Today's Message Index:
----------------------
1. 07:03 AM - Pre-oiler system controls (Robert L. Nuckolls, III)
2. 07:06 AM - Re: Intermittent power supply issue (Robert L. Nuckolls, III)
3. 09:57 AM - Re: Question (Robert L. Nuckolls, III)
4. 10:44 AM - Re: Intermittent power supply issue (user9253)
5. 11:22 AM - Re: radio noise (user9253)
6. 02:10 PM - bearing failure resulting from current flow (Christopher Cee Stone)
7. 05:03 PM - Re: Contactor clicks but doesn't make electrical contact (Robert L. Nuckolls, III)
8. 05:03 PM - Re: bearing failure resulting from current flow (Robert L. Nuckolls, III)
Message 1
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| Subject: | Pre-oiler system controls |
At 02:24 PM 5/7/2013, you wrote:
Bob,
I have your book and perused your web-site. I have a simple question
concerning controlling a pre-oiler Accusump accumulator and an oil
pressure pump with the same switch. Both electric obviously.
The Accusump is an oil pressure accumulator plumbed into the high
pressure oil system and controlled by an electric on/off
valve. Before engine start, you open the valve, the accumulator
discharges and the engine is pre-oiled with a squirt of high pressure
oil. The valve is left open during flight to provide oil pressure
during transient fluctuations. Before engine shutdown, the valve is
closed by removing power, trapping oil pressure in the
accumulator. This system is on my aircraft and controlled by a
simple on/off switch.
I am planning on adding an electric oil pressure pump to this
system. The pump will receive supply from the engine sump, and
pressurize the same feed/return line that the Accusump is connected
to. A check valve will prevent high pressure oil inadvertently
recirculating back into the sump. The purpose of the pump is two
fold: the accumulator tends to bleed down over time, and curious
fingers tend to deplete my accumulator (oops, what does this switch do?)
I've heard various forms of 'pre oiler systems' over
the years. I wondering why you're sacrificing empty
weight to carry both the accumulator and the pump.
The accumulator is like a battery . . . it's capability
is limited by size . . . one shot and it's empty.
The pump is like an alternator. As long as it's supplied
with power, it's capability to circulate oil is virtually
unlimited. What is the advantage to be secured by having
both devices on the airplane? You need a source of power
to open the accumulator valve -OR- to run the motor. I'm
having trouble grasping the value of having both systems
on the airplane.
My switch control plan is to use a three position switch - off on (on)
Off - bottom position - no power to Accusump valve or oil pump.
On - middle position - only power to Accusump to open valve.
On (momentary) - up position - power to both Accusump valve AND oil pump.
Is it possible to wire a switch this way?
Yes, you would need to acquire a two-pole, three-position,
progressive transfer switch with momentary operation in one
position. An exemplar switch is the Honeywell 2TL1-50 switch
that can be procured here:
http://tinyurl.com/btfd4e9
Here's a link to the specification sheet.
http://tinyurl.com/d2vkuvx
Obviously wiring is not my strong suit, and I cannot figure out what
switch to use and how to wire it. Any help and advise you can give
will be greatly appreciated.
The progressive transfer mechanism combined with
spring loading of full up position provides the functionality
your looking for. But I recommend you re-consider burdening
your airplane's empty weight with the accumulator which seems
to be of limited value when combined with the pump.
Bob . . .
Message 2
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| Subject: | Re: Intermittent power supply issue |
At 03:41 PM 5/7/2013, you wrote:
>I have a Long-EZ with the Z13 11/01 architecture.
>It has been running fine for 5 years but now an intermittent power
>supply issue has arisen.
>The Garmin 530 and GTX 330 run off the endurance bus and have been
>going offline recently: the transponder more frequently but the 530
>nav/com/gps has the "power off" screen come up and then power seems
>to reestablish itself and then all is fine with the radio for a while.
>The VMS1000 engine instrumentation display also comes off this bus
>and the volt sense has recently been showing 12.7 to 13.7 volts.
>Bypassing the bridge rectifier now has the voltage showing 15.1 to
>15.4 volts and then flashes the volts display.
>I am about to go through the LR3C troubleshooting guide, but
>wondered if anyone has any bright ideas as to what may be occurring?
>Patrick Elliott, England. G-LGEZ.
First, a reading over 14.6 on the system is TOO HIGH.
