[79FT]: Building Things
|On:||Jul 26, 2020|
|In:||[Chickenhouse Charger] Electrical Rebuild|
|Tags:||6781G, MA5 Charger, electrical, soldering, fwf, panel|
Well, damn. With almost a year (no, more than a year!) of my being a caretaker of the Chickenhouse Charger, I finally was about to actually begin what I have started - which was, putting in my wires.
I decided to start at the switches, and run from the panel forward. Some wires will terminate at the fuse blocks (power feeds), and some will go forward - to the front panel, voltage regulator, and firewall forward.
Then, I was planning to run a few wires backwards - the ones that were pre-terminated on my transducers (fuel, oil pressures, oil temp, and mag pickup for the tach).
Immediately, I will admit: that was a mistake. While the harness turned out alright, it could've been much neater - if I ran in one direction. I could've made sure the whole thing is wire to wire and perfectly clean. So I should've run front to back, because my pre-terminated wires all "started" upfront.
In other words, prop to tail. Well sigh. Next time. On the other hand, this approach would've made terminating switches at the panel a nightmare. That was, initially, the reason why I wanted to start at the panel - so that I'd pre-attach wires to switches, tie them up, and then trim them at the other end.
At any rate.... Shall we?
Couple things to knock off before I started wiring was to complete the back panel. One thing that was left was the compass correction card bracket. No problem, drilled and tapped a couple holes for #2 brass screws.
Here's Mr. M. installing it:
Compass Correction Card Bracket
The other one was the inertia switch for the smoke system. Glenn had it in for "safety": in the event of a shock (crash?) the switch breaks the circuit. I am.. not sure why he would have it, but he had it.
I considered not putting it back in, but what the hell.
Here's the switch:
The problem was, it sat tightly between other switches in the panel. With old layout, that barely worked; but with the new layout, and Honeywell double throw switches, the connector plug was getting in the way. So I had to resort to some vandalism. :)
Removed the connector and the shroud
Epoxy around the tabs
And the switch fit nicely. Here it is, tucked between the switches. You can see how that connector would've interfered.
Shock Switch between other switches
The final prep thing was enlarging two holes for ground points to #10 and cleaning the back side up to expose nice shiny aluminum.
Now ready, I decided to install the switches first, and then wire them from the back. I needed a couple short jumpers though to connect them, and to set up some wires to be the exact length. That'd be impossible with switches installed in the panel (too little access), so I set up an old placard plate, installed switches into it, and worked on those jumpers and terminations on the bench before moving them to the airplane.
Switches on the bench mockup
Here's a couple more pictures of soldering and terminating fun pics:
Warning light socket
(that flux got cleaned off, of course).
Tagged and shrunk
The heatshrink I'm using for these and in fact all my soldered joints is special strain relief kind with glue in it, specifically, Raychem SCL. It's 3:1 and it is very rigid - almost completely rigid. It definitely adds more support than the typical PIDG crimp used everywhere.
Pigtailing shielded p-lead
Finished with rings, HST, and tag
And then, switches went in, got tightened and straightened up, and I started running the wires.
Somewhere in the middle of running the wires
I think it happened when I was yet again sitting in the cockpit, clicking the switches and enjoying the very well done Honeywell's action.....
Engine starter engaged position - note that I can hit the starter and hold the throttle with the same hand
...when it dawned on me...
My three most important switches, L and R Mags, and Master, were set up with lockouts - you couldn't turn them on just by clicking them, instead, having to pull the lever first to move it to the "on" position. I mostly did that to protect from accidental too playful a kid in the cockpit.
But they weren't locked out in the "on" position!
Why is that important? Well, the Smoke and the Fuel Pump - the most operated switches on this plane - are right there. Note how their levers are shorter? If I accidentally hit the longer levered Master, or a Mag, switch, that would turn it off - with me potentially shutting down the motor. While a remote possibility, improving the situation would amount to just replacing the switches to the ones with lockouts in both on and off positions.
I don't know how I missed that when designing the original setup...
I decided to do it.
So out came the switches, I had to un-wire the terminals from the back. In went the order for three new switches with now correct lock-outs.
About a week later, I had them, and could proceed.
With left side wired up, I could tie it down. Mind you, access there is tight and from all kinds of weird angles :).
Tying left side
Some of those knots I did from the side. Some I did while sitting in the cockpit, using mirror as reference
Look in the mirror!
Then, some "extreme soldering" to extend the panel lighting wires, that turned out to be a hair too short.
For those lighting wires, and for the turn coordinator, routing took some fiddling with. My initial plan would've had them rubbing against the sides of the gauges, and I decided to bring them "out" and away - that's why I had to extend them, by the way.
Lighting, and turn coordinator wires, test-tied
Note no padding on that pitot line: this is a temp, "sizing" pass: I am yet to finish assemble the back panel, and will add the right padding then.
