Question about collimated display systems.

[geneb]

[QUOTE=wledzian;111483
@geneb -
If it does come to that, I'd be more than willing to share the cost with you. It's looking like a screen for a 48" mirror could be formed from a single 4x8 sheet of plexi.[/QUOTE]

Building an oven to evenly heat a 4x8 sheet of material isn't an insurmountable challenge, but could certainly be an expensive one. I think we'd be better off building a three segment screen and have the projector seams align along the screen seams. I'm game either way, but if we're going to build an oven & vacu-forming table to that scale, we'd better come up with a use for it after we pull a pair of 24" radius screens off of it. *laughs*

(Now if I was an Evil Scientist type[*], I'd be tempted to see how well you can vacu-form people...Muahahaha!)
[*]Oh who the **** am I kidding? Who wants to volunteer? *Evil Laugh*

g.

(mumbles unpleasant things about nanny-ware)

[castle]

@wledzian

Ahhh! the fog is slowy lifting...

Since discussions seem to indicate that the projection screen is not a uniform sphere might it be easier to use a front projection system. Redifun builds a front projection system and that eliminates the problem of projector seams.

Makes the setup a bit more complex but doable.

JW

[ANDYSMITH]

@geneb I think there still is a person at Thun Field that vacforms plexi airplane canopies. He has an oven big enough to walk in and the vacuum systems too. He is next to the prop shop and behind Atkins Rotary.

Andy Smith

[crashdog]

I just got a reply from a professional visual system manufacurer. They told me that "low-cost" systems start at around half a million u.s. $'s. So sure is no option for a hobbyist But at least now we know.

Gery

[geneb]

That's good to know Andy. When we get to that point I'll have to find out how much he'd rent time on it. I certainly wouldn't need him to build the form.

Gery, "low cost" and "collimated display" is like "military intellegence". It's an oxymoron of the most extreme kind.

Having said that, keep in mind that with a hobby system, perfection is the enemy of good enough.

g.

[mikesblack]

Hi wledzian,

The 5 foot 6 inch curved base may be too short in order to allow for adjustment. I may need to expand that by a few inches. I am using aluminum tracks to allow for front to back and up and down travel.
Eyes are 46 inches from the floor. More pictures and measurements to come.



Mike

[mikesblack]

I think I'm going to move my bed to another location. If I have a chance of doing this correctly, I will most likely need to build the mirror without the restriction of needing regular passage.

Check out my latest photos.. The captains front window has a green mark and a string cross between the vertical and horizontal point of view. From that point to the wall measures 48". The height of my eyes is 45-46".

The upper edge of the side window is 53"and 31" for the lower edge. The angle of these windows is measured at 65deg.

I am not sure what I need to do to make sure the lower edge of the image from the mirror clears the side windows and fuselage while looking from inside the cockpit. Any ideas that you think I might consider?

Thanks again.

[castle]

Hmm, Mike's question on clearances got me thinking.

Have DoubleCAD installed, but not ready to delve in, so got out my trusty old drafting set.

Starting with a 6 foot radius set the eye point down 3 feet and in 6 inches, think I got a workable solution for a FOV of +25 and -20 except

1) the top edge of the screen is 20 degrees below the equator
2) the lower edge is 60 degrees down
3) which provides 40 degrees of mirror to view or a width of ~ 50 inches for the mylar
4) the approximate radius of the projection screen is 4 feet

but the radius of the lower edge of the mirrot is 6*cos(60) = 3 feet which is inside the cabin

Going to have to go back and reread Mike's tutorial in msg #78

@mikesblack
you might consider a projection screen that overhangs the top of the cabin and build a mirror accordindly

[wledzian]

@mikesblack
Is your cockpit a to-scale representation of a 767? It looks to me like 5'6" doesn't fit.
I've got the sketchup model, I can trace the eyelines to locate the bottom edge of the mirror. So far, the best I've been able to match castle's geometry puts the eyepoint about 5" off-center from the mirror axis; the 767 eyepiont is at least 21" offset.

I'd like to give a more encouraging response, but I need to rebuild the geometry and play with it a bit, I won't be able to give it any real attention until Saturday evening, I'll let you know what I come up with.

[mikesblack]

I believe my cockpit is close to scale, but I'm sure there is quite some error considering that angles used have been created using multiple photos and not from plans. So while I believe there is error, and also a degree of asymmetry, I wouldn't think there was a significant difference. I'll elaborate a little and ask some questions to follow, so to make sure we both understand and are discussing the same things.

Can you explain what you mean by the "eyepoint offset" from the mirror axis? My understanding as of now is that the mirror axis is the center of the mirror sphere, situated in the center of the cockpit, located adjacent to the pilots' eyes, and set at 90 degrees to the cockpit floor. With this assumption, the Captains eyes are 1' 6" from this point.

The 5 foot 6 inch circle that I cut was based on what could fit just below the lowest edge of the cockpit windows, so that it would miss intersecting the rear windows. Other than that, it is an arbitrary figure. As it is now, this ring just fits as intended, but I believe in order to get more adjustability, up/ down or back and forth, I will extend this radius.

If there is any measurement, you need that I have omitted, please let me know and I'll let you know.

Thank you very much again for your expertise and your time helping me solve this. Please do take your time and convenience. Again, I must say I am greatly appreciative.

Thank you too Castle for your help and input.

By the way, moved my bed, so have tons more room forward of the cockpit, but still have to deal with those side walls. My wife has been great allowing me to do this, but I doubt she would be so if I suggested, tearing down these walls.