[DeTomaso] Rear Window
Ken Green
kenn_green at yahoo.com
Fri Mar 18 15:39:05 EDT 2016
I talked to a guy a while back who ran regularly at Bonneville. He claimed you can tell a lot by the dust thrown up behind a car, and a lot of dust was in indication of poor air flow around the car.
He said he had seen Panteras at Bonneville, and there was a lot of dust trailing them.
Ken
From: Jack DeRyke via DeTomaso <detomaso at poca.com>
To: kenn_green at yahoo.com; steve at snclocks.com; detomaso at poca.com
Sent: Friday, March 18, 2016 11:59 AM
Subject: Re: [DeTomaso] Rear Window
Besides long-time POCA member "Dr Andy" Wortmann who runs a
professional airflow research laboratory in So-CA, there's racer Dave
Kanahele (also in So-CA) who did some aero stuff to one of his Panteras
in around the same time frame. Both men's efforts made the Pantera rear
silhouette look like a Mangusta. Ron Wade in WA made a few double pane
rear windows hoping for a cabin temp reduction and maybe a sound
reduction. I have his prototype installed in our Pantera, and my
rudimentary testing showed NO temp reduction and only a 1 dB sound
attenuation. Finally, some of the Swedish Pantera owners did tuft-tests
on the road back in the '90s that showed a slight positive pressure in
the engine compartment, leading to the conclusion that replacing the
rear quarter windows with side air scoops tend to bleed air OUTWARD
rather than pull outside air in- at least at legal road speeds and with
small scoops. Boundary layer effects happen here.
Nevertheless, Steven is actually doing something about his guesses and
that's gratifying. Aero is an area in which the medium in question is
invisible, effects change with velocity and intuition is more
frequently wrong than right. That's why good racecar aero guys make as
much as the cars' designers.
J DeRyke (also no aero-expert)
-----Original Message-----
From: Ken Green via DeTomaso <detomaso at poca.com>
To: Stephen <steve at snclocks.com>; detomaso <detomaso at poca.com>
Sent: Fri, Mar 18, 2016 9:25 am
Subject: Re: [DeTomaso] Rear Window
This sounds a lot like what Andrzej Wortman did about 13 years ago. I
think some of his papers were provided to POCA. Mark McWhinney seemed
to be the main point of contact.
Ken
__________________________________________________________________
From: Stephen <[1]steve at snclocks.com>
To: [2]detomaso at poca.com
Sent: Friday, March 18, 2016 8:35 AM
Subject: [DeTomaso] Rear Window
I've been pondering for quite a while now the idea of putting a piece
of glass in the "window" in the deck lid behind the engine in 5332.
This would keep the engine from getting wet every time it rains and
would also keep from sucking grit and water off the road when the car
is running down the road.
Both seem like decent goals. Oh, and it would also make it more
difficult for someone to just reach in and remove 5332's dog-bone air
cleaner. OK - no one has taken it so far. But, hey, it would be all
too easy to remove.
Looking at the opening - it sure looks like the original intent was
to
put in a window.
I have sent an e-mail to Tom Tjaarda (attached) asking his thoughts.
Hopefully he will respond.
In the interim, I put together a set of sensors so I could see what I
could learn about conditions in the engine compartment just inches in
front of the opening, to the right side of the dog-bone. The
attached
photo shows the instrument cluster shot from inside the car.
I'm measuring air velocity through the rear window (vane anemometer)
Vacuum just in front of the window
Rotation of the a/c condenser fan (volt meter connected across the
motor, which acts as a generator when the fan turns)
Two of the above are fairly straight forward. The vacuum - not so
much.
When one talks about a vacuum, one is usually talking about a vacuum,
relative to ambient atmospheric pressure. So, if a vacuum gauge is
hooked up to your intake manifold, it reads the difference in
pressure
between the atmosphere where the gauge is sitting, and the inside of
your manifold, where the hose from the gauge is connected.
So, what does one compare to in a moving car? The interior of the
car? That is what one would get if one puts a vacuum gauge in the
cab
and routes the hose to the area in question. But, what does the
pressure (or vacuum) inside the car do with the car moving down the
road. Open the windows, your ears pop, and the pressure changes.
