Chapter 22 – Electrons vs. Paper

Posted on 27 December, 2016 by Airdog

Well, as I pointed out, between the holiday stuff, the football, and more importantly, this nasty cold I’m fighting, I have abided by my previous statement that the build would slow down quite a bit.

I did finally receive a pack of 1/16″ roll pins that I ordered, so I was able to mount my gray finger grip back onto the landing brake switch post (permanently). Last year I had to drill out the original roll pin in order to get the finger grip off to then allow me to remove the switch from the throttle handle housing. In fact, the hole that is now visible on the side (top) of the switch grip wasn’t there when I started last year and was created as a result of my drilling endeavors. Presently, I put some E6000 on the bottom side of the switch to help seal up the roll pin hole.

Barring any other adventures, this does it for the completion of my throttle handle switch installation, wiring & prep. Over the next few days, when I start feeling a LOT better, I’ll drill a hole or two in the lower left area of the instrument panel bulkhead to mount some Adel clamps for use to secure the throttle handle cable (and whatever other wiring needs secured).

The remainder of my work over the past couple of days has been around finalizing the electrical system push. For one, I started compiling a list of even more electrical system components I’ll need for the future (shielded wiring, consumables, etc.). I also printed out a couple of batches (~12) of heat shrink wire labels and attached some of those.

One main thing I’ve been doing, since I’m really not feeling up-to-snuff, is updating my electrical diagrams. You can imagine there is simply a myriad of data that needs to be annotated (in digital form, vs. my own chicken scratches!) on these diagrams: wire colors, wire sizes, wire labels –these change a lot with the addition of connectors– circuit changes, etc. I would say that it’s not uncommon for me to have anywhere from a dozen to 50 data points on each diagram that requires updating, which in and of itself isn’t necessarily or overly difficult. However, the crosschecking (or consolidating) of ground points, bus tab positions (again, or piggybacking) –and making the decisions on those as well– is what eats up a good bit of time. And of course there’s the oft required research that may accompany any such decision.

In addition, I’ve done (or simply documented) major circuit design revisions, mainly the items that are controlled via the airspeed switches and/or ancillary relays. I also did a major overhaul of my panel dimmer and cockpit lighting & dimming circuit design as well. As a point of reference, I haven’t touched this particular wiring diagram since June 2014, so it definitely needed some attention.

I’m about 2/3rds through the diagrams and don’t have that many more to go. Once I start feeling better, with my electrical system documentation updated, I’ll be ready to start back on some real work . . . like perhaps some wheel pants. I will note that the wheel pants are most likely the only thing that will get done in the next couple of months since I really need to start flying again: A LOT!

Chapter 22 – Relay this!

Posted on 24 December, 2016 by Airdog

I started off today by finishing up the wiring harness, for lack of a better term, for the MGL RTC-2 clock. I printed out the heat shrink labels, put them on, and then terminated the wires into the connectors (P6 and J4, both B sides).

With the wiring finished I then decided to do a quick checkout of the RTC-2 clock, so I hooked it up and fired it up. I then familiarized myself with the screen system and set up some of the parameters. With everything looking good I turned it off, pulled the plug and put it back on the shelf.

I then started in on wiring up the relay for airspeed switch #2 to control the 3 components that are controlled by this airspeed switch, all below 70 knots:

Taxi Light extension
Low speed warning (via AG6)
RAM air butterfly valve open warning (via AG6)

Note in the pic below that I cut off the Normally Open (NO) pin since it’s not required in this configuration.

For the power feed side of the relay, off the NC pin, I tied 3 wires into one to connect to the relay. Again, I did the Bob Nuckolls’ technique of using a pigtail from the single wire to wrap around the wire bundle.

Here’s a closeup.

I then soldered the wire connection bundle.

And then covered the joint with some heat shrink for wire security.

I then soldered the power lead to the relay and wrapped the wires around the relay in prep for heat shrink.

Which I added next. The heat shrink really does a good job of holding the wires securely in place.

I then terminated and labeled the wires. I also built the separate wire for the #2 terminal on the airspeed switch, which is simply a ground wire to the avionics ground bus (G5) [single black wire in upper right corner].

