[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
  References
  1. [1][3]http://www.snclocks.com/
  2. [2][4]http://fs19.formsite.com/kagforms/form675003155/index.html
  3.
  [3][5]http://www.snclocks.com/TheRestofourWorld/Hammered-Dulcimers/Abou
  t-S
  teves-Dulcimers/19824807_4sHGgj#1558377542_LKmkrT7
  4. [4][6]http://www.perfectoldman.com/
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  3.
  [11]http://www.snclocks.com/TheRestofourWorld/Hammered-Dulcimers/About-
  Steves-Dulcimers/19824807_4sHGgj#1558377542_LKmkrT7
  4. [12]http://www.perfectoldman.com/
  5. [13]mailto:DeTomaso at poca.com
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References

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  3. http://www.snclocks.com/
  4. http://fs19.formsite.com/kagforms/form675003155/index.html
  5. http://www.snclocks.com/TheRestofourWorld/Hammered-Dulcimers/About-S
  6. http://www.perfectoldman.com/
  7. mailto:DeTomaso at poca.com
  8. http://poca.com/mailman/listinfo/detomaso_poca.com
  9. http://www.snclocks.com/
  10. http://fs19.formsite.com/kagforms/form675003155/index.html
  11. http://www.snclocks.com/TheRestofourWorld/Hammered-Dulcimers/About-Steves-Dulcimers/19824807_4sHGgj#1558377542_LKmkrT7
  12. http://www.perfectoldman.com/
  13. mailto:DeTomaso at poca.com?
  14. http://poca.com/mailman/listinfo/detomaso_poca.com
  15. mailto:DeTomaso at poca.com
  16. http://poca.com/mailman/listinfo/detomaso_poca.com

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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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     use the links above.
     References
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     3.

   [11][14]http://www.snclocks.com/TheRestofourWorld/Hammered-Dulcimers/Ab
   out-
     Steves-Dulcimers/19824807_4sHGgj#1558377542_LKmkrT7
     4. [12][15]http://www.perfectoldman.com/
     5. [13]mailto:[16]DeTomaso at poca.com
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   References
     1. mailto:[20]steve at snclocks.com
     2. mailto:[21]detomaso at poca.com
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     4. [23]http://fs19.formsite.com/kagforms/form675003155/index.html
     5.
   [24]http://www.snclocks.com/TheRestofourWorld/Hammered-Dulcimers/About-
   S
     6. [25]http://www.perfectoldman.com/
     7. mailto:[26]DeTomaso at poca.com
     8. [27]http://poca.com/mailman/listinfo/detomaso_poca.com
     9. [28]http://www.snclocks.com/
     10. [29]http://fs19.formsite.com/kagforms/form675003155/index.html
     11.
   [30]http://www.snclocks.com/TheRestofourWorld/Hammered-Dulcimers/About-
   Steves-Dulcimers/19824807_4sHGgj#1558377542_LKmkrT7
     12. [31]http://www.perfectoldman.com/
     13. mailto:[32]DeTomaso at poca.com?
     14. [33]http://poca.com/mailman/listinfo/detomaso_poca.com
     15. mailto:[34]DeTomaso at poca.com
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References

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   3. mailto:detomaso at poca.com
   4. mailto:steve at snclocks.com
   5. mailto:detomaso at poca.com
   6. http://www.snclocks.com/
   7. http://fs19.formsite.com/kagforms/form675003155/index.html
   8. http://www.snclocks.com/TheRestofourWorld/Hammered-Dulcimers/Abou
   9. http://www.perfectoldman.com/
  10. mailto:DeTomaso at poca.com
  11. http://poca.com/mailman/listinfo/detomaso_poca.com
  12. http://www.snclocks.com/
  13. http://fs19.formsite.com/kagforms/form675003155/index.html
  14. http://www.snclocks.com/TheRestofourWorld/Hammered-Dulcimers/About-
  15. http://www.perfectoldman.com/
  16. mailto:DeTomaso at poca.com
  17. http://poca.com/mailman/listinfo/detomaso_poca.com
  18. mailto:DeTomaso at poca.com
  19. http://poca.com/mailman/listinfo/detomaso_poca.com
  20. mailto:steve at snclocks.com
  21. mailto:detomaso at poca.com
  22. http://www.snclocks.com/
  23. http://fs19.formsite.com/kagforms/form675003155/index.html
  24. http://www.snclocks.com/TheRestofourWorld/Hammered-Dulcimers/About-S
  25. http://www.perfectoldman.com/
  26. mailto:DeTomaso at poca.com
  27. http://poca.com/mailman/listinfo/detomaso_poca.com
  28. http://www.snclocks.com/
  29. http://fs19.formsite.com/kagforms/form675003155/index.html
  30. http://www.snclocks.com/TheRestofourWorld/Hammered-Dulcimers/About-Steves-Dulcimers/19824807_4sHGgj#1558377542_LKmkrT7
  31. http://www.perfectoldman.com/
  32. mailto:DeTomaso at poca.com
  33. http://poca.com/mailman/listinfo/detomaso_poca.com
  34. mailto:DeTomaso at poca.com
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