How frequent are derailments?

[Harlequin]

You were asking about frequent derailments. Wheels dropping into flangeways may or may not be related.

I hope other people’s videos don’t show frequent derailments!

 

[YT-1300]

The piece of track is not level with the baseboard and wont be helping with any derailments or unwanted uncoupling.  Is the XPS flat?   As well as checking the track is flat, I'd check that XPS is flat too, use a long steel rule.

4 hours ago, n9 said:

Maybe I've been very unlucky then. My layout is 2x1m, has about 20 points, two double slips, two crossovers (all Electrofrog or Unifrog). Both crossovers are as I've described, as are both long crossings, which also both came with one dead rail in the diamond.

 

I think the frog bounce will be evident from any video out there showing stock running across Peco Code 55 points, especially 4 wheel stock. I think one of the Dawlish videos on here had an example with clay wagons bouncing. It wasn't specifically about this, just a lovely train running. If I find it again, I'll post it. But here's a picture of my Revolution tanker stopped at a frog, in this case on a diamond. Note the raised rear wheel on the right. In fact, if it's rolled lightly, it will come to an abrupt stop there as the front wheel falls into what is, in effect, a pot hole. But pretty much all frogs and flangeways on Code 55 are far too large for the stock I have.

 

 

 

That piece of track is not level with the baseboard and wont be helping with any derailments or unwanted uncoupling.  Is the XPS flat?   As well as checking the track is flat, I'd check that XPS is flat too, use a long steel rule.

 

I remember my friend had problems with wheel drop on Peco's O gauge points, he ended up laying plasticard strips in the frog to alleviate it - it was trial and error but worked successfully in the end.

 

If your Dapol Brit and 9F are having problems, the driving wheels need to have their back to back's checked, if they wont run well on Peco track, they'll run even worse on finescale trackwork.

 

A running video would be helpful

[009 micro modeller]

11 hours ago, Davexoc said:

kinematic couplings with too much spring force

 

I model in 009 (so the same track gauge as N, but in my case usually using code 80 Peco track). I don’t have a particularly large number of derailments, most relate to shunting accidents with small wagons, which can be put down to driver error or the light weight of some of the smallest wagons themselves. But, in common with a lot of 009 modellers, I don’t use the sprung Rapido-type couplings used in N (apart from on a few early pieces of rolling stock that can’t be easily converted), instead using various types of Bemo-derived loop couplings (they are mutually compatible, but not at all compatible with Rapido or Microtrains couplings). These 009 couplings aren’t sprung, which avoids that problem, but there are some other disadvantages compared to the types more usually used in N gauge, depending on what you want to do.

 

[RobinofLoxley]

That picture of the rocking tanker, is the diagonally opposite wheel in a hole or on flat rail at that point?

[shipbadger]

My N scale US exhibition layout has now done over 25 shows.  All the scenic section is code 55 track.  The fiddle yard is 'normal' Streamline, whatever that is, it was just cheaper than code 55 at the time.  Derailments usually have obvious reasons, things dropped on the track, careless elbow and so forth.  One thing which I notice in earlier postings is the mention of foam underlay.  Manufacturers for decades have produced moulded foam to use with their track products. Other people may use foam of the 'closed cell' type, like camping mat or floor underlay.  The first type of underlay does not produce a stable surface on which to lay track, it's main function seems to be to allow minor undulations in the baseboard to be to a greater or lesser extent negated when laying track.  I've never been convinced by 'floating track' arguement.  All my track is laid on cork which is sanded level before any track is laid.  In N I would suspect that there is no cushioning effect whatsover. 

 

Weighting of stock is something else to consider.  The NMRA publish guidance on suggested weight for rolling stock.  I also use a back to back gauge set to their standards.  It's always worth checking.  After problems with one loco some years ago and correspondence with various people, including the manufacturer it turned out the factory had been using the wrong gauge to set the wheels.  These things do happen.  With regards couplings, mine are all Microtrains as I've never found any of the compatable ones satisfactory.

Derailments will happen, the aim is to make them a rare event.  Each time it happens try and work out why.  Is it the same spot, the same vehicle or even the speed at which the train was travelling.  After a while you will slowly eliminate the problems, be able to sit back, relax and watch the trains go past.

 

Tony Comber

[34theletterbetweenB&D]

Part of the problem in assessment of 'what works, what causes problems' is that to add to all the factors mentioned there are the 'unknowable' effects of individual layout builder's capabilities. It's 'what works for you' that matters.

