Intermission

Everywhere I take a nut off, I replace it with MS21042. Half the size, and it supersedes the default AN365 and AN363.

Just nuts!

And by the way, often times it's convenient to use a "grabby thingie" to start them.

Grabbie

Back to it

Set up the hardware stacks, crimped short lengths of wires into the terminals, hooked up the ground strap...

Starting to mount

...and finally, got to use my TorqSeal! I think this is the first fastener I have torqued to it's final state in this project. Milestone!

First dab of torqseal

Next, trimmed and crimped the ground wires.

Ground wires

And that was it! Two more dabs of torqseal on the bottom nuts, and installed all the plugs for the holes left over from removing old lines. I'm using AN-6 plugs here.. nice, light, and pretty.

Installed!

Why not top ones as well? Well, I have this pesky gutfeeling that I will hook up an adel to at least one of them to hold the main wiring harness to it. It's just too convenient a spot not to do it.

And to top it all off, did a couple of nice placards to remind myself of things :).

Placards!

Switch Anti-Rotation Holes

You have probably figured by now that I have a taste for misery, and for ranting about how miserable that or this was :). If you read a few notes in this Dear Diary, you will notice a trend - that I tend to come up with ways of making myself aggravated, very consistently and reliably.

Well, this time it was the "anti-rotation" holes for switches in the panel; and the plan was to drill them from the back side of the panel not quite all the way thru (yay, no access and contortionism again!)

Every switch, circuit breaker, and certainly, a dimmer, comes with a "keyed" washer to prevent it's rotation. That means you're drilling two holes - one for the appliance (switch, or whatever), and the other for the little tab that's on the washer.

Picture explains this better. Here is a little hole template I quickly drew in Solidworks, properly dimensioned, with washers from (left to right) the circuit breaker, switch, and the dimmer.

Holes template

See, Remo didn't have those "secondary" holes on the panel - so I had to drill them (especially for the dimmer).

But wait, you ask. If you drill holes, that will be ugly - a hole next to every switch?

Yup. Aha. Agreed! Though the nuts are supposed to cover them, they, I'm pretty sure, from my testing at least, wouldn't have...

No problem! Remo made the panel from 1/8" thick aluminum, and I needed maybe half that much for the tabs to go in. So the plan was to very carefully drill them just deep enough to house the tabs.

Made me a nice little set of templates...

Templates in the making

...out of a small piece of aluminum, drilled holes using my paper template, and cut them up...

Templates, cut up

...and cleaned up the holes and edges.

The plan was, to put a template like a "washer" around a switch/CB/..., and center punch the secondary, small, hole, thru it. Then, I'll have punch marks to drill, and will have to either get to them from the side of the plane, or, more likely, from the back of the panel while sitting in the seat and not seeing where they are while drilling, using a mirror to position the drill first.

Like I said, I have a taste for misery.

So there we went, punching the back side.

Center-punching on the back side of the panel

Click-clickity-clack.

Cling! Ding! Ding dang dong.. it sounded like a chunk of metal just fell off the plane and dropped on the cockpit floor.

!??!?@??!??! What the h... did I break?!

I crawled out from behind the panel and looked into the cockpit.

On the floor, looking at me, and almost smiling, was...

Placard!

...this. Remo's placard that went around the switches. Like so:

Placards - in place

Wait, wait wait wait. It came off. But it will be held back by the switches' nuts when the switches are in. And.. cover the holes! That means, I don't need to drill the holes from the back side and worry about punching thru (or not going deep enough) - I can comfortably sit in the cockpit and drill them from the front! All the way thru! The placard will cover them! In my search for misery, did I luck out?! :)

In retrospect, this (and the opposite side's) placard were probably not glued. No need - switches' nuts hold them just fine.

They were stuck because Remo probably installed them on top of the paint that didn't fully cure - and it just stuck to the backside of placards over the years, under the pressure from switches' nuts.

I stuck my nail under the opposite side placard, and it came off with a little force.

Ha!

Well, it was smooth sailing from there...

Marking from the front

... relatively speaking, of course. I still had to hold up the vacuum with my knee, and maneuver the sharp drill, making sure to be extra careful not to poke it into anything important (like, fabric on the sides).

Curlies!

All drilled!

The ones on the corners were annoying; but I already had the drill bit installed into one of my hex drill adapters - so a 90 degree adapter was not an issue. Didn't even need an angle drill.

Angle adapter for the side hole

Happy end!

Dimmer Pot

That sucker has 1/4" diameter threads; and all the holes I have in the panel are 1/2... Without some serious bushings, or other mods, or a new hole.. ugh.