Most
of us don't have an external air inlet (at least an intentional one)
to
the cab except for the windows.
My solution is to use a fairly sensitive pressure gauge (a
sphygmomanometer - gauge used to read blood pressure. It reads in
inches of mercury. FYI, there are roughly 50 inches of mercury per
psi). I have connected the gauge with small-diameter plastic tubing
to
a 200 ml stainless sample bomb. I wrapped the bomb in towels and
placed in a cooler to minimize temperature changes. See, the
pressure
in the bomb will change by roughly .03 psi (1.5 mm Hg) for each 1
degree F change in temperature.
I then pressured up the bomb and let it sit overnight to stabilize.
It
ended up at 280 mm. This is my "zero" at the then current barometric
pressure.
One has to view the pressure gauge as a delta-pressure device. It
shows the difference in pressure between the bomb (high pressure) and
the atmosphere around the gauge. So, if the reading on the gauge
goes
up, the differential is increasing, which means the atmospheric
pressure is going down. As in a wee bit of a vacuum around the
gauge.
Flip side, if the reading on the gauge goes down, well, there is less
differential between the 280 mm Hg in the bomb and the atmosphere
around the gauge, so the pressure is going up.
OK - that is complex.
While a gauge that can be read down to around 1 mm hg (0.02 psi) is
pretty sensitive, I suspect we are talking pretty minimal vacuum
levels. Preliminary testing suggested a reading of 272 mm Hg at 80
mph. The pressure around the gauge went up!
Huh. A lot to learn here.
I also noted that the volt meter did not show any rotation of the fan
on the a/c condenser. Need to make sure the wiring is ok. But,
note,
the meter reads in mV, and, in my earlier testing, it showed voltage
if
the fan turned at all.
The rubber for the new window shows up today, the window next
Wednesday.
My plan is to get a decent video and stills of the test instruments
at
several speeds. Then, when the new window is installed, rerun the
test. I suspect the anemometer will still be valuable, since I
suspect
there will be a lot of turbulence in the air in the engine
compartment
even with the window in place.
Needless to say, having the window in place will complicate putting
the
deck-lid back in place.
Stephen Nelson
Good morning Tom. Whilst I am pretty sure you have no clue who I am,
being a member of POCA, I am aware of your contribution to the
Pantera. And I thank you for what you designed.
Being fairly new to these cars (3 years) I am still learning a lot.
One thing I have noted is the ability of my car to pick stuff up off
the road when I am driving at speed. I have found 1/4 inch gravel
behind the inlet manifold and was amazed to see high water marks on
the
side of the rocker covers after a couple of hours driving in the rain
at 70 mph. Really quite neat actually, little wave pattern down the
sides of the rocker covers. Should have shot a picture.
None the less, I have queried the POCA forum about the absence of
glass
in the opening behind the top of the engine. Folks indicated no one
had ever tried installing glass, and some voiced concerns about the
cars overheating if there was not lots of air flow past the engine.
So, am writing to see if I can get your thoughts on the lack of a
window in the deck lid and would appreciate any wisdom you can
impart.
Whilst I have done a number of upgrades to 5332, including making the
engine a wee bit stronger, installing the best radiator and fans that
I
could identify, and getting the a/c so it keeps the car comfortable,
I
haven't really made any changes in the aerodynamics - like wings or
spoilers or front air dams. I suspect she would be a good test mule
for such a window and plan to start my investigation by figuring out
pressure (vacuum) levels above the engine at various speeds and also
the direction of rotation and relative rpm of the a/c condenser fan
(volt meter across the motor). My thought is to then do the same
with
a window in place.
Any and all comments would be appreciated.
Stephen Nelson
[1]SNClocks.com
Click here to join one of our mailing lists [2]Contact Lists
Click here for our new [3]Hammered Dulcimers galleries
Click here for [4]my new blog on finding happiness in retirement
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-------------- next part --------------
I talked to a guy a while back who ran regularly at Bonneville. He
claimed you can tell a lot by the dust thrown up behind a car, and a
lot of dust was in indication of poor air flow around the car.
