Mailing List flyrotary@lancaironline.net Message #17736
From: Jeff Waltermire <bearhawk767@gmail.com>
Subject: Re: [FlyRotary] Re: 2nd battery Re: Amps required to run engine&amp- hours available
Date: Tue, 22 Feb 2005 20:03:24 -0500
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
I exceeded the size limit for the picture on this gizmo for a second alternator when I sent it earlier.  Now I'll just paste a URL for you.  It's as close as your nearest John Deere dealer.  The info comes from the site http://home.hiwaay.net/~langford/corvair/dynamo.html
Jeff. 

Charlie England wrote:
Ernest Christley wrote:

Bobby J. Hughes wrote:

Found the picture. The catalog seems to be missing.
http://www.racemate.com/home.htm


 

There that's better.  The claim that it won't overvoltage is absolutely false.  In the bottom of the picture on the right.  That is the regulator.  It works by dumping excess energy to ground.  It looks like a heat sink, because it IS a heat sink.  If that thing burns out and you rev high enough that the rest of your system can burn off what the generator puts out, you're in an overvoltage situation.

The specs claim 1/3rd Hp to drive it.  That is about 18A at 13.5V.  I'll make a big assumption here and assume that they rated that at 5500RPM, the same number they used to compare the pump flows at the bottom of the spec page.  Using this on the end of the crankshaft would be a simple matter of bolting the coil pack to the front housing and the bolting the 'can' that carries the magnets to the end of the shaft.  Many motorcycles use this exact same setup, and you can buy some of those packages for about $100.  I looked at and rejected those, because 18A isn't enough for a replacement; though it will do as a backup.

Harley Davidson makes a similar setup for their Goldwing bikes that is 35A.  That is the one I want to look at.

I'm one of the early speculators/hopefuls about whether the crank angle sensor shaft/gear could handle the torque of a small alternator supplying just engine electrical power. The eshaft is obviously a safer route if no one can do the sensor shaft calcs with confidence.

18 amps should be plenty to run the engine stuff. Start using ship's power & switch to the crank mounted alt. automatically (as someone else mentioned) as rpm comes up. Use the a/c electrical system (which backs up itself at low current demand levels) as backup for the engine's power. Now it's triple redundant.

The eshaft thing should be do-able with the little Kubota PM alternators if you can rig a little 3 legged support in front of the eshaft pulley & bolt a flex coupler to the front of the pulley to drive the alt. shaft.

There's also a crank mounted alt. sold by one of the VW conversion houses. I posted a link to it several months ago; I'll try to find it again if anyone's interested.

The ideal way to control it would be a switching regulator instead of the linear shunt that seems to be common, but I doubt there's an off-the-shelf model that would handle the rather wide input voltage swing (probably <12v to >60v)  give 14v out.

Charlie



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