Possible pot locations

I was hoping to stick it into the old "Master Circuit Breaker" hole (marked (2) above), but it was waaaay too big.

Looking around, looking around.... aha! Here's a number 8 or 10 screw plugging a hole! I can enlarge it and we'll be in business! (marked (1)).

Yep. Good luck, buddy. That was an even bigger hole that was plugged with a #8 screw in a countersunk finishing washer... hmmm... maybe that will work out for the pot too?

You know, drilling a #10 countersunk washer to have a 1/4" hole in it is... hard? Annoying? You can't really grip it in any manner without damaging it, you can't hold it in your fingers... I think I lucked out on my third try, with combination of a Unibit and light clamping of that washer in a vice.

With that re-drilled countersunk washer, the pot mounts just fine in hole #2. And #1 got plugged back :).

Compass Mount

Well, after all that excitement compass mount was almost anti climactic. I toyed with the idea of putting it into the panel (and relocating G-meter into a new hole I'd cut around where the ignition switch was - see, after having failed relocating Hobbs there, the idea of still making a bigger hole in the panel keeps nagging me :).

No good. When that much down, too much steel around it confuses the compass to the tune of about 30 degrees... No need to add extra problems in already a magnetically problematic plane.

So, top it was to be. The windshield will get in the way, but I really, really didn't want to take it off (~20 #6 screws and nuts in a tight spot is no fun).

Eyeballed the bracket alignment with the fuselage centerline and put it in the right spot...

Damn! Sharpie's too tall to get in there to mark the holes vertically. "Angle Sharpie Adapter"... hmm..

I know!

Angle Sharpie Adapter

A bit of disassembly and forceps do the trick ;).

aaaand, mark!

Holes punched and drilled, I added a bit of rubber foam under a portion of the mount to "eat up" uneven surface created by combing...

Mount mounted

...and voila...

Vertical card compass!

Side note to attentive folks: yes, I know I need brass hardware - those CSK washers and SS CSK screws are temp fasteners I used to test positioning. It will be brass, I promise :).

PS

... playing with new switch labels...

Labels

PPS

Oh, by the way, the best accompaniment (score? ;) ) for working on a biplane is...

... The Chairman, of course!

Diagram

I have updated the electrical diagram, version 2 is here.

• Main Connector is gone. I was convinced that reliability concerns outweigh the benefits of having it. Plus, I have very little precious room to work with.
• Physically, it's easier to hook up the LR3C Sense wire to a different spot - on the Shunt stud rather than to the Master Contactor/Starter Contactor jumper directly. It makes no difference, it's the same circuit - just a different hookup spot to it.
• I also fixed some typos, and cleaned up a bit.

Firewall Forward

I started trying things around firewall forward while figuring out routing and lengths for carb control cables, and continued afterwards.

Contactors and Beefy Wires

Contactors

It became obvious fairly quickly that I won't be able to use the nice B&C Starter Contactor because of it's mounting holes not being the same as a very common SS581 Starter Solenoid that was set up by Remo. Also, the way terminals were set up on the B&C Starter Contactor would have made them closer to the carb control cables. And, I didn't want to drill more holes in the firewall.

B&C Contactor

SS581 Contactor

So I decided to go with SS581-style and ordered one from Vans. While waiting for it, I used the old one just to mock things up.

And because it doesn't have the spike catcher diode, I had to get me a couple IN5400s, and soldered an extension lead to one of them.

Extension lead

The other leg will get a crimp ring terminal. I had to do that 'cause the diode leads themselves weren't long enough.

Battery and Starter Wires

Those are the thickest wires, and routing them is more complicated than the other ones. In addition, the battery + -> master contactor wire is the only wire that can't be turned off, and therefore needs to be very well thought out and as short as possible.

Here's something else, too. The Charger was set up to ground the battery to the motor. So far, so good - starter is by far the largest consumer in the electrical system. However, nothing was done to ground the motor to the rest of the airplane!

So the rest of the system was probably grounded via whatever metal to metal connections there were on the motor. Control cables and braided fuel and oil hoses? ;) Airbox bowden "carb heat" cable... I can't think of much more else.

Initially, I was planning to run a ground strap braid from the battery negative to one of the bolts holding the battery box to the firewall, but with fuel system components and control cables around, just couldn't figure out a good way to run it and support it. I had to end up settling for running it to the engine mount instead.

So the bottom line is, the negative 4GA cable is gonna go to the motor, and parallel to it a braid will go to the motor mount. I also figured out a clamp arrangement with some standoffs that will keep the wires neat and organized.

