Video: on-road tuft testing Ford Ranger aeroshell / aerotopper / aerocap

[MetroMPG]

Found this by accident today. Is this an EcoModder's work? Did I miss a thread?

Note the mini wheel skirts on the back wheels too.

http://www.youtube.com/watch?v=QMWITzkVNtU

Sloped truck topper is intended to reduce the aerodynamic drag on a pickup truck as compared to an uncovered bed. If achieved, the results are likely to be improved fuel economy during highway travel, lower wind noise, and higher top speed. Angle of declination is ~8 degrees, and flow appears to be attached, yet turbulent. Construction is corrugated plastic on a 2x2 treated lumber frame. Secured to bed by 4 nylon tie-downs with 330 lb working load, with 1000lb break rating.

Fuel economy:
EPA Rating: 22mpg highway
Current Actual: ~25mpg highway
Desired: 30mpg

[RobertSmalls]

I wonder what kind of results he'd see from sealing up the gap between cab and cap, plus more aggressive wheelskirts. You could better aero from a gradually increasing curvature, and the cap would probably end around the top of the tailgate.

But even if there are more aerodynamic designs out there, you have to admire the easy to do coroplast on lumber construction.

Plus he's got beaded seat covers!

[MetroMPG]

You can actually see signs of a separation bubble on the side of the cap, right behind the cab. So you're right: gap fillers would probably help.

I think ease of construction beat out full optimization. Can't fault that approach. Better than doing nothing at all.

Aeroshell, beaded seat covers, mini fender skirts... this guy must be a member!

[Jethro]

It's tempting to try something like this on the Ram.

It's gotta be real annoying not being able to see out the back of the truck though. How bad would it be to remove the tailgate? With as 'high' as my truck is, it'd give me a pretty good view that way!

Currently if I am gently cruising at about 60 I can get 17 out of her out on the highway.

Of course, I bought my 200SX, so the truck is now a foul weather / off road toy.

[thatguitarguy]

Sure it could be better, but ease of construction on this is a big thumbs up. That side angle cut doesn't even look like a straight edge was used. It probably took him just as long to place those tufts as it did to build the thing in the first place.

Visibility is what you are used to. If you've ever driven a delivery truck, or a bus, you can't see out the back or the side. You have to use mirrors. Mirror deletes may be aerodynamic, but for me, the safety trade off isn't worth it without a video replacement.

My Ranger was older, but with the 5 speed I could get 27mpg just by slowing down. I would think 30mpg in this thing would be doable if he did the same.

[Jethro]

Visibility is a huge thing for me. I sold the camper shell that came on my truck because it destroyed visibility.

Intentionally hindering your visibility is silly IMO. Course, I worked for an insurance company, and after seeing THAT MANY wrecks, yea, you do what you can to avoid em!

[MetroMPG]

I asked the cap owner if he saw any improvement. (He seems to know who MetroMPG is, even though I asked using the EcoModder account - mysterious!)

Originally Posted by EcoModderDOTcom ... (21 hours ago)

Were you able to measure any fuel economy change after making the aero cap?

Originally Posted by NickSuch21 ... (9 minutes ago)

Hey MetroMPG! I need to build an MPGuino so I can get some better data. I saw about a 2mpg improvement, but that was within the noise of my per-tank fuel measurement method. This was mostly for testing the attachment method at speed and the robustness of the construction. Definitely a lot of room for improvement.

---

Also, some screen grabs of the tuft testing:



Top image shows what you want to see: attached flow (tufts streaming aft) on the top & sides, right to the end of the cap.

Middle image shows evidence of the separation bubble behind the cab. Not a huge deal, but interesting to catch. The lower tuft reversed direction / swirled around a lot more often than the next one up.

Lower image is interesting because it captures what to my eye looked like a tendency of the uppermost tufts on the side of the cap to angle slightly upward on average. I think this indicates flow moving upward toward the lower pressure on the top surface. And it underscores why we should aim for curved transitions where possible instead of sharp corners, so flow moving from one surface to another doesn't have the chance to "trip" or separate going past the corner. (The exception being trailing edges, where it's OK to chop off and leave a sharp angle.)

Just nitpicking. Perfect is the enemy of good. I think it's fair to say the cap probably works as intended.

[suchy21]

Originally Posted by MetroMPG

Aeroshell, beaded seat covers, mini fender skirts... this guy must be a member!

Here's some mod candy for Christmas: Picasa Web Albums - Nick - Aerodynamic T...

Not organized, but I tried to add some captions.

[bondo]

Back in February of 2005 I photographed the way the snow had blown off the first aerocap I built on the way to work. It looks as if the air was turbulent in the central part of the roof and then became laminar as it moved rearward, blowing the snow away from the surface in two distinct wedge shaped areas.

The ridge of snow which built up along the edge of the cap is interesting. This first cap was not that effective because the roof was too flat and the angle of the roof was too severe causing separation.

I wish I could find the video of the flow visualization I did on the present design of the aerocap back in May of 2007 using yarn tufts. It showed good attached air all around the lid except for the rear corners. The two wind tunnel tests we have done showed the same when the smoke was applied.

Bondo

[aerohead]

Originally Posted by bondo

Back in February of 2005 I photographed the way the snow had blown off the first aerocap I built on the way to work. It looks as if the air was turbulent in the central part of the roof and then became laminar as it moved rearward, blowing the snow away from the surface in two distinct wedge shaped areas.

The ridge of snow which built up along the edge of the cap is interesting. This first cap was not that effective because the roof was too flat and the angle of the roof was too severe causing separation.

I wish I could find the video of the flow visualization I did on the present design of the aerocap back in May of 2007 using yarn tufts. It showed good attached air all around the lid except for the rear corners. The two wind tunnel tests we have done showed the same when the smoke was applied.

Bondo

Brett,from what I remember of the smoke flow images for your cap,the near-field flow was great.Even the Kamm cars exhibit some "drunkenness" with the flow,where top and sides meet.
You have no apologies to make for your cap designs,I consider them to be the BENCHMARK.Delicious!