Hello, I’m trying to make different types of suspensions for my car system. I’ve started off with solid axle, simulating fake leaf springs. I used this to make it, however I don’t think it’s working very well. I’ve set it up like so:
However when I run it in-game, something unexpected happens:
The centre of mass (and also parent of Attachment1 of the axle hinge constraint) rotates slightly.
How would I fix this?
Are your HingeConstraints the same force?
Are the spring forces high enough to balance it out?
Is the mass of the car off center?
Leaf springs don’t hinge horizontally like that though. My post said to use 2 HingeConstraints and the pivot at the far end of the driveshaft. This means there is one set for rotation like you’ve got, but there’s a hinge that allows the whole axle to pivot up and down from the transmission end.
Here’s a screenshot of what I did in that post. The red axle, leaf springs, and driveshaft are one MeshPart that moves up and down pivoting on the left hand HingeConstraint. The Hinge in the center of the picture allows the axle to tilt, but it’s still connected to the left hinge so the axle moves for bumps that push one wheel up and not the other. As you can see I’ve also got my SpringConstraints pushed to the outside of the whole assembly to help balance the suspension left and right.
Hey!
Thanks for the reply, it’s an honour to speak with such a talented builder.
I didn’t know HingeConstraints could have forces… so they don’t have any. The spring forces are high enough, but I decided to start off from scratch and follow your picture. It’s working well so far, but I was wondering
Do you have any limits for any of the hinge constraint rotation?
Thanks again for the help!
Whoops, I meant SpringConstraint forces, not HingeConstraint forces, I’ll edit that.
I didn’t put Limits on the angles of the hinges, I just limited the lengths of the springs. If things start to bounce around past the limits you can add them. I just found the springs easier to find the best suspension travel amount for.
You can test drive that truck (and other vehicles with different physics setups) in the suspension test place on my profile!
Ah okay, that makes sense. I limited the lengths of the springs and it works a lot better (and with no jittering caused by hinge limits). This is fantastic!
Aha, I frequent that place! I’ve been there many a time. Thank you so much for the help! 
Awesome. You can see I kind of cheated on the leaf springs as the Mesh just disappears into the frame, but it looks pretty good to me and doesn’t involve any complicated mechanics or skinned meshes.
If you want to see more of the actual vehicles like the dump truck and pickup you can visit my construction site game. It also has an excavator, front end loader, bobcat and crane as well.
It’s awesome, great job doing it.
Sorry to necropost, but yesterday I tried to make independent suspension using hinges but its quite glitchy. Have you tried independent suspension? Should I use prismatic constraints instead of hinges?
Don’t use 2 hinges in line where 1 hinge can work. They will add lag and probably fight each other.
The dune buggies in the place I mentioned have independent suspension. You can see the A arms.
I use 1 hinge at the chassis for each pivoting arm, and at the top and bottom of the rear axle suspension for the wheel axle part.
For the front steering I use a hinge for each pivoting arm at the chassis and a BallSocketConstraint top and bottom for the wheel axle Part. This allows the part to pivot up and down for suspension, as well as twist left and right for steering.
As you can see it works pretty well.
For the pickup I use only the 1 suspension hinge at the front of the driveshaft. The other one allows the solid axle to tilt left and right for uneven terrain.
Sorry for the late reply. Thank you!
Hello again
I decided to try my hand at swing-axle suspension, and I saw no other way but to use 2 hinges in one line.
What are the 2 center Hinges on the axle connected to? If they are both connected to the swing arm then they won’t pivot on it.
I’d suggest 1 single Hinge at the closest end of the swing arm, connected to the axle.
Experiment with the Forces and Damping of your Springs. You may also want to move them farther out to each wheel. You can see from my picture that I attach the spring to the same Attachment as the wheel Hinge which gives it more leverage.
Also try experimenting with the Density of your wheel Parts, the friction of your wheels, the MaxForce, Damping, FreeLength, Stiffness,and Limits of your springs.
Change 1 property at a time to see if that gets rid of the jittering. If it helps then try changing one of the other properties. Keep switching and changing them, just like fine tuning the suspension on a real car. Changing one of them may affect the others so you may have to go back and modify the previously set values.
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