Beefy Wires - side view

Beefy Wires - top view

Negative leads and grounding

Oh hey, and I practiced my lacing on those ignition wires. One of my plans is to excise all the zipties I can get to, and replace them with lacing cord ;).

Laces

ANLs and Shunt

ANLs and the Ammeter Shunt will go to where no man had go... 'cuse me, to where the old Voltage Regulator was. Like this:

ANLs and Shunt placement

I will need to make a backplate for them to re-use the old voltage regulator mounts, and not have to drill new holes in the firewall. I used my Solidworks templating trick, and made me a nice template...

ANL template

... and a mockup (with material, as usual, courtesy of USPS).

Mockup backplate

The shunt is offset "down" due to the top hole in the backplate (which will have one of three holddown screws to hook up to the old voltage regulator mounts), and I couldn't use buss bar stock to connect the stud terminals on the shunt and ANL bases - if I were to do that, it would not let the ANL covers to come on. So, before doing anything drastic, I decided to check to see how it would look with the wire jumpers

Crimper

One side done

Second ring on the jumper

Done

On the firewall

I liked the way jumpers came out a lot, and will probably keep them that way. They do add just a bit of weight, but not enough for me to worry about.

Side Conduit

The Voltage Regulator and the Main Terminal/Fuse Block were to go to the Side Conduit running alongside the fuselage.

Rough component locations

I had to relocate the bowdens lower to free up some space. The Oil Cooler box on this plane is all sorts of weird, including a flapper valve controlled by one of those bowdens that closes up the airflow to it (which is not enough to begin with; being a 1.5" SCAT takeoff off of back baffle.. but don't get me started on that). That cable turned out to be too short when relocated - but I lucked out - Glenn had a bowden going to the Rotec TBI that I removed for "prime" function, and that bowden was plenty long. I'll trim it to final length when I'm done in that side conduit.

The brake tube was running inside the conduit, and I will have to relocate it to run below the conduit and be supported by adel clamps. For now, I unhooked it and used it to somewhat mock up the new run. Tube and fittings ordered, and tubing bender already here!

Fuse Block

I was gonna use a 20-position fuse block from B&C. Well, that didn't go too well.

Fuse block

Tight! I basically lose the whole top row of fuses with it. Not enough room....

After poking around the Internets for a bit, came to these nice fuse blocks made by Blue Sea Systems. Longest ones they have are 8 fuses, so I will need two (if I recall correctly, I have 13 fuses in the diagram currently, and I want some spare positions for later if I need them).

Blue Sea Systems fuse block

Much better! Plus, they use ring terminals rather than tabs - and while tabs are light and simple, I don't like them. Removing them is hard, and, when removed, the terminal loses a lot of it's grip. It's almost like an "assemble once" type deal.

Voltage Regulator

With how the wire harness is gonna go in that conduit, and with bowdens being where they are, the best orientation for the Voltage Regulator would've been "upside down", with terminal strip up.

Upside Down orientation

Damn you, the yellow sticker on the regulator! DAMN you! (hint: read it :) ).

Mounting it sideways, I'd have a line of rivet heads under it - which I didn't want to deal with.

Sideways orientation

And mounting it down... Down was annoying because of the clamp for bowdens and bowdens close there. That would also complicate wiring.

Down orientation

Upside down would've been perfect... except for that yellow sticker :). So, I decided to Hail Mary and asked nice folks at B&C about what they thought.

See, the problem is I know why they wanted the terminal strip to be pointed down. It's so that water won't get into the box in case of condensation accumulating on it. But I thought, maybe I can seal it somehow?

The answer from TJ at B&C was a resounding no. Right side up, sideways - but not upside down.

So I mocked up the right side up mounting...

Right side up mockup

Yuck. Yeah; it'd work; but it's ugly as hell.

The only other option would be sideways, but on "standoffs" of sorts to clear the rivet heads. I mentioned that to TJ, and he said that that could work, but I should check if I can access the voltage adjustment screw on the top of the box.

Damn it! I forgot about it. On the top of the box there's a plug over a hole that opens up access to a tiny screw to adjust buss voltage - basically, to fine tune how much volts the battery sees. Not something you do often, but you want to be able to do it.

But then, TJ mentioned that he saw the holes in the firewall and that might be the saving grace.

Bingo!

I tried it out again in vertical, now with mocked up standoffs

Vertical

With just enough aggravation due to bad access (mandatory in aviation pretty much), you can undo the bolt covering the hole in the firewall (this hole was left over from the brake line relocation), pop the plug on the voltage regulator, and just have enough access to the adjustment screw.

