Ok, I'm a writer with a liberal arts background, and I do not know how to calculate this.

Here is my question:

What will be the distance from the ceiling to the center of my projector given the following parameters?

1) The lens is 12.5" from the ceiling tilted at around 11-12 degrees downward (see dimensions below to see how I arrived at this).

2) The lens is 7' from the screen.


The box is 30" long and the rear will be lifted (assuming this works out) 6".

I'm hoping the center will be 30-36" from the ceiling.

Thanks

I'm not following you. Got a drawing?

How's this - quick and dirty.

Is this what you're looking for? If the rear is 6 inches higher, the center is 3 inches higher. No math required.

Edit: I'm a guru! I'm a guru! Pretty good for a guy without a completed projector or even a plog. (Coming soon. Try not to die of boredom.)

Thanks

But, I was looking for how far from the ceiling the center point of the projected image will be with this set up.

If it's at 30-36 inches from the ceiling I'm good. The bottom of the screen will not be too high for comfortable viewing. If it is less than 30 inches, I need to angle it more. If I need to angle it more, I will need to build a bigger exterior box to accomodate the increased angle.

Therefore, finding this out now, helps on several fronts.

Thanks again, though

For the throw as specified at 7' (84")

The rise/run of 6" rise over 30" run will determine the angle. (Easier than messing around with messy degrees or even radians for this problem.)

So 30 goes into 84 2.8 times.

Therefore the change in height over the same run is 6" X 2.8 = 16.8" Then you add the 12.5" that the center of hte lens is already down from the ceiling and you get a total of 29.3"

Great! Thanks!

Ok, I didn't really think that's what you wanted. The one piece of missing information is the throw.

Because of the projector's angle, for every 30 inches of throw you drop 6 inches vertically. (Your angle is 11.31°, if you care) Using that ratio, you just multiply by the distance to the center of the screen and add your 12.5" offset to get the total distance from the ceiling. Thus:
screen center to ceiling = 12.5 + (6/30 or .2)*throw

To get your 30-36 inches, you work backward:
30-12.5=17.5, 17.5/.2=87.5" throw
36-12.5=23.5, 17.5/.2=117.5" throw

Edit: Sorry, missed the throw. Supra's right. Bloody cross-posting.

Thanks for all the help. Now, I know how big to make my out box.