How to do pics of tuft testing

[JulianEdgar]

One thing I really notice is that very few pics of tuft testing are posted here. As a zero cost way of seeing where there is attached and separated airflow - and also airflow direction - tuft testing is brilliant.

I like to use still image cameras for this (ie as opposed to a video camera), taking a sequence of photos and then picking the best single one that is indicative of the tuft pattern. Then I usually crop it a lot.

Photographing from the side of the road when the car passes you at ~60 km/h (35 mph) is usually fine. (Probably, you can do it in the street in which you live!)

To do this type of photography, I think that you need a camera that has:

• a fast shutter response, ie it takes the pic the instant you press the button (most dig cameras these days)
  
• the ability to set the required high shutter speed (most good consumer cameras and all 'prosumer' cameras)
  
• the ability to do a sequence of shots rapidly, one after the other (varies lot between cameras - look for burst mode of, say, 8-10 shots)
  
• a telephoto lens focal length that retains good resolution (again, most good consumer cameras and all 'prosumer' cameras, but be wary of digital zooms)

So, a sequence of pics as the car drives by me:



And then after selecting and cropping:



Final shot:

• Nikon D300
• Focal length 195mm (35mm equivalent)
• F9 aperture at 1/500th of a second shutter speed
• +0.3 stop exposure compensation

(This pic is showing the airflow pattern without Edgarwits front external air curtains)

And here is another, literally taken in the middle of suburbia (the driver was braking for the culdesac at the end of the street - note neighbour's post box!):

[freebeard]

An industry standard for testing is the 100ft circle (usually for G-forces).

With a camera on tripod and operator at the center you could record crosswind conditions efficiently.

[JulianEdgar]

Originally Posted by freebeard

An industry standard for testing is the 100ft circle (usually for G-forces).

With a camera on tripod and operator at the center you could record crosswind conditions efficiently.

I have done extensive amounts of skid pan testing, including at car manufacturer's proving grounds, on test facilities, and on my own circles (chalked on roundabouts for HPVs).

I do not think this is a good guide to crosswinds, as the air yaw angle is constantly changing - and the 'crosswind' component is relatively small.

On my 'home' skid pad:



(My first recumbent trike: it met the skidpan criterion but it was waaay too heavy.)

And my Lexus on the skid pan

[Gasoline Fumes]

I did some tuft testing with my ugly old Honda Civic Wagon. Lousy photos, didn't get any help!

Hood, windshield and roof looked good.





Behind the front wheel:



It looked like air was going under the side skirt:



Side mirror:



Side mirror removed:

I was so surprised by the air moving upwards behind the A pillar that I added more tufts!

[M_a_t_t]

Originally Posted by Gasoline Fumes

Lousy photos, didn't get any help!

I have the same problem. I think I've convinced my Mother to drive my car and then I can try to take pictures from the side of the road or follow in her car and try to take pictures or atleast observe them and take notes.

[JulianEdgar]

Originally Posted by Gasoline Fumes

I did some tuft testing with my ugly old Honda Civic Wagon. Lousy photos, didn't get any help!

Hood, windshield and roof looked good.

Yes, very seldom any problem in these areas on any car of the last 30 years

Behind the front wheel:

Looks excellent with smooth wheel cover

It looked like air was going under the side skirt:

Often the case - airflow is travelling towards the low pressure area under the car.

Side mirror:

Side mirror removed:

Flow on the door window is better with the mirror present! Mirror present: main door glass flow separation only behind mirror support. Mirror not present: main door glass separation more prevalent.

I was so surprised by the air moving upwards behind the A pillar that I added more tufts!

Flow pattern directly behind A pillar is common - I assume it indicates the developing of a trailing vortex off each front pillar. Removal of mirror appears to have increased the area of this flow substantially. It would be interesting to do throttle stop drag testing with and without the mirror.

[M_a_t_t]

How is this?

[JulianEdgar]

Need standard / modified shots.

[M_a_t_t]

I don't have a direct picture of the stock setup. I will get one tomorrow when it is daylight.





Here is a video I shot of it. I was trying to center the shot in the first 2 shots. The 2nd one didn't really work out. If you slow down the last few seconds it shows the modified version pretty well.

https://www.youtube.com/watch?v=RavN...hannel=M_a_t_t

[Gasoline Fumes]

Originally Posted by JulianEdgar

Flow on the door window is better with the mirror present! Mirror present: main door glass flow separation only behind mirror support. Mirror not present: main door glass separation more prevalent.


Flow pattern directly behind A pillar is common - I assume it indicates the developing of a trailing vortex off each front pillar. Removal of mirror appears to have increased the area of this flow substantially. It would be interesting to do throttle stop drag testing with and without the mirror.

I had also tested the right front window. That car never had a mirror there. I can't explain why the two sides were so different! Multiple photos show the same patterns. I taped over the mirror hole on the left side. I wish I had known about throttle stop testing when that car was still roadworthy. Maybe I'll do some testing with my Insight if I ever get it running correctly.