Interesting Aerodynamic Cars (Mike Vetter's ETV, also Avion)

[Bicycle Bob]

Originally Posted by AeroMcAeroFace

I wouldn't fancy driving that delivery vehicle over a windy bridge, you would hope it has a low centre of mass so it doesn't tip over.

That VW has a gurney flap on the diffuser, is that for diffuser function or air flowing over the top of the diffuser? Has anyone seen any evidence for this or heard of it before?

The location of mass does not matter for a just a crosswind, only the total. This shape looks as if it might have less drag in a crosswind, working as a sail. For real benefits, though, the sail has to be able to spill wind if overturning is imminent for any reason. With a bit more activity, it should be able to resist cornering forces directly instead of through downforce.

[AeroMcAeroFace]

Why does the mass location not make any difference? Would the car be as likely to tip in cross winds if the mass was concentrated 100 feet in the air? Maybe resistance to sliding, turning or being a weather vane is related to total mass but I don't understand how the mass being lower wouldn't improve crosswind tipping resistance.

If the mass was infinitely high it would be an inverted pendulum and any breeze would topple it over.

[Bicycle Bob]

Originally Posted by AeroMcAeroFace

Why does the mass location not make any difference? Would the car be as likely to tip in cross winds if the mass was concentrated 100 feet in the air? Maybe resistance to sliding, turning or being a weather vane is related to total mass but I don't understand how the mass being lower wouldn't improve crosswind tipping resistance.

If the mass was infinitely high it would be an inverted pendulum and any breeze would topple it over.

If the mass were very high, it would take the centre of pressure up with it in any realistic visualization. However, the mass itself will always be acting straight down, and as long as the road is level and straight, will have the same effect.

[freebeard]

That VW has a gurney flap on the diffuser, is that for diffuser function or air flowing over the top of the diffuser? Has anyone seen any evidence for this or heard of it before?

At 4:00 — "It extends the effective length, apparently."

The postal truck has a central peak. How does that affect crosswind performance?

[kach22i]

Could of went faster but for the crosswinds.

https://forums.pelicanparts.com/off-...ures-2393.html


Article:
https://www.automobilemag.com/news/s...on-car-record/

[kach22i]

Cool scale model.

AutoCult 1/43 Audi Front UW8/40PS Jayray 04026
https://houseofhobbies.com/products/...s-jayray-04026

[aerohead]

Originally Posted by AeroMcAeroFace

I wouldn't fancy driving that delivery vehicle over a windy bridge, you would hope it has a low centre of mass so it doesn't tip over.

That VW has a gurney flap on the diffuser, is that for diffuser function or air flowing over the top of the diffuser? Has anyone seen any evidence for this or heard of it before?

I'd like the guy to expand on his thesis.
The original 1971 Gurney flap was intended for undisturbed, upper body flow.
Embedded within the wake, as it's shown, perhaps it's isolating the diffuser effect from the wake turbulence enough to marginally amplify the downforce. A direct explanation is always better than a guess. Especially mine.

[freebeard]

A direct explanation is always better than a guess. Especially mine.

I think we're all bozos on this bus.

I see it as a localized feature at the interface between the (more or less stagnant) wake and fast-moving air. In this case the fast moving air is in the diffuser. I wonder why it isn't inverted. It would be easy enough to test both orientations.

[kach22i]

https://myautoworld.com/gm/history/c...tte1-57ss.html

The science of aerodynamics has progressed since the days when GM engineers conducted airflow tests with tufts of yarn taped to Zora Arkus-Duntov's 1957 Corvette SS.

[sgtlethargic]

Eco-Runner X: