In a road vehicle the throttle can be adjusted from zero to maximum throttle by simply varying the pressure on the gas peddle. Why aren't locomotives designed this way...with a continuously variable throttle?.. i.e. why the eight settings?
I've wondered that for years. Does it have to do with the fact that the actual traction comes from an electric motor? Trolley cars have (used to have) notches on their throttles.
I don't think its the electric motor...those 200 ton dump trucks used in mines are diesel-electric also..and they have a continuously variable foot throttle much like a car does.
Seems like we talked about this a while back.
I think part of it has to do with MU'ing locomotives together. Something like three or four wires can give you enough combinations to do all eight steps.
Larry Resident Microferroequinologist (at least at my house) Everyone goes home; Safety begins with you My Opinion. Standard Disclaimers Apply. No Expiration Date Come ride the rails with me! There's one thing about humility - the moment you think you've got it, you've lost it...
Searched "throttle settings"...found nothin
Because you don’t need the ability to vary the throttle.
As Tree pointed out, you have to MU locomotives, so they need to all have the same basic settings…in that a given RPM produces a set amp rate to the traction motors.
Notch 5 on a Dash 9 is the same as notch 5 on a SD70.
Also, you would be fatigued beyond any thing you have experienced if you used a foot throttle on a locomotive…driving a automobile or a large truck is totally different.
You have varying terrain or road surfaces, and the need to accelerate and decelerate quickly for turns and stops, neither of which really applies to what a train does.
Keep in mind that a Dash 9 weighs in around 440,000lbs...if you "stomped on the gas" in one, it would slip the wheels, and something that weighs that much needs a constant steady acceleration, just like what is provided by "notches" as opposed to a variable throttle.
But a constant setting works best for how trains handle…you don’t need to stop and start often, so why go through the mechanical additions to create a variable throttle that’s not needed.
23 17 46 11
That's interesting...you mentioned "the same amp rate for a given rpm" for each power setting. So the power setting determines the rpm which in turn determines the current output of the generator.
Locomotives have to have a system to maintain speed of the engine regardless of load placed on the engine, a function which is provided by a governor. Automobiles do not need this system because they do not have an electrical transmission but have a mechanical transmission.
EMD began by designing its locomotives with eight throttle steps plus idle. It could have chosen 10, 16, 7, 9, or 25, but chose eight because (1) that was a sufficient level of "fineness" to meet users needs for the rather narrow rpm range capability of the engine without subjecting the user to needless complexity that would drive up purchase price and maintenance price, and (2) it was convenient to use 8 because of the electromechanical technology of the day. The Woodward governor applied to an EMD engine used four solenoids to effect speed control. Each throttle setting energized a different combination of solenoids, as follows (for a 16-567C):
Someone more versed in the byzantine workings of governors and electrical control systems can probably do a far better job of explaining how governor's work. Suffice it for me to say that "8" throttle notches is what we had at first and that became the convention. Today's locomotives with microprocessor controls could have a continuously variable throttle, and in effect the microprocessors govern the engine in that fashion anyway. But the 8 notches remain because it is convenient to operate in that fashion. Speed control on a locomotive has to be varied continuously anyway, in many operating conditions, in order to maintain the train as close as possible but not over the maximum authorized track speed. Thus removing the detents doesn't save any work but it does make operating memory and practice harder to replicate.
RWM
You nailed it, RWM! Now I understand how a diesel-electric throttle works (in principle, anyway). Hope you don't mind if I cut and save your response for my personal RR info file. - a.s.
RWM has it right. I'll just add that the number of notches is 8 instead of 7 of 9 or 10 because that's how many unique combinations you can make from 3 solenoids. The 4th, "D" solenoid is in the governor to actuate an engine shutdown.
The governor is basically a flyball type and the three solenoid act on a triangular plate with a geometry such that each solenoid is "worth" either 1, 2 or 4 notches. (I think A is worth 1, B is worth 4 and C is worth 2) The plate pushes against a spring in the opposite direction from that of the flyball mechanism.
The D solenoid is woth -2 (it doesn't act on the triangular plate directly) and is is picked up along with C in notches 5 and 6 to get it some exercise so it won't be stuck when it's called on for a shut down. It is also used for low idle (D + A = -1, not enough for a shut down)
If you added another solenoid, you could get 16 speed settings.
The fulcrum nut sets the speed.
-Don (Random stuff, mostly about trains - what else? http://blerfblog.blogspot.com/)
http://en.wikipedia.org/wiki/Hermann_Lemp
Besides, "notch 8" wouldn't mean anything any more (ie, full throttle).
