noise."Mechanic: Terminology Explainer · 1:45am Sep 16th, 2021
My last blog post, we talked about some railroad slang. Like, you don’t go to dinner, you go for beans. Pull out a drawbar, you pulled a lung; if you get the draft timbers, too, you got the secret works. Heaven help you if you go in the ditch.
But there’s proper terminology, too; locomotives have notches in the throttle (usually notch 1-8, IIRC), rail cars have an “A” and “B” end and you’d better be able to tell them apart. Also locomotives have a front end which can be conveniently identified in the US by the letter “F.”
We’ve got lingo for days at the shop, a combination of things all mechanics say and sort of ‘in jokes,’ but this isn’t a blog about those. No, this is more of the “A” end and “B” end kind of thing, what automakers call stuff. You’ll be shocked[/sarcasm] to know most of it isn’t standardized.
So grab your juice box, we’re gonna go on an adventure!
I couldn’t tell you off the top of my head how many auto companies there are which sell cars in the US currently. GM, Ford, Chrysler Stellantis, Toyota, Honda, Volkswagen, Mercedes, Tesla, etc. And while there are some names they, by law, have to call things (and even that gets fuzzy), by and large they can call a part whatever they want to.
Obviously, in the aftermarket there’s more ‘universal’ names for ‘universal’ parts (I don’t mean that fit universally, I mean that all cars got ‘em). If I tell you that a car needs windshield wiper blades, you have an idea what I’m talking about, and if you were working at a parts store, you’d look up what wiper blades fit that year, make, and model. You wouldn’t worry if Tesla calls them ‘aerodynamic windscreen squeegees’ or Mercedes says it’s a Scheibenwischerblatt.
I can tell you, though, when you work at a dealership as a tech, some of the parts guys get downright snotty if you call it the wrong thing. Back when I was at a GM dealership, I needed to get a price for an alternator on a GM product.
They looked down their noses at me and said ‘it’s called a generator.’
‘But it isn’t a generator, it’s an alternator. It makes AC current which goes through a FULL BRIDGE RECTIFIER.’*
‘GM calls it a generator as they have done since electricity for automobiles was invented.’
And while I suppose that gave them a moment of superiority at the dumb tech who didn’t know GM hasn’t updated their parts catalog since 1920, in the end it wasted everybody’s time. Mine especially.
_________________________________
*I don’t remember if automotive alternators actually have full bridge rectifiers in them or some other arrangement.
Likewise, every now and then my manager, who’s worked for GM since, oh, about 1920 (to hear him tell it) gets frisky when I call a GM computer by a generic name.
‘That truck’s got a code for a failure in the ABS module.’
‘It’s not the ABS module, it’s the hydraulic control unit.’
So of course I got back at him shortly thereafter when I was working on a Ford. He can’t recognize different kinds of Ford cars, they’re all Focuses to him. Anyway, it had a fault in what anybody would call the HVAC module (or climate control module), but of course Ford doesn’t call it that; on that truck it was the EATC module.
(Electronic Automatic Temperature Control)
All of y’all who have a car, think about sitting in the driver’s seat and looking at that panel in front of you that’s got warning lights and dials and maybe a fancy digital thingy to tell you stuff about your car. Generically, that’s usually called the Instrument Panel Cluster, although of course each automaker has their own name for it, especially if it’s got other functions. Some Fords, it’s the HEC, the Hybrid Electronic Cluster. On a Chrysler, it might be the CCN, the Cabin Compartment Node (and on some, it might be the CCN/CGM because it’s also a central gateway module). It could just be the “Meter” on an Asian car, or the “Combination Meter.”
[I’ll be honest, there aren’t going to be very many Asian or European names for things because I don’t know those cars as well and usually use generic names for their components.]
When you go to unlock your car with the little remote buttons, if you’ve got a GM you’ll most likely be sending a signal to the RKE module—remote keyless entry. Ford, it might be the Remote Receiver Module, and in Chrysler you’ll get the WIN or the WCM (Wireless Interface Node or Wireless Control Module).
