Proper belt tension on the lower rotor drum

[Baseman norm]

What is the proper belt tension on the lower rotor drum in a 251 ?

Thank you in advance.

[peterb_2795]

I normally set the tension (just using finger tension to guesstimate) such that the belt slips in such a manner that it takes the lower drum 5-7 seconds to get up to full speed.
Note: I don't have a 251 but have 147 and assume that you would want the same effect from the lower rotor in a 251.
HTH...

[Baseman norm]

Ok thank you
I do belive they are the same motor stack and rotor
What is the diameter of the lower motor pulley on the 147