Decoder with notching

[gregc]

Overmod

he notches determine control bands of engine rpm (in part to avoid running at critical speeds

help me out, now i'm curious.   a link would be great

i'm assuming "engine rpm" refers to the generator.   

notches configure solenoid switches resulting in different amounts of power  (i.e. same rpm generates different power depending on solenoid configuration).   for a given solenoid configuration, power varies with rpm.

i'm guessing some regulator circuit (govenor?) is adjusting fuel to achieve some desired rpm/hp.   reduce fuel if > target rpm and increase fuel < target rpm.

how correct are my guesses?

[Bayfield Transfer Railway]

richhotrain

 

 

gregc

joe fugate has described more prototypical operation of a loco/train w/ sound as "micro operations"

the ProtoThrottle is selling to the market interested in more micro operation 

 

 

 

Golf is calling, but when I get back home, I want to follow up on the Proto Throttle which interests me.

 

Rich

 

I had a chance to use a Proto Throttle.  If, like me, you like operations from the point of view of the person at the throttle, it's a barrel of fun.  It also slows things way down, which would be a great way to help keep road trains from burying the yard.

Pricey, but worth it.  I wish I could afford a dozen.

Hell, I wish I could afford one.

[Bayfield Transfer Railway]

yes, folks, he's not only the youngest lawyer in history, he knows more about computers than computer scientists, he knows more about diesels than professional engineers, he's a 150th degree Black Belt in the Secret Ancient Martial Arts, he found the Ark of the Covenant, he's Batman on weekends, he's been trained to kill with his bare hands by the Israeli Secret Service, and he's a Double-0 Spy with a License to Kill.

[Overmod]

gregc

my understanding is each notch corresponds to a specific HP.

Go back and read the Trains thread again.  The notches determine control bands of engine rpm (in part to avoid running at critical speeds, of which there may be many in a practical Diesel engine of this scale) and the governor then adjusts fuel feed to maintain speed in this range as load changes (and hence does the actual horsepower output regulation as measurable at the crankshaft or traction generator/alternator input.)  Further control of the actual horsepower through the motors, and much if not most of the slip, creep, and adhesion control giving wheel rim or 'dbhp' is done via the electrical system (PM Randy Stahl or Don Oltmann for precise details by prototype).

[gregc]

Lastspikemike

Bear in mind that the prototype has 8 steps covering only 400-500 rpm. Each notch raises the rpm limit by only 50 or so rpm.

my understanding is each notch corresponds to a specific HP.

   1     70.0   3 %
   2    150.0   7 %
   3    335.0  17 %
   4    595.0  30 %
   5    875.0  45 %
   6   1200.0  61 %
   7   1565.0  80 %
   8   1940.0 100 %

[speedybee]

OldEngineman

I ran the big engines for 32 years, freight and passenger.

The throttle handle on most diesels (at least in my time) was directly linked to engine speed, with each notch producing a certain RPM of the engine, and producing more power applied to the motors.

Thank you! This is exactly the information I needed to continue with my project. The conversation seems to have gotten carried away.

The proto throttle does not appear to be a reasonable solution because, as far as I can tell, it has no way of knowing how much load the locomotive is pulling, which varies based on grades, friction, weight of cars, etc. The solution must come from the decoder itself, probably by using the notch setting and drawbar pull to determine how speed should change.

[SeeYou190]

SeeYou190

PLEASE leave on-highway diesel engine controls and injection systems out of your under-informed statements. I know you are liking to think you are an expert on everything, but now you are dipping your toe into the pool of my true field of expertise. I do not want to be trolled or pulled into a conversation where I try to explain to you how you are wrong like others have been.

Lastspikemike

for the pedantic among

Oh well, as usual, Luke Skywalker says it best.

He who knows everything about everything obviously knows more than poor old "pedantic" me, who must simply know nothing about diesel engines or how those mysterious magical things actually work.

I will never mention anything about these mechanical confusing beasties again.

I'm tapping out.

