I am newly persuaded that the actual, official, original, Zen-master calm CERTAINTY of the engine vent rings elusive measurements have been derived. There are six different measurements out there, and thanks to analyzing ALL of them, including my own, and including trying the Bandai 1/72 PG multiplier effect to unsatisfactory results, I am now reasonably confident that the canonical measurements for these should be...
Inner Diameter (upper lip, inside): 82.56mm, or 3.25 inches exactly.
Outer Diameter (at base): 101.6mm, or 4 inches exactly.
What factors lead to this conclusion? A couple of things:
1.) ILM used imperial measurements, never metric, because they were building in America and had American measuring tapes in inches and feet, not centimeters and meters.
2.) Joe Johnston designed the Falcon to be asymmetrically symmetric, and a 3.25 ID for the 6 topside engine vents would visually balance perfectly against the four topside forward mandible pits, which were 3 inches in their ID openings and 3.5 inches in their underside OD bays that held their own array of submerged greeblies. This would also give the vehicle a 'forward' looking direction and sense of speed and motion, as the details in the front of the vehicle are always leaner/slimmer than the rear of the vehicle where they are thicker/fatter, per Johnston's own love of Formula 1 Race Car designs, the Y-Wing design, etc.
3.) Taking the otherwise excellent and useful trick of using the Bandai PG Falcon at 1/72 and multiplying each of their dimensions by 3.51152 to arrive at the Falcon's 1/20.5 scale, is actually NOT helpful in this case. This is because these engine vents were not found parts or greeblies kitbashed from another kit, and it appears that this is one area where Bandai "evened things out" and "smoothed over some irregularities" on the mandala section. Because if you use their measurements as a multiplier, you get 79mm for the ID and 99mm for the OD, which are clearly way too low (in fact, the lowest of all six measurements out there.)
4.) The only "real way" of fail-safing these measurements is not actually against the original greeblies, which certainly helps, but against the vintage Koolshade, which you can theoretically derive from the 23-louvers-per-inch industry specs of the product. But in practice you can't. Because industry specs round up or down. In reality, the only way to get the real measurement is to a.) count the number of louvers visible in the Chronicles Vehicles books top-down reference pics, and then measure how much that is against an actual piece of vintage Koolshade. When you do this, you discover 76 louvers visible in the pic from top to bottom, and on the vintage Koolshade this comes out to exactly 82.56mm, or 0.01mm off of 3.25 inches. What THIS means is that vintage Koolshade is actually 23.38 louvers per inch, meaning that the industry spec has been rounded down.
So long story short, I originally thought these were 83mm ID and 105mm OD and I am happy to stand corrected and clarify that the actual, official, and bullet-proof specs for the 5-foot Falcon engine vents are...
3.25 inches on the inside diameter.
4 inches dead even at the outside base diameter.
I have YET to build the mandala, and so the final confirmation of how does it look against the greeblies, how does it "spread" across the rear-quarter mandala, how is the parts-to-the-whole ratio affected, etc, all has to be confirmed. But I am confident enough to print all six of these out at this point with these measurements and begin building. (nota bene: if you have downloaded, used, printed, or otherwise taken my previous measurements as canonical, they are off, so please modify yours accordingly.)
(And yes, if he wants to, Sean Sides can here rightfully accuse me of reinventing the wheel in this little exercise. His numbers were the only measurements of the six I found that were spot on.)
Inner Diameter (upper lip, inside): 82.56mm, or 3.25 inches exactly.
Outer Diameter (at base): 101.6mm, or 4 inches exactly.
What factors lead to this conclusion? A couple of things:
1.) ILM used imperial measurements, never metric, because they were building in America and had American measuring tapes in inches and feet, not centimeters and meters.
2.) Joe Johnston designed the Falcon to be asymmetrically symmetric, and a 3.25 ID for the 6 topside engine vents would visually balance perfectly against the four topside forward mandible pits, which were 3 inches in their ID openings and 3.5 inches in their underside OD bays that held their own array of submerged greeblies. This would also give the vehicle a 'forward' looking direction and sense of speed and motion, as the details in the front of the vehicle are always leaner/slimmer than the rear of the vehicle where they are thicker/fatter, per Johnston's own love of Formula 1 Race Car designs, the Y-Wing design, etc.
3.) Taking the otherwise excellent and useful trick of using the Bandai PG Falcon at 1/72 and multiplying each of their dimensions by 3.51152 to arrive at the Falcon's 1/20.5 scale, is actually NOT helpful in this case. This is because these engine vents were not found parts or greeblies kitbashed from another kit, and it appears that this is one area where Bandai "evened things out" and "smoothed over some irregularities" on the mandala section. Because if you use their measurements as a multiplier, you get 79mm for the ID and 99mm for the OD, which are clearly way too low (in fact, the lowest of all six measurements out there.)
4.) The only "real way" of fail-safing these measurements is not actually against the original greeblies, which certainly helps, but against the vintage Koolshade, which you can theoretically derive from the 23-louvers-per-inch industry specs of the product. But in practice you can't. Because industry specs round up or down. In reality, the only way to get the real measurement is to a.) count the number of louvers visible in the Chronicles Vehicles books top-down reference pics, and then measure how much that is against an actual piece of vintage Koolshade. When you do this, you discover 76 louvers visible in the pic from top to bottom, and on the vintage Koolshade this comes out to exactly 82.56mm, or 0.01mm off of 3.25 inches. What THIS means is that vintage Koolshade is actually 23.38 louvers per inch, meaning that the industry spec has been rounded down.
So long story short, I originally thought these were 83mm ID and 105mm OD and I am happy to stand corrected and clarify that the actual, official, and bullet-proof specs for the 5-foot Falcon engine vents are...
3.25 inches on the inside diameter.
4 inches dead even at the outside base diameter.
I have YET to build the mandala, and so the final confirmation of how does it look against the greeblies, how does it "spread" across the rear-quarter mandala, how is the parts-to-the-whole ratio affected, etc, all has to be confirmed. But I am confident enough to print all six of these out at this point with these measurements and begin building. (nota bene: if you have downloaded, used, printed, or otherwise taken my previous measurements as canonical, they are off, so please modify yours accordingly.)
(And yes, if he wants to, Sean Sides can here rightfully accuse me of reinventing the wheel in this little exercise. His numbers were the only measurements of the six I found that were spot on.)
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