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Better Borescope Crack Resolution

DanH

DanH

Legacy Member
Mentor
Annual time, so again inspecting the outboard HS hinge attach rivets for cracking of the spar:

www.vansaircraft.com

SB-00036 REV 3 - Van's Aircraft Total Performance RV Kit Planes

Requires inspection of outboard elevator hinge bracket area on rear spar of horizontal stabilizer for cracks. If cracks are found, repair and replace outboard hinge brackets with new parts.
www.vansaircraft.com www.vansaircraft.com

I'm using a Teslong inspection camera, a nice little unit with both side and end views on the borescope wand. The spec page says image capture resolution is 1920 x 1080. Does a pretty good job, with one exception. When looking at shiny unprimed surfaces, it's difficult to decide if I'm looking at a crack or a scratch. Primered parts, no problem. Anodized surfaces, quite good. It's just the shiny stuff.

So how to improve crack identification? Tell me a trick please. Remember, we're looking insde a closed assembly.

Just for fun, the photos below are the same potential crack, taken one year apart. No visible change. Crack or scratch?

Same Rivet 2023 2024.jpg
 
looks like a scratch to me. The examples of cracks that I have seen related to this tend to have ragged edges, propagate radially, and mostly in a straigh-ish line.
 
I don’t have any tricks Dan. I have the same issue on the HS spar. I was able to get die penetrant on this area however. Didn’t help much. Pretty sure it’s a scratch.
I just watch it and no growth, no change, no problem. Document with photos as you do.
Curios to see other responses.
 
I've struggled with the same problem. Perhaps turn off the camera's light and get a separate fiber optic light to come in from a different angle than the camera lens.
 
Puff some tire talc in there to kill the shine? Never tried it, just a thought.
 
I spent a decent part of my early career working with machine vision systems, and regularly work around people that still do. Lighting makes all the difference in some images. Try lighting from different angles, and vary the brightness. Off-axis lighting (fancy way of saying light the image from the side) can show amazing things. Some colors of light make some metals ‘pop’ more than others, though my memory isn’t good enough to tell you which colors work best for which metals, and if memory serves, I only remember witnessing that on black and white images, so add in a color camera and things may change. That said, I’m not sure how to accomplish that in the instance of this inspection since I’m still building and haven’t done the inspection myself, so some creativity may be in order. Judging by your history of posts, I’d say you have plenty.

To me what you have looks like a scratch. The metal grain seems to carry through it on one of the images.
 
Just running the pics through a number of light filters you can see the grains running perpendicular to the scratch as Sam says.
Doesn't appear to even break the surface.
 
I have probably the same scope that I have used quite a lot, and I agree with your comments about it.
I also agree with others that to me it looks like a scratch.
 
I had mark like that, I think came from shoving my bore scope in there and the tip made the mark. I squirted a little WD40 on there and it disappeared. If it was a crack it could not have disappeared.
 
Dan,
I don't think the light would travel almost perpendicular across a crack as it does in your two photos. Across a scratch it is plausible. I say enjoy another year of flying your RV-8.
 
Maybe you could try taking images from multiple angles (at least 4, as widely separated as possible) and pass the results through VisualSFM or a similar program to get a high resolution 3d image?
 
Both photos in post # 1 seem to show a direct reflection from the lighted scope. If the scope is positioned at an angle that's not perpendicular to the surface being inspected, the light will not be reflected back into the scope as much. Try this: in a darkened room, put your cell phone "flashlight" right over your nose and shine it at a mirror. You'll probably see not much but the flashlight in the mirror. Now move the flashlight off to the side, and you'll be able to see your face illuminatedby the flashlight. For the inspection in question, one view looking from a bit below, and another from a bit above might be prudent.
 
All the current photos are indeed lighted with the LEDs on the tip of the camera wand. I have the original tooling hole in the end rib and a second hole created just for this inspection. I will try the insertion of a standalone light and turn off the camera lighting. Will report.

Steve mentioned squirting a little WD-40. Anyone know of a benign liquid which might improve crack identification?

