Thanks for the comments, guys! When I get some pictures you'll see that it isn't as great as it looks in the video. I've got it set to run faster than what would be scale because I like to get work done when I'm on a machine and also so I could slow video down to about 1/4 speed and then it moves quite realistically. Just a simple matter of end point adjustment. I'd like to get one of those doohickeys that slow the servo down to make the swing speed up and slow down even smoother.
Lil Giants, don't worry, that's not cheating. Do it! Watch this:
http://www.youtube.com/watch?v=m41u14fuu_g
I got the twin screw version of the Vac-U-Tow
http://www.vac-u-boat.com/ . It's finished enough for test running but I never got any videos due to only having two hands, and I need to make some modifications to the house to get it looking more like a Columbia River tug and squirt some colored stuff on it.
SmallHaul, I thought about that, but draglines on barges just ain't done. You'd have to have the machine sitting right on the edge of the barge so it doesn't interfere with the drag cable and you have to have massive spuds so you don't bend them when you take a scoop. Also a clamshell's digging depth is limited only by the length of the hoist cables. But I do want to build a machine on tracks that can swing a clam or dragline bucket. If I get real ambitious I'd like shovel and backhoe fronts as well. I was eyeballing yours a while back. When I was little I would have gone without dessert for a year for one of those cranes, but they don't make 'em like that anymore.
Lorenzo, do you mean the tagline winder? It's got a spring pulling on a lever that has a line from the end of it wound around a 1/16" axle. On the end of that there's a narrow 7/8" diameter drum that the tagline winds onto. Basically it converts a strong pull and 2-1/2" of linear motion into rotary and back into about 3 feet of weak linear. It's kind of hard to explain but when I get some pictures it will be pretty self-explanatory.
Iron Art, you betcha.
When I see a crane barge on the river I try pretty hard (legally!) to see whose it is and what it's doing. There was a huge one working for several months off the Port of Longview recently but I would have had to risk life and limb to walk out onto the bridge to get a good view of it, so I missed out on that
Pictures to come...