D&D 5E what is the cr of the infernal war machines in descent into avernus?

[Shades of Eternity]

Trying to figure out how they got their formula for extrapolation purposes.

 

[jasper]

They don't have a cr.

 

[DND_Reborn]

Not exactly the same thing, but close is the Hellfire Engine from MToF:

So, that is something of a basis if you want it.