Today's Message Index:
----------------------
1. 04:47 AM - Re: z-14 ? (Robert L. Nuckolls, III)
2. 05:22 AM - Re: Engine ground on RV 10 (Robert L. Nuckolls, III)
3. 07:52 AM - Pitot Heat (Neal George)
4. 08:10 AM - Re: Pitot Heat (Ralph E. Capen)
5. 08:43 AM - Re: Pitot Heat (Ron Quillin)
6. 08:47 AM - Potential Exp Load Center Failure Mode (Ed Anderson)
7. 10:06 AM - Re: Revision 12 Z Figures (Jeff Page)
8. 12:26 PM - Re: Engine ground on RV 10 (rparigor@SUFFOLK.LIB.NY.US)
9. 02:26 PM - Two speed trim contoller (Stan Blanton)
10. 03:04 PM - Re: Two speed trim contoller (Bob-tcw)
11. 03:11 PM - Re: Engine ground on RV 10 (Robert L. Nuckolls, III)
12. 03:37 PM - Re: Engine ground on RV 10 redux (Robert L. Nuckolls, III)
13. 05:03 PM - Re: Engine ground on RV 10 (Bill Mauledriver Watson)
14. 07:56 PM - Re: Engine ground on RV 10 (Robert L. Nuckolls, III)
Message 1
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At 06:13 PM 2/11/2009, you wrote:
>
>Bob thanks for the Z-33 that shows duel power to contactors. This
>has lead to another question. I have S701-1 type contactors as shown
>in Z-14. My contactors only have one small stud that closes the
>contactor when grounded Can these be wired for duel power sources
>or do I need to replace them with S701-2 type contactors. . Thanks Tim
The only difference between a 701-1 and 701-2 is how the diodes
are installed. You can remove the jumper wire on a -1 and add
two diodes to convert it to a -2. The only time you would need to
replace the contactor is if you had purchased a 3-terminal device
common to other suppliers of battery contactors.
Bob . . .
----------------------------------------)
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
----------------------------------------
Message 2
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| Subject: | Engine ground on RV 10 |
At 02:06 PM 2/11/2009, you wrote:
>
>Bob Nuckolls,
>
>You said below that stainless firewall sheet is not a GOOD conductor.
>Will you please quantify that statement? How much worse is it than
>2024-T3 aluminum?
>
>I have a battery in the tail of my airplane that is grounded through the
>airframe, but the forest of ground tabs is on the stainless steel
>firewall. Does that mean that I need to run a fat wire from the forest
>of tabs attach bolt on the stainless steel firewall to some portion of
>the aluminum airframe?
It wouldn't hurt.
The simple answer to your question is that stainless steels are
between 10 and 30% as good a conductor of electron flow as
annealed copper. That sounds worse than it is in this case
because we're not dealing with a long, thin conductor between
point A (your battery ground) and point B (your forest-of-tabs).
Imagine if you will 1,000,000 conductors between A and B. Each conductor
is made of aluminum (A-to edge of firewall) where a piece of
stainless wire is spliced on (edge of firewall to B). While the
addition of the stainless might make the over all path resistance
of any one conductor jump by a factor of 3 to perhaps even
10x, the PARALLELED value of all those conductors is still
a rather low number.
As an example, I think I heard a number offered in a meeting
on lightning issues that the resistance of a Model 400 Beechjet
from nose to tail was on the order of 1 milliohm. Pretty low
as far as cranking engines was concerned (assuming that you
ran cranking current the length of the airplane!). In terms
of 100,000 amp lightning strikes, that 1 milliohm was quite
significant for other concerns.
If you visualize your point A to point B conduction pathway
as a wire frame made up of many paralleled paths of connected
airframe components, the whole thing is still pretty good
(with "pretty" being "terribly" non-quantified . . . terribly
isn't well quantified either).
The point is that while the stainless steel as a single entity
in a huge array of entities doesn't cause the cranking current
pathway to become useless. The concerns come with ageing
of the airframe where new rivets that were swelled up in tight
holes become less conductive with time in service and
environmental effects.