Ford has also long had the GEM—Generic Electronic Module—which does whatever functions Ford wants it to do. It’s the sort of ‘not otherwise specified’ of older Fords, to be honest.
GM has the DDM, the Driver’s Door Module, and the PDM which I bet you can guess what it is (and where it goes). Chrysler, not to be outdone, has more door modules on their minivans, they’ve got the DMFL, DMFR and then since it would be too obvious to have the rear doors being the DMRL and DMRR (and since they’re power, and slide) they instead have the PSDML and PSDMR. Oh, and an automatic liftgate! That’s the PLGM (on GM it’s just the LGM; on Ford it’s probably something the GEM does).
Not to be outdone, some GM trucks have the Chassis Control Module. It drives the fuel pump (sometimes) and the trailer brakes (sometimes) and in my experience is GM trying to duplicate Ford’s Fuel Pump Driver Modules, although unlike on a Ford where the truck doesn’t start when the FPDM goes bad, GM designed their CCM to usually let the truck start but take down part of the network.
Chrysler put a Hellcat motor in it and the fuel pump gives it all it’s got.
Some of the networks on a car are standardized, they have to be to speak to the scan tool. And some of them are standardized to that even if they don’t have to speak to the scan tool; why would an automaker want to develop a separate network protocol specifically so it won’t talk to a scan tool?
Well, if it’s cheaper to build or wire, maybe. Or if it’s fancier, so we have things like LIN busses and GM’s MOIST MOST network and Audi’s fiber-optic radio ring network that’s diagnosed with a special lollipop and I could go on and on although I’d have to snag a bunch of network diagrams from different vehicles and figure out what all the different networks and subnetworks are and I’ll be honest, nobody wants to read about that. Not unless it actually comes up in a blog post about network diagnosis, anyway.
Undercar parts also get their own names, even when it does the same thing. GM has purge solenoids which let metered amounts of evaporative emissions into the engine. Ford also has the same thing, but on a Ford it’s a PMV (pulsewidth modulated valve). Toyota loves calling those little emissions valves VSV for ‘vacuum switching valve’, and they’ve got a bunch of them so you’ll see things on a diagram like CAN-VSV and EVAP-VSV and so on (IIRC, been a while since I looked at a Toyota vacuum/emissions diagram).
Chrysler keeps changing the names of the parts so nobody knows what to order. Is it a LDP? NVLD? ESIM?
You may wonder what brought this all about, why I bothered to write this blog post (besides that it’s an excuse to post pony pictures).
My next blog post is about a Chrysler that had a similar electrical failure to a Ford I’ve blogged about before, and so I used some of the Ford terminology to describe the problem and solution, even though of course that’s not what Chrysler calls those parts or systems. I think it’s easier for y’all to follow along if I sort of genericize some of the lingo, rather than strictly stick to OE descriptions and names, especially if it really doesn’t matter in terms of the diagnosis and the repair. Obviously, in some cases it matters, and in those cases I will give you a more complete description.
Also, y’all thought I was kidding at the very beginning of the blog post when I told you that in the US, locomotives have an “F” on them (by law!) so you know what the front is.
I wasn’t kidding.
Obligatory snowpony picture for the outro!
To further explain that little ‘F’—that’s the direction that the locomotive will go when you want it to go forward. While you might think this is obvious, not only are some locomotives symmetrical from front to rear (such as the GG1), and sometimes they were configured to run long hood forward. Huron and Eastern 101, pictured above, runs short hood forward, whereas its sister 105 was set up to run long hood forward:
railroadmichigan.com/he105s1.jpg
Source
EDIT: for those who are having trouble finding it (it’s small), look for a white letter “F” on the blue side sill next to the yellow handrail. It’s way more obvious on 101; on 105 it’s in the same location but on the other end of the locomotive.
I'm sure some of the naming things are so they can 'own' them rather than a generic name that belongs to everyone. It's also why there is so many annoying variations in card machines at various stores while the hardware is pretty much the same
Ok. I have to plead ignorance. When you mention the F, do you mean there is literally a letter F that can be seen in those train pictures? If so I admit to not being able to find it.
