See my replay to philp.I think you will have friction problems, put at least one washer, with lubricant between the wheel's brass tube and the nut.
10-15 cars (minimum) at 60 to 80 cm(foot irl), it will strongly depend on the steam power or li ion powered motors and number of motors....I don't know the length of trains (number of cars) you want
The wish is double....but is this doable? time and experiment will tell
My smallest radii(outside track in the inside garden) will be 2.85(/3.00 and 3.15) meters for the big trains, around the house track will be the smallest 3.80 (/400 and 4.20) meters in radii.
ut there are very cheap ball bearings available.
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Comen sense for longer trains incl weight, but there is a lot more, how much weight does a car "need" for weight to stay on the tracks.
The fine info and prestigious data on your website.....I thought i was going with the one Ariosto craft uses.....i still must make the definitely choice....i have made some notes from your site!Are you using the G1MRA or Morop or NMRA standards for wheel specifications?
What do you advice?