-Kevin

[rrinker]

 You're missing one point. The governor range is tied to the throttle, it's not an independent device which only regulates the fuel rack based on load.

Quote from an operator manual for a real EMD loco (specifically in this case, a DD40X:

"The throttle electrically controls speed and power by actuating a governor mounted on the engine and by tying the response of the locomotive power control system to the throttle. The main generator converts the engine's mechanical power to electrical power, which is then distributed to the traction motors through circuits established by various switchgear components in the electrical cabinet. "

 Link to the whole manual: http://www.sbs4dcc.com/images/EMD-DD40X-Operating-Manual.pdf

Here's another, from an SW-8: "105 Throttle Lever This lever controls the speed of the engine and the train speed in normal operation. The SW8 and SW9 locomotives are basically equipped with the pneumatic-hydraulic governor control commonly termed the AIR THROTTLE. Speed of the engine is controlled by air pressure transmitted from the throttle control stand to the engine governor. The engine speed increases as the air pressure is increased, by opening the throttle, and is decreased as the pressure is reduced, by closing the throttle. When the throttle is opened, a cam actuated throttle switch is closed thereby enabling the main generator to produce power (assuming the generator field switch is IN and the reverse lever is in the forward or reverse position). The STOP position is obtained by depressing the button on the end of the throttle lever and pushing the lever one step beyond the idle position. When the throttle is in STOP, the contacts of the shut-down switch being closed, energize the shut-down solenoid in the governor; this stops the engine. In order to start the engine the throttle must be in the idle potition."

Link: http://www.chartertoconductor.com/wp-content/uploads/2019/06/sw8-om.pdf

There are a lot of operator manuals online - the older ones especially also cover how they work and in the case of the SW-8 manual, includes electrical schematics. Kind of like how automobile owner's manuals used to be, not only told you how to operate the controls, but how to repair it as well. Now they all just say "see your dealer"

                                       --Randy

 

[Overmod]

OldEngineman

he throttle handle on most diesels (at least in my time) was directly linked to engine speed, with each notch producing a certain RPM of the engine, and producing more power applied to the motors.

Keep in mind this is at least a two-step process: the notches regulate engine speed (via the governor) but the 'power applied to the motors' is also regulated separately via excitation, transition, steps of field weakening, etc.  We keep trying to tell our litigator this, but he keeps wanting it to be continuous and stepless like the railfan conception of a Baldwin throttle...  

I was recently reminded, in a discussion of Kettering's paper on the development of the EMD 567, that a large part of the determination of the rpm for each 'notch' rack setting was to avoid critical or resonant speeds in the engine, particularly the early harmonic balancers which as I recall used springs and tended to be fragile if provoked.

Union Pacific had the bright idea that, if fuel regulation is the only thing that controls motor rpm, they could rig an SD24 to run at constant speed, and just run the throttle in servo and do the fine adjust entirely electrically.  This, as they say, "failed to thrive" for a range of interesting reasons, some predicted about as well as the success of Arrowedge a few decades later.   

I recall some older GE freight engines (so long ago that I can't remember which ones) where the RPMs would increase in "2-notch intervals" at some throttle positions. They were odd ducks.

Actually, this for a while was a GE 'selling feature', the so-called 15-notch throttle.  The eight principal notches corresponded to the running notches of the standard MU control; the 'intermediate' or 'half' notches being used to load the engine more at its notched rpm.  This would have been a much more interesting idea had GE not been addressing turbo lag and some pollution concerns with glacial physical acceleration of the engine, and correspondingly slow loading it down electrically; a poster here familiar with the breed said it could take 80 seconds to load to Run 8 ... with a significant part of the loading taking place only in the last 20 seconds.  If you think that would lead to interesting road behavior, including when MUed to EMDs, imagine having to flat-switch with a locomotive having those characteristics...

[Bayfield Transfer Railway]

OldEngineman

"I do know just from standing beside moving locomotives that the 8 step throttle (which isn't technically a throttle just btw, diesels are not throttled)  does not correlate to engine rpm nor locomotive speed."

