On Tue, 18 Aug 2009 14:21:15 +0100, Dave Plowman (News) wrote:

In article . com,
Jules wrote:
Sounds like an extremly simple & practical idea - along the lines of
the wind up radio. Possibilities are endless, hook up a hydralic
pump instead of an alternator & the world is your lobster.

Still cheaper to use an inverter with most vehicles. You then have the
choice of cheap mass produced mains devices.

How well do they cope with big inductive loads such as motors though,
where the start-up surge can be quite big? (i.e. the well pump that the
OP refers to)

In the same way as your generator driven off the car wheel would - it
needs to be butch enough to cope with a starting load.

I agree it seems like a good solution if running everyday electronics out
in the wilds, I just don't know how well it'd stand up to running the
'bigger stuff'.

You need one rated for the job.

OK... I was just curious as most inverters I've seen are piddly little
things which seem like they'd happily go bang if given any serious work to
do :-) (but fine for running laptops etc.)

Friction drives are horribly inefficient - as well as the safety issues.

No argument there! In the OP's case I'd be looking at something* other
than a roller drive. But some somewhere where keeping things running is
more important than the efficiency or safety, I can imagine it might make
a good minimum-maintenance solution.

* going IC engine - roller drive - alternator - motor - pump does seem
a bit clunky. Even jacking up one back wheel of the vehicle and
tapping mechanical power straight from there to drive the pump might be
relatively painless (given enough hub bolts on the wheel it might just be
a case of removing two or three and bolting a drive flange to them - no
need to even take a whole wheel off). There's still the inefficiency of
the vehicle's drivetrain, but OTOH it allows better matching of engine and
pump speed.

cheers

Jules