I have had quite a few. I make a lot of homemade implements so sometimes the developing of those implements takes longer than I have time for.
That is not a cop-out. Like I built a rock and stick rake for clearing land on my farm, and it worked...sort of, but it would jamb up sometimes because it needed better bearings, and wheels that did not flex. It was a time-sensitive job...a short period of time from when I could get on the field without rutting it up, to when the grass was too high, and so it was just easier to pick the sticks up, then order steel, fabricate, weld, and refine the rock and stick rake.
It really was not a failure, I just did not have time to perfect it. That happens a lot for me.