Backing/Shoving Long Trains

[K487]

Subject: Backing a 69-car train around a loop with 16" radius curves.

Today I managed to run a long train backwards on a track loop with 16" radius curves (measured center-of-track to center-of-track), and I thought you might be interested in some of the details.

I have had my HO layout (this is my second) for 18 years.

I have 3 major loops, L-shaped, basically like a right angle dogbone.  I run only DC, my cars all have KD couplers, are a maximum of scale 52' long (most are 40' and less), and of the total of 204 cars on these 3 trains there are about 10 different manufacturers represented.  Eighty five percent of the railcars have plastic wheels, and the rest have metal wheels.

The track is all Atlas NS 100 flex (all joints soldered; no exceptions).  There are 9 Atlas crossing diamonds of various angles, 23 20-year old Model Power #4 turnouts, and 1 Model Power curve-on-curve turnout on the layout.

Each train is currently pulled by a pair of diesels: Loop 1 (outer) 2 Atlas Trainman RS32s; Loop 2 (middle) 2 Bachmann GP30s; and Loop 3 (inner) 2 Atlas Trainman RS32s. 

Loop 1 (22" radius) train has 65 cars.  Loop 2 (19" radius) has 70 cars.  Loop 3 (16" radius) has 69 cars (composed of seventeen 52' cars, and the rest are shorter.)

All loops (total of 4 – the fourth is smaller, 80% hidden, and an ore unit train of 33 cars runs on it) are each powered by their own MRC Tech 2 Railmaster 2400 power pack.  The switch engine and remote control turnouts are powered by a fifth MRC Railmaster 2400.

Today I was running trains on Loops 1 and 2, and decided to run the train on Loop 3 (16" radius curves.)  I had the trains on Loops 1 and 2 running backwards, so on a whim I decided to try and run the Loop 3 train backwards.  I had tried this a few months ago and a car derailed fairly quickly, so I've just run it forward since then.  However, I did one thing a number of weeks ago: I took 3 50' light-weight tank cars from the first half of the train and put them in the back half - about 15 car lengths in front of the caboose.

While Trains 1 and 2 were running backwards for the first time ever, I ran Train 3 backwards - 20 times non-stop around its loop.  It takes Train 3 three minutes and twenty seconds to make it around the loop, so I ran these three trains backwards continually for 66 minutes, and did not have one single derailment on any train.  The only noticeable thing that happened was that about 5 box car bodies on Train 3 leaned/tilted outward on parts of the 16" radius curves, but the wheels stayed on the rails.

As a reminder all of my railcars, no matter the length, are weight-targeted at 2.75 oz. per car; I think they currently average 3 to 3.5 oz.  I also do not follow another NMRA practice – that of keeping one truck on a railcar "snug" (to keep the railcar from wobbling) and the other loose.  Both of my railcars' trucks, like the prototypes, must have (within limits) horizontal and vertical freedoms.

The MRC power pack surface for Train 3 (16" radius curves) ran a little warmer than the other two.  That makes sense – 16" radius curves create more resistance/friction/drag than the other two larger radius curves.  And it could be that the tighter the radius gets that the friction/drag rises exponentially and not linearly.

By the way, all my Atlas Trainman RS32s, GP38-2s, and Bachmann GP30s, 35s, 38-2s, 40s and FA units, operate on these 16" radius curves with no modifications.  Haven't tried the Bachmann Alco RS3 on it yet.  Do I even try to run my Bachmann Berks and SD40-2s on it?  Nooooo. 

As info I don't have any other engines except a couple of AHM? 0-4-0s that my son and I used to use as slot cars on a previous layout when he was about 8 years old; he's 36 now.  While we were racing locos (double track main lines) I used to quietly throw a remote control track turnout in front of his engine which then said engine would attempt the curved route, fly off the track, and roll and bounce in fascinating ways.  For the first few times I did this his expressions were priceless – including when I showed him how I was doing it, but then he did it to me and we had finger fights over the push buttons.  I still chuckle every time I think about it.   No, he's not into model railroading, and no I don't think these experiences "scarred him for life." 

Any comments or questions, fire away.

K487

[jward]

i think the reason you are able to back that train is due to three very important factors. first, the cars are weighted evenly. and from my experience both in model railroading and on the real ones it is the light weight cars which pop out of the train. second, those atlas rs32s you are using are super smooth running locomotives. this helps keep the forces in the train even and lessens derailments under any circumstances. third, you are backing them slooooowly. even so you have some cars leaning which means they want to derail. a little more speed, or a jerk in the train due to dirty track and they would be off the rails.

[K487]

Jeffery:

Thank you for your comments.  Let me respond to them.  As info I have previously added about 2 ounces of weight to each loco for better traction.

I sure agree with you on car weights that are all close to the same.  It helps.

Atlas engines do indeed run smooth, but my two Bachmann Gp30s run equally smoothly when pulling/pushing such a long/heavy train.

You and others might find the following interesting.  Your last comment about backing them slooowly is right, so you got me curious and I ran Train 3 on Loop 3 (16" radius) faster backwards.  I used the two Atlas locos and then used the two Bachmann GP35s.  I ran the train backwards two times around the loop twice as fast (1 minute 40 seconds per loop vs. the slooow time of 3 minutes 20 seconds.)  I then ran the train backwards even faster three times around its loop at 1 minute 15 seconds per loop.  The power pack control knob was then at about 50mph.  Max speed on the dial is 100 mph.

The five box car bodies still leaned out, but zero derailments.

K487