Is there a better camera system to fit the tiny access hole?

A lot of us are doing this particular inspection at least annually, and some of us are probably going to be asked to do crack surveys in the future. As a group, perhaps we need to think about best methods and tools.
 
DanH said:
All the current photos are indeed lighted with the LEDs on the tip of the camera wand. I have the original tooling hole in the end rib and a second hole created just for this inspection. I will try the insertion of a standalone light and turn off the camera lighting. Will report.

Steve mentioned squirting a little WD-40. Anyone know of a benign liquid which might improve crack identification?

Is there a better camera system to fit the tiny access hole?

A lot of us are doing this particular inspection at least annually, and some of us are probably going to be asked to do crack surveys in the future. As a group, perhaps we need to think about best methods and tools.
Click to expand...
a liquid could possibly fill the crack, making it even more difficult to see. I think the answer is in a secondary light source. It seems the key is to get an off angle. The problem with the units is that the light is on plane with the camera, so get a perfect reflection. To my eye, the artifact in the pic is a scratch.
 
 
DanH said:
All the current photos are indeed lighted with the LEDs on the tip of the camera wand. I have the original tooling hole in the end rib and a second hole created just for this inspection. I will try the insertion of a standalone light and turn off the camera lighting. Will report.

Steve mentioned squirting a little WD-40. Anyone know of a benign liquid which might improve crack identification?

Is there a better camera system to fit the tiny access hole?

A lot of us are doing this particular inspection at least annually, and some of us are probably going to be asked to do crack surveys in the future. As a group, perhaps we need to think about best methods and tools.
Click to expand...
This might be an option:

visionminer.com

AESUB Blue

Disappearing state-of-the-art scanning spray - No cleaning required - Thin and homogeneous coating - Free of pigments - Developed and approved by scanning experts
visionminer.com visionminer.com

Sorry, no first hand experience, but I've thought about getting it for some 3D scanning projects I've done. It's designed for a very similar purpose.
 
DanH said:
Is there a better camera system to fit the tiny access hole?
Click to expand...
Dan,

Try the DEPSTECH Dual Lens Wireless Endoscope, 1080P Scope Snake Camera with 7 LED Lights,0.31In Lens Video HD Inspection Camera,IP67 Waterproof Borescope,16.5FT Cable for Android & iOS Phone or Tablet

Pros:
Fits through a 5/16 hole
16 foot cable that will reach back into the tail
Wireless - you can set up your phone or tablet somewhere convenient and use two hands to wrestle the cable
$55

Con:
Not articulating
 
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As previously mentioned, I've also found that adding additional bright LED lighting can make a big difference.
 
Do a test scratch and crack on scrap and check it with similar lighting. The enlarged pictures appear to me to have the same grain as the adjoining material and to me that would be a mark or small scratch.
 
It's a tool mark, possibly from the original inspection camera dragging along the spar.

See if you can turn down the LED illuminator or mask it off with some tape.
 
And now, the rest of the story....

Tip 'o the hat to those who suggested auxiliary lighting. Lots of LED options these days. Turns out there is a type called COB light strip, in this case USB powered. Easily slips through a 1/4" hole.


Look, an official Petit Jean goody bag battery pack, courtesy of our friend Bill.

Pack II.jpg


Stuck it to a narrow aluminum strip. Worked best when pointed away from the subject panel, so light was diffused.

In Use.jpg


Compare this with the grainy mess I posted previously...schazam!


Sample 1100w.png
 
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So, Dan. You have a "two holer" RV-8? 😳 Can I assume you took the most recent photo with the camera in one hole and the light in the other?
 
gnuse said:
So, Dan. You have a "two holer" RV-8? 😳 Can I assume you took the most recent photo with the camera in one hole and the light in the other?
Click to expand...

Correct. The SB allows enlarging the existing tooling hole to 7/16. I'm pretty sure the COB strip and the scope will both fit through a hole that large. I elected to go with a second small hole early on. It allowed backing the camera away from the spar surface, a prior attempt at better pictures. I doubt there is any practical difference between two small holes or one large hole.

