Now that all of that is done I've gone back to what I love best which is tinkering with things. My latest project will be a stationary bike that runs a generator and produces electricity. After doing some research it seems as if all I have to do is run a chain from my rear bike sprocket to a gear on a DC motor to produce electricity.

My original idea was to use a car alternator but after doing some reaserch I realized that this would not work. Why then do they use alternators in cars rather than using DC motors to charge the battery?

Anyone have any idea in hell how big a DC engine a human powered bike can turn? I plan on hooking it up to a Mountain bike transmission (gears) so that you will be able to shift to produce more RPM.
Do you think a 1 or 2 HP DC engine is too large or too small?

I'm picking up parts here and there off Ebay. I'm trying to keep the price under $400.00

My goal is not just to produce electricity but to produce as much is humanly possible with pedal power.

Once I get the basic bike and motor set up I plan on adding a charge conroller, a few 12V batteries and a 1500 Watt power invertor so you can plug household appliances into it.

the reason alternators are used rather than generator units

-alts use slip rings rather than individul segments for the rotor. Slip rings wear less and reqire far less maintenance. (no shorted segemnts)

-alts produce a higer output at lower rpms.

-i forget the rest

Go down to the wrecking yards and rip off the generator and regualtor for the VW beetles. Most had generators and will do what you are thinking about.

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As for the power output, it depends on the time scale. I think a rather strong, fit individual might be able to produce around half a kilowatt for up to about 30-60 minutes. I know I've been able to make up to 1500 watts for a few minutes. I could probably do more (maybe over 2000) but I was already maxing out the resistance on the bike I was riding. And if I trained at it for a few months, I might be able to hold that rate longer, although it might be a high enough exertion that heart and arterial wall thickening could be a risk. I doubt most people would be able to do it. Most of the fitness-oriented people I know have a lot trouble getting past a kilowatt for more than a few strokes. At the other extreme, it would not surprise me if someone like Lance Armstrong is able to push out 1.5-2 kilowatts for sustained intervals of time and burst of up to maybe 4 or 5.

If it's just to power a TV or a computer, I'm sure an average-sized person at a good fitness level should be able to sustain it. That would be around 200-300 watts, I think, which isn't a particualarly high or low resistance level on the bikes I've ridden.

[ 01-12-2005: Message edited by: WillyTrombone ]

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There is also the "mass" issue...generators are much heavier.

Just to add what was already said...and I came home today and the house was 2degrees C. So glad I came home today instead of tomorrow from the gfs house or I would have had ice/water everywhere. Thermal ignition element was blown

j/k

The generator came first, way before the alternator.

It puts out AC but converts it to DC for practical purposes as does an alternator.

The problem with the generator is that in order for it to charge a battery (like in a car or tractor) it has to be spinning pretty fast at all times.

It needs speed to put out its maximum output so if the vehicle idles it does not charge the battery sufficiently.

So they invented the alternator which of course is much more advanced and charge the battery at very low rpm like at idle. Plus they support much higher output demands.

There are many reasons they are better which were natural design progression. In a generator the winding spins, where in an alternator the heavy windings are fixed so it can spin much faster, especially at idle.

The windings use a phase shift method in the magnetic field, which boosts the output power even more.

So why wouldn’t hubba-bubba want to use an alternator to charge and assault his batteries?

Oh and congrads 2X!

[ 01-12-2005: Message edited by: Cacophonous ]

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I don't know how efficient this bike I tried is, but I wouldn't want to power a modern workstation on that bike. Laptop, sure. TV, no idea.

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quote:

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Originally posted by FS:
Wow, I can't believe I'm agreeing with FS on this one

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