EXP-Bus . . . some extensive discussions
on various list-servers

November 1999
 An exchange with a "satisfied EXP-Bus user who was recommending
 same to other builders

    So, fresh out of the box, you've invested time and effort on the system 
    that did not go directly to the production of your airplane. 

 >Isn't that what "Experimenting" is all about :). Unlike many builders I
 >spend a lot of time exploring the build process and design issues. 
 >One of the great joys I have discovered with homebuilding is the time I
 >spend working out how to do something and exploring different methods of
 >achieving the task. 

    Oh most certainly!!! I too have many creative features in the machines
    I fly and encourage any and all to exercise their rights and desires
    to do the same. But we were discussing shortcuts of various flavors
    in getting a system installed. My suggestion was that the EXP Bus did
    not deliver on it's advertising hype. I thought you were taking a position
    to the contrary.  Even for your own case, you've already spent 
    more time evaluating and modifying the EXP Bus than I say should be
    required to install and wire it's equivalent collection of parts.

 >Quite probably, but then I knew that before I purchased the unit. My 
 >requirements were for a unit that could hook into my experimental 
 >microprocessor based flight management system. Having had a good chat
 >with Jay Humbard who designed the unit we came to the conclusion that
 >their unit combined with their own monitoring board would actually save
 >me around six months of development time.

   Okay, we're not talking apples and apples here and we need to make sure
   that folk listening in know it. The EXP Bus is attractive to you for
   personal reasons that go beyond the considerations I outlined in my
   original design review.

   Based on your own experience, how would you recommend that anyone purchase 
   and apply the EXP Bus to their own project, and compared to what other 
   technique is anything saved?

 >The recommendation is simple but probably won't please you too much as it is 
 >more oriented to personal psychology than to hard technical  . . . 

    (a piece of your message dropped out here but I get the gist of it)

   On the contrary, it pleases me very much that you have the time, talent
   and willingness to explore new techiques and to share your experiences with

 > . . . .Aero Electric Connection, wire up their own fuse panel and do all 
 >the cabling themselves then this is by far the more preferable but lets not
 >forget those that need a more gentle introduction to the fine art to electrical cabling.

  Then I don't think we disagree on much . . . you're willing to pay the asking
  price for the EXP Bus product to accomplish a certain task. You believe that
  it saves some cabling time and I say it needs to be demonstrated. I sugested
  that after you add the wires nessary to remotely mount the switches, you'll have
  as many or more wires that with any of the techniques I recommend. I don't think
  there's any disagreement between the costs of do-it-all-yourself and using products
  like the EXP Bus.  You didn't speak to any of the other arguments I made.

  What I want people to understand is the difference between USING a product and
  RECOMMENDING that anyone else use the product. Your application for the
  EXP Bus is unique and doesn't demonstrate much for the guy who is spending 
  hundreds of dollars in anticipation of reaping the "savings" offered in the ad.  I too
  dabble in technologies and techniques that I am proud of and willing
  to talk about at length. However, when asked to recommend hardware and techniques
  for an amateur builder, I have a totally different responsability.


    Bob . . . 

