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

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

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!

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!

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!:thumbup:

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.:cool:

Sure it could be better, but ease of construction on this is a big thumbs up. :thumbup: 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. :turtle:

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!:thumbup:

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!)

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Also, some screen grabs of the tuft testing:

http://ecomodder.com/forum/attachmen...1&d=1261692596

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.

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

Not organized, but I tried to add some captions.

Snow Visualization
 

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

smoke
 

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!

Thanks Phil.
 

Thanks for the compliment. You were blazing new trails in light truck aerodynamics back in the day at Texas Tech, long before I had a clue. Back then all I was worried about is where the next party was.

Thanks for all your years of hard work in vehicle aerodynamics and then the sharing of the massive data base you have put on line for everyone to have as a great reference here on ecomodder.

Bondo

annoying
 

I cut away for the third brake light,a rear window,and incorporated a flush side window for safety when lane changing and backing out of parallel parking spaces.
The chopped away areas did not remarkably effect mpg.
The claims for attached-vortices appear to have great merit.

I would think that a lot of the turbulence seen down the side is caused by the driver's side mirror.

mirror
 

They're much better than in past generations of vehicles.By streamlining the mirror housing and moving them out away from the side has done a lot to reduce interference drag.
We're hoping that the automakers can successfully petition the DOT for the ability to replace the mirror altogether,replacing with synthetic vision from cameras and displays.
We wait.

Right, but I'm talking about the Ford Ranger in the video. Definitely far from streamlined. I don't know of any pickups with streamlined mirrors since most are oversized to improve visibility, especially when towing loads.

Yep, the 1993 Ranger's mirrors are flat-faced. Some lead in and extended trailing edge could help, but I would prefer to stick a few PS3 cams and a netbook in there.

mirrors
 

drees,I went back and re-watched the video.While the Ranger's mirrors don't "look" streamlined,they actually are,given their frontal area.
If you could get a look at Hucho's book you would find two separate reports addressing the streamlining of bluff bodies,Figure 4.99 and Fig.11.26.
Hucho uses the expression "saturation",where,once a certain degree of rounding of a leading edge is accomplished,the drag minimum is achieved,and no additional streamlining will affect a lower drag.
They're not "swoopy" but aerodynamically,they are very correct.

Tuft Test on Aerolid.
 

In May of 2007, a friend of mine and I made a video of the first Aerolid with tufts of yarn on it. Here is a snapshot of the yarn tufts showing attached air on the sufraces of the Aerolid. I somehow lost the video but at least had kept this snapshot.

The air is attached on the top and sides. At the rear corners it starts to separate. What is really wild is how the air splits on the rear edge of the lid, dead center, and the yarn on the left points left and the yarn on the right points right. I always wondered why this happened.

At the wind tunnel at Allen Park the aero guys spent alot of time with the smoke at the back lip of the Aerolid. They told me the air was separating cleanly off of the roof and that two large counter-rotating vortices, with the one on the left side spinning counter-clockwise and the one on the right side spinning clockwise, created as the air blends off of the sides of the bed into the low pressure air at the rear of the truck, was causing the yarn (or smoke) to go right or left along the rear lip from dead center.

Flow visualization with yarn is easy and fun and can tell us alot about what air does over a surface as most of you know.

Bondo

yarn
 

Looks good to me! Kamm couldn't do better.

You can improve visibility with plexiglass aerocap (I had seen a newer f150 with one and immediately thought that the driver was surfing the Ecomodder)