AeroElectric-List Digest Archive

Wed 04/16/08


Total Messages Posted: 11



Today's Message Index:
----------------------
 
     1. 04:30 AM - Re: Questions on avionics (rampil)
     2. 07:57 AM - Grommets (Jeff Page)
     3. 08:32 AM - Re: Grommets (Ernest Christley)
     4. 08:57 AM - Re: Grommets (Bill Boyd)
     5. 09:04 AM - Voltage Drop in DM15-14 Dimmer (Danny Smith)
     6. 09:20 AM - Re: Grommets (Rob Housman)
     7. 09:21 AM - Re: Grommets ()
     8. 09:53 AM - Re: Grommets (Ernest Christley)
     9. 02:17 PM - Re: Voltage Drop in DM15-14 Dimmer (Robert L. Nuckolls, III)
    10. 02:43 PM - Ground Power - Z31A (Emond)
    11. 03:00 PM - Re: Rear Mounted Batteries - more questions (n277dl)
 
 
 


Message 1


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    Time: 04:30:41 AM PST US
    Subject: Re: Questions on avionics
    From: "rampil" <ira.rampil@gmail.com>
    Re: TSO and altimetry sources There is no requirement for TSO in owner built aircraft. As I said previously, there is only a performance requirement. Part 23 is a separate issue. -------- Ira N224XS Read this topic online here: http://forums.matronics.com/viewtopic.php?p=177151#177151


    Message 2


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    Time: 07:57:02 AM PST US
    From: Jeff Page <jpx@Qenesis.com>
    Subject: Grommets
    I was surprised to find halves of grommets lying on the floor of my hangar the other day. In January, they were installed in the leading edge ribs. It has been too cold here in Toronto to do much work on my plane since then. As far as I can tell, the holes in the aluminum ribs shrunk from the cold and cut the grommets in half. I am glad I found this out before pulling all the wires through ! The holes were drilled a hair smaller than the grommets, which fit nicely without bunching up. The holes were carefully deburred and I can rotate my finger in the holes without feeling a sharp edge. The grommets I purchased from Spaenaur rather than the local hardware store. They are specd as material: SBR, hardness: 60 durometer +/-5. Are these grommets the wrong material ? Should there be slack around the grommet when fitted in the hole ? Some other problem I haven't thought of ? Thanks, Jeff Page Dream Aircraft Tundra #10


    Message 3


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    Time: 08:32:50 AM PST US
    From: Ernest Christley <echristley@nc.rr.com>
    Subject: Re: Grommets
    Jeff Page wrote: > > I was surprised to find halves of grommets lying on the floor of my > hangar the other day. In January, they were installed in the leading > edge ribs. It has been too cold here in Toronto to do much work on my > plane since then. > > As far as I can tell, the holes in the aluminum ribs shrunk from the > cold and cut the grommets in half. I am glad I found this out before > pulling all the wires through ! > > The holes were drilled a hair smaller than the grommets, which fit > nicely without bunching up. The holes were carefully deburred and I > can rotate my finger in the holes without feeling a sharp edge. > > The grommets I purchased from Spaenaur rather than the local hardware > store. They are specd as material: SBR, hardness: 60 durometer +/-5. > > Are these grommets the wrong material ? > That would be my guess. If it was too cold to work on the plane and you believe the aluminum shrunk, then the grommet were possibly as brittle as glass. One of the techniques for manufacturing rubber bushings is to freeze them and then machine them like metal. They got nice and brittle (but probably didn't shrink much), and then the aluminum closed in on them. Probably happened several times. Try keeping a 60W lightbulb turned on in the plane.