 

I am no great craftsman when it comes to layout structure, track laying etc. and put in a lot of time in determining what works for me, when resuming the hobby largely using Peco Streamline in OO, and a mix of RTR and kit built stock, all with metal wheels to something close to RP25.

 

Points, I found only the medium and large radius points were unconditionally reliable. Curved point, only reliable in trailing direction. All the rest unacceptable.

 

Track on running lines, minimum plain track radius of 30", with transition curves from tangent.

 

Couplings, all one brand, mixtures not fully reliable; and this only after careful height matching and mounting stability adjustements.

 

Adjustments to vehicle weights were occasionally required to make them all within 40% of the average for each vehicle type.

 

In the pursuit of being able to do with a full size train, whatever the real railway did - so for example I can reverse 60 4W wagons through any point network meeting the above criteria - fine and stable control is required, and DCC proved to be the way to achieve this for its smoothness.

 

Your recipe will vary!

[YT-1300]

4 minutes ago, 34theletterbetweenB&D said:

Part of the problem in assessment of 'what works, what causes problems' is that to add to all the factors mentioned there are the 'unknowable' effects of individual layout builder's capabilities. It's 'what works for you' that matters.

 

I am no great craftsman when it comes to layout structure, track laying etc. and put in a lot of time in determining what works for me, when resuming the hobby largely using Peco Streamline in OO, and a mix of RTR and kit built stock, all with metal wheels to something close to RP25.

 

Points, I found only the medium and large radius points were unconditionally reliable. Curved point, only reliable in trailing direction. All the rest unacceptable.

 

Track on running lines, minimum plain track radius of 30", with transition curves from tangent.

 

Couplings, all one brand, mixtures not fully reliable; and this only after careful height matching and mounting stability adjustements.

 

Adjustments to vehicle weights were occasionally required to make them all within 40% of the average for each vehicle type.

 

In the pursuit of being able to do with a full size train, whatever the real railway did - so for example I can reverse 60 4W wagons through any point network meeting the above criteria - fine and stable control is required, and DCC proved to be the way to achieve this for its smoothness.

 

Your recipe will vary!

I don't think I've had any unreliable pointwork, even though I alter every point I use (I replace all the moulded sleepering around the tie bar and replace with copper clad) and I usually modify the angle of the straight part of the point to suit my needs, I've never had a problem with derailments from doing this.  Actually now I think ok it, I did have a derailment at one point but this was due to me damaging one of the blades when I dropped a hammer on the layout.  Just had to bend the blade back to vertical and its worked fine ever since.

 

Re your comment about couplings, this is very important.  I use Kadee's on my HO (and OO) stock.  It's very important to have the same make, height and the same degree of movement on each and every coupling.

 

I spend time making sure my boards are flat, my track is flat, the b2b's and couplings are consistent.  Spending that time results in smooth, trouble free running.

[Right Away]

Not troubled with derailments as a rule as the main track (00) was laid several years ago on 3mm cork on 9mm plywood, but those that have occurred have been the following:

• Leading bogie wheel of certain steam locomotives have risen over rail head at a particular location where others (of the same class) are unaffected. This has been corrected by: wheel back to back adjustment / ensuring front cosmetic coupling does not foul bogie frame / ensure tender drawbar does not bind at the pivot which tends to keep the ensemble “in line” preventing the bogie from following the track / adjustment of vertical tension  of bogie - where possible. It’s all a bit trial and error.
• Some coach “close coupling” mechanisms have been found to bind and impede the swing of bogie pivot - check for flashing etc.

 

Edited December 25, 2023 by Right Away
correction

[Michael Hodgson]

12 hours ago, The Johnster said:

 jerks cause derailments.

 

 

Good description of the way some people operate !

[n9]

Thank you for all the replies!

 

Certainly it seems my question has been answered: derailments happen very few times, and usually with a specific item of stock, or singular location, or human error, or a coupling issue.

 

My derailments (so far!) happen only on double slips and long crossings. Clear suspects are now the driving wheels on my Brit and 9F. (They tend to derail on them 1 in 20 or 1 in 30 times.)

 

However, I do find it hard to separate reliable running across any point from the amount of rocking and jumping up and down caused by Peco's frog potholes. Here's a video showing one of the slips removed from the layout and placed on another flat piece of XPS with a couple of straights. My 03 first runs across it alone, showing the lateral slaloming (which happens with the Brit tender too, as well as stock) followed by the 03 pulling a random assortment of 4-wheelers from Farish, Revolution, and Peco that shows wagons rocking and jumping up and down quite alarmingly, at least to my view. (The 03 and Brit tender have wheels in gauge.)

