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Linn Westcott and realistic control.

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Posted by trainnut1250 on Friday, February 15, 2013 12:09 PM

Rick Mugele

Also, when using the F7 brake, can the throttle be increased increase the stopping distance?

No,, increasing the throttle after the brake is applied has no effect.  In regards to the simulator that Jack Burgess built that you mentioned and your other thread about blunt brakes and throttles, you might contact Jack directly through his website:

http://www.yosemitevalleyrr.com/

I have seen Jack's simulator (pretty nifty) but i believe that it is not currently in use on his NCE DCC controlled layout.

Guy

 

 

see stuff at: the Willoughby Line Site

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Posted by Rick Mugele on Thursday, February 14, 2013 8:56 PM

Randy,

Thanks for the update.  In digging through the archive, I found the October 1975 RMC with the Jack Burgess quarter-size cab control feature.  Jack used the TAT IV with Blunt brake circuits.  In the same issue was the second part of the Don Fehmann SST/7 which featured train and independent brakes.  I suppose either of these cabs could be plugged into the Zephyr jump port?

Thanks again,

Rick

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Posted by rrinker on Thursday, February 14, 2013 5:37 PM

 The Zephyr jump port simply takes the output of a DC throttle and uses it as the throttle control for a DCC address assigned to it. So the functioning would be whatever functioning offered by the DC throttle connected. It simply monitors the voltage developed across the output, same as a DC loco running on the track would, and it translates that into a DCC speed step. So if the effect of the throttle would be to increase the output voltage if the throttle lever was opened while the brake was applied, then yes, the loco would speed up. At a given throttle position and brake handle position, the voltage will be decreasing, so the loco will slow down. If the brake is increased, it will drop faster, if the brake is reduced, it will drop slower or if the throttle position is such that it would overcome the brake, the voltage would go up, so the loco would speed up.

                 --Randy

 


Modeling the Reading Railroad in the 1950's

 

Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.

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Posted by Rick Mugele on Thursday, February 14, 2013 1:48 PM

Guy, Randy,

Randy mentioned connecting the Blunt brake throttle to the Zephyr "jump port".  How does this work?

Also, when using the F7 brake, can the throttle be increased increase the stopping distance?

Thanks,

Rick

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Posted by trainnut1250 on Thursday, February 14, 2013 1:20 PM

Rick,

If I understand you correctly, Yes I have done this many times...The brake set up is included my standard configuration for Tsunami equipped locos on my layout..  I have set up around 10 locos with the brake.  I use the Easy DCC system, I use the settings in the Tsunami CVs to acheive the effect that Randy and I referred to earlier.  I'm sure this will work on any DCC system..

When i set up the decoder I usually re-map the functions so that F7 is the brake.This is explained in detail on page 24 of the Tsunami manual. The default brake is F11.

Specific brake instructions are on page 61 in the manual.  You have to set CV 3 and 4 to a value of at least 20  (CV 3 is acceleration rate , CV 4 is braking rate).

You then set the degree of braking desired using CV 61 and that's it. 

 When coming down grade I will apply the brake by pressing F7 and the train slows down with out touching the throttle setting, when released, the train speeds up to the original throttle setting (hence the acceleration setting CV 3).  Only downside is if a loco at rest has the brake turned on, there can be a moment of "why doesn't my train respond to the throttle"...You have to release the brake to move.  The brake setting is a fixed amount of braking, there is no way to vary the intensity of the brake without resetting the CV. Not perfect but still pretty cool effect.

 

Hope this is helpful,

 

Guy

see stuff at: the Willoughby Line Site

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Posted by Rick Mugele on Thursday, February 14, 2013 12:16 PM

Guy, Randy,

Have you actually done this with the Digitrax Zephyer, Blunt brake circuit, and Tsunami?  If so, can you provide details?

Thanks,

Rick

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Posted by rrinker on Thursday, February 14, 2013 7:30 AM

 The layout was a Timonium, but I wasn't. I usually go to that show, but I was unsure of when my GF's surgery was going ot be and wasn;t able to prepare with a room and so forth.