I then got to work on the last ancillary relay that will be added (at least at this point) to the electrical system: the COM1-COM2 PTT switch relay. Since I only have an (ON)-OFF-ON switch available to me on my control stick, I had to use a relay if I wanted to use that switch to flip between my COM1 and COM2 radios for PTT. Here’s the switch positions:

ON (Up) – NO relay position that closes to switch PTT to COM2 radio
OFF (Middle) – Default NC position, keeps PTT on COM1 radio unless flipped up.
(ON) (Down) – Momentary ON position that is NOT run through the relay. Controls COM1 radio freq FlipFlop (COM2 radio FlipFlop & functions controlled via HXr EFIS). Does not effect the middle OFF/NC relay position.

I started with the main bus fed power wire and soldered it to the coil pin.

I then soldered the other wires into place. The purple wire connects to the COM1-COM2 PTT flip switch on the control stick. The 3 wires with the black heat shrink are all 22 AWG shielded wires. The common wire goes to the Dynon Intercom, with the other 2 wires going to the COM1 and COM2 radios, respectively. (COM1 = NC, COM2 = NO)

As with all the other relay packs that I’ve assembled, I then wrapped the wires around the relay and covered it with heat shrink.

I should note that I tested both of these relay circuits out and they both worked great. I won’t be working on the build at all tomorrow (Christmas), but I will be back on it Monday. I would like to also point out that I really am coming to the end of the line on this round of electrical stuff, so I will soon be moving back into the realm of the wheel pants!

Chapter 22 – Wiring Heated Pitot Tube

Posted on 20 December, 2016 by Airdog

Well, as per usual I knocked out one of the “low-hanging fruit” items first. I had to go down to the shop to measure some stuff & check component fit in the nose, so I drug the Radenna SkyRadar ADS-B receiver and power cable down there with me. I checked the required length of the cable and then upon returning upstairs, I cut the power cable. This included cable, by the way, had a cigarette lighter charger adapter on the end of it.

I then verified positive & negative sides of the cable and then terminated each wire with a D-Sub pin. Later on, without the ADS-B receiver in hand, I looked up its 2-character code and somehow derived that it was “DX,” so that’s what I used on the labels. Then after affixing the heat shrink labels I realized that the code was actually “AD”…. not “DX”. Ugh! So, instead of redoing the labels, I double checked my list and sure enough I wasn’t using “DX” for anything else, so I simply swapped the component ID sticker label to DX. This all took place after I took the pic below, but the component ID is now DX for the ADS-B receiver. Endless fun in Never-never Land kids!

I then got to work on my main task of the day: getting the heated pitot tube circuit completed between the airspeed switch #3 (40 Kt) control relay and the pitot tube power relay. Since I got the correctly rated relays –as defined by Bob at TCW Tech– in from Mouser, I could move forward on wiring up my #2 and #3 airspeed switches. To be clear, my buddy Marco is working on a high end control box for the heated pitot tube that when completed can easily be implemented into this system. As for now, I’m simply using a $3 relay to ensure that my pitot system is ready, barring any delays that Marco may incur on the Arduino-based heated pitot tube control system he’s developing. After all, he has an airplane to build as well!

Here’s a shot of my general purpose relay. Again, the main requirements for these specific relays that I’m using for the airspeed switches was A) minimum 600 Ω resistance on the power coil, and B) small, narrow body to allow EZ placement inline to the wiring.

Since I was going to heat shrink wrap this baby after I finished, I went ahead and removed the NC (normally closed) pin since it had no role in this circuit design. What remained where the 2 coil posts to the right, then moving left the common (C) terminal, and then far left the NO (normally open) terminal.

I then soldered the power (red & red/yellow) wires into place. And the ground control wire that hooks into tab 1 of the airspeed switch (orange/black). As per Bob at TCW, I also soldered in a 1N4001 diode between the power connections across the coil.

On the NO terminal I soldered in a long 22AWG wire that terminates into + side of the heated pitot tube POWER relay (here I’m working on the control relay… again, there are 2 total relays for this circuit).

