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Author Topic: 2-2-v1 internal or external  (Read 19515 times)

Chris Johnson

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2-2-v1 internal or external
« on: February 12, 2014, 03:54:35 AM »

All the focus seems to be on an external feature, I've never been inside one of these beasts but is it possible that thus is an internal feature?
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JNev

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Re: 2-2-v1 internal or external
« Reply #1 on: February 12, 2014, 07:13:05 AM »

All the focus seems to be on an external feature, I've never been inside one of these beasts but is it possible that thus is an internal feature?

It is possible but there are arguments against it -

The tapered spacing of the previously-attached stiffeners, for one - and apparent contour (hard to tell due to current state of material).  These details suggest a tapering, contoured installation - consistent for one with the belly of the L10.  That is not typically found in the inside details - more typically one would find straighter sections and parallel bracing there.
- Jeff Neville

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Ric Gillespie

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Re: 2-2-v1 internal or external
« Reply #2 on: February 12, 2014, 05:36:19 PM »

Couple more arguments against it being an internal piece:

•  Why aerodynamically-friendly brazier rivets on an internal structure?
•  The close spacing of the underlying structure (presumably stringers) and their beefy nature are totally inappropriate for non-load bearing structure.
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JNev

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Re: 2-2-v1 internal or external
« Reply #3 on: February 13, 2014, 03:56:09 PM »

Couple more arguments against it being an internal piece:

•  Why aerodynamically-friendly brazier rivets on an internal structure?
•  The close spacing of the underlying structure (presumably stringers) and their beefy nature are totally inappropriate for non-load bearing structure.

Excellent points - the brazier headed rivet we see was used for air passages typically.  A round head would have been used in that day for internal applications, and a flat-head where clearance needed internally.  That was the point of the 'new' universal head - one set of tools and one stock-type got it all done.

And I've learned a bit more about the "never use #3 rivets in primary structure" mantra that I lived by for so long - it now seems to have been an anecdotal construct from the time universal rivets showed up and that was passed on by a single generation then-forming their skills:

A number 3 brazier head (AN455) is relatively broader than a universal of the same shank diameter, hence has better skin-clamp-up traits (superior bearing capacity).  Hence, although the universal 'may replace all other types of same size', something got lost in the transition: you won't find #3 UNIVERSALS in primary structure to speak of - and there was a good reason for it.  Now I realize that we were taught amounted to a wise man's realization of need to 'upsize' to #4 universal if replacing a #3 brazier in primary structure - this to avoid the loss of bearing strength on light skins...

And now I know.  And how grateful I am to look back and realize how much knowledge and experience was invested in me by good men when I was a foolish boy, it is humbling and the root of a fine education, if I can apply it well. 

RIP and God bless, Thomas Munn, A&P/IA/Instructor Extraordinaire - you made a difference.
- Jeff Neville

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Ric Gillespie

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Re: 2-2-v1 internal or external
« Reply #4 on: February 14, 2014, 09:15:30 AM »

A number 3 brazier head (AN455) is relatively broader than a universal of the same shank diameter, hence has better skin-clamp-up traits (superior bearing capacity).  Hence, although the universal 'may replace all other types of same size', something got lost in the transition: you won't find #3 UNIVERSALS in primary structure to speak of - and there was a good reason for it.  Now I realize that we were taught amounted to a wise man's realization of need to 'upsize' to #4 universal if replacing a #3 brazier in primary structure - this to avoid the loss of bearing strength on light skins...

Let me make sure I have this right:

With the great ramp-up in aircraft production as the political situation in Europe deteriorated, production materials and practices were streamlined.  One example was the introduction of the AN470 UNIVERSAL head rivet to replace the AN456 brazier, AN455 modified brazier and AN??? round head rivet.  But the UNIVERSAL head had a slightly smaller diameter head than the old brazier head and therefore had less bearing capacity, so while #3 brazier heads were okay for primarily load-bearing structure, the move to UNIVERSAL head rivets required a step up to #4s as the minimum.

Can we pin down the date for the introduction of the AN470 UNIVERSAL head rivet?  I'm not having much luck finding it on line.


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JNev

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Re: 2-2-v1 internal or external
« Reply #5 on: February 14, 2014, 11:39:34 AM »

A number 3 brazier head (AN455) is relatively broader than a universal of the same shank diameter, hence has better skin-clamp-up traits (superior bearing capacity).  Hence, although the universal 'may replace all other types of same size', something got lost in the transition: you won't find #3 UNIVERSALS in primary structure to speak of - and there was a good reason for it.  Now I realize that we were taught amounted to a wise man's realization of need to 'upsize' to #4 universal if replacing a #3 brazier in primary structure - this to avoid the loss of bearing strength on light skins...

