diff --git a/lib/models/motor.py b/lib/models/motor.py
index 302dfc9..c8121bf 100644
--- a/lib/models/motor.py
+++ b/lib/models/motor.py
@@ -46,25 +46,25 @@ class MotorTank(BaseModel):
     discretize: int
 
     # Level based tank parameters
-    liquid_height: Optional[float]
+    liquid_height: Optional[float] = None
 
     # Mass based tank parameters
-    liquid_mass: Optional[float]
-    gas_mass: Optional[float]
+    liquid_mass: Optional[float] = None
+    gas_mass: Optional[float] = None
 
     # Mass flow based tank parameters
-    gas_mass_flow_rate_in: Optional[float]
-    gas_mass_flow_rate_out: Optional[float]
-    liquid_mass_flow_rate_in: Optional[float]
-    liquid_mass_flow_rate_out: Optional[float]
-    initial_liquid_mass: Optional[float]
-    initial_gas_mass: Optional[float]
+    gas_mass_flow_rate_in: Optional[float] = None
+    gas_mass_flow_rate_out: Optional[float] = None
+    liquid_mass_flow_rate_in: Optional[float] = None
+    liquid_mass_flow_rate_out: Optional[float] = None
+    initial_liquid_mass: Optional[float] = None
+    initial_gas_mass: Optional[float] = None
 
     # Ullage based tank parameters
-    ullage: Optional[float]
+    ullage: Optional[float] = None
 
     # Optional parameters
-    name: Optional[str]
+    name: Optional[str] = None
 
     # Computed parameters
     tank_kind: TankKinds = TankKinds.MASS_FLOW