  I guess it does take getting used to, but I quickly developed the method of using my DT400 throttle held down at my side, never looking at it after selecting a loco. I can hold it on one hand, roll the throttle encoder with a thumb, and click it to reverse, leaving my other hand free to uncouple cars and operate ground throws when switching.

 I hate to think how big they'd have to make the thing if the buttons were all different sizes and shapes - and going back to fewer buttons with multiple multiple shift and escape functions to access all the features would be equally or even more complex, trying to remember all the combinations. I would like to see a different intermediate throttle, somehwere between the UT4 and DT402, single encoder, 0-10 keypad, select loco button, and I suppose 2 shift buttons, one for F10-F19 and one for F20-29 (which I don't ever use since all the high functions ever seem to be used for on sound decoders are cattle car and city sounds, which I don;t want coming out of my locos, but if access was not given to the full 29 functions, people would complain, since MRC's giant hyperbole machine has made it 'absolutely critical'). There are some DIY Loconet compatible options that are close to this already. A display to see what number you keyed in is kind of important, too.

       --Randy

 


Modeling the Reading Railroad in the 1950's

 

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Posted by rrebell on Wednesday, February 13, 2013 9:42 PM

The only problem I have with the train engineer is sometimes I hit the stop button by mistake, smaller button would have suited me just fine.

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Posted by ATLANTIC CENTRAL on Wednesday, February 13, 2013 8:23 PM

CSX Robert

ATLANTIC CENTRAL

My only problem with encoder wheels is more of a sense of needing a display, to know how much I have changed it. As implemented by Digitrax, the knob is uncomfortably small and the display hard to read. Maybe too, the Train Engineer has the "option" of the "emergency" button if you feel you need to stop in hurry, the encoder wheel lacks that option.

Additionally, the push button approach is much easier to operate with one hand and no eyes on the throttle...

With Digitrax's encoder equipped throttles, you can also increase and decrease speed with pushbuttons, which is what I do when switching(with one hand and without looking at the throttle), and they also have an emergency stop button.

But the problem is there are TOO many buttons (32 if I recall) and they are TOO small for my chubby fingers.

My Aristo Train Engineer throttles have five BIG buttons that are easily identified by feel alone -

FASTER - a bar at the top

SLOWER - a bar below "FASTER"

EAST and WEST - side by side

EMERGENCY - a bar at the the bottom

All easily pressed with my thumb as I hold the throttle in one hand.

I use Digitrax throttles all time at a number friends layouts, I have yet to really get use to them after a number years of operating sessions in our Round Robin.

If i must use a Digitrax throttle, I prefer the UT4R, it is the least objectionable of the bunch.

Sheldon

    

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Posted by CSX Robert on Wednesday, February 13, 2013 8:10 PM

ATLANTIC CENTRAL

My only problem with encoder wheels is more of a sense of needing a display, to know how much I have changed it. As implemented by Digitrax, the knob is uncomfortably small and the display hard to read. Maybe too, the Train Engineer has the "option" of the "emergency" button if you feel you need to stop in hurry, the encoder wheel lacks that option.

Additionally, the push button approach is much easier to operate with one hand and no eyes on the throttle...

With Digitrax's encoder equipped throttles, you can also increase and decrease speed with pushbuttons, which is what I do when switching(with one hand and without looking at the throttle), and they also have an emergency stop button.

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Posted by ATLANTIC CENTRAL on Wednesday, February 13, 2013 7:33 PM

rrinker

 That's exactly why I prefer the encoder throttles over the potentiometer ones. Since it can take several truns to go from stop to full speed, I can very easily accelerate and decelerate in a prototypical fashion, no jackrabiits, no slamming on the brakes. And I don;t have to fiddle with the decoder settings. I do typically put a little momentum in my locos - basically the least common denominator, mainly, light loco moves. If I would just crank open the throttle with a train, it would be too fast to be realistic. But since th encoder makes tiny little steps, I can run up to speed very slowly, simulating the load of that train.

