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Author Topic: FAQ: Visually Estimating Electra Tire Diameter - old photos  (Read 46734 times)

Martin X. Moleski, SJ

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Re: Electra Tire Diameter
« Reply #30 on: June 14, 2012, 07:24:17 AM »

I'm not sure why we're still speculating on the size of the tires given the inspection report.

I think the question arose from Jeff Glickman's use of the tire diameter in his analysis of the Anomaly Formerly Known as Nessie (AFKaN).  It's not clear to me whether Heath is trying to contradict or confirm Jeff's interpretation.
LTM,

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« Last Edit: June 14, 2012, 09:00:52 AM by Bruce Thomas »
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Heath Smith

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Re: Electra Tire Diameter
« Reply #31 on: June 14, 2012, 04:05:41 PM »


I tried to rotate the Mobil Oil photo about 1.9 degrees counter clockwise to compensate for the camera tilt.
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John Ousterhout

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Re: Electra Tire Diameter
« Reply #32 on: June 14, 2012, 10:15:42 PM »

"...If we assume that Earhart was about 5'7", and she is about 4ft away from the tire, can you approximate the tire diameter on the vertical?...
Assuming the vertical distance from the top of AE's (bent) head, down to the bottom of her right shoe (not accounting for heel lift), I measure 71-1/2 mm on my screen.  Note that each pixel is about 3/4  cm, so there's a LOT of potential error here.  The tire appears to be about 37-1/2 mm across the diameter, at an angle from the vertical that includes both completely rounded edges.  Since it is at a moderately oblique angle, there will be some distortion, and since the tire is not spherical, some additional distortion.  Ignoring those distortions gives an apparant and relative tire diameter of 35 inches.

Cheers,
JohnO
 
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Andrew M McKenna

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Re: Electra Tire Diameter
« Reply #33 on: June 15, 2012, 02:09:14 AM »

Heath

I don't think anyone is getting uptight about this thread, it has been an interesting exercise.

You say you found something that you didn't agree with, and at this point I'm not sure I understand exactly what it is that you feel points to anything other than the 35x15-6 tires, which are both indicated by the standard equipment list for the L-10, and the inspection report as it came out of the repairs from Lockheed.  I don't believe there is any documentation that the tires were changed after this point, and we can probably calculate the number of T/Os and landings made after that point.

If anything, this thread seems to confirm that the tires are approximately 35 inches in diameter. 

Is there something that still indicates otherwise in your mind?

Andrew
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Heath Smith

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Re: Electra Tire Diameter
« Reply #34 on: June 15, 2012, 03:20:15 AM »

Andrew,

The museum wheel clearly is not what would be a standard 35x15-6 tire. It is a 30 inch tire at most. The outer rim is 8". If you only assume the outer rim was the same size on Earhart's Electra, the tire size ends up being nearly identical as the museum piece. While it is possible that the tire on the museum piece is non-standard, it is also possible that the hub and tire on the piece became a standard. This also is surely not a case of someone hacking on some old tire where a 36" tire belonged as a 36" tire would not fit in the forks. It is logical to assume then that the forks and tire sizes were either optional equipment or Lockheed produced several incarnations of all of the above, fork, tire, and hub.

There are at least a couple of photos of Earhart squatting next to a tire. If she is a foot or two away from the tire, and she is 5'7" tall, it is not plausible in my opinion that the tire is 36 inches.

I have measured other objects in some of the photos like the standard oil drum that is 33.5 inches tall near the tire and after adjusting for distance, the tire is not 36 inches tall. It is at most the same diameter as the museum tire.

There are many other photographs out there yet to be look at and I will continue to do so. So far, everything that I have looked at does not indicate a 36" tire but a much smaller tire.
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Heath Smith

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Re: Electra Tire Diameter
« Reply #35 on: June 15, 2012, 03:34:24 AM »

Quote
Ignoring those distortions gives an apparant and relative tire diameter of 35 inches.

John,

Attached is the photo with a red line where I peg her height at 5'7". Is that about what you had selected? Note that he her head is slightly tilted downward so I am slightly above where you would consider the top of her head.

If you do nothing else but assume the same pixels per foot, the tire as shown by the red line is about 32 inches. This is of course not adjusting for perspective, since the tire is closer than Earhart, it's actual size is less than 32 inches.

Once you adjust for perspective, say approximately 4 feet (which is just a guess of course) the tire is much less than 32 inches, more like 28 inches. Interestingly enough, the size of the outer rim is 8 inches, the same as on the museum wheel.
« Last Edit: June 15, 2012, 03:38:24 AM by Heath Smith »
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Monty Fowler

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Re: Electra Tire Diameter
« Reply #36 on: June 15, 2012, 07:16:03 AM »

It's an interesting excercise, Heath, and something that I do not claim to have even the remotest expertise in. I would gently suggest, though, that since you have to keep using words and phrases like assume, approximately, adjust for, not plausible, etc., in all of your posts, it causes me, at least, to question your results.

