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Jury strut AN bolts, nuts and washers

BritishCubBloke

BritishCubBloke

SPONSOR
Bellingen, NSW, Australia
The bolts, nuts and washers on my PA18-150 jury struts keep corroding. I operate near the sea.

Firstly, do I order Cadmium or stainless replacements?

Secondly, how the fricking frick do I tell what they are?! The parts catalogue doesn't seem to list them all. There are three different lengths and I cannot figure out the AN nomenclature at all. It is incredibly confusing. The AN bolt selector on Aircraft Spruce doesn't seem to have the right sizes, but that can't be right.

Can anyone help? Steve Pierce?

Thanks in advance,

David
 
I don't know how strong the stainless is. I would coat with something. Here is my hardware call-out.
IMG_20181122_091930_1.jpg

Sent from my Pixel 2 XL using SuperCub.Org mobile app
 

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BritishCubBloke said:
The bolts, nuts and washers on my PA18-150 jury struts keep corroding. I operate near the sea.

Firstly, do I order Cadmium or stainless replacements?

Secondly, how the fricking frick do I tell what they are?! The parts catalogue doesn't seem to list them all. There are three different lengths and I cannot figure out the AN nomenclature at all. It is incredibly confusing. The AN bolt selector on Aircraft Spruce doesn't seem to have the right sizes, but that can't be right.

Can anyone help? Steve Pierce?

Thanks in advance,

David
Click to expand...

Use stainless

And you need my app I wrote to help you find correct bolt lengths. Very simple to use. http://www.skuptech.com/page4/page4.html


Sent from my iPhone using SuperCub.Org mobile app
 
Jury Strut Hardware

I have cleaned up a relevant drawing (13405) with photoshop and enlarged the labels with the hardware listings, that probably has all the information you need. The system only uploaded a low resolution jpeg/pdf file but I will try and send you high resulotion copies.

A2/A4 stainless would certainly be more resilient but in the UK we would certainly need specific approval so not really an option.

13405_Strut Installation - Lift and Jury_A4.jpg

Kind regards

Stew
 

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skywagon8a said:
Mike what does your FAA guy say about the substitution of stainless hardware for the approved AN hardware? I can see it with screws holding fairings but this is a semi structural use.
Click to expand...

Corrosion resistant (stainless) hardware is FAA approved. The nomenclature just adds a "C" after the size. So your AN3-5A (undrilled cad plated approved bolt) becomes a AN3C-5A ( undrilled stainless steel approved bolt) They do cost a bit more, and I don't know about weight. I use them on exhaust and floats. Also, nuts are available in corrosion resistant steel, and are also standard, legal approved AN hardware.
 
Grant said:
We use this on all exposed hardware on float planes.

ARDROX
Click to expand...

This is interesting. I've always used a mix of Paralketone and solvent thinned for spraying inside airframes, and brushed it on exposed fittings and bolts.. but this sounds like it might be better. Is it a form of the same thing? Which I guess is basically a paraffin based coating? I've always figured Paralketone was like Cosmoline, but never sure. I read the website and would like to learn more from real experience. Is this product similar to something like Paralketone but available in different consistencies etc.? Always looking for something better when it comes to salt and airplanes..
 
46 Cub said:
Corrosion resistant (stainless) hardware is FAA approved. The nomenclature just adds a "C" after the size. So your AN3-5A (undrilled cad plated approved bolt) becomes a AN3C-5A ( undrilled stainless steel approved bolt) They do cost a bit more, and I don't know about weight. I use them on exhaust and floats. Also, nuts are available in corrosion resistant steel, and are also standard, legal approved AN hardware.
Click to expand...
Yes BUT, is the AN3C-5A approved as a substitute for the AN3-5A? The original poster BritishCubBloke is in the UK where the regulations are different than here in the States. Has the FAA approved this substitution? The C hardware is not called out in the Piper parts list to my knowledge.
 
skywagon8a said:
Yes BUT, is the AN3C-5A approved as a substitute for the AN3-5A? The original poster BritishCubBloke is in the UK where the regulations are different than here in the States. Has the FAA approved this substitution? The C hardware is not called out in the Piper parts list to my knowledge.
Click to expand...

Well, yeah.. I suppose you are right about that. I don't know... for that matter I've never looked them up to see if they have equivalent properties.. shouldn't have suggested them.
 
