Getting MTH PS3 steam to Coast (in Conventional)

I'm going to go into an area where I don't have all the facts and am only working off of theory and such.  I don't know enough about these engines to know if anything that follows is actually true in this particular case.  

There are two things I can think of that contribute to an engine coming to a sudden stop when cycling to neutral.  The first is the mechanical drivetrain.  it may be that the gear box is designed in such a way that if the motor is unpowered the wheels simply can not turn.  If this is the case, one would need an e unit that gradually reduces motor power in order to get any sort of coasting effect.  The second is that the e-unit in place may be effectively connecting both of the motor's connections together, which would cause the motor to act like a brake on the drive train.  If this is the case, using an e-unit that floats the motor when it is unpowered may allow it to coast...some.  

I'm unfamiliar with the Dallee unit, so I don't know if it would help with either of these problems.  I do know that if one were so inclined they could fairly inexpensively construct their own e-unit that could counter either problem.  One might even be able to do something inline with the PS3 electronics that would allow all of the engine's sounds and features to remain intact while allowing the engine to coast to a stop.  

All that said, I'm curious why it wouldn't be worth the time to code the boards properly in the first place.  It seems to me there are plenty of people that run conventional, and  a strong contingent of folks that are only interested in conventional operation and have no desire to ever run any form of command.  If I bought an engine advertised to be fully functional in conventional, I'd like it to perform well in that environment.  I've always used the direction buttons to stop, and expect many others do as well, sort of a "feature" of conventional running in my opinion.  

JGL

SJC posted:

... MTH has said the coasting issue is a software issue, not a hardware issue. They are aware of it but don't really intend to fix it.

 

I know you've been all over this issue for over a year now.  Earlier this year you commented in another thread that MTH is/was working on a PS3 software update for this.  Do you have new information that this is no longer the case?

stan2004 posted:

SJC posted:

... MTH has said the coasting issue is a software issue, not a hardware issue. They are aware of it but don't really intend to fix it.

 

I know you've been all over this issue for over a year now.  Earlier this year you commented in another thread that MTH is/was working on a PS3 software update for this.  Do you have new information that this is no longer the case?

I contacted MTH's Andy E. about this in March of this year. Per his email back, R&D would look into it again to see if a software update was possible. I did just follow up last night about it, hopefully I'll get something in the next few days back. He did note that a previous attempt to fix this, several years ago failed. It failed because 1) Little consumer feedback 2) Lack of positive results in the fix the tried. 3) Declining numbers of conventional control operators. 

See my post about the issue.  I'm wondering if some diodes and a directional relay would fix this.  I suspect it's because of dynamic braking when the power is removed and the drivers provide a current path from the motor leads and stop the motor too quickly.

gunrunnerjohn posted:

See my post about the issue.  I'm wondering if some diodes and a directional relay would fix this.  I suspect it's because of dynamic braking when the power is removed and the drivers provide a current path from the motor leads and stop the motor too quickly.

Link?  I don't know about his specific collection of PS3 engines but there's not much room to add a relay.

If this is the dynamic braking issue as JGL and GRJ surmise, it seems to me it would also show up in command mode when E-stop is pressed as track power is instantly removed from the track.  Point being while E-Stop is not a "normal" operating mode the software fix would benefit more than just the conventional guys.

stan2004 posted:

gunrunnerjohn posted:

See my post about the issue.  I'm wondering if some diodes and a directional relay would fix this.  I suspect it's because of dynamic braking when the power is removed and the drivers provide a current path from the motor leads and stop the motor too quickly.

Link?  I don't know about his specific collection of PS3 engines but there's not much room to add a relay.

If this is the dynamic braking issue as JGL and GRJ surmise, it seems to me it would also show up in command mode when E-stop is pressed as track power is instantly removed from the track.  Point being while E-Stop is not a "normal" operating mode the software fix would benefit more than just the conventional guys.

Link is HERE.

This GS4 Daylight is the only PS3 steam engine I have presently that has this issue. I know of at least two others I have had that have the 'quick stop" issue. One is the MTH Imperial Mikado and the Other is the MTH Imperial 0-8-0 switcher, both PS3 products.  FWIW, my only other PS3 steamer, an Imperial Railking 0-6-0 (from 2013) DOES coast in conventional and operates beautifully. It doesn't coast as far and long like some other PS2 engines but it doesn't skid to a stop.

I apologize for not address JohnGaltLine's post sooner. Without power, the drive wheels can't be turned due to gearing. This is common with all MTH locos. I use the direction  button all the time, especially when switching. Granted I won't be switching with a large 4-8-4 passenger engine but still, even throttling down a bit quick will cause it to lock up and skid. Extreme caution is required. My biggest concern with this issue is the gears getting chewed up after this happening one too many times, even with extreme care in preventing it. This is especially true on the club layout with several people operating on the same track at once. One E-stop press or short is all it takes.

Doesn't the engine have a Fly-Wheel? 

Why does it have to "coast" anyway?

Hot Water posted:

Why does it have to "coast" anyway?

Because he would like it to when he removes power.

A heavier flywheel seems in order; I guess that they have been using a software solution to fix a mechanically-correctible problem. If so, not a good idea. So 21st-Century, it seems, on the surface. But I don't know.

My WBB 027 Alco FA-2's, which I upgraded to ERR Cruise Commander/RS, have light flywheels and to not coast (stop gracefully) as well as I would like, but it's not bothersome - I know how to drive them.

Flywheels - not software. That's the ticket. 

Hot Water posted:

Why does it have to "coast" anyway?

