I am getting a yen to machine something, but not an engine. I am somewhat intrigued by mechanisms that have an "automatic reverse" function to them. Not just a simple function like reversing gears, but more like something that moves along a short track, stops at the end of travel, then reverses movement and moves back to the original starting point and then repeats. The power source for this would be one of my many small engines. I have googled "reversing mechanisms" and there is a great array of articles posted about this. Of course, I want it to be something with a considerable "WOW" factor to it. I have the capacity to make spur gears here, but not internal gears nor funky gears like you see on a mangle.(Which is super neat.) The biggest problem I see to a mechanism like this is that when it gets to the "turnover" point, if it has to shift a lever to go into reverse it will probably just "hang up". The actual mechanism which moves something along can be a threaded rod with a threaded follower that reverses rotation, or a rack/pinion drive, even possibly a flat belt drive that shifts from a clockwise rotating pulley to a counter-clockwise rotating pulley. The big deal is that it has to do this without human intervention. I don't have the capacity to make a double reverse thread like you see on "level-wind" fishing reels. My tools are strictly limited to a manual lathe and a manual mill and a full set of 24 pitch gear cutters. I will have no problem designing whatever it is that I do, it's more the fact that I have to figure out exactly what I want to do. This is a wide open game, so if you have a good suggestion or a link to this type of mechanism working, by all means go ahead and tell me about it.---Brian