Huh....?

I ran the big engines for 32 years, freight and passenger.

The throttle handle on most diesels (at least in my time) was directly linked to engine speed, with each notch producing a certain RPM of the engine, and producing more power applied to the motors.

This was back in the days "before microprocessor-controlled engines", for the most part. Perhaps they do things differently now with engines that have a computer sitting between the engineman's hand and the big diesel under the hood. But I left the freight engines behind before the computers came in.

There were exceptions, just about all of them in passenger due to the HEP alternator which was attached to the driveshaft on F40's. They would run at full RPM even with the engine standing still. Moving the throttle on these increased traction power, but didn't change the RPMs. The Genesis engines work the same way.

I recall some older GE freight engines (so long ago that I can't remember which ones) where the RPMs would increase in "2-notch intervals" at some throttle positions. They were odd ducks.

But with most engines back then... take one more notch... the diesel would ramp up accordingly...

 

 

Hush, you and your "actual experience."  The World's Greatest Expert On Everything has spoken.

[OldEngineman]

"I do know just from standing beside moving locomotives that the 8 step throttle (which isn't technically a throttle just btw, diesels are not throttled)  does not correlate to engine rpm nor locomotive speed."

Huh....?

I ran the big engines for 32 years, freight and passenger.

The throttle handle on most diesels (at least in my time) was directly linked to engine speed, with each notch producing a certain RPM of the engine, and producing more power applied to the motors.

This was back in the days "before microprocessor-controlled engines", for the most part. Perhaps they do things differently now with engines that have a computer sitting between the engineman's hand and the big diesel under the hood. But I left the freight engines behind before the computers came in.

There were exceptions, just about all of them in passenger due to the HEP alternator which was attached to the driveshaft on F40's. They would run at full RPM even with the engine standing still. Moving the throttle on these increased traction power, but didn't change the RPMs. The Genesis engines work the same way.

I recall some older GE freight engines (so long ago that I can't remember which ones) where the RPMs would increase in "2-notch intervals" at some throttle positions. They were odd ducks.

But with most engines back then... take one more notch... the diesel would ramp up accordingly...

[Bayfield Transfer Railway]

Of course, ultimately we reach the point where we need to ask "Do I want a control system that's so realistic that only a trained locomotive engineer can use it?"

There is such a thing as too much realism.

 

[Overmod]

Lastspikemike

Now I don't know how modern diesel electric locomotives control torque output...

It is probably worth learning about.  Most modern engines now use EFI (electronically controlled and modulated fuel injection) and what used to be called FADEC (full-authority digital engine control) and the details are easily as sophisticated as those of automotive drivetrains; they also 'phone home' if they start to have problems.  If you listen to one of these engines in DP you can hear finer engine control than in eight-notch compatibility for MU.  (Control over the electric transmission is a whole 'nother world, that gets fascinating in places like creep control and wheelslip detection and avoidance, but these are not really related directly to diesel-engine speed or power control beyond circumstantial.  And the world changes again, dramatically, with the use of synthesized AC drive, which opens up great possibilities for proportional engine control outside MU standard compatibility)

I do know just from standing beside moving locomotives that the 8 step throttle (which isn't technically a throttle just btw, diesels are not throttled)  does not correlate to engine rpm nor locomotive speed.

The problem is that idle tells you nothing about how the engine governor controls power in the eight-notch system.  In the great number of locomotives with Woodward governors the 'power' notches correspond to mechanical 'fuel rack settings' which control the amount of fuel burned in each stroke (which is the way an injected engine with no combustion-air throttling varies power) but the actual governing feature of the Woodward governor adjusts the engine to set speeds (also by regulating the amount of fuel injected; diesel power output is determined by efficient fuel burn per power stroke but a surprisingly high percentage of the actual expansion power is used just in turning a compression-ignition engine at constant speed -- more, if trying to accelerate the engine into a load.)  There are very good tutorials on the Web regarding the Woodward governor and how it functions; there are also good illustrations on the eight notches, the corresponding engine-speed tables, and the interesting reasons there are 'eight' notches in the system and not the 15 that GE tried to produce as a 'feature' or one of the stepless-control systems like Alco or Baldwin air throttles.

