sri, it's HO scale
I'm hoping to replace the coupling completely and eliminate the draw bar arrangement - I have - weighted - the tender as a partial, yet unsatisfactory solution

     I have the above locomotive with short haul tender. It uses a draw bar 'coupler' between the two. The tender derails consistently even on straight stretches. 
     Can I replace the draw bar arrangement with something elso to corect this derailing situation ?
     Thanks for your advice -

     deepest