First let me say that I am not someone who has a great appreciation for exquisite detail on my rolling stock so most of my freight fleet consists of lower end shake-the-box kits (Accurail, Athearn BB). However, I am very fussy about perfomance so I do everything I can to make these cars perform well. I make sure they meet NMRA weight standards. I replace the kit couplers with KDs and make sure they are the correct height. I ream the trucks with my MicroMark reaming tool and subsitute P2K wheel sets for the ones include with the kit. I check the wheel gauge with my NMRA gauge. As a result, even these cheap kits give me good performing rolling stock.
One of the final tests I do is a roll test in which I push the rolling stock down my 1.5% grade to see how far it willl roll. I have arbitrarily decided that to get a passing grade, rolling stock must roll at least to the station at the bottom of the hill to get a passing grade. Last week, the new builds that I tested all rolled well past that station. Today, the new builds barely reached that same station even though they were the same make of kit. I retested a number of the cars I had built the week before and found out they too were barely passing even though they had all rolled well past the station in their initial test. The only variable I can think of is the weather. Last week, we had a high pressure system with low humidity. This week, we have had a low pressure system move in with lots of rain, fog, humidity etc. I’m wondering if ths could explain why they wheels don’t seem to be rolling as freely as they had last week.
Well, I would guess a changing in temp could but not that likely. Have you pulled the wheels and checked for hair or lint? I have had some of my free wheeling stock act up after some long run time, trucks start to ware but not as quick as you have stated.
I have to agree with Ken even though extreme temp. changes and higher percentage of humidity are not the friend of the model railroader things in our world are not that that sensitive. It’s more of an over time issue where scenery and track for example warp as well as bench work if not prepared and built properly.
I here you on the not so into the exquisite level of detailed rolling stock but with the obvious asterisk details come better quality components such as trucks and wheel sets. Obviously running metal wheel sets is a most definite improvement over plastic ones and typically your better quality of rolling stock comes with metal wheels as well as the other component better quality trucks. Your roll test tells the tale and I feel it’s all you need that is after weighting and tuning the trucks and seeing if the wheels are in gauge. I would suggest going back to square one and if you don’t already own one invest in one of those truck tuning tools from Micromark, the wheel puller/adjuster tool and an NMRA gauge to make sure your wheels are in gauge and spinning true and easy.
Temperature could affect their rolling ability on cars where the axles fit nicely, but snugly, in their receptacles in the sideframes. Add 10 degrees and you may have a reaaaaaallllly snug fit, snug enough to cause some degradation. Also, with use comes debris in the bearing cups. Bits of plastic, lint, house dust, …name it.
I doubt that humidity could be a significant factor, even in excessive humidity where some condensation was taking place. I would be they need to be cleaned more than anything, and maybe it is time for the truck tuner gadget.
After I stuck down my track to my spline incline I started letting some cars roll freely down the hill to start looking for problem areas. The hill is about 30’ long and even though there appears to be no issues with the track the same cars came to rest at different spots on each run. Go figure! I am guessing it is the small flaws that sometimes make the difference on this kind of test, but wouldn’t affect day to day operation.