Adjustment screw - firewall side

Adjustment screw - conduit side

We got ourselves a winner, I think!

Panels

Hobbs

Hobbs was on the front panel, probably because of space issues on the rear panel.

Hobbs meter

"Aux Generator", eh? :) (read what the gauge says).

Well, I had this unsightly hole left over after removing the ignition key switch...

Unsightly hole

... and I thought, maybe I could put the Hobbs back there?

My initial tests with one of the 2 1/4 gauges I have removed seemed to have been okay: there was just enough room in there to get another 2 1/4 gauge in.

So, I got me a very nice panel punch that could make a nice, round, clean hole in place.

Instrument Hole Punch

Well, next was to remove the Hobbs from the front panel. That was an hour of contortionism. The Hobbs is held by an aluminum backplate and four nylock nuts, so I had to have a wrench over them the whole time. Oh, the screws are way too long BTW, so taking all them out took about five times more turns than it should've, while I was wondering if my wrists will take this much flexing, twisting, and bending any longer.

Mounting ring

This is a pic from the fuel quantity gauge held in the same manner, but here he's using brass flat type nuts that you can hold with your fingers. On the Hobbs, it was nylocks.

Anyway, I got it out. And then, started setting up for punching that hole. Removed VSI to give me a bit more room to work with.

I tried to reconstruct exactly what happened next in my memory to write it down here, and could not. I was basically fiddling, checking clearances, making sure I'll be able to hook up the punch and center the hole, have enough room for the mounting ring in the back and clear everything I had to clear, when I discovered that...

The Hobbs was not a standard 2 1/4 inch gauge - it was a touch bigger. So the hole that I would've made would've been too small for it. And that if I punched the hole, I would've been just left with a bigger hole and nothing to put in there.

Damn, damn, damn! Damn you, assumptions that every "small" gauge on an airplane is 2 1/4!

And I had the expensive punch that I had no use for :(.

Oh well. Thanks God I actually did not do it - only to have a larger hole to plug up. I guess, that Hobbs is (thru more contortionism) going back to the front panel.

As they say, Le Sigh.

Switches

Finally, something fun! I put in the switches to play with layout. Here's the first, and (after playing with moving things around and pretend turning them on and off), the best, layout.

Left side

Right side

On the right side, I might clump the switches together, or leave them as on the picture, to "match" the placards (those are left over placards from fuses that were there in the old electrical system). The little brass knob on the right is gonna be panel lighting control pot.

Compass

I am going to replace Pilot's whiskey compass with a vertical card one - yes, I am directionally retarded :) It's not that expensive a mod in the grand scheme of things; and is the only directional instrument available to pilot on this plane (no DG ;) ).

It's a bit taller than the whiskey compass, so I'm playing with different mount locations. I think this is what it will be; with shock isolating rubber pad under the mount where the gap is at the moment.

Compass

Fuel Sender Crimps

One of the evenings, I wanted to make sure the Fuel Gauge was still okay (I had a suspicion that it wasn't - turned out to be false).

But first, I wanted to clean up the wiring on the tank sender.

Before

Before

The terminals on it are "automotive" style, without insulation support.

After

After

There. No zipties, good terminals, and marked :)

The Crimper

Normally, crimpers for large size terminals are super expensive; but Harbor Freight, as usual, sells a hydraulic crimper with large dies for just about fifty bucks.

Here it is, in it's full glory.

Crimper

Dies

Technically, the way it's designed is it's supposed to produce these nice hexagonal crimps. Or at least, I think that's what they were trying to do.

But those familiar with crimpers know that the key is in good dies; and that's were most of the money is. Damn, "regular" stripping dies for StripMaster are what, $10; while milspec dies are what, $150? Now; of course there's diminishing returns there - in the case of StripMaster, regular dies work just fine for most applications.

Here's the problem with HF Crimper dies. The holes in them are severely undersized, which makes them produce "flat", rather than hexagonal crimps. We can't know if this is by design. What I tried to do is to research what others are doing, and to run a few "is this a good crimp" tests.

The Test Setup

I was crimping chunks of 8 AWG MIL-W-22759/16 wire into AMP Battery Terminals.

The Terminal

After crimping, the terminals were hacksawed in the middle of the crimp, and polished to see if there were any voids or visible wire strands. A good crimp must be "gas tight". In other words, all the metal has to be pushed together hard enough to become a single piece of metal for all intents and purposes.

