Mention was made of the electric locomotive heritage of diesel electrics, and I should point out that streetcars, up to the PCC, had controls with eight or ten notches, the old K-type controller. Also, the earliest EMS diesels had manual transition from series to parallel and for field shunting, but starting with the F-3, transition was made speed dependent (approximately) on the basis of the voltage across the armature commutator, and automatic. Resistors are still employed for field shunting of dc motors, but not in the main power leads, and field shunting does not waste much power. All this has been replaced with electronics and very precise control of voltage and current to both field and comutator in ac-generator current production locomotives, even with dc motors. (AC motors do not need comutators.) Continuously variable control would be a lot simpler now, but still is not needed.
M636C 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
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
That's the problem with the Woodward governor. You can only set the speed for 4 notches independently. The rest just are a result. Sometimes, you can wind up with a speed schedule that's "lumpy".
An electronic governor has the advantage of being able to set each notch's load and speed independently. This is particularly attractive on a roots blown EMD where you could get somewhat better fuel efficiency in the lower and middle notches.
-Don (Random stuff, mostly about trains - what else? http://blerfblog.blogspot.com/)
THE.RRDon't forget that the original "Diesels" were really straight electrics with a gen set added. The electric controled speed by sending the 600V (or more) DC thru a set of resistors. Each notch on the controller sent the voltage thru a different combination of resistors till full voltage was applied for full speed. A lot easier for GE or Westinghouse to supply the same controller to the first Diesels.
Don't forget that the original "Diesels" were really straight electrics with a gen set added. The electric controled speed by sending the 600V (or more) DC thru a set of resistors. Each notch on the controller sent the voltage thru a different combination of resistors till full voltage was applied for full speed. A lot easier for GE or Westinghouse to supply the same controller to the first Diesels.
While there may have been a few diesels with "straight electric" control systems built, most of the diesel-electrics in the US used the control system developed by Lemp for GE. By using a combination of a battery winding, shunt winding and differential winding, he was able to get the generator to operate in a more-or-less constant power mode. The transitions from full series to series parallel to full parallel was to overcome the voltage and current limits for the generator. In the high horsepower extreme for generators (e.g. GP-35), field shunting became necessary to keep the voltage and current within limits.
The big problem with using resistors is that they waste energy, and they were not needed with the Lemp control.
I remember SW1s having no "notches"
Big Jim .. you are old .
I understand that streetcars have infinite throttles , they also have low current draw, I wonder how long a grid resistor would last at 6500 amps? I know that electric frieght locomotives have a large amount of grid resistors , I also know that using them too much spells disaster, they always have assorted blowers to try to cool them along with open cicuit protection but if you blow one the destruction is going to be major !
Imagine how many wires would be in an MU jumper if there were more than 8 notches ! Aren't they heavy enough ? And in cold weather they are not easy to work with with 27 wires !!
Yes the old GE's had half notches but they also had throttle relays that would stay picked up through the half notches to give a true 1-8 notch reference via the MU, AVR= A valve relay , BVR= B valve relay , etc.
I think the original designer of the 8 throttle notch system was missing two fingers
I remember from a past issue of TRAINS that the main reason for eight notches is that is all the electronic capacity that was available in the early years of diesel locomotive development. The Technology is now available to have unlimited number of notches, like a car, but since eight still work fine, the change was never made.
THE.RR . Each notch on the controller sent the voltage thru a different combination of resistors till full voltage was applied for full speed.
. Each notch on the controller sent the voltage thru a different combination of resistors till full voltage was applied for full speed.
Now THAT explanation I understand.
Dave
Lackawanna Route of the Phoebe Snow
That would be a conductor's dream come true! Imagine, not having to go outside on a freezing night in a snowstorm to switch cars! Assuming the switches can be thrown automagically by then, too...I don't think railroads would have any shortage of employees then!
Why have notches, and not a continuous throttle???
The PCC streetcars were designed with an almost infinate controller, but by then convention was settling on the diesels, and backwards compatibility was needed.
Phil
Timber Head Eastern Railroad "THE Railroad Through the Sierras"
I really see no problem with autopilot.
Pilots take advantage of it.
They set and take long naps.
Aircraft can land them selfs now.
If they install remote coupler. The computer would be able to drop off and pick up sets of cars. Do all the tests and be on its way.
Yeah, I jokingly wrote that line. Besides, today's lawyers would never allow it even if it was safe to do someday.
kolechovskiEngineer can take a nap while the train drives itself.
Engineer can take a nap while the train drives itself.
That theory has been disproved already. See this accident brief.
Technology might be able to overcome that once detailed train movement mechanics are programmed in to deal with slack action and other stresses, especially with the ECP trains we've been having out here, I'd think that kind of thing could be expanded. What all does ECP offer as benefits anyhow? All I know is it pisses off the crews that have to lug them in and work with them, LOL! It's been a number of times their train has been getting stuck with their lead unit dying on that thing. Anyhow, could wheel-grip detection be included?
(remember that the "blade" rod of the fork and blade pair was only held in place by the positive pressure on the piston).
Sorry, but that is not the way I remember them at all. The way you explain it, it sounds like the rod is only floating around in air. Seems to me that the fork rod held the blade rod in place.
And yes, I am old enough to remember those "half notches" on the Alcos & GE's
.
Cruise control sounds like a good idea, and it is, in my pickup, especially for long trips. I'm sure it would be very helpful over flat terrain in cases where no notch is really right for maintaining the desired speed.
I suspect that the biggest issue with it on trains would be management of slack action. Having the locomotive(s) maintain a constant speed doesn't take into account the dynamics involved in the rest of that mile-long train over varying terrain.
Perhaps one of our experienced engineers can speak to the concept.
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...
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...
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.
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.
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 !
- Paul North.
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
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.
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!
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.
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.
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.
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
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
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).
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.
IIRC, the old GE's only had 8 engine speed settings, but had two generator excitation levels for each speed setting.
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.
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
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.
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