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Home made generator?

N

news.zen.co.uk

Jan 1, 1970
0
Hi

I don't know as much as i'd like about electrics, but i thought someone here
might be able to help.

Here's the thing...I need a generator. New, they're around £100 for a 750W,
but I've got an old 3.5 bhp engine which, i imagine is half of what the
generator actually is.

What i'd like to know is there anything i can buy (like just the generator
bit) or use (like a car's alternator) to 'bolt on' to the engine to produce
electricity to power lighting/power tools etc..to save buying a new genny?

Any thoughts appreciated!
\sh
 
J

John

Jan 1, 1970
0
"news.zen.co.uk" wrote
I don't know as much as i'd like about electrics, but i thought someone
here might be able to help.

Here's the thing...I need a generator. New, they're around £100 for a
750W, but I've got an old 3.5 bhp engine which, i imagine is half of what
the generator actually is.

What i'd like to know is there anything i can buy (like just the generator
bit) or use (like a car's alternator) to 'bolt on' to the engine to
produce electricity to power lighting/power tools etc..to save buying a
new genny?

It will probably cost you more in materials and parts than it would to buy a
new unit.

It will certainly cost you vastly more in terms of your time and effort
 
A

Andrew Gabriel

Jan 1, 1970
0
You could certainly get 750w out of a big car alternator but this
won't be the one in a Mini. Big old Detroit iron had alternators in
the 70-100a range. An old cop car or a Caddy is a good start.
Your 3.5 HP engine should spin it up. The problem is that is 14v or
so. You will still need an inverter to make that mains voltage.
I am doing a similar thing here for hurricane outages but I only run
small loads and some are 12v

The Lucus alternator used in old UK minis (and some other UK cars of
that era) generated up to 42A at idle speed, but only went up to about
48A max a little above idle, and produced no further increase in power
output as you raised the engine speed further. Nowadays, alternators
are controlled digitally by the engine management unit, and won't work
standalone.
 
J

James Sweet

Jan 1, 1970
0
You could certainly get 750w out of a big car alternator but this
won't be the one in a Mini. Big old Detroit iron had alternators in
the 70-100a range. An old cop car or a Caddy is a good start.
Your 3.5 HP engine should spin it up. The problem is that is 14v or
so. You will still need an inverter to make that mains voltage.
I am doing a similar thing here for hurricane outages but I only run
small loads and some are 12v


Big alternators are everywhere these days. The factory Bosch unit in my
Volvo 740 is 100A and it has a convenient internal regulator. I have an
extra one in the garage awaiting just such a project, since I also have
a perfectly good 3HP engine sitting around. Any luxury car from the mid
80s on should have at least a 70A alternator. Seat heaters, power
windows, power seats, all that stuff sucks a lot of juice.
 
J

James Sweet

Jan 1, 1970
0
There was a hack to the voltage regulator that allowed you to get 120v
out of one (over on this side where we use it). They sold the kit at
places like JC Whitney but I haven't seen it lately.
It is not in the 50/60 hz range at all though. This is high frequency
AC. It was sold to run drills and other "universal motor" type tools.


If you run the field coil flat out, you can get even more than that
without rewinding. You have to spin it pretty fast and obviously you
will not get anywhere near the full rated load current. The output is
unfiltered DC unless you tap off prior to the diode pack in which case
it will be 3 phase AC.
 
J

James Sweet

Jan 1, 1970
0
John said:
"news.zen.co.uk" wrote

It will probably cost you more in materials and parts than it would to buy a
new unit.

It will certainly cost you vastly more in terms of your time and effort


Clearly if you were to go buy all the parts it would, however he has an
engine already, and a used alternator can be had for anywhere from free
to $30 bucks or so, can't really factor in the time and effort if you're
the sort who enjoys this stuff, and what decent engineer doesn't?
 
N

news.zen.co.uk

Jan 1, 1970
0
James Sweet said:
If you run the field coil flat out, you can get even more than that
without rewinding. You have to spin it pretty fast and obviously you will
not get anywhere near the full rated load current. The output is
unfiltered DC unless you tap off prior to the diode pack in which case it
will be 3 phase AC.

Many thanks for all the replies, folks. You've all given me something to
think about.

And now I think I'm going to try and get hold of a decent sized alternator
and give that a go.

Cheers again!
\sh
 
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