 It also comes in handy with sound - though I know this doesn't appeal to you, with many sound decoders, the momentum controls the 'loading' effect on the prime mover. There, it needs more momentum programmed in, simulating the heavy load, which you can bypass by slowly opening the throttle. For a heavy train - crank open the throttle, prime mover loads up, loco begins just creeping. You can throttle back to reduce the prime mover, or else if the throttle is at the speed you want anyway, as the loco reaches that speed, the prime mover will settle down. All pretty neat and effective as long as you don;t have the thing cranked up to toy train sound volumes.

 Consider making that Strasburg trip around the July 4th week - I'll be there with the RCT&HS big modular layout in the museum.

           --Randy

 

There is no question that the encoder wheel and the push button are similar in that regard.

On the Train Engineer, even if you press and hold the excel or decel button, there is a fixed rate of change that is not instant.

My only problem with encoder wheels is more of a sense of needing a display, to know how much I have changed it. As implemented by Digitrax, the knob is uncomfortably small and the display hard to read. Maybe too, the Train Engineer has the "option" of the "emergency" button if you feel you need to stop in hurry, the encoder wheel lacks that option.

Additionally, the push button approach is much easier to operate with one hand and no eyes on the throttle.

But basically I agree, a little momentum is a good thing in a throttle system, and properly used provide most of the "effects" the OP seems to be looking for - at least in my view.

Were you at Timonium on the 2nd - 3rd?

I was going to look for you and introduce myself but I had the grand kids and was "busy" just keeping up with them.

Strasburg is less than one hour from here, we go there quite a bit, may that weekend will be available.

Sheldon

    

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Posted by rrebell on Wednesday, February 13, 2013 2:52 PM

I would like to comment on the fact that with the proper flywheels on a diesel, mine don't stop on a dime, even at emergency off.

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Posted by trainnut1250 on Wednesday, February 13, 2013 1:28 PM

rrinker

. The EFFECT of it was that as you apply the brake, the loco slows but not as fast as it would if the throttle was closed first, and if you let off the brake, the loco will speed back up.

     --Randy

  

 

This is exactly how the Tsunami brake works.  Neat effect.

 

Guy

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Posted by rrinker on Wednesday, February 13, 2013 12:26 PM

 Very true - it IS that simple. You can connect Blunt's throttle to the jump port on a  Zephyr/Zephyr Xtra. Just turn off the pulse. The loco controlled by that throttle will behave just as a DC loco controlled by that throttle, assuming momentum effects are nto enabled in the decoder. Although some of the interactions might be useful - particularly on braking, hit the air, train doesn't slow down right away because the decoder has momemtum enabled.

            --Randy

 


Modeling the Reading Railroad in the 1950's

 

Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.

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Posted by CSX Robert on Wednesday, February 13, 2013 12:13 PM

The throttle circuits used to simulate a real train should be easy to implement on a Digitrax system as long as the circuit does not rely on reading the motor's bemf and as long as the circuits output is smooth(actually even a pulsed output would be usable if fed through a resistor capacitor filter).  Just feed the circuit's output into a Zephyr's jump port.

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Posted by rrinker on Wednesday, February 13, 2013 12:11 PM

 That's exactly why I prefer the encoder throttles over the potentiometer ones. Since it can take several truns to go from stop to full speed, I can very easily accelerate and decelerate in a prototypical fashion, no jackrabiits, no slamming on the brakes. And I don;t have to fiddle with the decoder settings. I do typically put a little momentum in my locos - basically the least common denominator, mainly, light loco moves. If I would just crank open the throttle with a train, it would be too fast to be realistic. But since th encoder makes tiny little steps, I can run up to speed very slowly, simulating the load of that train.