BTW, a small strip of aluminum tape closes HS inspection holes until next year.
 
There’s no substitute for adequate light.

Back when I went through NASA photography training (we did a LOT of that….), the first lesson on day one - repeated frequently - was that “if there’s no light, there’s no picture!” The human eye/brain combination can look at a poorly lit scene and fill in details - but the camera can’t be fooled. It’s amazing how the focus and resolution of a picture improves with adequate light.
 
DanH said:
Correct. The SB allows enlarging the existing tooling hole to 7/16. I'm pretty sure the COB strip and the scope will both fit through a hole that large. I elected to go with a second small hole early on. It allowed backing the camera away from the spar surface, a prior attempt at better pictures. I doubt there is any practical difference between two small holes or one large hole.

BTW, a small strip of aluminum tape closes HS inspection holes until next year.
Click to expand...
I found some tape dots on Amazon to cover my inspection holes...no need to offer another entrance for a critter. I went the centered 7/16" hole route and regretted that my "tooling hole" had been filled over. The other unfortunate news was it wasn't located where the drawing thought it was. Thanks for sharing your finding......it is a yearly event that we get to enjoy. Better than my hangar mate however that we found cracks on and had to installed the kit. I guess this subject has gone quiet, but I still wonder the cause of cracking......time, acro, prop wash, bad luck, etc.
 
gnuse said:
I found some tape dots on Amazon to cover my inspection holes...no need to offer another entrance for a critter. I went the centered 7/16" hole route and regretted that my "tooling hole" had been filled over. The other unfortunate news was it wasn't located where the drawing thought it was. Thanks for sharing your finding......it is a yearly event that we get to enjoy. Better than my hangar mate however that we found cracks on and had to installed the kit. I guess this subject has gone quiet, but I still wonder the cause of cracking......time, acro, prop wash, bad luck, etc.
Click to expand...
DanH said:
And now, the rest of the story....

Tip 'o the hat to those who suggested auxiliary lighting. Lots of LED options these days. Turns out there is a type called COB light strip, in this case USB powered. Easily slips through a 1/4" hole.


Look, an official Petit Jean goody bag battery pack, courtesy of our friend Bill.

View attachment 54876

Stuck it to a narrow aluminum strip. Worked best when pointed away from the subject panel, so light was diffused.

View attachment 54877

Compare this with the grainy mess I posted previously...schazam!


View attachment 54878
Click to expand...
Now that is a slick way to get rid of cracks. Need to market that. Oh, Wait there never was a crack to start with just an illusion. I do like the outcome though
My luck varies Fixit
 
That’s great Dan!
COB, if anybody cares, Chip on Board, “builds” the LED directly into the substrate, rather than a discrete LED surface mounted.
So, density of the LED’s is much higher. This makes for good intensity, lower surface brightness, and better uniformity. I can see how that kind of lighting would work well for rendering the surface.
 
DanH said:
Correct. The SB allows enlarging the existing tooling hole to 7/16. I'm pretty sure the COB strip and the scope will both fit through a hole that large. I elected to go with a second small hole early on. It allowed backing the camera away from the spar surface, a prior attempt at better pictures. I doubt there is any practical difference between two small holes or one large hole.

BTW, a small strip of aluminum tape closes HS inspection holes until next year.
Click to expand...
Another option, I use a small piece of electrical tape to cover the hole. Seems to be working fine.

Chris
 
Hi Dan, from my experience as a Quality engineer in the medical device industry (specifically endoscopes, laproscopes, arthro-scopes, if you can adjust light source intensity it helps greatly. Another method is a pale cellophane in pink or red will allow for viewing more detail without reducing light intensity. Incidentally it looks like a crack at the rivet hole
 
In the SB photos of the example cracks (plural) usually showed up in multiple rivets. If you just have this single rivet showing this possible crack it is probably a scratch. Continue to monitor.
 
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