Back when the cheap and reliable Toyota trucks used to have vinyl letters on the un-embossed tailgates to spell out TOYOTA, I figured out that, with an extra set of letters, I could easily alter mine to read COYOTE. So I went down to the Toyota dealership and asked for a set of tailgate "decals."
Oh boy...
After a half-hour lecture on why they aren't decals, the guy condescended to order me a set. I don't remember what he called them because the term was so far removed from accurate or descriptive that it never stuck in my head. But I did eventually get my COYOTE tailgate.
5582561
There is literally a letter F, yes. It’s by the front steps, kinda directly above the front wheel.
Here’s a closeup of a UP locomotive:
ewscripps.brightspotcdn.com/dims4/default/1826bfc/2147483647/strip/true/crop/960x720+0+0/resize/960x720!/quality/90/?url=http%3A%2F%2Fewscripps-brightspot.s3.amazonaws.com%2F4d%2F70%2F52ab6c4a47518f4630892300c2a2%2F234355139-1656867301171070-5233020196312688261-n.jpg
It’s just to the
leftRIGHT* of the red “watch your step” sticker, and that’s about where you’ll see them on most locomotives.(*Curse you left and right and my inability to remember which is which)
If anyone is curious here is the relevant regulation concerning the "F"
5582568
Thank you!
As regulations go, that’s short and to the point.
Also, it doesn’t specify how big it should be, so painting a “F” that’s six feet tall on the nose of the locomotive would be legal, I suppose. Wonder if anybody’s done that with one that’s due to hit the paint booth but hasn’t yet?
On some locomotives, it JUST Isn't obvious which way the unit should go when directed to go "Forward" (like the afore mentioned GG1) Yard switchers like EMD's SW series would be good examples, as would ANY center-cab loco. But on an EMD E or F unit? Northern Pacific 7012A
5582567
Thank you. Much appreciated. Now that you've pointed it out, it seems almost painfully obvious. Lol. As one of my old professors used to say, it's only easy when you already know it.
5582572
You didn’t specify what kind of E or F unit. . . .
pbs.twimg.com/media/EjrakfzVcAAeMBy?format=jpg&name=small
Source
I guess when you need a switching locomotive, whatever you can get will do
Be curious to see if B units normally had the front labeled. As I’m sure you know, the cab window is an aftermarket modification, but B-units did have a hostler stand in them from the factory.
Here’s some more discussion of Haysi #1. I haven’t clicked through the links yet, but boy did that unit get my attention.
5582574
Yeah, I run into that all the time when I blog or write stories. I know it, so surely all my readers do too. . . .
That’s one nice thing about blog posts, not only do I get to share some stuff I know (or learned in the process of writing) which might not be common knowledge, but I also learn new stuff on the way, too. So it’s a win for everyone!
And I bet if you live in America, next time you see a train go by, you’re gonna be looking for that little “F” on the front of the locomotive.
"It's like A Tribe Called Quest--you got to say the whole thing!"
Huh, I always thought they made the locomotives symmetrical so they could run them an equal number of hours in each direction to normalize wear and tear. I learned something! (and I'm going to bed)
Mercedes calls their body computer the SAM (Signal Acquisition Module [or whatever that is in German]). To help confuse you, there's a front SAM and a rear SAM.
I think my favorite abbreviation for a control module has to be Chrysler's security module the 'SKREEM.' idk what it stands for lol. Antiquated by 'SKIM.'
Then you've got the generic CHMSL, which is also pretty funny.
As for German, my favorite German car term is 'Heissfilmluftmassenmesser.' Literally 'hot film air mass meter.' It's just silly because it's such a long word.
Volkswagen for a while used an abbreviation for themselves (Volkswagen Auto Group) in all literature and on parts, but you'll notice that sometime in the early 2000's they stopped referring to themselves as 'VAG' in favor of 'VWAG.' Can't imagine why lol.
I am amused by this, in the 'yep, BTDT' way.
What's really fun, is some auto manufacturers define functions/references in their systems that result in those references looking like a specific component rather than the function. For example, if something were to refer to a 'C5', to make something up, it would quite confuse the electronics technician troubleshooting the board who diligently measures Capacitor Number 5 and finds it perfectly fine.
