Derailed coal cars in curve.

[userjh5174]

Hi everyone,

                    I run a HO scale coal train with 50 cars on a 24 deg radius curve track with no problem; however, I just added 10 more coal cars to my train and when ever I go around the curve or start to pull from a stop in the curve, the first 5 or more cars will just flip over. any solutions?

[jeffrey-wimberly]

Add weight to those cars.

[selector]

The phenomenon you have encountered happens in the real world of trains as well, and is commonly known as 'stringlining'. In fact, if there has been a serious miscalculation and a very heavy trailing tonnage is still moving under the forward strain of enough engines, and if the weakest knuckle in the whole consist doesn't part company with its shank, the strain on the inner rail along the curve may be so great that it actually pulls it outward with the flanges pressing against it, or it'll flip onto its side.

For our models, Jeff has one answer, although more generally you could say place your heaviest cars forward, at the head of the consist and just behind the engine.  If you have a string of lighter hoppers and then three or four substantially heavier items of rolling stock dragging the tail, the heavy tail and the struggling front end will conspire to lift the middle up so that they'll straighten, which is that the towing vector wants to do...make a line showing the shortest distance between the two anchoring points.

Adding weight into cars already being trailed, more than the extra ten hoppers, places a greater strain on the motive power.  if you have tight curves and any grades you may find the locomotive(s) stalling and spinning in place, or yet more stringlining. Widening curves alleviates some of the problem, but as Jeff suggests, placing more weight closer to the front should help.

Crandell 

[tomikawaTT]

You might want to take the time to check each car individually for:

1. Weight - NMRA Recommended Practice calls for one ounce plus an additional 1/2 ounce per inch of length.  I discovered the hard way that one popular brand of HO hoppers is grossly underweight.
2. Rolling resistance.  I had some cars that would barely roll on a 2% grade before adjustment, and have others that will roll away from a harsh glance on supposedly level track.  The object is to make them as free-rolling as possible.  A truck tuning tool will help the ones that aren't simply suffering from congealed lubricant.  The worst might require new wheel sets or new trucks.
3. Clean wheels.  A layer of grunge on the tread is just like a low tire.  It drags against the rails and increases the pull needed to move it.  It also decreases the effective flange depth.

Then, if you're running that hopper train as a unit, rank your cars from the most free rolling to the most sluggish - and position the hard haulers closest to the loco.

If your car wheels accumulate crud, it would be a good idea to establish a cleaning interval rather than wait until the thickness exceeds flange depth.  That, too, will increase the frequency of derailment problems.

Chuck (Modeling Central Japan in September, 1964)

[Anonymous]

it is not the lack of weight but the roleling resistance that causes a process called string lineing. they want to be a straight line on a curve. weight only helps when they have a good set of truchs. cleaning your wheels and good lube is a best bet. rmr

[Shamus McWeasel]

You have hit that magic place where the inherent drag of the rest of the consist has become significant enough for it to engage in a tug-of-war.  The opposing forces are attempting to lessen the strain by pulling across the curve - those 5 cars are a result of the struggle.  I agree - try adding weight to the cars affected, and see if it solves the problem.  Final thought - you should not need as much weight the further from the engine you go, and you might want to add fractional weight to the next car or two down the line as well...

[ironmillwright]

I'm very new to the whole forum thing here, and agree with all responses. One other Idea, is taken from real-life situations. Adding another engine mid-consist or even at the end of the train is something I've wanted to try for a long time. My fears of doing this have to do with poor couplers. USMR horn-hook types notoriously uncouple when a force pushes them together. I have so many to replace with knuckles, it makes me shudder. If your 'helper' engine has a lower speed and and can be outrun by the head engine, I think it would work. another criteria for this working well is a clean track and clean pick-up points throughout. Note: I'm coming from a DC perspective. I understand DCC engines can be fine tuned to do exactly what you want them to. Good luck. 

[userjh5174]

I have found that adding Dpu (distributed power) in the middle of my train has solved the "Trainlining" effect : cars pulled off track and derailed. the DPU provides less stress on my train and track by decreasing the tug of war of the locomotives pulling against a heavy train in a curve.

I can now run over 70 coal cars with no problems around the curve and on a 1.5% grade with 3 locomotive. This setup is done with hook-horn couplers and DC only as an experiment to see how big my train can get.

My Athearn Sd-40-2 and my 30 year old Bachmann Gp-40's have also had their weight increased by over two times the amount for increased tractive effort.

 

[ironmillwright]

Good to hear that it works, userjh5174. I oversimplified the horn-hook thing. Incorrect and incompatible height between the cars' couplers has a lot to do with it, too. I ran about a 70 car consist behind a 3 GP-38 plus a GP-40-2 four engine lash-up, but could not stop on a curve - it would yank 'em off the track when initial power was applied to restart, no matter how gingerly it was done. 

I'm gonna try it.