I then wrapped the wire leads around the body of the relay for strain relief and then heat shrank the whole assembly together.

Here’s the finished product, with each wire appropriately terminated and labeled. The black wire twisted in with the purple/blue wire is simply the return ground for the + / − coil control on the heated pitot tube POWER relay (RL005).

Over the next few days, when I get a chance, I plan to build the airspeed switch #2 relay much in the same fashion as this one. AS #2 will be a 70 Kt control relay for taxi light (allowed to extend below 70 Kts), the RAM air valve open warning (below 70 Kts), and the Low Speed (~stall) warning.

Again, with social events and out-of-town guests stopping by over the holidays, I’ll be busy with all that. But I will try to sneak some work in here and there when I can.

Chapter 22 – P6 Connector Wired

Posted on 18 December, 2016 by Airdog

Although I did get a fair bit of football watching in, I still managed to print out a couple sets of wire labels and get over a half-dozen cross connect wires constructed so that I would have something to label!

Here’s a shot of the right-side Triparagon with the P6 (A side) connector about 90% populated,which includes cross connects from the E-Bus.

To highlight what’s involved on these: every wire that is made must be double-checked for the proper gage, color and ID label. I then ensure that this is documented both on the connector pinout sheets and also in any of the pertinent wiring diagrams. For grounds especially, I ensure not only that the ground buss matrix spreadsheet is updated but that the wires are connected to the optimum terminal on the buss. Obviously, buss terminal placement for each power buss termination is scrutinized as well.

Here’s a closer look at the main bus and the wires terminated into the P6 connector.

Tomorrow I’ll continue to finalize all the Triparagon cross connect wiring, primarily on the J4 Signal PQD connector. It should be another day or two max and I should be done with the wiring that can be completed this go around. Then on to the Wheel Pants!

Chapter 22 – In the weeds!

Posted on 17 December, 2016 by Airdog

I didn’t get a ton done today on the right side Triparagon component wiring, but I did get some significant stuff done. I did get a few more P6 PQD connector wires terminated, labeled and in place, but today was really all about getting the remaining 3 Integrated Backup Battery System (IBBS) leads up to speed.

The 3 leads the IBBS wiring harness that I left long before are the EFIS backup battery info lead, the X-Bus voltage (AG6) lead, and the IBBS power on/off switch lead. The issue is that of the 3, I can’t terminate 2 of them since I wouldn’t be able to fit them through the hole & grommet in the Napster bulkhead if I did. The X-Bus voltage monitoring lead, which is an optional lead that would normally power an LED warning light, is the only one I could terminate since I simply chose to use the ‘ol inline D-Sub pin-to-D-sub socket connector trick (again, ala Bob Nuckolls).

Since a D-Sub pin is barely –if at all– bigger than a 22 AWG wire, then I had no issue terminating the voltage info wire lead with one. That being said, however, although I printed the labels for this wire I can’t heat shrink them in place until after I get the wire installed through the Napster bulkhead! The labels simply add too much diameter and since they’re rubbery in texture, too much friction.

Now, the X-Bus voltage monitoring lead is a little unique in this configuration since it also feeds a piggy-backed wire to the AG6 warning annunciator that lights up if there is a low voltage condition on the X-Bus. Again, in the stock installation configuration, this would be an LED lighting up, but I’m connecting it the AG6 for the warning annunciation. To ensure the proper power on the circuit I needed to place a resistor in the circuit to protect the AG6 (and mimic a load of an LED light… I know, not much juice there). I originally had identified the need for a 2K Ohm resistor, but I only I had a 1.5K resistor on hand, so in it went… good enough!

Thus, my first task of the day was to solder a small lead onto the 1.5K Ohm resistor, or perhaps solder the resistor to the lead . . . who knows?!

Anyway, here’s the resistor soldered to the 22 AWG wire lead.

I’m using the same configuration for soldering a resistor inline as I did for the Voltage Regulator, which allows for excellent strain relief for the soldered resistor (BTW, I picked up this nifty trick off the EAA workshop videos). To the open side of the resistor I then soldered the AG6 lead (white/green stripe wire) and a mini-pigtail terminated with a D-Sub socket (purple/yellow stripe) to later mate up with the wire coming from the IBBS (that I terminated with a D-Sub pin/above).

