A new notion of rank for finite supersolvable groups and free linear actions on products of spheres

For a finite supersolvable group G, we define the saw rank of G to be the minimum number of sections Gk/Gk-1 of a cyclic normal series G* such that Gk -Gk-1 contains an element of prime order. The axe rank of G, studied by Ray [10], is the minimum number of spheres in a product of spheres admitting a free linear action of G. Extending a question of Ray, we conjecture that the two ranks are equal. We prove the conjecture in some special cases, including that where the axe rank is 1 or 2. We also discuss some relations between our conjecture and some questions about Bieberbach groups and free actions on tori.