Central Pressure Differential Reduction Tube...

[Frank Lee]

I'm not buying the duct idea but anyone can feel free to test it out, or find existing research that may have tested it.

[gasman]

I haven't found an example where it has been tried with the purpose of reducing drag, so the results don't really apply (they didn't measure what I needed measured... at least that I could find publicly).

If I'm right, though, it might be a moot point. It would be a pretty involved install (cutting a big hole in the firewall and other obstructions, making it water-tight, keeping the ducting out of the way, etc.).

man I wish I had access to a wind tunnel...

I just might have to build one of these (low-speed wind tunnel, courtesy of NASA)... I checked it out and I have everything except the plexiglass and fan... and I can just adapt a computer power supply and computer fans to go in place of that... hmmm...

[user removed]

NASA is tearing the wind tunnels down at Langley AFB. Been there since it was NACA.

regards
Mech

[aerohead]

Originally Posted by gasman

I haven't found an example where it has been tried with the purpose of reducing drag, so the results don't really apply (they didn't measure what I needed measured... at least that I could find publicly).

If I'm right, though, it might be a moot point. It would be a pretty involved install (cutting a big hole in the firewall and other obstructions, making it water-tight, keeping the ducting out of the way, etc.).

man I wish I had access to a wind tunnel...

I just might have to build one of these (low-speed wind tunnel, courtesy of NASA)... I checked it out and I have everything except the plexiglass and fan... and I can just adapt a computer power supply and computer fans to go in place of that... hmmm...

Since you've done HVAC work,let me throw some at you in HVAC terms:
* At 60 mph,a vehicle of 22 sq-ft frontal area( typical mid-size car ) is displacing 116,160 cubic feet per mile,or,116,160 cfm.
* From your ASHRAE Manual it should indicate that to avoid unacceptable duct friction losses for the 'air handler' velocities should be kept below 1,200 fpm.
* If you were to shunt all the vehicles air through your duct at 1,200 fpm it would require a throat size of 96.8 sq-ft,or 9.838 on a side for a square duct or 11.1 ft dia. round duct.This is obviously larger than the vehicle itself.
* If you make the duct smaller to accommodate seats,passengers,engine,powertrain,etc.,the duct losses would be larger.

[mwebb]

the military had a similar idea
Tubular bullets
they did extensive testing many years separated the testing events , both sets of tests showed that the tubular bullets did not reduce drag

from the spitzer boat tail shape

which is the shape of bullet with the least amount of drag as proven in the real world more times than can be counted .
which contradicts all of the thoughts on aerodynamics regarding the front of a car in this forum .

however a bullet spinning at 100k rpm traveling at faster than the speed of sound
is not a car .
none the less
there are no round nose boat tail bullets
and the round nose flat base bullets have terrible ballistic coefficients compared to
spitzer (pointed) boat tail bullets

just a thought

[pounsfos]

im curious about this test but would love to see a-b-a testing to see if it is plausable.


will keep an eye on this

[1995gsx20g]

it may seem a little more outlandish then gasman but the idea that came to my mind was to create a hole in the firewall lets say of 6 inch diameter and run no duct while in cab. with an 8in diameter hole at the tail of the car attached to a 500cfm inline booster fan. yes the car would be a wind tunnel and it has flaws with water but could this push the duct drag to the side and actually make some gains? or does this make the entire inside of the cab part of the frontal drag?

[kach22i]

Nothing in this article about the holes "in-flight", but an interesting design.

"Holey" bullets claimed to go faster

At the same time, the gases shooting out of the vents are also said to create a rocket-like effect, increasing the bullet's velocity. All of you physicists are welcome to weigh in on this one, but it's hard to say if gases exiting the sides of a bullet would really cause it to travel any faster than gases that were limited to pushing on it from behind.