    Message 4


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    Time: 08:57:06 AM PST US
    From: "Bill Boyd" <sportav8r@gmail.com>
    Subject: Re: Grommets
    60W light bulb isn't going to help much at altitude. It gets COLD up there. I'd suggest a re-do with looser holes or different material. Just my $.02 -Bill B On Wed, Apr 16, 2008 at 11:27 AM, Ernest Christley <echristley@nc.rr.com> wrote: > echristley@nc.rr.com> > > Jeff Page wrote: > > > > > I was surprised to find halves of grommets lying on the floor of my > > hangar the other day. In January, they were installed in the leading edge > > ribs. It has been too cold here in Toronto to do much work on my plane > > since then. > > > > As far as I can tell, the holes in the aluminum ribs shrunk from the > > cold and cut the grommets in half. I am glad I found this out before > > pulling all the wires through ! > > > > The holes were drilled a hair smaller than the grommets, which fit > > nicely without bunching up. The holes were carefully deburred and I can > > rotate my finger in the holes without feeling a sharp edge. > > > > The grommets I purchased from Spaenaur rather than the local hardware > > store. They are specd as material: SBR, hardness: 60 durometer +/-5. > > > > Are these grommets the wrong material ? > > > > That would be my guess. If it was too cold to work on the plane and > you believe the aluminum shrunk, then the grommet were possibly as brittle > as glass. One of the techniques for manufacturing rubber bushings is to > freeze them and then machine them like metal. They got nice and brittle > (but probably didn't shrink much), and then the aluminum closed in on them. > Probably happened several times. > > Try keeping a 60W lightbulb turned on in the plane. > >


    Message 5


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    Time: 09:04:09 AM PST US
    From: "Danny Smith" <dsmit132@bellsouth.net>
    Subject: Voltage Drop in DM15-14 Dimmer
    I have the DM15-14 dimmer with only a Garmin GMA-340, TT ADI and a 3 ft LED strip (.086amp) attached to it. When I turned on the LED strip it didn't seem very bright so I checked the voltage and found that with an input to the dimmer of 12.7 V the output was only 9.7 V. Is a 3 V drop to be expected or is the dimmer module defective? Danny


    Message 6


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    Time: 09:20:10 AM PST US
    From: "Rob Housman" <rob@hyperion-ef.com>
    Subject: Grommets
    While not disputing that the grommets failed, I must question your explanation. The coefficient of thermal expansion for aluminum alloy 3003 (a common sheet alloy) is 12.9 microinch/inch deg F, so doing the math for a 1 inch diameter hole and a temperature change from a really hot 100 deg F day for installation and a really cold minus 50 deg F day during the winter you get a worst case diameter change of slightly less than .002 inch. A half inch diameter hole would change less than .001 inch for the same temperature change. Installing the grommets into an undersize hole, thus stressing the grommet, is probably the culprit, not contraction alone. Best regards, Rob Housman Irvine, CA Europa XS Tri-Gear A070 Airframe complete -----Original Message----- From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Jeff Page Sent: Wednesday, April 16, 2008 7:53 AM Subject: AeroElectric-List: Grommets I was surprised to find halves of grommets lying on the floor of my hangar the other day. In January, they were installed in the leading edge ribs. It has been too cold here in Toronto to do much work on my plane since then. As far as I can tell, the holes in the aluminum ribs shrunk from the cold and cut the grommets in half. I am glad I found this out before pulling all the wires through ! The holes were drilled a hair smaller than the grommets, which fit nicely without bunching up. The holes were carefully deburred and I can rotate my finger in the holes without feeling a sharp edge. The grommets I purchased from Spaenaur rather than the local hardware store. They are specd as material: SBR, hardness: 60 durometer +/-5. Are these grommets the wrong material ? Should there be slack around the grommet when fitted in the hole ? Some other problem I haven't thought of ? Thanks, Jeff Page Dream Aircraft Tundra #10


    Message 7


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    Time: 09:21:58 AM PST US
    From: <Flagstone@cox.net>
    Subject: Re: Grommets
    Jeff: Your finding has me concerned. Could you provide the following details: 1 Grommet Dimensions or Spaenaur part #: Inside Diameter Groove Diameter Outside Diameter Groove Width Overall Thickness 2 Hole Diameter 3 Rib thickness Were the wires in conduit? If so what was the outside diameter of the conduit. Do you have a pic of the installed grommet and the split grommet you can post? Thanks Mark ----- Original Message ----- From: "Jeff Page" <jpx@Qenesis.com> Sent: Wednesday, April 16, 2008 7:52 AM Subject: AeroElectric-List: Grommets > > I was surprised to find halves of grommets lying on the floor of my > hangar the other day. In January, they were installed in the leading > edge ribs. It has been too cold here in Toronto to do much work on my > plane since then. > > As far as I can tell, the holes in the aluminum ribs shrunk from the cold > and cut the grommets in half. I am glad I found this out before pulling > all the wires through ! > > The holes were drilled a hair smaller than the grommets, which fit nicely > without bunching up. The holes were carefully deburred and I can rotate > my finger in the holes without feeling a sharp edge. > > The grommets I purchased from Spaenaur rather than the local hardware > store. They are specd as material: SBR, hardness: 60 durometer +/-5. > > Are these grommets the wrong material ? > > Should there be slack around the grommet when fitted in the hole ? > > Some other problem I haven't thought of ? > > Thanks, > > Jeff Page > Dream Aircraft Tundra #10 > > >


