TECHNICAL ILLUSTRATION+ "BC"

[JimWebb]

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(viewed 320 times)Thank you for your nice reply Brynn.    The reason I'm seeking out other technical illustrators that did this stuff "BC", before computer was an interesting period of time.  I don't want to confuse anyone but I was one of the first illustrators that used the developing program referred to axonometric projections and not isometric.   I worked Piasecki Helicopters in Morton, PA where I actually worked on the plywood mock ups of the CH-46 SeaKnight and CH-47 Chinook helicopters.  In the early 60's I and two other fellows were tasked in doing all the structural repair manuals on the CH-46 SeaKnight where all the dimensions were taken off the blue prints.   Piasecki became Vertol which eventually morphed into Boeing Helicopters.  Today Boeing uses the software CATIA in the development of all their aircraft.    The ellipse templates I used and still have was made by TIMELY.    To long to go into here the templates were made in degrees that went from 15 ? to a full circle.    I hope I can explain ellipse templates in a simple way by steps.    1. Picture a three dimensional orange.   2. Divide the orange with a vertical line passing through the center point becomes the axis.  3. another line horizontally through the center point is now the thrust or center line.  4. Visually slice the orange through the vertical axis and discard the left hand side.   5. Now you half of a sphere which you begin to slowly turn on it's vertical axis faced head on.  6.  You can then easily see the ellipses form as you turn the orange.   7. The vertical line is called the major axis where the horizontal line becomes the minor axis.   Try this your self using an orange or some other sphere.       

   

[brynn]

Very interesting

I thought axonomic and isometric were the same thing.  Or do you mean it was just the terminology that was used?

Ok, I understand what you mean about the ellipses on the thrust line.  There must be only one ellipse that would fit on that axonomic projection then.  At least only 1 that represents a true circle...I guess you mentioned 30?.

They're gone now, but there used to be a really nice animated [edit - interactive rather than animated] Inkscape drawing, that showed all the parts of a certain kind of jet....I guess it was some kind of fighter jet.  You would mouse over a part, and the name and explanation would pop up.  Actually it was a tutorial, so I'm sorry the author/artist apparently removed it.

[Lazur]

Slicing the orange is already built in.

[brynn]

Ah-HAH!!

[JimWebb]

I enjoyed reading the replies I to my posting.   I and my wife are downsizing and moving to a smaller setting where I no longer have to do property maintenance.   I'm happy to have found INKSCAPE as a creative source for what I do.   I consider my self as part of the bridge generation where I grew up using the buggy whip technology to what I happily use now.  I relish the technology I use today.     I'm amazed as to how much was accomplished "BC" where there were no hand held calculators, computers or anything like them.  It was the "slip stick" technology that dominated engineering.   It is for this reason I'd like to share how things were done in technical illustration by hand with those who are interested as there is not many of us left.
What got me started in things aviation was my actually seeing the Hindenburg flying over Philly before she crashed at Lakehurst NJ in May 1937.     Now to answer the difference between isometric and axonometric.    Boeing developed the axonometric system that used a book of tables, a protractor and proportional dividers.  I'll show you examples when I find them in my stash.
Airframes are made up all sorts of parts that set in place at crazy angles which included a number of bulkhead sections that are set at crazy  angles..    The simplest way to describe it here is that making accurate drawings of all the parts mounted at odd angles was correctly foreshortened was by the tables book that told you the correct proportional setting of the dividers.   Every part to be illustrated was set on some thrust angle such 7? or  87? .  Using the book one could determine the foreshortening used on a particular thrust angle and the correct ellipse template degree that was to be used.   Difficult to explain, but easily visualized.    I'll explain more if you like, but I was using the "layers" technique before it became a standard tool in graphics programs.

 

[brynn]

Hah!  Compared to me being from the "BC" generation, it sounds like you're from the "BBC" generation.  I've only seen the Hindenburg flights from old newsreel images.

I relish the technology I use today.

Oh, me too!  It's a whole new world out there today.  I remember with my parents' generation, it was the telephone that changed their world.  For their parents, it was indoor plumbing (they lived in the country).  For my generation, the personal computer.

So you're saying that this "layering" technique sets axonomic apart from isometric?  But for the 2D plane, the grid itself is the same, right?


By the way, you don't have to start a new topic for every message.  If you want to reply to an existing topic, click one of the 2 "Reply" buttons, as shown in the image below, circled in pink.  (click on it, to make it bigger)  However, if you want to post a message with a different subject, start a new topic, like you have been doing.