Using 8 AWG dies

For baseline, I used the HF die marked for 8 AWG.

8 AWG die / crimp

8 AWG die / crimp

As you can see, using the "nominal" die produces this weird, flattish-with-a-bulge crimp. What's worse is it adds this strange "jog" to the terminal lengthwise, and scrapes the metal inward where the crimp starts. That's lots of stress risers.

8 AWG die / cutaway

The crimp quality is good though. There are a few specks of shavings I didn't clean off - those are not defects.

Using 6 AWG Dies

I went next size up, to dies marked for 6 AWG. That produced the same crimp as for 8 AWG, but with "wings" being thinner - almost paper-thin. I also didn't like how it mangled the terminal even more.

Somebody online mentioned that they rotated the crimp 90 degrees and did it again to "push the wings in" and I tried that.

6 AWG die / crimp

6 AWG die / crimp

I think the resulting crimp, while tight, is too rough to be acceptable. It almost feels tortured.

6 AWG die / cutaway

Inside though, it's all nice and compressed.

Using 4 AWG Dies

Finally, I tried 4 AWG dies.

4 AWG die / crimp

This crimp almost looks good. The jog is almost not there, and it has nice hexagonal shape. "Wings" are almost not present.

However, the dies closed fully and it felt to me that the metal was not compressed enough (I recall the resistance I felt in the crimper doing the previous two tests, and the resistance I felt on this one was much less).

The cutaway confirmed that.

4 AWG die / cutaway

Those imperfections on the cutaway are voids left from not enough compression force applied.

Conclusion

Well, it's a sad one really. If you want to use the HF tool, then you probably should use dies that make those "winged" style crimps (like the one produced in my first test), and suck up the jog and other imperfections.

I have posted my findings on AeroElectric list, and the conclusions seems to be supported - the dies are horrible, and to make them real good one would need to rework them significantly.

• Main thread
• Sub-thread one
• Sub-thread two
• Sub-thread three

Or, alternatively, just solder them (here's a nice howto by Mr. Nuckolls) , which is what I am seriously considering.

Update - October 2019

After trying and failing the soldering approach, I have devised a technique of using this crimper to achieve good results. Musings linked in the previous sentence, and here's the jist:

• Given wire gauge of, say, 6
• Use die 2 sizes up - so, die marked for #2 wire
• Put the wire in the terminal. Start by squeezing the terminal turned 90 degrees (so "side to side" rather then "top to bottom"). Just give it a gentle oval shape
• Now, turn it 90 degrees and squeeze until the jaws close
• At this point, you will have a somewhat undercrimped joint, as I described in my notes on the crimper; but it's shape will be a perfect hex.
• Now, go 1 size "down" (so, dies marked for #4 wire). Squeeze.
• Stop when you feel it's done shrinking.

Pretty!

The New Wiring Diagram

I have posted it in PDF over here.

Wire length / drop / load calculations are in the Excel spreadhseet over here.

• The design is based on Figure Z-11 from AeroElectric Connection by Bob Nuckolls, with the following tweaks:
  • I'm using the B&C LR3C Voltage Regulator, so it's wiring has been incorporated
  • I dropped the Endurance and Main Battery busses
  • I have tweaked the starting switches circuit, main buss feeder, and how ammeter is hooked up - see below for discussion
• The diagram is laid out to generally clump the components together as they would be on the airplane. It initially might seem convoluted - but it has a certain flow to it matching the locations of components. Start in bottom right corner for battery/starter/alternator circuitry and go counter clockwise - this will effectively take you "thru the airplane" as the components will be laid out; roughly

Review Items and Commentary on Specifics

Starter Circuitry

My current take on my Starter and Mags circuitry is this:

Starting and Mags Circuit

This is a deviation from Z-11, with both switches having to be in the momentary up position for starter to engage. I like this better for two reasons:

• It makes the act of starting the motor more explicit
• It returns back to correct "running" position automatically

I need to test the ergonomics of pressing up a couple switches together. If I don't like it, another alternative would be to replace the "Right Mag" switch circuitry from -5 to -1: making the top position on it non-momentary (as noted on the diagram). This will reduce the "user-friendliness" but will still keep the explicitness, especially with my using pull-to-unlock switches from Honeywell.

Main Power Distribution

The Charging and Buss circuitry excerpt below:

Power Distribution

Note that:

Shunt is set up to be in the "battery" lead. I like "battery lead" style ammeters, showing charge current on the 12-o-clock-plus segment, and discharge current on the 12-o-clock-minus segment.