He said he had seen Panteras at Bonneville, and there was a lot of dust
trailing them.
Ken
__________________________________________________________________
From: Jack DeRyke via DeTomaso <detomaso at poca.com>
To: kenn_green at yahoo.com; steve at snclocks.com; detomaso at poca.com
Sent: Friday, March 18, 2016 11:59 AM
Subject: Re: [DeTomaso] Rear Window
Besides long-time POCA member "Dr Andy" Wortmann who runs a
professional airflow research laboratory in So-CA, there's racer Dave
Kanahele (also in So-CA) who did some aero stuff to one of his
Panteras
in around the same time frame. Both men's efforts made the Pantera
rear
silhouette look like a Mangusta. Ron Wade in WA made a few double
pane
rear windows hoping for a cabin temp reduction and maybe a sound
reduction. I have his prototype installed in our Pantera, and my
rudimentary testing showed NO temp reduction and only a 1 dB sound
attenuation. Finally, some of the Swedish Pantera owners did
tuft-tests
on the road back in the '90s that showed a slight positive pressure
in
the engine compartment, leading to the conclusion that replacing the
rear quarter windows with side air scoops tend to bleed air OUTWARD
rather than pull outside air in- at least at legal road speeds and
with
small scoops. Boundary layer effects happen here.
Nevertheless, Steven is actually doing something about his guesses
and
that's gratifying. Aero is an area in which the medium in question is
invisible, effects change with velocity and intuition is more
frequently wrong than right. That's why good racecar aero guys make
as
much as the cars' designers.
J DeRyke (also no aero-expert)
-----Original Message-----
From: Ken Green via DeTomaso <[1]detomaso at poca.com>
To: Stephen <[2]steve at snclocks.com>; detomaso <[3]detomaso at poca.com>
Sent: Fri, Mar 18, 2016 9:25 am
Subject: Re: [DeTomaso] Rear Window
This sounds a lot like what Andrzej Wortman did about 13 years ago. I
think some of his papers were provided to POCA. Mark McWhinney seemed
to be the main point of contact.
Ken
__________________________________________________________________
From: Stephen <[1][4]steve at snclocks.com>
To: [2][5]detomaso at poca.com
Sent: Friday, March 18, 2016 8:35 AM
Subject: [DeTomaso] Rear Window
I've been pondering for quite a while now the idea of putting a piece
of glass in the "window" in the deck lid behind the engine in 5332.
This would keep the engine from getting wet every time it rains and
would also keep from sucking grit and water off the road when the car
is running down the road.
Both seem like decent goals. Oh, and it would also make it more
difficult for someone to just reach in and remove 5332's dog-bone air
cleaner. OK - no one has taken it so far. But, hey, it would be all
too easy to remove.
Looking at the opening - it sure looks like the original intent was
to
put in a window.
I have sent an e-mail to Tom Tjaarda (attached) asking his thoughts.
Hopefully he will respond.
In the interim, I put together a set of sensors so I could see what I
could learn about conditions in the engine compartment just inches in
front of the opening, to the right side of the dog-bone. The
attached
photo shows the instrument cluster shot from inside the car.
I'm measuring air velocity through the rear window (vane anemometer)
Vacuum just in front of the window
Rotation of the a/c condenser fan (volt meter connected across the
motor, which acts as a generator when the fan turns)
Two of the above are fairly straight forward. The vacuum - not so
much.
When one talks about a vacuum, one is usually talking about a vacuum,
relative to ambient atmospheric pressure. So, if a vacuum gauge is
hooked up to your intake manifold, it reads the difference in
pressure
between the atmosphere where the gauge is sitting, and the inside of
your manifold, where the hose from the gauge is connected.
So, what does one compare to in a moving car? The interior of the
car? That is what one would get if one puts a vacuum gauge in the
cab
and routes the hose to the area in question. But, what does the
pressure (or vacuum) inside the car do with the car moving down the
road. Open the windows, your ears pop, and the pressure changes.
Most
of us don't have an external air inlet (at least an intentional one)
to
the cab except for the windows.
