Summary

Duplo compatible train base for use on wood train tracks with other magnet coupled trains.

Instructions

The magnets I used were a bit too strong, but still usable.
https://www.kjmagnetics.com/proddetail.asp?prod=R621

I think that flatter tacks would be better at keeping the cars aligned over the bridge.
Dritz 44283 Upholstery Decorative Round Head Nails, Brushed Silver, 7/16-Inch, 24-Pack
http://www.amazon.com/gp/product/B0083VS2ZS?psc=1&redirect=true&ref_=oh_aui_search_detailpage

I have not been able to make nice rolling trains, so I did not print the axle, I ended up using this 1/8" rod.
http://www.amazon.com/gp/product/B00EVC4G62?psc=1&redirect=true&ref_=oh_aui_search_detailpage

I had to dill out the wheels, axle holes, and tack holes, otherwise it printed fine without supports. I epoxied the magnets and tacks into place making sure the magnets were oriented properly.

wood track magnet duplo train