dynamic front and rear hydraulics on tractors

[johannesschmalzl]

I’ve got another idea for more realism on tractors: dynamic front and rear hydraulics. On real tractors, these also oscillate slightly when driving over uneven ground. Below is the addition for your XML code.

        <!-- Front joint assumed at index 0 (negative rotation offsets in file) -->
        <set path="vehicle.attacherJoints.attacherJoint(0)#moveTime" value="3.04"/>
        <set path="vehicle.attacherJoints.attacherJoint(0)#comboTime" value="0"/>
        <set path="vehicle.attacherJoints.attacherJoint(0)#rotLimit" value="0 4 0"/>
        <set path="vehicle.attacherJoints.attacherJoint(0)#rotLimitSpring" value="0 0 310"/>
        <set path="vehicle.attacherJoints.attacherJoint(0)#transLimit" value="0.05 3 0.05"/>
        <set path="vehicle.attacherJoints.attacherJoint(0)#transLimitSpring" value="0 310 0"/>
        <set path="vehicle.attacherJoints.attacherJoint(0)#allowsJointRotLimitMovement" value="true"/>

        <!-- Rear joint assumed at index 1 (positive rotation offsets in file) -->
        <set path="vehicle.attacherJoints.attacherJoint(1)#moveTime" value="3.76"/>
        <set path="vehicle.attacherJoints.attacherJoint(1)#comboTime" value="1"/>
        <set path="vehicle.attacherJoints.attacherJoint(1)#rotLimit" value="0 4 0"/>
        <set path="vehicle.attacherJoints.attacherJoint(1)#rotLimitSpring" value="0 0 786"/>
        <set path="vehicle.attacherJoints.attacherJoint(1)#transLimit" value="0.05 3 0.05"/>
        <set path="vehicle.attacherJoints.attacherJoint(1)#transLimitSpring" value="0 786 0"/>
        <set path="vehicle.attacherJoints.attacherJoint(1)#allowsJointRotLimitMovement" value="true"/>

     </attributes>
</parentFile>

[DrewCZ]

hi @johannesschmalzl , please let me know why do you have spring value on another axis than rotation?

        <set path="vehicle.attacherJoints.attacherJoint(0)#rotLimit" value="0 4 0"/>
        <set path="vehicle.attacherJoints.attacherJoint(0)#rotLimitSpring" value="0 0 310"/>

I'm not skilled in attacher joints and this seems to be interesting.
understand, that rotaion is alloowed on Y axis for 4° free, and spring is applied on Z axis.
thank you

[johannesschmalzl]

Thanks for your question and your interest. To be honest, I’m still more or less in beta. The first tests are already promising, and the core functionality of my idea is working well. But there’s still a lot of fine-tuning to do. For example, the top link is still too spongy and has too much give—so plows hang too low at the back. But I’m working on improving it.

[johannesschmalzl]

Front (index 0)

moveTime="3.04"
What it is: Time (in s) for the front three-point hitch to travel from fully down to fully up.
Effect on the plow: Determines how fast it raises/lowers when you press the key—purely kinematic (animation), not spring stiffness.

comboTime="0"
What it is: Time offset (in s) that staggers combined motions within the attach/lift sequence.
Effect on the plow: No delay at the front; the movement starts immediately.

rotLimit="0 4 0"
What it is: Angular play (±) around X / Y / Z in degrees. Here only the middle axis is allowed: ±4°.
Effect on the plow: Minimal “pitch” around the permitted axis—the plow can follow small ground waves without wobbling sideways (X and Z are locked).

rotLimitSpring="0 0 310"
What it is: Joint spring stiffness for the three rotational axes.
Effect on the plow: The permitted rotation is noticeably sprung/damped (together with engine defaults); the front is comparatively softer than the rear → gentler compliance, less jerky.

transLimit="0.05 3 0.05"
What it is: Travel (±) in metres along X / Y / Z.
Effect on the plow:

X/Z: ±5 cm micro “float” to relieve binding (cornering, frame twist).

