I explain that I am into railroad research and "yeah, I play with trains also". And I look straight into their eyes when I say this.
If we at my house I'll offer them a copy of my railroad societies historical magazine with an article that I've had published. After looking at the article for a moment, most people give an appreciative grunt. Most professional people acknowledge the work that takes.
Now with others, (it depends on the read you get off them or if they are - the nasty ones - as described by Roger above.) I'll answer that "I do historical research, mostly about railroads. And before you ask, do I play with trains? Yup, just like Reverend Lovejoy on the Simpsons ! " I've found that to generate anything from a smile to more often laughter. For most of those nasty types, the humor completely deflects any follow up they might have. Other people, it seems to put them at ease. Matt Groening always has wrote Reverend Lovejoy's model railroading experiences as never going too well. A useful foil.
Jim Dick - St. Paul