubled the range that your batteries alone would have taken you, all for about the same amount of effort as it takes to walk.

Ok, ok. Taking off under nothing but electric power is very demanding on your drive motor, and it doesn't do a very good job of it. The same goes for if you grind to a halt on a steep hill, or have to do a hill take off. All your pedaling to rotate that first motor is going to do nothing but generate heat. Even with the batteries, if that hill is steeper than the drive motor can handle, you'd be out of luck. The motor isn't going to push your butt up that hill, and if you try it, you're gonna burn something out.

Now what? Well, it's a bike. You have an immense amount of (slow-turning) torque at your crank. And wait a minute, the crank is already lined up and even has a big sprocket on it to put a chain between it and the rear wheel. And you were smart enough not to hook your drive motor up to that free-wheeling sprocket on your rear hub, you hooked it up directly to the other side of the wheel. Good thing that, because you need to run a chain from your crank to that freewheel hub. Now you can pedal slow and hard to get yourself up those stupidly steep hills, and on take off, so you don't prematurely burn out your drive motor. That's great!

Wait a minute...what about the crank turning the first motor to make the 150 watts?
Well, you left that hooked together, right? You can still crank the pedals to turn the motor to make the 150 watts.

But now the crank is hooked to the rear wheel as well!
Well, that won't stop you from generating that 150 watts, as soon as you get your pedals cranking up to that almost lazy speed you need to generate it, about 5 seconds after take-off, thanks to the 350 watt motor pulling another 200 watts from your batteries to propel you along.

But the crank is still connected to the rear wheel! I won't be able to pedal lazily anymore! It'll be pushing the wheel the whole time, defeating the purpose!
No, it won't. That's why you hooked the crank to a freewheel hub. As soon as the rear wheel is spinning faster than you are pedaling, the chain between the crank and the rear wheel might as well not be there. You can pedal freely to your hearts content, making that 150 watts without also having to drive the rear wheel at the same time. The drive motor and the batteries(and the 150 watts you're generating) will keep it spinning faster than your pedaling will. And the freewheel will stop the crank from breaking your leg when you try and top pedaling. Nice safety feature.

But what if the batteries die! I'll never make it home!
Didn't we start this experiment without any batteries? Pay attention. You can still generate 150 watts to turn that motor, and you can pedal it like any other bike. If you're feeling energetic, you can even use that 150 watts to recharge the batteries instead of pushing the motor. You've been eating too much McDonalds anyway, you could use the exercise. And before you say that the single-speed hub is much too slow to get around with: the drive motor will act as a second speed. In theory, if you are on level ground or goign down hill and it starts taking you less than 150 for the drive motor to maintain your speed, you will start to accelerate. You start pedaling like a madman and generate 350 watts, and the drive motor will behave as if the batteries were still fully charged.
Besides, even if both motors and the batteries all melt into nothingness, you can still pedal yourself home like the rest of the cycling world.

Umm...umm...umm. Aha! If I hook the first/pedal-motor up to the other motor at the same time as I hook the batteries up to the drive-motor, it'll make my crank spin! Ha! You think you're so smart...I'd be forced to pedal it faster than the batteries are turning it to make any power.
You're starting to annoy me with all these questions, kid. One fat diode will stop electricity from flowing the wrong way into your pedal-motor, so your crank isn't going to spin and make you get any exercise you might need. You'll have to decide that for yourself.

But I don't want ot always have to pedal.
Grrr! That's why you have batteries and a drive motor! You'll simply not have as much range as you would if you were pedaling as well.

Um...err...the crank isn't spinning fast enough to make anywhere near 150 watts on the pedal motor. Don't glare at me like that, mister!
Gear it up then, you annoying brat! Make the motor spin ten times faster than your pedals are turning. Make it spin a hundred times faster! I don't care! Get out of here! I've had enough of your constant questions! It'll work! Go away!

Aiee! *Runs away*


...


I've got to stop talking to myself. Especially on a forum.

Haha, I didn't mean posting on here was like chatting to myself, Deacon. I meant the way I was asking questions and answering them myself in my initial post in this thread was like having a conversation with myself. That's why I started putting the questions in italics, so it looked like someone else was asking the questions. That would be my dry/ironic/sarcastic sense of humor coming out.

