lb/yd
pound per yard
Linear mass densityexact by definition
The pound per yard is exactly 0.4960546478... kg/m. It is the unit that names railway rail: 115 lb rail means 115 pounds per yard, which is 57 kg/m, and North American mainline track runs 115 to 141 lb/yd.
Watch out: European rail is specified in kg/m under the same logic, so UIC 60 rail is 60 kg/m, which is 121 lb/yd. The two numbering conventions look similar and describe different sizes.
| 1 lb/yd | 0.49605465 kg/m |
Where the unit came from
Rail has been specified by weight per yard since the earliest British railways, because the rolling mill sold it by the ton and the engineer needed to know how much steel was in a length of track. The practice outlived the imperial system in the countries that adopted it.
Solvers that use linear mass density