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Author
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Topic: Pop Quiz & Valvoline?
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Dave Bird
Jedi Master Film Handler
Posts: 777
From: Perth, Ontario, Canada
Registered: Jun 2000
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posted 09-03-2000 08:05 AM
Pop Quiz to myself. My flat lenses are 88.9mm focal length. With 100 foot throw, that's 12'9" x 23'7" image. For scope, 4.75inch (which I figured at 120.65mm) focal length, 100 foot throw, 14'8" x 34'6" image.
Just checking to see if I figured right, if anyone can answer, thanks.Next, in place of Simplex 10-weight projector oil (and I'm sorry, I know I asked before but can't find it), how about Valvoline SAE10 Non-Detergent (in blue bottles, and ONLY until I can source some real Simplex oil from a reputable dealer who doesn't want to wreck my machines by telling me 40-weight "will do")? ------------------
Dave Bird
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John Walsh
Film God
Posts: 2490
From: Connecticut, USA, Earth, Milky Way
Registered: Oct 1999
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posted 09-03-2000 09:33 AM
Dave: Your numbers are right. When I round off to the next lower inch, I get;100 ft throw, 3.5in fl flat, 4.75in fl scope flat height = 12ft 8in
flat width = 23ft 6in scope height = 14ft 8in
scope height = 34ft 8in Do you have adjustable top masking? If not, the formula has to be worked backwards to find a lens to fit the avaiable height. I usually favor flat, (first) so as an example: flat is: 100ft throw, 3.5in fl gives:
flat height = 12ft 8in
flat width = 23ft 6in If top masking is fixed at 12ft 8in, that's what the height for scope will be also. So: scope is: 100ft throw, 12ft 8in high
(.700 * 100) / 12ft 8in = 5.5in fl lens scope would have to be a 5.5in fl lens if the top masking cann not be changed.
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Dave Bird
Jedi Master Film Handler
Posts: 777
From: Perth, Ontario, Canada
Registered: Jun 2000
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posted 09-03-2000 01:23 PM
No adjustable masking John, just adjustable lawn-mowing! I'll need to cut down some hay to build this screen, or right in the middle of the backyard, if wife let's me! These lenses were from a drive-in, and don't seem quite matched for the same size screen, but there must have been good reason. A 200 foot throw would not impede on my backyard, but I don't need a 70 foot screen (yet)!I put some soundhead oil in my XL's a while back by mistake, haven't really been running them, so I want to change it soon. I've got two big jugs of some kind of oil (form salvage day at the drive-in), but can't recall what it was for. Gordon, is your dealer John K. back from holidays or business trip? I've been unable to reach him, though I've been quite busy myself. I want to convert the oil intakes for upward operation. Thanks for all the replies. ------------------
Dave Bird
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