we are making bicycle parking racks from frames. very easy and effective. strip down frame, insert stem into seat tube, turn upside down and slide stem onto a 1" piece of round tubing. space them at about 30".
a 90" piece of round steel tubing works great: this allows an inverted bike frame on each end, with a frame at 30" and one at 60". this allows 8 bikes to be parked easily. the round tubing should be about 10" off the ground: this is accomplished either with a bmx frame on each end attached via stem in seat tube, or even simpler- bmx handlebars and a stem (similar to the bike stand set up that free ride pittsburgh has a picture of on their web).
i'll let the list know when we have a picture.
we have 6 of these racks, and we loan them out and/or take them to events (by bike trailer because they are so light). i'd imagine we could have them 'for hire.' we a couple of these in front of our shop too.
these racks are a use for frames that have been hit by a car, or low-end bikes.
you could also leave some parts on the bike, like the bottom bracket- that way, as energy gets more expensive, the parking racks could possibly serve as a part depo.
community gardens are a good outlet for these racks too.
if security is an issue, a quick weld or grind can make them more secure.