D.Carleton aegrotatio From what I have researched, all preserved examples have had both the transformers and the mercury rectifiers removed... What mercury rectifiers?
aegrotatio From what I have researched, all preserved examples have had both the transformers and the mercury rectifiers removed...
From what I have researched, all preserved examples have had both the transformers and the mercury rectifiers removed...
What mercury rectifiers?
My thoughts exactly. GG1's used AC series motors, which is why the PRR electrification ran n 25Hz. On the other hand, PCBs in the transformer...
D.CarletonIt may even be cheaper to make new molds and pour new castings.
Much more likely that individual complex sections would be cast using lost-foam, then jigged and assembled using laser keyhole welding. That method eliminates both the difficulties involved in keeping all the molds and cores aligned and in making such a large pour and then controlling the various sections' cooldown correctly.
if you are going to recast the frame, using an existing frame as the mold for the mold, keep the mold around, so after 20, 30, 40 years, cast a new frame.
A new welded frame might be less expensive and more practical?
GG1 did not have a liquid reostat. No reostat for traction power. A multi-tap transformer instead. Remember an ac COMMUTATOR motor was used, the motor design being to make ac at low enough frequency behave like DC in the motor, well, close enough to dc to get torque and traction. So you just reduce power by reducing voltage to the motor, as is done with resistors for dc motors but more efficiently with multi-tap transformers with ac. And, yes, the New Haven power that ran into Grand Central Terminal did have essentially two separae control systems, grid resistors contolled by relays (and series connection of two motors to parallel, and possibly field shunting [weakening]for dc, and multitap transformers for ac. The rebuiled would use AEM-7-dc technology, using electronics to control dc voltage to the motors.
daveklepperif you are going to recast the frame, using an existing frame as the mold for the mold, keep the mold around, so after 20, 30, 40 years, cast a new frame.
To paraphrase Arthur C. Clarke, 'you can't do that, Dave.'
Matching shrinkages to get a proper one-shot casting from molds made directly from an existing frame is an extremely difficult exercise, on top of the already-difficult matter of assuring proper gating, etc. for a quality pour of a casting that complex.
Perhaps the best approach today would be to make pointcloud measurements of the existing frame, translate these into CAD, and make the patterns, including the lost-foam patterns for the cores, directly with the correct shrinkage allowance. And then make sure someone keeps up with changes in the computer industry, CAD/CAM practice, etc. so that in 40 to 50 years the data will still be in usable shape to make more (or drive whatever cheaper and better processes are available by then).
The point of decrystallizing is that the existing frame represents a near-net-shape pattern already containing all the metal needed for a good casting, so a self-mold not taken fully to liquidus (but only to where the crystallization structures redissolve) and then properly and very slowly cooled will give you a proper underframe (needing little more than metalspraying to reach proper service dimensions) with good strength. Attempting to re-cast the underframes 'from scratch' is likely to be far more expensive, even if you have enthusiast-level donation of professional goods and services and you get good castings on the first pour.
Might be interesting, just for historical purposes, to make a set of fabricated underframes as proposed for the high-speed project. Nothing in those that a good shipbuilder couldn't watercut, hydroform, and laser-weld, and if you wanted a true high-speed GG1 that could operate at modern Corridor speeds you'd want it (even with just the chevron-spring approach)...
I seldom stray from the Classic Trains and General Discussion Forum's or else I would be behind a 'puter all the day long and never take the garbage to the curb or anything else done, but in this case I will make an exception.
Very informative discussion here. You could conclude the Pennsy was quite primitive in this frame design without the aid of CAD/CAM, watercuts, hydrofoam or laser anything and yet they built an outstanding locomotive, let alone the frame itself.
!st Semester students in my class are taught real Drafting with T squares, triangles and pencils and inking pens, on drafting and light tables. I have always received a lot of flak and resistance for this as the powers that be continually cannot see this as part of the curriculum, instead wanting the students to go directly to AutoCAD and Vulcan or GemCom. However, its still my course dammit!
I find the students have a far better understanding of what they are doing at the computerized levels with a semester of getting it done by hand on paper and actually thinking. They appreciate the beauty of their work, as did the designers of the GG1 and its components.
There is nothing whatsoever either primitive or defective about the GG1 underframes; they were at least as complex a casting as what GSC was doing with cast engine beds at the time, and the fact that they represented the only locomotives that could achieve practical Metroliner speeds at one time should tell you all you need to know. It is worth considering how the design was made, and then the patterns and cores made, and how GSC cast them -- the difficulty today being that doing the job that way involves more metal than required, the suspension is still steam-era (excellent, mind you, but the only damping provided other than friction and gravity was 'snubbers' - which were nothing but coil springs wound to a different period from the main suspension springs, similar to what's done on modern three-piece freight trucks. Those were taken off the GG1 comparatively early in their lives, which I didn't understand when I thought they were still energy-absorbing devices...
The big problem with the cast frames for high speed was that they were very heavy for the job they actually had to do. In part this was rationalizable because all the buff and draft force went through the underframe, but there got to ba a major problem (as with steam locomotives) when Metroliner service provided only relatively short Amfleet consists (with those inside-frame disc-braked trucks) which were (obviously) not intended to help stop hundreds of tons of locomotive too. The fun came in when you look at how you apply braking effort to a GG1 traveling at high sustained speed -- the engine trucks don't do much good, and the quill axles ... have shrunk tires on them, like 57"-drivered steam locomotives. These had to provide a more-than-expected share of the brake force, which led to what we really should have seen coming...
For any practical rebuilding of GG1s for 120mph service, you'd need reliable braking from that speed using consists capable of running at that speed. All the Gibson rings or fancy clips in the world won't accomplish that for long enough. Hence reduction of mass in the design, and one place to do that was a redesign of the underframe that would not suffer crystallization as those castings did as they aged, with a bit more application of good design rather than generous factor of safety in the detail design at potential stress-raising areas.
Well heck. Thanks for the in depth informative answer. A fellow colleague I work with daily is a PhD Metallurgist. I will bring up this crystallization factor with him and get his take on the new process required.
Share with me what you find, in detail. Particularly any improvements in alloy metallurgy (or casting technique) that would produce better castings in this particular service.
You might also see what he thinks about eliminating the pedestals and stress associated with them through the use of the canted chevron springs to the axleboxes...
RME- Will do. His PhD is in Physics and he has specialized in Metallurgy for many years now, mostly with aluminum and tungsten studies with aircraft materials and also works on the Synchrotron in Saskatoon. He is also somewhat of a Railfan as his dad was an engineer (driver) in India. You never know what we may find out.
While you have him: ask if he thinks a modern cerium steel would be better than classical 'high dynamic' for lightweight Timken rods.
I'm writing this stuff down. Looks like Im going to have to take him out for lunch this week!
Very pleased to see such a robust exchange of ideas and thoughts about rebuilding a GG1 If the GG1 had continued in service the very things discussed would have undoubtedly been done or very close. As with UP's 844, Challenger and now Bog Boy, modern technology is being applied to ensure a safe and Federally compliant engine is attained Remember Big Boy sat idle for over 50+ years and it's still being rebuilt. Maybe some one should contact the UP steam engine shops in WY to get their take on ageing cast metals. After all Boy Boy weighs over a Million Pounds and that's a lot of energy rolling down the rails at 60+MPH. Challenger weights in right at a million pounds.
RME- Have not forgotten you. I put the questions to my colleague and followed it up point form questions in an email. Simply awaiting a response. Hopefully he has something to say.
Where is this?
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