Still trying to learn stuff.........box cavity?

[hat_man]

Wasn't trying to mock. I've had that pic on the computer for years. Always wanted to post it here.

Not sure I could get the tonneau cover to close with a vertical extension and a pivoting mechanism. I'll have to start with cardboard and see what I can come up with. Not saying it won't work, I just can't see it in my mind. Time to stop at the appliance store see if they have any boxes.

[slowmover]

A fully-boxed tail on a 53’ van is worth having. It’s right at four-feet deep.

But with this caveat: increasing the length of the sail ALSO increases the leverage of wind against the vehicle. This is a serious concern. The crosswind has a longer lever to use.

So much so in this case I know drivers who otherwise run them WON’T when empty or nearly so (I can load 45k in the box. Today’s load is 7k. That’s “empty”).

Moving the trailer tandem axles rearwards can offset this effect (wind forces increase drastically every foot rearwards as they can’t escape the squared roof edge), but there’s a legal limit to how far back. AND it makes the trailer more difficult to get through every turn or curve with the increase in distance from the Drive Axles (Ackerman angle).

Were I the trailer owner I would have both skirt & tails (plus the nose cone arrangements we’ve seen to collapse the tractor/trailer distance from one another). The MPG benefit is obvious, and given a regular loading (25k plus) it makes handling the truck EASIER throughout the day. Wind problems are reduced, overall. But it’s also a new caution on a windy mountain pass. In a rainstorm squall line. Etc.

The pickup half tonneau looks nice. But the Aerolid is where to start. Even a simple one (as on a Dodge Cummins owners truck in aluminum sheet) provides an idea of benefits.

For a city box truck, or for a pickup, access to the box/bed has to be weighed against complexity in a tail. The forces at work back there are high. To replicate the industry TRAILER TAIL is no small matter given a cab-height bed topper.

Which is why you now see Coanda devices being used on the trailing edge of vans. Less problem and MOST of the benefit.

Tails are so 2014. (Ha!)

Obama-Age Obsolescence.


Now, for my pickup it’d be front airdam and side skirts. The rear cavity “ought” to be something I can dismount. A hitch-mount carrier with an extension (roof & sidewalls) that extends upwards from a transport case to meet my LEER bed topper roofline.

How to treat the exit UNDER that (under truck body) is where a big question mark exists (for me).

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[freebeard]

One thing I've noticed in this discussion (Ecomodding Central: Green Grand Prix modding thread) is this part from a Prius:


https://ecomodder.com/forum/showthre...tml#post603668

Compare to the High Momentum mudflap called out here:


The Prius part seems to be a much reduced version of the truck mudflap. Maybe something half-way between the two?

[Tahoe_Hybrid]

Originally Posted by Fat Charlie

Everything I know about aerodynamics I learned on Ecomodder.

To me a box cavity has always been a fast and dirty boat tail. Not perfect, probably not good looking, but effective. I've seen some graphics of pretty ones that just needed some skin to be real boat tails, but even one panel hanging out back coming close to the template is good.

I can't find the post, but this was on an early version of The Anal Probe:


The setups on the backs of 18 wheelers these days are a good example. Crappy boattails, but way better than the unmodded truck:



It's not pretty, it's not optimal. It's a box.

those are actually illegal anyways in most states

and if the cop is a real jerk he will cite you for a oversized load without permit as well



I really love tailgating those the FE is a bit higher compared to a normal 18 wheeler truck

[MeteorGray]

Why would the trailer box-tail be illegal?

Do they cause the rig to be too long for maximum specs or something?

[aerohead]

Originally Posted by Tahoe_Hybrid

those are actually illegal anyways in most states

and if the cop is a real jerk he will cite you for a oversized load without permit as well



I really love tailgating those the FE is a bit higher compared to a normal 18 wheeler truck

It used to be that any truck in the USA could run up to a 5-foot tail,without penalty,as a matter of US energy policy.What a shame if they've changed that.

[slowmover]

They’re in no way illegal. That’s flat funny.

Truck regulation is basically road restrictions. Think turns and curves where rear overhang intrudes into other lanes. Rare; mainly mountain roads. These roads, but not those; etc. That “takes care of” OAL limits.

And they work well. I had a slight tailwind out of Amarillo yesterday at 79,300-lbs. Stayed above 10-mpg with skirt & tails almost all the way to OKC at 67-mph.

This morning when I finish this I have to pull the tractor out from under the 59k trailer to re-grease 5th wheel. Had to initially shove my way under. Fighting any crosswind, road camber changes, ruts, etc, gets old.

Will buy fuel and then also move trailer tandem axles forward slightly and also move the 5th wheel itself. End result will be FAR fewer steering inputs and/or degree & duration thereof.

Mechanical condition always trumps aero. One has to set the conditions for it’s performance addition
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