[79FT]: Building Things

FWF, Side Conduit, and Panel

...messing around trying things


On: Sep 08, 2019
In: [Chickenhouse Charger] Electrical Rebuild
Time logged: 21.5
Tags: 6781G, MA5 Charger, electrical, fwf, panel

I was on the fence about making this entry as multiple separate ones versus just one giant one... After all, it covers quite a few, mostly unrelated, things that I did in the last few days, and it would've made sense to keep them separate.

However; finally decided to make just one big article with all of them. None of them are finished; but somewhat a decent chunk of work is - I think I have mostly figured out where everything will go and how it will all come together.

I guess, what I'm trying to say is, if you clicked on the "Panel Layout" entry in the Log, and are trying to figure out why are you seeing notes on Firewall Forward, just keep scrolling :).

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

B&C Contactor

SS581 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

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 - side view

Beefy Wires - top view

Beefy Wires - top view

Negative leads and grounding

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

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

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

ANL template

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

Mockup backplate

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

Crimper

One side done

One side done

Second ring on the jumper

Second ring on the jumper

Done

Done

On the firewall

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

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

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

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

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

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

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

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

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 - firewall side

Adjustment screw - conduit 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

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

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

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

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

Left side

Right 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

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

Before

Before

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

After

After

After

After

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


"MidEx 726, sorry about that, Center thought you were a Midway arrival. Just sit back, relax and pass out some more cookies ... we'll get you to Milwaukee."
-ORD ATC


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