Trailer Talk

Using Archimedes’ Lever Principle to Help Propel a Tractor-Trailer

Multiplying the tractor's pulling force could reduce required input and save 80% in fuel, this concept's inventor believes.

September 19, 2014

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Archimedes, the scholar and mathematician of antiquity, was quoted as saying, “Give me a place to stand and a large enough lever, and I will move the earth.” That’s debatable, but some pretty big and heavy things can be nudged into motion with a lever – and trailers are among them, says an inventor in Ohio.

Herman Mitchell, a former U.S. Air Force electronics technician, has learned engineering principles and methods of calculating the physical forces involved in vehicle dynamics. He has devised what he calls the Easy Go Trailer, which multiplies a tractor’s pulling power with levers placed at the trailer’s axles.

With a current trailer, the tractor’s fifth wheel pulls against the kingpin, which tugs along the rest of a trailer. The pulling force is nowhere near the maximum legal combination weight of 80,000 pounds or the trailer’s weight of 62,500 pounds, which stays on the rig’s suspensions, axles and wheels. So the pulling force needs only to overcome rolling resistance of bearings and tires, and aerodynamic drag as the rig speeds up. Typically the pulling force on a flat highway will be about 500 pounds for the trailer and 140 pounds for the tractor, Mitchell has calculated.

If that pulling force is multiplied by levers, power needed to move the trailer is eased, and fuel economy could increase by 80%, he says. Here’s how it works:

1. Floating kingpin  2. Linkage arm  3. Carrier bearing assembly  4. Front and rear levers  5. Trailer chassis
6. Tire-wheel assembly  7. Landing gear  8. Suspension  9. Axle  10. Input pivot (top of lever) 11. Fulcrum pivot at axle
12. Output pivot at bracket mount
1. Floating kingpin  2. Linkage arm  3. Carrier bearing assembly  4. Front and rear levers  5. Trailer chassis 6. Tire-wheel assembly  7. Landing gear  8. Suspension  9. Axle  10. Input pivot (top of lever) 11. Fulcrum pivot at axle12. Output pivot at bracket mount

Tops of the levers – two on each axle – are linked by a long rod to the trailer’s kingpin, which slides or “floats” slightly. As the kingpin is pulled by the fifth wheel, the rod tugs against the lever tops and the axles, to which the levers are attached. The axles form a fulcrum for the levers, whose bottom ends pivot in brackets beneath each axle; the levers now push against the axles.

The long ends of the levers above the axles are about five times the length of the short ends at the axles and pivots, so the mechanical advantage is 5 to 1. Therefore, the 500 pounds of required pulling force at the axles is reduced to 100 pounds, and an input force of 110 pounds will cause the tractor and trailer to move away from a stop and accelerate.

A driver would notice how much lighter the trailer feels, and he could ease up on the foot feed. Or the engine’s output could be reduced electronically or by downsizing. Either way, considerable fuel would be saved.

The vertical space beneath a trailer’s superstructure limits the possible lever length and therefore the mechanical advantage’s ratio, Mitchell says, so it comes out to be 5 to 1. There’s even less space beneath low-slung trailers, like drop decks and lowboys, but he has other devices in mind that, with shorter levers, would provide the desired multiplication of force.

The floating kingpin shouldn’t be a problem during braking, but if it is, he figures a locking mechanism could stop movement during those events. A regular steel-spring or air-bag suspension would be secured normally to the axles, and would provide their normal vertical articulation and cushioning. Levers would move with the axles, and the apparatus connecting the levers to the kingpin-linking rod would swivel to allow movement.

So, that’s the Easy Go Trailer concept, in plain English. Mitchell describes his patented design in engineering terms, which he’d be happy to share with trailer manufacturers and others who see its validity and potential. He once built a model using bicycle parts to demonstrate it, but no longer has it. I've suggested that he make another one to show that it physically works.

While his levers might not move the Earth, they might help reduce fuel burn enough to save it from excess greenhouse gases. Contact Herman Mitchell at Power Products LLC, 937-235-0448 or [email protected].

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Author Bio

Tom Berg

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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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