Thanks everyone for your input... lots of very knowledgeable people on this site..
enr2099Interesting discussion. BTW, not all locomotives had an 8-note throttle. Anyone remember the throttles on some old GE's with 16 notches, or the Budd RDC's that have 4 notch throttles? IIRC some Baldwins had 22-notch throttles.
Didn't the Fairbanks-Morse locomotives also have a 16-notch throttle ? (very vague recollection here)
If you can, find some Trains from the 1960's and 1970's when there was an annual "All-Diesel" issue, and experts such as Jerry A. Pinkepank (and others whom I can't remember right now) contributed articles on such things, the MU (multiple-unit) hoses and pins, Herman Lemp's development of the electrical transmission and control system, etc.
- Paul North.
Ulrich In a road vehicle the throttle can be adjusted from zero to maximum throttle by simply varying the pressure on the gas peddle. Why aren't locomotives designed this way...with a continuously variable throttle?.. i.e. why the eight settings?
Ulrich, it seems that you may have a valid point here, despite the negative comments above, although they may ultimately have more general and wider applicability. Here's a quote from Al Krug's great website, in the "Railroad Facts and Figures" section, on the page for the Dash 9 - 44CW or "C44" locomotive, at:
http://www.alkrug.vcn.com/rrfacts/dash9.htm
under the table for "C44 Fuel Use & Horsepower by Throttle Position":
"Note 1: Notice that the Hp increases by 150% from throttle 1 to 2 [ 200 HP to 500 HP - PDN] and by 100% from 2 to 3 [ 500 HP to 1040 HP - PDN]. These huge increases make yarding trains at 10mph difficult. You must either constantly move the throttle up & down to maintain 10 mph or else apply independent brakes and work the power against the brakes making them hot. Perhaps GE had something with the 16 notch throttles on the 1960s era U25Cs."
Oddly enough, though, Al doesn't have a lot about throttle positions other than fairly extensive tables for fuel usage and horsepower output, etc., and commentary on same for each one for several different locomotives. Nevertheless, you might find some more useful information by just browsing through it at:
http://www.alkrug.vcn.com/rrfacts/rrfacts.htm
or his home page at: http://www.alkrug.vcn.com/home.html
I think I read somewhere that early Baldwins had a throttle that was virtually continuous, so you could make very fine adjustments - didn't really have notches (or at least had many notches). However the technology to do that was pushing the envelope in 1940's electronics, and it apparently was a maintenance / reliability nightmare. Eight notches were cruder by comparison but easier to maintain and use.
IIRC, the old GE's only had 8 engine speed settings, but had two generator excitation levels for each speed setting.
Most Baldwins were built with an air throttle which was continuous in theory. A separate air line rather than jumper cables was required to operate in multiple. A maximum of four units could be operated in multiple with an air throttle since response time faded beyond the fourth unit. Needless to say, a Baldwin with an air throttle could not MU with anything with an electric throttle (just about everything else).
Railway Man Locomotives have to have a system to maintain speed of the engine regardless of load placed on the engine, a function which is provided by a governor. Automobiles do not need this system because they do not have an electrical transmission but have a mechanical transmission. EMD began by designing its locomotives with eight throttle steps plus idle. It could have chosen 10, 16, 7, 9, or 25, but chose eight because (1) that was a sufficient level of "fineness" to meet users needs for the rather narrow rpm range capability of the engine without subjecting the user to needless complexity that would drive up purchase price and maintenance price, and (2) it was convenient to use 8 because of the electromechanical technology of the day. The Woodward governor applied to an EMD engine used four solenoids to effect speed control. Each throttle setting energized a different combination of solenoids, as follows (for a 16-567C): Throttle Position Governor Speed RPM Solenoid Energized Governor Speed RPM Adjustment Stop Min Max A B C D Min Max Solenoid Sequence Idle 275 283 * 275 283 "C" 5 1 275 283 275 283 2 344 374 * 338 369 3 424 454 * 414 444 4 515 523 * * 500 508 "B" 4 5 584 614 * * * 564 594 6 675 683 * * * * 650 658 Fulcrum Nut 1 7 755 763 * * 725 733 "A" 3 8 835 843 * * * 800 808 "D" 2 Someone more versed in the byzantine workings of governors and electrical control systems can probably do a far better job of explaining how governor's work. Suffice it for me to say that "8" throttle notches is what we had at first and that became the convention. Today's locomotives with microprocessor controls could have a continuously variable throttle, and in effect the microprocessors govern the engine in that fashion anyway. But the 8 notches remain because it is convenient to operate in that fashion. Speed control on a locomotive has to be varied continuously anyway, in many operating conditions, in order to maintain the train as close as possible but not over the maximum authorized track speed. Thus removing the detents doesn't save any work but it does make operating memory and practice harder to replicate. RWM
EXCELLENT! I was just going through my GP9 operator's manual to find the info. As a note, earlier locomotives were less inclined to 8 notches, i.e., the old GE U25B's had 24 notches, if I am remembering it right. They also had a steam era "clutch" on the end of the throttle that had to be squeezed before the throttle could be moved.
