HydroGlide Active Suspension 1.0.2

HydroGlide
Hydraulic Suspension



52% less body travel over bumps · 61% less nose dive · 55% less body roll
HydroGlide vs the stock Grand Marshal Luxe, measured in game. Full table below.​

Your Grand Marshal hits a bump at 40 km/h. The wheels hammer away. The cabin barely notices.

HydroGlide builds hydraulic suspension and fits it at the factory, together with the carmaker. Launch partner: Gavril. Launch car: the Grand Marshal. More cars are on the way.

Stock Luxe, HydroGlide Assist and HydroGlide

Quick start

1. Subscribe in the in-game repository (or see Installation below).
2. Spawn the Gavril Grand Marshal and pick Luxe HydroGlide (A) or Luxe HydroGlide Assist (A).
3. Drive. Shift+J changes mode; hold T / G to raise or lower.
4. For the live dashboard: UI apps menu → HydroGlide.

Pick your HydroGlide

HydroGlide Assist in Silver, HydroGlide in Shadow Blue

• HydroGlide Assist · $57,500 · On / Off
  The subtle upgrade: the stock car, calmer. Stock coils and shocks with short-stroke cylinders (±40 mm) underneath; pump and accumulator in the trunk (35 kg).
• HydroGlide · $72,500 · Glide / Sport / Off
  The magic carpet. Soft coils on long-stroke cylinders (±100 mm) and race anti-roll bars; heavy-duty pump and accumulators in the trunk (70 kg).

How it works
Under every coil spring sits a hydraulic cylinder, fed by an engine-driven pump and an accumulator in the trunk. The control unit checks the body position 2,000 times a second and moves the cylinders to cancel float, dive and lean.

The cylinder moves the spring seat, and force goes through the coil spring, like the factory active systems of the late 90s.It's real hydraulics: pump, accumulator, servo valves and end stops, each with its own limits. Push hard enough over rough ground and you can drain it: the ride goes soft until the pump catches up.

The numbers
Measured in game against the stock Grand Marshal Luxe: same course, same speed, same inputs, every car freshly spawned. Over the bumps: mean of 2 runs each.

• Broken road, 40 km/h, body travel: stock 13.2 cm → Assist 8.9 cm (−33%) → HydroGlide 6.3 cm (−52%) · Sport 7.8 cm (−41%)
• Broken road, 40 km/h, pitching: stock 6.9° → Assist 3.3° (−53%) → HydroGlide 2.2° (−68%) · Sport 2.9° (−58%)
• Hard stop from 90 km/h, nose dive: stock 4.1° → Assist 1.7° → HydroGlide 1.6° · Sport 1.2°
• Steady turn, 65 km/h, body roll: stock 4.1° → Assist 2.9° → HydroGlide 1.9° · Sport 1.7°
• Hills and crests: the body follows the terrain instead of fighting it. In the dip at the foot of a hill, HydroGlide keeps 19.2 cm under the body (stock: 19.9 cm).

Motion trail over the same bumps: the stock car rocks, HydroGlide stays level

Hard stop and steady turn, the three cars side by side

Body height and pitch along the bump course (all five configs)

Pitch through the hard stop, roll through the turn

Glide or Sport (HydroGlide, Shift+J)

• Glide: the magic carpet. Best over bumps.
• Sport: the flattest it gets (1.2° dive, 1.7° roll). In a long stop it pitches the nose back up before the car settles.
• Off: the cylinders sit still and the soft springs carry the car.

1.5 s into the stop, Sport has already lifted the nose

Watch it work
The HydroGlide dashboard app is a green-LCD instrument straight out of a 90s luxury dash. It shows, live:

• Each corner: cylinder position (amber at the end of travel) and pressure
• The accumulator: pressure, the pump's cut-in and cut-out marks, a CHARGING light
• The pump: power in kW and oil flow through the valves
• Mode, ride height, and a LOW PRESSURE warning when you've outrun the pump

UI apps menu → HydroGlide.

Cylinders working, accumulator charging, a rear cylinder at the end of its travel (amber)

Under the trunk lid

• Open the trunk and the pumps and accumulators are right there: 70 kg of hardware (HydroGlide), 35 kg (Assist).
• The pump runs off the engine and takes real power from it: over the broken road at 40 km/h it averages 10.5 kW (about 14 hp) in Glide, 7.7 kW in Sport and 5.7 kW on the Assist. Its whine rises and falls with how hard the system is working.
• Engine off: the pump stops, the active control fades out and the cylinders settle back.

The pump and accumulator pack

Ride height
Hold T / G to trim the ride height up or down by 2 cm (front and rear separately with Alt). The cylinders hold that height whatever you load in: passengers, luggage, a full tank.

