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Old 03-04-2012, 01:30 AM   #1
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electric generator from alternator and bike parts


I want to build a bike trailer with a flwheel and independent gearing that can be powered by 1-4 bikes, with rear-wheels removed, to spin an alternator and generate electricity for an outdoor bike-based movie showing. Anyone have any suggestions on how to make the flywheel itself? Something with a significant diameter.

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Old 03-04-2012, 01:34 AM   #2
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electric generator from alternator and bike parts


Like how do I find an alternator? Is it basically just attached to the fan belt, that thing other than the starter? I don't really need any special alternator do I, since it isn't going into an actual car?

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Old 03-04-2012, 07:05 AM   #3
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electric generator from alternator and bike parts


What voltage are you in need of?
What kind of projector are you going to use?
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Old 03-05-2012, 02:46 PM   #4
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electric generator from alternator and bike parts


I guess I need 12vac, if I want to electrify a typical automotive inverter for non-auto accessories, right? How hany different measurements do I need to track?
Most of the projecotors I've been looking at are 2-300watts. I want my generator to run the projector, a laptop, and a moderate sound system if it has four people pedaling.

I guess I could just install a couple alternators on the same drive train.
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Old 03-05-2012, 05:39 PM   #5
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electric generator from alternator and bike parts


Leave it as DC to avoid frequency problems.
A world class cyclist can put out 400w for 20 minutes, 400/3 watt-hours.

This is an ambitious project for a non-engineer.
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Old 03-09-2012, 02:23 PM   #6
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electric generator from alternator and bike parts


What do your mean 'leave it as DC'? It will be an alternating current when it comes from the alternator(s), then the current needs a rectifying bridge or an inverter before it's DC, right. What do you mean by 'frequency issues'?
What machine is that world-class cyclist using?
Do you think the world-class cyclist would be aided by the kinetic energy of four other cyclists contributing to the same flywheel drive shaft? I'll post my gearing schematic soon.

What about wrapping my own coils, then using a bunch of salvaged neodymium hard-drive magnets (in an even number) chemically bonded with precise spacing to a wooden flywheel as a low-rpm alternator. In the mean time though, I can use a salvaged alternator, or two or three, on the same bike part drive system, to produce certainly enough for the projector. The projectors I've been looking at seem to top out at about 250watts, so I figure if I can get 300 for that, then I just have to worry about the sound-system's requirements.
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Old 03-09-2012, 02:45 PM   #7
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electric generator from alternator and bike parts


The alternators will put out varying freqs. which makes sizing transformers for this application difficult.
If you leave it as DC the inverters will convert the energy to high freqs. which means smaller transformers which means more efficiency and less cost.

If 130 w-h for 1/3 hour is peak power/energy output for a short time, you can figure out the long term energy output per person from these numbers:

1 Calorie = 1.163 w-h
A "Calorie" is not a "calorie".

A 160 lb person may use 550 Calories while sleeping, so on a 2000 Cal/day diet this leaves 1450 Cals to do useful work.

The efficiency of the body of an untrained person in converting Calories/hr into watts may be 10%. This is a search I haven't done recently but exercise machine readouts will give you some clue.

Last edited by Yoyizit; 03-09-2012 at 02:47 PM.
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Old 04-13-2012, 09:11 PM   #8
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electric generator from alternator and bike parts


If you are looking to do this on a shoestring budget with "junk" parts, I would go the route of stuff freely avaliable. Automobile alternators can be found at junkyards for about $20 or so. I'd then go to a flea market or thrift store and buy some old bicycles, remove the rear tire, and put a belt drive around the rim and to the alternator.

Next, I would connect an automobile deep-cycle battery to the alternator (s) Automobile alternators have internal rectification and voltage regulation built into them, but Automobile alternators are designed to work with a buffer load on them that would be the battery. Most alternators also have an "exciter" connection where power is provided back from the electrical system (it also controls voltage regulation) The battery will also provide a "buffer" when you want to change bikers or something.

I take it you want to use ordinary video equipment IE a DVD player and an LCD projector. With this being the case, these devices run on AC power. For that, I would get a DC to AC power inverter and connect it up to the battery..I'd use like a 1KW or so. An LCD projector is probably going to use about 100 to 200 watts for a typical 2000 lumen model...that's about the power one fit teenager can put out on a bike, and thus keep the battery balanced out.
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Old 04-14-2012, 11:10 PM   #9
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electric generator from alternator and bike parts


Wonderful. Even better, my plan is to build a bike-trailer with the gearing from 9 bikes to be able to accept input from four different cyclists, run through two stages of gearing to a flywheel in the center of the trailer. I may use a ceiling fan motor with neodymium magnets installed into it, or I may build the flywheel into an alternator from scratch, wrapping my own coils for a higher max amperage.
I've been watching youtube videos:
http://www.youtube.com/watch?feature...&v=4LRfNMRGbh8
and (if these don't work, search youtube for 'muddymuddymuddmann')
http://www.youtube.com/watch?v=DACZP...f=list_related

I also found this page regarding alternator construction:
http://www.otherpower.com/pmg2.html

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