Problem with vehicle and articulated part

Hello there,

We’re having an issue with the physics of our trucks. These are attached via a constrain to their trailers, which is working fine so far. The trailer does have a VehicleMovementComponent as well, but without any controls.

The trailer’s placing and attachment is done via a blueprint. At the time the trailer comes to a halt - the velocity is at 0, so to say - the whole trailer won’t move anymore. The truck still reacts to input. Its wheel are steering and rotating on spot.
The trailer actually does have a little bit of velocity, but it’s barely noticeable.

We’ve tried various configurations for the truck, trailer and the constraint, unfortunately without any positive result. It looks like something is blocking the movement.

Thank you and kind regards,

Hi Rene,

I attempted to reproduce this in a new version of the Vehicle template, but I couldn’t get your results. Could you try reproducing the issue there or create a small test project using your assets, then upload it here?

If you don’t want to upload your assets publicly, you can send me a link to download the project by PM over the Forums.

I’m looking to do something similar to do a UE4 remake of farming simulator but having a heck of a time getting any kind of trailer to work, they have to have 4 wheels and I cant find a solution (constraints, physics handle, spring arms) that works at all for “pulling” a vehicle. It seems without throttle input the friction on the wheels is infinite on a “Trailer” (from me even trying to push one).

Looks like something that would require massive studio funded coding I dont quite have the skills in c++ to undertake the wheelvehicle class and physx for a pet project, Vehicles has always been an issue in UE4.

Hey Rene,

I’m still looking into this. I attempted to reproduce the results that I experienced in your project, inside of a new project that was based off of the Vehicle Template. However, I wasn’t able to reproduce the behavior there. Setting up a ‘trailer’ in the vehicle template work fine.

I’m wondering if it has something to do with the trailer being a separate blueprint, but I’m not sure why that would cause an issue.

is still in holidays so I will answer instead of him.

Can you send your project with the working trailer please?

Hey User,

Here is the test project that I created. It’s a super basic version of a truck trailer using the template assets.

Hey User,

Did the test project I sent help give you any clues as to why your setup was having issues?

Sorry for the late answer.
I don’t understand the setup of the wheels in your project. The Blueprint has only one Vehicle Movement Component with 4 Wheels setup. Which setup is used at the “trailer” Wheels? Is it possible to define more than 4 Wheels in the Component?

Hi User,

Sorry for the delay.

The trailer is the same Skeletal Mesh that is used for the base car but the ‘trailer’ component is using a different Physics Asset that has the wheels constrained to a particular axis. The reason for this is the base Physics Asset is not constrained and relies on the Vehicle Movement component to keep the wheels constrained properly.

As far as making a vehicle with more than 4 wheels, here is a bit more info on that. Basically to implement it properly you will need to dip into code. You can however ‘fake’ it by using a ragdoll/animated wheels as the extra wheels.