The electric transmission in these locomotives is infinitely flexible which is why it is used.

Unfortunately, there is a very long and sometimes fascinatingly involved history behind the things needed to regulate the 'infinitely variable' electric drive to suit it to the decidedly not as variable economical power output of many types of internal combustion engine.  You can start with something like modified Ward-Leonard and then work your way up to see how the approach evolves with respect to different types of combustion engine.

Hydraulic transmissions have been used, pump and motors correlating exactiy to their electric versions but not as durable, flexible or ultimately efficient as the electric versions.

More unwitting ignorance here.  Only very small or very unsuccessful locomotives use hydrostatic drive, and no more than a moment's reflection will suggest some of the reasons to you.  All the large diesel-hydraulics use some version of hydrokinetic drive (a thing German companies brought to high sophistication for high power transmission); a good example is the Krauss-Maffei 'America-Loks' being discussed in the Rivarossi thread, which produced 4000hp in a single-unit locomotive (using high-speed diesel engines,  not as practical with the added weight and cumulative losses of a typical diesel-electric transmission).  Final drive in these is mechanical, using universal-jointed 'Cardan' shafts or the equivalent, more or less just as a car with an automatic torque-converter transmission does.  There are very good descriptions of these things from Voith alone that will explain them for you, but unless you think about railroad-specific control and maintenance issues you may be unaware why these ultimately 'failed to thrive' in US practice, with the notable exception of flexibly accelerating RDCs.

All the electrics are just an infinitely-variable-ratio transmission, by definition a stepless transmission like a CVT now in automotive use

In fact other aspects than 'stepless control' factor in, such as the ability to implement reverse braking without friction heating or tread wear, and avoidance of electrical overload or damage (see for example the various DC-traction-motor limits, for example low-speed hourly and instantaneous limits up to around 10-12mph or birdsnesting concerns above an armature rpm determined in part by gear ratio.

None of this is particularly arcane,and the 'why and wherefore' is not difficult to acquire, but you have to learn it 'as it is' and not pretend it's the way you want it to be from assumptions.

[SeeYou190]

Lastspikemike

That 8 step throttle control on the prototype locomotive is not as simple as the fuel injection controller on a truck Diesel engine, although now even automotive diesels use quite complex software to deliver the desired torque characteristics.

Please, please, please...

You have made a lot of bad comparrisons lately about DCC, and the DCC people have tried to correct you.

PLEASE leave on-highway diesel engine controls and injection systems out of your under-informed statements. I know you are liking to think you are an expert on everything, but now you are dipping your toe into the pool of my true field of expertise. I do not want to be trolled or pulled into a conversation where I try to explain to you how you are wrong like others have been.

Thank you.

-Kevin

[SeeYou190]

rrinker

 Hence the Proto Throttle. Even if it were half the price, I can't see most people replacing all their unrealistic knob throttles with them. But as seen in numerous videos of them in use, for the people that do enjoy it, the Proto Throttle gives them that realistic feel.

I have said before... if I had to start all over I would have a G scale ISL shelf layout with one GP-9 and a proto throttle.

That would feel like railroading.

-Kevin

[rrinker]

 Hence the Proto Throttle. Even if it were half the price, I can't see most people replacing all their unrealistic knob throttles with them. But as seen in numerous videos of them in use, for the people that do enjoy it, the Proto Throttle gives them that realistic feel.

 Now they just have to make one modeled after an Alco control stand - running an RS3 with an EMD control stand just feels wrong. 

