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#1
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Converting station(s) to dimensions in scale
Now, some data sources do not list dimensions directly, but as “Station Numbers” (often with a “STA” prefix). So you have to work out the particular dimensions between any two given station numbers. It’s not hard, just different.
If I have a scale drawing with station numbers, how do I convert that to actual dimensions ? Can you provide some examples how to do it?
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#2
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It's just subtraction! For example, if the top of the cylindrical portion of a model is at STA 100 and the bottom of the cylindrical portion is at STA 950, then the length of that section is 850 (of whatever units the drawing is using - centimeters, inches, etc). That's all there is to it.
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#3
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Yeah, I have to set things up in a spread sheet. Run a column of STA dimensions, then to a column of the deltas (differences). Then I add a column with the deltas multiplied by the model scale factor.
It's crazy when the "0" station isn't the bottom or the tip of the nose, but you just account for in your dimension table. Edit: here is an example of a V2...note for some dimensions I used STA 0, others, like some fin dimensions I use the top of the fin root so drawing the fin is easier. My weird scale is for a BT-101 body. This is an xlsx file, had to zip it to upload it. Last edited by rocketguy101 : 02-06-2021 at 10:58 AM. |
#4
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It can be frustrating when Station 0 isn't where you think it should be. In my experience, STA 0 may be tied to something like a location on the launch pad/launch rail. That way the ground segment and flight segment stations match. Even more frustrating than having to account for an oddball STA 0 when dimensioning a model is having the flight and ground segments use completely different stations when you need to work with both. You have to be aware there IS an offset (not always obvious when looking at a drawing of one or the other), and you have to know the magnitude (conversion factor, if you like) of the offset. Far easier when everything is made to align!
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#5
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As a land surveyor, I have had to work with stations and offsets for all sorts of roadway projects, shoreline projects an others. Even more fun would be when roadways with differing station numbers would cross at an intersection. Or when an older drawing had a differing STA 0+00 or used a different baseline. And then of course differing survey crews would come up with a different distance between stations which would have to be accounted for.
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#6
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Station 0
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The main reason that many manufacturers (aircraft as well as missiles) use a theoretical station 0 that is located well out in front of the vehicle itself is to allow for future versions. If you put the origin of your coordinate system exactly on the point of the nose, then any time you have a revision of the nose shape, or a growth/stretch version, or any other significant change, you would have to go through the entire drawing system and generate a new set of location dimensions for all parts, as well as re-numbering the mass properties database, and a lot of other paperwork revisions. Almost all vehicle config changes will still be using almost all of the previous vehicle parts, so why make yourself have to do a bunch of extra work? Placing station 0 out in front of the nose by two inches or two miles does not matter, as long as you know the definition of your coordinate axes.
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#7
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Quite possibly true for aircraft, but definitely not true for the Atlas and Delta launch systems. As stated before, the intent for these SLVs was to ensure alignment of flight and ground segments. Hard to tank a vehicle when the swing arm misses the fill/drain coupler by 10-15 feet! |
#9
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Great! Thanks!
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"Old Rocketeer's don't die; they just go OOP".....unless you 3D print them. |
#10
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Thanks for the link; that will be a great resource to have available.
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