More recently, my sister in law was hunting down a good price for a resonator for her vehicle. She and others were perplexed.. and I helpfully spoke up: "It's a muffler. The company probably uses an internal specific name to refer to it. Kinda makes sense, because it resonates inside."
How is onto the pony planet going? Been about 16 months now... Still remember when one came out every 3 weeks.
Well... I've seen literally thousands of those go past, and never noticed that letter 'F'.
And then there's the part on my Intrepid that was recently replaced, the sticker on which has a pentastar logo, a GM logo, and the letters SWF in a diamond, a different part number next to each logo, plus some other number below all that. Also had to borrow a socket for the weird inverse-torx bolts that were holding it in, because of course it uses something weird like that. (And the person the socket was borrowed from apparently used it for changing the same part on a Chevy, so Dodge isn't the only one who uses those weird bolts for that one part, it would seem.)
"Chrysler put a Hellcat motor in it and the fuel pump gives it all it’s got."
...Um. What?
[wikis]
Sooo looks like the F6F-5 Hellcat was driven by a Pratt & Whitney R-2800-10W Double Wasp engine that could output 1.6 MW. If you need that much power for your car's fuel pump, though, I think something is very wrong somewhere. :D
(I assume this is a joke -- but I doubt I'll fully getting it, and I'm curious about what I suspect is missing background information both to better understand the joke and because I'm curious about what the background information is in itself.)
And thanks for the blog post and comments. :)
5582555
I feel like in the case of cars (and their networks) there’s some engineering inertia, as well. For example, Ford loves abbreviations on their data lists (such as INTCAMADVERR . . . Intake Cam Advance Error) which are sometimes helpful and sometimes not (like the COPENPLAT). And there were nearly two decades of computers on cars and even some basic networks before the Feds and SAE demanded at least some standardization, so it would make sense for them to keep doing what they always did when they could.
It does leave some interesting edge cases, too. Traditionally, a PCM (Powertrain control module) controls both the engine and transmission, while an ECM only controls the engine (and might rely on a TCM [transmission control module] for shifting). Aftermarket scan tools usually have a selection for “Engine” and “Transmission”, and often if the two are integrated, you get some crossover with codes (i.e., the trans doesn’t set trans-specific codes). But you’ll usually get a unique data list. Like, for the engine you might get “Engine data,” “Misfire,” “Fuel,” etc., and maybe for the transmission you’d get “Trans data”.
Anyway, early 2000s Rams with the Cummins had both an ECM and a PCM; the ECM was a standalone Cummins module, and it communicated with the PCM that was a Dodge unit. On the aftermarket scan tool, the “Engine” is the Cummins module, and the “Transmission” is the Dodge PCM.
5582564
I’ve never seen anyone do “Coyote”, but I did see a “YOYOTA” once, which amused me.
The coolest tailgate I ever had was on an early 80s S-10, it was stamped (as most of them were back then) and painted black . . . with red reflective stuff in it, so at night in headlights, it was a red “Chevrolet.”
5582584
I don’t wanna say the whole thing if I can help it.
5582607
As far as I know, which direction a locomotive goes isn’t really a wear thing (since they’re electric motors on the axles making them go). I suppose gear wear might happen.
There are some symmetrical locomotives where it’s impractical/inconvenient to turn them for whatever reason. A lot of railroads run locomotives tail-to-tail in pairs, so you don’t have to worry about that (one of the shortlines near where I lived often did that, so you’d have a three-car train being pulled by two locomotives). Ideally, you don’t want to have to run a locomotive for a long amount of time with the engineer either looking in the rearview mirror or craning his neck, and also signal placement is based on normal running direction, so if the locomotive is running rear-end forward, the engineer might not have good visibility of signals.
5582620
I have seen that before. I think somebody copied it from Mercedes on a model or two (probably Chrysler, to be honest).
The thing I hate about Mercedes is our Snap-On tool shows their five-digit codes, but Identifix doesn’t recognize them on any model I’ve had the misfortune to work on.
