L28 Powered, Hydraulically Driven Rock-Crawling Buggy

[blue72]

This was in a recent issue of Four Wheeler Magazine that I picked up.

 

 

The basics:

Custom built rock buggy designed and fabbed by Jeff Friesen, a graduate of Cal Poly. All square and rectangular tubing, laser cut from flat sheets and hand TIG'd.

L28 engine from a '78 280Z is rear mounted, propane fueled and drives the hydraulic pumps, alternator (to drive winch, electric fans on hydraulic fluid and engine coolant radiators), air compressor.

Suspension has equal length a-arms, monotube shocks, and airbags on all corners allowing individual corner leveling over most any obstacle (up to two feet of adjustment).

Two hydrostatic pumps, one for each the front and rear end. Fluid is pumped in series through two Eaton drive motors.

Front and rear hydraulic steering rams with separate pump.

 

Even if rock crawling and / or rock buggies aren't your thing, anyone can appreciate the engineering and ingenuity that went into this build. Plus, even though the wheels are driven hydraulically it still has the heart of a Datsun.

 

Here's a link to the 4 wheeler article: http://www.fourwheeler.com/featuredvehicles/129_1007_hydrostatic_hydrodynamic_rock_buggy/index.html

 

His build thread at pirate4x4.com: http://www.pirate4x4.com/forum/showthread.php?t=763311&page=7

Edited September 13, 2010 by blue72

[Tony D]

Back in the 80's there was a guy running the competitive mudbog drag circuit with a black VW Powered AWD car called "The Widowmaker"...

The rest of the competitors complained and protested because he thought to use Hydraulics to run motors on the front wheels in conjunction with the conventional transmission out back so he could alter how much power went to the fronts. When he would start bogging from rear drive only, he slid the lever and had the fronts dragging the mudbuggy along.

 

Sanctioning judge had a real succinct answer for the protesters: "You guys are running Blown Hillborn Injected V8's and you are whining because you can't beat a little Beetle-Bug four-banger running some hydro pumps on the front wheels? Give me a break! Get competitive or give it up!"

[ModernS30]

Its now got a V8 in it. Look through the build.

[blue72]

What!!??!!!?!?! Pulling out an L series motor to swap in a small block Chevy? That's blasphemy!

 

 

 

Is there a smiley that just denotes sarcasm?

[ModernS30]

What!!??!!!?!?! Pulling out an L series motor to swap in a small block Chevy? That's blasphemy!

 

 

 

Is there a smiley that just denotes sarcasm?

 

That is actually the issue. There wasn't enough power in the little L28 for it to break 14mph.

[Tony D]

What kind of efficiency was that guy getting? 14mph? The Widowmaker was running bogs at well over that speed with VW Power!

 

He must have some hellacious leakage on that hydrostatic drive setup if an L28 won't power it.... especially with it's steady-state ability at higher revs!

[goodoldjam]

Reading through the build it didn't sound like he was switching because the L28 wasn't enough to go fast. Sounded like he wanted to be able to operate it at lower rpms and have that sound. Actually from the specs sounds he gutted a forklift.

Top speed is apparently 22mph as stated on fourwheeler link and weighs 4300lbs with the L28.

From the specs it doesn't sound like it's going to go much faster and why would he be focused on going faster.

Top speed 22 MPH

Pumps Displacement 2.81 CI/REV

Pump Max REV 4000 RPM

Pump Max PSI 5000

Planetary Ratio 30:1 Rated @ 50,000 Inch/LBS

Drive Motor Displacement 2.48 CI/REV

Drive Motor Torque 156 FT/LBS

Planet Torque 4687 FT/LBS

Drive Motor Speed 4532 RPM

Planet Speed 151 RPM

Tread Speed 22

Draw Bar Pull 4686 LBS

 

Where did it say it only goes 14mph.

"It is destroying my backyard and scarring the animals. I have been testing it and getting it set up and learning how to drive it. I will post up changes I have made, but for the most part it needs to be rev'ed up and ease the joysticks like a aircraft. It will jump and stop like a bull if you get crazy with the controls. It has no cooling issues so far. The torque and speed are about dead on with the design specs. Videos once I learn how to drive it and hit a trail. It is big, loud, and fun."

 

I don't know why you would need to go faster than 22mph, imagine what happens when he lets off the controls going that fast.

Edited September 13, 2010 by goodoldjam

[blue72]

What kind of efficiency was that guy getting? 14mph? The Widowmaker was running bogs at well over that speed with VW Power!

 

Was this Widowmaker you've referenced saddled with 30:1 planetary reduction boxes on each wheel?

[goodoldjam]

Was this Widowmaker you've referenced saddled with 30:1 planetary reduction boxes on each wheel?

 

Yeah the whole point was torque, it probably drives the same as a small skid steer. You need to be gentle with the controls.

Which if anyone has driven one going 10mph down the road, they would know that feels fairly quick. If you let go of the controls it basically locks up and feels like your going to flip. Same if you throw the controls forward your front wheels come off the ground.

 

The important spec is max pump speed, If he never exceeds that he won't go any faster.

This is more a piece of machinery, get in and throttle up and leave it there.

I think his choice to go to a V8 was more of a cool factor than anything else, it may bog a little less under load. It's like putting a V8 into any small hydrostatic machine, it's not going to add much.

 

Though there are hydrostatic street sweepers with variable pumps and wheel motors that can reach highway speeds. I've been told that if you let off the treadle to fast on the highway it will about throw you out the windshield.

 

Difference between Tony's example was the fact that it had a actual transmission and was driving a separate pump. It was a mudbog and this is a crawler, though I totally agree that the L28 was more than enough.

Edited September 13, 2010 by goodoldjam

[randy 77zt]

i used to work on street sweepers that were hydrostatic drive .pump and drive motor were made by sauer danfoss.when you let off the gas it stops quick.a crawler with hydraulic motors at all 4 wheels would work better than axles.military hummers have gear reduction boxes at the wheels.these would work good with hydraulic motors on them

[Tony D]

Guys, you are talking to the guy who retrofitted the Japanese Self Defense Force MJ1 Bomblift with chrome engine tins and dual carbs. No suspension, hydrostatic drive, and rear drive-wheel steering. The guy who beat a 'he was jumping the bomblift driving down the flightline sir! apprehension by letting the officer drive the thing and determine for himself if it was possible (he determined it was NOT and indeed it WAS an 'optical illusion' as I convinced them it was (yeah, I was jumping it...) Look up USAF Munitions Handler, MJ1A and see what I'm talking about... The Japanese had VW industrial engines while we were saddled with (in the old days) Wisconsin MV4HD air cooled V-4's. Later we got diesels. I prefered the VW setup. Man THAT one cooked!

 

It's all about how you set it up.

 

The Widomaker, btw, was running dual hydrostatic motors off a single pump---one driving each wheel up front. Likely it was driving at some predetermined ratio determined by pump/motor size ratio, avaialble flow, and horsepower. Like I said, it was lever-controlled for the split from zero upwards, so that tells me it was likely a variable swashplate arrangement like the Sunstrand Dennison Pumps (or Hydromatiks) used in aircraft hydraulic test stands.