And yes, you would need a diode to isolate the pedal motor...without it, it's a motor, not a generator. The nice thing about having a two motor (well, a generator and a motor) would be the ease of pedaling. You could provide as much or as little extra energy as you want. I suppose you'd call this setup a pedal-assisted electric bicycle, rather than the other way around.

Most of us can't pedal 200 rpm, nor can we crank full torque at slow speeds for long, but we can certainly maintain a "walk" level of output (60-120) rpm at low resistance, and we can probably maintain it for extensive periods of time. I know I can, at any rate, and I'm not in great shape. It's hills and maintaining a high speed that will wear me out in no time.

I figure 150 watts is a realistic, maybe even conservative number for what we could generate at a maintainable pace, but with all the transmission losses and such, I don't want to be over-confident. The average human can put out about half a horse power - at most - worth of mechanical power. It takes a high class athlete to put out (and maintain) somewhere around 3/4 of a horsepower. Anyway, 350 watts is close enough to half a horsepower (745 watts to a horsepower) and a bit under half of that seems like a reasonable amount for a typical Sunday afternoon amount of effort as pedaling to me, hence my 150 watt estimate.

Anyway, here's a continuation of that last example...lets throw in another free-wheel hub, this time in-between the generator-motor and the pedal crank. This will be an aid in getting the right gearing to make the generator-motor put out what we want, but more importantly, we can now spin the generator-motor faster than the pedals are turning, if we want to.

And that's where you introduce a gas engine into the mix. Hook the drive output of the gas engine on the same side of your jack shaft that the generator-motor is on, and make sure it uses a centrifugal clutch, so it is "Freewheels" when the engine is off but you are pedaling, and viola. Now you have a gas and pedal powered generator. It can be flying at 7000 rpm all day and cranking out more than the 350 watts needed to run the drive-motor on the rear wheel. Now your batteries are charging off the same power source that is powering your rear wheel. Shut off the engine when you're charged up and resume silently cruising off battery/pedal power. You'd probably have twice the gas mileage you would if you moved the bike directly off the engine, since it would be off half of the time.

Talk about hybrid.

There are other configurations, like having the gas engine push the bike and using the drive-motor as a second generator...the only benefit I see to that is that you'd still be able to pedal at a leisurely pace and adding your 150 watts to charge the batteries faster, rather than making your pedaling pointless (you'd not be able to catch up to the speed the engine would be spinning the generator-motor in the previous configuration, so pedaling becomes moot).

Lots of ways of doing it, depending entirely on the builder's preference. Me, I don't have a second motor to do it, so I would - no, will- end up using the drive motor as the only generator. This is both simpler and lighter, though it means pedalling would be useless except on take-off or as a last resort to get me home.

PS: You don't have to have the pedal-motor/generator match the drive motor, by any means. As long as it can generate at least equalt voltage, you're good to go. Use a little 250 watt motor, if that's what you have, at the same voltage, or put a higher-voltage motor on there so it starts outputting at a much lower speed, or get rid of it and put an alternator on instead...it's all good.

PPS: If you have the original configuration (no second jackshaft, no gas engine), you can set up the "generator motor" to assist in your pedaling on those steep hills or on take-off with just a switch. It would be geared very low, and you'd have to keep your pedal speed up to match, but it would be capable of carrying you up the steepest of hills or take all strain off the main drive-motor on takeoff.

Pops;

I'm right down town. That's the main reason I am interested in electric powered bikes. If I lived anywhere but in the city, I would probably stick to gas power and just pedal my butt though any real urban areas. That doesn't make it legal, but it at least makes it unlikely to be caught. I've seen and known many people who do it. I even saw a guy on a go-ped down town a coupel of weeks ago, and he doesn't even have the excuse of pedals!

Again, that doesn't make it legal, but that's what the electric is for. I have a true electric bike, and it can get me anywhere within town, it can even get me out to Langford and back. That doesn't lessen my interest in such a project.

Yes, we're limited to 500 watts...not that anyone but you will know if its 500 or 1000, unless you go blasting past a cop at 50km/hr. But besides that, you can have over 500w if you don't mind registering it as a "limited-speed motorcycle", riding on the roads in traffic and having a license plate...though good luck getting a bicycle to pass any kind of safety inspection they might have.

