---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Fri 07/22/11: 13 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 05:36 AM - Re: Airframe ground connection (Robert L. Nuckolls, III) 2. 07:27 AM - Re: Airframe ground connection (user9253) 3. 08:23 AM - Re: Re: Airframe ground connection (George, Neal Capt 505 TRS/DOJ) 4. 09:15 AM - Re: Re: Airframe ground connection (Robert L. Nuckolls, III) 5. 10:05 AM - Re: Airframe ground connection (Louie928) 6. 10:19 AM - Lamar MC 10 with internally regulated alternator (josnooze) 7. 11:30 AM - Re: Re: Airframe ground connection (Robert L. Nuckolls, III) 8. 12:20 PM - Re: Airframe ground connection (Louie928) 9. 01:22 PM - l5t06e 1ipfv (Vincent Welch) 10. 01:32 PM - Re: l5t06e 1ipfv (Harley) 11. 01:44 PM - Re: l5t06e 1ipfv (RGent1224@aol.com) 12. 03:22 PM - Re: l5t06e 1ipfv (Vincent Welch) 13. 03:32 PM - Re: l5t06e 1ipfv (Harley) ________________________________ Message 1 _____________________________________ Time: 05:36:17 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Airframe ground connection > >Or, run a +12V #4, and a ground #4, to the starter and engine >thereby bypassing the airframe from the large starter current. The >wire length from battery to engine is about 7 feet. That's the 'clean' way to do it. #4 welding cable for battery wires. Take battery (-) to firewall feed through bolt, battery (+) through battery contactor and then firewall to starter contactor. Bob . . . ________________________________ Message 2 _____________________________________ Time: 07:27:35 AM PST US Subject: AeroElectric-List: Re: Airframe ground connection From: "user9253" > Something like 1/8" aluminum 2" or 3" in diameter riveted with, say 8 #4 rivets, to the underlying thin aluminum or galvanized steel to distribute the current? Rivets do not make very good electrical connections unless there are many of them in parallel (electrically). Certain brands of switches are prone to fail because they use rivets to carry the current. Joe -------- Joe Gores Read this topic online here: http://forums.matronics.com/viewtopic.php?p=347383#347383 ________________________________ Message 3 _____________________________________ Time: 08:23:29 AM PST US Subject: RE: AeroElectric-List: Re: Airframe ground connection From: "George, Neal Capt 505 TRS/DOJ" The switches that we've seen fail at riveted joints didn't fail because of the rivets, per se. They failed because rivets were used to join grossly dissimilar materials - Bakelite/plastic sandwiched between metal tabs - AND the leads were not supported adequately. In service, movement of the wire leads relative to the switch body flexed the terminal tabs, eventually loosening the riveted joint. As the riveted joint works and loosens, the gas-tight electrical connection is compromised. The less-than-ideal electrical connection introduces electrical resistance which manifests as heat. The heat further damages the loose rivet/plastic/copper interface thru corrosion and differential thermal expansion rates, and a destructive cycle of rising resistance, higher heat and accelerated damage results until the Bakelite cooks and crumbles or the copper bits inside anneal and deform to the point that the actuator can't move the rocker far enough to make/break the connection. Neal > Rivets do not make very good electrical connections unless there are many of them in parallel (electrically). Certain brands of switches are prone to fail because they use rivets to carry the current. Joe Gores >> Something like 1/8" aluminum 2" or 3" in diameter riveted with, say 8 #4 rivets, to the underlying thin aluminum or galvanized steel to distribute the current? ________________________________ Message 4 _____________________________________ Time: 09:15:58 AM PST US From: "Robert L. Nuckolls, III" Subject: RE: AeroElectric-List: Re: Airframe ground connection At 10:19 AM 7/22/2011, you wrote: TRS/DOJ" The switches that we've seen fail at riveted joints didn't fail because of the rivets, per se. They failed because rivets were used to join grossly dissimilar materials - Bakelite/plastic sandwiched between metal tabs - AND the leads were not supported adequately. In service, movement of the wire leads relative to the switch body flexed the terminal tabs, eventually loosening the riveted joint. As the riveted joint works and loosens, the gas-tight electrical connection is compromised. The less-than-ideal electrical connection introduces electrical resistance which manifests as heat. The heat further damages the loose rivet/plastic/copper interface thru corrosion and differential thermal expansion rates, and a destructive cycle of rising resistance, higher heat and accelerated damage results until the Bakelite cooks and crumbles or the copper bits inside anneal and deform to the point that the actuator can't move the rocker far enough to make/break the connection. An excellent recap of some extensive discussion shared here on the List some time back. Emacs! Rivets have been used to assemble gazillions of switches for decades. The designers of such devices strive for rivets not to be the "weakest" link in the chain of stresses on service life. Let's look at the inner workings of a Carling toggle (common to tens of thousands of Cessnas and certainly thousands of OBAM aircraft). We observe TWO features in the