Help with Photo Measurements

[Bruiser]

I know this is a long shot, but I also know there are people on the forums with mad skills so I thought I would ask.

Could anyone help with turning this photo into a drawing with measurements?


I am having trouble figuring out the length of each section. There are the given measurements to work from such as the diameter (17.23) and the length of the motor (185.01) but I have measured it three times now and come up with something different each time. What I need is the nose cone length and the lengths of the different payload sections. Basically I need the dimensions forward of the rocket motor. I can do the math to make it 1/6.9 scale.

Anybody good at this sort of thing?

Thanks,
Bob

 

[Zeus-cat]

It might be easier and more accurate to just look up the actual dimensions if you know what the rocket is.

 

[Bruiser]

Well it is a black brant V sounding rocket so some of the dimensions are known. The payload and nose cone dimensions change though based on the payload specific to each launch. So in this case a photo is what there is to work from...

Bob

 

[Nytrunner]

For sport scale, stick the photo in paint or another photo editor and compare pixel lengths

 

[Bruiser]

I don't know how to do that. I was enlarging the photo on the screen and measuring. I printed out the photo and measured. I also measured a photo of just the front area. Then I compared them all and I had different measurements each time. Obviously I suck at this

-Bob

 

[jlabrasca]

There was some rotation, and some vertical perspective distortion, and some barrel distortion from the WA lens. I used the white stripe on the rocket to try to straighten out and align the verticals -- but without knowing the FL of the lens and position from which the image was captured, the corrections are really just cosmetic.

Also, the left side of the airframe is obscured by the launch tower, so the diameter is just a guess.



EDIT -- Typo: The distance from the base of the nose cone to the tail should be about 151 units, not 134 units.

 

[Bruiser]

So what are those measurements? Millimeters, Inches?

Nytrunner gave me an idea to open it in some program and print it to the size I am building. That way I get all the measurements in one swoop and they are definitely all at the same ratio. So I looked at the programs on my computer to see what I had. I tried Publisher thinking maybe make it a banner but I couldn't find a "banner" option. Next I tried Paint and I was able to figure out how to print it on several pages.

So the measurements that are the same on all BB Vs is the motor diameter of 17.26 inches with a length of 185.01 inches. After several enlargements it seems 900 percent is the closest. It not exact on though. At 1/6.9 scale the motor on my rocket should be 26.81 inches and 2.5 in in diameter. The enlargement of the photo to 900 percent came out with a length of 27.1 inches and a diameter of 2.45 inches so it is a little longer but a litter skinnier but it'll work.

Next I am going to try to work up a color drawing of what it will look like.

-Bob

 

[jlabrasca]

So what are those measurements? Millimeters, Inches?
-Bob

The Illustrator document is set up for millimeters -- but it might as well be pixels or points or picas. I was trying to get the proportions, figuring that you would be able to work out the as-built dimensions from the diameter of the airframe.

Scaled and dimensioned to at the 17.2" diameter you call out in the top post



Be aware that the numbers on the drawing are all way too precise. To appropriate precision the OAL is 360", and the tail-to-nosecone-break length is 300".

There does not seem to be a visible feature at 185" (the motor length you quote), so I cannot really even guess to what extent lens distortion and perspective are skewing the lengths. Unless you've got more information about this round, the photograph is probably not an adequate source for an accurate scale drawing.

 

[stantonjtroy]

Black Brant V courtesy of ROTW. Should be able to get accurate dimensions up to STA 0 and scale the payload/nosecone based on these proportions compared to the drawing.

 

[Bruiser]

That is one of the drawings that the baseline measurements came from.

jlabrasca, the motor length just happens to be the same length as the white stripe in the Always drawing posted above. I should have posted that as a reference earlier because all Black Brant V (or 5) rockets are the same dimensions from the motor back.

So this is what I have come up with using a combination of OR to get the outline and Paint to add the colors. BTW, the overall length in OP came out to be 52.425. I do like the way it looks and I have just enough body tube to do it. I had not ordered enough but I have a 6" piece of tubing left over from when I built my Ventris clone.


If you haven't seen it, here's my build thread https://www.rocketryforum.com/threads/ps-ii-inspired-black-brant-v.156900/

Thanks for all the help,
-Bob

 

[jlabrasca]

jlabrasca, the motor length just happens to be the same length as the white stripe in the Always drawing posted above...

Doesn't seem to be the case for this round.



I got a little tricky, mirroring the image and lining up the tip of the nosecone to get the diameter -- but I don't think I could have gotten it that far wrong,

 

[Bruiser]

Your measurement is very close. The Alway drawing is 185 and you are 184. And that is based off the diameter which just a fraction difference there is multiplied many times over when calculating the length.

It would have helped if the photo you were working from was larger. I have another I found last night that might be better. I'll attach it. Yes, I think so. You can see the space between the payload and the launcher better.



-Bob

 

[jlabrasca]

Your measurement is very close. The Alway drawing is 185 and you are 184.

-Bob

The line I drew for reference (which ends in a filled circle terminal) is 184 inches. The measured length of the white stripe is closer to 200 inches.

That is a better image. Looks like you can see the diameter in the clear, I've burned more time on this than I can spare today. If I get a few minutes tomorrow I'll take another swing.

 

[Bruiser]

Oh, I didn't realize that the measurement was to the circle. It'd be nice to confirm the measurements but printing out the picture to the size of the model I am building should be very accurate. I was thinking about the diameter being a little smaller than expected when compared to the length and I realized that should be expected with a photo. I'm pretty happy with what I have and I think I will move forward with it.

Thank for your help,
-Bob