mike75925

well, i'm looking around, and seems like $200 will get my foot in the door. that's new and on ebay. what i'm wanting to know is: 1. are any of these hub motors dual acting (run and charge at the same time)? 2. if not, is there a hub dynamo/motor that will put out enough juice to keep the motor running up to 3/4 of it's max speed? i've seen some e-dirtbikes and such at the scrap yards, and i know some d.c. motors can be ran as generators. i've been riding bicycles most of my life, but now i live in the hill country, let me tell you, hills suck unless you are headed down one! anyway, i'm leaning toward geared (freewheel when not engaged), 24v500w, most likely thumb throttle (so i can keep my 15 gears). maybe this (perpetual charge) is attainable only with a trike (front wheel motor, rear wheels dynamoed)? thanks in advance

CigTech

ok 1st there is no Motor that can be both a drive motor and a generator. They just don't build them like that. 2nd If you put a 250watt non-geared motor on the generator wheel you would still not get enough power out of the generator motor to power the drive motor. To much loss in drag, load, hills, Wind and your weight. No free lunch here.

Now if you put a Gas generator of say 1000 watts at 110v AC. then you could power the hub motor and/or charge the battery. The weight and size of the AC generator will not fit a reg bike frame. But you could get around 180 miles per gallon if you could. One guy on here did just that on a powered 4 wheel bike/car thing.

turbo1889

Another post about making a perpetual motion e-bike machine. There should be a sticky in this section that explains 8th grade level physics for those who don't understand them.

On the other hand there is something on e-bikes known as "regenerative braking" that if you live in very hilly country and often have to use your brakes on the down-hill side to keep from going too fast and getting out of control could be useful. It is only available with direct drive hub motors or fixed chain drive motors where the motor is always spinning when the wheel is spinning and there is no freewheeling action. Due to efficiency and other losses you won't ever even get close to half of what it took to climb the hill back on the down-hill run using regenerative braking, but you will get something back and it will save wear and tear on your brakes. I personally prefer to use a mid-drive which does not have re-gen. braking capability but because of the better climbing efficiency I come out just as good or better.

mike75925

as to a generator motor combo, they do and have made them. well, not a generator, but an alternator i guess. some of the old generators and some of these pocket bikes (gas fired) have a combo starter (motor)/alternator. granted they do not work at the same time, but if you were to use 2 sets of coils instead of one, you just might get both at once out of the same unit. theoretically, if you can find out what trips the starter/alt between it's functions; say it is normally an alternator, but pushing the starter button makes it a motor, well you could hack the button and install the throttle. provided of course it would handle being used as a motor vs a starting motor. if dynamo A puts out x juice, how many dyanmoes will it take to make R the required juice? they could be arranged so that they look like a fender, or a planetary system. i also have heard of some circuitry that will boost power, it could be installed between the dynamo and battery bank. i don't recall if there are adverse effects with this simple power amp, but it may be worth a look.

mike75925

there is a small 2 stroke genny that does like 900w, it would fit on a rear rack or in a front basket . problem there is that we're dealing with dc, correct? how much loss will there be from an ac adpter?

CigTech

I went to Devry for electronics. There is only thing that you can not get around. You can't cheat the power man. Meaning that you can not get more watts out then you put in. you can change volts and amps, but watts will always be the same. For a example if you have a 12vdc inverter that puts out 30amps at 110vac you need to input 275amps 12vdc to get that 30maps 110vac out. 12vdc at 275 amps is 3300 watts. And 110vac at 30amps is 3300watts.

mike75925

cig, what happens when you step up the power being produced from a gene/dynamo, as in power transformers? i used to build the actual transformers, and i don't recall anyone talking about losses. on small scale production, any loss could be failure.

CigTech

1st volts = potential difference - or - potential work that can be done.
2nd Amps = the flow of charge per second through a simple circuit.
3rd watts = The work being done - or - power it takes for the work to be done.

ok now lets look at this. If you incress the volts the amps will decress for the same of power. Same goes for amps. If you incress the amps you will decress the voltage to get the same amps. step-up/down only incress or decress the Voltage or amps not the power. What you get out of a gene/dynamo (as far as watts go) is all you get. So if you have a 12v 2amp gene/dynamo all you can get from is 24 watts. Now if you step up the voltage to 48 volts than all you'll get 24 watts but now at .5 amps. There is no way to incress the watts at all. Thats why the electric company bills you in watts. Because there no way to cheat.