View Full Version : Mechanical Rigging- Am I setting myself up for a fall?

10-22-2014, 03:56 AM
So, as a personal learning project, I'm modelling a superdetailed 1950's BR Standard Class 4 Tank engine entirely in SubD, and I'm very pleased with my progress so far:


However, I've come to a point where my ignorance reigns supreme. Once modelling is finished, I'd like to animate all the various twiddly bits of valve gear, (as can be seen in the animation here (http://www.mekanizmalar.com/walschaerts_valve_gear.html) ). Now, I'm currently working on the cylinders and directly connected bits, and am getting near to the stage where I need to tilt them to the appropriate angle to the footplate, (see image below).


I've kept them straight so far, to keep modelling simple, but to get all the linkages and such like correctly dimensioned, I'll need to rotate them soon. Am I digging a huge hole for myself when it come to animation though? I've pondered doing this in nodal, but in quick tests, the networks gets messy very quickly, so I might try IK of one sort or another, but I really don't know that much about it.

So, finally, the question - Will I be alright rotating the cylinders now, or would I be better leaving them horizontal, then in Layout parenting them to a null, and rotating that, so all the slide-y bits still work in simple Z axis, rather than some complicated mixture of Z and Y?

Thanks :)

10-22-2014, 05:53 AM
Either way... Nodal certainly would be quite complex, network wise, but a mix of IK, targets and constraints can do all that just fine, just takes a bit of thought to put it all together to function as a whole unit. The only catch is making sure that the model itself is "viable", in so much as if it were built for real, would the parts line up properly during motion, or would they snag/lock... cos if so, then when the IK goes in it'll also lock up as there is no solution available to achieve a given "pose" within the action sequence.

Beyond that, short of doing it for you, its not the easiest thing to advise how to achieve, there's plenty on IK and such in my rigging tuts... also the walkthroughs like the digger and pixar lamp in there which help pick through less obvious setups and different ways of approaching something of that nature.

10-22-2014, 08:17 AM
Thanks, just wanted to make sure. :)

I have pretty good layout drawings to work from to construct the motion, as well of lots of pics of the real thing I took on a visit to the Bluebell Railway the other week, so once I get the angles right, I should be able to put everything together pretty accurately. In theory at least!

How do nodal and IK work together? Anything I should be aware of? I have a nice simple wheel rotation compound node I'd like to use, as I've read somewhere that expressions get confused after a certain number of iterations.

10-22-2014, 08:20 AM
check if there are any examples here that can help >

i think it should be...

edit, yes >

10-22-2014, 08:42 AM
How do nodal and IK work together? Anything I should be aware of?

All comes down to evaluation order...


10-22-2014, 09:59 AM
Thanks chaps, lots of stuff to do before I'm ready to start rigging though. I'd best get on with it... :D

10-22-2014, 01:36 PM
Not a lot of visible progress this afternoon, but I've been tweaking and lining things up so all the rest of the motion should go together the way it's supposed to.