Hi everyone,

I'm evaluating Bongo 2.0, and would like to use it to work out some vehicle suspension kinematics. I can't seem to figure out how to make Universal join constraints stay connected. 

I have created a small spline and point to drive the vertical tire movement, it's snapped to the upper ball joint. It moves up and down around 2". I would like this to only drive the height of the suspension travel, not exact position.

The control arms are both set as hinges, rotating about Y axis, in local object space.

I linked the lower control arm to a 'universal' point, and linked that point to the spindle (vertical member line). I linked the top of the spindle to another point, which is constrained to the animated point on a path. 

I did similar for the upper control arm, except I didn't link it to the spindle, as they are both linked to a universal location at the top. 

When I animate the suspension travel you can see the points become disconnected. 

I am just starting out so I am hoping there is a setting to have all connections force to stay together. (2nd picture)

Thanks,

Carl

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This is a shot showing the 4 points attached to the chassis that need to remain static. The other 2 points need to both translate, and rotate at the same time as the suspension travels. Bongo doesn't seem to want to let me do this. 

I've set it up this time like one long chain, 2 hinges (top and bottom) that rotate in one axis, and the rest are universal joints. It rotates when I animate the lower control arm, but when I add the constraints for the 2 points on the top arm, it stops animating. 


Thanks,

Carl


Hi Carl,

Any chance that you could post the model?

It's quite hard to say what goes wrong without having the actual model.

Sure, its basic, but I'm just trying to wrap my head around it before bothering with real geometry. 

Thanks for the help,

Carl

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Something like this that you want to achieve?

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Thanks, that's very close, but the rear node of the upper arm moves, and it needs to be stationary. When I add another point constraint to it, I lose connection of the 2 main pivots of the 'spindle'. 

The spindle will rotate, while it travels upwards, and likely both a-arms move at slightly different rates, this is what I cannot seem to achieve. 

Thanks again,

Carl

Also it looks like the upper arm was scaling, these will be solid metal parts. With pivots in one direction where I labelled static, and ball joints at the 2 outer locations.

If you uncheck the scaling for the universal joint it won't scale. 

Looks like I sent you the file which didn't have that unchecked.

Have to say that I'm having a hard time following what you want to do.. Any chance that you could look up a similar animation online so that we could have a look at that?

Thanks, that's very close, but the rear node of the upper arm moves, and it needs to be stationary.

Do you mean the object called UCA -should not move at all? Not in any direction?

When I add another point constraint to it, I lose connection of the 2 main pivots of the 'spindle'. 

 - I'm not sure what you're talking about. An object can only have one pivot.

The spindle will rotate,

- Currently there is nothing in the IK -setup that will make the object called Spindle rotate. The movement of the IK-cahin comes from the object called LCA, and that movement only pushes the object called Spindle upwards.

Sorry I havent been as clear. 

I have attached another picture, hopefully it helps. 

The 3 white circled areas, are static in position, and only rotate in 1 plane. 

The 2 black circled joints, top and bottom of spindle, rotate in all degrees. So the spindle can rotate while travelling up and down. 

This is the front suspension of a car. 

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Based on your revision of my file, I changed a couple of things, and it works, sort-of. The problem is the 2 universal pivots, spindle top and bottom, become disconnected. I think maybe because the spindle doesnt rotate correctly as the lower arm is moving it upwards? Its rotation should be controlled by the top joint I suspect, though I'm not sure what happens behind the scenes in Bongo.

Thanks again.

Carl

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Something like this:

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Eureka Marika!

Interesting, it was missing 1 more constraint at the end of the chain, and now it seems to work as expected. 

Can you look at the change I've made quickly?

I see all 'parts' have been made not hinges, joints, or constraints, just regular objects, but part of the heirarchy. The rest have been made hinges, or universal joints which only have rotation. 


Seems to do the trick, will try with proper models now. 

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