As SJC says, if you remove track power (by pressing the DIRECTION button) the engine locks up coming to a violent halt and potentially de-railing cars.  It has been pointed out that the same engine, same motor, same flywheel, but different electronics/software (PS2 vs. PS3) behaves differently.  Hence it's not that MTH is replacing or trying to replace the flywheel with software.  Instead it seems the PS3 electronics/software is behaving in a manner which demotes the coasting potential of the flywheel.  As discussed the consensus is dynamic braking (something which the software can apparently control) is stealing this coasting energy from the spinning flywheel for whatever reason.  In the case of a hybrid-electric vehicle, dynamic braking is used to charge the battery.  I wouldn't expect to see any published analysis of if/how/why MTH changed the flywheel dynamics going from PS2 to PS3.  For that reason I don't think there would be substantial gain to simply increasing the size of the flywheel.

In addition to violently derailing the train behind it, this issue also SHREDS the traction tires if you are not careful. Not to mention, I'm sure it does a number to the motor, steam driving wheels/valve gear and internal gearing. I want and expect to have these trains running for years to come.

Andy at MTH got back to me. He said R&D was going to look into it and he would follow up and get back to me if there was any news. R&D tells Andy that if there is a simple software fix, they will pursue it.

I suspect the difference is the PS/3 electronics use different motor drive circuitry.  AFAIK, the flywheel in the PS/3 locomotives are the same size as the similar models in PS/2.  I believe this to be a change in the electronics, perhaps an unintended consequence of the upgrade to PS/3.

So, at this point am I correct in saying that the drivetrain in question is not the most awesome to allow the engine to coast to a stop, but that the same exact drive drain (gears, motors, flywheels, etc) DOES coast to a satisfactory amount on engines with the PS2 electronics.  

Under that assumption, does anyone have some photos of the PS2 and PS3 boards in use?  I know that in at least one of these relays are used to switch the power control to the motor(s) and am curious if the other uses semiconductors instead to form the H-Bridge. (Triacs, FETs, Transistors, etc.) The semiconductor method naturally floats the motor where it would not cause substantial breaking, where as a relay H-Bridge would when wired in typical fashion.  

Before hypothesizing further I'd like to see the boards in question just to get an idea of the components in use.  

JGL

_{See disclaimer in my previous post if needed.}  

SJC posted:

...

He did note that a previous attempt to fix this, several years ago failed. It failed because 1) Little consumer feedback 2) Lack of positive results in the fix the tried. 3) Declining numbers of conventional control operators. 

 

If cars derail, traction tires shred, gears slam together, etc. when you press E-stop or when a breaker trips from a track short...then I'd this is an issue for ALL users, not just the conventional guys.

I'm surprised there hasn't been more "consumer feedback" from command operators. Or if lack of feedback means the command operators don't care, perhaps it would be easier for MTH to alter the coasting software only when in conventional mode. 

At minimum it seems your cause can only be helped if other conventional control operators would send a note to MTH about this issue. 

I agree however it seem it's only happening with  some later ps-3 engines.  Not all of them.  What's going on?

FWIW, I notice that with DCS (had to find my long lost DCS set), the same "quick stop" issue is present with the E-Stop command. Double tap of the brake button and direction button both brought slow, coasting stops. Deceleration was set at 2, I cranked it up to 25 (limit) and noted the engine would now "quick stop" like it does in conventional. Turning it down to 1 brought nice, coasting stops. Back in conventional, no changes whatsoever. 

Well, now we're shooting in the dark and speculating.  From what I've read this occurs in PS3 STEAM engines.  Since the flywheels are the same in PS2 and PS3, and PS2 coasts just fine, the question is what's different?  AFAIK, all PS3 steamers have a processor in the engine (in addition to the one in the tender).  PS2 only has a processor in the tender.  Of course the flywheel in a steamer is in the engine (and I haven't read reports of this happening in a diesel).  So it could be about the "new" software in the engine processor and how it interacts/uses the energy in the flywheel that's the design issue.  Apparently MTH understands the issue (and we don't) so we're just playing 3-blind-mice scurrying around for cheese...

I suggest there's little to be gained in speculating why/how MTH designed the coasting software as they did.  I'm more curious about if anyone other than SJC has even given them feedback.  To that end, that's why I suggest if this is a concern to anyone to send a note to MTH.  From what I can tell MTH has not said "no"... and the squeaky wheel does get the grease.

stan2004 posted:

Well, now we're shooting in the dark and speculating.  From what I've read this occurs in PS3 STEAM engines.  Since the flywheels are the same in PS2 and PS3, and PS2 coasts just fine, the question is what's different?  AFAIK, all PS3 steamers have a processor in the engine (in addition to the one in the tender).  PS2 only has a processor in the tender.  Of course the flywheel in a steamer is in the engine (and I haven't read reports of this happening in a diesel).  So it could be about the "new" software in the engine processor and how it interacts/uses the energy in the flywheel that's the design issue.  Apparently MTH understands the issue (and we don't) so we're just playing 3-blind-mice scurrying around for cheese...

I suggest there's little to be gained in speculating why/how MTH designed the coasting software as they did.  I'm more curious about if anyone other than SJC has even given them feedback.  To that end, that's why I suggest if this is a concern to anyone to send a note to MTH.  From what I can tell MTH has not said "no"... and the squeaky wheel does get the grease.

 

 

FWIW, Barry Broskowitz reported, after testing, that his Imperial Mikado also had the "quick stop" problem and reported it to MTH so I'm not the first one to tell them. 

I should also reaffirm that I have another PS3 steamer, 30-1570-1, that DOES coast in conventional. This is, apparently, a recent PS3 steam issue.