46 Cub said:
The nomenclature just adds a "C" after the size. So your AN3-5A becomes a AN3C-5A
Click to expand...
I've been looking for some numbers for this hardware and have only found the shear strength of the AN-3 bolts as being 75,000 psi.
Does anyone know what the shear strength of the AN-3C is?

I suspect that it is less.
 
skywagon8a said:
I've been looking for some numbers for this hardware and have only found the shear strength of the AN-3 bolts as being 75,000 psi.
Does anyone know what the shear strength of the AN-3C is?

I suspect that it is less.
Click to expand...

Curious now, I typed it into Google "AN3C shear strength". I don't know how to share links, but the first page was from Coast Fabricators. By their specs they list the AN3 and AN3C as 125,000 tensile, and 75,000 shear, with a 450 degree temp rating. At least on that page, there did not seem to be a distinction between the two in their properties.
 
Are the stainless bolts (AN3C) the same tensile strength as the cad plated ones?
The tech data sheet does not list a separate tensile strength for corrosion-resistant steel bolts. That would indicate they would be rated the same per the TDS.

Hex head aircraft bolts are made of high-strength type 4037 or 8740 alloy steel (type 8740 is most commonly used). The bolts are centerless ground and threaded after heat treatment. Minimum tensile strength 125,000 PSI. Cadmium plated per specification QQ-P-416A, Type II, Class 3. Available with shank drilled for cotter pin or undrilled for stop nut application, and with or without drilled head for safety wire. Specify bolts to have undrilled shank by adding letter "A" after the dash number. For bolts with drilled head add letter "H" after the AN number. (AN3H-15) See illustrated examples. "C" represents Type 431 Stainless Steel (contains iron which is magnetic). The length of AN aircraft bolts is measured from under the head to the end of the shank. The "grip" is the unthreaded portion of the shank. See table for conversion of length and/or grip to proper AN callout. "C" stands for stainless. Others are cadmium plated.



Sent from my iPhone using SuperCub.Org
 
Jury strut tubing is what.... 20 ga? Maybe thinner? You flatten the tube ends and drill a hole to pin with a bolt in shear. What's the tear strength of the flattened tube ends? Common sense favors the bolts being stronger than the tube ends. Especially 50 year old tubes with internal corrosion. Arguing structural properties of the bolts seems silly.
 
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stewartb said:
Jury strut tubing is what.... 20 ga? Maybe thinner? You flatten the tube ends and drill a hole to pin with a bolt in shear. What's the tear strength of the flattened tube ends? Common sense favors the bolts being stronger than the tube ends. Especially 50 year old tubes with internal corrosion. Arguing structural properties of the bolts seems silly.
Click to expand...

Well, it was about whether it is the same part to satisfy the controlling authority. Here, under the jurisdiction of my own PMI, I know I can use my own judgement where to use them. I would use them in jury struts, but would want to have paperwork by the manufacturer stating identical properties before using them in, say, a gear bolt. And, of course everyone recognizes there are qualities such as ductility, hardness, toughness.. beyond simple strength. I agree it won't make a difference in a jury strut but the point made by skywagon8A is a good one.. In England he may be stuck with the precise part number. He could just buy 10 of them and change them out when not pretty..if he doesn't want to paint them or goo them up with wax. I like to use wet paint for assembly on the parts that are going to stay together for a long time.
 
It's actually just cheap entertainment for me. I've never bothered to look up the difference, and I find it interesting to learn more.. so reading the input here is the sort of thing I like about this site... It is likely esoteric knowledge for many, but I enjoy learning a little here and there..
 
46 Cub said:
Curious now, I typed it into Google "AN3C shear strength". I don't know how to share links, but the first page was from Coast Fabricators. By their specs they list the AN3 and AN3C as 125,000 tensile, and 75,000 shear, with a 450 degree temp rating. At least on that page, there did not seem to be a distinction between the two in their properties.
Click to expand...
I found that and it does indicate the same. Yet there are two separate alloys involved which would imply that there ought to be different numbers however slight. Yet this document is only a parts catalog.
mike mcs repair said:
Are the stainless bolts (AN3C) the same tensile strength as the cad plated ones?
The tech data sheet does not list a separate tensile strength for corrosion-resistant steel bolts. That would indicate they would be rated the same per the TDS.
Click to expand...
mike do you have a link to the tech data sheet?
If in fact they are the same, then the bolts would be interchangeable. Yet we as aircraft mechanics would need this proof in order to back up our use of a substitution.
 
