Has anyone added additional Super Capacitance to MTH 44 Tonner?

Can you provide a link to the articles you alluded to?  I'm not sure a supercap is involved.

Of course a supercap is involved, it's the only thing that would extend the running time after power is removed.

Being  a conventional runner, I did not realize that any engines had supercaps in them.  None of the four caps in there looked like supercaps either by their physical size or (for the ones you can read the markings) capacitance.

Trust me, there is a couple of them there.   Here is a standard PS/3 diesel board, note the two supercaps.

Ah - those are indeed supercaps! 

The blue ones are the supercaps in the 44-tonner.  You can tell by the brand name and the fact that there are two.  Note they're smaller than the ones used on the diesel PS/2 board, that's the basic problem.

Correct me if I'm wrong, but I don't believe MTH puts caps on the motor drive circuitry, only on the sound. I noticed this trying to run my Hi-Rail H-10 on 2 rail Gargraves Hi-Rail track. Whenever it crossed the insulated turnout frog at low speed it would instantly stop even though the sounds would continue for a bit. This was a surprise to me and really drove me nuts because in the HO models they DO puts caps on the motor drive. This is the sole reason I abandoned my MTH 2 rail Hi-rail experiment. Even though it worked in this video, it was inconsistent at best.

MTH has great ideas, but they usually fall short on execution. This is just another example.

It's not on the actual motor drive, but it does hold up the electronics so that they won't go dark on a brief power glitch, that's what we're talking about.

I thought flywheels where suppose to get us over the dead spot ?

If they were about five times the mass, they might do the job.

I don’t see any reason why you couldn’t add larger supercaps to the board.

What is the rating on the 44T supercap?

I'm not an electrical engineer, so forgive me if this is a dumb question: Are these supercaps or the lack of them in any way related to the issue that PS3 locos supposedly don't coast when operating in conventional mode?  As far as I know MTH never provided a firmware update or any kind of resolution.  (I don't even know if they officially acknowledged the issue.)

Supercaps in MTH PS3 locos do not provide power to the motors.  They only provide power to the electronic controls which otherwise might drop out when there are breif interruptions of power, such as when going over dirt.

RJR posted:

Supercaps in MTH PS3 locos do not provide power to the motors.  They only provide power to the electronic controls which otherwise might drop out when there are breif interruptions of power, such as when going over dirt.

Which does no good if the engine stalls on a dead spot. Their HO models and pretty much every other DCC decoder with Caps buffer the motor drive as well so the engine keeps moving over the bad spot. Stupid choice by MTH to not stay consistent in their implementation if you ask me.

No one asked you.  Before accusing MTH of stupidity, please provide your calculations of the size supercap required to power 2 O gauge size motors over a gap.

Wow, Johnny he dun told you

I am hoping that someone will provide a part number and wiring instructions to fit above the white label in picture.

jonnyspeed posted:

RJR posted:

Supercaps in MTH PS3 locos do not provide power to the motors.  They only provide power to the electronic controls which otherwise might drop out when there are breif interruptions of power, such as when going over dirt.

Which does no good if the engine stalls on a dead spot. Their HO models and pretty much every other DCC decoder with Caps buffer the motor drive as well so the engine keeps moving over the bad spot. Stupid choice by MTH to not stay consistent in their implementation if you ask me.

RJR posted:

No one asked you.  Before accusing MTH of stupidity, please provide your calculations of the size supercap required to power 2 O gauge size motors over a gap.

I don't always agree with what he says about MTH. He does point out what's wrong here. There are plenty of decoder brands that have developed over recent years and the subject of keep alive circuits keeps coming up. I have to believe that MTH has at least looked at the problem. If they skipped it or ignored it, I don't know? Someone there must have ran the engine at least once and I would hope they saw how it stopped without coasting.

 Remember the video that MTH released that showed someone placing black tape on the track and how MTH engines would keep running over it? What happened to that claim? Would this 44 ton engine run over the tape?

 I don't believe that we require any poster to have an engineering degree to post about a known problem with an engine. The focus on keep alive circuits is not new. We should be able to discuss it here.

Given that the O-gauge models weigh many times what a comparable HO model weighs, I suspect supercaps to do a keep-alive function for the motor drive would be pretty huge.

A couple of points and a slightly unrelated question of my own. 

