Question about collimated display systems.

[geneb]

I've been thinking about this nasty problem for the last three weeks. So much so that I didn't do a thing with it today - I gave my poor IBM 5160 some quality time instead. *laughs*

First, you need one of these...



...but that's not all.

I'm going to try to get a frame that will fit into the one shown above to retain a solid skin - hopefully I'll get to it tomorrow.

One thing I noticed about the video from How It's Made - the mylar _crawls_. I've only seen that when a material is being drawn against a solid surface. I strongly suspect there's either a solid skin with a Metric Buttload(tm) of tiny holes, or there's a gas permeable solid like MDF there. Fortunately, I've got me a little gadget that's perfect for drilling holes in Metric Buttload quantities.

I should note that the frame in the picture above is a 60 degree wide slice of a 48" radius circle. It's 40 degrees high. The top is at zero degrees. This is a good size for a practical test. It also means that if it works, I only have to build two more to get 180 degrees.

g.

[castle]

That is one fine pic of one fine piece of work and craftmanship. Yes, drawing the mylar against a solid surface is the way to go. Would be most interested on how you construct the surface and the tolerances you are working with. I guessing that is plywood or some other type of non permeable material.

Hers is a suggestion on "attaching" the mylar.

Rather than trying to pre-measure the material and attaching it, first construct your frame and surface and the vacuum system. get some sort of "referee" material, cut it into sections, turn on the vacuum, and slap the strips in place. Cut an oversized piece of mylar that you know will extend beyond the edges of the frame. Roughly position the mylar against the "referee" material. Once the mylar is sort of in position, remove a section of the "referee" material by sliding it out from under the mylar. Hopefully, the mylar will be drawn against the surface. Continue until all the strips are removed.

If that works and the mylar is in position, simply mark the attach points on the mylar or maintain the vacuum and secure the mylar to the frame, shut down the vacuum and trim as required.

Warning, I've NOT tried this myself. Just a crazy idea.

JW

[mikesblack]

Great work! Curious about R. I was considering 6 feet and 30 degrees vertical but if there isn,t a disadvantage going to 5 or less feet, it would make for moe space in an already crammed room. Do you have any ideas on this?

[mikesblack]

Thanks castle

Can you explain "referee material"? Not quite sure I understand exactly what you have in mind.

Thanks.

[geneb]

Great work! Curious about R. I was considering 6 feet and 30 degrees vertical but if there isn,t a disadvantage going to 5 or less feet, it would make for moe space in an already crammed room. Do you have any ideas on this?

Mikesblack, you realize a 6 foot radius will give you an edge-to-edge width of 12 feet, right? The radius of the screen is going to be dictated by the size of the simulator cab. I picked 48" because I can use it with a couple of different cockpits - IF it works. Making even a "good enough" thin film mirror is a brass plated nightmare.

BTW - wledzian, I've got the projectors set up and running, so if you want to stop by and see it in action, let me know. I'm going to be taking it down at some point in order to move it, so let me know as soon as you can.

Here's what my next step looks like:


The gray colored components need to be cut out, but with any luck I'll be able to do that tomorrow.

g.

[castle]

Referee material --- anything that would block the holes and create a suction and substitute for the mylar. wrapping paper, aluminum foil, 8x11 paper sheets, etc.

Would also be a way to test your vacuum system and seals by blocking air flow through the pin holes and use smoke to see if air is being sucked in from other spots on the frame or joints.

JW

[geneb]

"Reference" material maybe?

g.

[mikesblack]

Thanks for explaining. I understand what you mean. Makes good sense.

On a separate note, I would love to find some plans or blueprints of these level D C. display systems. That would take out much of the guesswork.

I wonder how helpful the manufacturers would be if someone called over to explain that he or she was a hobbyist, looking for some helpful ideas or information. I wonder if the response would be guarded. Perhaps a manufacturer would be resistant to help someone if they thought by sharing could compromise their competitive advantage.

I have found Mike P. work and links to be a great help, so thank you Mike. I look forward to your new book. I have been reading your second book of late. Very interesting indeed. I'm sure I'll continue to check out your site for updates on this.

I will be happy to share what I find as I gather more information and look forward to exchanging ideas on this. Given that this seems like uncharted waters for the general DIY guy or gal, makes it even more intriguing.

[mikesblack]

geneb,
My pit is 11.5 ft across at the floor and at the back. I have roughly 2 ft from side of pit to my wall, perhaps a little less on the other side. I am considering that my radius origin is located at the throttles in the center of the cockpit. The widest part of the circle and where I am measuring R is at the top of the Mylar screen, where the angle relative to the floor is 90 degrees.

I'm considering the following.

Angle of arc from bottom to top of screen. Whatever I can do in order to keep the Mylar material wrinkle free. Width based on the arc based on 30 degrees and r= 6 feet is approx. 3 feet assuming my math is correct. ( 2Pi R) = approx. 36 ft diameter. So At 10 degrees of arc( 36/36) = 1 foot. I need to be sure that when I look out of the cockpit window I have enough viewing surface above and below cockpit window so there isn't an interruption to the image. If I bring these elements into consideration perhaps I might get away with 3 feet viewing surface. I need to experiment with curves of various radii and arc to see what will work.

[castle]

Just in case you've not found this site and want more info on concave mirrors and optics..

http://www.physicsclassroom.com/class/refln/u13l3d.cfm

Your instincts are probably correct, no manufacturer is going to supply details, trade secrets, and proprietary data to a voice on the phone no matter how sincere, honest, and trustworthy the caller may be. Afraid we're on our own here. OTOH there are some very bright, intelligent, and creative folks in the hobby side of simming as well as those on these forums.

Plus we're not going for FAA Level D certification. Close enough works for me