 It also comes in handy with sound - though I know this doesn't appeal to you, with many sound decoders, the momentum controls the 'loading' effect on the prime mover. There, it needs more momentum programmed in, simulating the heavy load, which you can bypass by slowly opening the throttle. For a heavy train - crank open the throttle, prime mover loads up, loco begins just creeping. You can throttle back to reduce the prime mover, or else if the throttle is at the speed you want anyway, as the loco reaches that speed, the prime mover will settle down. All pretty neat and effective as long as you don;t have the thing cranked up to toy train sound volumes.

 Consider making that Strasburg trip around the July 4th week - I'll be there with the RCT&HS big modular layout in the museum.

           --Randy

 


Modeling the Reading Railroad in the 1950's

 

Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.

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Posted by rrebell on Wednesday, February 13, 2013 10:11 AM

Thanks Sheldon!!!!!!!!!! I was wondering as I have a large (15x30) and a single large dogbone with a yard at both ends, max 3 operators. Main is the Train Engineer and one yard (very small with a carfloat interchange) is a standard MRC 2500 with the other main yard being a handheld control linked to a 2500 as it is a much bigger yard.

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Posted by ATLANTIC CENTRAL on Wednesday, February 13, 2013 7:32 AM

rrinker

 The thing is, none of that matters. It's all a simulation anyway, You're getting too caught up in the details of how Blunt's design worked. The EFFECT of it was that as you apply the brake, the loco slows but not as fast as it would if the throttle was closed first, and if you let off the brake, the loco will speed back up. This might be easier to accomplish with a potentiometer throttle, but I'm confident it could be done digitally as well - the throttle and brake in Train Simulator work prototypically, even down to independent and dynamics. True actual train braking will never work in small scales - the physics doesn;t scale - so it's always a simulation.

     --Randy

Agreed!

And so, I suggest that it is infinitely more practical, in our selectively compressed little worlds, to simply learn how to slow or speed up the train in a manner that reasonably reflects how it would appear to the casual viewer.

I find the Aristo Train Engineer very good at this, better than most DCC setups. Without any programing or other "fiddling", most locos respond in a very smooth and prototypical manner. The ramp up and ramp down times built into the TE provide the perfect amount of delay to simulate throttle and brake actions while still allowing precise control for switching.

We are not in the cab, we don't have "seat of the pants" feel or onboard instruments to go by - we are observers - even as we a are miniature operators.

But that is just my view, if I wanted that real life experience, I would drive up to Strasburg and apply for a job.

Disclaimer - my modeling goals are more focused on running a "railroad", not just one locomotive.

Rick, ideas like your battery powered Challenger are interesting, but at the end of the day I need and want to operate everything from a GE 44 Tonner to a C&O H8 on the same system. And I need to MU 3 to 6 unit diesel sets without a lot of complex actions. And many of my operators have no real knowledge of actual locomotive operation. 

Sheldon

    

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Posted by rrinker on Wednesday, February 13, 2013 7:01 AM

 The thing is, none of that matters. It's all a simulation anyway, You're getting too caught up in the details of how Blunt's design worked. The EFFECT of it was that as you apply the brake, the loco slows but not as fast as it would if the throttle was closed first, and if you let off the brake, the loco will speed back up. This might be easier to accomplish with a potentiometer throttle, but I'm confident it could be done digitally as well - the throttle and brake in Train Simulator work prototypically, even down to independent and dynamics. True actual train braking will never work in small scales - the physics doesn;t scale - so it's always a simulation.

     --Randy

  


Modeling the Reading Railroad in the 1950's

 

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Posted by ATLANTIC CENTRAL on Wednesday, February 13, 2013 6:05 AM

rrebell

Sheldon, how big a layout do you have ??????????? It must be huge to need that many channels.

My layout room is a dedicated 22' x 40' heated and cooled space above my detached garage.

When complete the layout will fill the room and consist of a double track mainline on two levels about 8 scale miles long, or about a 500' actual run.