First, the PS3 problem of the train coming to an abrupt halt when power is interrupted had nothing to do with the super capacitor inside the locomotive. It has to do with the circuit design.

For whatever reason, the problem only occurs when running the PS3 locomotives in conventional mode. They work fine with DCS.

Second, since no one is offering any specific alternative for a larger super cap, is there a reason? Aside from how much space it would fill? The 44-tonner, which has excellent sound, does cut out too quickly during the shutdown sequence, so I too am curious if there is a practical alternative. 

And finally, to CTR, since you have already found a reason to remove the diecast body, can you tell me if the shell is two or three castings? I know the cab is separate from the front and rear hoods, but are the hoods a single casting that connect under the cab? I hate to nose around out of simple curiosity, in fear of pinching some wires on reassembly, so I haven’t removed the shell from the frame on my unit yet. And MTH still doesn’t have any exploded drawings of this model on its website, so my curiosity remains unfulfilled. 

Jim R. posted:

For whatever reason, the problem only occurs when running the PS3 locomotives in conventional mode. They work fine with DCS.

I could only guess that it's in the DCS programming then? as long as it sees the power...

It was discussed somewhere before.

RJR posted:

No one asked you.  Before accusing MTH of stupidity, please provide your calculations of the size supercap required to power 2 O gauge size motors over a gap.

Last time I checked this was an open forum. One that I have been a member of for over 17 years. I also have significant real world experience in many scales so I have amassed a good amount of information that some may find helpful. If it hurts your brand-loyalty feelings that I called their decision stupid then that is your problem. I have a very sound and logical reason for making my statement. Do you have the same for a counter-point? Didn't think so.

IF the motors were wired in parallel then the current draw would not be much more than that required for HO. An Atlas RS-1 (twin motors) with parallel wiring draws ~1A with wheels slipping. There are many options in the DCC world that will easily power those motors. How do I know? I have converted Atlas, MTH, and Lionel models with dual motors to 2 Rail with DCC and keep-alive caps. I've used TCS, ESU, and QSI decoders and caps from SoundTraxx, ESU, and TCS.

MTH electronics don't appear to be as efficient as modern DCC alternatives.My guess as to why they chose to move the caps off of the motor drive is probably due to cost or packaging. Regardless of why they did it, it created models that do not perform as well as DCC electronics in a 2R application. I don't think anyone would argue with that.

I asked MTH why they made the choice on Facebook but they never responded.

ctr posted:

Previous posts have mentioned that the MTH PS3 44 tonner has insufficient Super Capacitor.

Insufficient to do what?  Can you provide links to the exact discussions you refer or perhaps summarize what behaviors are insufficient.  There seem to be multiple conversations going on which is confusing.  

Also since you have the board exposed can you carefully bend up the caps in question and report the markings/lettering to help identify the parts in use?

My 2 cents,  not sure if this observation helps. I have 10 DCS PS-2 and 9 PS-3 all 2/3 rail except my 44 tonner, PS2 very seldom if ever miss a watch dog signal, work very well in lash-up mode of over four engines, never stall and never stop fast when power is lost. all my PS-3 have those problems. I have a 0-6-0  2 rail that I had all the wheels tied to ground, and a third roller installed now it is just as good as PS-2  or better. Even smokes better now. 

This is just my experience it means nothing.

Clem 

clem k posted:

I thought flywheels where suppose to get us over the dead spot ?

Correct. It is quite impressive the energy stored in what seems like a tiny flywheel.  The math is somewhat geeky with calculations of rotational inertia blah blah blah.  If you have nothing better to do on a rainy afternoon try putting a couple of half-dollars or whatever on top of the existing flywheel and watch how it affects coasting distance!  Much more economical than storing energy in electrical form (such as a capacitor) which would then need to be converted to mechanical energy thru the DC motor which is a relatively inefficient conversion.

The shell comes off in one piece. Remove 4 screws, pull handrails and grabs loose from shell. Gently pull apart. disconnect light plug.

It is a very tight fit. and more difficult than most to reassemble.

Stan2004,

Insufficient to keep alive in DCS mode over track irregularities or short electrical gaps.

The engine is no longer apart and based on above comments is unlikely to be without more knowledge on this subject. I am sorry that my answer doesn't help much.

ctr posted:

The shell comes off in one piece. Remove 4 screws, pull handrails and grabs loose from shell. Gently pull apart. disconnect light plug.

