Trailer Talk

Powered Trailer Axle Provides an Off-Road Boost

Run off the tractor's wet kit, the hydraulically driven axle adds traction in rough conditions and can eliminate 4x4s used by some European operators.

November 4, 2016

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The 4x2 tractor can't get the rig moving on a slippery upgrade, so the trailer's powered rear axle provides a boost. Photo: Tom Berg from SAF-Holland video
The 4x2 tractor can't get the rig moving on a slippery upgrade, so the trailer's powered rear axle provides a boost. Photo: Tom Berg from SAF-Holland video

Powered trailer axles are unusual, even in Europe where they do things differently with trucks than what we do here in North America. That’s why a new product from SAF-Holland, a hydraulically driven trailer axle, might find acceptance with operators over there.  

The predominate Class 8 configuration in Europe is a single-rear-axle, 4x2 tractor pulling a three-axle trailer. Tractors, therefore, cost and weigh less than our common 6x4s that pull a tandem-axle trailer.  The 4x2 works fine on pavement, especially with a locking differential, but a single drive axle on end-dump rigs sometimes can’t grab enough traction while off road.

So such operators often use 4x4 tractors, according to Markus Heuser, Germany-based director of global marketing communications for SAF-Holland. Of course, a front-driving axle adds weight and cost to the tractor.

Thus the company’s  “SAF Trak” axle. It’s powered from the tractor’s hydraulic wet kit that tips the trailer body. On the trailer, two Poclain hydraulic motors, one at each axle end, turn the wheels to help get the rig moving in slippery conditions. A driver pushes a switch on the dash and compressed oil is sent to the motors to get the traction boost. It works only at low speeds.

As you’ll see in the accompanying video, a hydraulic motor is a 10-cylinder radial, like old aircraft engines. Heuser says the hydraulic tank on the tractor would need to hold a few more gallons of fluid, and of course, the trailer needs to be set up with hydraulic lines extending to the powered axle. 

There are no plans to bring the SAF Trak axle here because our 6x4 tractors with twin-screw tandems seem to have enough traction for on/off-road work. But he didn’t say “never,” either.

Comments

  1. 1. Frank Owens [ November 24, 2016 @ 04:12AM ]

    "A driver pushes a switch on the dash and compressed oil is sent to the motors to get the traction boost." Doesn't this author know that you can't compress a liquid

 

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Author Bio

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Tom Berg

Senior Contributing Editor

Journalist since 1965, truck writer and editor since 1978. CDL-qualified; conducts road tests on new heavy-, medium- and light-duty tractors and trucks. Specializes in vocational and hybrid vehicles.

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