The mainline will support the operation of four to six trains. There is a separate passenger terminal, engine terminal, main yard and industrial belt line area that will support the operation of three operators, two working the yards, one on the industrial belt line.

Additionally there will be a single track "branch-line" representing a separate railroad that interchanges with the ATLANTIC CENTRAL and that line will require one throttle.

Hidden staging will be provided for about 30 trains, typically 35-40 cars in length.

Full operation will require a crew consisting of eight engineers, two dispatchers, yard master and several conductors for local switching.

The layout is also set up in such a way that four mainline trains can be on "display loops" if desired and this will still allow for separate operation of the other areas, yards, passenger terminal, etc.

While big, I would not call it "huge", I know a number of modelers with layouts larger and/or more complex than mine.

I consider my layout large, but relatively simple, designed for long trains and realistic operation while still maintaining good display operation for non railroaders.

Sheldon

    

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Posted by Rick Mugele on Wednesday, February 13, 2013 1:41 AM

Greg,

Actually, the rehostat of the most basic throttle does not control voltage but power expressed as watts (volts times amps).  Input would be the basic 12 volts modified by rehostat resistance.  Some folks used Variac transformers to control voltage output to maintain constant speed.  Amperage draw would vary according to load changes but voltage would remain constant.  On a 1:1 locomotive it is actually possible to watch amperage drop and voltage climb as the train accelerates given a constant power setting.  Probably see this with a model locomotive and a basic power pack and meters.

Now we just need to figure how to send the proper signals for a DCC decoder to interpret as power and brake applications. 

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Posted by rrebell on Tuesday, February 12, 2013 11:27 PM

Sheldon, how big a layout do you have ??????????? It must be huge to need that many channels.

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Posted by fwright on Tuesday, February 12, 2013 5:56 PM

Rick Mugele

The problem with the TAT and DCC decoders is that the throttle is disconnected when the brake is applied.  Also, most DCC F7 brake functions toggle on and off, so there is no way to increase the brake effect, or to reduce it by adding more throttle.  In 1:1 railroading, it is possible to work the throttle against the brakes to make precise stops.  The Dennis Blunt circuits modified the TAT so that it was possible to work the throttle against the brakes (MR, Aug. 1968, pg. 48).  This was all electronic simulation without a powered caboose or tender. The "brakes" were all in the worm gear of the open frame motors of the time.

The "braking" of the motor in the engine is exactly the same input to the motor as reducing the throttle by a pre-determined amount at a pre-determined rate.  Whether the throttle is disconnected when the brake in the model world is applied is a simple electronic function.  When the brake is applied, the controller simply needs to know the state of the throttle, and resume throttle setting - preferably with a reasonable amount of momentum (or delay) - when the brake is released.  The throttle setting at brake application can also be used to determine braking rate and deceleration due to brake.

The point I was making is that in our models, there is only a single input point - voltage to the motor.  The motors are generally linear with voltage, except at the bottom and top ends.  At the bottom, drop the effective voltage below a threshold (threshold varies with real load and pulse shape) and the motor stops turning, locking the drive train.  At the top end, our motors generally have little RPM variation with increased voltage.  The top end is not far off prototype behavior, but the bottom end is very unrealistic.  Therefore, we try to avoid operating near the low end threshold of the motor by high ratio gearing and pulse application.

Also, without a train (caboose) brake, there is no way to take the slack out or put slack in other than changing the speed of the locomotive relative to the rest of the train.  This is the opposite of train brake behavior, which slows the speed of the cars relative to the locomotive.

....The locomotive slid down the hill and derailed with most of the cars.  Most realistic train wreck (Layout Design Journal 40, pg. 4).  Be assured that a permanent magnet motor will stop if there is any kind of resistance across the brushes.  The motor tries to act as a generator against the permanent magnet field.  Lots of resistance.

Agreed, dynamic braking using the motor as a generator is a feasible alternative control method.  But like the prototype, if contained within the locomotive (DCC), cooling is an issue.  Otherwise, a block control system is needed to isolate each locomotive (DC).