Let me make sure I have this right:

With the great ramp-up in aircraft production as the political situation in Europe deteriorated, production materials and practices were streamlined.  One example was the introduction of the AN470 UNIVERSAL head rivet to replace the AN456 brazier, AN455 modified brazier and AN??? round head rivet.  But the UNIVERSAL head had a slightly smaller diameter head than the old brazier head and therefore had less bearing capacity, so while #3 brazier heads were okay for primarily load-bearing structure, the move to UNIVERSAL head rivets required a step up to #4s as the minimum.

Can we pin down the date for the introduction of the AN470 UNIVERSAL head rivet?  I'm not having much luck finding it on line.

Yes, that is my general read of it, Ric.  I realize that is still very abstract - but I've been confounded in trying to find a rational basis for the "don't put #3 rivets in primary structure" that my old A&P teacher laid on us repeatedly back in the '70's.  He worked in a bomber production plant during WWII on the west coast as an inspector - Liberators I think.  Remembered seeing Howard Hughes come and go in a Lockheed twin - said he was a sloppy dresser, especially shoes - rag-tag.

The 'universal' seems to have emerged (am trying to find more definitive information) during the spool-up that started happening around 1938.  It was an obvious simplifying measure in that it could replace all protruding head rivets:

Quote
The universal head rivet is a combination of the roundhead, flathead, and brazier head.  It is used in aircraft construction and repair in both interior and exterior locations.  When replacment is necessary for protruding head rivets - roundhead, flathead, or brazier head - they can be replaced by universal head rivets.

Conversely, with regard to the brazier and other specialized protruding head rivets -

Quote
Roundhead rivets are used in the interior of the aircraft, except where clearance is required for adjacent members.  The roundhead rivet has a deep, rounded top surface.  The head is large enough to strengthen the sheet around the hole and, at the same time, offer resistance to tension. 
  The Flathead rivet, like the roundhead rivet, is used on interior structure.  It is used where maximum strength is needed and where there isn't sufficient clearance to use a roundheaded rivet.  It is seldom, if ever, used on external surfaces.
  The brazier head rivet has a head of large diameter, which makes it particularly adaptable for riveting thin sheet stock (skin).  The brazier head rivet offers only slight resistance to the airflow, and because of this factor, it is frequently used for riveting skin on exterior surfaces, especially on aft sections of the fuselage and empennage.  It is used for riveting thin sheets exposed to...

All of this is quoted from some antiquated guidance that a friend has provided me - trouble is, he didn't identify the publication (I have photocopies of the text but not including reference - will get from him next week).  It is old stuff and the publish date should get us into the ball park at least on when the AN470 came about and was being implemented.  He restored a Spartan Executive, so that era is his interest, hence this material - which is likely contemporary / just post-production for craft like the Executive and Electra (since those types clearly used the older styled rivets).

This text gives a good thumbnail of why the AN470 came about and what properties it was intended to have to cover at least three other types.  Where my old instructor comes in is more obscure, but consider carefully what is said here about the brazier's ability to clamp-up light skins, and that the AN470 is definitely a smaller head-area size for a given shank diameter. 

I beleive that is where my old mentor was coming from - and likely got it in his WWII era transition from a pre-war "A&E" (old designation) to a gent who worked the newly-modernized lines of WWII as they emerged.  A bit of conjecture there, but mine to make as it came out of my own past experience as passed down by an old master; I just had to wiggle through the weeds to see where he was coming from.
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Jeff Carter

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Re: 2-2-v1 internal or external
« Reply #6 on: February 14, 2014, 02:52:46 PM »

In slogging through searches of the millions of titles on Google Books and Hathitrust Digital Library, the AN470 Universal Head seems to have became standardized in the late 1940s or early 1950s. 

Aero mechanic's questionnaire. Los Angeles, Aero Publishers, 1955:  Says "This rivet was developed after the war and generally replaces round-head, brazier head, modified brazier-head, etc. rivets for uses where protruding head rivets are needed. Original rivets of the kind mentioned can be replaced with the AN 470."  Another early mention of AN470 is 1950 in Western Machinery and Steel World where AN470 is mentioned as "recently standardized".  The Magazine of Standards, Volumes 24-25, 1953 mentions standardizing on universal head to save money.  The universal head is briefly mentioned in Aluminum and magnesium design and fabrication, 1949.