(no, no pictures of those abominations of Alcos converted to EMD prime movers)

                                           --Randy

 

[gregc]

richhotrain

but you can't replicate.

why not?    but i doubt modelers would want that, taking 10 mins to get up to speed.   so you scale the mass computation

i've worked on code to determine the speed of a train based on the tonnage, HP, bearing friction and grade.   not perfect, close enough.   does a train stall/slip going up a grade?  does it start rolling backwards?

it appears there are modelers interested in more accuarate behavior of a train.   trains that more realistically accelerate (not constant), are limited in speed due to HP/tonnage/grade, slow down or accelerate on grades and require use of brakes to maintain (down a grade), slow and stop a train.

and they want sound that matches the situation.   brake squeals, lots of noise accelerating a lot of tonnage and less noise when pulling no cars.

[richhotrain]

gregc

joe fugate has described more prototypical operation of a loco/train w/ sound as "micro operations"

the ProtoThrottle is selling to the market interested in more micro operation 

Golf is calling, but when I get back home, I want to follow up on the Proto Throttle which interests me.

Rich

[richhotrain]

gregc

 

richhotrain

How can you scale down a real locomotive to perform like it does on the prototype to any of the scales used in model railroading? 

don't understand why you think controlling the speed like a real loco is that hard?   it's just math

of course you don't want a model pulling 100 cars to take as long as a real locomotive, but you can cheat a little so that it accelerates faster.

Exactly. And that's my point, greg. You have to "cheat", or more politely stated, you have to "improvise" a little...or a lot. You can simulate, but you can't replicate.

Rich

[gregc]

richhotrain

How can you scale down a real locomotive to perform like it does on the prototype to any of the scales used in model railroading?

don't understand why you think controlling the speed like a real loco is that hard?   it's just math

of course you don't want a model pulling 100 cars to take as long as a real locomotive, but you can cheat a little so that it accelerates faster.

i think there are at least 3 things to understand for more realistic control

1. you need to be able input the tonnage (# cars)
2. the "knob" controls the acceleration calculated from the tonnage and an estimate of engine force (tractive effort)
3. brake control is needed slow/stop because the "knob" can't slow the train down

joe fugate has described more prototypical operation of a loco/train w/ sound as "micro operations"

the ProtoThrottle is selling to the market interested in more micro operation

[richhotrain]

How can you scale down a real locomotive to perform like it does on the prototype to any of the scales used in model railroading? You can't. So, why are we trying so hard to do it?

Rich

[gregc]

SeeYou190

I do not think an 8 step throttle would work in the model world.

why not if you have a tonnage input such as the ProtoThrottle has (unused) and use the control to determine the drawbar force (HP) and not simply as a speed setting.   acceleration is proportional to the mass (tonnage) / drawbar force.

the loco would accelerate much differently w/o any car vs 5 cars

i'm curious if each notch is a proportional amount of horsepower: 12, 24, ... 88, 100%?   how much horsepower do you want in notch 1 if you're just moving the loco?

my understanding is that prototype engineers are switching between two notches to maintain a relatively constant speed.    wouldn't modelers interested in prototypical operation like that?  select a notch to accelerate the train up to speed, possibly reduce it to zero and coast, then use the brake to slow and finally stop.

[SeeYou190]

I do not think an 8 step throttle would work in the model world.

Just as an example: A GP-9 will act much differently in notch 2 with one empty hopper car than it will in notch 2 with six loaded boxcars and a caboose.

There is just no reasonable way to simulate all the real world effect of hundreds of tons in miniature.

-Kevin

[Overmod]

Lastspikemike

We speak at cross purposes.

Actually, no, I was intentionally restricting my remarks to 'model' in the sense of 'smaller-scale physical replica with prototypical operating characteristics as well as appearance.'

Architectural models serve the same purpose as design models or stylists' clays: they are a part of a good design process, not an end result to show off craftsmanship or 'wow' clients.  Architecture crits often contained  the dread words "there was no model" (meaning that designs that looked fine in the side and end elevations or in the axons just Did Not Compute in as-built 3D).  
The same applies in spades to many automobile designs and details... and yes, this includes steam and other locomotive streamlining.  But very seldom do we find this in actual model railroading...

