Piston rig - how to make it to work like on this video (bones)

[Anonymous]

Hello,

For two days I was trying to make a similar rig, but I wasn't able to to figure out how he set the bones of the piston head to go up and down in one axis without twisting and reacting on movement of crankshaft. Link in his video to tutorial is dead. I don't want do use method with trig and math, to make animation more applicable for future designs.
In my dsign I want to replace piston head with additional shaft that I want to work the same way bot end in piston cylinder (it will be model of steam engine for game project).

Could I ask somebody for step-by-step instructions how to achieve the same effect of animation like on this video, or working link to some tutorial?
https://www.youtube.com/watch?v=MlEdNwiBcK0
Thank you for your help!

[malcomarmstrong]

What have you tried yourself so far? Its all well and good saying you tried, but thats not very convincing.

It may be better to show some work tried (and failed) when asking someone to invest their time to write and develop a tutorial for free, or to invest time looking online for something you could find yourself. I am assuming that you are not willing to pay for someone else`s investment, development and time.

Many will help you, but just asking for info when you have not shown any development is not the way to go about it. I know that seems grumpy, but I see a lot of posts like this where people ask for stuff they can easily source themselves.

Have you actually looked online for a tutorial yourself before you came to ask others to do it for you?

However, is this end result to be a manual process or a scripted one? 

Have you looked online for info relative to how a piston works?

Show what you have done so far and we can go from there.

regards

[Anonymous]

Ok, so it is that I made so far.
Green cylinder (rod joint) is linked to yellow (main shaft) with "link constrait" so it orbit around main shaft.
Red box (rod) and orange box (piston shaft) is linked with "position constrait" and works fine.
Red box "look at" orange, and orange "look at" blue box (placeholder, there will be casing of cylinder) and looking works fine. Also I figured already how to allow bone to move on one axis, so the orange box and its bone move correctly. The problem is, when main shaft is turned, bone of rod (wchich is linked with "position constrait" with green cylinder) starts to behave like on screenshot, break bone structure, and situation is like on the right screenshot.
This is the problem that I can't solve, everything else I figured out by myself or get from tutorials.

[malcomarmstrong]

Have a look at these:

http://www.torqsoft.net/piston-position.html

https://www.youtube.com/watch?v=-02mLcuNutQ

Whatever you do, you will need math to resolve it. Whether that be via bones or scripted expressuions, so you need to have a good grasp of the math behind the position and rotation.

[leeminardi]

Here are two videos I created for rigging a piston.  Sorry, but they do use math.  You can use the expressions I derived and just change them for the length of the crank and connecting rod.  Note that the part 2 tutorial has a better way to handle pistons at any angle.  Just create your piston to work in the x directions then link it to a dummy object as I explain in part 2.  

Let me know if you have any questions.

Part 1  https://youtu.be/VYaxjfu682w

Part 2 https://youtu.be/zDWGOCK_EcE

[leeminardi]

I had a chance to look at your file piston.max.  

I suggest the following.

1. Make sure your system units and display units are the same.  This is very important when using math in an expression controller.

2. Rename the objects so that they reflect what they are.  For example, "MainShaft" instead of "Cylinder002"

3. If you want to rig the model to be able to rotate the main shaft and have the piston move then delete all the bones and follow the youtube tutorials I listed in a previous post.  If you want to be able to move the piston and have the shaft rotate then you can use the IK approach (with, or without bones).

4. You state "Red box (rod) and orange box (piston shaft) is linked with "position constrait" and works fine."  You have used a link controller where only a simple link is needed.

I suggest you start over and create a crank, connecting rod and piston.  Forget about bones. Place a dummy at the end of the crank where the connecting rod should be and link the connecting rod to the crank.  You can then create an expression controller for the piston using the equations in my video.

Post the new "celan" model and I can give you a hand.

Lee