[Boost-users] boost/units - converting forces (lbf->N)

To see if I understand the library, I want to create metric and imperial systems without using Boost Units predefined systems*.  Conversions between lengths are going well.  Conversion between forces are going well until pounds-force to newtons; line 182 in the link.  What am I doing wrong when lbf will not convert to newtons? Here is my code: https://coliru.stacked-crooked.com/a/f5f80d39fbdf8013 Any help is appreciated. * //imperial namespace boost {namespace units { namespace us {}}}//sinamespace boost { namespace units { namespace si {}}}