    Message 8


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    Time: 09:53:23 AM PST US
    From: Ernest Christley <echristley@nc.rr.com>
    Subject: Re: Grommets
    Bill Boyd wrote: > 60W light bulb isn't going to help much at altitude. It gets COLD up > there. I'd suggest a re-do with looser holes or different material. Just > my $.02 > > OK. A 120W bulb.....and a really long drop cord. 8*)


    Message 9


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    Time: 02:17:50 PM PST US
    From: "Robert L. Nuckolls, III" <nuckolls.bob@cox.net>
    Subject: Re: Voltage Drop in DM15-14 Dimmer
    At 11:01 AM 4/16/2008 -0500, you wrote: ><dsmit132@bellsouth.net> > >I have the DM15-14 dimmer with only a Garmin GMA-340, TT ADI and a 3 ft LED >strip (.086amp) attached to it. >When I turned on the LED strip it didn't seem very bright so I checked the >voltage and found that with an >input to the dimmer of 12.7 V the output was only 9.7 V. Is a 3 V drop to be >expected or is the dimmer >module defective? It's probably okay. The regulator used in those dimmers is one of the LM317 series devices. You can get the data sheet at: http://cache.national.com/ds/LM/LM117.pdf the figure on page 6 labeled "Dropout Votlage" tells us that the minimum input-output differential can be as high as 2.0 volts depending on load. I had a number of folks question the voltage drop at max intensity settings . . . if it's a valid concern, there are other devices that offer reduced overhead maximums. When I designed those dimmers, the goal was (1) provide control of virtually any size illumination load by means of a small, panel friendly control potentiometer and (2) offer good voltage regulation such that bus voltage perturbations didn't show up in the panel lighting. An ancillary consideration was that 98+ percent of dimmer operations were at very low output settings . . . on the order of 4-6 volts. The duration of flight time where visibility of the illuminated objects would be enhanced by raising the dimmer from say 11 to 14 volts is a very few minutes during the day-night transition. Hence, limiting maximum output to 2 volts or so below bus voltage was not a big deal. Bob . . . ----------------------------------------) ( . . . a long habit of not thinking ) ( a thing wrong, gives it a superficial ) ( appearance of being right . . . ) ( ) ( -Thomas Paine 1776- ) ----------------------------------------


    Message 10


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    Time: 02:43:53 PM PST US
    From: "Emond" <d_emond@mweb.co.za>
    Subject: Ground Power - Z31A
    Bob Please can you confirm the correct procedure for using the ground power on Z31a architecture. Is it imperative to first switch on the "ground power" switch, before switching on the master switch? Would I just switch ground power off, once the aircraft has started? What would happen if ground power switch was inadvertantly left on for an indefinite period, or turned on whilst the aircraft engine was running? Your assistance as always is appreciated. Dave Emond RV10


    Message 11


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    Time: 03:00:24 PM PST US
    Subject: Re: Rear Mounted Batteries - more questions
    From: "n277dl" <dljinia@yahoo.com>
    Bob and list, Using the previously attached document as reference... Assumptions... rear mounted batteries. Main Bat Cntctr, Aux Bat cntctr and Xfeed Cntctr all mounted in rear beside the batteries. 2awg ground wire to fwd central gnd bus attached to the engine via stud through firewall. XFEED cnctr closed for starting. 2AWG wire from the same side of XFEED cntctr that the main bat cntctr is connected to starter cntctr. Questions.... Can I then run appropriate sized wire (tbd) from the same side of the starter cntctr as the 2awg wire is attached to the main pwr bus? If so, I also assume I would run appropriate sized wire ~8-10 awg (but not the heavy 2awg) from aux bat side of the XFEED to the Aux bus and use same wire to from the aux alt (prob 8 amp b&C alternator). Hope this makes sense. Really just trying to understand if I can only run two fat wires from the batteries to the firewall if I want to ground at the firewall or need to pull the extra "hot fat wire". thanks. Doug -------- Doug &quot;Fools&quot; are always more creative than process people and will always find ways to ruin a perfectly good set of processes. Read this topic online here: http://forums.matronics.com/viewtopic.php?p=177275#177275




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