Note that the buss feeder wire is protected by a slow-burn 35A current limiter. In Z-11, that wire is not protected at all. My reasoning for this decision is that this wire is relatively long on my plane (around 4 feet), since fuse block is near the rear cockpit. I wanted to protect it.

One area of concern here is that in the event of alternator short, the Ammeter Shunt will be a part of the alternator circuit that will see a lot of current while the 40A slow burn opens up. My gutfeel says it should be able to handle it, but I am not sure. At any rate, figure Z-11 has the same setup with shunt on the alternator's B-Lead.

Voltage Regulator Field Supply Circuit

The circuit looks like this:

Field Supply Circuit

I copied the AeroElectric's figure Z-11 wire gauges here. In Z-11, everything upstream of Breaker is 18 AWG, and everything downstream is 20 AWG, but it's not explained why.

Is this driven by a requirement to ensure that fuselink survives the short in the circuit in case of crowbaring, and the breaker pops first, w/o endangering the fuselink much (18 AWG allows for 22 AWG fuselink instead of 24 AWG)?

Components Location and Main Connector

Here's a relative diagram of components location, that is necessary for explaining what Main Connector is. Click it for larger version.

Key component locations

Note that logically, the way one would wire this airplane would be to pre-wire switches and other items that go into the pilot's (back) instrument panel with long pigtails, then install the switches, and tie down wiring behind the panel. Then, the pigtails can be connected to fuse block and loads.

Some of the load wires already exist (lighting for example), and they will have to be spliced to wires coming from switches.

I have decided instead to locate a kind of "Main Connector" right there near the Fuse Block. A wire comes off of the Fuse Block, goes to the switch on the panel, then switched power is returned to the "Main Connector". Load is on the other side of Main Connector.

This serves a couple purposes:

• Create a logical "access point" into the main wire bundle, for reading labels, tracing wires later, and such
• Simplify installation process
• Connect to existing load wires that are not being replaced

For now, I am thinking about using Molex 0.093 pins in two housings (I have 13 circuits total to connect via this thing, and want to have room for further expansion). I would love suggestions here. One of the requirements is that it should be easily workable with a multimeter for tracing / testing purposes (I technically could've used D-Sub here , but am not due to this precise reason).

Wire Marking

I like marked wires. I used to be a networking guy, and I was very meticulous about marking every single wire in my cabinets, so that I knew exactly what was plugged in where.

It took a bit of upfront time, but saved a bunch of it later on.

So naturally, I was planning to do the same on the Charger, and, more importantly, make it look professional.

Thanks to living in this day and age, that is simple. No, I'm not gonna pay someone to laser etch my wires - that's a cop out :). It's like paying someone to paint your plane.

Instead, I have researched and found a perfect label maker - Brady BMP21 (not including a link here because it will probably go dead after some time... just search for it). This thing has 3:1 heatshrink tube cartridges.

The proverbial coupon

Prior to shrinking

Shrunk!

Fusible Links

Every wire must be fused at the source. Well, almost every :). We don't fuse a couple wires like battery - master contactor: but this is an exception rather than the rule.

Most wires are fused on the fuse block at the main buss. But some wires are impractical or impossible to have hooked up to that. Think ammeter shunt wires as a classic example.

For those, most people use bulky, ugly, and generally eww-y inline fuses. But there's a better option! Enter fusible links.

The idea is simple: use a short length of wire 4 gauges smaller the wire to be fused. So if your wire to be fused is 20AWG, you would do:

Source -> 24AWG -> 20AWG where the 24AWG segment acts as a fuse. The idea is, in case of a short, that piece will burn first.

So, I wanted to convince myself that that will work fine for me.

Initially, me and my ham neighbor tried to use his ~30 amp power supply to do it. No joy. The best we could do is 22 amps, and (imagine that!) 24 gauge we were trying to burn held up to the abuse with no sweat at all! I could even hold it in my fingers. Yay, milspec wire!

So I decided to go rough. I do have a discarded old battery, after all. It was time to burn some wires with it.

Here, the red wire is 20AWG, and the black wire is 24AWG. Using crimps for quick setup.

The link

The hookup

Boom!

It burnt real quick, in less than a second, and the protected (red) wire barely got hot (I was holding it - that was a part of the test). Yes, say that I am unscientific all you want - milspec wire holds up to 150C, and I can't hold up to 150C. The 20GA wire got barely warm - which means it won't cause any problems in a bundle.

It worked!

Now, it was time to set up a real one - to make sure that when the "fuse" wire burns, it doesn't damage anything.