Bonus: SkyGlide, the experiment
HydroGlide doesn't only do hydraulics. SkyGlide is its experiment with electromagnetic suspension, in the spirit of that famous one: a heavy linear motor at every corner, power amplifiers and a capacitor bank in the trunk, all on self-leveling air springs. It works like magic: no pump, no lag, no limits. (Honestly: its corner force is idealised. HydroGlide's is not; it lives within its pump, valves and stroke.)

It was only ever fitted to the Grand Marshal as a test bed, and it was never sold: the hardware adds 190 kg, and nobody would pay the price. Two test cars are included, a Luxe and a Limousine.

• The full air-ride height range on T / G: the body goes from 10 cm (slammed) to 34 cm (lifted) above the road.
• Park with the engine off and it settles down to rest; start it and it rises back up.
• Being experimental, they don't follow the terrain, so a sharp dip at the foot of a hill can make them scrape.

SkyGlide test car: slammed, ride height, lifted

Keys (Options → Controls, search "Suspension")

• Shift+J: mode (HydroGlide: Glide / Sport / Off · Assist: On / Off)
• T / G (hold): raise / lower (HydroGlide ±2 cm · SkyGlide full air range)
• Alt+T / Alt+G: front only · Alt+Y / Alt+H: rear only
• Shift+T: auto-leveling on / off (SkyGlide)

If a key doesn't respond the first time, press Ctrl+R once (reload vehicle).

Tuning (Tuning menu → HydroGlide / HydroGlide Assist)

Spoiler: Every tuning option

• Active strength and default mode
• Cylinder stroke
• Pump size and flow limit, accumulator volume
• Valve flow and response
• Body-float, pitch and roll control
• Terrain following
• Spring rates and damping (HydroGlide)
• Sound volume

Engineering notes (for the curious)

Spoiler: Spec sheet and how it was tuned

Spec sheet (defaults; most are in the Tuning menu)

• Cylinder stroke: ±100 mm HydroGlide · ±40 mm Assist
• Springs: HydroGlide 42 / 14 kN/m front / rear (stock 70 / 23) · Assist stock
• Pump: engine-driven, 12 cc/rev capped at 20 L/min (HydroGlide) · 7 cc/rev, 16 L/min (Assist); its torque is taken from the engine
• Accumulator: 2 L (HydroGlide) · 1 L (Assist), precharged to 110 bar; pump cuts out at 200 bar, back in at 185 bar, relief valve at 220 bar
• Servo valves: 25 L/min (HydroGlide) · 18 L/min (Assist) at 35 bar drop; 10 ms dead time, 10 ms lag, 15 ms position loop
• Pistons: 28 mm front, 20 mm rear
• Engine off: valve leakage slowly bleeds the accumulator and the cylinders settle back

How it was tuned

• Soft springs, long stroke: stiffer springs for more cylinder force were tried and rejected; the passive ride got harsher and the active system couldn't win it back. Soft springs already ride better than stock on fast bumps, and the cylinders handle the slow body motion.
• Hills vs bumps: at these speeds a bump sequence and the start of a hill are too close in frequency for a filter to tell apart. HydroGlide tells them apart by how long a push lasts: a cylinder held near one end for longer than a bump takes lets go and follows the terrain. Bumps are unchanged; hills keep stock-like ground clearance.
• Fast valves matter: slow valves turned the bump-cancelling into bump-making at 3-4 Hz. Fast servo valves fixed it.
• Measured fairly: every number on this page is against the stock car, same session, same course; Off on a modified car doesn't count as stock.

Installation
Subscribe in the in-game repository, or drop the zip (don't unzip it) into your mods folder (usually %LOCALAPPDATA%\BeamNG\BeamNG.drive\current\mods) and restart the game.
To fit it to any Grand Marshal: Additional Modification → HydroGlide Active Hydraulic Control (with the HydroGlide springs and shocks) or HydroGlide Assist Hydraulic Control.

Known limitations

• Grand Marshal only for now; more cars come in later updates.
• Stock spring and shock visuals (the trunk pump pack uses the vanilla lowrider pump model).
• Fast wheel vibration (wheel hop, roughly 8-12 Hz) rides about like the passive springs. Above about 4 Hz, moving the spring seat mostly moves the wheel, not the body, so (as on real cars) the active system works on the slower body motions.
• Approaching a crest at full throttle, HydroGlide's nose can ride up to about 12 cm higher than stock for a moment before settling.

Changelog
1.0.1: First public release, launching with Gavril: HydroGlide (Glide / Sport / Off) and HydroGlide Assist (On / Off) for the Grand Marshal Luxe, HydroGlide dashboard app, tuning options. Includes HydroGlide's experimental SkyGlide test cars.
1.0.2: HydroGlide dash screen in the cabin (the dashboard app on an in-car display, with a boot logo). The suspension keys now come in their own file, so the Grand Marshal's stock key bindings are left untouched.