On my O gauge layout, when I run a train with some boxcars in it in reverse through an O22 switch, some of the boxcars derail. I have put mag balance weights in the boxcars, but I don't think they're weighted heavily enough. There are no problems with the track or the switch. Does anyone have any ideas how to make the boxcars heavier so they don't derail?
Thanks.
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Check wheel gauge and wheel flange the on the switch. You might try adding 5oz.plus 1oz. for every in of length of the car.
Paul
The NMRA weight recommendation for a 40 foot O scale boxcar is 15 ounces.
A Lionel Standard O PS-1 boxcar weighs just about 15 ounces.
MTH Premier 40' boxcars weigh 17 ounces.
Atlas Masterline 40' boxcars weigh 19-20 ounces.
If you are running modern scale boxcars they shouldn't need more weight unless you have some other unusual operating conditions. If you have older/smaller/lighter boxcars I would weight them until they are in the 15-20 ounce range.
Be aware the O-31 curves are what they have always been, toy train curves. They are very tight and backing a long train through them entitles cars to cause problems. Additionally, O22 switches were not very good 60 years ago and they haven't gotten any better with time. Modern switches like Fastrack and Ross are better functioning switches and the larger diameter modern switches are better still.
If you want to back a 20 car freight train through a switch you should be able to do it using stock modern O scale cars like those described above if you are using O-72 or larger curves, a modern track system like Fastrack, Ross, Atlas or Scaletrax and a modern locomotive with Proto 2, Proto 3 or odyssey II run at a steady slow speed. If cars, track or locomotive control are "traditional" things get harder quickly. If cars, track and locomotive control are all traditional backing trains through a switch reliably is very hard indeed and you will be doing well to back a 6-8 car train through an O-31 switch consistently without derailing.
A Lionel Standard O PS-1 boxcar weighs just about 15 ounces.
MTH Premier 40' boxcars weigh 17 ounces.
Atlas Masterline 40' boxcars weigh 19-20 ounces.
If you are running modern scale boxcars they shouldn't need more weight unless you have some other unusual operating conditions. If you have older/smaller/lighter boxcars I would weight them until they are in the 15-20 ounce range.
Thanks for this info, Ted. Is there a reference list available somewhere of what the NMRA weight standards are for all the various types/lengths of freight cars? Or should we just use a formula to calculate the amount of weight needed based on car length as NCT mentioned above?
Joe
The NMRA recommendations for car weights in all scales are in RP-20.1
The NMRA recommends 5 ounces plus 1 ounce per inch of car length in O scale. For a 40' boxcar (10 inches long in O scale) that means 15 ounces total. That is just a recommendation and I think that many of the 3 rail manufacturers are correct in going a few ounces heavier. For trains up to 20 cars and curves of O-72 and greater, especially using numbered switches for yards and sidings all the popular Standard O, Premier and Masterline freight cars play well together without having to add any extra weight.
All the NMRA standards and recommended practices can be found at the link below. I have found the car weight recommendations to be pretty good for 3 rail O scale. I wouldn't go lighter than the recommendation for a box car. A 40 foot flat car with its low center of gravity will be ok a little shy of 15 ounces. A few, even several ounces heavy is fine. If you go too heavy or too light car location within a train made up of mostly standard weight cars becomes an issue.
For 3 rail some NMRA standards are not so good. The standards for 3 rail track are terrible. If you want dimensional standards for 3 rail switches just measure a Ross! The NMRA should really just ask Steve to rewrite their 3 rail track standards. 
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