Levin's description of the project explains what we did.
While it might have sounded so awesome with the circuits and complex mechanism and all, this project failure exposed some serious deficiencies in how we operated (particularly me, because I could see #1 & #2 and failed to correct them):
1. Overconfidence in designs and paper planning, which led to no test run on location – and so we missed the ledge. It’s only common sense to test something in the environment that it’s meant to be used in, but our 2 brains (who I won’t identify) over-relied on brainpower and didn’t do a test run. My failure in this was failing to convince them: since I had joined late, I didn't have much sway over them, and so it went.
2. Lousy recces and measurements led to incorrect information about the clock tower, particularly the length of the ledge protrusions. The best would be to have a physical measurement (a plumb line would be enough), then an architectural blueprint, with pixel measuring (which our 2 brains relied solely on) only as a last resort. Pixel measurement isn't very accurate; there's too much uncertainties involved in it.
3. Overly complex triggering mechanism – A much simpler electromagnetic circuit (which would be familiar to any P6 kid) would have done the job, as shown in the diagram below. My failure was in thinking of it only after the project failed.
I do hope these deficiencies will be ironed out.....