topic Re: Rigging a car driveshaft in 3ds Max Forum

Rigging a car driveshaft

paulchisholm — Fri, 08 Mar 2024 21:23:29 GMT

Any ideas how to animate a car driveshaft? How can I animate the wheel end up and down in the Z axis while the whole shaft rotates along it's length?

Re: Rigging a car driveshaft

leeminardi — Sat, 09 Mar 2024 15:38:09 GMT

The following should do what I think you want.

There are 4 bones and 3boxes. The boxes represent the three shafts of the drive train. The local X axis for each object is in the direction of the centerline of its shaft. Box001 is linked to bone001 with its x, y, z move axes locked and its y and z rotate axes locked. To see the behavior of the drive shaft rotate box001 about it local x axis.

A transform script is used to position and orient box002 and box003. At the junction of box001 and box002 for example, we know the direction of box002 is the same as bone002 and either the y or z axes point in the same direction. I assumed y (row 2 of the transform). Therefore the z axis is simply the cross product of x and y. I would think that the x direction of bone3 in world coordinates could be use as the x axis of box003. But this did not work as I thought it should so I just used the world coordinates of bone004 to define the x axis of box003.

I should add that I assumed that the joints are universal and not constant velocity. Universal joints are used for rear wheel drive and the angular velocity varies sinusoidally with respect to the input shaft.

Re: Rigging a car driveshaft

paulchisholm — Mon, 11 Mar 2024 12:14:36 GMT

Hi Lee,

Thanks for your advice. It's always good to discuss techniques and methods.

The boxes in your file do rotate about the bones as I need. However, I have a single mesh for the whole driveshaft with bellows that should deform as the suspension moves up and down rather than three separate boxes.

Also the first and last bone should remain parallel, connecting the differential and the wheel. I have it rigged so the movement of the bones is correct, but when I rotate the mesh it keeps its initial shape and rotates like a bicycle crank rather than rotating in place around the bones.

Here's a movie showing you what happens in my model.

Cheers.

Paul

Re: Rigging a car driveshaft

leeminardi — Mon, 11 Mar 2024 13:25:06 GMT

Interestig challenge. Can you post a Max file of the driveshaft and bones? Would it be feasible to use a hose object to model the bellows portion of the driveshaft?

Re: Rigging a car driveshaft

paulchisholm — Fri, 15 Mar 2024 11:12:33 GMT

Hi Lee,

I've animated the driveshaft texture and linked that to the rotation of Dummy044. I've attached a screen capture. I can link other items like the wheel and brake disk to Dummy 044 so their rotation can all be adjusted by the single dummy. Add the skin modifier with vertex weighting after the texture and the bellows work nicely with the texture following the movement.

Dummy043 imposes an orientation constraint on Bone06, so I can animate rotation of Bone04 to mimic bumps and Bone 06 stays horizontal.

I'm still curious if there's away to rotate the mesh rather than the material. The file is attached if you want to have a go.

Cheers.

Paul

Re: Rigging a car driveshaft

leeminardi — Fri, 15 Mar 2024 15:09:13 GMT

@paulchisholm it looks like a great solution!