/I have been watching this thread for a while. /One Comment /Any time a designer or tech tries to limit a pilots /options to fit HIS idea of what should happen I do /not want to fly the aiplane. No manufacturer has /used fuses in an airplane since the fifties or early /sixties, producing an airplane using them is about as /smart as going back to the Model "T" spark coil /ignition. Further installing them so that the pilot /can not change them in flight is downright dangerous. I'd say that it depends on what you're trying to limit. Options or workloads. May I recommend a book called "The Naked Pilot" by David Beaty. This book and others is a documentation of facts surrounding a series of serious accidents. All were ultimately chalked up to "pilot error" but the book points out how easy it is to become locked into a mindset that defies all logic and explanation. Airlines don't permit most crews to mess with the breakers except "critical to flight" and then reset only one time. I'll suggest that it's advantageous to make sure that your critical systems are backed up, not made "repairable" in flight. The fuses we're speaking about have evolved a great deal since the sixties . . it's not a regression to consider using them again. ---------------------------------------------- Another response received on the same subject: ---------------------------------------------- >All you say may be right, Bob, but you are bordering on flaming. >It smacks of "I am the only one here who can be right". If you >want to keep credibility, and I have enough background to believe >that you usually are right, you need to tone down the innuendo >so that you are effective in communicating. I was afraid some folk would take the "my mind's made up" message the wrong way. My point is simply this: To this date, ALL of the contrary responses received this subject have contained no data. I've not and never will flame anyone or anything but I will sometimes show my frustration with the the lack of critical dialog on the subject. I'm inviting you all to participate in the same kind of critical design review I enjoy with my peers in my professional capacity. My critical assessment of the advertisement for the EXP-Bus was that it saves neither time, weight, dollars nor does it add any level of safety over other circuit protection methods and I explained why I thought so. To date, there have been many proponents of the product jump up and recommend the device but not one has shown where my assertions were wrong. The banner in my signature file is not an attempt at tongue-in- cheek humor; I'm serious. The list-server is just a communications tool . . . it can spread the good, the indifferent and the ugly. It's only through reasoned dialog that the good stuff can be sorted out from the rest. In the final analysis, one may always build their airplane any way they please but when someone asks for advice, advisors owe it to the advisee to impart as much understanding as possible. Regards, Bob . . . AeroElectric Connection //// (o o) ==========oOOo=(_)=oOOo========== | | | Go ahead, make my day . . . | | Show me where I'm wrong. | ================================= http://www.aeroelectric.com
/I have been trying to follow this thread over the last /weeks, and the more I follow, the more confused I get. /Initially it appeared to me that the ExpBus was a great thing, /even if a little expensive. It appears now, after following your /answers that every feature on it has drawbacks that would make /it even dangerous to use. It DOES have some safety issues but by-in-large, I'll suggest that it's worst sins are that it's less than truthful in its promotion. You're correct, $250 is a pretty good chunk of change. /Because you have the experience and knowledge that you have, /why don't you design something similar using your approach to /parts and construction, that can be built by us. It could /even be packaged with instruction and parts. I'm not sure anything needs to be fabricated by me or anyone else to provide a more acceptable alternative to wiring an airplane. If one purchases a battery master relay (mounted where it belongs . . . right next to the battery) a couple of Bussmann 15600 series fuse blocks (mounted under the panel where ever you would have mounted the remote EXP-Bus board) and the toggle switches (mounted where the EXP-Bus switches would have been mounted) that you'll have exemplary protection, convenience and very nearly an exact duplicate of the EXP-Bus remote mounted wiring task. Assuming: Fuse Block Breakers Fab/Install Estimate Battery Contactor: $20 $20 1 hr Breakers (30) 600 16 hrs Fab, Assemble & Wire Fuse Blocks (2): 60 1 hr Fuses (30): 7 Switches (10): 57 57 3 hrs Terminals (56): 6 6 2 hrs Assted Wire between protection and switch 5 5 _____ ____ $155 $688 These times are estimates of how long it would take me to fabricate switch and breaker panels and do drawings for purchase of engraved overlays. The fuseblock installation saves you $100 over EXP-Bus and $530 over breakers. Except for the fabrication of bus bars and breaker panels, either installation presents no bigger a wiring task than the remote mounted EXP-Bus installation and the values I've give above allow for up to 30 protected circuits. Further ALL parts are off-the-shelf distributor items available from dozens of sources. This is another plus for rolling- your-own that I'd not thought of before. Except for the Bussmann fuseblocks, there are NO proprietary fabricated parts and lots of alternatives for sources. Bussmann stands a VERY good chance of being around for awhile. So . . . future repairability and cost of ownership of the parts-built system are quite attractive. /I'm not very good at electronics even though I have a degree /in Office Machine Repair and worked at the trade for about 7 /years. Replacing parts was one thing, but designing circuits /was something else, and now, I'm going to be "designing the /circuits in the GS. The simplicity of just connecting to the /ExpBus was what cought my eye. It was your relative inexperience in designing and fabrication that hooked you. If someone hands you a relatively complex looking piece of stuff and says, "lookee here at all the time and effort I can save you by doing this in advance and handing it to you as a completed assembly." What the offeror doesn't tell you is that all the custom assembly work may not be necessary or is easily replaced by machine fabricated parts using other sources and technologies. /Anyway, I'll keep following the thread, maybe things will eventually /fall into place when I start wiring......I'm sure thankful there /are people on the net like you and the others. Keep up the good work. Thank you. Again, I'll point out to folk following this thread and others. My mission is to discover and then share the most cost effective ways to accomplish a task with NO compromises in performance or safety. Airplanes are an EXPENSIVE hobby. I believe that if we all put our heads together and figure out how to trim unnecessary time, cost and weight out of the more traditional techniques, you'll stand a better chance of having more time, dollars and/or panel space to install something that enhances the utility of your airplane.
Re: EXP-Bus . . . a compendium 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 . . . . jh: The installation manual advises against mounting the EXP board by the jh: switch bushings. The proper method is to support the PC board by the jh: mounting holes, not by the switches. To this end, we now offer pre-stamped jh: mounting gussets that allow one to quickly install the unit properly in most jh: 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. jh: He is simply wrong here. All connections to the bus should be made using jh: 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. jh: Most of Mr. Nuckolls objection to the product seems to be that it does not jh: save (much) time, money, or weight. For someone of his background and jh: knowledge, his assertion is probably right. However, most builders lack jh: his expertise and experience in electrical system design and implimentation, jh: 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? jh: I invite ay EXP users to comment on this, as they are in a better position jh: to know than either myself, or Mr. Nuckolls. . . . The EXP product is an time jh: saving device that is flexible enough to accomodate the needs of virtually jh: 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 . . . 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. jh: Our feedback from customers is that the board saves them time, both in the jh: installation and in the planning stages of their electrical systems. . . rh . . . . . . It is true that the EXP does not solve all of their jh: 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. Further, if a first time builder believes he has saved some time, how can he offer a comparison between what he has just done and something he's never done? 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 //// (o o) ==========oOOo=(_)=oOOo========== | | | Go ahead, make my day . . . | | Show me where I'm wrong. | ================================= http://www.aeroelectric.com

This pretty much ended the discussions . . . Jay did not choose to continue the dialog nor did he answer my specific questions . . .

Comments and alternative views welcome!