I then terminated the initial mini-lead with a D-sub pin, since this will actually get terminated into the 9-Pin D-Sub X-Bus connector (B side).

I then covered each of the solder joints with heat shrink.

And then the entire resistor zig-zag joint with a piece of heat shrink. Note the 3 other leads –coming from the P6 connector– that are terminated into the X-Bus 9-Pin D-Sub connector.

I then test fitted it into the 9-pin D-Sub back shell, confirming my initial hypothesis that it would fit.

I then mounted the opposite side of the back shell in place. The fit is tight, but not uncomfortably tight where it has to be forced. (Both sides shown below).

That’s it for today. I’m heading out for dinner and a movie with friends, so no more build tonight. Also, tomorrow will most likely be a light build day as well since we’re heading into the end of football season, with lots of big games and lots of big playoff implications!

Chapter 22 -Wiring Triparagon

Posted on 16 December, 2016 by Airdog

As I mentioned before, my final act on this big first round of working on the electrical system will be to wire up all the cross connections I can from points A → B on the Triparagon itself.

I started off working on the gear & canopy warning module, and its partner in crime: the warning horn. I wanted to get those wired up as best possible since they reside immediately above all the PQD connector wiring. My first task was to extend the positive side (red) lead out of the Warning Horn, which connects through a 3A fuse on the Main Bus. I fired up my trusty soldering iron and soldered a length of red 22AWG wire to extend the Warning Horn lead. I then added heat shrink over the joint, labeled the wire, and then terminated it with a FastOn connector.

Here’s a big picture shot of my work on the right side Triparagon. Once I get the cross connects on this side complete, I’ll move to the left side.

Besides airspeed switch #1, the majority of my cross connects have been between right side Triparagon resident components and the PQD connectors; primarily the big P6 connector, which you can see in the upper right corner.

Here’s a quick shot of the area where I do the majority of my cable building and connector terminating/assembly.

Tomorrow I’ll continue to work on the right side Triparagon cross connects, then move onto the left side next.

Chapter 22 – Triparagon complete!!!

Posted on 15 December, 2016 by Airdog

I’d like to first off point out that it was a year and 10 days ago (Dec 5, 2015) when I first used the term “Triparagon” in my build blog. Now I of course use it as a common term. And what was once just a flurry of ideas and thoughts regarding the Triparagon has made its way into finalized reality. What the Triparagon has become is even better than what I had envisioned about 13 months ago when I first had the epiphany to do this.

The best plans rarely account for everything, and as far as the Triparagon is concerned I greatly underestimated the time and effort it would take to simply create the lightening holes. Thus, when I looked at the Triparagon this morning, after the “last & final” round of lightening holes, I should have been put in the looney bin when I decided I could go just one more round using a smaller 0.190″ drill bit. So that folks is exactly what I did: an entire FINAL round of lightening holes!

I also noted that I could actually remove a bit more weight by rounding the corners of the vertical Triparagon plate. So before I started in on the final round of 0.190″ lightening holes, I drug out my Saber saw and did some cutting. After I finished rounding off the corners, I then got to work drilling the small holes. If the area could take a 0.190″ hole and still have a good amount of metal for strength, it got drilled!

After the final round of lightening holes was finished, I then set about for the next 3-1/2 hours in chamfering the holes. I did it the in my typically poor man’s milling machine style by using my drill press with a slightly larger bit, and going very slowly (the downward motion, not the bit) to create a nice edge on each hole, albeit a fair number of them are a hair off center.

After chamfering the smaller holes I then finished the edges of the larger holes. [I had to finish up the last handful of smaller holes with a cordless drill since my chuck assembly literally fell out of my drill press while chamfering one of the holes. Luckily the hole wasn’t next to anything important because it created a decent sized crater where a nice lightening hole had once existed!]

I then drilled and installed 6 larger rivets across the top of the cross shelf mounting brackets to permanently mount them to the Triparagon vertical plate. Afterwards, I drilled 0.190″ lightening holes in-between the rivets.

