Nord 3.606 to 3.787

Nord 3.606 to 3.787 were 0-6-0 locomotives for mixed traffic of the Chemins de Fer du Nord. The machines were the continuation of the Nord 265 to 274 (3.265–3.274) Mammouth locomotives of 1849, and hence were also referred to by the same nickname. They were retired from service from 1910 until end of 1930.

Construction history
The first series, Nord 3.621–3.660, dated back to 1860. Regarding the dimensions and disposition of the frame and drivetrain it was derived from the preceding Nord 265 to 274 Mammouth locomotives of 1849. Contrary to the 1849 type the machines were fitted with a Crampton-type boiler and firebox. The firebox extended over the rear driving axle and the boiler consisted of three shells. A Crampton steam regulator was mounted at the front and the steam pipes were routed down to the cylinders on the outside of the boiler. The two cylinders were mounted inside the frame in an inclined position and had a Stephenson valve gear. The machines weighed 26.6 t and had a tractive effort of 4017 kg. They were coupled with two-axle tenders, holding 7 m3 of water and 3 t of coal, and weighing 19 t.

The type of 1861 had a boiler pressure of 8.5 kg/cm2 and increased the maximum tractive effort of 5254 kg. The next type in 1861–1863 had an increased cylinder size of 380 x which yielded another increase in tractive effort to 5821 kg.

The next series, Nord 3.663–3.697, was put into service in 1866–1867. It also had cylinders of 380 mm and weighed 27 t.

The machines of the next series, Nord 3.698–3.747, had an increased power output. They were built in 1875–1878 and had a Belpaire firebox and boiler with the dome on the rear boiler shell. The leaf spring of the rear axle suspension had been moved down below the firebox and the cylinder size increased to 400 mm

The newer locomotives had an increased boiler pressure of 9 kg/cm2, and on major overhauls also the older machines were brought to this standard.

The last series, built in 1882 and comprising Nord 3.606–3.620 and Nord 3.748–3.787, was built with vacuum brake and cab. The machines had a boiler pressure of 10 kg/cm2 and a tractive effort of 6849 kg.

In 1880 four locomotives, Nord 3.621, 3.630, 3.634 and 3.639, were transformed to tank-locomotives for tram service.

Service history
The locomotives were used for mixed service on the main lines of the Chemins de Fer du Nord, as well as on less important lines, and later were used for local passenger trains, mixed service, freight trains and shunting. The last locomotives in service, the Nord 3.685, 3.714, 3.718, 3.732, 3.745 and 3.774, were removed from service with 30 December 1930.