If keeping truly legal is/becomes my goal, I'd go for the original idea of having a pedal-powered generator to extend my range. A 500 watt motor to push me, a 250 or so as a generator...I can't see anyone complaining about that. There's no gas engine involved anywhere. And if they do decide it's a problem...have two 250 watt motors or a 150 and a 350, so your total is 500 watts between them.

For me, I want a long range electric bike, but I'm not going to get caught 30 km out of town with only pedal power to get me back...not when the bike weighs an extra 60lbs with batteries. I'll hide a tiny gas engine on it somewhere that no one will see, just in case. and chances are, it'll only get used in an emergency. With a choice of being on the wrong side of the law or having to pedal all the way home, I know my choice!

My electric bike is made by Luyuan. There's a couple of places in town that used to sell them, but I'm not sure if any do anymore...I know the scooter shop near here doesn't stock them anymore. Anyway, if that's no help, its one of those that looks like a lot like a gas scooter, just a bit smaller with pedals. 48 volt/350 watt. I think it's great...until I hit a hill or the batteries start getting low.

Seeing as my wife has taken to riding it too, and the little one (That's her sitting on it in my avatar), I've long since decided not to make a project out of it. I'm working on something else instead, rather than fix something that isn't broken.

If you take the engine off a moped and put pedals on it, does that make it a bicycle?

If you then motorize it, is it a moped again, or a motorized bicycle?

You're saying that this:

without an engine, etc, could in no way be considered a bicycle?

And yet this is most certainly a bicycle...


I don't see much difference, except for the heavy-duty frame/wheels/brakes. I would want them to be heavy-duty, if it was motorized, or if it was carrying 50lbs of batteries.

And yes, if you put the same engine back on, I would call it a moped again; I wouldn't put the engine back on, I would want to put an electric bicycle motor on it instead. I would call what all of the motorized bicycles on this forum are to be mopeds. Of course, I go by the real definition of moped, not what a lot of people call mopeds.
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mo⋅ped /ˈmoʊˌpɛd/
–noun
a motorized bicycle that has pedals in addition to a low-powered gasoline engine designed for low-speed operation.
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...a motorized bicycle. In other words, it's a bicycle...with an engine. A lot of people like to call my Honda Passport a moped.

I certainly do not. It has no pedals. You have to shift gears. It's not even a scooter, but technically a step-through motorcycle.

Anyway, if a moped is a motorized bicycle by definition, then a motor-less moped is a bicycle, also by definition.

On a similar but other topic...I was going to write a post of a theory on how to make a 2-speed (or more) automatic transmission, using two centrifugal clutches, with first gear also on some kind of freewheel (one-way roller clutch bearing) and the clutch springs for second gear being set to engage at, say, two or three times the rpm of first gear. And I was wondering why no one was using it already in their engines/transmissions/builds.

Well, I found out someone has been all along. The Tomos Mopeds(some have pedals, so I'll let it slide!) with their two-speed transmissions use this very method.

Tomos engines are interesting. It's nice to see something mass-produced that doesn't function the same as every other scooter on the market. For example, most engines out there have a small sprocket on the engine, going to a large on the rear wheel, the opposite way a bicycle does. Not a Tomos...they have a large sprocket on the engine, and small on the wheel, just what you want on a moped (in my opinion).

I'd like them even more if the pedal-start could be set up as pedal or start, and if they would also get rid of the two-stroke engine in favor of a 4-stroke, I'd love 'em.

Having owned an old, temperamental 2-stroke motorcycle, I am not a fan of 2-stroke engines. They have their places, like on light-weight power equipment, but in general they're hard to start, run hot, are noisy, burn oil, waste excessive fuel, have a narrow power band...all the very things that would tell you a 4-stroke isn't running right!

I bought one of those motorized bicycle engine kits a few years ago, and it certainly fell in with those same complaints. I sold it two weeks later. And have since sold the motorcycle, too. No, not for me...then again, comparing a 4-stroke to an electric motor, the electric motor wins out. No noise, little to no heat, no gas, no "starting" required...I'm looking forward to the day when high energy density batteries become affordable. Shouldn't take too many more years.

Edit: I think I got off topic!