Specifications of the front hub:
Brand: Shimano
Model: HB-IM40 Nexus
Color: Silver
Number of spoke holes: 36GTS
Type of brake: Rollerbrake
Type of axle: Fixed axle 140 MM
Axle included: Yes, without nuts
Type of bearings: Ball bearings
Weight (GR): 375
Intended use: City

Data for spoke length calculations using the Sapim spoke size calculator:
Total length of the hub (MM): 100
Non-gear side (MM): 27
Gear side (MM): 15
Hub diameter non-gear side (MM): 52
Hub diameter gear side (MM): 52

Link to spoke calculator: www.sapim.be/spoke-calculator