Transformer Tales

An edit to paragraph “A train traveling on track 2, engine crosses from track 2 to 1 without incident,...”

There are no subsequent sparks. Track 2 is now deenergized, cars are derailed before they cross to track 1 and are dragged in such a way they do not short track 1.

We used to do these problems all the time in math class. An O gauge model freight train with a single engineer was traveling west at a simulated 45 MPH. A O gauge model passenger train with the engineer's girlfriend was traveling east at a simulated 60 MPH. How long until the sparks fly?

For anyone who does not tune in daily, the previous postings are at https://cr4.globalspec.com/comment/1319509/Re-TVS-Diode-really-required.

Previously the discussions were around three subtopics:

1. TVS diode: very useful for over voltage (sparks) suppression but nothing more.
2. Circuit breaker: useless for the over voltage conditions you will have on your train but very useful to open up (turn off) a circuit when a short is caused by a derailed train.
3. Solid state detection circuit: a very fast way to detect a fault and open the circuit but it is a little more complex than the other options.

You want to detect a fault and have any single fault trip all circuits open. This is basically a slightly more complex version of one of the option #3 suggestions. Most of the option #3 suggestions did (or could) have fault detection and circuit interruption as separate parts of the circuit. The circuits need to be designed such that any one tripped fault will open all circuits. If you have traditional logic then this would be an "OR" gate. The actual circuitry would influence how the "OR" is done.

You said “You want to detect a fault and have any single fault trip all circuits open.” This is correct and well restated.

See #6. My sticky part is, can this be configured to differentiate a fault trip from an operational power interruption?

Main power is fed by relay energized by transformer, transformer loses power, relay disconnects, main power off...Relay has manual momentary button to initially energize circuit...

This to bypass relay cut-out and start circuit...

This to adjust control voltage for relays...

And a couple of fan relays...

Good suggestion, but this sort of solution has already been considered and rejected:

1) Transformer is constantly changing, some of these changes include momentary off to change state of the RU.

2) There are also instances where only one train is running, other tracks are powered down.

Either case above precludes the protection scheme suggested.

You could add a UPS power supply, that would differentiate between short and power out...

...and for one track operation you could have a switch that ran the "off" track through the NC contacts on the fan relay...you could have a separate control transformer that was manually operated...and switched for either track or both...this then controlled with a voltage sensing circuit switch so that as long as there was some voltage output, the power would continue to be supplied...

Not following you here.

It is required that the track be zero volt for about a second to cycle the reversing unit.

Just add a delay on break relay in the control circuit...

How about something like a 2 pole circuit breaker? Short in either line disconnects both lines.

Shunt trip breakers may also be workable, but I haven’t figured out how.

https://www.outbackpower.com/downloads/documents/integration_products/system_accessories/Ground_Fault_Detector_Interrupter_installation_instructions.pdf

This is actually a maintenance issue. The objective is to attend to all cases of <...dented wheel flange...> so that a <...derail...> does not occur.

After all, that's what happens on the prototype.

Here at the ‘Road To Success Railway’ we strive for 100% trouble free rolling stock, power units, and ways.

However, stuff happens.

Once had an unfortunate trespasser (spider) get himself caught in a set of points, this prevented both points from properly aligning but was close enough to allow three or four cars to pass before one car with wheel spacing at the high end of tolerance for gauge jumped the track at points.

We have improved security fencing to prevent similar events in the future.

One must always make sure that the back-to-back of the wheelset flanges exceeds the face-to-face dimension between the vertical face of the wing rail and the vertical face of the check rail, and that the front-to-back on the wheelset is compatible with the front-to-back between the check rail and the point and splice rails.

One must also look out for bogie rotational stiffness.

If you get one of these spiders,leave it alone.It will transmit a signal back home for help,and a spider invasion will ensue.

https://www.dailymail.co.uk/sciencetech/article-2531107/Mystery-Amazon-solved-Miniature-towers-surrounded-picket-fences-trees-work-SPIDERS.html

That looks like a miniature AN/FLR-9.

Are the wheels on the trains tapered,like on real trains?The taper helps keep the wheels centered and allows for differential speed of the wheels on curves.

Yes, the model wheels are very similar to 1:1 prototypes (1:1 = 1 to 1 scale, real world train). A few wheel geometry changes do exist, in part to accommodate the fact that 1:1 equipment weighing as much as 400,000 pounds simply does not work just like a 1:48 model weighing in at about 10 or 12 ounces.

Another wheel/track thing is, different track manufactures use different shapes of rails. Most of what I use is the older (but still very common) round rails, generally called tubular track. One mfgr. use a solid rail that is quite closely scaled to 132 pound (65.5 kg/m) 1:1 flat bottom rail, another uses a hollow rectangle tube (sort of a compromise in between the other two). A wheel designed with heel and flange specific for 1:48 tubular rails will hunt and oscillate on the 1:48 prototype solid rails, particularly on straight stretches. So, most O scale rolling stock uses a somewhat middle-of-the-road, kind of close, works pretty okay most of the time wheel geometry to operate acceptably on different track designs.

Even in the 1:48 universe, compromises are common.

Knowing nothing about this,why not use double flanges on wheels?I am sure there is a reason for this,but I don't know why not.

A good question. Flanges on both inside and outside cause troubles on curves. Wheels are set on axles, these axles are paired (tripled in heavyweight passenger cars) in truck assemblies, these rigidly holding the 4 wheel in a rectangle, two trucks on a car, pivoting. Flanges inside and out tend to grind away the outside flanges.