It is possible, but very seldom achieved, to have a single thread worm drive be reverse driven (capable of free-wheeling).  NWSL had an On3-sized gearbox with really good bearings that could be reverse-driven.  And that's what would be needed for a fully effective dynamic brake.  But in a conventionally controlled layout this is not necessarily a desirable feature.

IIRC, Steve Hatch's Tsunami setup adjusted momentum, brake, acceleration, deceleration, and throttle values so that the effect was not to disconnect the throttle with brake application, and that the brake could be modulated.  Braking rate might be "locked", but modulation through "blipping" the brake was possible.

As Sheldon points out, very few layouts are suited to the kind of operation you are advocating.  Most operations on a normally compressed layout have enough for the engineer to do with switching moves, time and permission tracking, and other simulations that adding the interplay of train brake and throttle would be task overload.  It would take a quite large layout, with longer than normal sidings to replicate your scenario.  Which is why there is probably so little interest.  I am abstractly very interested in the topic, but on my switching layouts, dealing with flywheel or added electronic momentum is plenty of real world to deal with.  John Allen would probably have been one of the most interested in such a control scheme, but a lot of his operations were over the line trains.

my thoughts, your choices

Fred W

 

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Posted by ATLANTIC CENTRAL on Tuesday, February 12, 2013 4:46 PM

Rick Mugele

Sheldon,

First, I should explain that I did work the steam excusion business and now work as a BNSF engineer, so my view is colored by 1:1 steam and diesel lovomotive operation.  As a model railroader, I think about some of the challenges and joys of 1:1 railroading that have not yet been scaled down for model railroading.  In addition, Bill Darnaby made a wonderful description of a train order meet with steam locomotives (Model Railroad Planning 1995, pg. 58).  "You can actually hear the engineer bringing his train under control as it approaches the west end of Avoca siding."  This engineer must be prepared to stop since his train has no authority past the west end of Avoca until the opposing train is in the clear.  If the engineer simply comes to a stop, then time and momentum will be lost.  If the engineer comes in too hot, he will end up like Casey Jones going through the back of the opposing train if it is not in the clear.  The trick is to set some air and keep working steam to keep the train stretched.  If the opposing train is not in the clear, the throttle can be closed and more air set to bring the train to a quick stop.  If the way is clear, the brakes are released and the throttle opened to get back up to speed.  There is a lot of satisfaction in being able to accomplish this, and more drama than simply turning the knob or pushing the button to make the train stop on a dime and give you nine cents change.

And I do not blame anyone for not liking DCC sound.  Sound systems are not yet able to "lip-sync" the dramatic action of an Avoca style meet.

Meanwhile, I do enjoy the two-button throttle on the radio remote that controls my Athearn HO Challenger.  I have the hot lead to the main circuit board routed through a jack so that a battery car can be plugged in.  On battery power, performance is flawless and "good enough" until something better comes along.

Rick,

I get that, but I don't think too many others are interested - just like few are interested in my integrated DC Advanced Cab Control with CTC and real working interlockings.

They are happy doing what they do with DCC. Most are not interested in signals, CTC, TT & TO operation or how the Westinghouse air brake stops a train (the subject of my 7th grade science project), or how real engineers control thousands of tons of rail car and locomotive.

I know I'm not interested in sitting a simulator, and I'm way more interested in what you have to say then most people I know in this hobby.

The other thing that I would question is the usefullness or effectiveness of such a throttle on most of our selectively compressed layouts?

Sheldon

    

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Posted by gregc on Tuesday, February 12, 2013 4:40 PM

If Linn Westcott were alive today, would he be working with transistors, ICs, FPGAs, micro/picoprocessors, ...?

greg - Philadelphia & Reading / Reading

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Posted by ATLANTIC CENTRAL on Tuesday, February 12, 2013 4:37 PM

Have you tried Aristo's version of direct radio control? also which version of the Train Engineer do you have, I have and use the two channel but just aquired the 10.