It is a very tight fit. and more difficult than most to reassemble.

It would be nice if we could concentrate on getting an answer to original question without all the unhelpful opinions. I am seeking an answer--not a dog fight.

Apologies for derailing your thread. I thought it relevant. I'll bow out now.

Engineer-Joe posted:

 Remember the video that MTH released that showed someone placing black tape on the track and how MTH engines would keep running over it? What happened to that claim? Would this 44 ton engine run over the tape?

Yes, I remember that video!  I think it featured a Protosound-1 F-unit circa 1995.  I highly doubt the 44-ton diesel or ANY PS3 loco would pass that test.  Combination of self-locking gears, circuit design, lack of capacitance driving the motor, and flywheels that are the size of two quarters stacked together .

I have a Lionel 6-11203 Berk that will coast about 30" when power is cut from full speed.  I have no idea whether it has supercaps, and no knowledge of the circuit design.  I do know that about 10 years ago, Lionel began using BACK-DRIVABLE worm gearing on many of their Legacy locos, which allows some coasting.  The idea isn't new; postwar locos used back-drivable multi-threaded worms.  I happen like this solution, and if the model I want is available with this feature, that's the one i would choose.  The amazing thing is that in the Legacy locos, Lionel was able to make the gears back-drivable, and still keep the gear ratio low (numerically high) enough to achieve a speed range that's not too fast!

Stan, I have one of the first delivered.  The PS3 board would regularly drop out (I run trains very slow much of the time).  Discussions with MTH disclosed my particular board would keep operating about 0.25 seconds less than the desired minimum.  Adding extra capacitance (I don't recall how much and am not about to reopen the loco) cured the issue.  It can crawl anywhere on the layout.

stan2004 posted:

ctr posted:

Previous posts have mentioned that the MTH PS3 44 tonner has insufficient Super Capacitor.

Insufficient to do what?  Can you provide links to the exact discussions you refer or perhaps summarize what behaviors are insufficient.  There seem to be multiple conversations going on which is confusing.  

Also since you have the board exposed can you carefully bend up the caps in question and report the markings/lettering to help identify the parts in use?

Stan, I'm one of the ones that mentioned this deficiency.  My 44-tonner drops out about one second after power to the track is interrupted, much too short a time, and a lot shorter than any other PS/3 or PS/2 locomotive.  I haven't popped the top on mine yet, but from the pictures here, I see that the supercaps used on the 44-ton board appear shorter (and thus probably lower capacity) than the ones used on the standard diesel boards. 

I also suspect the PS/3 board design doesn't get full benefit from the capacity of the supercaps, it probably drops out well before they're mostly discharged, thus necessitating the need for more capacitance.  I'll be interested in finding out what capacitance those caps are, the ones on the PS/3 diesel board are 5F 2.7V.  They're wired in series to give a 2.5F capacitance.  I suspect those small ones I see in the picture of the 44-ton board are not more than maybe 3.3F.

ctr posted:

...Insufficient to keep alive in DCS mode over track irregularities or short electrical gaps.

Understood.  So 2 things must happen to deal with the short electrical gaps from loss of track power.

1) Electronics must stay alive for the duration of the power interruption.   We are talking about gaps in the fraction of a second.  This is the job of the supercap or other electrical storage device (like the battery in PS2).

2) The engine must physically coast thru the length of the track irregularity until track power is restored on the other side.  This is the job of the flywheel.  As several guys have pointed out, the supercap has nothing to do with providing mechanical reserve power to get the engine to the other side of a physical gap in track power.  It makes sense that this is a bigger issue at slow speeds.  The energy stored in a spinning flywheel is proportional to squared-RPM.  Doubling motor speed quadruples energy stored in the spinning flywheel.

Increasing the supercap size can solve the case where the flywheel moves the engine across the dead rail...but does not keep the electronics alive for the duration.  The electronics drops out and when the engine reaches the live rail, the electronics starts again - probably powering up in conventional-neutral since there was no watchdog.  

But increasing the supercap size will not solve the case where the flywheel is not large enough to carry the engine to the other side of the gap.  In this case the engine is on a dead rail.  The electronics will play out the shutdown sound to completion.  But game over.  You are stuck on a dead rail and have to manually slide the engine onto a live track section.