The right side of the panel was much easier - it held much smaller, and simpler circuits, for lights and turn and bank.
You can see the beginnings of the ground strap to bond the panel with the "side conduit", holding the fuse blocks and being one of the grounding points. In my original design, I had firewall, motor, "side conduit", and panel, as ground points - all bonded with those straps.
Here's the right side:
and the bonding strap
Panel bonding strap
(the bonding strap got enclosed in super flexible heatshrink just for neatness: this is a fit-up picture).
I also had some fun with ADELs right where the wires turn from the "side conduit" towards the panel. I had to clear and negotiate a couple bowdens, and the engine monitor harness was unwieldy.
I think that took a number of hours, just trying various setups, the final one that I really liked was this:
Engine monitor and carb heat bowden.
I replaced all the ugly zipties with lacing, of course :).
Meanwhile, on the outside, to keep the wires nicely separated, I spread them out in kind of a "fan" in the order they ran, back to front:
A day later, I replaced the tape with a comb. Yep, a cheapo $1 comb :) Worked out great.
And finally, before committing and continuing, I checked each wire for gauge, and proper circuitry.
With all those wires sticking out, it was now time to start figuring out routing in the side conduit. All the wires that had to go forward had, well, to go forward.
After lots of fiddling, I ended up with this:
Initial stab at the side conduit routing
I had to clear all the brackets, and other sharp things. Ended up adding a couple more ADELs (and drilling holes in the conduit to accommodate). Also, reused some existing holes, made a few standoffs for ADELs and such.
Another angle on the side conduit
And that was it for now. Now, all the other wires needed to join the main harness in the side conduit.
The most interesting piece in it was a Westach tach, that fed directly off of a P-Lead and required a .25A fuse. Glenn used a 1A classic glass fuse, but I decided to do it right. See, the thing is, if it fails "short circuit", that'd turn off the mag - I guess that's why the fuse is in there.
The tach would get another 20GA shielded wire, just like a p-lead, and I decided to join it to right mag's p-lead at the magneto - instead of splicing it into the p-lead running front to back in the side conduit.
But, back to the fuse. I figured, I'd build it into my connector that hooks up to the tach. Then, if blown, the connector could be rebuilt. Yep, it's more annoying than a regular replaceable fuse, but that circuit is not critical, and I had no room for a "regular" fuse block or holder.
So I got me a "legged" .25A fuse with a massive voltage rating (I forget what it was, but definitely above what a mag makes), and hooked it to a regular Molex pin.
Finished with SCL, it's encased in a plastic tube and is not moving anywhere. There's two layers there, actually: one around the fuse and the pin, and another around the housing and the inner layer.
The final connector got set up like this:
Inline fuse and connector
... and it goes on the tach like this:
On the tach
The lead is just a regular pigtailed P-lead, of course. Notice how I like using SCL around individual Molex pins for added strain relief - that's because I can't produce good Molex crimps that I like; and I end up post-soldering them in addition to crimping. That strain relief ensures that soldered joint is firmly held immobile. Takes a bit of extra time, but I actually like that better than straight Molex crimps.
The rest of the front panel wasn't interesting, just annoying. There's only three circuits there: nav lights wires from the left wing run along the back of the panel to the right side where the conduit is, and then there's hobbs and tach, and that's it. It was just very annoying: with very little access, not being able to see things, and, being in the front hole, having to climb out and in every time I needed a tool I forgot to put close (when in the back hole, I can roll up a cart to it and have all my tools there).
Mirror was absolutely required.
The only way to see things
I will admit to asking my dentist right around this time if he had a trick up his sleeve for this kind of mirror work. Of course, he said. Practice. Lots and lots of it.
Okay, so the front panel got done, and it's wires merged with the main harness.
Front panel sub-harness joining the main
There, see, it's that small bundle going up and disappearing from view right in the middle of the "conduit"? That's the front panel sub-bundle.
The final set of wires to join the main harness were all the wires coming from the firewall side - mainly, transducers and other instrumentation wires, but also a couple wires for the voltage regulator.
This was precisely when I realized the mistake I talked about in the beginning - and ended up with less neat, and more tortured harness. Oh well.
I started up front, trimming and terminating my fat wires for the starter and alternator B-feed. Some more extreme soldering (to cap them), this time with a torch.
More extreme soldering
I tied up, and clamped the fat bundle to the motor: and apparently, didn't take a single picture.
Then, I had to figure out the diode for the Starter contactor - first of, it needed longer leads. There, instead of soldering, I used small barrel crimps from Molex along with heatshrink (I do use them where soldering is impractical, and I decided not to have soldered joints FWF).
Diode with leads
And all enclosed
And then, a simple ADEL to hook it up and hold it
Diode all hooked up
And then, the ammeter shunt, and the sense wires. Those needed fuselinks - in liew of an in-line fuse. Simpler, and cleaner this way.
