Bus Bar Material

kontiki

kontiki

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Kontiki
Pulled a suspicions looking piece of bus bar material out tonight. Looks like it's dead soft aluminum. Is that a common GA practice?

I couldn't find any plated copper bus bar in any of the usual supplier catalogs. I can probably buy a piece of copper and tin it after I drill it.

I'd be open to an off the shelf plated bus bar if anyone knows a source. Terminal strip bus bars don't work because of the hole spacing.
 
It's probably aluminum and so too would be the wiring (probably). AL-6 is the smallest AWG size aluminum wire recommended for use on aircraft, that could be an easy way for you to know if your wiring is aluminum.
 
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Nothing wrong with an aluminum bus bar. Aluminum is actually substantially more conductive than copper per unit weight.
 
kontiki said:
Pulled a suspicions looking piece of bus bar material out tonight. Looks like it's dead soft aluminum. Is that a common GA practice?

I couldn't find any plated copper bus bar in any of the usual supplier catalogs. I can probably buy a piece of copper and tin it after I drill it.

I'd be open to an off the shelf plated bus bar if anyone knows a source. Terminal strip bus bars don't work because of the hole spacing.
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https://www.aircraftspruce.com/catalog/pdf/bussbartds.pdf
 
I'm familiar with aluminum 00/000 (can't really remember size) generator feeder wiring and have done the whole copalum splice thing a couple times. Never saw it used as a bus bar. Nothing else in the electrical system is aluminum that I'm aware of. It does look like it would be easy to work with. I need more if I'm going to make it the solution. Any references to alloy type and ampacity calculations?

The holes in the MS25226 bus bar I already have can't be used as is, the breaker holes are 13/16 centers. I woke up thinking getting slightly oversize bar and drilling my own holes. I'd feel better with the higher ampacity there too.

What a difference a nights sleep makes. Thanks.
 
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kontiki said:
I'm familiar with aluminum 00/000 (can't really remember size) generator feeder wiring
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Most conductors once you get up in size are going to be aluminum.
and have done the whole copalum splice thing a couple times.
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Copalum is used to join copper wires to aluminum wires safely. It's a different issue than terminals.
Never saw it used as a bus bar. Nothing else in the electrical system is aluminum that I'm aware of.
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Aluminum bus bars are pretty common. They're pretty standard in the regular power industry.
 
Take the removed bar to an NDT shop and see if they'll do a conductivity test on it for you. That may tell you what you have, however some aluminum alloys conductivity ranges overlap, been there a few times and used chem sort to make an exact alloy determination. But, chem sort is destructive testing and only used on old parts you plan on disposing of or new material when you have enough extra.
 
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I thought there was a reaction between copper and aluminum? :confused:
 
GlennAB1 said:
If the bus bar wasn't plated it would oxidize pretty readily too.
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Copper oxidizes VERY slowly, and only in very controlled environments, and copper oxide is very black and not a bad conductor. I'm sure you meant that it SULFATES, forming the green verdigris so pretty on copper statues and roofs,which is an insulator.

You ever took a high school or college chem class?

Jim
 
weirdjim said:
Copper oxidizes VERY slowly, and only in very controlled environments, and copper oxide is very black and not a bad conductor. I'm sure you meant that it SULFATES, forming the green verdigris so pretty on copper statues and roofs,which is an insulator.
You ever took a high school or college chem class?
Jim
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Thanks Jim, my bad, it was in reference to the previous posts about aluminum, which seems to be the major subject in this thread, but you are so bent on correcting me you missed that. Did you ever respond about your 60 years experience in aircraft maintenance and you not being on the Charles Taylor Master Mechanic Award honor roll? When I hit 50 years you can be damn sure I'll be on it.
 
GlennAB1 said:
Thanks Jim, my bad, it was in reference to the previous posts about aluminum, which seems to be the major subject in this thread, but you are so bent on correcting me you missed that. Did you ever respond about your 60 years experience in aircraft maintenance and you not being on the Charles Taylor Master Mechanic Award honor roll? When I hit 50 years you can be damn sure I'll be on it.
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Reputation preceded by ego?
 
GlennAB1 said:
If the bus bar wasn't plated it would oxidize pretty readily too.
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I gave some thought to using copper and just tinning it after I drilled it. I don't have a solder pot, the copper bar I have is kind of huge anyway. I'm AWP right now, I'm hoping that I'll be able to take a piece of MS25226 (-4 or -6) and drill my own holes offset from the production holes, it gives me an easy way to document the rating. I probably can find a metallurgy reference for 2024-T0 (I work with a bunch of structures guys) and could work through the circular mils to cross sectional area calculation for a piece if I need to. I prefer to adapt the mil spec part if I can.
 
Copper and aluminum indeed develop coatings that are not as conductive as the base metal. This is why just twisting wires together is NOT a approved way of doing things (either in a plane or in building wiring). While dissimilar metals can create a corrosion cell (it also takes moisture), the problem with aluminum household wiring isn't one of corrosion typically. It's because of the different thermal expansion and malleability cause commonly used methods designed for copper alone not to work reliabily (wirenuts are right out, even certain other devices like receptacles and switches not rated for aluminum wires). The main bus bars in most building electrical panels these days are aluminum and they have copper wires in them without problem.
 
A former plane had an aluminum bus bar between the alternator and landing gear breakers. Over time the screw terminals had worked slightly lose and allowed corrosion to develop under the terminal connection which then caused occasional arcing / overheating.

We replaced it with copper, drilled out as you describe. Never had a problem after that.
 
My 1962 Cessna had bare copper bus bars. They were dark brown oxidized (not green). I removed the fuses, and installed breakers in their place. 54 years, and that bird is still going!
 
Sure is a wide variety of them on ebay. Lotta ways to skin the ol' cat. Almost all of these has violated at least one rule of thumb in some way, like minimum bend radius of wires or the number of terminals installed on one screw. The top picture shows the bus terminated into an Amp CPCs (commercial) connectors without any backshell. I've seen the backshell-less CPCs used on STC's appliances before.

















 
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Backshells are for strain relief and often sold separately so that each application can be tailored, i.e. 90 deg. bend vs. straight, I suspect an oversight rather than intentional omission.
 
GlennAB1 said:
Backshells are for strain relief and often sold separately so that each application can be tailored, i.e. 90 deg. bend vs. straight, I suspect an oversight rather than intentional omission.
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I think intentional omission. That one at the top is from a Cessna 182T per the ad.
http://www.ebay.com/itm/Cessna-182T...ash=item35f933ebdc:g:9BIAAOSwa-dWmC1Y&vxp=mtr


The others I mentioned were installed on the pigtails of two separate instruments EGT/CHT and a Fuel Flow. Both where assembled without backshells by the manufacturer. I'm guessing they are using double crimp open barrel contacts to omit the backshell.

You must slip a straight backshell over the harness prior to pinning the contacts into the plugs on the Amp CPC series connectors.
 
Then that's an engineering call, and deviates from standard industry practices, which they can. I suppose these are connectors that aren't expected to be messed with frequently, if ever.
 
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