A compilation and observations on the dialog . . .
list: Thank you for your response to Mr. Nuckolls' review of your product.
list: I am sure I speak for most of the 700 members of the list when I say it
list: was appreciated. I predict Nuckolls will like it because of its
specificity
Indeed I do appreciate it. It allows us the opportunity to discuss
features and options and come to some common understandings. I think
what follows will illustrate and bring out some of the variances in
our perceptions.
list: I enjoyed reading the parts of your response which were directed at
list: defending your product and explaining possible misunderstandings.
list: The parts where you attempted to undermine Mr. Nuckolls' knowledge
list: and credibilty were at best lame and at worst embarrassing (for you).
Gently . . gently . . . every one of us can remember a time when we
suffered from hoof-in-mouth disease. I still recall several instances where
a favorite uncle of mine (an electrical engineer and mentor of my very
early years) who could get me to expound at length on something I thought
I knew and understood and then melt me to the ground with a single question.
He never took a whack at me directly but by exploring what I knew with his
own
questions, I wound up whacking myself!
list: I sincerely hope you can find a way to communicate with each other
list: in some other way than on this list as far as your emotions are
concerned.
list: As far as the product reviews and responses... Keep em coming!!
I'll suggest that this list is precisely the place where it should take
place.
It's akin to conduting potentially charged conversation in a public
restaurant
over lunch. By remembering where we are and who is watching, we can focus
much better on the knowlege to be shared and it tends to keep our emotions
in check. People that are put off or bored with all this can simply DELETE.
list: I'm about to order breaker/toggle switch combo's to save some space.
list: Is there any good reason to avoid these, other than the fact if the
list: switch wears out you also lose a breaker?
Very germane to this topic. There's a subtle attractivness to switch breakers
but consider this. One of the goals in architecturing power distribution
is to minimize the size and number of bus bar material. The feed
from battery to breakers is generally short and goes to a single patch
of breakers (or fuses) on the right side of the panel. If your circuit
protection includes switch/breakers and those switches are on the left side
of the panel, you've effectively created a second breaker-patch on the other
side as well. The place were switch/breakers make the best sense might be
if they were grouped with there other breakers in a single array.
list: . . . The Exp-Bus is not directly connected to the battery. The
starter
list:contactor coil lead does feed back to the panel to disable the avionics
bus
list: during cranking. Direct connection is only mentioned in the installation
list: manual as an option. Perhaps it should not be mentioned, but we are
list: homebuilders and should capable of making our own decisions and forming
list: our own opinions given the facts.
Which is exactly what I hope were doing here . . . gathering facts. I'm
very interested in the wiring scenario where a long, always hot feed to
a battery master on the EXP-Bus is recommendable and why. If it's an
"option" I presume it has merit under some condtion as yet unknown to me.
list: Bob is not the only electronics expert in the world. There are thousands
list: of us. Can it really be that Bob is the only one that's right? Frankly,
list: I'm getting a little tired of reading about how stupid the rest of us
are.
There's certainly no intent on my part (nor do I sense it from anyone else)
to make anyone feel "stupid". As you're about to read, there are some
variances in understanding that beg further discussion . . . . .
jh: As the owner of Control Vision and the designer of the EXP BUS, let me
jh: respond to Mr. Nuckles criticism(s) of the product . . many of his concerns
jh: are based on his misunderstanding of the product, and perhaps a bit of
jh: "not invented here"...
I don't think so but I'm pleased that you are here and willing to join
us . . .
jh: There is no reason to have a long hot battery line in any EXP installation.
jh: While this is one option for installing the EXP - this is by no means the
jh: only option . . .
This was an impression I had from another list member's description of a
"battery
master relay" mounted on the etched circuit board remote from the battery. If
this "option" is described in your installation manuals, then under what
conditions would you recommend that your customer elect to use the option?
jh: Most people are installing the EXP with a master solenoid,
jh: particularly in aircraft that are primarily cross country machines.
jh: When installed in this configuration, the starter should be connected to
the
jh: switched side of the solenoid, per our installation manual. His point
jh: regarding the starter solenoid sticking is a minor one, since the starter
jh: is rarely (NEVER?) engaged inflight, this reduces this extremely remote
jh: scenario to more of an irritation, than a safety issue.
Never said the starter was engaged in flight. I and others on the list have
cited numerous instances of starter contactor welding. The potential
for grief even when not airborne is apparent. An uncontrollable starter
circuit failure has a lot of potential for expensive if not hazardous
damage.
me earlier: The self-reseting nature of poly-fuses can hide a latent failure;
you can be suffering intermittant short that you don't catch
because the poly-switch resets when the short clears.
jh: "The self-resetting nature of the polyfuses" is actually ideal for use
jh: in aircraft. Once tripped, they will remain tripped until the load on the
jh: circuit is reduced virtually to zero. They will only reset in a circuit
jh: that is unloaded.
