where can i get the washers and bolts for n scale 2-6-2 loco prairie

Hi .  I cannot seem to get the drive wheels to stay put they keep coming loose  what is keeping them inplace . Thanks, Dave.

I have  a used one that the lines are messed up  and the crane with the spring is not attached bottom line any where to see a breakdown to put it back together Thanks Dave

I just bought on e bay  a bachmann UP  2-6-2 It runs But the wheels come loose The same goes for my old bachmann 4-6-4 . is there someway to fix Thanks Dave