A possibly confusing scenario is if you are operating on the edge.  That is, you have many track irregularities and the supercap is constantly being called into action to keep the electronics alive during gaps.  The flywheel is doing its job to carry the engine thru the gaps.  So what can happen is each brief interruption draws down the supercap.  When power is restored the supercap must be charged up.  But as you know from the initial waiting time on PS3, the charging time can be quite long (tens of seconds).  So living on the edge means the supercap is constantly charging/discharging.  Everything seems fine except, on average, the supercap is never fully charged.   So you perform the remove-track-power "test" and the shutdown sound plays to completion...but this is because the engine was stopped and the supercap had been allowed to charge up to full.

stan2004 posted:

So you perform the remove-track-power "test" and the shutdown sound plays to completion...but this is because the engine was stopped and the supercap had been allowed to charge up to full.

The issue with the 44-ton locomotive is that even if you let it charge for minutes and cut power, it will drop out in about a second, and it doesn't get anywhere close to finishing the shutdown sound to completion.

ctr posted:

The shell comes off in one piece. Remove 4 screws, pull handrails and grabs loose from shell. Gently pull apart. disconnect light plug.

It is a very tight fit. and more difficult than most to reassemble.

Stan2004,

Insufficient to keep alive in DCS mode over track irregularities or short electrical gaps.

The engine is no longer apart and based on above comments is unlikely to be without more knowledge on this subject. I am sorry that my answer doesn't help much.

RJR posted:

Stan, I have one of the first delivered.  The PS3 board would regularly drop out (I run trains very slow much of the time).  Discussions with MTH disclosed my particular board would keep operating about 0.25 seconds less than the desired minimum.  Adding extra capacitance (I don't recall how much and am not about to reopen the loco) cured the issue.  It can crawl anywhere on the layout.

So here's your answer... sort of. Contact MTH and see what they told him to do.

If you don't like discussions on a subject you post, maybe state that in the beginning. Also try a search on what others have done.

I am going a little about these supercaps, Are they also called super capacitors?

Never mind, I googled it.

A supercapacitor ( SC ) (also called a supercap , ultracapacitor or Goldcap ) is a high-capacity capacitor with capacitance values 

gunrunnerjohn posted:

 

The issue with the 44-ton locomotive is that even if you let it charge for minutes and cut power, it will drop out in about a second, and it doesn't get anywhere close to finishing the shutdown sound to completion.

gunrunnerjohn posted:

 

I'll be interested in finding out what capacitance those caps are, the ones on the PS/3 diesel board are 5F 2.7V.  They're wired in series to give a 2.5F capacitance.  I suspect those small ones I see in the picture of the 44-ton board are not more than maybe 3.3F.

Well, if a fully charged supercap (pair) drops out in ~1 sec, seems to me the solution isn't as simple as doubling or even tripling the capacitance.  That is, wasn't the rule-of-thumb to test for a good battery or battery-replacement to remove track power and listen for 8-10 seconds (or whatever) of shutdown sounds?  If the pair of blue capacitors in the photo only gets ~1 second, this suggests you ~10 times more capacitance since reserve-energy is proportional to capacitance.  Would it fit?

Does this engine have a particularly short shutdown sound sequence to compensate for the lack of reserve electrical energy?

Separately, I'd think there would be griping from the conventional operators.  The supercap keeps the electronics alive when the DIR button is pressed which of course removes track power for, say, ~1 sec.  Seems a sequence of relatively closely spaced direction changes (in conventional) would deplete the supercap (not enough time to recharge) and then the direction change would cause the electronics to drop out...the engine would then have to go through the startup sequence when the DIR button is released.

Stan, trying to recall a few years ago when I was discussing this with MTH, I think they were shooting for >2 seconds; certainly not less.

Well, that's the situation with my 44-ton model, and when I got it, I even swapped it because the first one did the same thing.  After getting the second one and having exactly the same issue, the penny dropped.

Oh, and the 44-ton engine does indeed drop out if you do a couple quick reverses in conventional mode unless you're very quick on the button.

This drop out problem is especially annoying when running in Lashup mode. The second engine provides enough momentum to push through electrical discontinuities--but the first engine drops out of DCS mode and comes up in Conventional (stopped.) So one engine is pushing against a dead stopped engine. Not good!

RJR.

Who did you talk to at MTH about this?

What did they tell you?

Who installed the additional Super Capacitors?