[DeTomaso] Rear Window

[bill gaino]

This gonna be great information!  I have pondered the idea myself.
  Bill 1362


https://www.facebook.com/pages/slickpaintcom/129049637149634?ref=ts&fref=ts  
If you want it slick.  www.slickpaint.com  like us on facebook


-----Original Message-----
>From: Stephen <steve at snclocks.com>
>Sent: Mar 18, 2016 11:35 AM
>To: detomaso at poca.com
>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