This website http://everyspec.com/ contains specifications on just about any piece of hardware made in the U.S. (I think).

If one searches for AN3 a four page PDF file is available giving a tremendous amount of info on that bolt.
 
BritishCubBloke said:
The bolts, nuts and washers on my PA18-150 jury struts keep corroding. I operate near the sea.

Firstly, do I order Cadmium or stainless replacements?

Secondly, how the fricking frick do I tell what they are?! The parts catalogue doesn't seem to list them all. There are three different lengths and I cannot figure out the AN nomenclature at all. It is incredibly confusing. The AN bolt selector on Aircraft Spruce doesn't seem to have the right sizes, but that can't be right.

Can anyone help? Steve Pierce?

Thanks in advance,

David
Click to expand...

David,

I worked on a supercub that lived in the Bahamas 3 months out of the year. A few points:

1. Hot salt water environments seem to increase corrosion.

2. We changed all external hardware to stainless.

3. The wings and aft fuselage received a boeshield fog every year.

4. Every year we removed all of the float parts (brakes & actuators)- (amphibs) and cleaned the salt off. If you did not do this the salt water would get in between all of the surfaces and corrode over time. Imagine running a slat water power washer over all of the amphib cub parts.

Tim
 
behindpropellers said:
David,

I worked on a supercub that lived in the Bahamas 3 months out of the year. A few points:

1. Hot salt water environments seem to increase corrosion.

2. We changed all external hardware to stainless.

3. The wings and aft fuselage received a boeshield fog every year.

4. Every year we removed all of the float parts (brakes & actuators)- (amphibs) and cleaned the salt off. If you did not do this the salt water would get in between all of the surfaces and corrode over time. Imagine running a slat water power washer over all of the amphib cub parts.

Tim
Click to expand...

Kinda like this?
IMG_4916.jpg

IMG_4905.JPG
 

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musket said:
This website http://everyspec.com/ contains specifications on just about any piece of hardware made in the U.S. (I think).

If one searches for AN3 a four page PDF file is available giving a tremendous amount of info on that bolt.
Click to expand...
Thanks, I looked at this. It gives the shear strength for AN-3 steel at 2,125 pounds and aluminum AN-3DD at 990 pounds. It does not address the corrosion resistant steel. Without knowing the specific alloy of these bolts it is not possible to determine the actual shear strength. In my experience the stainless hardware has a lower shear strength. As a result I would have no ammunition to justify using the AN-3C as a substitute for an AN-3. If someone can document the -3C number which will prove that it is at least as strong as the -3, then I would without reservation recommend using the AN-3C as a substitute for the AN-3.

It is likely that using the AN-3C bolts as a substitute for the AN-3 for attaching the jury struts on a Cub will be satisfactory. I just can not prove that it is.
 
The jury struts only stabilize the lift struts. They aren't really directly subject to flight loads. So in my opinion that AN3 bolt is simply the smallest readily available "bolt", and its stress capability really isn't important. It would be interesting to compute for comparison the edge pullout strength of the thin jury strut material. I'd be surprised if it's even close the bolt strength. But I've been wrong before - - -
 
Gordon Misch said:
The jury struts only stabilize the lift struts. They aren't really directly subject to flight loads. So in my opinion that AN3 bolt is simply the smallest readily available "bolt", and its stress capability really isn't important. It would be interesting to compute for comparison the edge pullout strength of the thin jury strut material. I'd be surprised if it's even close the bolt strength. But I've been wrong before - - -
Click to expand...

I agree on the part that the bolt is too big for its use...

BUT, take a rear jury strut out and lift or push on a wing tip and watch the rear spar flex!! amazing amount... best illustrated before you put the leading edge on....

when we patch up a plane to ferry back, jury struts MUST be there... even if wing is all bent up...
 
mike mcs repair said:
I agree on the part that the bolt is too big for its use...

BUT, take a rear jury strut out and lift or push on a wing tip and watch the rear spar flex!! amazing amount... best illustrated before you put the leading edge on....

when we patch up a plane to ferry back, jury struts MUST be there... even if wing is all bent up...
Click to expand...
Agree completely.:smile:
 
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