As seen above, with the bone rig I tried to apply, the green segment moves down as soon as the red segment starts rotating.
Is there some sort of Driver I can apply to detect a range of rotation on the X axis, on which I can apply a Shape Key to my injector to animate it going up/down?
At this point, it seems like the easiest solution, especially since I have 7 more of these that need to animate at certain intervals…
What about shrinkwrap modifier to controlling bone of green part targeted at surface of red part?
Hi Zruud, thank you for thinking with me!
I am new to applying modifiers to bones;
What would the shrinkwrap accomplish?
How would I go around setting this up?
I’ll try to make reference blend.
Hi again @veryKnightley
I should have mentioned this before, in your wankel post, but it would be helpful if could post up your file, or a limited part of your file. In the wankel thread, to figure out how to make it work, I just created a few circle mesh objects since I didn’t have the gears or wanted to spend time creating gears. Having the real mesh objects your working with would be better to figure this out…
It looks like you are playing with an overhead cam and valve lifter setup, (is it still a lifter if it’s pressing downward on the valve?).
My first thought would be to use a driver, but I don’t think that would work. An IK constraint might be the thing to use here. The IK target would be a bone at the tip of the camshaft lobe. The IK chain would be the lifter and valve. Then lock some of the IK constraint’s rotations so the chain doesn’t bend…
Randy
Hello @revolt_randy,
I noticed it is a common courtesy, but sadly most of the files I have to work with are proprietary so I cannot share them freely.
As for this injector, it was a paid asset and I would not want to be responsible for ‘leaking’ a complete model. Forgive my reluctance in posting these files in my original post.
I did manage to clear everything out of the engine, leaving only the assets that need to be animated:
Injector.zip (4.3 MB)
I am learning a lot in mechanical rigging with all the help the people on this forum are providing;
Sometimes its “on the tip of my tongue”, but I just need a visual to figure it out.
Thank you again for sharing your knowledge
This is what I could come up with:
injector_rig.blend (857.8 KB)
I believe there is some less complicated way though (maybe manually tweaked driver) 
Oh this looks perfect already!
I could go through this to figure out what you did, but would it be possible to get a bit of an explanation of what is happening here, with the Floor and Shrinkwrap modifiers etc?
I can try
Every bone except “B” is parented to “root”, so if you transform “root”, everything should hold together.
“B” is parented to “B_floor”, so it can be manually tweaked a bit.
“B_floor” is constrained to keep its position directly under the lowest of those five “shrink” bones.
“B_shrinkwrap_01-05” are constrained to stick to object “A”, so they are simulating the surface that cannot be crossed by the “B_floor” bone.
I also tried that “driver” method and…no 
I tried using a driver with a custom curve and I couldn’t get it to work. I had problems creating the curve that I will have to look at more closely. One should be able to create a curve for a driver for this, just like one should be able to create keyframe animation for something like this…
I’ll look at it again soon and see if I can figure out where I’m going wrong…
Randy
okay, I re-looked at this and figured out where I was going wrong. My problems were the fact that snapping was enabled in the driver editor window, causing my key points on the curve to not stay exactly where I needed them to. Setting it to ‘No Auto-Snap’ allowed me to create a driver curve that works in about 5 mins.
There does appear to be a little glitch when the control bone ‘A’ rotates around 270 degrees. In the attached file, look at frames 36-39 of the animation.
Randy
injector_rig_driver.blend (871.3 KB)
Here’s an alternate version using a Shrinkwrap modifier, and a small geo-node object to create a bounding box for the top object.
injector_rig_bounding_box.blend (903.4 KB)
I saw this solution while googling for a cam rig: https://blender.stackexchange.com/questions/199320/how-to-rig-animate-a-multi-lobe-camshaft
I did something similar to start, but there were portions where there would be a bit of an overlap. Adding the bounding box fixes that.
I’ve made a small fix to mine, so that the whole system can be rotated, and it will still work properly.
injector_rig_bounding_box.blend (905.6 KB)
I just want to say, thank you all for the wonderful collaboration on this issue!
The two Reddit forums where I asked the same question were less than helpful.
At this point in time, the timebudget for this issue ran out so I had to hook everything up to a Shape Key and animate its value by hand;
Not especially tricky but hardly a scale-able solution.
As soon as I can get some time, I`ll run through these various files and resources and see ‘what sticks’.
Thank you all once again, I love problems like these, how frustrating as they may be at times