It would be interesting to get a conductivity measurement
between the center of the firewall sheet and the battery (-)
terminal of your airplane before and after adding a
fat-wire jumper. I did have occasion to measure the
battery(-) to crankcase resistance on a wrecked 172. See
http://www.aeroelectric.com/articles/grnding.pdf
Even in the bent state, the resistance was just
under 3 milliohms. Know too that the majority
of that resistance came from wire and joints in
wires use to complete the chain. The airframe
would have been a small fraction of the total.
If this sounds like an indefinite answer as to the
value of adding the jumper wire, you're right. Your
brand new airplane as-assembled will probably not
show the effects of less-than-the-best grounding.
But as a matter of experience and good practice let
me offer that I try to avoid using the firewall sheet
(indeed other parts of the airframe) as the universal
ground conductor.
This is discussed in the 'Connection and in Figure Z-15.
Adding the jumper now and then using the airframe for
grounding ONLY a few remote accessories is a good
thing to do for the owner-operator that's going to
be flying this airplane 20 years from now . . . hopefully
that's you.
Bob . . .
Message 3
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Bob -
I have an AN5814-1 heated pitot-static tube. This monster draws over
20-amps at turn-on, and settles down around 12-amps or so. How would you
recommend I feed it?
Fat breaker on the panel?
S704-1 relay?
Something else?
neal
Message 4
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I have a fuse on mine - 30 I think....looks like you're considering the switch
too based on your possible use of a relay.
Ralph
RV6A N822AR @ N06 3.7 hrs....
-----Original Message-----
>From: Neal George <n8zg@mchsi.com>
>Sent: Feb 12, 2009 10:49 AM
>To: aeroelectric-list@matronics.com
>Subject: AeroElectric-List: Pitot Heat
>
>
>Bob -
>
>I have an AN5814-1 heated pitot-static tube. This monster draws over
>20-amps at turn-on, and settles down around 12-amps or so. How would you
>recommend I feed it?
>
>Fat breaker on the panel?
>S704-1 relay?
>Something else?
>
>neal
>
>
Message 5
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At 07:49 2/12/2009, you wrote:
>I have an AN5814-1 heated pitot-static tube. This monster draws over
>20-amps at turn-on, and settles down around 12-amps or so. How would you
>recommend I feed it?
Just as a point of reference, we have the same PS tube in a certified AC.
It's fed through a 20A breaker and a Carling rocker switch with faston tabs.
No problems so far.
It will be 36 years this August.
Ron Q.
Message 6
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| Subject: | Potential Exp Load Center Failure Mode |
A potential Damage mode of the EXP2 Load Center.
PROBLEM
Recently a couple of friends of mine flew an RV that had been purchased,
from Texas back to NC. The RV had been checked by an RV "broker" and seemed
to be Ok short of having a dead battery. The battery was replaced and the
next morning and my two friends launched into what was to become a nerve
racking flight. Getting up the next morning to start their return trip,
they discovered that the new battery was dead and would not crank the
aircraft. The alternator was functioning OK and reducing electrical load to
the minimum they decided to continue the trip (with jump starts at every
stop) until arriving safely.
Having a bit of experience with electrical systems, I was asked to take a
look at the problem. The aircraft had an EXP2, a load center with toggle
switches installed. I was not familiar with the unit, but after getting the
schematic for the wiring of the EXP2 board, the first thing I notice was
that the Master relay on the board was missing and the socket holes taped
over with masking tape - which I though rather odd. Reading the
specifications, I discovered the relay could be replaced with a special
jumper (as explained later - it has to be this special jumper - a plain wire
jumper will not work) in event an external master contactor was used, but
the manufacture's jumper was not present either.
I found that even with the relay missing and no jumper present in the relay
socket and the Master Switch OFF that there was still continuity between
the alternator and battery terminals on the EXP2 board - again, I though
that rather odd. More on why this continuity later.
