Casey Rhodes wrote:So you are planning on having the tumbling shaft, lifting arms, lifting links and radius rod animated for changing valve travel and reversing directions? Also, having some kind of radio chatter would be really neat.
Yep, I've already modelled and animated the entire Walschaert's gear, including lifting links, radius rods, reverse rods, reverse shaft, everything all the way up to and including the Johnson bar and its latch (or clutch, not sure exactly what that bit is called). By the way, the latch handle is animated so that it automatically squeezes when you start to move the bar and releases (to drop the clutch/pinion into the teeth in the rack) when the movement stops, plus I implemented some hysteresis smoothing to stop the little lever from flicking open/closed when the movement of the bar (as you drag it with the mouse) isn't done perfectly smoothly.
The problem, however, is how to link the animation of the driving wheels and motion up to the radius rod, with the position of the reverser and the swinging back and forwards of the little lifting links. It's very tricky because the position of the radius rod and the length of travel of the valve crosshead depends on the vertical position of the lifting links, which is a parameter that can't be injected into the unique animation sequence of the motion to modify it. Instead, I'd have to create a separate animation sequence of the motion for every possible position of the Johnson bar. The animation of the Johnson bar has 40 possible positions (the throw of the lever is animated in 40 steps, in order to get the animation of the reverse rods, lifting links, etc. to be smooth). So, that would mean having to make 40 different animation sequences for the motion (and script it to activate the appropriate animation depending on the steady-state position of the Johnson bar). That would mean animating the position of each part of the motion 1600 times (because each unique motion animation sequence also has 40 individual frames), and all done by hand. I think it's practically impossible. I'll have to think hard about it, but I might have to fudge it so that there is perhaps one animation for fully forward (lifting links and radius rod at the lowest position), another for neutral (radius rods intersecting the middle of the links) and another for full reverse (radius rods lifted to the highest position in the links), but that would still mean that for most of the time, the lifting links wouldn't be properly connected to the radius rods.
Any suggestions?
Matt just picks from the ones I send him.
I also need to add some artificial highlighting to the textures.
Meanwhile, I'm becoming more and more eager to drive this engine, so get your domes and chests and whatever settled and let's put this beauty in the showroom. Thanks for sharing the nuts and bolts.
