---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Tue 04/04/17: 5 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 04:06 AM - Re: old B and C SD-8 Dynamo failure (user9253) 2. 04:50 AM - Re: old B and C SD-8 Dynamo failure (Robert L. Nuckolls, III) 3. 07:43 AM - Re: old B and C SD-8 Dynamo failure (ashleysc@broadstripe.net) 4. 08:45 PM - MGL CHT probe (Jeff Point) 5. 09:05 PM - K Type Thermocouple Wire Striping (William Hunter) ________________________________ Message 1 _____________________________________ Time: 04:06:42 AM PST US Subject: AeroElectric-List: Re: old B and C SD-8 Dynamo failure From: "user9253" The saying, "Ring it out", when referring to electrical testing, got its beginnings when troubleshooters used a doorbell for testing electrical motors. There is not much difference in resistance between a good motor and one with a shorted winding. But there is a difference in the inductance. An experienced electrician could tell the difference in doorbell sound when connected in series with a shorted motor winding compared to a good winding. Modern doorbells are not suitable for this task. The doorbell must be of the old fashioned clanger and bell type. This information might be of use to you 27 years from now when your new SD-8 dynamo malfunctions. :-) -------- Joe Gores Read this topic online here: http://forums.matronics.com/viewtopic.php?p=468022#468022 ________________________________ Message 2 _____________________________________ Time: 04:50:40 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: old B and C SD-8 Dynamo failure > >I have no complaints about this SD-8 failure. I certainly got a >reasonable service life out of this unit. I just thought I'd share my >story as just one more data point, although I appreciate it's kinda >ancient history. I'm planning on taking the dynamo apart (curiosity) >and maybe salvaging the magnets. Are the windings smoked? Do they smell bad? The DC resistance of this product is less than 0.25 ohms. So if you had a shorted turn or two, you could not resolve it with jelly-bean test equipment. The magnets are ferrites . . . rather brittle. You probably couldn't get them loose without breaking them up. >Bob, if you wanted to look at this dynamo for some reason, I'll be happy >to mail it to you. I suspect you've got much better things to do than >'paleo-forensics' on this dated item. > >Mark Actually, I would like to see it. I have a drive stand running that fits the SD8 and I'm equipped to test/inspect it in detail. Getting a close up look at a sample with this kind of service on it would be illuminating. Send the rectifier/regulator too. I'll get them checked out and repaired/replaced as needed. Bob . . . ________________________________ Message 3 _____________________________________ Time: 07:43:28 AM PST US From: ashleysc@broadstripe.net Subject: Re: AeroElectric-List: old B and C SD-8 Dynamo failure Hi Mark; Hi All; I read this as an endorsement, not a complaint. Who gets 27 years of operation from a car, washing machine, or computer? It gives me great confidence in B & C products. Cheers! Stu. ----- Original Message ----- From: "Mark Todd" Sent: Monday, April 3, 2017 10:32:48 PM Subject: AeroElectric-List: old B and C SD-8 Dynamo failure Well, after 27 years and 2300+ hours, my good old SD-8 dynamo finally gave me a problem. It was installed in my day/VFR RV4 in 1989 as the only charging source. It could produce up to 8.6 amps at high RPM and met my modest electrical load requirements (<4 amps in cruise) for all these years. Of course, I could expect my low voltage light to come on (at 12.5V) at low rpms depending on the loads. I didn't mind. It made for a nice reminder to turn off my boost pump as I exited the runway on landing. On a recent flight, I noticed that the low voltage light came on a little earlier than I expected on landing. At high RPM, the voltage was only going to 13.9 instead of the usual 14.1V. A quick run through my switchable loads showed they were pulling their expected currents. I have a switchable volt/amp gauge on my panel so I can look at one or the other but not both simultaneously. The amp readings are taken off my B lead and it takes several seconds for the amp reading to stabilize on my gauge after it's selected. I never saw an unexpectedly high amp reading on the gauge. Back at the hangar, a brief look at my B lead connections didn't reveal any problems. On the next flight, the low voltage light came on even sooner and the voltage only got to 13.7V. A more detailed inspection was made of the wiring, including micro-ohming some connections (using Bob's 100mA current clamp micro-ohmmeter design I've enjoyed using for several years). I