Great post, Paul. Cry away……good therapy! So what if the beer tastes a little salty.
After your confessional I'm moved to post a personal embarrassment that might be worthwhile to other members for its warning about use of wire rope.
After some thefts of personal-property items left outdoors in the town we lived in, I decided to keep our Grumman 15-ft canoe inside the garage, but because space was tight I suspended it from the ceiling using two transverse 2 x 4s, each hung from two 1/8"dia steel wire ropes. At that diameter they're usually called "airplane wire," I think. I mounted a hand-cranked winch on one wall and ran the ropes from the winch through pulleys to four appropriate points, from which the ropes dropped to the 2 x 4s.
The canoe weighed about 85 lb, and from a tensile load standpoint my system was VERY conservative. I don't recall the actual ratio of total working load for the four ropes to the weight of the canoe, but do remember clearly that I played it extremely safe on that score.
My mistake—which nearly killed me—was to use tiny pulleys. Each had a sheave diameter of about ½". I was totally ignorant of safe design for such a system and hence did not know that with a rope diameter/sheave diameter ratio of only 4, no matter HOW conservative the application was regarding LOAD, I was condemning the WIRES in the strands of the ropes to be bent so badly in passing over the sheaves that their yield limit would be exceeded with EVERY PASSAGE over a sheave!
As one who had an ME degree, even though I didn't stick with engineering, I should have had the sense to read up on safe practice with wire rope before making that lashup, but didn't. That was embarrassment No. 1.
No. 2 was not reacting to the warning the poor tortured wires tried to give me. Every time when the canoe was lowered to the racks on our car, and thus the load removed from the ropes, they immediately assumed helical shape. "Oh, look at the pretty barber poles," I said to myself. Not even a glimmer of thought as to WHY they were helical.
Embarrassment No. 3—the worst of all. I failed to react when after a few uses of the system, wires in the strands began to BREAK! Existing vocabulary is not adequate…..some new word needs to be invented to convey my dumbness with that one.
So came the day when one wire too many gave up the ghost as I lowered the canoe. Thank goodness I wasn't trying to put it on the car, just getting it out of the way of the garage door opener to fix a problem. Lordy oh lordy, what a grand and glorious C-L-A-A-A-N-G that Grumman aluminum canoe made when it hit the concrete floor! This only about a second after my (obviously empty) cranium had been right under the end of the canoe. You know…where the side profile comes to sort of a POINT.
What a great headline it would have been for The Berkshire Eagle: "Pointy canoe meets pointy head in Richmond…..gene pool improved."
The recommended sheave diameter/rope diameter ratios in Machinery's Handbook vary with type of rope, application, etc., but my rough rule of thumb now is 20--not that I'm likely to design any future system!!! After my close call, I started noticing the sheave diameters relative to wire rope size on various cranes. Although I made no measurements, my impression was that the sheave diameters were AT LEAST 20 times rope diameter and perhaps more.
I went to our local hardware store in Camden last year to see if the wire rope section had any information for buyers about safe design, and noted a sign warning people not to use wire rope for suspending loads……period. Soon after I was at the Home Depot outlet in Rockland, and saw NO application information of any kind at the wire rope section.