The AN470 or "universal head' rivet is not mentioned in the list of rivet types in either the 1945 U.S. Navy training manual Aircraft metal work, Prepared by Standards and Curriculum Division, Training, Bureau of Naval Personnel, Washington, U.S. Govt. Print. Off., 1945 and not mentioned in the 1951 U.S.Navy Aircraft structural maintenance, prepared by Naval Air Technical Training Command for publication by the Bureau of Naval Personnel, 1951.  The unversal head rivet is finally listed in the U.S.Navy Aviation structural mechanic 3 & 2, Navy Training Courses, 1956 for use "when existing stocks are depleted."

Aircraft manuals which list the aircraft's rivet types are hard to find, but occasionally a list of rivets will be given in repair or structural manuals on ww2aircraft.net or avialogs.com.  The T-6 Structural Repair Manual, 1943 lists rivet types but does not include AN470 or universal head rivets.  The AN 01-60-3 Structural Repair Instructions for A-36 Series and P-51 series, 1943 (revised 1945) does not include any information on AN470 or universal head rivets.

Earliest mention of AN470 I found in NACA reports was 1952.
« Last Edit: February 14, 2014, 03:24:15 PM by Jeff Carter »
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Alfred Cramer

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Re: 2-2-v1 internal or external
« Reply #7 on: February 14, 2014, 03:36:00 PM »

The T-6 Structural Repair Manual, 1943 lists rivet types but does not include AN470 or universal head rivets. 

To add minutely to this impressive bibliography, Process Practices of the Airline Industry (1942) lists a "universal-head rivet" but it's NAF1008, not AN470.
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John Ousterhout

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Re: 2-2-v1 internal or external
« Reply #8 on: February 14, 2014, 04:31:22 PM »

To add even less, I believe Ric transposed 455 and 456.  The AN456 is a modified brazier rivet.  The AN455 is a brazier rivet.

To Alfred's point, was the Universal Head rivet called something else before the war?  I'm not sure when the "AN..." designation started being used for Mil-Spec fasteners.
Cheers,
JohnO
 
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Ric Gillespie

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Re: 2-2-v1 internal or external
« Reply #9 on: February 14, 2014, 05:37:17 PM »

To add even less, I believe Ric transposed 455 and 456.  The AN456 is a modified brazier rivet.  The AN455 is a brazier rivet.

Thanks. I'm not clear on how the "modified brazier" differs from the "brazier" so I'm not sure which kind Lockheed used on the Model 10 but I do know they're just like the one on the artifact.

To Alfred's point, was the Universal Head rivet called something else before the war?  I'm not sure when the "AN..." designation started being used for Mil-Spec fasteners.

The parts manual for the Lockheed 10 is full of fasteners with AN designations.

From what Jeff Carter found it's looking like the AN470 came along much later than we have been supposing (earliest date 1949). If so, we shouldn't see that rivet on WWII aircraft that have not been "restored."
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John Ousterhout

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Re: 2-2-v1 internal or external
« Reply #10 on: February 14, 2014, 05:59:54 PM »

This site has a convenient chart that shows the various rivet configurations.  It also links to detailed drawings.
Cheers,
JohnO
 
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Ric Gillespie

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Re: 2-2-v1 internal or external
« Reply #11 on: February 14, 2014, 07:02:05 PM »

This site has a convenient chart that shows the various rivet configurations.  It also links to detailed drawings.

Looking at the chart I'd say we have a AN455 brazier on the artifact ( the head on the 456 is TINY).  Just to be sure I'm going to buy examples of each rivet.  Univair Aircraft Corporation sells them.
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John Ousterhout

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Re: 2-2-v1 internal or external
« Reply #12 on: February 14, 2014, 07:32:23 PM »

Buy enough to mock up a sample to test.  For that you'll also need both sizes.
Cheers,
JohnO
 
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Ric Gillespie

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Re: 2-2-v1 internal or external
« Reply #13 on: February 14, 2014, 07:49:07 PM »

Buy enough to mock up a sample to test.  For that you'll also need both sizes.

We're not ready to build the mock up yet.  I just want to have examples for reference.
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JNev

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Re: 2-2-v1 internal or external
« Reply #14 on: February 18, 2014, 11:19:44 AM »

That is an interesting find on the AN470 date of appearance - all I had found before that suggested it was a war-time development.  Good find.
- Jeff Neville

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