flickroll

flickroll

Well Known Member
In my -8 there is one shielded wire with which I would like to have quick disconnect capability. Is this OK, and if so, what's the best method? D-Subs? Deans connector? Something else? Don't do it :) ? Should the shield wire go across the connector or is it OK to have a short piece of a shielded wire unshielded (in other words, the short piece of the connector itself remains unshielded)?

Thanks

Jim Shannon
RV-8 N52VV
Charlottesville, VA
 
Jim,
You don't say what the application is, but typically it is acceptable to have a short portion of the wire unshielded inside the connector. If you use something like a d-sub connector with a metal backshell, it is still somewhat shielded from outside sources, although not from other wires within the connector.
 
Jim,

What's the application?

If it will be repeatedly plugged/unplugged as part of normal operation & it's a 'non-critical' item, there are many choices at your local Radio Shack or local equivalent. (Higher quality versions of the same connectors are available from a good audio supply house. Switchcraft is a good brand.)

The lightest weight ones would probably be the mini-phone plug connectors, similar to the headset connector on an Ipod except mono instead of stereo. You can get the plug and a mating in-line jack. If they don't have the mono version, just buy the stereo & ignore the 'ring' terminals in the connectors. The only real downside to them is lack of locking feature, but if you are hooking up a portable device the lack of lock can be an advantage (snag the wire & it unplugs instead of breaking the wire).

If you need a lock, check out the 'XLR' type connectors used for balanced mic lines in pro audio equipment. They are a *lot* heavier (ounces instead of grams), but do have the lock feature & will carry substantial current loads if you are powering something with this line. They have 3 terminals, but the metal shell can be used as a 4th terminal. All combinations of in-line or panel mount, Male or Female are available.

Charlie
 
This particular application is for a four wire shielded cable exiting the fuselage and heading out to the right wingtip. The cable is for a Dynon remote compass. I'd like the quick disconnect capability for ease of wiring the aircraft right now, and later when/if a wing is removed all you have to do is uncouple the connector to remove the wing. Thanks

Jim Shannon
RV-8 N52VV
Charlottesville, VA
 
The shielding on the Dynon EDC is not all that critical. You can get by with pretty much any connector.
 
Another one that would be handy to have a disconnect on is the serial altitude encoder wire going to the GTX327 Transponder from the Dynon D100. Would this one be OK to have the disconnect on?

Jim Shannon
RV-8 N52VV
Charlottesville, VA
 
It would probably be ok, but I fail to see what the benefit would be. Extra connectors add extra complexity, and reduce reliability when they are placed in areas where they are not needed.

Also, again Mel is correct. On the Dynon remote compass line it's not that terribly picky....

Cheers,
Stein
 
The only advantage is when removing the panel from the airplane. A quick disconnect on that line, plus other wire terminations at terminal blocks, allows the whole panel to be easily removed. It's not that big a deal, and if it's better I'll leave the disconnect off.

Jim
 
Hi Jim,

I understand your reasoning, but I'd discourage connectors for that application or future reason. I usually try to push everyone to build their planes (in their entirety - including systems, structure, etc..) for the 99th percentile of use/maintenance....not the 1 percentile of maybes. How many times do you see yourself removing the panel for anything other than upgrades, etc..? There is an entire slew of other items that make removing the panel a not so simple affair so I'd just say don't worry about it. It's one wire out of many things. Even the "plug & play" panels you see come out of professional shops are NEVER that simple. There is a LOT of other things that your panel ends up having connected to it.

My 2 cents!

Cheers,
Stein
 
I've had this question myself but not in the context of removing a panel. I've wondered about wing root disconnects and what happens to the strobe drain wire at the connection. What I presume the answer is here is that it should be treated as any other wire.

The reason it's an issue for me is I'd like to get the wings on under the assumption I can fly it off the field I'm at BUT the field I'm at is in transition. The FAA and DARs are trying to "discourage" first flights but it's not entirely set in stone yet and there's the possibility I could fly it off the field and land it somewhere else and there's the possibility that I'll have to dismantle the thing and truck it to that "somewhere else."

At the same time I'd like to wire up the landing ligts and Tru Trak (well, actually, I would have to cut these wires since I bought Stein's harness) and strobe navs under the assumption that I won't have to deconstruct the darned thing.
 
Strobe wires

Interesting coincidence that this question appeared now... I was just looking at my Vans lighting Sytem 6. There are three strobe lights, and this foil-shielded wire that is used to connect them. Now, the instructions say to ground the sheilding to the airframe. Two questions occur to me...

1) I'm not sure whether I should solder the foil to a wire and run it back to the ground bus on my firewall? Or good enough just solder teh foil directly to the nearest bulkhead?

2) for the strobes out on the wingtips, if I break the wire at a connector at the wing-root, the shielding will be broken there. This means the shielding running out through the wing wouldn't grounded, unless I attach a wire to the shielding with another connector to attach it to a wire in the fuselage running back to the ground bus. What have others done about this?
 
prkaye said:
1) I'm not sure whether I should solder the foil to a wire and run it back to the ground bus on my firewall? Or good enough just solder teh foil directly to the nearest bulkhead?
Click to expand...

I don't believe you do anything with the foil. It's the drain wire (the uninsulated wire encased in the foil) that you'll be using.

prkaye said:
for the strobes out on the wingtips, if I break the wire at a connector at the wing-root, the shielding will be broken there.
Click to expand...

Shielding and grounding are two different things.
 
I don't believe you do anything with the foil. It's the drain wire (the uninsulated wire encased in the foil) that you'll be using
Click to expand...

The instructions that came with the whelen stuff definatley said to ground one end of the shield to the airframe. I'll pull the instructions out and provide the exact reference/quote when I get home.

Shielding and grounding are two different things.
Click to expand...

Of course I realise that, but if the shielding is supposed to be grounded to be effective (as suggested in the instructions), then this leads to the problem I described.
 
I'm still not following you. Why would you ground your shield by attaching the foil to anything? You can, I guess, run the drain wire all the way to the ground on the firewall if you want. I may do that since I used the strobe bracket from Van's and attached it to a primed stringer. Otherwise I'd just ground it there.
 
In this case...

Bob Collins said:
I'm still not following you. Why would you ground your shield by attaching the foil to anything? You can, I guess, run the drain wire all the way to the ground on the firewall if you want. I may do that since I used the strobe bracket from Van's and attached it to a primed stringer. Otherwise I'd just ground it there.
Click to expand...

...I believe the foil is the shield. It's just a different way of fabrication.

It should be just grounded per the instructions to the airframe - I would connect it to one of the power supply mounting screws. If the power supply to strobe light line is broken by a connector in the middle of the line, then connect the other end of the line to the airframe near the strobe... this will make the wire shielded in two portions, with no countinous DC path due to the connector. Should be OK in this configuration.
 
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