Specifications of the rear hub: 
Brand: Sunrace
Model: HBM45
Color: Silver
Number of spoke holes: 36GTS
Type of brake: Rim brake
Number of gears: Freewheel 5-7S
Type of axle: Fixed axle 170 MM
Axle included: Yes, with nuts
Type of bearings: Ball bearings
Average weight (GR): 293
Intended use: City
 
Data for spoke length calculations using the Sapim spoke size calculator: 
Total length of the hub (MM): 135
Non-gear side (MM): 34
Gear side (MM): 44
Hub diameter non-gear side (MM): 46
Hub diameter gear side (MM): 46
 
Link to spoke calculator: www.sapim.be/spoke-calculator