Thursday, June 2, 2022

Monk Subdivision - Taming the Monster (Grade)

Oh my! Imagine my surprise Wednesday evening when Jérôme spiked a few stretch on track on the main line and requested we test a few locos. Everything looked so great and I didn't see the need for a test, but I knew he wouldn't leave me alone if some locos wouldn't climb the grade with rolling stock in tow... A Bachman GP9 was put on the rails to pull one 40 express baggage boxcar and eight heavyweight coaches... it started well, but once half the train entered the first curve, the speed decreased dramatically until some wheel slippage happened. It wasn't a nice sight... at all. But hey, I blamed it on cheap Bachmann motor.

A Bachmann 4-6-2 struggling to exit the staging yard

Then, it was a Proto GP9... it climbed the hill, slightly slowed down but performed quite well! Hurray, it was just because of a crappy loco. Then the Proto F3, a brick of metal, had serious slow down... but the C-Liner performed OK... Bachmann Light Pacific stalled and slipped entering the first curve and the IHC Mogul was even worse... unable to pull a 4 cars train. Something was happening... locomotives didn't perform well, except heavy diesels which required multiple units. I started to panic to be honest as I'm accustomed to flat layouts with no serious pulling issues. Trevor Marshall's warning against grade and Lance Mindheim poor opinion of them were ringing in my head... Did I made a mistake? Jérôme didn't care that much about that. It wasn't an issue for him, but an opportunity to run locomotives for "real" by controlling the throttle. I knew he was right, but it didn't appeased my fear at all!

The next evening, after a day of doubts, I went downstairs and performed a few other tests to try to understand. I knew I didn't take into account how curves affected my maximum 1.6% grade, transforming it in a 2.7% grade. And I knew my 2.1%, not yet built, would go over 3%. Steam locomotives are finicky and whimsical, it was a disaster that could trash my dream to run the 1950s. I had to test the other locomotives, many of which had poor reviews online when running on 2% grades.

I started with a good old friend, a Bachmann Spectrum 2-8-0 weighing a lot. It ran perfectly and climbed the grade with very little effort, pulling the heavy train... I had a sigh of relief since I absolutely needed that locomotive to perform well. Then, I tried a Spectrum 2-10-2 which generally is considered light and underpowered. It was going to be another disaster yet, it performed quite well, with a little bit more of speed reduction than the Consolidation. It was a good sign since I need this loco to pull long trains.

Then came a Bachmann Chinese 2-10-2 QJ. Performance was average at best because the loco was a little bit too light. With maybe 2 oz, it would be a great puller... but it didn't matter too much. Finally, I tried a BLI Mikado. Once again, performance was relatively satisfying. I feel this loco could benefit a little bit more weight, but it should be fine pulling a 10-car freight train. These results made my day as they proved a good chunk of the fleet was fit to purpose, albeit with some extra tuning.

However, it was clear I would have to rework the grades and make the vertical transition somewhere else than the curve in the yard. At 1% grade + a .0.9% curve factor, it was a 2% grade that was too much... But more on that in a later post.

After the test, I was curious to know what was the pulling power of real similar CNR locomotives. As you may know, there aren't any reliable formulas to equate tractive effort to tons pulled by a locomotive. However, I found a rule of thumb by Al Kurg explained by someone nicknamed Akarmani on MRH forums. The rule isn't that reliable, but he discovered it overlapped several data obtained by different means. I wasn't finicky about it, just wanting an average number, something in the ballpark to see if the model locomotives were completely bogus or close to their real counterpart.

Here's an excerpt of Akarmani's formula taken from MRH forums:

"So far the only "rules of thumb" I have so far is (1) average 6lbs per ton to over come starting friction and average 3 lbs per ton once moving and (2) average 20 lbs per ton per % grade.  

Example: a 2-8-0 with a TE of 42000 lbs would be able to pull (42000/6lbs per ton) 7000 tons on level dry track. A little less that 140 (50 ton) cars after subtracting the weight of the engine and tender, plus the caboose.  On a 1 percent grade the total weight would reduce to (42000/26lbs per ton)  1615  tons.  This is very close to Dave's information concerning an RDG 2-8-0 pulling 1500-1700 tones up 3/4% to 1% grade. It is also close to what I calculated using Davis formula. I came up with 4.26 lbs per ton with the train going 1 MPH on level straight track.  4.26 lbs per ton is between 6 lbs and 3 lbs per ton."

