Today's Message Index:
----------------------
1. 08:58 AM - Re: Education is EXPENSIVE but information is FREE (DannyBo)
2. 09:33 AM - Re: Possible Z-14 error?? (Robert L. Nuckolls, III)
3. 10:13 AM - Re: Re: Possible Z-14 error?? (Robert L. Nuckolls, III)
4. 05:30 PM - Re: Z101 in an RV-10 (johnbright)
Message 1
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| Subject: | Re: Education is EXPENSIVE but information is FREE |
Very interesting, actually education everywhere is really expensive
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Message 2
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| Subject: | Re: Possible Z-14 error?? |
At 10:00 AM 9/2/2021, you wrote:
>
>Hi Bob,
>
>I am looking at wiring my RANS S-21 based to a large degree on your
>Z-14 architecture. As I am reviewing it and creating my schematics
>in SolidWorks, I noticed something odd. I am looking at what I
>believe is the latest revision (dated 24-Jun-2013).
>
>On P1, the wire from the cross-feed contactor to the main battery
>contactor is 2 AWG as compared to 4 AWG from the aux battery
>contactor to the cross feed. Since both batteries are the same
>size, it seems these should be the same size conductor unless the
>lengths are dramatically different.
>
>The bigger question I have is why is the conductor on P2 from the
>main battery contactor to the starter contactor 4 AWG when 2 AWG is
>used to the starter itself from its contactor? Did the wire sizes
>from the main battery contactor to starter contactor get transposed
>with the size from the cross-feed contactor to the main battery
>contactor? Or is the assumption that the length from the cross-feed
>contactor to the main battery contactor is long and the length from
>the main battery contactor to the starter contactor is short?
>
>I plan to mount my two batteries side by side with short runs from
>the batteries to their contactors (hopefully less than 12") and
>short runs from the battery contactors to the cross-feed contactor,
>again 12" or less if practical. My batteries will likely be under
>the baggage compartment floor according to the RANS plans which is
>not my favorite location, but the firewall is too crowded and I
>really don't want to run clear back to the tail cone. This means
>that my cable from the battery contactor to the starter contactor
>will likely be 6' or more in length and then another 3-4 feet to the starter.
>
>Given the above, I am leaning towards 4 AWG for the short runs
>between batteries and main and cross-feed contactors and then 2 AWG
>from battery or cross-feed contactor to the starter contactor and 2
>AWG from starter contactor to starter. However, this isn't what I
>see on your architecture diagram hence my question. Although, RANS
>shows 4 AWG for everything from the battery to the starter so maybe
>I am being overly conservative.
Sorry for the delay on addressing this thread . . .
numerous pressing issues elsewhere . . .
The z-figures are ARCHITECTURE drawings
suggesting approaches to FAILURE TOLERANT electrical
systems for a constellation of aircraft and proposed
missions.
So yes, there are some 'anomalies' in wire and
fuse sizing . . . these drawings are assembled from
snippets of other drawings that described systems
in a constellation of aircraft. AFTER a configuration
is selected then do a LOAD ANALYSIS to confirm or
modify the suggested wire size and associated
protection.
Bob . . .
Un impeachable logic: George Carlin asked, "If black boxes
survive crashes, why don't they make the whole airplane
out of that stuff?"
Message 3
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| Subject: | Re: Possible Z-14 error?? |
>Your plan to use 2AWG for long runs and 4AWG for short runs sounds good.
10AWG wire is 0.001 ohms per foot. For every 3AWG steps in
wire size, resistance varies by a factor of 2. Hence
7AWG wire would be 0.0005 ohms/ft; 4AWG would be
0.00025 ohms/ft; 2AWG would be approx 2/3rds of the
way between 4AWG and 1AWG of 0.00012 ohms/ft. Let's
call it about 0.00016 ohms/ft. If you'd like a hard-copy
look-up, here's but one example https://tinyurl.com/4jw4heeh
For broad brush estimating, let's assume 200A for
a average starting current. So, 10 feet total 4AWG
wire in your cranking loop would drop 200A x 10ft x
0.00025 ohms/ft = 0.5 volts. An acceptably small
value. Replacing it with 10' of 2AWG would yield
a voltage drop of 200A x 10ft x 0.00016 = 0.32 volts
or 180 millivolts! If your loop is less than 10'
then the improvement is still smaller.
The attached figure is purloined from Chapter 2
of the 'Connection. In this figure I hypothesis
cranking performance of a 4AWG cranking loop in
a canard pusher . . . i.e. LONG cranking wires.
As you can see, even with these wire lengths,
cranking voltages are rather nominal. Starter
motors EXPECT to see voltages on the order of 9
volts.
In any case, up-sizing wire from 4 to 2AWG produces
about 30% improvement only in WIRE drop while doing
nothing for internal resistance of battery and
voltage drops across other hardware in the loop.
I suggest that with few exceptions (IO-540
engines in a composite seaplane - that airplane
hand a cranking loop of 48ft! We ran doubled
up strands of 2AWG), 4AWG will suffice
nicely for the cranking loop especially
in a metal airplane. A more detailed analysis
is called for in LONG runs on composite aircraft.
Bob . . .
Un impeachable logic: George Carlin asked, "If black boxes
survive crashes, why don't they make the whole airplane
out of that stuff?"
Message 4
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| Subject: | Re: Z101 in an RV-10 |
Some thoughts.
(low) chance of dual alternator failure
I plan to fly periodically with the main alternator off to stress test the backup
alternator in addition to a preflight functional check.
Note the backup alternator has a shear coupling with a 500 hour/5 year recommended
replacement interval per Vic Syracuse, Tempest says 6 years.
second alternators are 20A at most
The B&C 410 and 425 put out 29 and the 462 32A at 2300 RPM on a Lycoming. At 2700
RPM its 32 and 35A respectively. Main advantage of 462 is more current at low
RPM, ref spec sheets.
============
Z101 supports fire-the-cockpit-master-off-engine-keeps-running if you fly with
the engine bus alternate feed on. And master relay failure is benign in flight
and discoverable at preflight.
I plan to fly with the engine bus alternate feed normally on but periodically off
in order to stress test its diode feed path from the main bus.
You can easily add a 2nd stud at the opposite end of a Bussmann 15600 series fuse
block to make the engine bus feeds from the battery and from the main bus separate,
eliminates that stud as an SPOF.
RV-6A with SDS EFI+I and Z101 as a template, not flying yet.
--------
John Bright, RV-6A, at FWF, O-360
Z-101 single batt dual alt SDS EM-5-F.
john_s_bright@yahoo.com, Newport News, Va
https://drive.google.com/folderview?id=1u6GeZo6pmBWsKykLNVQMvu4o1VEVyP4K
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