Rainbows in the Lehigh Valley Gorge

[TMo]

Superelevation update for today. I'm pleased to report that 3 of the 4 sections of superelevated track have been tested for use with the Rapido M420.... and all passed with (eventually) flying colors - some tweaking was necessary, especially around track joints. I just finished running the 3 continuous sections at sampled speed ranges from low to max speed, forward and reverse in both loco orientations without derailing. I'm feeling pretty good about the future, and the light at the end of the tunnel is within sight (if I squint).

I did send Rapido an email message late yesterday - text of it is below. Not sure it will engender much good will from Rapido, and I think there's only a small chance that my message results in a change in design or some future words in a manual, but I had to try:

"Recently procured one of your products. This unit (an M420W #33014 "HO Scale MLW M420 (MR-20b) Canadian National #3545 (Stripes Scheme)) had been derailing at a very annoying frequency in a set of winding 26"-radius curves with a continuous grade of about 2% since I acquired it in December. I would have liked to have bigger curves and less grade on my layout, but I'm short on available space and have made due since 2006.

I have about 16 other diesel locomotives (4 and 6 axle) from a variety of manufacturers (Athearn, Atlas, Stewart, Bachmann, etc.). Your model was my first Rapido. No derailment issues for any of my other locomotives. Aside from the derailment issue, I LOVE your M420 (I think the details, weight and power are fantastic) and I want to keep it, and I want to run it. Therefore, I did a deep dive into these curves and the differences between this Rapido model and my other locomotives. Here are my findings (in no particular order):

1) The primary source of derailment for the M420 is wheel lift on one of the four axles as the loco negotiates these graded turns. Flange on the outside wheel (this can be either the front or rear wheelset of either truck) climbs over the rail or the inside wheel falls off the rail while turning and climbing or turning and descending the grade.
2) The main difference between the Rapido trucks and anything else I have is the relative stiffness of the trucks in the roll and pitch axes. They are less nimble (more rigid) and allow less potential movement in roll and pitch axes than anything else I have. I do not see any method to adjust this stiffness from my end - it's built into your design.

The aforementioned section of track has a lot of scenery installed and the track had been ballasted. Nevertheless, since I am bound and determined to run this model on my layout, I explored superelevating the outside rail in this set of turns by 2mm. Having the weight of the locomotive push the inside flanges into the rail (in my case) was the secret sauce to success. However, transitioning back to the flat tracks beyond the curves was also troublesome as the front and rear trucks end up rolling over constantly changing track profiles. What I found was a gradual superelevation change (at least 2 locomotive lengths) can work. Believe me, this exploration has been rough and I've spent the better part of this month on a 12-ft section of track and my new locomotive.

So, why did I write this? 1) I love your manual, but your tough-and-cheek comment about "no problem negotiating 18-in curves", and avoiding modeling theme park operations is a bit too flippant. Based on a couple of forum entries, it appears that I am not the only one to encounter similar problems negotiating much wider curves that 18-inch radii. 2) Since it worked for me, suggesting superelevating track may be something that is suggested in the manual if there are derailment issues in curves, or maybe you could look into this issue and potential fixes to layouts that will allow operation without derailment. 3) I'd suggest that retooling future models or offering a retro kit to allow for more pitch and roll of the trucks should be undertaken by Rapido.

Again, I care enough about keeping your loco on my layout so important that I trashed a good bit of scenery and spent a lot of frustrating days figuring all of this stuff out. I'm floored by the level of detail and the great operation (at least on straight track). I hope you can keep producing unique models like this one and I applaud your attitude toward our hobby."