CURRENT OVERLOAD
To make a long story short, upon further examination, it was apparent that
the EXP2 board had encountered a heavy current overload at some point. This
overload apparently not only fried the on-board relay but did cause the
copper leads on the EXP2 board to become hot enough for the solder coating
to melt and run off of some of the copper leads. When the board was removed
it became clear that someone had solder a heavy strip on the underside of
the board to complete a circuit between alternator and battery across the
relay socket terminals - apparently in attempt to jump the damaged relay
position.
INEFFECTIVE REPARE ATTEMPT
However, that specific attempt at repair kept the battery terminal on the
EXP2 board connected to EXP2 board Alternator terminal at all times - even
when the master switch was OFF. With a functioning on-board relay present,
the circuit between battery and alternator terminals on the EXP2 is broken
when the master switch is off. But, the jumper repair soldered across the
relay position maintained the contact between alternator and battery
terminals regardless of master switch position.
This electrical system had one external master solenoid. When this solenoid
is closed the battery circuit is completed to both the starter and to the
Exp2 Battery Terminal. IF the on-board relay (or manufacture's jumper) is
installed and the master switch is ON then the EXP2 on-board battery
terminal is also connected with the alternator terminal through the EXP2
board. If the external solenoid is open then only a no. 18 AGW wire
connects the hot side of the solenoid to the master switch on the board.
When this master switch is ON it grounds the external solenoid relay circuit
causing the external solenoid to close the high current path and connect the
battery to the rest of the system (including the alternator). Turning the
Master switch ON also clauses the on-board relay to close which is what
actually interconnects the battery and alternator terminals on the board.
EFFECT OF REPARE ATTEMPT
There appears to be two potential drain paths resulting from the makeshift
jumper across the on-board relay position. Shown in the broken red line on
the attached schematic, there was a low current (no. 18 wire) hot lead off
the battery side of the ext. solenoid to the Master Switch. When the Master
switch was turned on (grounded) - it completed the circuit to ground and
permitted current to flow through the solenoid coil closing the external
solenoid which then provided the high current direct path between battery
and alternator for heavy current flow. However, even when the Master Switch
was OFF (ungrounded) and the external solenoid open it appears there was
still a steady drain through this line to board and hence the alternator
(and any keep alive load fed from the board). This of course produced a
continuous battery drain with the engine off and master off.
This current drain (through the load resistance of the alternator and
board) after engine shut down may have been low enough to preclude
activating the external solenoid in which case it would take longer to drain
the battery. However if this drain (with the master off and ungrounded) was
sufficient, it may have kept the external solenoid close long enough to
drain most of the battery, before battery power fell too low for the flow to
keep the relay close in which case, it would open - but, drain would still
continue through the low current path shown by the dashed red through the
master switch circuit. Resulting in a dead battery.
I still have one puzzle- if the alternator and battery are always
connected on the board, I could see the drain over night, but why wouldn't
the battery get charged during flight - surely enough to turn the engine
over at the next stop? Well, I have a hypothesis I've posted at the end of
this e mail for you electrical types. I'd be interested in feed back on it
- or your viewpoint as to why the battery would not charge in flight. Thanks
in advance.
After tracing the rest of the aircraft electrical power system and finding
out it was wired according to the recommendations in the EXP2 manual, a new
EXP2 board was installed and everything functioned normally. Note. I
could not find any alternator fuse link - it may have been present, but no
extended search was made for it as it was clear there was continuity to the
alternator.
POSSIBLE CAUSE
In trying to figure out what had happened to cause the power surge and
looking at the EXP2 diagram, one possible scenario became clear. IF someone
left the master switch ON and then while replacing or messing around with
alternator, permitted the alternator "B" lead to become grounded, a circuit
(short) is completed from battery to ground with the EXP2 on-board relay in
between. The very high battery current flow would be from the battery
through the EXP2 board's relay and circuit board leads to the grounded "B"
lead. Certainly higher than the 40 amps rating of the on board relay and
apparently enough current to heat some of the copper leads on the EXP2 board
above the melting point of their solder coating.
It was equally clear that had the master switch been OFF which would have
had the on-board relay open (and no connection between battery and
alternator) that the grounding of the "B" lead would have been a non-event.
Naturally, I do not know for certain if this was what actually happened, but
it is clear that it easily could.
