I have never seen a cylindrical slide rule, but I have seen a gigantic linear slide rule. The whole instrument itself was probably between 10 and 15 feet long

I have never seen a cylindrical slide rule, but I have seen a gigantic linear slide rule. The whole instrument itself was probably between 10 and 15 feet long and about 1.5-2 feet wide. I don't know what the total scale length was, because I never got to see it up close. It was hanging above the blackboard in one of my high school math teachers' rooms. I think the effective scale length might have been rather small, because, IIRC, it was actually a demo instrument used to show people in math classes how to use a slide rule.