₣яэđĸĊ
03-20-2009, 09:25 AM
7:49 AM, Granola Land time.
Yet another damned morning wake-up call.
Part 1:
I live approx 8 miles from the Ontario Airport, down here. General Electric operates a Jet engine rebuilding facility there. They rebuild engines for the 747,57,etc series of planes. I know, I helped develop some of the CNC Lathe refinishing processes for this, waaay back in ancient days... like 1986-ish.
Anyway, they have a place they call "The Pit". it is a huge square hole in the ground, boxed in by very thick walls of concrete. Since every engine rebuilt has to go through a full throttle run-up test before going back in service, I'd want a lot of concrete tween me and the engine too.
Part 2:
I have been here in SoCal for every major earthquake since 1961. In May, 1960 I was in Concepcion Chile, and went through what is still the largest land-based earthquake ever recorded. a 9.2
Also, My father held both a mechanical and civil engineering degrees; heavy background in geology, one-time surveyor, designer of automated undergound mining equipment, on and on. When the Japanese came to study the "other end" of the huge tsunami they experienced in may, 60, they came and found my dad, to show them around.
I guess I'm trying to give the impression that, while I am not a trained geologist, or anything of the sort, between the talks dad and I had over the years, and the unusual anount of "OJT" I've had, it gives me a bit better view of these events than most folk.
The Problem:
After 12 years of sitting in this very spot, and all the chances, I still cannot tell the difference between the sound of a building earthquake, and one of these damned full throttle tests, Damnit!
The only diff between the two is that, if it's an earthquake, after about 8 seconds of the floor, rafters, windows, and my teeth rattling, the floor begins to both shake, and move.
Long damned 8 seconds, I can tell you.
Free, Jet Engine Trivia:
Did you know that the casing around the main stator for a GE CF-6 engine is purposely machined roughly 0,020 inches out of round? They are.
Heres why. According to one of the engineers there, once the engine kicks off (starts) the suction against the engine wall is so great, "that casing could be square, doesn't make any difference, in 1/2 second, it WILL be round".
The problem is when they're not running, and the plane is sitting on the ground, the total weight of the beast is so great that the engine literally "sags" until it's about 0.020 inches out of round. The tolerances are so close that the vanes of the impeller then touch, bind up, against the wall of the engine, making it impossible to start.
So.... they machine the case with shims in it, to make it 0.020 inches out of round "the other way". That way when it sags under it's own weight, while not running, the case is round :)
Fred
Yet another damned morning wake-up call.
Part 1:
I live approx 8 miles from the Ontario Airport, down here. General Electric operates a Jet engine rebuilding facility there. They rebuild engines for the 747,57,etc series of planes. I know, I helped develop some of the CNC Lathe refinishing processes for this, waaay back in ancient days... like 1986-ish.
Anyway, they have a place they call "The Pit". it is a huge square hole in the ground, boxed in by very thick walls of concrete. Since every engine rebuilt has to go through a full throttle run-up test before going back in service, I'd want a lot of concrete tween me and the engine too.
Part 2:
I have been here in SoCal for every major earthquake since 1961. In May, 1960 I was in Concepcion Chile, and went through what is still the largest land-based earthquake ever recorded. a 9.2
Also, My father held both a mechanical and civil engineering degrees; heavy background in geology, one-time surveyor, designer of automated undergound mining equipment, on and on. When the Japanese came to study the "other end" of the huge tsunami they experienced in may, 60, they came and found my dad, to show them around.
I guess I'm trying to give the impression that, while I am not a trained geologist, or anything of the sort, between the talks dad and I had over the years, and the unusual anount of "OJT" I've had, it gives me a bit better view of these events than most folk.
The Problem:
After 12 years of sitting in this very spot, and all the chances, I still cannot tell the difference between the sound of a building earthquake, and one of these damned full throttle tests, Damnit!
The only diff between the two is that, if it's an earthquake, after about 8 seconds of the floor, rafters, windows, and my teeth rattling, the floor begins to both shake, and move.
Long damned 8 seconds, I can tell you.
Free, Jet Engine Trivia:
Did you know that the casing around the main stator for a GE CF-6 engine is purposely machined roughly 0,020 inches out of round? They are.
Heres why. According to one of the engineers there, once the engine kicks off (starts) the suction against the engine wall is so great, "that casing could be square, doesn't make any difference, in 1/2 second, it WILL be round".
The problem is when they're not running, and the plane is sitting on the ground, the total weight of the beast is so great that the engine literally "sags" until it's about 0.020 inches out of round. The tolerances are so close that the vanes of the impeller then touch, bind up, against the wall of the engine, making it impossible to start.
So.... they machine the case with shims in it, to make it 0.020 inches out of round "the other way". That way when it sags under it's own weight, while not running, the case is round :)
Fred