 

 

 

Do your Peco Code 55 slips work this badly? Both of mine do this.

 

Perhaps with less swaying, I've found this effect is replicated on every Peco Code 55 point, crossing, and slip I have purchased as new.

 

Additionally, the speed of the 03 is as slow as it will go on this particular slip without losing continuity irrecoverably at one of the frogs. I suspect that this issue also has a lot to do with the potholes and slalom effect.

 

 

I can say that approximately 70% of my time and effort on the layout this last 18 months, has been spent investigating, correcting, or attempting to correct the problems I have encountered with Code 55. Not sure if that's expected, but it certainly feels like far too much.

 

 

 

 

8 hours ago, DCB said:

Something very wrong with that slip or crossing.   The frog is raised right?  Not the flangeway blocked.     Peco have produced some rubbish at times  they seem to do batches and some batches are atrocious and  the next batch are modified but still bear the same  part numbers.   I model in 00 , I have  gauge 1 fingers so can't cope with N ( I did try Once briefly) A few years ago  we bought 3 new Peco live frog 2ft radius points, for "Ugleigh" they were rubbish and I got 3 broken ones from Cheltenham Model Centre which suitably bodged replaced the useless new ones.

My 00 Dapol Mogul constantly derailed until I turned its leading wheels in the lathe so it might be rubbish track plus rubbish wheels.  But the points, slips, crossings should be flat so that has to be number one change.  Maybe a mate has some you can borrow?

For track testing I have a number of very fast locos and if they have wont go through my points very fast then I fiddle with them till they do.   It's usually a dog leg or something similar, but its very noticeable how much better older wheels are at staying on the rails than 21st century ones. 

 

Thank you for confirming that Peco can make mistakes! 🙂

 

 

7 hours ago, Harlequin said:

I hope other people’s videos don’t show frequent derailments!

 

I hope so too! 🙂

 

4 hours ago, YT-1300 said:

The piece of track is not level with the baseboard and wont be helping with any derailments or unwanted uncoupling.  Is the XPS flat?   As well as checking the track is flat, I'd check that XPS is flat too, use a long steel rule.

That piece of track is not level with the baseboard and wont be helping with any derailments or unwanted uncoupling.  Is the XPS flat?   As well as checking the track is flat, I'd check that XPS is flat too, use a long steel rule.

 

I remember my friend had problems with wheel drop on Peco's O gauge points, he ended up laying plasticard strips in the frog to alleviate it - it was trial and error but worked successfully in the end.

 

If your Dapol Brit and 9F are having problems, the driving wheels need to have their back to back's checked, if they wont run well on Peco track, they'll run even worse on finescale trackwork.

 

A running video would be helpful

It is level, although I can see why it might not look that way in the pic. The diamond is angled away from the camera to the right, and to its right there is also more underlay in the foreground for track I haven't laid yet. So an optical illusion. I have been trying out shims to counter the drops in the frogs. Do you know what height the plasticard should be?

 

3 hours ago, RobinofLoxley said:

That picture of the rocking tanker, is the diagonally opposite wheel in a hole or on flat rail at that point?

The opposite wheel is resting at the bottom of a frog pothole 🙂

 

3 hours ago, shipbadger said:

My N scale US exhibition layout has now done over 25 shows.  All the scenic section is code 55 track.  The fiddle yard is 'normal' Streamline, whatever that is, it was just cheaper than code 55 at the time.  Derailments usually have obvious reasons, things dropped on the track, careless elbow and so forth.  One thing which I notice in earlier postings is the mention of foam underlay.  Manufacturers for decades have produced moulded foam to use with their track products. Other people may use foam of the 'closed cell' type, like camping mat or floor underlay.  The first type of underlay does not produce a stable surface on which to lay track, it's main function seems to be to allow minor undulations in the baseboard to be to a greater or lesser extent negated when laying track.  I've never been convinced by 'floating track' arguement.  All my track is laid on cork which is sanded level before any track is laid.  In N I would suspect that there is no cushioning effect whatsover. 

 

Weighting of stock is something else to consider.  The NMRA publish guidance on suggested weight for rolling stock.  I also use a back to back gauge set to their standards.  It's always worth checking.  After problems with one loco some years ago and correspondence with various people, including the manufacturer it turned out the factory had been using the wrong gauge to set the wheels.  These things do happen.  With regards couplings, mine are all Microtrains as I've never found any of the compatable ones satisfactory.

