inflatable drag-reduction gadget

[phantom power]

I was watching 2010 (the movie) one day, and I got this idea from watching those inflatable atmospheric-braking sheilds.

A lot of the aerodynamic drag on a vehicle is due to the fact that our vehicles aren't shaped like a tapered cone in the rear. In fact, most vehicles are flat in the back. Just about the worse possible configuration, in terms of creating drag.

But they are flat for a reason. Making them cone-shaped is kind of hard to work with in terms of getting things in and out.

But what if we installed cone-shaped, inflatable balloons on the back of a vehicle. Like a semi. When the vehicle is stopped, you can deflate them, and have easy access to the doors in back. When the vehicle is moving (maybe at some minimum speed), you can inflate the balloons, and suddenly, the back of the vehicle becomes aerodynamic!

It might add a few feet to the length of the vehicle, but not necessarily that much. Especially for something like a semi.

Am I smoking dope?

[BlueEyedSon]

1. The cone would have to be fairly rigid, otherwise it would flap like crazy

[phantom power]

3. yes, it would. I don't know how much pressure it would require.

I picture the balloons being mounted pretty strongly against the doors, so they'd have plenty of support on that side, at least. And since they'd be round, they ought to be reasonably strong.

I say "cone", but I'm not exactly thinking of a cone, with a point. More like a half-sphere, actually.

[ret5hd]

2. we don't know...are you smoking dope?

[phantom power]

4. I'm not playing "gotcha". no-sir, not playing "gotcha" with the press...

[Alpharetta]

5. a decent idea

But FYI aero drag is not always intuitive. Surprisingly, pickup trucks get better highway mileage when the liftgate is UP, for example. Somehow, the liftgate creates a bubble of air above the truck bed which makes the truck slippery.

One more note: some vehicles already have airfoils which activate and extend at highway speeds. Some Porsches, for example. There may be value in examining their approach.

[flamin lib]

6. Ford has experimented with channeling air through vents to

form a cone behind the vehicle. The early Taurus was a test bed. They used high pressure fans and body panel vents to make a swirling cone behind the vehicle. Styling, noise levels and poor performance in high cross winds killed the concept.

[lapfog_1]

7. Plastic detachable tail drag reducers already on the market.

not the inflatable type as you describe.

I was at NASA when they were doing the initial wind tunnel
tests of full sized tractor trailer rigs (in the 40 x 80 test
section tunnel) and trying different "nose cones" (aerodynamic
additions to the top of the tractor). Saves about 7 to 10 percent
on the fuel... that savings alone is enough to fully fund NASA.

[phantom power]

8. yeah, like that, but for the back of the trailer.

[lapfog_1]

9. I thought that is what I was saying... hence the term "tail drag"

These are snap on plastics which are more like rounded bubble
shaped things than a true cone. They fit on the back of a
trailer.
http://66.102.7.104/search?q=cache:kXPnMiBI4EgJ:www.solusinc.com/pdf/2003-01-3377.pdf+drag+reduction+trailer+&hl=en
Try this link too

http://www.airtab.com/how.htm

[phantom power]

10. According to that report...

they work well, and don't have any adverse effects on driving or utility.

I wonder why I've never actually seen one being used.

[lapfog_1]

11. I have a truck driving friend

and I'll ask... but my first guess is that the trailers are,
generally, the responsibility of the shippers, while the tractors
are owned by the independent trucker. The fuel is expended by
(and paid for) by the truckers, so there really isn't much incentive
for the shipper to attach one to the trailer. The trucker has
the incentive, but they generally want to 1) back the tractor
under the trailer, 2) attach a umbilical of electric and air hoses,
and c) get on the road. Carrying a tail drag reduction device
somewhere on the tractor is going to be difficult. Jumping out
and removing same before backing the trailer into a dock is a major
pain. Not to mention job of attaching and detaching the plastic
cone (could easily be a two person job, but truck driving is
generally a solo occupation).

But I'll ask him.

Inflatable might be a win here, but inflating to a pressure that
maintains shape while traveling at 70, and maintaining that pressure
without leaks into the trailer, all sound like challenging engineering
problems.

[phantom power]

12. Easy to believe. A classic case, really.

I once was part-owner of a software business with a buddy. We had developed a really effective technology for identifying near-duplicate addresses in address lists, and cleaning them out. We figured that this ought to be a fool-proof business. Wouldn't anybody want to keep their address list clean, and spend less on mailing costs? (and reduce customer irritation).

But we discovered that address lists are maintained by separate companies. A typical business just buys the list from one of these specialized list-vendors. But the list vendors are paid by the number of addresses on their list. So there's exactly no motivation for them to buy our clever address-cleaning technology. The customers would probably like it, but they don't really have that much leverage with the vendors.

There should be a term for that kind of progress-inhibiting disconnect, where authority and motivation are disconnected in just exactly the right way to prevent any globally beneficial innovation.

[lapfog_1]

13. I believe the correct military term is SNAFU - n/t