This just struck me last night, thought the pros could probably answer. It seems like a really obvious matter, but how are diesels geared? On a car, of course, you've got either a manual or auto transmission that changes the gear ratios according to if you're going up a hill, or accelerating, or whatever. I know diesels have just the traction motors, that feed right onto the axles. What happens when a train would come to a situation when a car might need to change gears, going up a hill, accelerating, or what not? Is power just increased or decreased to the motors?(Run 1-8) Steam locos obviously didn't have anyplace to do any gearing, either. How did engineers deal with these elementary situations? Thanks for feeding my curiosity... Derek (long live Espee)
Hi Derek - Good question. Engine gearing is only from the traction motor to the axle and is not 'shiftable'. Traction motors are just jumbo electric motors and behave like any other, the harder they work or the faster they go, the more juice it takes to run them. To keep it basic, as a train starts up a grade or accelerates, the engineer adds power by notching out on the throttle and through a series of controls, the generator feeds more amperage to the traction motors making them work harder to overcome gravity or inertia. Once the train is over the top of the grade or reaches track speed, less power is required so you notch off until you're just at the level you need to maintain the desired speed. When you think about it, other than making it's own electricity with the diesel engine or picking it up from a wire as it goes along, a locomotive works on the same principles as a model train, just waaaay bigger and more complicated. Hope that helps. It can get a lot more detailed if you really want to know more. Stay tuned.
The only thing analogous to "shifting" that was done on older Diesels was "transitioning", where the traction motors, which were wired in series at lower speed, "transitioned" to parallel wiring when a certain speed was reached. Don't stand by the electrical cabinet when this took place! The "pop" and sparks were often spectacular. [ 25 April 2001: Message edited by: Gregg Mahlkov ]
The only rail equipment I know of that really did have a transmission to shift gears for speed, were the "Blue Goose" and other shop or "home made" rail cars and trucks, besides one Doodle Bug that my Grandmother and I would ride from Wichita, Kansas to Anthony, Kansas, and one time all the way to Aline, Oklahoma. The whole front end was painted in black and white chevron stripes, sort of scarey to see coming at you! Later models were diesel electric. We got to know the motormen on the old one, and several times I got to ride up front and watch him shift four times to get up to track speed, about 45 mph. I would guess the engine was a three banger Buda or Euclid engine, but it had a huge flywheel and he had shifting marks on (what I know now was a tachometer), that only went up to 400 rpm. He usually kept it between 200 and 325. That's where the exhaust sounded like Doodle-Doodle-Doodle and he's running 30 miles an hour at less than today's ideling speed!
Didn't the Kraus-Maffe (sp?) diesel-hydraulic that the Rio Grande tried 30-40 years ago have a hydraulic transmission? Also, didn't the original RDC's have some type of automatic transmissions between their 300HP diesels and the axle gears? Hank
Hank, I agree with you, although I got the impression Derek was asking about shifting gears, to change speeds. I read an article several years ago on the Kraus-Maffe rail bus that said the design was two vickers type hydraulic pumps arranged so that the driven pump was set at maximum flow, and the other pump was variable infinately from full foreward to zero flow at center, to full reverse flow. It is the same type of closed system we used on the gun turrets during the War (II). Now days several garden tractors, and full sized heavy equipment use this system. It provides almost the same control as did the steam engine. The K-M system was limited only by the horsepower driving it, the steam engine had the added advantage of the natural expansion of steam, which used to be considered "All the Power of Nature!" All that being explained, the K-M would have set the motor at its maximum torque, then changed speed by moving the pumps which would have acted like a hydraulic jack at low speed, with only the motor being the limit at full speed. A steam engine has all its horse power at any throttle setting, and can conserve some steam, water, by "Riding the Expansion when the valving is set (by the Johnson Bar) in the most effecient location just before cut off, known as the "Company Notch". A truck has to naintain a certain RPM in order to continue running, so must have gears to start even its own weight from a standing start. To "Pop the Clutch" without being in the low gear, will slow down the motor making it over-loaded beyond its maximum torque, thus "Killing your Motor". (Unless, like a drag racer, you can spin the wheels to accomplish the same thing.) Hank, I realize you knew all this, but I added the explaination for the younger guys who may not have known how all this works. I always wanted to put one of the hydro-static trannys in a go cart, but by that time there were no more War Surplus gun turret trannys left. I don't know if any automatic trannys were put in Diesels or not, I'm sure they were experimented with, but the diesel electric was adopted as more ecconomical. Yes, No? Correct me if I am mistaken, I made a mistake before. (I think it must have been about 1938.)
Thanks Watash, that's good info I had forgotten about the gun turret "motors". I do remember that you were mistaken once(!) ..... you thought you had made an Error, but later found out you hadn't Later, Hank
I'm still not quite over that one Hank. I think I had mentioned the automatic tranny some bicycle company tried about 1948, but it marked its spot like a Harley. It was based on the Dynaflow slip-n-go of the day. It still seems this was tried on some engine, but Now I'm really cornf-feused!
Watash, I think that the RDC's used by the New York Central in the very early 50's had some form of auto-shifting tranny to help their pair of "tiny" (~300HP) V-8 diesels. I seem to remember hearing (and feeling?) them shift from a "starting" ratio into a "running" ratio. I think I was told that they used a GM tranny, but looking back, I don't know if GM had anything that could handle 300+ horses back then. Did GM make an auto tranny for WW-II tanks? If they did, a tank tranny might have handled 300 HP. Hank By the way, if you are still looking for gun turret motor, you might want to check with Uncle Sugar .... He has twelve (12) 16" mounts on the four Iowa Class battlewagons that aren't doing anything at the moment. [ 28 April 2001: Message edited by: Hank Coolidge ]
Hank, the RDC had a Detroit Diesel power plant and an Allison transmission, all GM products. You are probably right about it originating on WW II tanks, although remember GM had its Euclid earthmoving machinery division at the time in competition with Caterpillar.
Gregg, I had forgotten about those fantastic "UKES" that we kids gawked at when we couldn't find a steam loco. GM's experience with UKE's probably was why they were lead designer for tank power chassis during WW-II. However, you answered my question - The original (and maybe later) RDC's DID have a gear-shifting tranny between their Detroits and the axles. Thanks, Hank P.S. There hasn't been any "public" action with the G&SI ... probably won't be for 6-9 months when it will have become a "Fait Accompli" H Derek .... Aren't you happy(?) that you started this topic? [ 28 April 2001: Message edited by: Hank Coolidge ] [ 28 April 2001: Message edited by: Hank Coolidge ]
Ah HA! When I worked on the Borg-Warner project, (400 Turbo flyte) tranny for Cadillac was where I heard about the (tank) tranny being tried out on the rails. Thanks.
Awesome stuff guys-- thanks for letting loose, always good to start a healthy topic. I feel slightly belittled, though; too much to know in this profession and hobby, that's the great thing about it, can't ever stop learning. Sorry didn't say something earlier, been around a lot(on the net) and I forgot I posted here. Thanks for the time, I know y'all love it though. Derek Long Live Espee!!