Which is exactly what the "flying" short can do . . . short, intermittant
draws of heavy current interspersed with periods of no draw . . .
jh: . . . . . . . . . . If an intermittent short shuts down the com radio,
jh: the remaining load from the radio will keep the poly-fuse tripped,
jh: preventing the circuit from cycling on and off. To get the PF to reset, one
jh: must TURN OFF THE RADIO. Mr Nuckolls obviously does not understand
jh: how the devices operate. -
I think I do. I was heading the avionics/electrical engineering group on the
Gates-Piaggio GP-180 project about 12 years ago when Jim West (local rep
for RayChem) brought me the first samples of polyfuses. We looked at them
carefully and with a great deal of interest but unable at that time to find
an application on the airframe (they were already INSIDE some products we
purchased). As recent as one year ago, I participated in a dicussion at
Raytheon (Beech) where the polyfuse was again being considered as a viable
subsititute for tradional circuit protection technologies. To date, I'm
aware
of no application of polyfuses at the airframe power distribution level in
certified ships . . . and they HAVE been and continue to be considered . . .
The latent failure I'm refering to is any momentary short that will open a
fuse or breaker in milliseonds and thereby announce it's presense immediately
so that investigation and repairs can be made before it happens again. There
are scenarios where the failure can remain hidden because you have no way
to know when a polyfuse has been called upon to act once the fault clears.
me earlier: One version of the EXP-Bus installation uses the terminals of the
switches to suport the etched circuit board. This adds mechanical
stresses to the switch terminals for which they were not designed.
Slight mis-alignment of the row of switches would aggravate the
condition . . . .
rh: The installation manual advises against mounting the EXP board by the
rh: switch bushings. The proper method is to support the PC board by the
rh: mounting holes, not by the switches. To this end, we now offer pre-stamped
rh: mounting gussets that allow one to quickly install the unit properly in
most
rh: panels. We now also offer rocker switches for a more stylish
installation.
Correct me if I'm wrong but even if the board is mounted by supports to the
board at the corners, how are stresses to the switch contacts relieved when
the builder drills his holes with centers having less precision than the
tooling
that sets centers of switch attachments to the board?
I'm not sure I visualize the recommended support scheme. If the switches
are left on the edge of the card, does the builder then fabricate a shelf
extending back from the panel to support the board?
me earlier: The last time I looked at an EXP-Bus and it's competitors at
OSH last year, they were both dropping wires directly to pads on
a p.c. board with no insulation support. After going to the trouble
to use PIDG terminals on the rest of your wiring, it seems prudent
that insulation support in the rest of the system would be nice.
rh: He is simply wrong here. All connections to the bus should be made using
rh: terminals. We do not advocate "dropping wires" directly to the PC board.
I'm not speaking of installer supplied connections, I'm talking about wires
on your product which are soldered directly into the board with no
insulation
support. I looked at three different versions of this type of product at
OSH and I'm not sure that the EXP-Bus had this feature . . . I know there's
another pre-assembled bus-switch-breaker product popular with the
canard-pusher folk that IS wiring intensive and suffers the problem. If
indeed
the EXP-Bus does not use wires in this way I may have confused it with the
other products . . . my apologies.
rh: Most of Mr. Nuckolls objection to the product seems to be that it does not
rh: save (much) time, money, or weight. For someone of his background and
rh: knowledge, his assertion is probably right. However, most builders lack
rh: his expertise and experience in electrical system design and
implimentation,
rh: and will have more trouble with a "conventional" system than he would
have.
But Jay, I'm here to offer all of the support for the uninitiated as my
talents
and spare time will permit (along with a lot of other folk who have
accumulated no small amount of knowlege and experience) . . . that's what
this
list is all about. I'm intently interested in your evaluation as to where
any
time is saved (assuming one remote mounts the EXP-Bus). My preception is
that
the builder has to install almost exactly the same number of wire segments
and
crimp as many terminals as either switch/fuse or switch/breaker
installations
we've been comparing. And depending on your reply to my earlier query, the
builder may have to fabricate a supporting shelf if he/she wishes to keep
the
switch/board assembly intact?
rh: I invite ay EXP users to comment on this, as they are in a better position
rh: to know than either myself, or Mr. Nuckolls. . . . The EXP product is an
time
rh: saving device that is flexible enough to accomodate the needs of
virtually
rh: all RV's, Kitfoxes, Glasstars and similar aircraft.
Time saving over a switch/breaker installation, you bet! See my post of
last night. A number of builder's have shared their experiences . . =2E
some have installed a variety of system configurations and are in a position
to personally compare the differences but they've not spoken to them
specifically as yet.
rh: Our feedback from customers is that the board saves them time, both in the
rh: installation and in the planning stages of their electrical systems=2E .
.
rh . . . <snip> . . . It is true that the EXP does not solve all of their
rh: problems, but it does solve ALMOST all of their problems.
But what is their basis for comparison? If they're mostly first time
builders
even trivial "problems" can seem huge. It's discussions like these that put
problems in perspective. This dialog may be little more than an intellectual
excercise for those of us who've made lifetime careers of this activity.
I'm trying to maintain an awareness that a lot of folk are going to read
these
words looking for guidance in making their own decisions.
Kindest regards,
Bob . . .
AeroElectric Connection
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