The SKREEM is what happens when a Sentry Key Immobilizer Module (SKIM) and Remote Keyless Entry Module (RKEM) love each other very much. You can almost see it: SKIM + RKEM. (at least that’s how I’ve seen it explained, which is probably backwards justification)
I’ve always preferred the generic ‘third eye.’ But it is fun to baffle customers with ‘you need a lamp in your CMHSL’ or ‘the reason your DC/DC convertor has failed on your Cruze is that your CMHSL leaks water.’ (I’ll post pics of that someday, probably.)
Apparently, all German nouns are capitalized, and you can squish together however many descriptive words you need to make them. Like German birth control, or the Antibabypillen.
Meanwhile, FAG still happily prints their name on their bearings (and at a guess, FAG is a shortened version of a German conglomerate).
5582621
See, there’s you first mistake, assuming that there’s any logic outside some committee's boardroom. Parts and circuits are numbered and named what they are, and logic don’t even enter into it. Unless it’s relays, where nearly everyone adopted the DIN (IIRC) standard.
Some brands do make use of both resonators and mufflers (like GM). IIRC, they’re a tube-within-a-tube with little holes poked in them for sound purposes, and look kinda like a cherry bomb muffler, if you know what those are.
5582643
Those were good times, I remember those times.
There’s a new chapter in slow progress. Very slow progress, to be honest, but I’d like to get it out before my ninth FimFic anniversary.
5582667
I don’t know where they put it on newer (wide-cab) locos, but I assume it’s there somewhere unless the FRA relaxed their rules, which I honestly doubt. Maybe next time I’m trackside, I’ll pay closer attention.
Here is is on CSX 59, you’ll have to zoom:
s3.amazonaws.com/rrpa_photos/9756/DSC00983.jpg
It’s on the side sill, right by where the handrail bends
5582836
That’s long been a thing, even back in the 60s lots of muscle cars were rocking LOF glass . . . Libby Owens FORD. Suppliers do what suppliers do, and sometimes the automaker (or parts house) cares enough to scrub off the other logos and other times they don’t. Ford sells some international parts (for the 7.3 diesel), and they just put their own sticker over the International sticker.
Yeah, that would be inverted Torx (or E-Torx). Torx was popular, so why not make it the other way around? GM really loves it, other automakers not as much but they do use it on occasion.
It’s a constant arms race between the boltmakers and toolmakers, and the only loser is the mechanic.
5582918
You wikied the wrong thing (although it would be cool if they put a radial in a car). They’ve got a version of the Challenger or Charger (I can’t remember which) that runs a super overpowered V8, which they call the Hellcat, and now that they’ve got the motor they’ve tried stuffing it in other things. It’s a 6.2L V8 Hemi with over 700 horsepowers.
I don’t know what other cars are actually offered with it, and which ones are memes or some dude who got his hands on one and stuffed it into, I dunno, a PT Cruiser or whatever.
5583310
The generic version of the part is this:
https://www.oreillyauto.com/detail/c/standard-ignition/engine-sensors---emissions/body-switches/ignition-switch/9eb1f5a25d0a/standard-ignition-starter-switch/std0/us268/v/a/1908/automotive-car-2001-dodge-intrepid
We just pulled an OEM one from a parts Intrepid, though.
Turns out that when it gets flaky, it takes out the windows, turn signals, airbag, and vent blower along with it. Gets reeeeally hot with the windows stuck in the up position and no fan.
5583306
Yes, those were good times. 2013 to 2014. Celestia slept in really well. It was before things started to go bad. Both parents were alive and not in decline. FiM was still going strong. Hasbro hadn't stomped on content creators yet. There wasn't an endemic virus. Definitely different and better times.
5583296 And Fuchs oil.
5582607
I figured it was so a train running the same track wouldn't need to be turned and could just keep running back and forth rather than having to turn around or swap engines. That's what GO transit does with their passenger trains although they still have to do a few checks each time they change ends. Bonus points that some of their trains only run with engines at one end but have a special passenger car at the other end with a closed off station to control things from.
5583385
I was running a pony con, a good weight, coming out of a terrible depression... Yeah, it was a bit of a golden age, wasn't it?
5583413
That it was; that is was.