current carrying path that are more vulnerable to wear-out or environmental failure. One is the contacts. Resistance across the contacts is a function of spring pressure and contact surface condition. Resistance across the pivot-saddle is also a function of spring force and surface condition . . . but at least it gets "scrubbed" each operating cycle. Contacts just get "hammered". Contacts also benefit from the cleansing effects of electrical arcing to burn away products of corrosion. When installed with some attention to stresses on riveted terminals, one can expect failure of the low-pressure, moving-components to precede failure of the rivets by perhaps an order of magnitude of service life. Rivets in the switches are used in tension and they join a stack of materials that includes a plastic. Rivets in sheet metal are used in sheer. Further, if properly drilled and set, they swell up in the hole to form a metal-to-metal, gas tight fit . . . not unlike the gas-tight fit of wires properly mashed in the barrel of a terminal. Riveted doublers to reduce sheet current density around a high-current ground to airframe is probably not a 'bad' idea . . . but if there are concerns for getting a good ground in a thin-metal assembly, perhaps going around it entirely with a bundle of copper "cat-hairs" is a 'better' idea. Bob . . . ________________________________ Message 5 _____________________________________ Time: 10:05:18 AM PST US Subject: AeroElectric-List: Re: Airframe ground connection From: "Louie928" Neal.George(at)hurlburt.a wrote: > The switches that we've seen fail at riveted joints didn't fail because > of the rivets, per se. They failed because rivets were used to join > grossly dissimilar materials - Bakelite/plastic sandwiched between metal > tabs - AND the leads were not supported adequately. In service, > movement of the wire leads relative to the switch body flexed the > terminal tabs, eventually loosening the riveted joint. As the riveted > joint works and loosens, the gas-tight electrical connection is > compromised. The less-than-ideal electrical connection introduces > electrical resistance which manifests as heat. The heat further damages > the loose rivet/plastic/copper interface thru corrosion and differential > thermal expansion rates, and a destructive cycle of rising resistance, > higher heat and accelerated damage results until the Bakelite cooks and > crumbles or the copper bits inside anneal and deform to the point that > the actuator can't move the rocker far enough to make/break the > connection. > > Neal > > > > Rivets do not make very good electrical connections unless there are > > many of them in parallel (electrically). Certain brands of switches are > > > > prone to fail because they use rivets to carry the current. > Joe Gores > > > > > Something like 1/8" aluminum 2" or 3" in diameter riveted with, say 8 > > #4 rivets, to the underlying thin aluminum or galvanized steel to > > > > distribute the current? You make a valid point regarding the riveted connectors on the switches. I've come across the exact problem you describe in my work. It can lead to intermittent problems before identification of the actual trouble spot. I bought all my switches from B&C and was dismayed to see they have the riveted connection to the push on spade connector. It takes little effort to move the connector under the rivet. These have apparently been used in a lot of airplanes over a long time so maybe no problems have surfaced. I'll need to be sure I have the wires well supported near the switch with no strain on the riveted connector. Yes, distribute the current over a wider contact area of the thin aluminum, or steel. A simple bolted connection to 0.032" aluminum or the 0.018" galvanized steel firewall has a ridiculously small cross sectional area for the current to pass through. If it was wire it would be a very small CMA, like a fuse link. True, it is a short distance and the voltage drop won't be a lot. Heat will be generated which can contribute to problems down the road. If the bolted connection can be made through a thicker piece of material of 2 or 3 square inches area, and that thicker piece electrically connected to the thinner piece, the current will be distributed out to a much larger area of the thin metal and the current density won't be so high. -------- Louis W. Ott 601XL beginner Quick Build Read this topic online here: http://forums.matronics.com/viewtopic.php?p=347398#347398 ________________________________ Message 6 _____________________________________ Time: 10:19:50 AM PST US Subject: AeroElectric-List: Lamar MC 10 with internally regulated alternator From: "josnooze" Does anyone know of any problems using a Lamar MC 10 all-in-one electrical control box with a plane power 60 amp internally regulated alternator? The MC 10 has internal crowbar overvoltage and overcurrent protection. Read this topic online here: http://forums.matronics.com/viewtopic.php?p=347403#347403 ________________________________ Message 7 _____________________________________ Time: 11:30:25 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Re: Airframe ground connection It takes little effort to move the connector under the rivet. These have apparently been used in a lot of airplanes over a long time so maybe no problems have surfaced. I'll need to be