Using this forumula, I could be able to derive what a "real" locomotive on the real Monk Subdivision could pull, then do the same with the layout conditions and see if the number of cars was close to what I saw when performing my test. Mike Confalone did something quite similar when dealing with diesel locomotive tonnage rating VS their horsepower. Here are the preliminary results:

As you can see, the "Layout" numbers are quite close to what I have seen on the real layout. By fine tuning my locomotives and tweaking the grades a little bit, it can be achieved. Keep in mind, that most steam era freight trains on the layout are 10 cars long, with longer ones reaching about 16 cars. Wayfreights with small steamers are generally about 6 cars long. As for passenger trains, the longest ones will have 8 cars. The Light Pacific will generally pull short ones, as it happened on Monk Subdivision, meaning it will pull 3-4 cars, which was fine when I tested it.

The table also gives me idea about which locomotives will need to be improved by adding some weight. IHC 2-10-2 will certainly need some because it's a little bit underpowered. Fortunately, there is still a lot of space in the boiler to do that. Spectrum 2-10-2 is almost alright out of the box. BLI Mikado is at its limits. The tender is lightweight and tracks badly. Also, the locomotive need more weight and I know many people did that to make them perform reliably. Bachmann Pacific, out of the box is too light. It seriously needs some extra weight under the boiler. Domes will be filled with lead at a minimum. The IHC Mogul will also need to be beefed up. I wish to rekitbash it and it will be a good opportunity to make it perform better.

In a next post, I will cover the options available to tackle this issue, namely the grade themselves. Fortunately, I have several options that will help a lot without rebuilding too much of the layout. Once again, using splines on open frame was the right choice for this specific layout.


  1. An interesting post to be sure. I hope you get the grade issues worked out. However, the big thing that jumped out at me was the reference to the Bachmann QJ. I have looked for these engines at train shows and online for years but never found one, even though Bachmann released at least a half-dozen different models of them.

    1. The grade issues shouldn't be too hard to work out. I did some tests yesterday and found out modifications are minimal. I can get the grades down to 1.5%-1.6% which would be perfect.

      I got a pair of QJs from a small import-export company dealing in model railroading based in Hong Kong in 2011. IIRC, the gentleman was Peter Lim and he was well-known for doing mainly business with people modelling Chinese Railways outside China that wanted these very specific models (Australia, North America and elsewhere). Mr. Lim offered good prices . Even at that time, they were getting very rare and pricy. I bought them on a whim since they were "affordable" compared to the market price elsewhere. They are fantastic models out of the box and are far superior to what Bachmann offer in North America. Back then, they had the level of details I would have expected from high end European models. I'm glad to have kept them! I also wanted the Mikado but they were out of stock. The last QJ he sold in 2012 were the sky blue version with the experimental gas turbine tender and the one with brass railings #2470 "Zhu De". I still see them on Ebay, but they are at least twice the price I paid back then. I also remember there was several batches produced and only the later one didn't have issues with the drive. I made sure to purchase these later models. I have one in the Jitong paint scheme and another one in the regular scheme. Knowing your interest in these locomotives, I'll probably post about them in the future! ;-)

  2. My, there's a lot to digest here! Yet these considerations are SO important, especially with the trend for serious modellers to build multi-deck layouts which necessarily involve grades between levels.

    I've done some reading on model steam loco suspension from a UK Scalefour club. Their website has this tome on the subject.

    I'm not sure that many would go to the lengths that these modellers do, but for a layout with a minimal steam loco fleet, I imagine that the average modeller could improve trackholding and thus loco pulling ability using some of the information in this article. Smaller steam loco models might benefit greatly by making some of the modifications described.

    For the rest of us (including me) it's experimentation with commercial models as you describe here. I especially find your figures for the Bachmann 2-8-0 and the Broadway 2-8-2 useful, as I have a few of these loco's.

    Thank you!

    Steve Lucas

    1. Thanks Steve! These modellers are insane (in a fascinating way). I've look at some of their weight distribution diagrams and they are really digging deep. If I were to build a small steam locomotive from scratch, such considerations would play a big roles. I wonder what were Rene Gourley's thought when he designed is gorgeous 4-4-0.

      One thing is sure, physics don't scale down, but they still apply. As I searched the subject, I was astounded by two things: 1) most people just don't care about how trains work, 2) those who cares still rely on 60-70 years old empirical data...

      I'm also glad to report I tested a Bachmann 4-6-0 (the newer ones) and it's also an excellent puller. The locomotive isn't very heavy, but weight is well balanced and the motor has torque. I pulled 1 boxcars and about 7 Athearn heavyweights without any issue. Only the IHC 2-6-0 is still struggling... This loco will need a visit to the benchwork!