(Or you can use Quick Reply, which is below the bottom Reply button.  It doesn't have all the formatting buttons and smileys that the full editor has.  But if I just need to post a short reply, it's very handy.)

There's an option in your profile that changes slightly the message-posting routine, that might help you understand better.  Click on the Profile tab near the top of any page.  Then in the dropdown menu under Modify Profile, click Look and Layout.  Find the option "Return to topics after posting by default" and click the little box (puts a check in it).  Then be sure to click "Change Profile" button in the bottom-right corner (to make the change take effect).

I like to use that, because it allows me to proof-read my message, one last time, after it's posted, before I move on.

[Lazur]

 

So you're saying that this "layering" technique sets axonomic apart from isometric?

Axonometry is the general name of representing 3D with a Cartesian coordinate system on a 2D plane.
Each axonometric image can be described by the main axises -their directions-, and a scale factor used on the distances.
(Usually x and y axises describe a horizontal plane and z describes height.)


Isometric drawings have their axises in equal 120? to each, and have the same, 1:1:1 scale ratio in each direction.
(So then a cube has the shape of a regular hexagon; not mentioning the default axonometric grid in inkscape.)


In general, axonometry can be off from parallel/ortographic projections too.
Like, Cavalier axonometry can be useful when illustrating steel beams -where the profile of the beam is drawn in 1:1 scale on x-z plane.
(Which look you can achieve with the motion extension.)


As far as I understand the mentioned axonometry in practice was "real axonometry", meaning that the scales of the axises are adjusted to their directions so it represents an ortographic projection/ortogonal image.

[brynn]

So as far as the terminology for Inkscape's grids, which word is correct?

[Lazur]

Axonometric is the general name, and in inkscape you can set the grid to have different angles too, so that seems a reasonable wording in that vein.
It displays isometric if angle x and z are set to 30?. One could argue over the calling of those angles -z should be vertical, why implying y to be vertical instead?
Or why to call them axonometric anyway when you cannot switch between xy, xz, and yz planes to show separate grids relating to their scales.
Calling the feature triangular grid could be less misleading.

[brynn]

Calling the feature triangular grid could be less misleading.

And less confusing!

[JimWebb]

"Ahah !" The definition of isometric compared to axonometric is dead on correct !    The word I conveniently left out that nades everything work is "FUDGING", where a bit of interpolation was required..   "FUDGING" was the key word in meeting the deadlines required  by contract.  Just a bit of useless information was that all the drawings we did were taken off the actual aircraft prints we took out from the "print crib".  Some of them when opened up were over 12' long.   The other issue we had to be careful with was looking through all the engineering "EOs" attached to the prints to make sure the parts location was correct. 
Not to belabor the issue was that aircraft use the same terminology as that used in the building of a ship.   Everything is measured off the center axis of the airframe designated center line 0.0.   One views the aircraft from the aft forward where the dead "Zero" reference point is on a plate built into the assembly jig.   As an example  a cabin airframe ring  are all numbered according to their location in the assembly jig  such as airframe 52.5 is located or positioned on the axis line at 52.50 inches front the center point 0.0 in the jig.  Making things more interesting was that the same part which maybe mirror imaged had a part number which ended in either "-1" or "-2"    The "-1" meant right hand and "-2" meant left hand.  Then there was the water line which is the axis  where some parts were mounted above the water line and others below the water line.  One of the tests we had to pass in doing technical illustration was I was  handed a print taken at random from the crib where I had  to go to an aircraft being built in a jig and find the exact location of the part in the airframe.   Enough for now !

Now as to the "layers" similarity.   The first thing that was done was make a detailed scaled outline of the frame ring were going to illustrate which was done to scale and located on the axis line.  We drew grid lines on the base illustration as reference points.
From there on vellum tissue was laid on the base line drawing where layer by layer each part or assembly was drawn. When all this was completed we then traced the master inking drawing on vellum of the complete assembly.   No different than using layers in Inkscape, but easier.   

Just as an aside, I loved  building aircraft where as a little kid I built rubber band powered airplanes.  The success of  Piasecki hinged on the skills of many ""Rosey the Rivetors" who still worked after the war.   Some of the airframes we built were done by women gas welders.  Gas welding is a craft/art and not something men could do well as most of them kept blowing holes in the thinned walled aircraft tubing !   More if your interested !     

Jim