No, I never have used the HO onboard Train Engineer.

I have eight of the 10 channel Train Engineer throttles and use them in conjunction with a system of Advanced Cab Control that integrates signaling, CTC, turnout control, and cab assignment into one system.

With a CTC dispatcher on duty, engineers only need to run their train, just like DCC.

Without a dispatcher, many cab assignments are semi automatic and linked to turnout position. turnout positions and cab assignments are then handled at local tower panels that allow complete walk around operation.

The limitation of the Aristo onboard train engineer was the size of the receiver.

I have one of the new Revolution throttles , but have yet to do much with it.

Sheldon

    

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Posted by rrinker on Tuesday, February 12, 2013 4:27 PM

 If the goal is to make a simulator, this can be done in the same manner as Blunt did, the actual control system, DC or DCC, is totally irrelevent. For about the same level of difficulty, you could make a DCC throttle where there is a brake handle that reduces but does not cut off the throttle as it's applied. In an analog fashion.

 Even better, JMRI supports those Rail Driver control stands, to make the brake work against the throttle there would be more along the lines of some scripting code. Then you'd have realistic controls to work with as well (they do, or did, have a traditional-style control stand as well as the more commonly seen console model - hopefully they still make that, since the console is totally inappropriate for my era).

                --Randy

 


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Posted by gregc on Tuesday, February 12, 2013 4:24 PM

a basic throttle controls the voltage to the engine, making the engine go the speed set by the throttle.

When you consider the TAT throttles or others that mimic momentum, the throttle now no longer directly controls the engine speed/voltage, but the desired speed/voltage  and the momentum circuit adds some delay to providing it to the engine.  In other words, the circuit starts becoming a train simulator.  On the TAT, there were controls to select the length/weight of the train that controlled how slowly it reacted.

it's interesting that because each car has brakes, the time it takes a train to slow/stop is not necessarily dependent on the length of the train, while the length (weight) does affect its acceleration.

one approach to building a better simulator is to have separate control for the throttle and brake.  The throttle no longer indicates the desired speed of the engine but the amount of power/force applied to the wheels.   So shutting off the throttle doesn't necessarily cause the engine slow, but simply stops maintaining speed.  Application of the brake causes the train to decelerate.   BEMF could be used to help determine if the train is going up or down hill based on the difference between the applied voltage and BEMF.

the processor within a dcc controller can mathematically simulate the speed of the train given the weight, based on the BEMF and application of throttle and brake.   In other words, it calculates what the train speed should be and applies the necessary voltage to make it so.

there's always emergency stop!

greg

greg - Philadelphia & Reading / Reading

  • Member since
    February 2012
  • 44 posts
Posted by Rick Mugele on Tuesday, February 12, 2013 3:47 PM

Fred,

The problem with the TAT and DCC decoders is that the throttle is disconnected when the brake is applied.  Also, most DCC F7 brake functions toggle on and off, so there is no way to increase the brake effect, or to reduce it by adding more throttle.  In 1:1 railroading, it is possible to work the throttle against the brakes to make precise stops.  The Dennis Blunt circuits modified the TAT so that it was possible to work the throttle against the brakes (MR, Aug. 1968, pg. 48).  This was all electronic simulation without a powered caboose or tender. The "brakes" were all in the worm gear of the open frame motors of the time.

Likewise, the implication was that the TAT could be adjusted so that it would respond by making the locomotive go faster when going downhill, so that the "brakes" would actually have to be "applied".  I have not seen any reports of this being done.  It would be interesting to know if this can be done with a DCC decoder.

BTW, I did have too many cars behind a locomotive on too steep a grade.  The locomotive slid down the hill and derailed with most of the cars.  Most realistic train wreck (Layout Design Journal 40, pg. 4).  Be assured that a permanent magnet motor will stop if there is any kind of resistance across the brushes.  The motor tries to act as a generator against the permanent magnet field.  Lots of resistance.

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