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Date: Sun, 05 Jul 2009 09:59:16 -0500
From: Charlie England <ceengland@bellsouth.net>
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To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Overvoltage ?   [FlyRotary] Re: Modify Alternator
 for External Regulator
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If you have a controllable circuit breaker or a switchable relay in 
series with the B-lead, you can control an over-voltage event. The 
Aeroelectric connection offered a 'crowbar' type protector for a while 
that would disconnect the B-lead automatically, and if memory serves, 
Bob Nuckolls now says that with an effective attention-getter to notify 
of over-voltage, the battery will easily damp the voltage to below 
damage-causing levels long enough to hit the B-lead disconnect. The only 
issue left is whether there is enough combustible material in the 
alternator itself to cause any real danger as it runs away, electrically 
isolated from the rest of the plane.

My personal opinion is that each person should carefully evaluate the 
relative risks of opening & modifying an inherently extremely reliable 
device, at their personal skill level. I spent about half my working 
life doing electronics service work and I'm pretty confident in my 
abilities in this area. My flying RV-4 (Lyc) has an unmodified '1-wire' 
alternator.

Charlie

Ed Anderson wrote:
>
> Just curious, Todd. When you had your alternator run-a-way, did you 
> have a battery or other load on the line. Yes and you are correct, 
> just because the odds are 1 in 1000,000 does not mean your 1 couldn’t 
> come up tomorrow. And I STILL DON”T use approved plastic fuel cans (or 
> any other kind) – one refueling fire was enough {:>).
>
> Thanks for providing that info to the list – now others can see 
> alternator over voltage is a possibility with a car alternator and 
> without the modification to the field coil circuit may be impossible 
> to shut down – short of shutting down your engine.
>
> But, if 60 years of experience is not worth anything regarding 
> alternators – then what is experience worth regarding anything. Like 
> just about everything else in this “hobby”, you are constantly 
> assessing risk (or should be) and I decided the risk of modifying my 
> alternator to eliminate the remote risk (base on my experience) of 
> over voltage was higher than an over voltage condition. YMMV {:>)
>
> Ed.
>
> Ed Anderson
>
> Rv-6A N494BW Rotary Powered
>
> Matthews, NC
>
> eanderson@carolina.rr.com
>
> http://www.andersonee.com
>
> http://www.dmack.net/mazda/index.html
>
> http://www.flyrotary.com/
>
> http://members.cox.net/rogersda/rotary/configs.htm#N494BW 
> <http://members.cox.net/rogersda/rotary/configs.htm>
>
> http://www.rotaryaviation.com/Rotorhead%20Truth.htm
>
> ------------------------------------------------------------------------
>
> *From:* Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] 
> *On Behalf Of *Todd Bartrim
> *Sent:* Sunday, July 05, 2009 3:07 AM
> *To:* Rotary motors in aircraft
> *Subject:* [FlyRotary] Re: Modify Alternator for External Regulator
>
> Yeah, that's what I said too Ed, then it happened to me when I was 
> still early in my flight test (on the ground fortunatly).
> However after years of carelessly pouring regular old auto fuel from 
> plastic fuel cans, despite all the warnings, I've yet to have a 
> problem. But I did hear of a guy that caught his plane on fire this 
> way. ;)
> So yeah, I'm sure it could happen. Hope it doesn't though. It would 
> sure ruin my day.
>
> Could it happen, undoubtedly, however, in 60 + years of driving 
> automobiles, I have never, never had an alternator run wild – the ones 
> that failed, just died. So if I can get by another 60 years {:>), then 
> I’ll probably hang up my wings (or who knows perhaps get another pair {:>)
>
>
>
> Ed
>
> Todd
> C-FSTB
> RV9 Turbo13B
>
>
>
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