Adjust the LR-3 regulator DOWN until a normal main bus
voltage of 14.6 is achieved.
A bridge rectifier doesn't go 'intermittent' . . . further,
closing the alternate feed switch is equivalent to bypassing
the rectifier. After re-adjustment of the regulator, see
if the intermittent condition goes away with the alternate
feedpath switch closed. You're looking for a lose connection
of some variety . . . but fix that voltage first.
Bob . . .
Message 3
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>
>So there it is, that 9 and 13 are grounds,
>running to the same AMP connector. This is what
>I was asking. Why are there 2 independent wires
>which end up going to the same AMP connector
>with 30 some pins on it that are all grounded together?
>
>Then in the bottom diagram for a PS Engineering
>marker beacon, pin 9 is the power ground and pin
>14 is the audio ground. So am I correct in
>assuming that they also end up at the same 30
>some pin AMP connector ' since the SL-30 pins
>for power ground and audio ground both end up there?
I cannot know the reasoning behind any particular
design decision unless it is specifically explained
in the manufacturer's documents. I can attest to the
my notion (shared by some) that many products miss
an opportunity to make a device easier to install
by making otherwise unneeded pins extra grounds.
This gives the installer an opportunity to neatly
terminate pigtails for shields on their own pin
in the connector. I have generated two widely
used, multiple connection grounding products. One
is the firewall ground bus sold by B&C, the other
is the panel/avionics ground bus offered on my
website. There are no specific assignments for
where connections are made on these products. My
architecture drawings feature ground symbols labeled
so as to suggest termination at a specific ground
bus . . . but not on any particular pin.
I am always pleased to see manufacturer's wiring
diagrams that offer dedicated ground pins for all wires
needing ground . . . but sometimes, it's simply
not possible to have plenty of grounds for all
contingencies.
There is nothing 'magic' about a proliferation
of grounds in any given connector.
Bob . . .
Message 4
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| Subject: | Re: Intermittent power supply issue |
9 times out of 10, electrical problems are caused by bad connections. I suggest
taking apart every connection in the circuit, making sure the mating surfaces
are clean, tugging on crimped terminals, and then reassembling everything.
Depending on the circuit, a bad connection(s) to the voltage regulator sense terminal
can cause high voltage or voltage fluctuations.
When problems are intermittent, a bad connection is the first suspect.
Joe
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=400152#400152
Message 5
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I agree with the others that it is a squelch problem.
On the top my Icom ic-A200 are 3 foil stickers each about 1/2" diameter which cover
pot access holes. The A200 top cover is lightly embossed with hard to see
labels for each of the 3 holes. The squelch is labeled SQL.
Joe
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=400154#400154
Message 6
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| Subject: | bearing failure resulting from current flow |
This topic was discussed here earlier this week. The following adds to
Bob's description of bearing failure due to a small current flow through
the bearing.
I have no commercial interest in any of the companies mentioned.
Chris Stone
Preventing Discharge Damage: Conductive Rolling Bearing Greases
Wed, 05/08/2013 - 2:23pm
Heiko Stache, Manager Business Unit =93 Bearing Technology & Sabine
Petri,
Product Manager, Kl=C3=BCber Lubrication
Get today's manufacturing headlines and news - Sign up
now!<http://subscribe.advantagemedia.com/mnet_ods/landing.aspx?cmpid=text
adincontent>
*Conductive rolling bearing greases provide inexpensive and efficient
solutions.*
Whether in the plastics, textile or motion control industries, damage
caused by electric discharge is a well-known issue, and today it is more
prevalent than ever. It primarily affects rolling bearings in machines
susceptible to static charging. In many cases, conductive grease made
especially for these applications can provide an inexpensive and efficient
solution to this problem, while at the same time ensuring optimum rolling
bearing lubrication.
Static charges may have a variety of causes. In film stretchers, for
example, plastic material is conveyed on steel rollers, leading to
electrostatic charging. In tumble drier drums, the plastic content of the
laundry, such as nylon, may be the cause. Rolling bearings operating under
high loads have a particularly high risk of damage, since there is
frequently partial direct contact between the rolling elements and the
raceways, leading to sudden discharge, not unlike an electric arc. As the
metal-to-metal contact is restricted to a very small area, even currents
well below 1 ampere can cause the contact points to weld or fuse together.
Typical discharge damage is in the form of plates, craters or grooves on
the bearing.
