Slide Rules

It seems like it would be physically impossible to make a flat spiral _SLIDE_ rule (where one scale can be repositioned against another scale). The Computer History Museum has a spiral slide rule (http://www.computerhistory.org/collections/accession/102633252), but it is not clear from the picture if the scales _SLIDE_ against each other. In a spiral, the area of a segment that as one degree wide by one spiral line to the next decreases as one goes toward the center, so a slide would bind if you tried to turn it toward the center or would be loose and not evenly contact the next band if you turned it away from the center. In an earlier post in this thread, someone said that they had not used their slide rule in anger. As a kid, I made something that would have been useful if they had wanted to. I took a cheap wooden slide rule, lightly sanded the groves, waxed the slide, and wrapped four big rubber bands along the length, so one end was on the outer part at one end and the other end was on the slide. Worked sort of like a cross bow or spear gun. I could send the slider through 6 layers of corrugated card board at about 20 feet! Bob