I downloaded your model and I’ve just spent a good while looking around it.
I just kept selecting individual components to study in isolation as your attention to detail is so spot on.
All I can say is WOW !
That is an amazing achievement and I take my hat off to you.
I think Animator could be used to do a pretty good approximation of the combined up-down translation and back-forth rotation. Use the “easing” feature (I think that’s the term in Animator) to make the motions non-linear, giving them accelerations at the start and end corresponding to the harmonic motions that the real thing would experience.
Thanks - but wouldn’t the back-forth rotation affect the entire length of the con-rod whereas the top centre must stay on the vertical c/l?
Sorry - disregard that question - I think I now understand what you mean.
As you probably have realized, it is possible (and necessary) to create a hierarchy of components or groups in the SketchUp model and apply various transformations to different objects in the hierarchy. This can yield very complex net motion for the inner objects. For example, an up-down translation for the outer (parent) object in the hierarchy, and a back-and-forth rotation to the inner (child) object in the hierarchy. As the inner object rotates back and forth, it will also be moved up and down by virtue of the outer object.
Thanks you VERY much for that - that probably explains a lot.
I have been trying to get the motion for the connecting rod to work correctly for a few hours without success, but I didn’t realise I needed an inner child component to make it work. I have just been applying multiple translation and rotation movements to the same component and getting some very strange results.
I will try child components now which will hopefully crack it.
I can see those easing options you mentioned within Animater and can’t wait to experiment with them once the basic movement is correct.
Sorry @TDahl but if you have a minute I could really do with your help again please?
I’ve now made the connecting rod the parent and the bearings its inner child. The connecting rod is set to rotate back and forth and the bearings to move up & down. However they are doing exactly that independently of each no matter what I do.
Any ideas gratefully accepted 
This is the movement I am trying to emulate which I can, so far, only achieve by creating multiple individual scenes but which may ultimately be the method I need to use.
I did this very quickly and roughly so you can see what is happening. The whole rod is using a vertical translation and a rotation. So the rod moves down as one action, then at the same time rotates as another action. So this very clunky one has 9 moves, 8 to move the rod and one to rotate the wheel. The wheel takes 8 seconds and each of the four pairs for the rod take 2 seconds.
Thanks Box
Any chance you can share the file please?
Is your profile correct, are you using 2021?
Yes - that’s correct 
It is very basic and I didn’t bother naming anything so it may be confusing. Ignore the fact the rod is made of 3 parts, it’s the whole component that is relevant.
Con rod.skp (35.7 KB)
Thanks - that’ll give me something to get my head around today.
I don’t know very much about Harleys other than they look great - but I used to have an early 80s Yamaha 500 that looked pretty similar to your ‘around town’ ride.
And if the mini is yours as well we have even more in common
The ‘Harley’ is a Kawasaki VN 2000, two cylinders 1 liter each. The other is Yamaha SR 400, single pot 88 model.
Mini is the other halfs, I can just about get in it but I can’t drive it.
Its a Kawasaki??? how embarrassing!
I didn’t know Kawasaki made a 2 litre bike - now if you had posted this picture I would have realised (as I can read where it says Kawasaki)
That’s the year with the ugly headlight, mine doesn’t have it.
Enough of my bikes…back to topic now.
Just spent 3 hours solid trying to do this with Animator without success, but I did get close a few times - especially for 1/4 of a turn by using the info from @Box plus the Easing Settings (InPolyNom [3.0]) but as soon as I try to animate the full rotation things, for some unfathomable reason, go astray . I think if I can crack this then everything else falls into place so I am going to watch tons of instructional videos now and see what I can learn.
I have tried to create this crankshaft-connecting rod animation myself this morning. The motion is close but not quite synchronized. I did the animation in quarter-turn chunks. I tried using Animator’s oscillator feature but got myself confused between that and the easing feature. Here is the SketchUp model and two animations.
Engine Animation.skp (189.8 KB)
That’s excellent, thank you very much - I will learn a lot from your file.
I notice you used sawtooth oscillations on a couple of the sequences - was that to match the rotation more accurately?