It is possible that if the repair jumper were removed and a new relay
installed that the old EXP2 board would have functioned properly, but given
the metal solder that flowed from the copper traces, I personally felt the
only prudent thing to do was to replace the entire board. The new owner
agreed and that is what was done. Who knows that effect that overstress
condition might have had on other components or the board itself.
I have no dogs in this fight and simply want to pass on to others using the
EXP2 about this possible failure mode - which may not necessarily be unique
to the EXP2. Given the nature and magnitude of the current Overload - one
could conclude that the EXP2 design is rather robust and damage tolerant. A
fuseable link between alternator and board may have helped - if it were not
rated at much more than 40 amps, otherwise a higher rated fuse link would
have still resulted in current flow exceeding the stated rating of the
on-board relay of 40 amps. My analysis may be incorrect - but the damage
was very real.
Naturally, detaching the battery is always the safest approach but not
always followed, but at least with the EXP2 make certain the Master switch
if OFF before messing with your alternator. There may be other scenarios
that could have caused this problem but that seem to be most probable.
Best Regards
Ed
Ed Anderson
Rv-6A N494BW Rotary Powered
Matthews, NC
eanderson@carolina.rr.com
<http://www.andersonee.com> http://www.andersonee.com
<http://www.dmack.net/mazda/index.html>
http://www.dmack.net/mazda/index.html
<http://www.flyrotary.com/> http://www.flyrotary.com/
<http://members.cox.net/rogersda/rotary/configs.htm>
http://members.cox.net/rogersda/rotary/configs.htm#N494BW
Addendum Hypothesis:
<http://www.dmack.net/mazda/index.html> Given the apparent connections with
the attempted jumper repair, I would have expected that the alternator would
at least keep the battery charged sufficiently to restart the engine after a
short refueling stop. However, this was not what the pilots ferring the
plane back experienced. They hand propped after one stop and got jump
starts at the remaining stops. But, still it would have seemed that with
the alternator charging that the battery would have been charged sufficient
for a start after a short stop even if it would be expected to drain down
overnight.
The only scenario I could come up with that might explain why the battery
never seems to receive a charge from the alternator follows:
Hypothesis. The external selonoid control all access to the battery with
the exception of one wire from the hot side of the selonoid which went to
the EXP2 board master switch. When the master switch was turned on
(grounded) this permitted current flow through the relay coil of the
external solnoid and close the high current path between battery and starter
and the rest of the electrical system including the alternator. In other
words, if this relay were open then there was no connection between
alternator and battery, if close then connection existed.
My though goes along these lines ( and I would like any input as to view as
to the plausability of this being correct or incorrect). IF only the
current flowling though the external solenoid maintained it closed and
permitted continunity with the altnerator throught the EXP2 board then
anything that resulted in decreased current flow could cause that relay to
open.
It appears that the current through the master switch is limited to that
flowing through the relay coil of the external solenoid provide by the
battery potential. It would appear that if through this repair jumper the
alternator voltage appeared on the master switch circuit that it would tend
to neutrailze or at least reduce the current flow. IF it did reduce it
below the hold down current required then the external solnoid would open
removing the battery from the electrical system including the alternator
while the engine was running.
While the engine is off or during starting - the alternator is not putting
out voltage therefore the battery potential holds the external selnoid
closed with the master switch closed. However, once the engine starts
running the altenrator potential comes on line and exceeds that of the
partially drained battery. IF the attempted repair resulted in the
alternator voltage appearing on that circuit and neutralizing the battery
poential to move current through the relay, its seems possible that the
external selnoid could open and remain open during alternator operation
preventing charging of the battery.
IF correct then you would have the worst of both worlds, the battery being
heavily drained by the starting current load and not being able to get any
recharge from the alternator and then would be drained down overnight I
admit, a wild stab in the dark, but the only one I could come up with.
