All That's Trucking

Closing the gap

May 10, 2011

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When you see drawings or mockups of futuristic trucks, one of the things you'll notice is there's virtually no gap between the tractor and trailer.
That makes for a very cool-looking concept vehicle, but how do you achieve that in the real world while still being able to back the rig around tight corners?

At the ATA's Technology & Maintenance Council meeting earlier this year, I got to see a demonstration of one way it could be done, courtesy of Jost International, which demonstrated its new Smart Gap System.

Gregory Laarman, vice president of engineering, explains that the idea is to close the gap between the tractor and the trailer so the wind continues over the top of the trailer rather than getting caught in the gap, where it creates aerodynamic drag.

The system consists of a fifth wheel slider assembly, with hydraulic cylinders and actuator controlled by sensors and an ECU. A hydraulic pump and accumulator actually move the fifth wheel. The system senses when it is safe and more fuel efficient to close the gap between tractor and trailer at certain speeds and under certain conditions. There are several positions, based on the speed of the vehicle. The closest brings the gap down to 24 inches.

When conditions indicate the need to return to a more conventional position, as in a turn or an emergency maneuver, the system automatically does so, quickly and without driver involvement.

Laarman explains it to me at TMC:

This animation from Jost shows how it works:

And lest you think that anything can be done with animation, here's a video showing it in action on a real rig:

The platform is the Jost Pro Tech integral angle inboard style slider assembly, which offers a 100-pound savings over conventional sliders, Jost says. In addition, the SGS assembly incorporates a cab actuated air release for the kingpin locking mechanism, advanced technology low lube liners on the top plate, and the Jost Lubetronic system to provide small amounts of lubricant automatically to friction points.

Jost officials told me they're in discussions with truck makers about refining and offering the new system.

One question I had later was, what effect would that have on axle weight regulations? Carroll told me, "We are working through the front axle considerations with some partners."


  1. 1. Monongahela Misfit [ May 16, 2011 @ 01:23PM ]

    I hope some of the Partners that Jost is working with on Axle Weights with are DOT folks at either State or Federal level. Outside of regulatory oversight I think this system could do a lot to help reduce our overall fuel consumption.

  2. 2. Rich Carroll [ May 16, 2011 @ 01:59PM ]

    When you look at the design of the futuristic truck-trailer combinations you will see another reality which is the inability for the operator to acccess the fifth wheel, landing gear, pnuematic and electrical connections. This will drive the industry to totally automated coupling systems complete with sensors indicating safe coupling. Fifth wheels are "moving" from the basic function of a lock between tractor-trailer to an integrated solution for fuel efficiency and operator safety.

  3. 3. Monongahela Misfit [ May 20, 2011 @ 02:31AM ]

    Are You suggesting that we wont be getting grease all over our coveralls while checking the 5th during a full pre-trip in future? I like that future.


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Author Bio

Deborah Lockridge

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All That's Trucking blog is just that – the editor's take on anything and everything related to trucking, with the help of guest posts from other HDT editors. Author Deborah Lockridge's career as an award-winning trucking journalist started in 1990.


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