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So tere I am, my usual lovable self, ****ing & moaning about all these
HOT projects that I've been ****ing & moaning about for the last
couple of years, NOW using a simple case of cancer as my excuse for
not getting anything done... and one of my regular cage-rattlers sez:
'So what ARE these hot projects? Is there anything on them that WE
could work on?' Which brings me down a notch or two in a hurry.
Calling my hand. Well... okay.

QUANTIFIED TEST DATA vs
COMPARATIVE TEST DATA

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...and hit the wrong damned key!

Great way to start, eh?

Okay, the subject is Quantitative Data versus a WAG, which stands for
a Wild Assed Guess and it goes something like this: Bracket for...
something. It's busted and your mission, should you care to accept
it, is to make a REPLACEMENT that is both stronger AND lighter.

First thing you gotta do is get all the pieces outta the old airframe
so you can figure out the SIZE of the thing, which you do. It is
4-5/8 by 8-3/8 and is made of Mystery Metal because there's no
markings.

Miking it, you get ABOUT 1/16" It has been jitterbugged on both
sides, etched & Alodined; 3/4" flange along the narrow dimension on
one end, which has four holes for 1/8" fasteners. It supported the
power supply for a high-intensity strobe beacon, which it did via four
8-32 nut-plates, flush-riveted. Not interested in those dimensions at
the moment, just the maximum strength. Fracture was along the bend
for the flange and there's some evidence the thing was already
starting to fracture before the tail-first landing finished the job.

So... how strong was it to begin with? One way to find out is to
fabricate an identical piece, rig a bracket to simulate the load of
the power supply (which weighed about 10 ounces) then rig a bridal
from the bracket to your bucket of lead and see what it will take. As
a starting point, the bird was spec''d for +6 & -4. The original load
was 10.8ounces so 6x10.8 gives me 64.8 oz or about four pounds.

Rig a vertical piece I can hold in the bench-vise. Take the part I've
fabricated out of .062 T2024-T3, weigh it on the gram scale, writ the
weight on the back then rivet it to the upright using 1/8" rivets.
Bracket & wire to the lead bucket gets measured and added to the
static load. Pour in four pounds of lead, consisting of chunks of
wheel weights, some lead sinkers, .44" lead balls for a pistol, ditto
for some .54 loads for a real shooter, couple of lead bb's... to get
precisely 4.1 lbs.

Nothing happens. Keep pouring in the lead. Somewhere up around 24
lbs... call it 35g's... wife asks me if I want some coffee and I say,
Hell yeah! and leave the thing to hang. It's still hanging there a
couple of days later when I need the vise for something else. I put
away the lead, dismantle the bridal and toss the upright (with the
bracket still attached) under the bench. this was back in March...
mebbe February... somewhere back in there. ( But instead of getting
back to this project I end up getting diagnosed with Cancer. But
that's a different topic)

So.... the hot project is to come up with a bracket that weighs less
but exceeds the required spec.

This is a simple chore. Trouble is, I can no longer bend at the
waist, nor can I pick up 25 lbs of lead -- I can't even empty the
bucket other than a handful at a time and I figure I got better things
to do... but this one will come in handy if I need an excuse for NOT
doing something somebody wants me to do, such, as making up a
bracket... you get the idea.

Lotsa observations not otherwise posted: The bracket was sheared.
There was no sign of dressing; edges were kinda rough, which is why it
was PROBABLY starting to crack even before the tail-wheel landing.
I'm told the thing was part of a kit but the guy doing the telling
couldn't say if the bracket was part of the kit or if it was made-up
by the fellow fellow who installed it... except he didn't. The
installation was done by some 'Working Under Supervision' wet-back and
then signed-off by the guy who got all the lolly.. and who doesn't
want to talk about the job, his work ethics or why the sky is blu.
The bird has already been fixed and flown home... so this real hot
project isn't hot at all, except to me.

-R.S.Hoover

wrote in message
...
So tere I am, my usual lovable self, ****ing & moaning about all these
HOT projects that I've been ****ing & moaning about for the last
couple of years, NOW using a simple case of cancer as my excuse for
not getting anything done... and one of my regular cage-rattlers sez:
'So what ARE these hot projects? Is there anything on them that WE
could work on?' Which brings me down a notch or two in a hurry.
Calling my hand. Well... okay.

QUANTIFIED TEST DATA vs
COMPARATIVE TEST DATA

Reply Reply to author Forward Rate this post: Text for
clearing space






..and hit the wrong damned key!

Great way to start, eh?