Noteworthy here are a specialty type of wheels with extended flanges. These use a more specialized track to accommodate these longer flanges, this setup is generally used in models running outside where insects, twigs, Popsicle sticks, etc. are more likely to be encountered. This is usually only found on so called Garden trains, these at varying scales usually around 1:20 or so. These wheels also wear out faster, so not commonly used on average toy train sets.

Derails are not the only source of track shorts, but are a common one. Cars are fitted with metal grab irons, handrails, brake wheels, exhaust stacks... these can vibrate loose and fall off, shorting the track. Track itself has an occasional issue with isolation strips at the center rails.

How about magnetic wheels,or magnets embedded in the wheels to help stability?

One large manufacturer supplied locomotives with magnet wheels, marketed as ‘Magna-Traction’. This helped a little, but has a tendency to pick up the bits of handrails fallen from cars already mentioned.

Discontinued after three or four years. No others (that I know of) have offered magnet wheels, prolly due to the issue of scrap metal collection.

Here is a good video on the shape of train wheels https://www.youtube.com/watch?v=XzgryPhtc1Y.

What an interesting thread for us all, I am fascinated and ready to be shot down for my ideas!

If the mains to BOTH transformers is taken from a single wall socket, and it passes through new power relay contacts between wall socket and the transformer, and if a "shorted" signal can be used to drop that relay, till it is reset by operator, that would work for the single line.

All you need for tracks one and two, is to add for the second line, is a further relay in the same power line to both transformers, but either before or after the first mains relay in the main power, in series so to say, so if either track sees a short circuit signal, power to BOTH transformers is dropped by either of the two relays.

I hope that makes sense to you, but if not I could make a small drawing/schematic, if neded.

I see myself that a similar method could be used in the power AFTER the transformers, but this would leave the transformers powered on, which is why my suggestion is to break the mains power BEFORE both transformers.

Andy, that is a very interesting idea. GA vote from me.

I’ll cogitate on this a while. I can see no real downside to the suggestion.

At some point here we need a schematic so everyone is on the same page and final hashing out can begin...

On O gauge in the UK, it is commonplace for a train to transfer from one controller to another by inserting an isolating fishplate in the rails, set both controllers to the same speed setting, and simply drive from one controller's zone onto the other.

Same on this side of the pond.

This is why you should have a true rms voltmeter on each track, this helps to prevent those jackrabbit runaways when an engine crosses to another track.

It is my understanding that OO (double O) scale is quite popular in the UK. Is this not so?

As an aside, I run one UK style engine and passenger car set, modeled after the Olton Hall.

It is so. However it is a compromise that dates back to the 1930s, when the German toy-maker Bing introduced small scale trains into the UK. The prevailing scale in Continental Europe was, and remains, HO, or "half O gauge", at 16.5mm track gauge and 1:87 scale prototypes [3.5mm:1ft], much as in the Americas. However, because the prototype in Europe is somewhat taller and a bit wider than in the UK, it was found that the available continental mechanisms would not fit UK locomotive bodies built to that scale. A good-old British compromise, the origin of which is attributed to one Henry Greenly, kept the 3.5mm:1ft mechanisms though increased the scale of the superstructures to 1:76.4, or 4mm:1ft, to fit them, giving a gauge/scale mismatch. 4mm:1ft is very easy for the finescale modeller to work with (1mm is equivalent to 3in - one can do it without tables of dimensions) and is supported today by a vast array of mainstream, specialist and aftermarket suppliers.

Any of the books written by Edward Beal either side of WW2 will give an insight into the gauge/scale conundrum.

From 1955 or so there was the beginning of a movement intended to rid models of the scale/gauge/appearance compromise prevailing in OO at 4mm:1ft. It resulted in a widening of the track gauge to 18mm, and later 18.2mm on finescale wheels, which is called EM Gauge, and to 18.83mm track gauge on true-to-scale wheels, which is called S4 or "Scalefour". The movement is founded on the track and wheels being the foundations of a scale model and just as important a part of it as the vehicles thereon.

There are now two specialist societies catering for the wider gauges in 4mm scale, both aimed at reducing compromise in scale models; one of them has well over 2000 members predominantly in the UK though they are found in other countries too. Though they have different outlooks there are close links between the two organisations and many individuals subscribe to both.

https://emgs.org/

The Scalefour Society

Pendon Museum, bringing the past to life - Abingdon, Oxfordshire

This is quite interesting, thank you very much for sharing.

This exhibits a large part of my interest in the hobby, histories of the hobby itself, histories of manufacturers, consumer demands and manufacturers responses to those, and histories of the 1:1 trains and their (sometimes nefarious) owners and directors and the various schemes and strategies used to ever increase their rail empires...

This may be a surprise to some, but for each of these diverse enterprises, it was always about the money.

Your comment regarding the S4 modelers is particularly interesting.

In the O scale, some US modelers use HiRail options, with closer to scale couplers, trucks and wheels. This gives a closer to true scale layout.

HiRail Wiki article.

Amazing, some of the effort put into some of these toy train layouts, absolutely amazing.

Indeed. There is a similar movement in the UK, named "Scaleseven". A long-term friend of this user subscribes to it and is making pioneering developments.

This group (S7) is quite interesting.

Thanks to you for sharing, this scale is yet another facet of the train hobby gem I had not an inkling even existed.