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What say yee?

RVG8tor

RVG8tor

Well Known Member
My Breaker panel will be hinged at the bottom, the idea being future maintenance, you just have to tip the panel out to get to the bus bars. In order to support the wire bundles I want to use a cushion clamp attached to the bus bar. I have a a tie for two rows of breakers that is held together with #8 screws, this is a convenient place for a cushion clamp. You can see the clamp in the photo.

The clamp is totally cushioned, (WDG type) so the wires will not touch any metal, but there would be voltage running trough the metal part of the clamp. I wonder if this could cause problems? It would take more work but I can fashion a standoff attached to the panel to make the same support. Just wonder if the easy route will work.

Thanks for the help

2mcfwuc.jpg
 
I see no reason why there should be a problem with these wires. They are double insulated (once with the wire sheathing, and again by the rubber in the WDG clamp). Stick with the simple route.

greg
 
I would be a bit worried about the long-term potential issue of the weight of the wires plus vibration causing the copper to work-harden, and maybe crack. (Although the copper looks pretty stout.)

I could be way off base here.:eek: I work on some pretty old airplanes, and have seen what the ravages of time and vibration can do.

And I'm talking about airframes, not my body!!:eek:
 
Pete,

I presume you are talking about the copper in the wires. To mitigate this, perhaps a couple additional supports would work? Any thoughts on the maximum length of unsupported wire?

greg
 
My current rocket has a hinged buss as you describe. It swings down from the panel and is held up in place with a 4g bungee cord. (at 3.5 Gs it starts to "fall" down below the panel). I have built a couple of other planes with this type of buss panel. If you have the wires enter the panel close to the hinge point and leave some slack you will have no problems. The panel only gets pulled down a few times a year so it is not like it is moving that often. It does make servicing and trouble shooting very easy.
 
Greg Arehart said:
Pete,

I presume you are talking about the copper in the wires. To mitigate this, perhaps a couple additional supports would work? Any thoughts on the maximum length of unsupported wire?

greg
Click to expand...

Actually, I was thinking about the copper bus bars. (Probably overthinking the issue.)
 
mmmmmh,

I would prefer use a small tube to prevent wire chafing and metal contact in this area. Just one inch between the clamp and wires.

my2cent
 
So, I'm now not clear about this buss bar. Is this hot or a ground bar? If it's hot, I don't think I would want a hot bar exposed like this, particularly if it's not securely fixed in place. I would prefer to have some sort of insulating shield around anything hot otherwise it could easily be shorted to the airframe.

If its a ground buss, then its common with the rest of the airframe and shouldn't be an issue. I would also agree that Luca's idea of a small piece of tygon or nylon tubing will help prevent chafing. I would prefer the tygon so that you could tighten down the adel clamp and keep the wires from moving. The nylon would be too rigid and you are unlikely to be able to squeeze it enough to grab the wires.

my two cents

greg
 
Thanks for the info

Sorry for the late replay, I was flying a trip to Osaka, Japan. The clamp is on the main bus bar the bar with shrink tube ties the two rows on the main bus. The bars are all made from .032 x .5" brass (the tie is .063)

I posted this on the Aeroelectic list and Bob K. thought it would be fine with only 4 wires but did admit it was somewhat unorthodox. I have more wires that just the 4 in the photo and have 3 row of breakers. Luca made a good point that if were to do this I should give some extra insulation by adding some tubing around the wires.

I think based on the inputs I will tackle this by making a stand off that is attached to the panel but not the bus bar.

Again thanks for all the inputs. I get 17 hours back home Christmas day before a trip on Sunday. It sucks being away from home for the holiday but it is nice getting folks to there destinations this time of year.

Merry Christmas from Osaka!
 
RVG8tor said:
....
I posted this on the Aeroelectic list and Bob K. thought it would be fine with only 4 wires but did admit it was somewhat unorthodox. I have more wires that just the 4 in the photo and have 3 row of breakers. Luca made a good point that if were to do this I should give some extra insulation by adding some tubing around the wires.
....
Merry Christmas from Osaka!
Click to expand...

Extra insulation would be fine, but there is an interesting point to your set-up.

If the insulation did fail at the clamp, since both the clamp and the wire are at 12 volts, there would be no big spark or release of smoke...:)

All you would lose would be the action of the by-passed CB.

You could almost say it's safer than a grounded clamp....
 
My solution

While on my trip over the holiday I was able to come up with a solution to support the wires going to the CBs. A couple years ago I picked up some stand-offs at an air show from a surplus seller. I am not sure what they are for, there is a part number but they are pre-drilled and the post is threaded for an AN3 bolt, they work like nut plates, the bolt goes in easy then gets tight. There is a tiny inspection hole to make sure the bolt goes in far enough I assume, kind of like the tiny hole in a D-sub pin. I have used these little threaded posts other places, kind of handy.

339hh8k.jpg
 
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