Hammerschmidt requires ISCG mounts. The fsa patterson has a 28t ring with a 45t overdrive...but you cannot use it with coaster brakes(not sure which S-A 8speed you're looking at), you'll never push any of those gears in the overdrive position, and it costs like $300. I think a BMX 3piece crank with a euro bb would be your best bet, unless you haven't bought the rear hub yet, in which case an Alfine or a SRAM rear hub might do you better. (Or even just a 3- or 5-speed S-A hub)