B&C sells very nice fiberglass tubing covered in silicone for exactly this purpose.

I also soldered the fuselink in this time - I wanted to see how well will the solder splices hold to the temps.

Soon to be splice

24AWG spliced into 20AWG

Note here: I know that in reality, the thin 24AWG wire will be the first in chain; here I'm just splicing it in the middle of 20AWG segment so that I can cover both ends. In "production" fuse links, the "source" end will be a ring terminal, and the fiberglass sleeve will go over it.

Sleeve on

With heatshrink

Ready to go!

Boom! Or not? I thought it didn't work, frankly. I didn't hear anything. I didn't smell anything. I actually took my multimeter to make sure the continuity wasn't there - it wasn't!!! Wow. The fiberglass sleeve contained the micro-explosion really well.

I took it off to inspect.

All burnt up wire

The fiberglass sleeve showed no signs of damage.

Great success!

I will need to play with different sizes of heatshrink and probably will use the glue lined strain relief kind just to support everything well, but hey - this worked very well indeed!

Load Measurements

Prior to ripping the old wiring out, I wanted to take some real life load measurements with various things turned on, so that I don't get any nasty surprises.

But this plane has no ammeter... damn. I searched around, and found this little doodad:

Hall Effect ammeter

Very nice. It basically measures current on the wire passing thru this big white ring using Hall effect. Very cool! No need to splice into the battery leads and install a temp shunt.

So, I rigged it up and took some numbers.

Rigged up

• Master On: 1.5 amps
  • Includes: Master Solenoid, and a couple of gauges
• Fuel Pump: 0.2 amps
• "Radios" switch (turns on engine monitor, and power to radios: turning backlighting on them): 0.8 amps
• I-Com Radio, Transmit: 2.6 amps
• Intercom: 0.1 amps
• Transponder: 1.1 amps
• Smoke Oil pump: 2.2 - 2.6 amps (high on startup)

So couple interesting things here. I think the x-der number is too low, but it wasn't being interrogated, and I can't make it be interrogated without flying the plane or using a transponder tester which I don't have. Also, Master On is too high seemingly... Will need to double check later and isolate things (master solenoid, hobbs, voltmeter, voltage regulator, fuel gauge) if I care enough - I don't think I do. Also, fuel pump is too low seemingly. Need to double-check the spec.

And then, I could not turn on the Turn-Slip Indicator...

Turn-Slip Indicator

Sad, sad indicator... see, it's long. And it's wire connector is sticking out. And it's right behind the front seat's headrest, and there's just not enough room for it, and the connector.

So whomever put it in... did this:

Sad, sad wiring

It's hard to see; but basically, those wires are bent "down" at a very sharp 90 degrees angle. Notice how he just used pins without the actual connector. The distance between them is tiny! I am surprised they haven't shorted over all these years. I really am.

Initially, I thought the gauge didn't turn on because that wiring was all bust up, so to test it, I decided to pull it out.

On the bench

I cut off the wires with those pins on them to hook it up to my testing battery... hmm.. but I needed some leads! Well, I was gonna make a bunch of various test leads - so this is as good a time as any! Man, I love soldering...

I long decided to make a bunch of leads with "passthru" banana plugs on one end, and something (a crocodile clamp, a battery clamp, a ring terminal) on the other. This way, I could mix and match, and plug them into my multimeter; daisy chain, and have multiples depending on what and how I needed to hook up. I had all the bits (clamps, crocodiles, banana plugs), and even got a roll of very nice super flexible silicone coated probe wire.

Components, and the battery clamp crimped on

Release the Soldering Kraken!

The banana plug pin

All hooked up

The gyro in the gauge didn't start. Damn.

But I had resistance between + and -. And I had voltage! Hmmm..

Second time I hooked it up, I saw a bit of a spark when I put the positive clamp to the battery, and heard something.

I spun the gyro with my finger.... it spun up!

Well, well. So that gyro "froze" in a bit... Yep, it was hard to turn over with a finger - no doubt a small motor in there had a hard time!

I probably "cleared it up" a bit when turning it over with my fingers - but that won't last long... damn.

Are we looking at the overhaul for this thing too now? Sigh.... Maybe I can find parts to do that myself, but not so sure about that.... It's not common for owners to overhaul their instruments - they're precision clockwork, after all...

Oh well.

And I will have to figure out how to solve that wiring problem with no space to hook up the right type connector. I am thinking along the lines of maybe routing a wire from inside of the gauge down thru a hole I'd drill, a grommet it it, and covering the whole business with with some sealant or something, so that the dust doesn't get in. we'll see. Need to ponder this a bit more.

