HydroDynamic Rock Buggy

Hydrodynamic Rock Buggy Front Steering Wheel

Driving the HydroDynamic Buggy
Friesen designed his buggy so that he could rest his arm comfortably on the center console and easily operate the hydraulic pump levers that send power to the wheels. Pushing the self-centering levers forward results in forward motion, and pulling them rearward results in reverse motion. The left lever controls the front wheels; the right lever controls the rear wheels. He also has fingertip control of the air suspension switches mounted on the center console. The green buttons inflate each bag and the red buttons deflate each bag. He says he levels the vehicle by looking at the angle of each A-arm. The steering wheel controls steering to the front of the vehicle as with a normal vehicle.

Directly above the steering wheel is a left/right toggle switch that Friesen can operate with his left hand. This lever operates the rear steering. The other switch is the engine governor/rpm control.

Suspension Adjustability
The HydroDynamic Buggy has an incredible amount of suspension adjustability. This allows Friesen to adjust for off-camber situations as well as to lower the center of gravity or increase ground clearance at will. We broke out a tape measure and conducted a very unscientific test (on slightly uneven, rocky ground) with the limiting straps engaged and stops installed in the airbags and found that the backbone of the vehicle (measured at the rear of the vehicle) could be as low as two inches from the ground or as high as 19 inches. The bellypan ranged from 14 inches with the airbags completely deflated to 31 inches completely inflated.

Hydrodynamic Rock Buggy Dual Propane Tanks

Dual propane tanks feed the 280Z engine. Propane runs through an Impco 225 propane mixer on its way to the engine. Above the propane tanks is a custom stainless-steel air tank that is used for the air suspension.

Dual propane tanks feed the 280Z engine. Propane runs through an Impco 225 propane mixer o

Specifications
General
Owner/Hometown: Jeff Friesen/Kingsburg, California
Vehicle/Model: HydroDynamic Buggy
Estimated value: N/A

Engine
Type: Datsun 2.8L I-6
Aspiration: Impco 225 propane mixer
Output, hp/torque (estimated): 170/150

Drivetrain
Transmission: Dual Sauer Sundstrand M46 hydrostatic pumps
Transfer Case: N/A

Suspension
Front: Independent, equal length A-arms, Slam Specialties airbags, Fox 2.0 shocks, limiting straps
Rear: Independent, equal length A-arms, Slam Specialties airbags, Ballistic 2.25 shocks, limiting straps

Axles/Differentials
Front: Eaton drive motors coupled to Auburn 28:1 planetaries, PSC hydraulic steering
Rear: Eaton drive motors coupled to Auburn 28:1 planetaries, PSC hydraulic steering
Ring and pinion: N/A

Wheels/Tires
Wheels: 20x8 custom steel double-beadlock wheels
Tires: Goodyear MVT 395/85R20 FW

The front and rear steering is powered by PSC double-ended hydraulic rams. These rams have a 3-inch bore. The hydraulic steering has its own pump, which is powered by the same shaft that powers the vehicle's other hydraulic pumps.
The front and rear steering is powered by PSC double-ended hydraulic rams. These rams have
The steering arms are made from 1 1/2-inch-diameter solid aluminum. On each end are 7/8-inch spherical rod ends.
The steering arms are made from 1 1/2-inch-diameter solid aluminum. On each end are 7/8-in
A Warn 12,000-pound winch is mounted on the front of the buggy. "A hydraulic winch would be dead if the buggy was dead. Electric was the only way to go for backup," Friesen notes. Both the front and the rear of the buggy have dual clevis mounts to aid in recoveries.
A Warn 12,000-pound winch is mounted on the front of the buggy. "A hydraulic winch would b

Powering the buggy is a propane-fired 2.8-liter I-6 from a '78 Datsun 280Z. The engine is rated at 170 horsepower and 150 lb-ft of torque, but Friesen calculates that at the lower rpm he's using, it's making about 125 horsepower and 125 lb-ft of torque. Friesen says the Delco 150-amp alternator is a Freightliner big-rig application unit that is rated at 10,000 rpm. He says the pulley size is calculated to run at about 9,000 rpm when the engine is at 4,000 rpm. This allows for maximum cooling and output so the alternator can put out a full continuous 150 amps without getting hot and burning up. The buggy uses a pair of Orbital batteries. Friesen designed the battery and charging system to be able to handle the task of recovery (i.e., extended winching) in case of hydraulic failure.
Powering the buggy is a propane-fired 2.8-liter I-6 from a '78 Datsun 280Z. The engine is
The job of keeping the hydraulic oil cool falls to a Thermal Transfer radiator with 17-inch electric fan from a Ford Crown Victoria (pictured on right), while engine cooling is handled by a Toyota Corolla radiator with dual electric fan setup.
The job of keeping the hydraulic oil cool falls to a Thermal Transfer radiator with 17-inc
The cab of the buggy has a pair of PRP seats, a dirt track-style steering wheel with spinner knob, and a custom center console that houses Auto Meter oil pressure and engine temp gauges as well all of the buttons that control the airbag suspension. Further, there are buttons and switches for engine starting, cooling fan control, compressor control, lighting, and engine governor. From the cab, Friesen has a clear view of the trail, thanks to clear Lexan panels.
The cab of the buggy has a pair of PRP seats, a dirt track-style steering wheel with spinn

Friesen can monitor the hydraulic oil temperature via a custom-made digital hydraulic oil temp gauge (arrow) that is mounted directly to his right between the PRP seats.
Friesen can monitor the hydraulic oil temperature via a custom-made digital hydraulic oil
Here you can see a view of the single rail that makes up the "backbone" of the chassis assembly. Note how clean all the welds are.
Here you can see a view of the single rail that makes up the "backbone" of the chassis ass
A pair of custom stainless-steel tanks houses the hydraulic oil. Each tank is designed to trap oil in the suction area and keep air bubbles at the top of the tank. The shape of each tank and the pickup position keep the air pocket away from the suction port when sloshing around. Further, the tank shape makes the oil take the longest route possible back to the suction port so the oil has a chance to dwell and let the bubbles work their way out before being sent back to the pump.
A pair of custom stainless-steel tanks houses the hydraulic oil. Each tank is designed to