My solution is to use a fairly sensitive pressure gauge (a
sphygmomanometer - gauge used to read blood pressure. It reads in
inches of mercury. FYI, there are roughly 50 inches of mercury per
psi). I have connected the gauge with small-diameter plastic tubing
to
a 200 ml stainless sample bomb. I wrapped the bomb in towels and
placed in a cooler to minimize temperature changes. See, the
pressure
in the bomb will change by roughly .03 psi (1.5 mm Hg) for each 1
degree F change in temperature.
I then pressured up the bomb and let it sit overnight to stabilize.
It
ended up at 280 mm. This is my "zero" at the then current barometric
pressure.
One has to view the pressure gauge as a delta-pressure device. It
shows the difference in pressure between the bomb (high pressure) and
the atmosphere around the gauge. So, if the reading on the gauge
goes
up, the differential is increasing, which means the atmospheric
pressure is going down. As in a wee bit of a vacuum around the
gauge.
Flip side, if the reading on the gauge goes down, well, there is less
differential between the 280 mm Hg in the bomb and the atmosphere
around the gauge, so the pressure is going up.
OK - that is complex.
While a gauge that can be read down to around 1 mm hg (0.02 psi) is
pretty sensitive, I suspect we are talking pretty minimal vacuum
levels. Preliminary testing suggested a reading of 272 mm Hg at 80
mph. The pressure around the gauge went up!
Huh. A lot to learn here.
I also noted that the volt meter did not show any rotation of the fan
on the a/c condenser. Need to make sure the wiring is ok. But,
note,
the meter reads in mV, and, in my earlier testing, it showed voltage
if
the fan turned at all.
The rubber for the new window shows up today, the window next
Wednesday.
My plan is to get a decent video and stills of the test instruments
at
several speeds. Then, when the new window is installed, rerun the
test. I suspect the anemometer will still be valuable, since I
suspect
there will be a lot of turbulence in the air in the engine
compartment
even with the window in place.
Needless to say, having the window in place will complicate putting
the
deck-lid back in place.
Stephen Nelson
Good morning Tom. Whilst I am pretty sure you have no clue who I am,
being a member of POCA, I am aware of your contribution to the
Pantera. And I thank you for what you designed.
Being fairly new to these cars (3 years) I am still learning a lot.
One thing I have noted is the ability of my car to pick stuff up off
the road when I am driving at speed. I have found 1/4 inch gravel
behind the inlet manifold and was amazed to see high water marks on
the
side of the rocker covers after a couple of hours driving in the rain
at 70 mph. Really quite neat actually, little wave pattern down the
sides of the rocker covers. Should have shot a picture.
None the less, I have queried the POCA forum about the absence of
glass
in the opening behind the top of the engine. Folks indicated no one
had ever tried installing glass, and some voiced concerns about the
cars overheating if there was not lots of air flow past the engine.
So, am writing to see if I can get your thoughts on the lack of a
window in the deck lid and would appreciate any wisdom you can
impart.
Whilst I have done a number of upgrades to 5332, including making the
engine a wee bit stronger, installing the best radiator and fans that
I
could identify, and getting the a/c so it keeps the car comfortable,
I
haven't really made any changes in the aerodynamics - like wings or
spoilers or front air dams. I suspect she would be a good test mule
for such a window and plan to start my investigation by figuring out
pressure (vacuum) levels above the engine at various speeds and also
the direction of rotation and relative rpm of the a/c condenser fan
(volt meter across the motor). My thought is to then do the same
with
a window in place.
Any and all comments would be appreciated.
Stephen Nelson
[1]SNClocks.com
Click here to join one of our mailing lists [2]Contact Lists
Click here for our new [3]Hammered Dulcimers galleries
Click here for [4]my new blog on finding happiness in retirement
References
1. [1][3][6]http://www.snclocks.com/
2.
[2][4][7]http://fs19.formsite.com/kagforms/form675003155/index.html
3.
[3][5][8]http://www.snclocks.com/TheRestofourWorld/Hammered-Dulcimers/A
bou
t-S
teves-Dulcimers/19824807_4sHGgj#1558377542_LKmkrT7
4. [4][6][9]http://www.perfectoldman.com/
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