PS

... and here's what happens to airplanes that aren't flown enough...

Dinner for someone...

Interlude

Battery Contactor is an interesting point here. Normally, one terminal is connected to the "always hot" side of it (basically, directly to the battery) and the other goes to the Master Switch. Master Switch turns the Battery Contactor on by grounding that wire, providing the negative side to the circuit. It's a safety thing. If that wire breaks, it'll either turn the electrical off (open circuit), or it will keep it turned on (short to ground). That's it.

But, one of the terminals on the Battery Contactor was grounded... that means, that the other terminal (the wire coming from the Master Switch) must provide positive side??? Huh? But where does it get it's power from?

Tracing

So to tracing we went. I spend maybe 10 hours trying to find diagrams and understand that alternator and voltage regulator hookups.

And me tracing it spelled my doom.

The Diagram

Now, I didn't trace the rest of it. Just the main distribution system. That was enough.

Shall we?

The current main power system of the Charger

Yep, the diagram is missing the main power buss. It's dangling off of the same spot where everything else that's interesting is - the Battery Contactor (marked MA RELAY) <-> Starter Contactor (marked STARTER REL) link.

So let's see what we have here.

• Lots of unfused wires. Do you see a single fuse here? Nope. That's because there aren't any. All the fuses are further downstream, off of the main buss.
• Voltage Regulator has this extra wire running to / from cockpit that isn't really necessary and could've been kept on the hot side of the firewall (terminal 4 wire)
• Alternator field broken at output (F->ALT) rather than at input (battery -> terminal 3)
• And the best part? Always hot wire that you can't turn off between the battery and the Master Switch to turn the Master Solenoid on.

That last bit bugged me. I couldn't find the damn thing. Even before actually tracing it, I knew that if the Master Solenoid is switched on the "hot" side, it needs to get the power from somewhere, and that only could be battery. But I didn't see any wires on the always hot side of the Master Solenoid. Only when I traced it, I actually traced the physical wire to where it goes, and then found it. It was so tucked behind the battery -> Master Solenoid wire that it was invisible:

This little !@#!S@#....

Oh; and by the way, the Master Switch is the only switch that's soldered in, and w/o any good insulation around the terminals, and over-stripped wires. So that's just waiting to short, and the magic smoke that'll be let out behind the panel when that shorts can't be stopped (always hot wire, remember?)

Master Switch

The Wires

So I kinda went backwards here; but I thought it'd be easier to see the diagram first.

Let's see.

Most of connections are made on this very nicely marked terminal block:

The terminal block

All the switched power comes out there, and every wire is marked. This actually helped a lot in tracing. This block is on the side of the plane, right next to the front hole's backrest.

You know what threw me off the most with that damned always hot wire (I ended up tracing it physically)? It's how it's hooked up.

Yep, it is hooked up to that terminal block. To the terminal... that is marked.. (drumroll).... "Master Switch".

Wait.. this actually makes sense... But where's the "return" from the switch?

Ah! It's the wire that's marked.... drumroll... "Fuel Gauge"!

So really, let's look at what's going on, shall we? Zoom in the image below, it's annotated.

Untangled

So let's see. We've got this bundle of wires, a lot of which are not fused, and one of which is always hot.

The Main Buss wire is the thickest one (10 gauge maybe?) that's not fused between this buss bar and the source (engine compartment).

Oh, did I mention that this buss bar is on the side of the plane near the rear instrument panel (so that 10 gauge run, and the rest of the harness between firewall and the panel is about 30 inches long)?

What else do we see there? Oh! The two little 1/16inch thick aluminum lines carrying.. fuel pressure (and oil pressure).

Shall I say more?

Shall I say that there's a fuel tank in between the front hole (passenger) and the firewall?

That the wires run along between firewall and rear cockpit along that fuel pressure line (to fuel pressure gauge)?

That if one shorts to this very nearby fuel pressure line, it'll burn a hole straight thru it, and then ignite the gas that'll start coming out?

Yep.

Can I fix all of that?

Sure. But rewiring will be much much easier, because I have to touch pretty much everything. Re-running half of individual wires in a bundle is much harder than re-running them all.

So, I made a decision to rewire the plane... Sigh. Looks like I won't be flying for a looooong time.

Oh, and tell you what. Tracing wires on a biplane is dangerous. I ended up twisting my knee and pulling a muscle while trying to get behind the panel so badly that I couldn't walk (or sit) for 2.5 days :(.