Derailments will happen, the aim is to make them a rare event.  Each time it happens try and work out why.  Is it the same spot, the same vehicle or even the speed at which the train was travelling.  After a while you will slowly eliminate the problems, be able to sit back, relax and watch the trains go past.

 

Tony Comber

In my innocence I went with Woodland Scenics foam underlay for acoustic reasons. If I could go back I'd probably choose cork. I've found the flex in the foam is also it's big weakness and I've ended up replacing short sections with wood where strength was needed, e.g. to hold a smooth join on a curve.

 

3 hours ago, 34theletterbetweenB&D said:

Part of the problem in assessment of 'what works, what causes problems' is that to add to all the factors mentioned there are the 'unknowable' effects of individual layout builder's capabilities. It's 'what works for you' that matters.

 

I am no great craftsman when it comes to layout structure, track laying etc. and put in a lot of time in determining what works for me, when resuming the hobby largely using Peco Streamline in OO, and a mix of RTR and kit built stock, all with metal wheels to something close to RP25.

 

Points, I found only the medium and large radius points were unconditionally reliable. Curved point, only reliable in trailing direction. All the rest unacceptable.

 

Track on running lines, minimum plain track radius of 30", with transition curves from tangent.

 

Couplings, all one brand, mixtures not fully reliable; and this only after careful height matching and mounting stability adjustements.

 

Adjustments to vehicle weights were occasionally required to make them all within 40% of the average for each vehicle type.

 

In the pursuit of being able to do with a full size train, whatever the real railway did - so for example I can reverse 60 4W wagons through any point network meeting the above criteria - fine and stable control is required, and DCC proved to be the way to achieve this for its smoothness.

 

Your recipe will vary!

There's a lot I've learnt only after I started building and laying track. Wish I'd known everything that would be unacceptable to me a lot earlier! But at least I now know to test a lot more, a lot more thoroughly, and a lot earlier.

[AndrueC]

For most of my rolling stock hardly ever. If/when they do it's because of debris left on the track or me running them into incorrectly set turnouts.

 

However I do have experience of some rolling stock being more sensitive than others. Troublesome stock I've found so far:

• Dapol JNA Falcon Wagon - Refused to run on my first layout as they apparently didn't like 2nd radius curves. I blamed the couplers for not returning to neutral position as the curve ended.
• Dapol Spine Wagons - Unable to negotiate a slightly dodgy part of one of the inclines on my current layout. Not enough vertical travel in the bogeys. Also the fixed connecting rods between pairs of wagons which prevent horizontal rotation of one wagon with respect to another.
• Dapol 21t Hopper Wagons - These are okay but are a little bit sensitive to rough track. Just a bit too light and easily cured by adding some weight to them.

 

My layout uses code 80 track laid on Gaugemaster underlay apart from the turnouts which are laid on corrugated cardboard salvaged from parcels. My club's N scale layout is code 55 and it has no problems. Nor for the record do I for the vast majority of my stock.

 

I agree about the frog wobble - it's quite poor for short wheelbase stock. My 4-6-2's tender suffers it a bit and my 21t Hopper wagons also do. It's not enough to cause a derailment but doesn't look nice. Bogeyed stock doesn't suffer the problem.

Edited December 25, 2023 by AndrueC

[AndrueC]

14 hours ago, n9 said:

No, they are most certainly not flat. It's how they came out of the packet new, with two hills, one for each frog. I spent an inordinate amount of time, lifting them out, reinforcing the underlay (for better or worse, I chose foam on XPS) with wood instead of foam, and then nailing the little darlings flat. Still got the derailments. It's part of what made me question the sanity of continuing with Peco.

Something wrong there then. All my turnouts are flat. I'll add that I'm no perfectionist track layer either so I wouldn't say that N scale with code 80 is pernickety but I suppose code 55 would be more so by its nature.

 

I have always had diamond crossings on my layouts and aside from one of them causing shorts everything runs through them just fine.

Edited December 25, 2023 by AndrueC

[AndrueC]

Okay some pictures I've just taken. They use two wagons that I built from Peco kits. In all cases the frog is under the left, far wheel.

 

Sitting on an installed code 80 turnout:

You can see a bit of the cardboard that the turnout is mounted to. lol.