The cause of the damage is a voltage applied to the bearing, which can be
of three different types:
- Shaft voltage (AC voltage): the shaft is rotating in an asymmetrical
magnetic field and, therefore, induction takes place.
- Unipolar voltage (constant or pulsating DC voltage): the shaft is
rotating and is itself magnetic, giving rise to an inductive effect.
- Extraneous voltage (DC or AC voltage): in this case, the shaft is
charged from the outside =93 e.g., from electric control systems,
track
currents, welding currents or electrostatically, =93 due to proces
s media,
lubricants or coolants.
Craters are the result when surface melting takes place on raceways due to
electric potential. Molten metal particles may also be carried off and
deposited on the raceway, where they are rolled down. Grooves form when
current flows while the rolling elements and the raceways are under load.
This causes the rolling elements to vibrate and, over time, typical grooves
form on the inner and/or outer ring. Repairing such damage takes a lot of
time and money =93 in extreme cases, the bearing as a whole has to be
replaced. The severity of the damage depends on a number of factors, such
as current intensity, time of exposure, bearing load, speed and lubricant
used.
Message 7
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| Subject: | Re: Contactor clicks but doesn't make electrical |
contact
At 08:51 AM 3/25/2013, you wrote:
<mrspudandcompany@verizon.net>
Bob,
Re: the contactor that we were discussing a week or two ago. I
believe that it is the original assembly in a C177B.
I removed it yesterday and replaced with a 3 terminal, same as was
originally installed, unit and it works perfectly.
The junk item went in the mail this AM, so you should have it in a
couple of days. It will be interesting to find out what you observe
as the failure when you tear it down.
Thanks for what you do!
Roger
Thanks for sending me the carcass. I've disassembled the
remains. The failure mode in this case is quite clear
and consistent with your narrative for intermittent
functionality. The photos at
http://tinyurl.com/cp4xkv3
http://tinyurl.com/d95qhst
http://tinyurl.com/bwqxm5v
http://tinyurl.com/bocgcaa
. . . show effects of selective corrosion.
The next photo http://tinyurl.com/butbm2m shows that
all conduction surfaces are bright and clean having
been properly torqued for gas-tightness. External
joints on wires brought to the contactor were
properly installed and not contributors to this failure.
This photo of contactor ring http://tinyurl.com/cm4ncou
suggests that the ring was free to rotate as evidenced
by the relative uniformity of the oxidation pattern
in the contact area.
The obverse side of the contactor ring http://tinyurl.com/d8pgygg
shows no evidence of localized heating. The c-clip that retains
the closure pressure ring shows evidence of localized corrosion.
http://tinyurl.com/bu3paoo here we see the opening spring
is uniformly rusted. http://tinyurl.com/d6wo24e The rust
is finely grained and easily transfers to the touch.
The drain hole in the contactor cap is open and clean. The inside
surface of the cap http://tinyurl.com/c6fk5kh shows evidence
of moisture pooling.
The outside surface of the cap http://tinyurl.com/cn8t7rl shows
evidence of condensation drip down the outside surface that
concentrated as surface wetness.
This is a good example of a 'soft' failure. The corrosion
patterns suggest mild effects over a very long period
of time. Concentrations and locations suggest the contactor
had been properly installed with the drip-hole down.
The intermittent nature of the malfunction suggests that
rust-dust off the spring would fall onto the upper side
of the contactor ring and provide a poor to no-conductivity
contaminant that would prevent the ring from making good
connection with the terminals. That when contact was good,
any dust in the gap would fuse to become part of the
discoloration on the contactor ring . . . which was free
to rotate and bring a less-contaminated area into service.
This failure was a very slow progressing event promoted
by years of normally deposited condensate. Condensate that
would occasionally produce low-point concentrations
of moisture on the end of the armature, upper inside
surface of the cap, and on the lower outside surface
of the cap.
Given that the failure was not gross and catastrophic,
it appears that everything was functioning to design
goals and that the contactor had simply reached the
end of service life for the conditions under which
it operated.
Bob . . .
Message 8
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| Subject: | Re: bearing failure resulting from current flow |
At 03:52 PM 5/8/2013, you wrote:
>This topic was discussed here earlier this week.
>=C2 The following adds to Bob's description of
>bearing failure due to a small current flow through the bearing.
Good data Chris . . . thank you.
Bob . . .
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