Then, for the first time, I officially mounted the cross shelf to the Triparagon vertical plate!

Here’s a top view of the cross shelf. You can see the lightening holes of the cross shelf mounting brackets through the lightening holes in the cross shelf.

And another view of the cross shelf, after I installed the diagonal support arms (which again requires mounting the Schottky diode heat shrink).

Here’s a side view of the finished & assembled Triparagon structure.

I then took it down to the shop for one final test fit (and the requisite round of pics!) before remounting all the electrical components back onto it. I figure it will be a long time before the bare Triparagon structure sees the light of day again.

Here’s a shot primarily showing the diagonal support arms and the front cross shelf overhangs.

And from the right…

Here’s a shot from the aft side of the now permanently (but removable!) cross shelf attached the vertical Triparagon plate.

I removed the Triparagon from the fuselage avionics area and took it back upstairs to start reattaching the electrical components to the structure.

Besides the required Schottky diode heat sink, the next items to get attached were the back-to-back attached AG6 warning annunciators (AG6A & AG6B).

I then remounted the Roll Trim relay board.

Now, I wanted to use some type of thread locker but all I had was red & blue. I went out on a quick quest to find some purple Loctite, for small diameter screws, but as per usual it was a lesson in futility after visiting 3 different stores. I remembered reading a forum post regarding thread locker from our friends in the VANs world. Sure enough I found it. A guy on the forum reported success with grey silicone RTV, and recounting in my mind the characteristics of the blue RTV I had used (not wisely!) to protect the bolt threads of my canard mounting tabs when I glassed the shear web, I figured I would use that vs. an actual thread locker (second pic below). To be clear, I only used it where I wasn’t using a nut on the other side of the plate to secure a screw.

I then remounted the 4-port USB hub with locking screws & nuts, and then the Avionics ground bus (G5) and Carbon Monoxide detector (CO), both with blue RTV.

I then remounted the Main Bus and E-Bus, which share the top 2 screws & AN3 nuts, and thus are physically clamped onto the Triparagon plate. The bottom screws for the E-Bus got blue RTV. Only one bottom screw for the Main Bus got blue RTV because the other one is shared as the aft mounting point for the SmartStart module, so it too gets an AN3 nut. Below you can see the E-Bus and the SmartStart module mounted on the left side of the Triparagon.

And here’s the right side of the Triparagon, with the Main Bus remounted. I also remounted the Trim relay box (TCW’s Safety-Trim) which shares its aft upper screw as the forward mounting point for the SmartStart module on the opposite side. The other 3 stainless steel countersunk screws on the Safety-Trim box got slathered up with blue RTV.

I then remounted the PQD connectors: 1 AMP CPC connector and 2 D-Sub connectors.

Here’s a shot of the aft side of the remounted PQD connectors. Notice how bare the area is just to the right of the PQD connectors …

Not anymore! I mounted the gear & canopy warning module (WG) and the Piezo warning horn (WH) in the space just forward of the PQD connectors, on the bottom left side of the cross shelf.

Here’s another shot of the installed gear & canopy warning module (WG) and the Piezo warning horn (WH).

I then got to work on doing a final mount of my 3 airspeed switches. Airspeed switch #2 and #3 were fairly EZ, but #1 was a bit of a pain. I had to remove and trim down the top of the horizontal arm piece on the left diagonal support to allow clearance for the airspeed switch. Specifically clearance for one of the FastOn connectors that mount on the underside of the airspeed switch, which was not accessible with the current configuration of the diagonal support arm.

After trimming the diagonal support arm, I remounted it and test fitted airspeed switch #1. There was still just a bit of interference with the support arm, but I had removed all that I could before actually cutting into a lightening hole. I found a 3/4″ 4-40 spacer and cut it in half, and tried out the 3/8″ spacer (vs the 1/4″ spacer I was already using!). Voila! That did the trick. I then mounted airspeed switch #1 to finish off the mounting of all the “CrackerJack” parts.

Here’s a closer, albeit blurry, shot of the right-side mounted airspeed switches. You should still be able to make out the airspeed set screw for airspeed switch #1 through the hole in the cross shelf overhang.