 

A slightly longer wheelbase:

 

The same again, this time parked on a Code 55 turnout that I bought as a future replacement but not currently being used:

 

 

And:

 

Both wagons can be made to fall into the frog by pressing on the corresponding corner (enough to grossly unbalance them) but left to their own device and/or when part of a rake them seem fair happy to roll across on three wheels.

Edited December 25, 2023 by AndrueC

[woodenhead]

To demonstrate that Peco track can operate well with crossings and points, I give you Little Aller Junction from our very own  @Chris M

 

 

I too have frog wobble but it's not derailments and really it's a feature in many scales unless you are building your own track to a particular standard and all your stock is to the same standard i.e. 2mm FS, or EM or P4.

 

One thing that can lead to derailments are the blades not closing sufficiently as that can mean it causes a wheel to jump on the closed side or the wheels will catch on the open side or even short.  I'm using IP Digital motors and have removed the springs so that they are firmly closed and then also wiring the frog for guaranteed electrical continuity.

[DCB]

It sounds like the slips are not flat, the frog is proud of the running rails which is maybe a manufacturing fault and the wheels are dropping into the "Frog Gap" which is a design fault.
The "Frog gap" appeared with the first Peco 00 track, which was "Universal" and could take both massive flange Triang or nearer scale  Hornby Dublo or Finescale wheels.  Prior to that track was designed with certain wheels in mind,  Hornby Dublo wheel flanges  run along the bottom of the frog / check rail gap keeping the wheel level as in a modern (US) flange bearing crossing.     Graham Farish used a swing nose crossing so there was no gap, it looked horrible but trains ran very smoothly over both types.

Bumping into the frog gap was something which folks sort of ignored, much 1960s rolling stock was sprung and or compensated and had bigger flanges.  The N gauge streamline is basically half size 00 so the feature or fault was continued.  To be honest only adopting a standard wheel profile for all you stock and shimming the flangeways can eliminate frog drop but it should be a minor irritant to a total PITA.

[AndrueC]

Here's a video from my first layout. About half way through after the train has gone round a 180 degree bend you will see it crossing a diamond. The tender wobbles quite alarmingly but the train keeps going.

 

[n9]

Definitely those are lovely layouts in the vids, no doubt about it, but I think it will forever evade me how that rallycross effect has somehow become accepted, or how in my video a loco nose- or tail-end swing with an amplitude of roughly 0.5cm doesn't appear to raise too many eyebrows in 9mm scale. But fair enough, perhaps I'm the odd one out. Your replies have been very helpful and informative regardless. Thank you.

[Michael Hodgson]

I was under the impression the problem was on plain track. 

 

Pointwork can certainly be the cause of problems, and I don't like the running of any of the vehicles through that slip, so I'm less inclined to suspect them. 

Slips seem to be disliked on the prototype, so they tend not to be used on running lines (except for single slips passed in the triling direction).  The back to backs of the point check rails may be to blame, and there's not a lot you can do about that. Could be unsupported wheels dropping into the "pot holes" at crossings.  I don't do N gauge and don't know what is usual with these slips. 

 

The worst slip I've come across in OO was by Joueff or Playcraft (can't remember but I blame the French) - and its problem was really that the radius was far too tight (tighter than radius 1).  Even so, it's OK as long as it's used in a yard and only with 4-wheel wagons and 0-4-0 tanks.

[TheSignalEngineer]

18 hours ago, The Johnster said:

Check that your slips are not distorted, even slightly, by laying them on a mirror, firstly right way up to see that the sleeper base is sitting flat, then upside down to check that all the railheads are level with each other.

The last frequent derailment I had was on a Peco 00 Code 75 medium point. Several Hornby coach bogies  particularly Maunsells didn't like going through it in the facing direction. It had gone hog backed near the frog and certain types of wheel flanges were  carching on the nose. Once it had been levelled it was OK.

Previous problems included certain types of couplings, particularly Hornby coaches, didn't like to straighten up after a curve or turnout, loco pony trucks being too light or stiff to respond to curves and perpetual b2b problems with RTR stock. Because of the latter all wheels are now checked and cleaned on arrival.

 

 

[woodenhead]

1 hour ago, n9 said:

Definitely those are lovely layouts in the vids, no doubt about it, but I think it will forever evade me how that rallycross effect has somehow become accepted, or how in my video a loco nose- or tail-end swing with an amplitude of roughly 0.5cm doesn't appear to raise too many eyebrows in 9mm scale. But fair enough, perhaps I'm the odd one out. Your replies have been very helpful and informative regardless. Thank you.

