az_gila

az_gila

Well Known Member
Doug... I noticed the new audio clip and picture dealing with grounds, and I feel it should be commented on.

The gist of the audio was to use graphite paste, which is fine, however the associated picture showed some techniques that are definitely not in accordance with AC 43.13.

Grounding hardware is quite well detailed in Chapter 11 of the "bible".

long link here to FAA web site

Page 82 (Table 11-16) covers how to use bolts as ground connections - our terminals are usually tinned copper, so use the lower half of the table.

In the picture shown...

No removal of primer under the nut - bare metal should be exposed.

A self locking nut is not appropriate as shown against the metal surface.

No washers apparent, either plain or self-locking.

Plain washers and self-locking washers are the correct hardware to use, and the materials should be as listed in the AC. In general, for our alum. planes, standard cadmium plated AN hardware is correct, with an aluminum washer under the terminal.

A final lock nut on the "stack" of parts is correct, and not shown.

It is so easy to follow the recommendations of AC 43.13-1b in this case, that there is no reason for using any other procedure.

If your Technical Counselor disagrees with the 43-13 recommendations, then let's have an open discussion about his reasons, and have him present them.

Until this happens, I believe the FAA recommendations are the correct procedures, and we should not propagate alternate methods without good reason.

YMMV, but I think that TCs should start with the FAA guidance as a basis for our RV construction work.

gil A
 
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Gil is correct - but the Van's plans do show a nyloc nut securing the ground stud to the panel, similarly with the "studs" on the on the home made terminal block. It can be confusing.
Jim Sharkey
RV6 - Wiring
 
Maybe Mel Asberry will chime in...he was standing next to me when I took the pic.
b,
d
 
Gil,
Your points are correct. However you must realize that this aircraft is a ways from being completed. These points were discussed at the meeting. Don was simply discussing one point. He was not trying to do a complete diagnosis. Another point that was not brought out was that you should limit the number of ground lugs to three per stud.
 
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Mel said:
Gil,
Your points are correct. However you must realize that this aircraft is a ways from being completed. These points were discussed at the meeting. Don was simply discussing one point. He was not trying to do a complete diagnosis. Another point that was not brought out was that you should limit the number of ground lugs to three per stud.
Click to expand...

FYI - Chapter 11 says four lugs max.
 
The MIL Spec for grounding was developed partly with an eye to 43-13, and partly with an eye toward aircraft life cycle managment. The limitation of 3 lugs per terminal was established as a means of allowing easy supplemental/after-the-fact equipment installation. All of the rework instructions I've had to get through USAF/US Army approval have allowed the addition of one ground lug to each pre-existing ground terminal, thus not exceeding 43-13's 4-per-terminal recommendation. By limiting net-new installations to 3-per-terminal the Mil Spec makes it easy for future systems growth without having to install a new grounding terminal.

If you're building a new airplane it's not a bad idea to go with 4-per-terminal, but install an extra terminal or two at the main grounding points (firewall, instrument panel). This will make it easy for you to install and properly ground any equipment you might add in the future.
 
thanks

Thanks for the comments guys, it was just that I have found it is cheaper to buy all of my hardware from Home Depot and not Van's. Besides those pesky ny-locs are so hard to work with and I can hand-tighten the other ones.
 
If you have very many grounds at all...I'd sure recommend going with the single point ground that Aeroelectric Connection recommends and that B&C sells, with a panel of tabs on each side of the firewall. It sure makes it easy to map out your ground bus.
 
Picture vs. text vs. completion status

Mel said:
Gil,
Your points are correct. However you must realize that this aircraft is a ways from being completed. These points were discussed at the meeting. Don was simply discussing one point. He was not trying to do a complete diagnosis. Another point that was not brought out was that you should limit the number of ground lugs to three per stud.
Click to expand...

Mel... The plane may be a way from being complete - but the caption and audio did not say that - and the picture looked like a completed item with a torqued down nut - looked completed in the picture to me. Whatever the completion status, the associated picture did not seem to really connect to the point being made in the new "audio clip' feature.

With 8000 users (is that the number DR?) I believe that factual detail with a back-up data source should be part of "how to do it hints".

In this case, following the AC 43.13-1b is extremely easy, and that is the way it should be shown.... and if Van shows otherwise, he should be notified.

Perhaps the whole reason for the Home Depot paste is that the FAA (and Mil-Spec) basic assembly hardware requirements - which protect against long term dissimilar metals corrosion - are not being followed?

Thank you DR for fixing the front page reference..... Remember that no-one has yet repealed the "picture equals a 1000 words" rule yet...:)

gil A
 
Which drawing?

jsharkey said:
Gil is correct - but the Van's plans do show a nyloc nut securing the ground stud to the panel, similarly with the "studs" on the on the home made terminal block. It can be confusing.
Jim Sharkey
RV6 - Wiring
Click to expand...

HBi Jim... where is this?

The original -6 plans missed the electrical bit...:)

My later OP-10 electrical drawing sheet does not detail this and it's not in my later Section 5 of my updated (2002) manual.

gil A
 
az_gila said:
HBi Jim... where is this?

The original -6 plans missed the electrical bit...:)

My later OP-10 electrical drawing sheet does not detail this and it's not in my later Section 5 of my updated (2002) manual.

gil A
Click to expand...

OP-12 (RV-6/6A WIRING HARNES INSTALLATION) dwg ref A10 shows 2x AN960-8 WASHER and 2X AN365-832A NUT for securing the studs to the Terminal Block.