4merroad4man EXCELLENT! I was just going through my GP9 operator's manual to find the info. As a note, earlier locomotives were less inclined to 8 notches, i.e., the old GE U25B's had 24 notches, if I am remembering it right. They also had a steam era "clutch" on the end of the throttle that had to be squeezed before the throttle could be moved.
I seem to remember some old GE U-boats that had 16 notches.
The C&NW E8 units had a throttle interlock which required the throttle lever be allowed to return slightly forward after each notch that it was advanced. This was to prevent the engineer from advancing the throttle too fast (thereby causing vast amounts of wheel slip). They also had a 'transition' lever. When C&NW created the "CrandalCab" units, they rebuilt the control stand and put in a regular EMD throttle (without the DB function or the transition lever).
As a further aside note, the early C&NW commuter cab-cars had an old-style EMD throttle assembly which included the 'transition' lever, in addition to the throttle and reverser.
I could just see a long train moving like I seen people drive.
They go 55 by going two minutes at 50 and two minutes at 60. Then as the decide to check the mirror. They drop to 45.
I rode on a tour bus in Germany. That bus was never at the same speed for 2 seconds.
I got off feeling like I had whip lash.
The GE's with 16 had what were know as "half notches". They'd get you engine speed without the load - an electrical trick designed to help the engr. manage turbo lag, if he cared to. Same basic set of 8 engines speeds.
The Baldwins with 22 had pneumatically controlled governors - heaven help them!
Question: Are other countrys using the 8 position throttles as well? This would include both exports from the US and foreign produced locos. Then we could go into EMUs (domestic and foreign) and other rolling stock. L&N historical society had an article about how the 27 point connector was set up including the 8 throttle positions.
I don't think that the Budd RDC's come into this discussion, since they are not diesel-electric, but have a mechanical linkage to the drive wheels. I know that they can be mu'ed with other RDC's, but I think it would be difficult to run one with a diesel-electric. I have ridden them in both single car and two car operation on the B&O (Washington-Baltimore) and VIA (Vacouver Island).
Johnny
Try a Google search for "locomotive" & "throttle" & "notches" - as separate words - and see what you come up with. I did one yesterday for that combination, plus "Fairbanks-Morse" as a phrase, and quickly found a detailed explanantion - about 3 - 4 printed pages equivalent, incl. about a half-dozen photos and diagrams (and way over my head, at least for the time I had available to peruse it) - of the Westinghouse throttles as used in Baldwin's and B-L-H's several post-war diesel electric systems on a page titled "Baldwin / Baldwin-Lima-Hamilton Control Stands" at :
http://www.geocities.com/wbd641/BLWcontrols.html
Good luck, and enjoy !
After reading all the replies it looks to me like is was an ingenious system that worked in the early days of deisel electric when the technology was new, and the reason we do it today is because "that's the way we have always done it".
Continuously variable does not require continuous adjustment or constant hands on. Modern fuel controls are very capable and sophistcated. It would be possible to set a speed and let the fuel control maintain it. Turbine powered aircraft have been doing it for decades.
Dave
Lackawanna Route of the Phoebe Snow
One thing not mentioned so far was that the EMD engine was very sensitive to torsional vibration (remember that the "blade" rod of the fork and blade pair was only held in place by the positive pressure on the piston).
The eight throttle notches and the associated engine rpm settings were carefully chosen to avoid "nodes" of high torsional vibration in the speed range of the 567 engine (and these were again checked for the 567C and 645E which ran at higher speeds).
This was outlined in Eugene Kettering's paper to the ASME on the development of the 201 and 567 series engines.
M636C
I understand what you are getting at.Instead of notch throttle positions. You would install push button throttling.Punch in the speed you want to go and the computer will maintain it.
It would be just like autopilot or cruse control.
I'm glad you guys posted abotu the 16-notch locos. I thought I remembered something about them. As for cruise control, that'd be awesome. Engineer can take a nap while the train drives itself. Eh, I'd be quite lucky to come upon a train that could someday let them do that. Maybe I've been watching Knight Rider too much lately...
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