And here’s a shot from behind, showing the staggered #1 and #2 airspeed switches. Note the clearance between airspeed switch #1 and the top of the diagonal support arm.

The final, no kidding, total weight penalty for installing the Triparagon is right at 1.2 lbs. Of course if you take into account the amount of wire in runs saved, and the myriad of separate mounting hardware, glass and epoxy to mount things on the sidewalls in the avionics area, I’d argue that there’s at least a quarter of a pound there, making the comparative weight penalty more around 3/4 of a pound. The weight comparison also doesn’t take into account the increased ease-of-use for the Triparagon.

Tomorrow I actually need to get some stainless steel hardware that I thought I had on hand to swap out with some of the hardware I used today. With Christmas getting closer I still plan on getting stuff done on the build, but it will be a tad less than normal.

Chapter 22 – Lightening the Load!

Posted on 14 December, 2016 by Airdog

I started the day off by finalizing and pulling the trigger on both a Mouser order and a quick ACS order (it appears that someone –ha!– forgot to order some 22 AWG shielded wire…).

I then got to work on the Triparagon vertical plate. I stripped off the cross plate, diagonal support struts and the Schottky diode/heat sink and got to work for the last and final serious round of lightening holes. The starting weigh-in this round for the Triparagon vertical plate, with the grommets and cross shelf brackets including 6 x K1000-3 nutplates, was 0.82 lbs. My goal was to get the weight down by another 0.2 lbs.

After drilling a 1″ lightening hole and 10 each 5/8″ holes, it weighed in at 0.78 lbs. At this point it was really time to get work. As you can see, I Swiss cheesed this thing like no tomorrow to drive the weight down to its possible lowest, without sacrificing strength. I used an 11/32″ (0.344″) drill bit to get all the in-between spots that I could while, again, still leaving enough meat on the bone for this thing to be as strong as it was before. It is an interesting concept that you can remove so much material, but when I flex it, it feels as strong as when it was a solid panel.

After squeezing in as many 11/32″ holes as I could (I have about 3-4 more places I can get with a slightly smaller bit), and drilling 3/16″ lightening holes on the upper arms of the cross shelf mounting brackets, I’m sitting at 0.68 lbs. for these components. Obviously, this isn’t quite as low as my 0.62 pound mark, but I’ve squeezed just about all the weight out of this thing that I reasonably can.

When I weighed the entire Triparagon assembly as a whole, it weighed in at 1.18 lbs, including hardware. Since I have just a handful of lightening holes to drill, if I add in the weight of the aircraft-side mounting tabs and the hardware, I’m right around, or just a hair over, 1.2 lbs. My initial goal was a pound or less for the entire Triparagon’s added total weight, so an extra 3.2 ounces ain’t bad… I can definitely live with that.

Thus, as Vince Lombardi said, “Perfection is not attainable, but if we chase perfection we can catch excellence.” Clearly I didn’t reach my ‘perfect’ requirement, but I got pretty close. In putting in a lot of effort to get as much weight off these components as possible, I feel like I’ve definitely achieved excellence in that regard.

Tomorrow I’ll spend a few hours chamfering the myriad of lightening holes I drilled today. I’ll then rivet the cross shelf mounting brackets in place, drill lightening holes in between the rivet locations and call the Triparagon build complete!

Chapter 22 – Triparagon Erector Set

Posted on 13 December, 2016 by Airdog

Funny, before I sent a few pics of my progress to my buddy Marco, I was thinking that this thing sure does look like an Erector Set. Sure enough, Marco texted back the same thing so I figured it would be a fitting title for today’s post.

I started off with a couple of shots of the Triparagon showing how it looks as removed from the airplane with all the electrical accoutrements attached. You can see on the right side that there’s a big bare spot where the original X-Bus once resided. Now I have more space to mount more toys in the future!

The goal for the day was at a minimum to get the diagonal supports in for the cross shelf. I was able to accomplish that. I was also trying to get the last round of lightening holes drilled on the Triparagon vertical plate . . . that did not happen.

