I was thinking of getting a granny gear set up but don't want to replace the crankset. A triplizer is available but I need to order the correct size.

What is the bolt circle diameter of the old Nuovo Record and Super Record cranks?



Who makes small chain rings compatible with the old (~1970) Regina Oro 5 speed chains?



Is there a standard amount of extra spindle length needed to install a triplizer?


Is it just an extra chain ring's width plus the inter-ring gap? Can I measure the tooth-to-tooth spacing on the existing chain wheel and use that?