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Old 11-25-2007, 11:15 PM   #184 (permalink)
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Join Date: Nov 2007
Location: 1000 Islands, Ontario, Canada
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Blackfly - '98 Geo Metro
Team Metro
Last 3: 70.09 mpg (US)

MPGiata - '90 Mazda Miata
90 day: 52.07 mpg (US)

Winter beater Metro - '00 Chevrolet Metro
90 day: 61.98 mpg (US)

Fancy Metro - '14 Mitsubishi Mirage top spec
90 day: 58.72 mpg (US)

Even Fancier Metro - '14 Mitsubishi Mirage top spec
90 day: 70.75 mpg (US)
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11-27-2006, 10:23 Am

Well, here's a bit of a blunder:

Contrary to what I reported a few posts back, our motor does NOT reverse direction by reversing the polarity on its 2 terminals. And guess what: its default rotation is the WRONG way for the transmission.

Permanent magnet motors can run either direction depending on polarity of the armature. 4-terminal series motors can be run either way by reversing the polarity of the field. (Assuming neutral brush timing and perpendicular brush/commutator setup.)

But I learned last night that 2-terminal series motors (such as we have) are wired to only rotate in one direction, regardless of polarity at the terminals.

So now we have to look at rewiring the field.

I won't pretend otherwise: this could be a grande screwup. When we hooked up the motor on the bench last week and reversed the polarity, we only confirmed that the motor ran. We didn't think to actually look in the end and check that the shaft was spinning the opposite way.

Worst case scenario: we have 2 pump motors that would work great on Honda transmissions!

More likely we just have to reverse (re-route) connections between the field & brushes/rotor.

I'm sure my ignorance must be entertaining. Still on ye olde learning curve, that's for sure.
Honda mods: Ecomodding my $800 Honda Fit 5-speed beater
Mitsu mods: Oops, I did it again! Bought another cheap, 3-cylinder Mirage. Mods in progress...
Ecodriving test: Manual vs. automatic transmission MPG showdown

has launched a forum for the efficient new Mitsubishi Mirage - fuel efficiency info for Geo Metro owners - electric car conversion on a beer budget
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