I got to work by stripping the Triparagon of all of its encumbering components, ensuring that each component and its hardware got bagged so as to keep track of they myriad of little pieces parts.

I then gathered up my 1/2″ x 1/2″ by 1/16″ thick 2024 angled aluminum extrusion and did a bunch of figuring out, measuring and head-scratching to configure the right side diagonal support. Because of the location and angle that it intersects with the vertical plate, I went ahead and decided to simply mount it with 2 x 4-40 screws to the aft end of the Schottky diode heat sink, which in turn is of course mounted to the Triparagon vertical plate.

After getting all my measurements and angles finalized, I marked up the extrusion and cut it. Since it’s really cold outside and it was more trouble than it was worth to pull out a miter saw, I simply cut this by hand using my German hack saw. I needed to remove a length of one side of the angled extrusion on the top-oriented end to make room for the static line attached to airspeed switch #1. I cut the perpendicular side with my hacksaw, but for the rip cut at the corner edge I used the Dremel with a cutoff wheel (pic is a bit blurry).

I then drilled a hole for a #8 screw through both the diagonal support and the right corner of the cross shelf overhang mounting tab. I then drilled and riveted a K1000-8 nutplate to the top end of the support arm. As you can see, I also marked the diagonal support arm with lines running the full length to drill lightening holes.

I then drilled a series of 3/16″ lightening holes. Although I used my drill press, they’re still far from perfect. But they lighten the piece and provide holes to secure wires to, so requirement met!

Here’s a shot of the finished right-side diagonal support arm for the Triparagon cross shelf.

On the left side I had nothing to mount the support arm to on the lower end of the arm, so I cut a 1.55″ piece of 1/2″ x 1/2″ by 1/16″ thick 2024 angled aluminum extrusion to make a small mount bracket. I planned to have the mount secured to the vertical Triparagon plate using the same 2 screws that also secures the aft edge of the Schottky diode heat sink (different screws than the 4-40 ones used above to mount the right side support arm).

I set the length (technically height) of the mounting bracket so that the screw holes would be about 0.2″ in from the top & bottom edge, so after cutting the mounting bracket to 1.55″ I simply marked and drilled a hole 0.2″ from the edge. I also tapped the hole to accept a 4-40 screw. I can of course drill this out later if I simply want to use a nut with the screw later on.

I then mounted the bracket in place, removed the lower screw and marked the hole with a Sharpie. I then removed the bracket and prepped it for drilling.

Jumping ahead (I had a pic or two in-between, but they came out frustratingly blurry!), here’s the completed left side diagonal support arm. Note that I used rivets to secure the arm to the mounting bracket. Also note that I drilled a number of lightening holes in not only the support arm, but the mounting bracket as well.

I then mounted the diagonal support arms in place on the Triparagon and snapped a bunch of pics.

Here’s a shot from the front right side of the Triparagon looking aft.

And another one from the front left side looking aft.

A head on shot looking aft.

And what you would see if the instrument panel was see-thru.

A bit closer from the front right & left looking aft.

A low angle shot looking from the left side forward.

And the final low angle shot looking from the right side forward.

Tomorrow I’ll remove the cross shelf and the diagonal support arms and drill the final round of lightening holes into the vertical Triparagon plate, which will be the end of my Lightening hole drilling on this thing! Once done I’ll clean up the holes and then start back with the final (permanent) mounting of the electrical components on the Triparagon. Then over the next few days I’ll get as much of the cross-wiring and interconnects knocked out as I can. Once that’s done –as well as a few minor Adel clamp hard points, click bonds, etc. floxed & glassed into the avionics bay area– I’ll call it quits on the electrical stuff for a while AND… get back to work on the wheel pants!

Chapter 22 – Taxi Light & Airspeed Switches

Posted on 12 December, 2016 by Airdog

Last night I diagrammed out the 8-position DPDT relay required for the new taxi light servo. Besides adding the relay into the mix on the Lights wiring diagram page, I also updated the wire depictions from the switch to the landing light to better highlight the shielded cable. I also added in the J0 & J7 connectors.

