---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Fri 12/29/06: 5 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 10:22 AM - What Are The Odds (Sally Kilishek) 2. 12:10 PM - Re: Pitot/antenna (Phil Birkelbach) 3. 03:44 PM - Re: Re: Back-Up Battery ground (Pat Salvati) 4. 07:50 PM - Re: Pitot/antenna (Robert L. Nuckolls, III) 5. 09:24 PM - Re: What Are The Odds (Robert L. Nuckolls, III) ________________________________ Message 1 _____________________________________ Time: 10:22:02 AM PST US From: Sally Kilishek Subject: AeroElectric-List: What Are The Odds Chuck: Good question. I'm an getting overvoltage light from the annunciator panel, which uses one sensor to pick up buss voltage, and getting a digital voltage readout from a separate sensor on the EMS. Both concur on the overvoltage. In terms of wiring, I think the following is true: We're getting 12 volts to the regulator and the connection from the regulator to the field terminal is sound (since the alternator is charging). The OVM-14 overvoltage device is working (alternator cuts off when voltage goes over 15 volts). I can't tell whether the regulator is not regulating or is regulating at >15 volts. George Chuck Jensen wrote: Are you measuring the voltage with a minimum of two different instruments? In short, are you sure it is the voltage and not the measuring device/indication? Chuck Jensen -----Original Message----- From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Sally Kilishek Sent: Thursday, December 28, 2006 12:39 PM Subject: AeroElectric-List: What Are The Odds (Was Over Voltage) --> Never to be deterred by experience, I installed yet another new VR749 regulator the other day. This was the fourth one. It worked fine for about 20 minutes, then showed the same behavior as the other three: oscillations between overvoltage of 15+ volts and apparent cut off. What are the odds that four consecutive regulators would be bad? Is there anything else in a plane wired per Z22 that could account for this behavior? Temperatures here are in the 40s and 50s. Could a negative temperature coefficient be causing the regulator set point to rise above 15 volts? George Dennis Haversham wrote: I have the same regulator (VR 749) controlling a 100 amp Mazda alternator. I'm running the engine on the ground while I finish the A/C but I've experienced the same thing. High voltage at the battery... Sally Kilishek wrote: > >I'm using a generic Ford regulator (Wells VR749) and a >B&C OVM-14 overvoltage module wired as per Z-22 in my >RV8. > >It worked fine for a short time, but after about 4 >hours of flying, the overvoltage indicator light >started flickering. Bus voltage is rising above 15 >volts (one time as high as 16 volts), then dropping >back below 15 volts and immediately rising again. > >It looks to me like the regulator isn't regulating and >that the OV module is cutting off the field excitation >until voltage drops below 15. > >I've replaced the regulator twice, but the problem >continues. > >Is there somewhere else I should be looking? > >George >N57G __________________________________________________ ________________________________ Message 2 _____________________________________ Time: 12:10:00 PM PST US From: Phil Birkelbach Subject: Re: AeroElectric-List: Pitot/antenna That aft-end of the T could be closed with some small radially drilled holes and used as the static port. Godspeed, Phil Birkelbach - Houston Texas RV-7 N727WB http://www.myrv7.com Bill Boyd wrote: > > > No reason I see why we can't have the pitot shaped like an inverted-T > rather than an L. That would allow more top (bottom) loading to be > added, and the "hat" would not radiate, thus negating any directivity > effects that would arise from the L-shape. The back of the T would be > strictly antenna-related and not needed for Pitot, of course. > > I like it. > > -Bill B > > On 12/26/06, Robert L. Nuckolls, III wrote: >> >> >> At 02:18 PM 12/26/2006 -0500, you wrote: >> >> >> > >> >I wonder if we could prototype a helically-loaded "rubber duck" comm >> >antenna and slip a polypropylene tube inside it with an L-bend at the >> >end to act as a pitot; encase the whole thing in a streamlined radome. >> >Interesting excercise. Bandwidth would inevitably suffer from the >> >physical shortening versus a quarter wave. A lossy loading coil would >> >give some feeble de-ice heat during Tx (just kidding.) A lot of