thought I detected a little bit of a burnt electrical smell near the dynamo housing where the armature leads pass through a clip screwed into the rim of the housing. Using a cheap digital multimeter, I checked the resistance across the disconnected dynamo leads and got 5.6 ohms. Not sure what it's suppose to be. I flew the plane again and this time, I got a low voltage light in cruise and zero B lead amps when checked. I checked the resistance across the dynamo leads again with the same meter.. and got a reading of zero. My micro-ohm meter said it was about 700 milliohms. I bought a new SD-8 and am back in the air trouble free. Since removing the problem unit, I removed the clip that held the leads at the rim of the dynamo housing and slid the protective sheathing back. The lead wires look fine, including the half-inch of wire I can see inside the housing. The resistance across the leads remains 'zero' when checked with another cheap digital mulitmeter. I concluded that I had probably experienced a progressive short within the dynamo, probably in the windings themselves. This dynamo was from the 1980's and the exterior design has changed a lot since then. This includes a protected routing of the leads out of the dynamo housing with a better clamping system. The insides have probably changed as well. Lord knows the new unit is easier to install with much better access to the mounting nuts. I have no complaints about this SD-8 failure. I certainly got a reasonable service life out of this unit. I just thought I'd share my story as just one more data point, although I appreciate it's kinda ancient history. I'm planning on taking the dynamo apart (curiosity) and maybe salvaging the magnets. Bob, if you wanted to look at this dynamo for some reason, I'll be happy to mail it to you. I suspect you've got much better things to do than 'paleo-forensics' on this dated item. Mark ________________________________ Message 4 _____________________________________ Time: 08:45:13 PM PST US From: Jeff Point Subject: AeroElectric-List: MGL CHT probe I recently purchased the MGL 18mm spark plug CHT probes from Aircraft Spruce. The photo on both their website and MGL's shows a copper ring soldered to a K-type thermocouple wire, a pretty standard setup. What they sent me is pictured below. Since the bare wire ends connect directly to the RDAC brain box, I deduced that the other end- a 1/4 PIDG fast-on, crimped to the thermocouple wires- must just attach to the copper ring. The tab end of the copper ring is exactly 1/4 inch, so this makes sense. This seems like a pretty cheeseball setup. From what I know of K-type thermocouples (mostly from reading the 'Connection) that wires must be silver soldered to the probe and to each other. Or, am I mistaken and is this a reasonable setup? I am also reaching out to MGL about this, but I thought I'd ping this group for your thoughts as well. Thanks Jeff Point Milwaukee ________________________________ Message 5 _____________________________________ Time: 09:05:56 PM PST US From: William Hunter Subject: AeroElectric-List: K Type Thermocouple Wire Striping Hi All, How does one (me) strip K Type Thermocouple Wires. The wire I bought from eBay Aircraft Supply has a metal shield and two wires inside that appear to be covered with some kind of a fabric type insulator. The metal shield can be stripped back with a pick, bandaids, and some bad words. The two inner wires insulation do not strip back with a mechanical wire stripper and if I use a razor blade the fabric insulation will simply unravel like a sweater thread. There has got to be a better way?!?!? Thanks, Bill Hunter On Apr 4, 2017 8:55 PM, "Jeff Point" wrote: I recently purchased the MGL 18mm spark plug CHT probes from Aircraft Spruce. The photo on both their website and MGL's shows a copper ring soldered to a K-type thermocouple wire, a pretty standard setup. What they sent me is pictured below. Since the bare wire ends connect directly to the RDAC brain box, I deduced that the other end- a 1/4 PIDG fast-on, crimped to the thermocouple wires- must just attach to the copper ring. The tab end of the copper ring is exactly 1/4 inch, so this makes sense. This seems like a pretty cheeseball setup. From what I know of K-type thermocouples (mostly from reading the 'Connection) that wires must be silver soldered to the probe and to each other. Or, am I mistaken and is this a reasonable setup? I am also reaching out to MGL about this, but I thought I'd ping this group for your thoughts as well. Thanks Jeff Point Milwaukee ------------------------------------------------------------------------------------- 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.