Electric motors generally exceed 80% efficiency.
Gas motors rarely exceed 25% efficiency.
Figure less than 6 V drop for a 75 foot extension cord
at 15A and less than 4 V drop at 10A.
120 - 6 = 114 V. That'd work great!
Good electric motors exceed 80% efficiency, cheap electric motors as
used in electric trimmers - not even close.
Gas motors may not be very efficient fuel wise, but a 1hp gas motor
outputs 1hp as long as it has fuel.
Either approach would work great.
I hear as a general rule of thumb that it takes
more 'HP' of gas engine to provide the same 'power'
as that of a same-rated electric motor under load.
I know, it sounds like nonsense on the face of it.
I suspect it has something to do with the different
torque curves of the two, though I don't know for sure.
The electric type would be very much quieter
and easier for her to use. Most importantly,
she *would* use it instead of getting rid of
it in a garage sale.
An electric motor can output more than it's rated HP for a short time if
sufficient electricity is available vs. a gas engine which can not
generally exceed it's rated HP. If the electricity is not available to
support the extra HP, either due to voltage drop from long extension
cords or circuit breakers tripping, you won't get any extra HP.
Your calculations are way off. First there is the length of the house
wiring from the service entrance to wherever you plug in the extension
cord. Then there is the cord itself and loss at connections which are
rarely perfect. If the combined total length of the house wiring and
the extension is more than 50 feet, you need to get a MUCH heavier
extension cord. 14AWG is not going to cut it. Go to a 10 AWG if you
want the power at the outlet to arrive at the tool. Unfortunately,
your diminuative friend will need a wheelbarrow to move that extension
You wouldn't know it from my suave, debonair
delivery on USENET, but I have yet to develop
the sophistication to allow my friends to think
my proffered solution was their idea all along.
This is unfortunate because like most folks on
this forum, I find 'engineering challenges'
fascinating. Mostly I enjoy the expression on
the face of my friends when they 'get' a
concept I've been trying to communicate.
(Well, OK they dry out and go from green to straw
color. But they do not pull out of the ground with
less than several hundred pounds of force and have
a very strong, fibrous stalk.)
Pictures are not convenient at the moment.
Not a problem though. Just envision a single stalk
about 1/4" to 3/8" inch in diameter, sticking about
3' to 4' in the air. They grow like a science fiction
experiment. They are completely absent in lots
surrounding hers and only appeared in her lot within
the last three years. Really spooky.
Our extension office has been closed for about 5 years.
He's doing it wrong. For starters, there are a lot of variations on
Round Up. Most people buy the cheaper versions that is 'pre-watered
down". Buy the full strength stuff, and mix it yourself to whatever
styrength is needed for each individual situation. The stuff that
comes in a spray bottle won't kill anything that is much tougher than
Mix 10-12 oz of full strength Round Up to a gallon of water and you
can kill astroturf and fake palm trees.
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