I HATE the Wind - Aero Semi Trailer Blew Over

[Shepherd777]

Originally Posted by aerohead

With less packaging efficiency,an Airstream trailer,with its generous corner radii allows for attached flow over and around, with even a smidegeon of pressure recovery on its leeward side before separation occurs,generating half the wake volume.

That's the problem we have trying to make freight hauling rigs fuel efficient. The trailers have to be square to haul the freight. The shippers require the most cube volume as can be had from a 53' trailer. Sure, there are 45,000# loads that only sit 4' high off the floor and "gross-out" weight-wise, before they "cube-out". But one cannot survive in the freight hauling business by not having a trailer that will haul max cube.

If you've ever seen the completely dopey, completely impracticable Euro trucks with the whale-back trailers, forget it. You would get laughed-off a shippers lot (and everywhere else) pulling in with a trailer like that here in the U.S. Not to mention the fact that you couldn't even back up to a loading dock with it.



We need to take a 13'6" high, 53' long, 102" wide rectangular box and make it as aero as possible within the confines of the law.

Aerohead - I will be adding a new thread later today or possibly tomorrow regarding the engine hot air exhaust vents on the new truck. I am sure they will be controversial. I am concerned with the air staying attached at this area. I would appreciate your input on this subject. More to follow. Thanks.

[euromodder]

Originally Posted by Shepherd777

If you've ever seen the completely dopey, completely impracticable Euro trucks with the whale-back trailers, forget it. You would get laughed-off a shippers lot (and everywhere else) pulling in with a trailer like that here in the U.S. Not to mention the fact that you couldn't even back up to a loading dock with it.

Donbur trailers ?
They don't reduce the volume compared to regular trailers.
There's actually more volume in them, though i'd think it's hard to use.
They use the UK regulations (which allows higher trailers than continental Europe) to make their hump-backed trailers more fuel efficient, yet still fitting loading docks.

Of course you could build a higher trailer with the same height overall as the hump, but apparently that's not always what's needed.
They also build double-deckers with flat roofs, it just depends on what the customer needs.

[Shepherd777]

Originally Posted by euromodder

Donbur trailers ?
They don't reduce the volume compared to regular trailers.
There's actually more volume in them, though i'd think it's hard to use.
They use the UK regulations (which allows higher trailers than continental Europe) to make their hump-backed trailers more fuel efficient, yet still fitting loading docks.

euromodder -

No offence to you folks or the rigs on the other side of the big pond was intended. I was not talking about those Donbur trailers, but the MAN trailer in the attached pic of my post. But even that Donbur teardrop box van trailer would reduce volume considerably here in the U.S.A. I did specify about them being "completely dopey, completely impracticable" using them here in the U.S. Thousands of interstate highway underpasses here are only 14' high. And we run trailers with a maximum height of 13'6" for 6" of clearance between the top of the trailer, and the bottom of the underpass. So if someone was to use a trailer like that MAN or the Donbur teardrop, volume would be adversely affected as the limiting factor would be the height of the trailer driving under a bridge. So if one slopes down the rear of the cargo carrying part of a trailer here in the U.S., there is no way it will carry the same volume. And while one could certainly back up to a loading dock, and load and un-load that Donbur teardrop, one could not with the MAN trailer.

My 53' dry van has a 110" inside height and a 101" inside width. So it will carry 4089 cubic feet of cargo. To still be able to drive under the bridges, and slope down the cargo carrying rear, it would carry considerably less.

[euromodder]

Originally Posted by Shepherd777

But even that Donbur teardrop box van trailer would reduce volume considerably here in the U.S.A. I did specify about them being "completely dopey, completely impracticable" using them here in the U.S. Thousands of interstate highway underpasses here are only 14' high. And we run trailers with a maximum height of 13'6" for 6" of clearance between the top of the trailer, and the bottom of the underpass.

That's the kind of situation we have here on the old continent, with height being more restricted than in the UK, so we use flat tops.

I can't see the more boat-tailed MAN drawing make it to practical hardware either, unless they get a relief from the legal length restrictions and put a lifting mechanism on the top slope, with an hydraulic ramp making up the lower slope.

Even then, the extra 4-5 meters in length aren't going to work for everyone.

[b13bliss]

It seems that a major redesign is required to significantly reduce cross-wind tipping, but any change in shape is going to adversely affect the cargo-carrying capacity or overall dimensions. I would suggest that the top two feet of the trailer be retractable vertically via pnuematics in the supports. The skin would have to overlap some to provide a seal at full height and to allow movement vertically. The supports would have to be slightly bulkier, but the cylinder could be small and protected by the support itself. I imagine the back door would need to be the two feet shorter with a vertical flap for full height access. Thus when the full height isn't needed, the trailer could be shortened at the push of the button, and the wake and side loading in crosswind could be reduced almost 15%. The trailer would only need to be at full height when it is loaded to the top, so that should help with tipping. I can't imagine it not saving fuel when in the lowered position, and it may be enough to offset the added expense. It would be interesting to see what your flow simulation would predict for drag reduction.

[Ultra-Orange]

For leaving the rig parked I'm thinking rig a quick release. The Diagonal braces that run from the floor of the trailer to the skirt could be braced with a vertical brace that runs from the end of the brace straight up to the floor of the trailer. then run a piece of "L" channel down the length of the skirt so it presses against the braces when the skirt is down. Put one quick release at either end of the channel, possibly connect them so that both quick releases work from a single lever (though I cant imagine trying to put the skirts up with just one person). Since the skirt already has a hinge the job is already half done. Just need a fastener to hold the skirt vertical and done!

Now this may be more engineering/work than your interested in sinking into your new trailer but thought Id toss in my 2bits