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From: firstname.lastname@example.org (Bill Allison)
Subject: Re: Help - Power mosfets - difficult load
Date: 22 Oct 2002 17:07:30 -0700
References: <email@example.com> <firstname.lastname@example.org> <email@example.com> <firstname.lastname@example.org> <email@example.com>
NNTP-Posting-Date: 23 Oct 2002 00:07:31 GMT
"Phil Allison" wrote in message news:...
> "George Gonzalez" wrote in message
> > A late thought- should have been my fiest question-- are you
> > really sure you need the torque and RPM's of a car starter motor?
> > What is the maximum anticipated pull? What max pull speed do you need?
> > If you're talking about your standard model airplanes, with engine HP much
> > less than 1 HP, then you probably don't need the torque of a car starter
> > motor-- something more like a car antenna motor sounds like a much closer
> > ballpark.
> > I suspect a car starter motor could tether anything up to a DC-3
> ** In fact a DC-3 usually has two 1200 horsepower, 14 cylinder, Pratt
> and Whitney radial engines to get it moving along at a modest speed.
> A car starter motor is widely used for the job Bill Allison is
> intending - but with a simple resistor bank and switch to vary the rpms.
> ......................... Phil
Phil is spot on George - you pretty much said it yourself when you
mentioned 1hp. To take a 5 to 10 pound aircraft up a 470 feet angled
climb to an altitude of 350ft in 10 secs or so needs about 0.5
horsepower which roughly equates to 1hp power unit after propeller
losses are taken into account. So my starter motor (spec says 800 watt
output which is a shade over 1hp) should be about right with a nice
margin. Car antenna motor is miles too feeble.
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