Today was all about the incorporation of airspeed switches, of which I have 3:

AS001 – 100 knot exclusively switching trim fast⇔slow to provide faster trim response at slow speeds and minute trim changes at high speeds.
AS002 – 70 knot for low speed warning (AG6), RAM air open warning (AG6) and taxi light deployment, all occurring below 70 knots.
AS003 – Exclusively for heated pitot tube shutoff below 40 knots. This is a safety feature of course since I have an extremely high heat producing element in the nose of a plastic airplane that absolutely must be off when the plane is not moving.

The speeds may seem a bit generic right now, but remember these are simply target speeds and are totally adjustable. I’ll of course dial them in once the plane is flying. Also, a point of note is that none of the items controlled or reported on by these airspeed switches are actual flight control components. If the trim airspeed switch dies, then I’ll simply control the plane with a higher or lower than optimum sensitivity on the trim, or simply sans trim…. a pain yes, but a safety of flight issue? no.

The above all being stated, I realized this weekend that I had a significant issue with my airspeed switches: I just had no idea how to wire these guys up!! They seem simple enough in theory, and are right there for the purchasing at Aircraft Spruce… so what’s the big deal? Well, at the bottom of the scant bit of info on a 1-page install instruction sheet, it inconspicuously states at the bottom: Maximum switch current = 20 milliamps.

What???

20 milliamps?! What do I have that uses anywhere near 20 milliamps?? … except maybe my 2 AG6 warning annunciators! Hmmm . . . another mystery. How do I wire this airspeed switch in series to something I’m controlling, when the airspeed switch can only handle 20 milliamps? If I were simply using this to report warning states from airspeed-switch-only derived info [<, > speed x] than no worries. But clearly that isn’t the case.

Thus, the first thing I did today was called Bob at TCW and left him a voicemail with an overview of my dilemma. I then worked on some needed updates on this web site for a couple hours. I also updated my grounding buss pinout matrix (below).

As I was finishing up some administrivia, Bob called me back. He essentially told me to roll up my sleeves, sharpen my #2 pencils and start taking some notes. Also, I needed to reach back into the recesses of my mind and not only find, but dust off, Ohm’s Law, because we were going to need it to figure these babies out boys & girls!

To make a long story short, the bottom line in getting to the holy grail figure of 20 milliamps or below when one is incorporating a relay with an airspeed switch is to ensure the relay coil resistance is above 600 ohms minimum, which of course drives down the amount of current (using 12V power = < 20 mA) that can pass through it. Ok, so I got that down, plus the need to use a protective parallel diode, much as we do on our main power battery contactors.

After getting off the phone with Bob I just needed to take a breath and do some self inventory, of my relays of course. Sadly, the quintessential B&C-sold S704-1 relay (below), of which I have a few at the ready, have a relay coil resistance of 144 ohms. No good! I then had to go on the hunt for the proper relays on Mouser to find acceptably rated relays.

Moreover, the sticky wicket for a high-current-powered item like the heating element in the pitot tube is that relays that have high coil resistance typically handle lower current loads. Nonetheless, I have an order queued up with mouser, and will test out a few different relays. I also have an alternate design to stick with my S704-1 relay as the first line relay to power the pitot tube, which itself would be controlled by a much smaller second line relay controlled by the airspeed switch (AS003). (relay photo from BandC.biz)

With all my new found knowledge on airspeed switches, I quickly got it all annotated on paper by then doing yet another major design overhaul on my Lights Wiring Diagram. After ensuring I have everything identified that I need up to this point, I’ll pull the trigger on my mouser order in the next day or two.

Ok, the taxi light operations and airspeed switch incorporation really were the last 2 long poles in the tent as far as electrical system design that I had serious questions on. With the code cracked on both of those, I can move on to finishing round #1 on the Triparagon & avionics bay/nose components wiring. I’m sure I’ll have wiring questions on some of the panel devices and the engine ignition & monitoring component wiring, but that’s a ways down the road. Thus, I feel confident that I should be done with all these electrical system shenanigans over the next week.

Tomorrow I plan on really focusing on finishing up the Triparagon install.

A Long EZ Push

The Building of Long-EZ N916WP

Monthly Archives: December 2016