I tested them a while back, and am confident they'll work.
First, we take a wire 4 "gauge steps" thinner than the fused one (so 24GA for 20GA fused, etc). That goes into the "source" terminal.
Beginning of the fuselink
Then, we hook it up.
Hooked up to the protected wire
Then, some heatshrink over the splice, for strain relief.
Then, a bit of fiberglass sleeve to contain the "fire" when (and if) it does it's job, as in, burns thru the thinner wire that acts as a fuse in case of a short.
A bit of marking too. And a "cap"
Capped and labeled
And finally, a couple knots to hold the sleeve better.
And finally, I finish installed all the engine transducers: pressures, and oil temp; and routed all their wires back into the side conduit and thru it back to the cockpit, adding them to the main harness. And that was that, for now - I plan to terminate them later.
I got rid of the belly strobe on the plane, because it was too heavy and too.. useless. Wingtip lights are gonna be the SkyBeacon and SkySensor from uAvionix (my ADSB mandate compliance :) ), and they have strobes: but they're not visible from the back. So I decided to replace the tail nav light with an LED nav/strobe.
Problem number one: no ground wire going to the tail light. For whatever reason, Remo decided to basically use the fact that the tail light is hooked up to the rudder with a pair of screws thru sheet metal of the rear rudder bow... I don't even want to begin to think what the ground path would be: hinges? control cables?
So, I needed a second wire.
Problem number two: it had to be one neat cable, and it had to be of a smallish diameter (Remo had an old 20GA wire, which is thicker than modern 20GA tefzel wire).
I decided to use a chunk of 20GA shielded - same ones I used for p-leads. Technically I guess you're not supposed to do that, but it's very far from all the antennas and I'm crossing my fingers that it won't create too much problems. Thickness was spot on.
So, I soldered the new piece to the old wire, and fished it thru using old wire as a pull. That part was scary - if that didn't work, I would've had to cut holes in the rudder to get a new wire thru.
Fishing a new wire thru
The tail light shipped with a small Molex. Why not?
The other end went onto the light, and everything got hooked up
All hooked up!
On the other end (on the tail fin side) the wire went into a hole on the inspection cover, and had to join the wire coming from the front. And I had to have the ground there. You can see that area right behind the elevator on the "fishing wire thru" picture.
Problem number three: nothing to hook up the ground to in that area. The only option I figured out was to use one of the rivnuts that are attached to the tabs welded to the frame, hoping that there's no corrosion there between the aluminum rivnut and steel fuselage. I figured I'd use a way too long a screw thru one of the rivnuts when attaching that inspection cover, and then pull the ring terminal onto it, and secure it against the back side of the rivnut with a nut and a washer. Ugly? Yes; but I didn't have any more options. Really, the right way to do that would be to run two wires from the pilot panel all the way back, but.. I'd have to start cutting fabric for that.
So, I attached the positive to the wire that was already there, terminated my ground, hooked everything up, hooked up some power, and...
A bit of debugging showed that... ground was the problem. Damn! I picked the wrong rivnut, I guess - it had corrosion. The one right on the other side though showed the right voltage when measured against the positive lead, so I just moved everything to the other side, and...
Let there be light!
At this point, the main harness looked something like this:
Main harness: complete, but not terminated
Now was the time to go thru it, cockpit to firewall, and terminate all the fuseblocks, and tie and zip everything up.
First, conduit, cockpit side. Lots of crossing things, lots of padding for bowdens where they cross the wires (I used the right sized vinyl tubing from my local friendly Aerospace Depot, and lacing to tie it).
Engine monitor harness got covered in tube for quite a distance - there was no way to keep it off and not rubbing on the conduit.
Cockpid side conduit
Fuse blocks got their placards. No, Mr. D., I am not doing brass placards again!
Fuse block covers placards
And then, slowly, methodically, every power wire got it's ring terminal. I added a bit of a "service loop" and used a ruler to try to keep each next wire exactly the necessary amount longer to reach the next terminal screw... Didn't work out too well, but close enough.
Tied up and hooked up
Another side got the same treatment, and then...
Did I just strip a terminal block hole?? Yep. I did. I blamed a bad block and definitely, positively, absolutely not my overtorquing the screw. Nope. No overtorquing. For sure!
So, had to get a new block. They're $35 so I figured I won't try to repair this hole to use an upsized screw....I'd spend more money on shipping small-headed #10 screws (the screws in the terminals are #8 but with small "oval" rather than "pan" aviation style head, so I'd have to get me some decent screws from McMaster.. by the time I'd be done, it'd be close to those $35).
So, fuseblocks. From there, it was just turning everything pretty.
Both fuseblocks done and tied
The whole thing
Sorry, couldn't resist doing a "before" picture.
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If you’re ever faced with a forced landing at night, turn on the landing lights to see the landing area. If you don't like what you see, turn 'em back off.
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