Reducing the form air drag of truck trailers can be accomplished better by reducing the size of the trailing edge than increasing the size of the leading edge (such as using wind deflectors).
Leaving the side walls of the trailer intact, hinge the roof at a point maybe five feet from the front edge. The roof then slides down in back to a point a couple of feet above the floor of the trailer. The rear door could be a roll-up type that withdraws parallel with the roof.
This will reduce the form drag of the trailer when carrying heavy loads, which are located in the front of the trailer, and when the trailer is empty. That covers a lot of time! With partial loads the roof can be lowered to a spot just above the cargo. A horizontal brace joining the rear top corners of the sides will minimize shaking and movement of the sides.
A rubber gasket on either side of the roof in contact with the interior side walls will mitigate the entry of water. Most of it will run off the after end of the trailer.
It doesn't take much of a reduction of drag to amount to a significant fuel savings for the trucking industry. Here is a possible contribution.
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The way I am understanding what you are saying, it would also reduce the amount of cargo that can be carried. One would have to figure would you save that much fuel and pollution by running more trucks to transport the same cargo.
You misunderstood the concept. The roof drops down to the level of the cargo in the rear of the trailer. A teardrop trailer would be difficult to load, carry less, and nobody would buy one. You might be surprised how much empty space there is in most of the trailers on the road. Some are even empty!
I think that this idea has merit, but I'm curious how you would design the rear-doors of the trailer to be a variable height?
I think if you made full-height doors that could drop-down into the rear of the trailer, to approx the level of the cross-bar bumper, you could do a two-foot drop, but other than that, I can't see how you could ever get all the way down unless your doors are canvas.
Also, I think the hinge at a point five-foot from the front might not be as advantangeous as making the whole shape of the trailer into a low-drag body, then hinge it at half-way and that section is your door. Sort of like an opening nose on an airplane. This way wouldn't be adjustable, but you'd always have a 'pointed' boat-tail for drag reduction.
i believe that the idea for the door is to use a roll-up style door, not hinge type doors. this allows it to be set to any height. I think this could be a very good idea, but i am curious as to how you would propose raising and lowering the roof, as it would most likely weigh over 200 pounds, and need to be lifted far above the reach of a man standing at the back. would this mean installing a hydraulic, pneumatic, or electric control system. im sure this would not be terribly difficult, but when all modifications are considered, do you really believe that this system would be cost-effective. most of these trailers are passed around so much that nobody will even claim them and pay for the maintenance, nevermind paying significantly more for the new ones.
Your roll-up door makes perfect sense. Don't know why I had a block against that.
The problem of raising a more that X00-pound roof really isn't that big of a deal--Initially, I'd suggest springs or gas-strut, but as you said, pneumatic or hydraulic would work, too.
But truthfully, most overhead doors already lift more than a couple-hundred pounds--they're just offset by springs.
The complexity issue is certainly the issue. It's not clear how much fuel you can save, so the equation is hard to balance with Any money spent on aerodynamics.