I decided to try and make a basic vehicle JBeam, which ended up being a tractor as they have no suspension and I found a very low polygon model to take dimensions from. I managed to make the general box shape section for the base of the tractor, and also make a very basic front axle for the wheels and steering. However I have been unable to get the hydro to do anything in game. I have also noticed that the inputs section of the debugging menus is blank, along with the Electrics page. Some help as to how to correctly set up hydros would be very useful. Picture of what I have so far:
Not very helpful is it. - - - Updated - - - Best bet is to ask DrowsySam because he used hydro's on his catapult so...
I'd add any engine to the vehicle, just copy one off the official content for testing. I found that not having any engine defined can screw some stuff up.
Was this solved? Because I have the same problem. I tried adding an engine, but the hydros still don't do anything.
Check your "camerasInternal" slot, sometimes if you have cameras defined that aren't actually linked to any valid nodes it causes problems, either add one camera that works, or delete the whole internal camera slot. It can cause weird things, like having invalid internal cameras makes the wheels leave skidmarks when they're not skidding, odd stuff.