capacitor power to bridge momentary track power loss

Dan,

The answer to your question is "Yes, but why?"

The challenge in powering over dirty track is the motor isn't able to pull enough power (voltage and/or current) to continue the locomotive's smooth travel over the dirty section of track.

It is true that the CC is likely also starved similarly, but fixing the CC's shortfall, without also providing keep-alive power to the motor, doesn't help the loco travel more smoothly, which is what is most noticable and troubling to the operator.

Powering a motor over bad sections would require a very large capacitor, and significant related circuitry, which wouldn't likely fit easily inside the loco.

How about adding a battery to handle the task?  Yes definitely, but then there's no need for AC powered tracks, and the need to clean them.  It's called 'dead rail' and many people swear by it.

Mike

    Thanks Mike

     I can see where battery power would work, but they would be pretty large also  right?

     I guess I sometimes have a problem where an engine stops and the lightest nudge of the locomotive restores power to the unit and board. It can be troublesome when running multiple unit consits where one loco stalls/loses it's speed and signal and the other keeps pulling. They then get out of cycle.

     I'm just trying to figure a way to briefly power the board during the interruption.

     To be honest, I don't have many troubles with this. Some engines run around never seeming to hit a dead spot while a couple of others seem to be rather glitchy.

                                                                                                                     Dan

You might want to take a look at YLB. It isn't meant to power motors, but does keep the sounds and maybe "computer" in sync like you are asking.

https://ogrforum.com/...st-impressions-great

http://hennings-trains.shoplig...unds-batt-repla.html

    Thanks bmoran4

    The YLB might work. I've never used one and always understood them to power the sound board and also, maybe the power board for MTH products. Not sure. Thanks for the thread link.

                                                                                             Dan

Some other options come to mind:

1) Try to identify the cause of the voltage drops, it may not be dirty track, rather it could be loose connections between pieces.

2) Adding more individual power connections every 8 to 10 track sections (unless you're using DCS) will also help.

3) Another option is if any of the problematic locomotives have only one pick-up roller or two that are are spaced closely together, adding another pick-up roller either to that locomotive or to an adjacent car/tender and wiring the additional pick-up roller back to the main power hot wire inside the locomotive.  This increases the likelihood that at least one of the pickups is getting sufficient voltage to keep things moving.

    Thanks Steve

    Admittedly I have no power drops around my 50' loops. Gargraves track going on about 10 years so power drops will undoubtedly help.

    I have 2 identical locos where one will run all over and never find a dead spot. The other I've resoldered all wipers and roller wires. It still is finicky for some reason. May be the board itself, but like I say one tiny nudge and it powers back up but in neutral.

    I have tied the two outer rails together where there is no insulated track stretches.

I just addressed a small steam locomotive that had direction control "spazzing out". Turned out to be a traction tire that was out of round causing a slight waddle minimizing that minimized the outside rail pickup points to a super sensitive level. Replaced tire and all is well. Not that this is your issue, but food for thought since we are thinking outside of the capacitor box.

  Thanks bmoran4

  I had to tie my outside rails together because I was having some outside rail connectivity problems. I did look into a metal infused electrical rubber product and surprisingly there is such a product.

  Maybe they should look into making traction tires for us.

If the "lightest nudge" is all it takes to restore power, then another approach is to increase the inertia (weight) of the mechanical flywheel.

This has been discussed before and the analysis is pretty nerdy, but if you're looking to coast thru track power interruptions, you're better off storing energy mechanically (vs. electrically).  That is, a capacitor's stored energy has to be converted to mechanical energy via the motor which has conversion losses as well as energy needed to run the motor drive electronics.  OTOH, the flywheel stores energy in directly usable form as mechanical momentum to advance the locomotive in the absence of track power.

So if looking for ideas outside the capacitor box you'll find interesting online discussions of modifying flywheels - for example using tungsten instead of brass as tungsten is more than twice as heavy.

Practically speaking I don't expect many guys have the ability to work with tungsten and/or to fabricate their own flywheels.  But OGR being a discussion forum to, uhh, discuss ideas... on a rainy afternoon with nothing else to do, attach coins (half dollars or whatever) to the existing flywheel.  This is just an experiment as you may not have the clearance to put the engine "shell" back on.  Again, the "math" is pretty nerdy but if the added flywheel momentum works, one can then ballpark the size of capacitor needed if that's where you want to store the reserve energy.  That is, most guys also don't have the size/type of capacitors needed just lying around...much less the comfort level tapping in to the motor electronics risking the dreaded release of magic smoke.

Fast Freight, It sounds to me like your losing ground. I had this problem once MTH came out with the 2 rail - 3 rail option on their engines. Only one side of each truck on diesels make ground contact on opposite sides of each other. I use a piece of glass, that was once a shelf in a bathroom medicine cabinet, to check the bad spot for flatness. You may be able to find one to borrow in your home. Lay it on the tracks exactly where the engine stops at a slow speed. What your looking for is a twist in the track where the ground rails cause the glass to have a gap under opposing corners. See if the glass teeters diagonally or slide a strip paper under the corners to check. Then just shim under the track, as needed, to get it flat.