Okay, the subject is Quantitative Data versus a WAG, which stands for
a Wild Assed Guess and it goes something like this: Bracket for...
something. It's busted and your mission, should you care to accept
it, is to make a REPLACEMENT that is both stronger AND lighter.

First thing you gotta do is get all the pieces outta the old airframe
so you can figure out the SIZE of the thing, which you do. It is
4-5/8 by 8-3/8 and is made of Mystery Metal because there's no
markings.

Miking it, you get ABOUT 1/16" It has been jitterbugged on both
sides, etched & Alodined; 3/4" flange along the narrow dimension on
one end, which has four holes for 1/8" fasteners. It supported the
power supply for a high-intensity strobe beacon, which it did via four
8-32 nut-plates, flush-riveted. Not interested in those dimensions at
the moment, just the maximum strength. Fracture was along the bend
for the flange and there's some evidence the thing was already
starting to fracture before the tail-first landing finished the job.

So... how strong was it to begin with? One way to find out is to
fabricate an identical piece, rig a bracket to simulate the load of
the power supply (which weighed about 10 ounces) then rig a bridal
from the bracket to your bucket of lead and see what it will take. As
a starting point, the bird was spec''d for +6 & -4. The original load
was 10.8ounces so 6x10.8 gives me 64.8 oz or about four pounds.

Rig a vertical piece I can hold in the bench-vise. Take the part I've
fabricated out of .062 T2024-T3, weigh it on the gram scale, writ the
weight on the back then rivet it to the upright using 1/8" rivets.
Bracket & wire to the lead bucket gets measured and added to the
static load. Pour in four pounds of lead, consisting of chunks of
wheel weights, some lead sinkers, .44" lead balls for a pistol, ditto
for some .54 loads for a real shooter, couple of lead bb's... to get
precisely 4.1 lbs.

Nothing happens. Keep pouring in the lead. Somewhere up around 24
lbs... call it 35g's... wife asks me if I want some coffee and I say,
Hell yeah! and leave the thing to hang. It's still hanging there a
couple of days later when I need the vise for something else. I put
away the lead, dismantle the bridal and toss the upright (with the
bracket still attached) under the bench. this was back in March...
mebbe February... somewhere back in there. ( But instead of getting
back to this project I end up getting diagnosed with Cancer. But
that's a different topic)

So.... the hot project is to come up with a bracket that weighs less
but exceeds the required spec.

This is a simple chore. Trouble is, I can no longer bend at the
waist, nor can I pick up 25 lbs of lead -- I can't even empty the
bucket other than a handful at a time and I figure I got better things
to do... but this one will come in handy if I need an excuse for NOT
doing something somebody wants me to do, such, as making up a
bracket... you get the idea.

Lotsa observations not otherwise posted: The bracket was sheared.
There was no sign of dressing; edges were kinda rough, which is why it
was PROBABLY starting to crack even before the tail-wheel landing.
I'm told the thing was part of a kit but the guy doing the telling
couldn't say if the bracket was part of the kit or if it was made-up
by the fellow fellow who installed it... except he didn't. The
installation was done by some 'Working Under Supervision' wet-back and
then signed-off by the guy who got all the lolly.. and who doesn't
want to talk about the job, his work ethics or why the sky is blu.
The bird has already been fixed and flown home... so this real hot
project isn't hot at all, except to me.

-R.S.Hoover
Senior Hoover (that is Californian talk),Yes sir as a retired EE, and a
person fooling around with helicopters, I really like to see some
Quantitative analysis when it is possible. Strength calcs are usually
possible to an extent and you have outlined Proof of Calcs, but I've found
another spec that worries me. Fatigue.. What is the resonant frequency of
the bracket and strobe power supply? What kind of vibration is experienced
by the bracket power supply system? Alodined? A textbook on fatigue of
aluminum structures shows that alodine as well as anodize can reduce the
fatigue life of aluminum. Obviously in some cases it is a don't ca RV
wing spar. Anodized increases corrosion life a bunch and decreases fatigue
life by 50%!! But calculated fatigue life of the spar is so large that a
50% reduction only creates a fatigue life that is way beyond the expected
life of the aircraft. Helicopters on the other hand vibrate at higher
frequencies than the "Stuck Wing" RVs and therefore use up their fatigue
life at a much faster rate. We were visited by a representative that had a
laser vibration frequency measuring device. Aim it at the member and tap
the member with a plastic hammer and the laser device would read out the
resonant frequency. Laser device was priced at $25K!! However, it should
be possible to build a home built version of that device for much less than
$1000. Another project waiting for me...

Keep stroking Senior Hoover, your work and influence are both needed.

Stu