There is no call out for the ground studs but pictorially they look the same.

It looks like the intention is to lock the studs to the panel with AN365s and also to lock the lugs to the studs with AN365s.

However Doc ES Harness-6/7/9r2 1/28/04 that came with the harness kit, page 3, Mechanical, 13th paragraph, referring to the ground stud screws says:

"Remove paint and primer from around the holes. Install the screws with an AN935C1032 external tooth lock washer on the front and the back of each panel to help make good electrical contact and prevent the screw from rotating."
 
az_gila said:
Mel... The plane may be a way from being complete - but the caption and audio did not say that - and the picture looked like a completed item with a torqued down nut - looked completed in the picture to me. Whatever the completion status, the associated picture did not seem to really connect to the point being made in the new "audio clip' feature.

With 8000 users (is that the number DR?) I believe that factual detail with a back-up data source should be part of "how to do it hints".

In this case, following the AC 43.13-1b is extremely easy, and that is the way it should be shown.... and if Van shows otherwise, he should be notified.

Perhaps the whole reason for the Home Depot paste is that the FAA (and Mil-Spec) basic assembly hardware requirements - which protect against long term dissimilar metals corrosion - are not being followed?

Thank you DR for fixing the front page reference..... Remember that no-one has yet repealed the "picture equals a 1000 words" rule yet...:)

gil A
Click to expand...

Hey; I didn't publish the picture or the audio. I was just explaining the circumstances.
 
A consideration in electrical joints is the joint resistance. This is especially important in the battery and return conductors in the starting circuit! To get low-resistance joints requires a clamping force of 1500 psi. Multiply this value by the contact area of the lug from its length-width minus the hole area. Use this obtained clamping force to select a Belleville spring washer of the correct value. This will not only assure a low-resistance joint, all other things taken into account, but will insure that the nuts will not rotate under vibration and any dis-similar thermal expansion of dis-similar materials will be provided for. Keep in mind that if you abrade a copper or aluminum surface it will immediately begin to oxidize on contact with the air. That is why you should abrade the mating surfaces after coating them with petroleum jelly or No-Oxid paste and then don't remove the grease but let the clamping force cause it to ooze out. These recommendations come from an ALCOA manual on joining contacts. It is also important that you do not rely on the mounting screws to provide the alternator/generator ground to the engine but that should be provided by a conductor such as a braid from the alternator case to the engine. It is also good practice to join a braid conductor from the engine to the firewall, since a lot of engine sensors use the engine ground as their return to a meter or EFIS; don't expect a magic return!!!
 
Why not just follow the standards?

elippse said:
A consideration in electrical joints is the joint resistance. This is especially important in the battery and return conductors in the starting circuit! To get low-resistance joints requires a clamping force of 1500 psi. Multiply this value by the contact area of the lug from its length-width minus the hole area. Use this obtained clamping force to select a Belleville spring washer of the correct value. This will not only assure a low-resistance joint, all other things taken into account, but will insure that the nuts will not rotate under vibration and any dis-similar thermal expansion of dis-similar materials will be provided for. Keep in mind that if you abrade a copper or aluminum surface it will immediately begin to oxidize on contact with the air. That is why you should abrade the mating surfaces after coating them with petroleum jelly or No-Oxid paste and then don't remove the grease but let the clamping force cause it to ooze out. These recommendations come from an ALCOA manual on joining contacts. It is also important that you do not rely on the mounting screws to provide the alternator/generator ground to the engine but that should be provided by a conductor such as a braid from the alternator case to the engine. It is also good practice to join a braid conductor from the engine to the firewall, since a lot of engine sensors use the engine ground as their return to a meter or EFIS; don't expect a magic return!!!
Click to expand...

ALCOA is covering their b*^t after the aluminum wire home electrics fiasco of the 70's. They use quite different materials in home construction.

Why not just follow the FAA recommendations of AC 43.13-1b... which have been well proven over the years?

A standard (fresh, not used...:)...) AN lockwasher that is called out in the chart referenced in my first post will provide all of the clamping force needed.

Why change a well proven - and basically a Mil-Spec - way of assembly?

The correct washers, as called out, will prevent the dis-similar materials problem you mention.

gil A

PS ... I bet the FAA chart was developed well before ALCOA found that their suggested materials and processes caused many house fires...:(
 
az_gila said:
ALCOA is covering their b*^t after the aluminum wire home electrics fiasco of the 70's. They use quite different materials in home construction.

Why not just follow the FAA recommendations of AC 43.13-1b... which have been well proven over the years?

A standard (fresh, not used...:)...) AN lockwasher that is called out in the chart referenced in my first post will provide all of the clamping force needed.

Why change a well proven - and basically a Mil-Spec - way of assembly?

The correct washers, as called out, will prevent the dis-similar materials problem you mention.

gil A

PS ... I bet the FAA chart was developed well before ALCOA found that their suggested materials and processes caused many house fires...:(
Click to expand...


Gil,

Any idea why the Van's plans don't follow the AC41.13-1b to the letter? It can't be the expense. The nuts and washers needed are dirt cheap.

Jim
 
Too busy?

jsharkey said:
Gil,

Any idea why the Van's plans don't follow the AC41.13-1b to the letter? It can't be the expense. The nuts and washers needed are dirt cheap.

Jim
Click to expand...

Too busy designing to read all of Chapter 11?....:)

You have to get to page 82 of the chapter to reach the table....

gil A
 
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