Minimizing Aerodynamic Effect for Trailer Towing

[aerohead]

Originally Posted by freebeard

What force would it take to 'shorten' the hitch, when it is under tension from tons of stuff being dragged down the highway? Possibly equivalent to rolling resistance?

We'd have to add the aero drag force of the trailer also.

[ByDesign]

The idea of an extend-o tongue is not bad. Forces are not that high comparatively, so something with a screw, for instance, could accomplish that easily. -- Bigger screw for a bigger trailer / load. Stopping would likely be the highest loads (depending on brake balance). Spinning it in and out is no problem with a good gearmotor because it does not have to happen quickly. Cheap GPS and such would make it pretty easy to tell how fast you were going. If the action happened progressively as speed increased from let's say 30 mph (full extension) to 50 mph (full compression) you'd get the bigger benefits at the higher speeds where it's important.

I find it pretty interesting that you mention this, because I've been contemplating the various aspects of doing this for semi trucks for a long time. There are some dynamic issues associated with changing the hitch load as the trailer comes closer, but I think most of those could be properly compensated by axle position and trailer load management (where you put the stuff in/on the trailer).

[freebeard]

Fixed trailer frame with a nose cone on the trailer that racks in and out?

I always thought the solution would be a tow vehicle with a spherical tail centered on the hitch point. Then a convex nose on the trailer could pitch, yaw and roll without affecting the gap.

[Bicycle Bob]

If that were my rig, I'd wrap it with Coroplast or other sheet material. It would make a bulbous extension over the tongue, as the experiment does, and flow smoothly into the sides. It would be tapered from the wheels to the roof, rather than stepped at the fender tops, to be easy to build, and to provide some extra width that would be carried to near the tail, and then curved in, winding up angled 15 degrees off the center line to minimize wake turbulence. The compound curve at the forward roof line can be done many ways, depending on what you find handy. In the truck wake, it does not have to be very smooth for the air, but the eye would prefer it.

[CrazyLee]

If you add a spoiler over the back of the Pickup it would kick the air over the trailer.
2010 Ford F150 Universal Wings

Also add a tail fairing to the back of the trailer.
Northeast trucking company adds tail farings to cut fuel | ZDNet

AirTabs work too.
Airtab | Aerodynamic Fuel Savers | Welcome

[aerohead]

From what I've seen,it takes a wind tunnel to figure out a proper geometry for a truck spoiler.
The following is a set of very degraded TV images I photographed on pause,from a VHS recording of a series of tests conducted by Texas Tech that I was given in 1990.
Every configuration has separation or overshoot except the deep,bulbous trailer nose at bottom right.
This is a tough DIY project with a limited budget.

[bluebunny]

here is a aero camper trailer I am designing for tow behind a VW Golf cheater diesel...

[bluebunny]

[aerohead]

Looks like an easy pull.And not a killer,fabrication-wise.

[aerohead]

Originally Posted by bluebunny

Attachment 19296

Without adequate testing,there's a risk that the flow will overshoot.Some of the angles of successful fairings are counterintuitive when you see them in action.
NASA would say the rooftop spoiler would be okay if you were also going to do the gap-filler again.