G'day cloudmagnet, All
At 02:49 AM 30/01/2010, cloudmagnet wrote:
>In the Photo section, in the "Default Club Album", there is a photo
>of an outboard motor conversion (top row, second from right) to
>electric. Now, from what I've been able to determine, an outboard
>engine turns over at anywhere from a few thousand RPM to as much as
>5 or 6 thousand, while most electric motors top out at 2500 RPM or
>so. Can someone tell me how this seeming disparity in input speed
>equates to output? What electric motors would be appropriate for
>this type of conversion? Thanks
I don't know what motors you have been looking at, but 2500RPM is
pretty low. My two outboards (1.5kW and 4kW) rev to about 4500RPM,
most on-road electric cars rev to 4500 to 6000RPM for DC motors and
9000 to 12000RPM for AC motors.
Forklifts and other similar vehicles are designed using low battery
voltage and high loading to be unable to be over-revved under normal
conditions, without active rev limiting. As such they use motors that
are rated in the range of 1500 to 2800RPM, but they are only
nameplate ratings - the ratings that the manufacturer put on them as
a statement of performance under certain conditions that suit the
application - these ratings are typically exta-ordinarily
conservative over what the motor is capable of.
DC motors that are very large are also low revving - but any that big
are way too big for an outboard. A motor 9" (230mm) in diameter by
18" (450mm) long can do 5500RPM, most motors smaller than this can do
at least these RPMs. How big an outboard are you after?
Typically the rev range of a brushed DC motor is very similar to the
rev range of an ICE, so are a good replacement.
Hope this helps
Regards
[Technik] James
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