The thing is we accept that if you go RTR we expect some compromise.

 

The answer is there and it’s to move to an adopted standard, a starting point is probably Wayne’s British Finescale points and track and see if that fixes your issue.

 

Beyond that 2mm FS is the next step unless you want to go to EM/P4

[n9]

2 hours ago, Michael Hodgson said:

 I don't like the running of any of the vehicles through that slip

You know I was expecting everyone to say this! And yes, I suspect the unsupported wheels aren't entirely innocent.

 

1 hour ago, woodenhead said:

The thing is we accept that if you go RTR we expect some compromise.

 

The answer is there and it’s to move to an adopted standard, a starting point is probably Wayne’s British Finescale points and track and see if that fixes your issue.

 

Beyond that 2mm FS is the next step unless you want to go to EM/P4

Hmm, given what's on view I think we'll have to respectfully differ on what the word compromise means 🙂. I do wonder though how all this "accepted" bouncing compares with pointwork from other manufacturers, Arnold, Walthers, Kato, Fleischmann, etc.

 

And I agree, my options are either to lump it, or remove the worst offending pieces, or jump ship.

 

[Michael Hodgson]

If the fault is indeed unsupported wheels, it means the flanges are not as deep as the "hole".  If you put a thin shim into that void in the frog it may help as the flange can run on the shim.  The likely downside is that other wheels on other stock might have deeper flanges, and if so their flanges will be lifted so that the normal part of the wheel is lifted out of contact - that's why the fine scale guys say standardise on a given wheel profile.  It's a problem in OO with the "steamroller wheels" of early Triang stock.  But it's probably worth experimenting to see whether you can improve running - it may be that re-wheeling a few troublesome vehicles may help.  Sometimes it's easier just to flog off the worsrt offenders on ebay.

[RobinofLoxley]

That picture of the rocking tanker, is the diagonally opposite wheel in a hole or on flat rail at that point?

 

The opposite wheel is resting at the bottom of a frog pothole 🙂

 

Right. This can only happen when one end of the model is heavier than the other. It will be inevitable sometimes with asymmetry built in but it needs balancing. Needless to say 4 wheeled creatures will all be susceptible. Not sure exactly what to do to correct but im thinking small weights near the centre..

[Harlequin]

1 hour ago, n9 said:

You know I was expecting everyone to say this! And yes, I suspect the unsupported wheels aren't entirely innocent.

 

Hmm, given what's on view I think we'll have to respectfully differ on what the word compromise means 🙂. I do wonder though how all this "accepted" bouncing compares with pointwork from other manufacturers, Arnold, Walthers, Kato, Fleischmann, etc.

 

And I agree, my options are either to lump it, or remove the worst offending pieces, or jump ship.

 

 

Yes, it's interesting that this appears to be the normal, accepted behaviour in N gauge. It's presumably a result of the standard RTR wheel profiles and the tolerance required in the flangeway widths to allow RTR stock to run straight out of the box. @Martin Wynne is the trackwork expert and he should be able to say more about all this and what your options are.

 

If you've got the time, money and patience to do the comparative tests of Peco against the other manufacturers you mentioned that would be very interesting.

 

One more thought: You could post about your disillusionment with standard 2mm pointwork in the 2mm Finescale forum. Those guys will understand your problem better than us in the general community, who are mostly 4mm modellers. They should also be able to offer you more options based on experience.

 

[AndrueC]

21 minutes ago, Harlequin said:

Yes, it's interesting that this appears to be the normal, accepted behaviour in N gauge. It's presumably a result of the standard RTR wheel profiles and the tolerance required in the flangeway widths to allow RTR stock to run straight out of the box. @Martin Wynne is the trackwork expert and he should be able to say more about all this and what your options are.

I'll take a look at my coal train (13 21t hoppers) tomorrow but I don't think they wobble very much. That may be because they are evenly balanced front to back so are pretty happy to balance on three wheels for a fraction of a second as one wheel crosses the frog. It's also worth noting that when testing my track by rolling a single wagon or a disconnected bogey across a turnout derailments are common. So whilst that confirms there is a problem it also (in my experience) says that it might be irrelevant. Group a collection of troublesome wagons into a rake and they run fine.

 

It's also worth reiterating that in my experience this only effects single axle rolling stock. Most of my stock is modern era and thus has bogeys and is immune to the problem. You can even see on my video that the tender is the only thing that wobbles - the coaches and loco don't.

Edited December 25, 2023 by AndrueC