Message 7
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| Subject: | Re: Revision 12 Z Figures |
Some possible updates to Z figures:
Z15K3p2
2nd paragraph, second line, change "Busses at" to "Busses are"
3rd paragraph, 5th line, "crancase" to "crankcase"
3rd paragraph, 6th line, "leas" to "least"
4th paragraph, 1st line, ""bee" to "been"
Z17 On diagram, label Dynamo as B&C SD-8 and regulator as B&C PMRIC-14
Z25 - Self-excitation components missing.
possibly show the SD-8 wires twisted ?
If you are intentionally deleting the self-excitation feature, delete
references to it in Z10-8A2 and Note 25.
If you want to promote the self-excitation feature, add reference to it
in Z16, Z17
Note 4 - Perhaps update the discussion here. When I read this the first time,
my impression was that I could choose a fuselink by selecting 4AWG smaller
than the wire to be protected. Discussions with you on this list indicated
that this was an over-simplification and that I should only use fuselinks
as shown in the Z diagrams. Perhaps additional discussion here to explain
some details, or some caution that additional learning is required to
select fuselink sizes.
Note 25. I have 1K, Z21A shows 3K resistor for SD-8 self-excitation.
Wish List:
I am particularly fond of Z13/8. As a step up, using Emagair
ignitions and an SD-8 aux alternator, I would suspect many builders
would also opt for B&C's
LR3C-14 regulator instead of the generic Ford regulator. Perhaps draw it that
way ?
With two electrically dependent ignitions, it seems to me the holy grail of
architectures would be completely isolated electrical systems as the only true
guarantee of no single fault causing disaster. Z14 is much more than
needed to
accomplish this goal. A major revision to Z13/8 would add a small
battery to go with the SD-8, feeding the second ignition from an
independent battery bus.
In the event of a main alternator failure, a cross-feed relay would allow the
SD-8 to feed the endurance bus. The aux battery would not be used to feed the
starter motor. If you believe this a worthy design goal, perhaps add
a drawing
to illustrate it ?
Jeff Page
Dream Aircraft Tundra #10
Message 8
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| Subject: | Engine ground on RV 10 |
Hi Bob
"The simple answer to your question is that
stainless steels are
> between 10 and 30% as good a conductor of
electron flow as
> annealed copper. "
Did you add
a decimal place stating between 10 and 30% and mean 1 and 3%??
According to this table:
http://www.ndt-ed.org/GeneralResources/MaterialProperties/ET/ET_matlprop_Iron-Based.htm
between 1 + 3% is more accurate??
Ron Parigoris
Just as a reference annealed copper is 100% and silver 106%:
http://www.wisetool.com/designation/cond.htm
Message 9
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| Subject: | Two speed trim contoller |
Bob,
Some time ago you published a schematic for a two speed trim controller.
Has that project ever been completed or should I try to fab one on my own?
The same question in regard to a basic mod of your dimmers to allow them to
be used in a similar fashion to control trim servo speedd.
Thanks,
Stan Blanton
RV-6
Extreme Slow Build
Message 10
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| Subject: | Re: Two speed trim contoller |
Stan, If you are interested in a pre-made product which includes two speed
trim control along with run-away trim prevention you may want to visit.
www.tcwtech.com
Thanks,
Bob Newman
TCW Technologies
----- Original Message -----
From: "Stan Blanton" <s.blanton@sbcglobal.net>
Sent: Thursday, February 12, 2009 5:22 PM
Subject: AeroElectric-List: Two speed trim contoller
> <s.blanton@sbcglobal.net>
>
> Bob,
>
> Some time ago you published a schematic for a two speed trim controller.
> Has that project ever been completed or should I try to fab one on my own?
>
> The same question in regard to a basic mod of your dimmers to allow them
> to
> be used in a similar fashion to control trim servo speedd.
>
> Thanks,
>
> Stan Blanton
> RV-6
> Extreme Slow Build
>
>
>
Message 11
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| Subject: | Engine ground on RV 10 |
At 02:23 PM 2/12/2009, you wrote:
>Hi Bob
>
>"The simple answer to your question is that stainless steels are
> > between 10 and 30% as good a conductor of electron flow as
> > annealed copper. "
>
>Did you add a decimal place stating between 10 and 30% and mean 1 and 3%??