5583316
Thank you, though I'm afraid I still think I lack the context to understand your elaboration/explanation; relatedly, I think you missed the sheer (humorous) magnitude of my parser failure:
I don't read "Chrysler put a Hellcat motor in it and the fuel pump gives it all it’s got.", in context, as describing putting that engine in a car.
I read it as that apparently 700+ horsepower engine being the pump drive motor. As in, that's all it does, drive the fuel pump.
Hence my confusion. :D
So, I think this might be an antecedent issue? What is the "it" that the Hellcat motor is put in, and what is the "it" that the pump is giving all the pump's got? Looking at it again, I think that that second "it" might be the Hellcat motor -- but that still leaves me without an antecedent for the first "it", nor an understanding of how this relates, presuming it does, to the previous paragraph about CCMs/FPDMs.
...Is it trying to communicate that, for whatever application this "it" is, the Hellcat motor takes so much fuel that no fuel pump control system is needed (since it's always running at full power whenever the engine's running?)?
:)
5583289
"As far as I know, which direction a locomotive goes isn’t really a wear thing (since they’re electric motors on the axles making them go). I suppose gear wear might happen."
Also, if I remember correctly, under load the rear axle(s) of a bogie tend to be more heavily loaded than the front axle(s). That said, I don't think I've heard of locomotives needing to be run in alternating facings to equalize wear, either.
5583301 I remember once upon a time when I was young... well, younger. We took our car in to the muffler mechanic because it was making a loud Your Muffler Has A Hole noise. They quoted us a price that included *two* resonators. The conversation went roughly.
Me: What's that? Why do I need two of those? And why are they so expensive?
Them: Because that's the way the exhaust system works. We're using factory parts to factory specs. It will take three days before the parts get here.
Me: I don't want them. How much is it with just mufflers and pipes?
Them: We have to install them.
Then later, at our regular mechanic, for about a third of the price.
Them: Sure, plain pipes and generic mufflers. We'll have it done this afternoon.
5583308
Oh, I don't for a second doubt you. It's just one of those things that was right in front of me, that I never noticed.
5583354
Yeah, that’s an important part. If some of it doesn’t work, a lot of functions won’t, either, or they might come and go. Depends on what goes down, TBH.
5583385
I’d like to get back on a more regular schedule, but these days it seem when I make plans about literally anything work or something else promptly stomps on them. I keep telling myself things will calm down a little bit in the winter, but I honestly doubt that.
5583400
Never heard of them, are they a big(ish) brand, or do they make specialty oil only, like the stuff that goes in shock absorbers or whatever?
5583402
Yes, that’s the general reason you’d do that.
Cab cars (as they’re sometimes called) are one way that railroads can keep from turning the train or running the locomotive to the other end, or having a locomotive at both ends. I think that for Amtrak, cab cars fell out of favor for collision requirements, for a while on some routes they were using decommissioned F40 locomotives which had had their diesel engines removed but those are probably all gone now.
Freight railroads will often have two locomotives hooked rear-to-rear so when they run around the train to pull it the other way, the crew switches locomotives as well and is facing forward. The local shortline where I lived did that, since the branch where I lived was dead-end.
5592466
Times are bad WHEN they calm down. That means something has gone seriously wrong.
5583473
Actually, I’m sure you know what air raid sirens sound like, some of them were powered by a Chrysler hemi.
(volume warning, it’s an air raid siren)
When the siren’s going off, you can’t hear the motor at all!
Oh, right, so the fuel pump is giving the Hellcat engine all the fuel it can give. These days they usually duty-cycle fuel pumps (basically, the computer turns it on and off really fast) to get the desired pressure, and they never run at 100% or almost never do.
There are performance engines where that does become a bottleneck, yes. Although in general if you need to make your fuel supply system bigger, that’s not all that much of a challenge.
I would imagine on a modern locomotive that’s fairly trivial, although I’ll be honest, I don’t know for sure. Obviously, the locomotive doesn’t carry any extra weight on it when it’s pulling a train, but I could see the pulling forces tending to tug the end facing the train down slightly when compared to the front of the locomotive.
