Model Train gets ball bearings on the engine axles. First set test build for proof of principle. 

using 4mm ID flanged bearings fit into the bushing bores, I added a slight notch to allow the flange to fit flush. Although a dimes worth of flange could stick out. We do need the wheels to have some gap for float. I find the 4mm is a good fit and provides a very smooth rolling action. Since my existing Chassis is so worn I may have to replace it for the best operation anyway. I am thinking i may try to build a Ball Bearing Chassis for it NOW. It would cost me a few days in completion but i think the results maybe so good it would be worth it. I can now cut axles to length, Insert the wheels. The open issue is locking the drive gear to the 4mm Stainless shaft. Will Locktight hold the gear to the shaft ??? Or use a Flyer Drive Axle with gear locking knurling then the left side bearing might be too small for the larger O.D. ??? I could measure one up and see if they was a 4.5 I.D. bearing and would it work. UGH! nothing is easy. Or turn that larger O.D. down that may be the best approach. D