The word "model" has several denotations and even more connotations.

To see the changes rung on this you need to look at the organized T1 Trust design effort.  Even the feasibility plan required design, multiphysics, and simulation modeling; there are now at least four separate versions of the design in 'train simulator' environments alone, and extensive modeling of control and sensing systems, including the necessary instrumented wheel sets to run in the Fast Loop, is done.  In fact it would be hard to think of a sense in which 'model' doesn't apply to 5550 ... except that it is not a demonstrator apartment for rentals or new purchases.  At least, not yet...

I confess I like to hear your opinion on the invaluability of railways.  There's a poster with the handle 'ttrraaffiicc' who occasionally posts over on the Trains Magazine forum; I'm sorely tempted to sic you on him.  Read some of his posts and you'll see why...

[Overmod]

Lastspikemike

So, yes, I bought a used Mantua 2-6-6-2 logger that is deliberately made to be out of scale and really doesn't run that well, never did even from new apparently. I had at that time no power nor track to run it on. If you understand why I would do such a crazy thing then each of your questions will be answered.

Actually, there's nothing crazy about it: all the illustrative questions that involve the hobby are yet to be asked:

Do you use it for display or operation?  Do you build a module or layout around it ... or fit it in to something else?  Do you rebuild it for better scale, or superdetail it, or weather it with care and skill?  Do you rebuild the drivetrain for smoothness, or remotor for 'moar power'?

And all the other things about structures to go with it, tracklaying connected with it, follow-on purchases or products ... and, above all, the joys (and other emotions) that go along with it.  (We already agree it's been stipulated to be an 'obsession')

The potential fun in this specific context is whether you want to model how a steam engine 'drives' or not.  If you think eight-notch plus physics is counterintuitive (as is three-notch DC MU electric control to an even worse extent, btw) there is a voyage of discovery just raising anchor: throttle, reverse, drifting methods, use of wire drawing for slip control... all of which can be 'emulated' in a device gear-driven by a variable-speed electric motor but only with great effort and care...

[gregc]

Lastspikemike

My opinions on this subject are influenced by my perception of what this hobby is about.

what's being modeled?

• locomotives
• trains
• structures
• scenery
• railroad
• railroad operation
• one or more of above
• ???

if locomotive, is it mechanism or behavior?

[rrinker]

 That's just simulated in the sound decoder though, those locos have a typical electric motor and gears driveline. I don't think the 3rd rail pickups on the Rapido models even actually work. 

                             --Randy

[gmpullman]

rrinker

Well, there are the Kato P42's with axle mounted coreless motors in HO, simulating traction motors.

Plus the Rapido ex-New Haven FL9s where the prime mover is shut down and the traction motors are powered off the DC third rail. About as close to model railroad simulation you can get.

IMG_6820_fix by Edmund, on Flickr

Cheers, Ed

[rrinker]

 Well, there are the Kato P42's with axle mounted coreless motors in HO, simulating traction motors.

 But no internal cumbustion prime mover turning a generator inside.

Hornby did live steam in HO, but it's not exactly practical when you get down to that size. The most common diesels in larger ride-on scales seem to be gas-hydraulic, mainly because appropriate hydraulic pumps and motors are pretty easy to source. Ones that size with electric motors tend to be battery powered, no engine of any sort.

                                              --Randy

 

[Overmod]

Lastspikemike

For a model railroad model it makes no sense to model the prototype diesel electric drivetrain.  It can be modelled much more easily by mere representation.

In case you are wondering, that is what I got done saying when you tried making that point a different way.

The discussion is about the other 'half' of the "representation" which is allowing model controls to be made and manipulated in 'prototypical' ways that produce the 'prototypical' simulated behavior in the model.

As noted, not all modelers will find this attractive, or interesting, or necessary for anyone to do ... all that is in previous comments.  On the other hand if you were building a training simulator for real railroaders, this would provide it... or any more 'forgiving' adaptation for early training or just 'more prototypical' fun.