work >> >to shave a half knot of speed penalty, but a fun excercise >> >nonetheless. If I weren't busy with other projects, it's just the >> >kind of thing I'd try. >> > >> >Come to think of it, a full size transponder antenna would easily fit >> >in a very modest blade pitot housing... >> >> Cool! Hadn't considered that. >> >> Hmmm . . . maybe better yet, slice metal pitot tube into >> horizontal and vertical portions (right across >> the knee joint). Materials that traverse the joint wound >> have to be non-conductor -OR- fabricated in a way >> that provides loading components for the comm antenna. >> >> Now the horizontal portion becomes more of a minimally >> radiating top-hat and the vertical mast enjoys majority >> current flow in the right polarity. >> >> THAT could work! Except for the inevitable distortion >> in pattern that arises from a leading edge location >> on wing, it might function rather well. >> >> If I can get an IR&D activity spun up next year, I'll toss >> that out on the table to see if some RF-inquisitive guys >> might like to go mock that up in the lab. It would be an >> easily crafted experiment. >> >> Bob . . . >> >> >> >> >> >> > > ________________________________ Message 3 _____________________________________ Time: 03:44:02 PM PST US From: Pat Salvati Subject: Re: AeroElectric-List: Re: Back-Up Battery ground Touche' ________________________________ Message 4 _____________________________________ Time: 07:50:56 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Pitot/antenna At 02:08 PM 12/29/2006 -0600, you wrote: > >That aft-end of the T could be closed with some small radially drilled >holes and used as the static port. That kind of rings a bell for something I've seen before although I'm sure the pitot-static tube was not also an antenna. Great thought! I'll add that to the mix. A pitot-static tube that is also a reasonably efficient antenna. I believe that's doable. Bob . . . ________________________________ Message 5 _____________________________________ Time: 09:24:39 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: What Are The Odds At 10:16 AM 12/29/2006 -0800, you wrote: > >Chuck: > >Good question. > >I'm an getting overvoltage light from the annunciator >panel, which uses one sensor to pick up buss voltage, >and getting a digital voltage readout from a separate >sensor on the EMS. Both concur on the overvoltage. > >In terms of wiring, I think the following is true: > >We're getting 12 volts to the regulator and the >connection from the regulator to the field terminal >is sound (since the alternator is charging). "Getting 12 volts" is not especially definitive. Do the specific votlage measurement cited below . . . >The OVM-14 overvoltage device is working (alternator >cuts off when voltage goes over 15 volts). How does it "cut off"? The OVM-14 is supposed to trip the field supply breaker. If the breaker does not trip, the OVM-14 is not a part of this trouble-shooting task . . . >I can't tell whether the regulator is not regulating >or is regulating at >15 volts. Easy. Use a voltmeter to measure between the A/S terminals and regulator case. THIS is the point where the regulator believes it is seeing bus voltage. You may find that it it sitting happily at 14.2 volts while voltage drops in wiring BETWEEN the A/S terminals and the BUS are cause for an artificially raising of regulation set-point. Take one of your regulators and install some short leads on it as illustrated below. Install right on the back of the alternator and see what the bus voltage does while the engine is running and you vary loads by turning things on and off. These experiments totally bypass all other ship's wiring. http://www.aeroelectric.com/Pictures/Regulators/Alternator_Test_1.jpg http://www.aeroelectric.com/Pictures/Regulators/Ford_Test_Reg.jpg I think you'll find that the alternator and regulator are fine . . . there's some bug in installation. Conduct the experiments cited above and report back the results. We can begin to divide the probabilities-list into manageable partitions. Bob . . . ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message aeroelectric-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/AeroElectric-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/aeroelectric-list Browse Digests http://www.matronics.com/digest/aeroelectric-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.