5583677
AFAIK, most cars you don’t need the resonator, but the exhaust might not sound as nice without it. It’s possible that sometimes they use the resonator to ‘tune’ the exhaust so they can have a smaller actual muffler.
However, some modern cars with Displacement on Demand do various tricks with their exhaust system and if you put non-factory stuff on the car, there could be undesirable effects. Ditto for diesels with regen, if you start modifying those you can have all sorts of interesting, undesirable side effects (like fires, for one).
5583686
Now you’re gonna be looking next time you see a train
5592467 They're a big European name in oil. When we buy stuff from the German aftermarket parts store, that's the brand of oil and fluids they carry lol
https://www.fuchs.com/us/en/
5592473
Right. :D
Oh, neat.
"Oh, right, so the fuel pump is giving the Hellcat engine all the fuel it can give."
Ah, thanks for the clarification. :)
"These days they usually duty-cycle fuel pumps (basically, the computer turns it on and off really fast) to get the desired pressure, and they never run at 100% or almost never do."
Oh, huh; neat. Thanks.
"There are performance engines where that does become a bottleneck, yes. Although in general if you need to make your fuel supply system bigger, that’s not all that much of a challenge."
Thanks.
"I would imagine on a modern locomotive that’s fairly trivial, although I’ll be honest, I don’t know for sure."
It depends on the particular motor control system used, as far as I know, and also as far as I know, different railroads tend to decide on different tradeoffs.
"Obviously, the locomotive doesn’t carry any extra weight on it when it’s pulling a train, but I could see the pulling forces tending to tug the end facing the train down slightly when compared to the front of the locomotive."
Hm. I don't know if that happens, actually. I think you may have misread what I said, though? The rear axle(s) of a bogie, not a locomotive. As in, for both the leading and trailing bogies, the front axle of the bogie will have less weight on it than the back axle. While I don't know why this happens, my educated guess is that it's from the reaction moments. If, say, a B-B locomotive is heading to the viewer's left, then the wheels will be turning counterclockwise and the reaction moments will be clockwise. The moment about a bogie's leading axle will thus, if the bogie is imagined as a lever with the axle as the fulcrum, be a force down on the trailing axle, while the moment about the trailing axle will be a force up on the leading axle. Though, admittedly, I've not worked the math on this out in any great detail, nor have I found evidence elsewhere of this explanation, or looked for it; it seems plausible to me, though, at least.
5592469
"I think that for Amtrak, cab cars fell out of favor for collision requirements, for a while on some routes they were using decommissioned F40 locomotives which had had their diesel engines removed but those are probably all gone now."
Actually, Wikipedia, at least, lists Amtrak as still having 15 Metroliner cab cars and 21 ex-F40PH NPCUs active:
https://en.wikipedia.org/wiki/List_of_Amtrak_rolling_stock#Passenger_cars
5594393
Huh, I didn’t know that. There could be factors in how it moves across the rails, too. In cars, the front and rear tires wear differently (granted, there are steering forces involved, too). There’s probably a whole bunch of science! figuring out rail wheel wear. Seem to recall coming across an article in Trains years ago about a truck design/wheel design that caused excessive derailments of a particular type of car just due to its dynamics. I think it was well cars (container cars), but I don’t remember for sure. I know they had some trouble with the RoadRailer trailers, too, which I think was in part because they’re so light compared to a normal railcar.
You probably know that the wheels are tapered so that the car centers itself and can go off-center for corners (when the wheels have to travel different distances), which might also play a part in the physics.
AFAIK, they don’t normally turn wheelsets on railcars around (although I don’t think they normally have a specific ‘front’ and ‘back’, so maybe it’s not that big an issue, and wheels just get changed when they need it?
5594393
Also (’cause I forgot):
Wonder if that’s active as in still on the roster, or active as in regularly being on trains? The article does suggest that the Metroliners are at least still used in PA.
The NPCUs used to be really common in Michigan, but then they got rid of them on every route I regularly see Amtraks on. Now we’ve got the Siemens Chargers on at least two routes.
Incidentally, still haven’t found a definitive answer as to why the open area in the middle is lit so brightly at night on those.