[Homestead] Shaking the grid
erthnsky at gmail.com
Sun Feb 21 01:58:35 EST 2010
Don Bowen wrote:
> There is no god add there is no free lunch.
And some people apparently can't accept their own beliefs, they just
need to keep repeating themselves, like saying a mantra for affirmation
in order to convince yourself. (I'm good enough, I'm smart enough, and
DogGoneIt, People Like Me!)
Everyone here knows how you believe, Don. We all accept that, and more
importantly, people respect your right to believe however you wish.
This is the second such comment in as many weeks, notably after someone
new surfaced. It seems like baiting to me, but perhaps it is just a
reaffirmation of your own beliefs?
I said I would like to see the group revived, not divided.
Anyway, on the post itself, all good points.
I want to interject an idea-it may not be worth a damn, but maybe it
will give someone an idea on how to make this idea work.
You were talking RPM's and gear ratios...I kept thinking about a cream
separator. We borrowed one that was hand crank, and the gearing was
such that that mother would hum after only a few revolutions. She may
not have to pedal at 50mph if something like that could work.
Oh well, I see that others have also mentioned gearing up...
As was pointed out you can
> generate a little power but it is very difficult to sustain. An
> automotive generator runs best around 4500 RPM. I Figure the surface
> speed of a 4 inch pulley at 4500 RPM and figure what a maintainable
> cadence is on the bike. Use that to work out the gear ratio and how big
> a wheel is needed to get that surface speed.
> Start with an alternator for a GM car from the 60s to 90s. These are
> one wire units and have V-belt pulleys. You may be able to use the
> wheel wothout a tire mounted to get the surface speed but you will have
> to use lower gears.
> Just some back of the envelope calculations when I am a bit tired from
> spending the afternoon climbing under the dash of my daughters car
> fixing the brake lights and turn signals.
> A 4" pulley has a circumference of about 12.56 inches. At 4500 RPM that
> works out at about 4710 Feet per minute or about 53 Miles per hour. I
> know that alternators produce current at much lower speeds but that is
> just an example. How long can you pedal at 50 mph?
> Now take another tack. A common GM one wire alternator size is 60 Amps,
> they are available up to 120 Amps. Newer Nippon Denso alternators like
> the one on my pickup are good for 170 Amps but I have a 60 GM somewhere
> around here. 60 Amps at 13.8 Volts is a bit over one hp ignoring
> inefficiencies. I do not have the figures handy but a male in average
> shape is only good for a sustained .2 hp or about 150 Watts. At 13.8
> Volts that is something like 11 Amps. I have a bunch of those small
> gell cell 12V 7 Ah batteries used in UPS. It would sustained pedaling
> about an hour to charge one of those batteries. A 7 Ah battery is
> speced to output .35 amps per hour over a 20 hour discharge.
> But don't let reality get in the way of a fun project.
"Nothing in this world can take the place of persistence. Talent will not; nothing is more common than unsuccessful people with talent. Genius will not; unrewarded genius is almost a proverb. Education will not; the world is full of educated derelicts. Persistence and determination alone are omnipotent. The slogan 'press on' has solved and always will solve the problems of the human race"
~ Calvin Coolidge
More information about the Homestead