derailments with b-train shorties

[EF57]

I notice that when derailing through switches (the notoriously untrustworthy nr. 4’s), a shorty’s first truck often passes through correctly but the trailing truck doesn’t, either trying to take the other route or derailing at the frog.  At other times they pass through flawlessly.  This holds for both powered cars and unpowered.  Speed seems to make no difference.   It doesn’t seem to be due to twist applied by the couplers, they are just the normal Arnolds on Bandai power units or Kato trucks.  Does anybody have this problem as well?

[roadstar_na6]

Try putting as much weight as possible in these cars, maybe that already helps

[Andrew Nummelin]

With more than one vehicle showing problems it is more likely to be a track fault.

1. Are there any bits of rail that are not aligned well? A small horizontal error can catch a flange and cause it to climb.

2. Are the switch blades held tightly against the stock rail as a vehicle passes over? This may not be easy to see.

3.  Is the track gauge correct all the way?  Any bits that are tight, especially on a sharp curve, can cause flange climbing. On a sharp curve some gauge widening may be needed.

 

Potential problems with the vehicles include 

1. Restriction to bogie rotation.

2. Incorrect back to back of the wheels

3. Couplings fouling the rails ( this can be difficult to spot as I know from personal experience).

 

Weighting may help but that only disguises the problem, it does not solve it.

 

Good luck!

[lukewang01]

It only happens to me when the traction tire is up front at right turnout. It seems like the wheel flange would get caught at the frog going the other direction. But I rarely encounter any problems with non powered cars.

[Andrew Nummelin]

Not specific to this problem, but there are many excellent bits of advice that are now on the Missenden Modellers web site.  The Trouble shooting page is particularly well worth looking at.

 

(The residential session planned for this weekend was of course cancelled, but there is a large on-line event being held instead so much advice made available to a wide audience.  

https://www.missendenrailwaymodellers.org.uk/index.php/virtual-missenden-autumn-2020/

 

My only connection is as an attendee at many past events.)

[EF57]

Thank you for that useful typology of (well-known) possible trouble sources. The only one possibly relevant here is the blade-stock rail gap, a known problem with these switches.   But I guard against that.  My question is, why should 2-3 cars pass through perfectly well and only then one derail—as mentioned, it can be powered or not—and then it’s always the trailing truck, the first having passed through OK?  That seems of theoretical interest to me.  Maybe a torque-effect of the following coupling? 

[EF57]

Spoiler

 

It’s the metaphysics of model railroading—today I ran all the trains through all the switches for a half an hour— not a single derailment!

[Kamome]

Do you tend to get more issue with the points that are joined to a curved track? I found many of my shinkansens picked the points on number 4s more often when placed next to a curved track. Using a 62mm straight before the point alleviated a lot of these issues. I eventually “tuned” my #4s by filing down the rail slightly where the blade makes contact with the stock rail. 

[cteno4]

Regular Shinkansens also don’t like #6 points right at curves as well even the longer radius Kato double viaduct. Spacers always helped fix this.
 

while the regular shinkansens tend to have issues being more inflexible in movement due to their couplers and sometimes diaphragm mechs, I think b trains tend to fall victim of the other end of the spectrum where things are very flexible and bouncing around a lot and even accordioning long wise some on coupler springs and thus can bump into point and even track joints at times that can cause random derailments. Running btrains on the old club sectional layout they were much more prone to find bad joints and such than regular trains were.

 

jeff

[defor]

I'm going to chime in and say that I experienced exactly the same issues with b-train on #4- the layout I was working on for my desk shelf at work ended up having major issues because the koki were so light- in the end, I started adding lead weights (bought a roll of 1mm lead off amazon-cut it to size and stack) to both the engines and the insides of the containers...

Still was never getting the reliability I was hoping for... Might look at revisiting this down the road, although maybe this time with tomix, even though it'll need some tweaks to fit the same general size...

 

#4's seemed particularly bouncy, owing to a few factors:

1. frogs don't sit consistently flat from factory
2. the switch points on a #4 are already well known to cause derails when wheel flanges spread the meeting point of the point and an outer rail
3. spacing between the wheels on b-train axles seems inconsistent
4. generally speaking, the trucks pivot a little moody, especially without sufficient weight on them.

 

All items are fixable, but I think if 1 and 2 are too complicated for you, the easiest fix is making sure not to put #4's right after curves, give at least 2 car lengths (in b-train) before going into a switch seems reliable(that said, you'll still want to do 3 & 4 (which are definitely doable without modifying the track)

Edited October 23, 2020 by defor