>
>According to this table:
>
><http://www.ndt-ed.org/GeneralResources/MaterialProperties/ET/ET_matlprop_Iron-Based.htm>http://www.ndt-ed.org/GeneralResources/MaterialProperties/ET/ET_matlprop_Iron-Based.htm
>
>between 1 + 3% is more accurate??
Good eye! I tried to do conductance values to
percentages of resistance . . . Thanks!
Bob . . .
Message 12
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| Subject: | Engine ground on RV 10 redux |
>At 02:23 PM 2/12/2009, you wrote:
>>Hi Bob
>>
>>"The simple answer to your question is that stainless steels are
>> > between 10 and 30% as good a conductor of electron flow as
>> > annealed copper. "
>>
>>Did you add a decimal place stating between 10 and 30% and mean 1 and 3%??
>>
>>According to this table:
>>
>><http://www.ndt-ed.org/GeneralResources/MaterialProperties/ET/ET_matlprop_Iron-Based.htm>http://www.ndt-ed.org/GeneralResources/MaterialProperties/ET/ET_matlprop_Iron-Based.htm
>>
>>
>>between 1 + 3% is more accurate??
>
>
> Good eye! I tried to do conductance values to
> percentages of resistance in my head . . . Thanks!
>
> Bob . . .
Message 13
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| Subject: | Re: Engine ground on RV 10 |
Robert L. Nuckolls, III wrote:
> That's ONE braided jumper strap (or 2AWG welding cable
> with terminals and heat-shrink) and as many thin, flat, sheet
> metal bonding straps as you have shock mounts (usually
> 4).
Bob, I want to do that on my RV10. I have the forest of tabs on the
firewall which has an 8AWG wire running back to the battery. I'll run a
braided jumper strap from the bolt on the forest of tabs to wherever
it's best connect it to the IO540 crankcase. And I understand it
doesen't really ground the engine as much as it grounds the forest of tabs.
But what do the 4 "thin flat sheet metal bonding straps" look like? I'm
imagining something forming an arc around the non-conductive shock
mounts but I've never seen this and can't find a reference. Can you
elaborate a bit here or point me to the photos you probably have out on
your site? Is this something I fabricate or buy?
If anyone can help me identify the ground lug on the RV10 engine mount
or the best place to attach a ground on the crankcase, I'd appreciate it.
Thanks.
Bill "ready to hang the engine" Watson
Message 14
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| Subject: | Re: Engine ground on RV 10 |
At 06:59 PM 2/12/2009, you wrote:
><MauleDriver@nc.rr.com>
>
>Robert L. Nuckolls, III wrote:
>> That's ONE braided jumper strap (or 2AWG welding cable
>> with terminals and heat-shrink) and as many thin, flat, sheet
>> metal bonding straps as you have shock mounts (usually
>> 4).
>Bob, I want to do that on my RV10. I have the forest of tabs on the
>firewall which has an 8AWG wire running back to the battery.
Eliminate this dude. It's contribution is too
tiny to measure much less observe. Ground battery
through 4AWG welding cable to the same class of
structure as cited below . . .
> I'll run a braided jumper strap from the bolt on the forest of
> tabs to wherever it's best connect it to the IO540 crankcase. And
> I understand it doesen't really ground the engine as much as it
> grounds the forest of tabs.
Okay, add another fat-wire jumper from forest
of tabs to structure right behind the firewall.
Anyone out there got a picture of the heavy
metal under the floorboards between the rudder
pedals?
>But what do the 4 "thin flat sheet metal bonding straps" look
>like? I'm imagining something forming an arc around the
>non-conductive shock mounts but I've never seen this and can't find
>a reference. Can you elaborate a bit here or point me to the photos
>you probably have out on your site? Is this something I fabricate or buy?
Leave those off. We distilled this process down
a bit from the first thought about using the
shock-mount straps. It's STILL a good idea not
to use the engine mount for anything other
than holding the engine on the airplane.
>If anyone can help me identify the ground lug on the RV10 engine
>mount or the best place to attach a ground on the crankcase, I'd appreciate it.
Bob . . .
----------------------------------------)
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
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