Y: a large window (±3 m) as a technical pass-through so the lift animation doesn’t snag the physics. This is not real spring travel; it only prevents animation/physics from “fighting”.

transLimitSpring="0 310 0"
What it is: Spring stiffness for the three translation axes.
Effect on the plow: On the middle translation axis a “hydraulic compliance” (float) is active. The plow can absorb tiny length changes (load shifts) without hard blocking.

allowsJointRotLimitMovement="true"
What it is: Allows the rotational limits to adapt when referenced parts move.
Effect on the plow: More stable physics while the lift arms are animated; no sticking—the joint cleanly follows changing limits.

Rear (index 1)

moveTime="3.76"
Effect: Rear raises/lowers a bit slower than the front → more realistic, calmer lifting of heavy implements (plow).

comboTime="1"
Effect: ~1 s delay within the combined motion sequence. This smooths the start/stop at the rear; the plow engages more “measured”, with less kick.

rotLimit="0 4 0"
Effect: Same as at the front: only the middle axis ±4°. The plow can pitch slightly but not roll/yaw—tracks straight behind the tractor.

rotLimitSpring="0 0 786"
Effect: Significantly stiffer than at the front. Pitch is allowed but strongly sprung → the plow “dives” less, holds working depth more steadily, and settles faster after bumps.

transLimit="0.05 3 0.05"
Effect: Same micro allowances as at the front (X/Z ±5 cm to relieve stress; Y large as a pass-through for lift kinematics).

transLimitSpring="0 786 0"
Effect: Higher longitudinal stiffness of the rear hydraulics. Under draft load the system “gives” less → more precise depth, less pumping.

allowsJointRotLimitMovement="true"
Effect: Same as at the front—prevents snags while raising/lowering.

What do you feel in the field with a plow?

Engaging/lifting:
Rear lifts in 3.76 s with a 1 s offset. No hard jolts; the plow stays on line (X/Z locked), only minimal pitch is possible.

Draft work over undulations:
±4° allows slight following of micro-topography. The rear (786) settles faster and holds depth tighter than the front (310), reducing “diving” after crests.

Cornering / relieving stress:
±5 cm on X/Z decouples small stresses between tractor frame and implement (no rattling/jerking) without letting the plow swing sideways.

Load changes / ground pressure:
The Y-spring (middle transLimitSpring) provides hydraulic compliance: slightly yielding under load to ease the kinematics, while the rear stays stiff enough that working depth doesn’t drift.

Practical tuning tips (if you want to tweak further)

More float / gentler compliance: set rotLimit to e.g. 0 6 0 and reduce rotLimitSpring a bit (or add rotLimitDamping, e.g. 0 8 0).

Even tighter working depth: raise transLimitSpring at the rear (carefully), or set rotLimit to 0 3 0.

Side shimmy? keep rotLimit unchanged but increase rotLimitDamping so the 4° don’t “free-swing.”

Hard knocks / clacking: slightly reduce transLimit on X/Z to 0.03–0.04 or add transLimitDamping.

[DrewCZ]

magic! thank you very much

[CiapekC330]

I have a suggestion. Could we introduce a weight limit for lifting implements in the front and rear hydraulics, based on the lift's maximum lifting capacity? Or perhaps the weight of the implement would affect its lifting speed—the heavier it is, the harder it is to lift? This could increase the game's realism.

[quadural]

I have a suggestion. Could we introduce a weight limit for lifting implements in the front and rear hydraulics, based on the lift's maximum lifting capacity? Or perhaps the weight of the implement would affect its lifting speed—the heavier it is, the harder it is to lift? This could increase the game's realism.

very good suggestion. One of the first thing that I noticed when playing "vanilla" => it seems so weird how fast the JohnDeere 3650 could lift an heavy plow like the agromasz 5 furrows one
But : this is not something I will try to add because =

1. I am already quite late converting base game vehicles
2. it definitely should be implemented in the base game (otherwise, we would have to add a new parameter for each tractor, "again")

IRL, lifting capability is one the the key point when buying a tractor.
But it is more complex than what people think =
indeed, a tractor with a lifting capability of 10T would never lift a 10T implement (except if we are talking of a cast iron ballast "implement", very close to the 3pt hitch attacher)

best example = plough or combination seeder. To be able to lift a 1.5T plough (5 furrows), you need more than 5T lifting capability
And IRL, the lifting capability is not the same depending on the lifting height. (but we don't have to simulate that ingame)

My opinion = in game, we should only get a system to limit the lifting speed depending on the tractor lifting capability and the implement weight. Something rather "simple".