| Dm6, Dm7 | |
| Service: | 1954–88 |
| Manufacturer: | Valmet |
| Yearconstruction: | 1954–63 |
| Numberbuilt: | 15 (Dm6) 197 (Dm7) |
| Numberpreserved: | 21 |
| Fleetnumbers: | 4000–4014 (Dm6) 4020–4216 (Dm7) |
| Capacity: | 64 passengers |
| Operator: | Valtionrautatiet |
| Carlength: | 16660frac=8NaNfrac=8 |
| Width: | 3100frac=8NaNfrac=8 |
| Height: | 3400frac=8NaNfrac=8 |
| Maxspeed: | 95km/h, later 115km/h |
| Weight: | 15– |
| Engine: | Valmet 815 D |
| Poweroutput: | 130kW |
| Uicclass: | (1A)(A1)dm |
| Aarwheels: | 1A-A1 |
The Dm6 and Dm7 were diesel multiple units built by Valmet in the 1950s and 1960s for Valtionrautatiet.[1] They are known by their nickname lättähattu (Finnish for "flat cap", the first widespread youth culture movement in Finland).
At the beginning of the 1950s it became clear that VR needed multiple units to compete with buses in short-distance traffic. In 1952, seven Dm6s were ordered from Valmet, and eight more the next year.
After testing the Dm6:s and having noted that the new DMU:s worked well in Finnish conditions, VR ordered more units. In total, 197 Dm7 class multiple units were built with some modifications (a larger wheel size, for instance).
Three Dm7:s (numbers 4145–4147) were transformed into goods transport vehicles. They were withdrawn in 1981.
16 Dm7:s were transformed into electric maintenance vehicles.
All Dm6:s have been withdrawn from service. 20 Dm7:s are preserved by Finnish museum railway associations.
No:4020 is at the Finnish Railway Museum.