sure I have the wires well supported near the switch with no strain on the riveted connector. Good practice . . . whether the terminals are riveted or not. Yes, distribute the current over a wider contact area of the thin aluminum, or steel. A simple bolted connection to 0.032" aluminum or the 0.018" galvanized steel firewall has a ridiculously small cross sectional area for the current to pass through. If you study the three sheets of Figure Z-15 found at http://www.aeroelectric.com/PPS/Adobe_Architecture_Pdfs/ You will see a directed effort to minimize the use of airframe for any ground return currents. If it was wire it would be a very small CMA, like a fuse link. True, it is a short distance and the voltage drop won't be a lot. Heat will be generated which can contribute to problems down the road. If the bolted connection can be made through a thicker piece of material of 2 or 3 square inches area, and that thicker piece electrically connected to the thinner piece, the current will be distributed out to a much larger area of the thin metal and the current density won't be so high. Assume a firewall ground feed-through stud is the central, single-point ground. Assume further that only a limited number of low-current remotely mounted accessories enjoy local airframe grounds, then current density and bonding issues go away. The firewall sheet carries a small percentage of the total system currents and never cranking current. Bob . . . ________________________________ Message 8 _____________________________________ Time: 12:20:15 PM PST US Subject: AeroElectric-List: Re: Airframe ground connection From: "Louie928" Thanks very much for helping clear this up. -------- Louis W. Ott 601XL beginner Quick Build Read this topic online here: http://forums.matronics.com/viewtopic.php?p=347416#347416 ________________________________ Message 9 _____________________________________ Time: 01:22:01 PM PST US From: Vincent Welch Subject: AeroElectric-List: l5t06e 1ipfv http://www.telegazeta.com/wp-content/plugins/img/eyog.html o3jgtyj9m=2C ixozyzgz5c. bua83i0f2l 1e694c6ehk1j 39g0sfdlllc. ________________________________ Message 10 ____________________________________ Time: 01:32:26 PM PST US From: Harley Subject: Re: AeroElectric-List: l5t06e 1ipfv Another one got through...don't click on it. Harley ----------------------------------------------------------------- > http://www.telegazeta.com/wp-content/plugins/img/eyog.html > o3jgtyj9m, ixozyzgz5c. bua83i0f2l 1e694c6ehk1j 39g0sfdlllc. > * > > * ________________________________ Message 11 ____________________________________ Time: 01:44:55 PM PST US From: RGent1224@aol.com Subject: Re: AeroElectric-List: l5t06e 1ipfv YOU BETCHA In a message dated 7/22/2011 3:33:12 P.M. Central Daylight Time, harley@AgelessWings.com writes: Another one got through...don't click on it. Harley ____________________________________ _http://www.telegazeta.com/wp-content/plugins/img/eyog.html_ (http://www.telegazeta.com/wp-content/plugins/img/eyog.html) o3jgtyj9m, ixozyzgz5c. bua83i0f2l 1e694c6ehk1j 39g0sfdlllc. (http://www.matronics.com/Navigator?AeroElectric-List) (http://www.matronics.com/contribution) ________________________________ Message 12 ____________________________________ Time: 03:22:18 PM PST US From: Vincent Welch Subject: RE: AeroElectric-List: l5t06e 1ipfv This did not come from me. Something has attacked my hotmail account and i s sending to everyone on my contact list. From: harley@agelesswings.com CC: welchvincent@hotmail.com Subject: Re: AeroElectric-List: l5t06e 1ipfv Another one got through...don't click on it. Harley http://www.telegazeta.com/wp-content/plugins/img/eyog.html o3jgtyj9m=2C ixozyzgz5c. bua83i0f2l 1e694c6ehk1j 39g0sfdlllc. ________________________________ Message 13 ____________________________________ Time: 03:32:20 PM PST US From: Harley Subject: Re: AeroElectric-List: l5t06e 1ipfv I suspected that your email was probably just spoofed, just wanted to warn others. It's happened to me a couple of times, and if you just wait it out, it'll probably go away in a few days. If you're password still works on your account, then it's probably not hijacked...someone just "temporarily borrowed" your address by putting it in their own "From" line. If that's the case, your account is not in any danger. If you start getting a bunch of returned emails with "address ubnknown" on them, that's definitely the case...it'll go away eventually. Harley ----------------------------------------------------------------- On 7/22/2011 6:18 PM, Vincent Welch wrote: > This did not come from me. Something has attacked my hotmail > account and is sending to everyone on my contact list. > > ----------------------------------------------------------------- > Date: Fri, 22 Jul 2011 16:29:54 -0400 > From: harley@agelesswings.com > To: aeroelectric-list@matronics.com > CC: welchvincent@hotmail.com > Subject: Re: AeroElectric-List: l5t06e 1ipfv > > Another one got through...don't click on it. > > Harley > ----------------------------------------------------------------- > > http://www.telegazeta.com/wp-content/plugins/img/eyog.html > o3jgtyj9m, ixozyzgz5c. bua83i0f2l 1e694c6ehk1j 39g0sfdlllc. > > * > > * > ------------------------------------------------------------------------------------- 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.