I am not a photo interpreter or forensic photo analyst. I push paper for a living. I have, however, been kicked in the head enough times to know when I don't know something, and to leave those things to people with greater expertise than mine. It's interesting speculation, but at the end of the day, it's the paperwork that carries the weight, as far as I'm concerned. That, again, is just my opinion.  ;D

LTM, who will now resume his regularly scheduled pushing,
Monty Fowler, TIGHAR No. 2189 CER
Ex-TIGHAR member No. 2189 E C R SP, 1998-2016
 
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C.W. Herndon

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Re: Electra Tire Diameter
« Reply #37 on: June 15, 2012, 08:37:11 AM »

Heath, here is a picture of the AE Electra being serviced in Karachi. Notice that one of the mechanics is actually bent over the tire under the port side engine.

http://earchives.lib.purdue.edu/u?/earhart,510
Woody (former 3316R)
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Bruce Thomas

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Re: Electra Tire Diameter
« Reply #38 on: June 15, 2012, 09:10:05 AM »

I know next to nothing about photogrammetry except to know that it’s a lot more complicated than anything I or anyone else has tried to use in this thread to reconcile the difference in opinion about the diameter of AE’s tires.  That’s why I posted earlier the link to the video that shows perspective playing such a large role in complicating the determination of the relative size of two objects in a single photo.  Then John Kirk pointed out the role of “tire squat” in complicating any comparison with the tire diameter versus the height of a 55-gallon drum (which, incidentally, is cited to be both 33.5” and about 34.5” in the same Wikipedia article).

Many such critical considerations (can you say “trompe l’oeil"?) come to mind:  How high is the camera above the ground?  Is the ground level? That is, is the photographer standing on a small rise or in a slight depression, so that the lens may not be in the same plane as the objects being compared?  Are the two objects being compared equidistant from the lens?  Are shadows distorting important detail?  What are the lens characteristics of the camera? And there are myriad other considerations that require the expertise of a person like Jeff Glickman to investigate and reconcile to obtain a reliable answer.  After all, how much time and energy went into trying to measure the length of AE’s shoe by comparing it to the rivet spacing on the aircraft?

That said, I’m just as intrigued as others with this matter of tire size, and cannot hold back in trying to apply my own amateurish hand and eye and naïve knowledge to the problem. It’s shaping up to be a lot like those witness accounts of a crime that differ substantively, leaving it to a jury to choose.
   
Let’s take the two pictures below for comparison purposes.  The first one shows a Lockheed 10A at the New England Air Museum (NEAM) and is from Earhart Project Research Bulletin #58.  As has been remarked in this thread, the tape measure shows that this tire is clearly 28” in diameter — well, except for one person, who assures us that the tape measure gives the tire’s indicated diameter to be 30”. 

No, I say that museum tire is indeed 28” high:  the photographer has used the détente on the measuring tape to lock it with the marking for 28” showing at the very bottom of the visible tape.  But I see the first 2 inches of the tape extending up above the horizontal plane across the top of the tire by two inches. 

Why did the photographer extend the tape those 2 additional inches?  Well, because the body of the case for the measuring tape is exactly 2”, and the two extra inches at the top come from the case’s two additional inches at the bottom.  It’s likely that the photographer ran the tape out 28” so that the end of the tape touched the floor and the 28” marking was level with the top of the tire; then he set the détente and inverted the tape,  standing the tape on its case as shown to take the picture, thereby causing the end of the tape to be seen to be 2 inches above the top of the tire.  Either way, I say that the tire shown is indeed 28” in diameter — and certainly not the claimed 30”.

Notice two other things about that picture and the landing gear shown.  First, the top of the tire appears to come about midway up that oval surface at the top of the fork.  And second, there is quite a bit of space showing between the top of the tire and the mud guard.  Neither of those would be affected by "tire squat."

Now look at the second picture, which is NR16020 being refueled in Bandoeng.  I think that the two things I pointed out in the previous paragraph support the notion that this aircraft’s tires are of a larger diameter than 28”, perhaps even as much as 35”. 

First, the top of this tire is showing significantly higher than the middle of the oval surface at the top of the fork.  And second, there appears to be significantly less space between the top of the tire and the mud guard above it than for the plane at NEAM.  Assuming that the fork assembly on AE’s plane is the same size as that of the plane photographed at NEAM, then the miserable little 3.5” of radius that is consuming so much attention in this thread is easy for me to reconcile in my mind’s eye. But are those perceptions the result of varying perspective between the two pictures?  There’s no telling.  How to reconcile this difference in amateur photo analysis?  Leave it to those trained in photogrammetry.   