Welcome to the wonderful world of engines , one engine can be fine, another engine is like a cat when you give them food they don't like or an Italian sports car when they decide the day isn't just right..... One thing that could cause this is lack of feeds, one of the simplest things is adding more power drops, and is just good operating procedure IMO.  Usually things like not enough rollers hit you on switches rather than open track running, unless something has only a single roller. You were smart to tie the negative rails together (something I'll have to remember to do on my layout long under construction...), that is another relatively simple fix. Another thought is check the rollers on that engine, make sure that they have full travel. If a roller has limited travel, if there is a 'dip' in the rail, even a small one, it could do what you are talking about. If the spring that pushes the roller to contact the rail is weak, you could have the same problem.

Stan is certainly right, the capacitor would have to be fairly immense to do this job!  However, many times adding a flywheel or a heavier flywheel just isn't practical for a variety of reasons, then the capacitor idea may have to be revisited.

If I were doing this with electronics, I'd consider a DPDT relay and a supercap.  The relay is to keep the polarity to the supercap proper, and the relay would be driven using a steering diode from the motor voltage to maintain the capacitor polarity.  A couple of 5V 1.5F supercaps in series should be enough, and you could always add one of motor voltage exceeds 10V.

@stan2004   I do have an idea about increasing the energy of a flywheel and may try that. I haven't drawn it up yet but picture this.

Take the flywheel off the motor and replace with a gear the same diameter of the motor. Now add 2 small bearings outside the motor where a shaft could go with a small gear meshing with the large gear and the flywheel on top of that. That might make the flywheel spin a lot faster ie storing more energy.

I'm still thinking somehow briefly powering the board as well might help.

@Dave Zucal  Yep, My track work could use some track work. I agree those MTH 2/3 rail locos can have some ground issues.

@bigkid I have an old army jeep that behaves like an Italian sports car. One day runs great, the next day the dew point drops and it stutters everywhere.  Some trains do behave the same way.

@gunrunnerjohn If I'm following correctly, the super caps are powering the motors briefly correct? I'm trying to power the board briefly as well. Not sure if it's possible. Maybe leach a little current off the super caps into the board after the bridge rectifier.

@fast freight posted:

Take the flywheel off the motor and replace with a gear the same diameter of the motor. Now add 2 small bearings outside the motor where a shaft could go with a small gear meshing with the large gear and the flywheel on top of that. That might make the flywheel spin a lot faster ie storing more energy.

I think you'll find that trying to increase the speed like that will incur a lot of friction, and also at any speed, it'll sound like an airplane on a takeoff roll!

@fast freight posted:

@gunrunnerjohn If I'm following correctly, the super caps are powering the motors briefly correct? I'm trying to power the board briefly as well. Not sure if it's possible. Maybe leach a little current off the super caps into the board after the bridge rectifier.

While possible, that would be much harder to accomplish as you'd have to tap into the electronics on the Cruise Commander.  I actually thought of a glitch in my idea anyway, the Cruise Commander works by monitoring the back-EMF of the motors, but the capacitor will mask that and thus render the cruise non-functional.

@fast freight posted:

    ...I have no power drops around my 50' loops. Gargraves track going on about 10 years so power drops will undoubtedly help.

RIGHT THERE IS THE PROBLEM. There is no way that 50 feet of track can function with only a single power feed. All this capacitor, flywheel, and battery talk is treating the symptom, not the disease.

Add some feeders and you will solve the problem.

I actually fired up my 24 x 12 layout the first time with one power drop, and it worked surprisingly well considering.  However, there was a significant power drop at the far end, though the rail pins did way better than I expected!  FWIW, I now have about 70 power drops throughout the layout, I never intended to actually depend on that operation.

@Rich Melvin posted:

RIGHT THERE IS THE PROBLEM. There is no way that 50 feet of track can function with only a single power feed. All this capacitor, flywheel, and battery talk is treating the symptom, not the disease.

Add some feeders and you will solve the problem.

   Understood Rich, yet......like I said some locos will travel that 50' and rarely hit a dead spot while others will stumble more often. Guess I'll crawl under the bench work.

@gunrunnerjohn posted:

I think you'll find that trying to increase the speed like that will incur a lot of friction, and also at any speed, it'll sound like an airplane on a takeoff roll!

While possible, that would be much harder to accomplish as you'd have to tap into the electronics on the Cruise Commander.  I actually thought of a glitch in my idea anyway, the Cruise Commander works by monitoring the back-EMF of the motors, but the capacitor will mask that and thus render the cruise non-functional.

    Thanks John

    Maybe I'll try the flywheel on one of those jet powered experimental locos they tried.

    As for momentarily powering the board, maybe not possible.

I was thinking of some steering diodes for the battery power to avoid compromising the back-EMF sensing so that the supercap could power the motor but not affect reading the back-emf...  I'll have to think about that, not seeing how it would work...