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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Subject: | Re: Questions on avionics |
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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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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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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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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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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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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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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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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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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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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Subject: | Re: Rear Mounted Batteries - more questions |
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
"Fools" 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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