So, I continue to believe in the integrity and correctness of the Aircraft Inspection Report that was signed the day before AE began the second world flight in her repaired airplane.  I’m comfortable in trusting that the main tires were indeed of the 35” diameter size.  But then, I keep hearing Ronald Reagan’s voice:  “Doveryai, no proveryai – trust, but verify.”  And I hope that the Bureau of Air Commerce inspector who signed that form (Lake? Duke? Dike?) did likewise.
LTM,

Bruce
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C.W. Herndon

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Re: Electra Tire Diameter
« Reply #39 on: June 15, 2012, 09:28:06 AM »

Bruce, take a look at the picture that I just posted of the Electra being serviced in Karachi. Note the one mechanic leaning over the port side tire and compare his size to the size of the tire and then measure 35 inches on your own leg.

Also I have been doing a little research on the "oil drums" used to store fuel. It appears that the size of the drums was not standardized until sometime during WWII so we can't be absolutely sure of the size of the drums in the pictures. See writeup below.

http://en.wikipedia.org/wiki/Drum_%28container%29 (I changed your link -- those drums you pointed to were too loud!  --BT)
Woody (former 3316R)
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« Last Edit: June 15, 2012, 09:35:04 AM by Bruce Thomas »
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Bruce Thomas

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Re: Electra Tire Diameter
« Reply #40 on: June 15, 2012, 09:39:25 AM »

Bruce, take a look at the picture that I just posted of the Electra being serviced in Karachi. Note the one mechanic leaning over the port side tire and compare his size to the size of the tire and then measure 35 inches on your own leg.

Also I have been doing a little research on the "oil drums" used to store fuel. It appears that the size of the drums was not standardized until sometime during WWII so we can't be absolutely sure of the size of the drums in the pictures. See writeup below.

http://en.wikipedia.org/wiki/Drum

Well, since I don't know how tall that fellow in the picture was, and you don't know how tall I am, I'm not sure what conclusion can be drawn there.  I do know that 28" comes to mid-thigh for me, and 35" falls a lot short of my hip.   :)
LTM,

Bruce
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C.W. Herndon

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Re: Electra Tire Diameter
« Reply #41 on: June 15, 2012, 09:53:01 AM »

Well Bruce, I am 5' 8" tall and 35" comes to right at my hip joint, just about where the top of the tire appears to be on the fellow in the picture.
Woody (former 3316R)
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Irvine John Donald

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Re: Electra Tire Diameter
« Reply #42 on: June 15, 2012, 02:53:36 PM »

I believe we should keep in mind that you are measuring one tire from very clear shots with other items in the foreground/background to get a scale from it.  Jeff Glickman has no such luxury when he says it is "Approximately: 36" diameter.  He has quite a fuzzy picture with nothing to give an easy reference to.  His estimate is based on a triangulation of landmarks from a photo in 1937 with approximate measurements from lst year's expedition.

As an exercise this is a lot of fun to work out and speculate about but I think you cannot say definitively that the "Bevington Object" is a 36" versus 28 tire".    Even Jeff isn't willing to come out 100% and say its a wheel or tire never mind saying its 36" for sure.  He only says that it "could" be a wheel assembly.
Respectfully Submitted;

Irv
 
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C.W. Herndon

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Re: Electra Tire Diameter
« Reply #43 on: June 16, 2012, 09:10:48 AM »

This post is to pose some questions for you guys out there who are, or have been, aircraft mechanics.

1. I have noticed that the tire in the picture of the Electra landing gear from the "museum picture" appears to be new.
2. Can a 35x15-6 tire that fits the Goodyear 6HBA wheel be purchased today?
3. Can a different sized tire that will fit the Goodyear 6HBA wheel be purchased today?
4. Could a modern wheel, with an 8" flange, and a modern 28"-30" tundra type tire be fitted to the Electra landing gear?
5. Does anyone know how to get a drawing with dimensions of the Goodyear 6HBA wheel?

Just some questions that have come to mind after looking at the museum tire picture.
Woody (former 3316R)
"the watcher"
 
« Last Edit: June 16, 2012, 10:36:39 AM by C.W. Herndon »
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Heath Smith

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Re: Electra Tire Diameter
« Reply #44 on: June 17, 2012, 07:13:41 AM »


Woody,

I finally had a chance to look at the photo you posted. It is a bit tricky because the tire is a bit further away than the guy standing in front of it. See the attached picture. The red lines approximate the height. I estimate the height to be 28 inches.
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