Train moving on a Railway, file 3ds max 4.2

[dekert]

This is the file under construction that gave me the problem as described in my last post in this forum...
it's a 400 frames animation with a carriage running on a railway. As you can verify, front and rear wheels have the same, constant, velocity... (because I couldn't make it better!) but while front wheels pivot is correctly linked to the carriage, rear wheels pivot changes continuosly its position moving along the railway... I'm finding a way to link this pivot to the carriage body, without changing manually its position... but How?

Thanks for Anyone help or support!

[mac5er]

maybe you could explain a bit better.
I dont understand what you are trying to say here.
Maybe you could include a picture or a drawing to explain the problem you are facing.

[dekert]

Here's 2 jpgs of the Carriage moving on a railway.
In one, you can see the carriage in a right situation: rear wheels group is in the correct position.
...in the other the carriage is moving on a curve: rear wheels group (having a link only with the railway-path, and not with the carriage body), is in a wrong position.
This happens because path constraint doesn't allow me to create a second link to the carriage body... or is it possible to find other solutions?

[Schwinnz]

here's how yu can do it in max 5, dunno if it works with max 4...

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Create a bone structure without an IK chain.

Select the bone or object where you want to the solver to start.

Choose Animation menu > IK Solvers > Spline IK Solver. In the viewport, move the cursor to the bone or object where you want the chain to end and click that bone. Then right-click in the viewport to end the IK solver creation without choosing a spline.

Create a spline or NURBS curve to be used with the Spline IK system. It is recommended that you apply the Spline IK Control modifier to it to place helpers at each vertex and make the spline easier to control.

Select the IK chain crosshairs and access the Motion panel. In the Spline IK Solver rollout, click Pick Shape and click the spline.

With this method, the position constraint is not automatically assigned to the root bone, so it must be assigned manually.

Select the root bone. Choose Animation menu > Constraints > Position Constraint, and click the helper at the end of the spline that you want the root bone to follow.

On the Motion panel's Position Constraint rollout you will see the constraint assignment to the helper/vertex.

To make the bones follow a path:

Follow steps 1–5 in the previous procedure.

Select the root bone. Choose Animation menu > Constraints > Path Constraint, and click the spline.

With the root bone selected, go to the Motion panel. On the Path Parameters rollout, animate the % Along Path parameter to make the bones move along the spline path.