Thank you. I know nothing about Quartering wheels so will have to check on that. 

I have 7 of the Thomas themed engines that I bought to run for my grandchildren. 4 are working great and 3 seem to be locking up. They do not have many hours on them and I have cleaned the track well.  I know they are not the highest quality but was wondering was there something I could do to loosen them up.  They are about 2 years old.  Thanks.